Search

Land surface albedo constitutes a critical climatic variable, since it largely controls the actual amount of solar energy available to the Earth system. The purpose of this paper is to establish a theory for the exploitation of space observations to solve the atmosphere/surface radiation transfer problem on an operational basis and to generate surface albedo, aerosol load, and possibly land cover change products. Surface albedo is rather variable in space and time and depends both on the structure and on the radiative characteristics of the surface, as well as on the angular and spectral distribution of radiation at the bottom of the atmosphere. Weather and climate models often use preset distributions or simple parameterizations of this environment variable, even though such approaches do not accurately account for the actual effect of the underlying surface. From a mathematical point of view, the determination of the surface albedo corresponds to the estimation of a boundary condition for the radiation transfer problem in the coupled surface-atmosphere system. A relatively large database of 10 years or more of Meteosat data has been accumulated by EUMETSAT. These data, collected at half-hour intervals over the entire Earth disk visible from longitude 0°, constitute a unique resource to describe the anisotropy of the coupled surface-atmosphere system and provide the opportunity to document changes in surface albedo which may have occurred in these regions over that period. In addition, since the coupled surface-atmosphere radiation transfer problem must be solved, the proposed procedure also yields an estimate of the spatial and temporal distribution of aerosols. The proposed inversion procedure yields a characterization of surface radiative properties that may also be used to document and monitor land surface dynamics over the portion of the globe observed by Meteosat. Results from preliminary applications and an error budget analysis are discussed in a companion paper [Pinty et al., this issue].

This paper analyzes data obtained on July 3 and 18, 1995, during the summer 1995 Southern Oxidant Study (SOS) field campaign. In a previous paper (Nunnermacker et al., 1998) we analyzed measurements of key species that contribute to formation of O3 in the Nashville urban plume and presented a semiquantitative picture of O3 production in the plume from the point of emission to locations where no net O3 was being formed. In this paper we use a box model constrained by observed concentrations of stable species to obtain a detailed mechanistic description of the instantaneous processing of urban emissions at various times in the chemical evolution of the urban plume. Instantaneous ozone production rates and efficiencies with respect to NOx and to primary radical production are examined. At high NOx concentrations in the fresh urban plume the O3 production rate was found to be directly proportional to the hydrocarbon to NOx reactivity ratio. At lower NOx concentrations, corresponding to the mature urban plume and the background atmosphere, the O3 production rate was found to be directly proportional to the NOx concentration and independent of the hydrocarbon reactivity. NOx was found to be most efficiently used for ozone production at low NOx concentrations. In contrast, the efficiency with which the system uses primary radicals was found to be very low at low NOx concentrations and to peak at a NOx concentration of approximately 4 ppbv. A sensitivity study of the instantaneous O3 production rates to changes in NOx or hydrocarbon concentrations showed that the instantaneous 03 production rate at the center of the urban plume, when half of the urban NOx emissions had been processed, is hydrocarbon sensitive. However, 03 production becomes NOx sensitive as the plume matures.

The Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) experiment aboard the Shuttle Pallet Satellite (SPAS) was successfully flown in early November 1994 (STS 66) and in August 1997 (STS 85). This paper focuses on the first flight of the instrument, which was part of the Atmospheric Laboratory for Application and Science 3 (ATLAS 3) mission of NASA. During a free flying period of 7 days, limb scan measurements of atmospheric infrared emissions were performed in the 4 to 71 μm wavelength region. For improved horizontal resolution, three telescopes (viewing directions) were used that sensed the atmosphere simultaneously. Atmospheric pressures, temperatures, and volume mixing ratios of various trace gases were retrieved from the radiance data by using a fast onion-peeling retrieval technique. This paper gives an overview of the data system including the raw data processing and the temperature and trace gas profile retrieval. Examples of version 1 limb radiance data (level 1 product) and version 1 mixing ratios (level 2 product) of ozone, ClONO 2 , and CFC-11 are given. A number of important atmospheric transport processes can already be identified in the level 1 limb radiance data. Radiance data of the lower stratosphere (18 km) indicate strong upwelling in some equatorial regions, centered around the Amazon, Congo, and Indonesia. Respective data at the date line are consistent with convection patterns associated with El Nino. Very low CFC-11 mixing ratios occur inside the South Polar vortex and cause low radiance values in a spectral region sensitive to CFC-11 emissions. These low values are a result of considerable downward transport of CFC-11 poor air that occurred during the winter months. Limb radiance profiles and retrieved mixing ratio profiles of CFC-11 indicate downward transport over ∼5 km. The accuracy of the retrieved version 1 mixing ratios is rather different for the various trace gases. In the middle atmosphere the estimated systematic error of ozone is ∼14%. Ozone data of correlative satellite measurements are well within this error bar. CRISTA agrees, for example, with Atmospheric Trace Molecule Spectroscopy Experiment (ATMOS) sunset measurements typically within 5%. The random error of version 1 ozone mixing ratios is 4%. Similar values apply to other trace gases. These low random errors allow the identification of small and medium scale horizontal and vertical structures in the measured trace gas distributions. Examples of structures in mixing ratio fields of ozone, ClONO 2 , and CFC-11 are given.

This is the second in a series of two papers on thermal inertia estimation from satellite data. In this paper we present the methodology that permits thermal inertia mapping using NOAA-advanced very high resolution radiometer data from the four temperatures algorithm developed in the first paper. Four NOAA images are used to assess thermal inertia: an image at 14:30 (nominal hour) is used to estimate the surface albedo; others at 2:30 and 14:30 are used to estimate the diurnal surface temperature range, while images at 7:30, 14:30, and 19:30 are used to assess the phase difference. The main advantage of the methodology is that the phase difference is obtained from satellite data without the need to know the value of the effective surface emissivity and total water vapor content of the atmosphere. Following the proposed algorithm and the developed methodology, maps of thermal inertia are presented, two for the Iberian Peninsula (on two consecutive days to check consistency of the results) and one for Morocco (to check behavior in different landscapes). The thermal inertia values obtained are consistent with the known properties of these zones.

Tentative estimates, using three-dimensional chemistry and transport models, have suggested small ozone increases in the upper troposphere resulting from current aircraft emissions, but have also concluded to significant deficiencies in today's models and to the need to improve them through comparison with extended data sets. The Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program was initiated in 1993 by European scientists, aircraft manufacturers, and airlines to collect experimental data. Its goal is to help understand the atmosphere and how it is changing under the influence of human activity, with particular interest in the effects of aircraft. MOZAIC consists of automatic and regular measurements of ozone and water vapor by five long range passenger airliners flying all over the world. The aim is not to detect direct effects of aircraft emissions on the ozone budget inside the air traffic corridors but to build a large database of measurements to allow studies of chemical and physical processes in the atmosphere, and hence to validate global chemistry transport models. MOZAIC data provide, in particular, detailed ozone and water vapor climatologies at 9–12 km where subsonic aircraft emit most of their exhaust and which is a very critical domain (e.g., radiatively and stratosphere/troposphere exchanges) still imperfectly described in existing models. This will be valuable to improve knowledge about the processes occuring in the upper troposphere and the lowermost stratosphere, and the model treatment of near tropopause chemistry and transport. During MOZAIC I (January 1993–September 1996), fully automatic devices were developed, installed aboard five commercial Airbus A340s, and flown in normal airline service. A second phase, MOZAIC II, started in October 1996 with the aim of continuing the O3 and H2O measurements and doing a feasibility study of new airborne devices (CO, NOy). Between September 1994 and December 1997, 7500 flights, representing 54,000 flight hours, were made over the continents (Europe, North America, Asia, South America, and Africa) and the Atlantic Ocean. Most of the measurements (90%) correspond to cruise altitudes (9–12 km), the remaining being obtained during ascents and descents near the 50 cities frequented by MOZAIC operations. This paper reports the main characteristics of the program and the flights, with a brief summary of the general content and focus of papers already published and companion papers of this special issue. These deal with the following: description and validation of the ozone and water vapor measurement methods; presentation of an accurate ozone climatology at 9–12 km altitude, over the Northern Hemisphere (130°W–140°E; 0°–80°N), and down to 30°S over South America and Africa; comparison between a 2-year MOZAIC ozone climatology (1994–1996; 0–12 km) and a long series of older measurements made since the 1980s at 8 stations of the Ozone Sounding Network; study of ozone-rich transients, up to 500 ppbv on a horizontal scale of 5–80 km, in the upper tropical troposphere; and comparison between MOZAIC ozone data and output from the global chemistry and transport model (CTM) TOMCAT.

Data assimilation is a vital technique in modern meteorology, allowing information from a wide range of observations to be combined to produce synoptic analyses of the atmospheric circulation. Data assimilation has a number of advantages over conventional analysis methods that stem from the use of a numerical model of the atmosphere as an integral part of the technique. The model provides a framework which allows information from observations to be combined with our understanding of the atmosphere, as embodied in the model, so that a consistent, evolving, three-dimensional picture of the atmospheric circulation may be constructed. The aim of this paper is to compare results from two different stratospheric data assimilation systems (from Goddard Space Flight Center and the U.K. Meteorological Office) to assess the reliability of analyses derived by using assimilation techniques. In particular, this paper concentrates on assessing the quality of the analyses for long-term transport studies. First, the zonal mean circulations are compared, with emphasis on the consistency of the residual circulation. Second, horizontal transport processes are compared, with particular emphasis on the representation of features in the neighborhood of the wintertime polar vortex. It is shown that the two analyses give a broadly consistent picture of the atmospheric circulation. Where differences are identified, they can often be attributed to particular shortcomings in one of the assimilation systems. The results presented here stress the usefulness of data assimilation for stratospheric studies.

This paper presents the description of the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) rain rate database and its different spatial and temporal variability characteristics. Accuracy and reliability of this database are evaluated with the position of the appropriateness of its use for the practical (ground truth, beam filling error for the Tropical Rainfall Measuring Mission) and theoretical (spectral estimation) problems. The following is shown in this paper: the concentration of a significant power in the origin of the frequency axis in the temporal spectra; the existence of a diurnal cycle (which has a range of variation of about 1.43 to 2.03 mm/h); the distinction between the north-south and east-west transport of rain, reflected in the two-dimensional spectrum and correlation function of the spatial field, and character of its anisotropy; the scales of the differences between the corresponding estimates of the TOGA and Global Atmospheric Research Program (GARP) Atlantic Tropical Experiment (GATE) data. The documentation of the TOGA COARE database is given. Methodology and software (in IDL and Fortran languages) for management of the TOGA COARE database system and for estimating of different variability statistics were developed. The results obtained can be used for choosing any subset appropriate for the particular rain analysis study, for rain modeling, for comparison with corresponding estimates of other sources of data (satellite or simulated by physical models), and for solving some other scientific and engineering problems connected with rain measurements and modeling.

An extensive study of tropospheric photochemical trace species, including the hydroxyl radical OH was conducted in the Colorado Rocky Mountains from early August to early October 1993. Many of the parameters that influence the abundance of OH in the atmosphere, including j(O3 and NO2), formaldehyde, nonmethane hydrocarbons, NOx, ozone, H2O, aerosols, and others, were measured simultaneously with OH. Instrumentation for measurement of OH included a long-path spectroscopic technique and several in situ techniques: ion-assisted mass spectrometry, laser-induced resonance fluorescence, and a liquid scrubber/liquid chromatographic method. Instrument comparisons between long-path and in situ measurements were conducted for OH, O3, CH2O, NO2, and H2O, and these measurements provide a valuable insight into the chemistry of the region. The complete data set provided a robust set of inputs to a zero-dimensional model for exploring OH photochemistry. Independently measured OH concentrations were in agreement within one standard error much of the time, thus giving confidence that hydroxyl is being measured correctly. OH concentrations were typically low during clean continental airflow with concentrations rarely above 4×106 cm−3. During occasions of polluted airflow from the Denver-Boulder metropolitan areas, values of OH rose as high as 1.2×107 cm−3. The nearly complete suite of trace gases measured simultaneously with the hydroxyl radical severely constrained the models and provided numerous opportunities to compare relations between species (e.g. OH versus NOx, OH/HO2, RO2 versus NOx). Modeled hydroxyl results using the complete species suite were about a factor of 1.5 higher than measured OH concentrations suggesting that the photochemistry may not be well understood. The campaign data provide new insights into the chemistry of the lower troposphere. This paper provides an overview of the campaign and brief descriptions of results from individual experiments. Details are provided in the accompanying papers in this issue.

During the period 1988-1990, studies of atmospheric aerosol have been made over the Atlantic. These include measurement programs out of Ascension Island (8{degrees}S, 14{degrees}W), the Azores (38{degrees}N, 25{degrees}W), Iceland (63{degrees}N, 23{degrees}W), and from the United Kingdom over the Northeast Atlantic. For these studies the equipment deployed included an airborne backscatter lidar (operating at 10.6 {mu}m), airborne particle-sounding probes, ground-based lidars (operating at 10.6, 0.53, and 0.35 {mu}m), balloon radiosondes, and a Sun-tracking photometer. In addition, standard meteorological information has been incorporated along with, when appropriate, data from the SAGE II limb-sounding satellite. The present paper thus introduces an overview of the program together with an outline of the technology, measurement characteristics, and performance of the airborne equipment that determined the strategic planning of much of the work. The measurements themselves, made in the relatively clean period for the atmosphere before the Mount Pinatubo eruption, will be presented in a subsequent series of papers. 26 refs., 5 figs., 3 tabs.

Small particles in the atmosphere, called "atmospheric aerosol" have a direct effect on Earth climate through scattering and absorbing sunlight, and also an indirect effect by changing the properties of clouds, as they interact with solar radiation as well. Aerosol typically stays in the atmosphere for several days, and can be transported long distances, affecting air quality, visibility, and human health not only near the source, but also far downwind. Smoke from vegetation fires is one of the main sources of atmospheric aerosol; other sources include anthropogenic pollution, dust, and sea salt. Chemistry transport models (CTMs) are among the major tools for studying the atmospheric and climate effects of aerosol. Due to the considerable variation of aerosol concentrations and properties on many temporal and spatial scales, and the complexity of the processes involved, the uncertainties in aerosol effects on climate are large, as is featured in the latest report of Intergovernmental Panel on Climate Change (IPCC) in 2007. Reducing this uncertainty in the models is very important both for predicting future climate scenarios and for regional air quality forecasting and mitigation. During vegetation fires, also called biomass burning (BB) events, complex mixture of gases and particles is emitted. The amount of BB emissions is usually estimated taking into account the intensity and size of the fire and the properties of burning vegetation. These estimates are input into CTMs to simulate BB aerosol. Unfortunately, due to large variability of fire and vegetation properties, the quantity of BB emissions is very difficult to estimate and BB emission inventories provide numbers that can differ by up to the order of magnitude in some regions. Larger uncertainties in data input make uncertainties in model output larger as well. A powerful way to narrow the range of possible model estimates is to compare model output to observations. We use satellite observations of aerosol properties, specifically aerosol optical depth, which is directly proportional to the amount of aerosol in the atmosphere, and compare it to the model output. Assuming the model represents aerosol transport and particle properties correctly, the amount of BB emissions determines the simulated aerosol optical depth. In this study, we explore the regional performance of 13 commonly used emission estimates. These are each input to global Goddard Chemistry Aerosol Radiation and Transport (GOCART) model. We then evaluate how well each emission estimate reproduces the smoke aerosol optical depth measured by the MODIS instrument. We compared GOCART-simulate aerosol optical depth with that measured from the satellite for 124 fire cases around the world during 2006 and 2007. We summarize the regional performance of each emission inventory and discuss reasons for their differences by considering the assumptions made during their development. We also show that because stronger wind disperses smoke plumes more readily, in cases with stronger wind, a larger increase in emission amount is needed to increase aerosol optical depth. In quiet, low-wind-speed environments, BB emissions produce a more significant increase in aerosol optical depth, other things being equal. Using the region-specific, quantitative relationships derived in our paper, together with the wind speed obtained from another source for a given fire case, we can constrain the amount of emission required in the model to reproduce the observations. The results of this paper are useful to the developers of BB emission inventories, as they show the strengths and weaknesses of individual emission inventories in different regions of the globe, and also for modelers who use these inventories and wish to improve their model results.

[1] In this paper, the potential of a multifrequency submillimeter radiometer to characterize ash plumes in the near-field of a volcanic eruption is evaluated. The radiometer's sensitivity to mass concentration and particle effective dimension is shown to depend most critically on aerosol altitude and ejected water vapor concentration. There is also some dependence on temperature, aerosol shape and complex refractive index. For this study, the volcanic aerosols are assumed to be randomly oriented solid hexagonal silicates of aspect ratio unity. The T-matrix method is used to calculate the single-scattering properties of the aerosols at 36 frequencies between 90 GHz and 880 GHz, and the aerosol bulk scattering properties are derived assuming lognormal size distribution functions. A midlatitude standard summer atmosphere and a perturbed midlatitude summer atmosphere are used to quantify the sensitivity, using the delta-Eddington two-stream approximation, of the radiometer to the presence of aerosol. It is shown that at 34 frequencies, between 113 GHz and 880 GHz, the sensitivity to aerosol is a maximum if the following four conditions are satisfied: (i) The altitude of the aerosol layer should be ≫ 3 km, (ii) 0.1 g m−3 < mass concentration < 30 g m−3 (iii) the aerosol effective dimension, De, 20 μm < De < 1000 μm and (iv) water vapor ejected by a volcano into the atmosphere should be < 1000 times greater than the background water vapor concentration. The paper demonstrates the potential usefulness of using spectrally resolved submillimeter measurements in the near-field of volcanic eruptions to characterize plume properties.

Aerosols are tiny suspended particles in the atmosphere that scatter and absorb sunlight. Smoke particles are aerosols, as are sea salt, particulate pollution and airborne dust. When you look down at the earth from space sometimes you can see vast palls of whitish smoke or brownish dust being transported by winds. The reason that you can see these aerosols is because they are reflecting incoming sunlight back to the view in space. The reason for the difference in color between the different types of aerosol is that the particles arc also absorbing sunlight at different wavelengths. Dust appears brownish or reddish because it absorbs light in the blue wavelengths and scatters more reddish light to space, Knowing how much light is scattered versus how much is absorbed, and knowin~ that as a function of wavelength is essential to being able to quantify the role aerosols play in the energy balance of the earth and in climate change. It is not easy measuring the absorption properties of aerosols when they are suspended in the atmosphere. People have been doing this one substance at a time in the laboratory, but substances mix when they are in the atmosphere and the net absorption effect of all the particles in a column of air is a goal of remote sensing that has not yet been completely successful. In this paper we use a technique based on observing the point at which aerosols change from brightening the surface beneath to darkening it. If aerosols brighten a surface. they must scatter more light to space. If they darken the surface. they must be absorbing more. That cross over point is called the critical reflectance and in this paper we show that critical reflectance is a monotonic function of the intrinsic absorption properties of the particles. This parameter we call the single scattering albedo. We apply the technique to MODIS imagery over the Sahara and Sahel regions to retrieve the single scattering albedo in seven wavelengths, compare these retrievals to ground-based retrievals from AERONET instruments and compute error bars on each retrieval. The results show that we can retrieve single scattering albedo for pure dust to within +/-0.02 and mixtures of dust and smoke to within +/-0.03. No other space based instrument has achieved a retrieval of single scattering albedo that spans the spectrum from 0.47 microns to 2.13 microns and produces regional maps of aerosol absorption showing gradients and changes. Applied in a more operational fashion, such information will narrow uncertainties in estimating aerosol forcing on climate.

[1] In comparison to the lower atmosphere where comprehensive global atmospheric specifications are commonplace, the ability to perform routine global measurements of the properties of the atmosphere above the stratopause continues to be an active area of scientific research. In this paper, we revisit the use of infrasound as a remote sensing technique for horizontal winds in the upper atmosphere. To use infrasound to monitor the winds in the upper atmosphere, a sufficiently strong and persistent infrasound source is required. In addition, because of the highly attenuating nature of the thermosphere, the signals used must have low enough frequency content to survive. In this paper, impulsive signals from the Tungurahua volcano in Ecuador are used. This volcano has gone through periods of intense activity during which impulsive signals of dominant periods between 3 and 5 s are emitted. Depending on the atmospheric conditions, stratospheric, mesospheric, and thermospheric arrivals are observed. It is found that the traveltimes of the thermospheric arrivals exhibit a coherent variability with periods equal to those of the tidal harmonics. As such, these observations suggest a means of passive atmospheric remote sensing that can be utilized in conjunction with other techniques to routinely measure the state of the upper atmosphere.

This paper describes calculations of the spatial and temporal variation of the radiation budget of a tropical mesoscale convective system (MCS). A combination of cloud model simulations, radiation model simulations, and analyses of observations obtained during the Equatorial Mesoscale Experiment (EMEX), the Stratosphere-Troposphere Exchange Program (STEP), and the Australian Monsoon Experiment (AMEX) are used to obtain these heating rates. The two-dimensional version of the Colorado State University regional atmospheric modeling system is used to simulate a tropical MCS that occurred during EMEX mission 9 on February 2, 1987. The simulation is shown to broadly agree with the observations reported in a related paper. The spatial radiative heating distributions derived from a two-stream radiative transfer model corresponding to the mature stage of the simulated cloud system indicate that significant horizontal inhomogeneities exist. According to the model results the effects of the MCS are to (1) increase in the infrared emission to the surface and to decrease in the net infrared energy loss from the atmosphere relative to the clear sky emission and (2) change the transmission of solar flux to the surface, the shortwave albedo of the atmosphere, and the solar absorption in the atmosphere. The results show how the MCS significantly reduces the solar flux to the surface relative to the clear sky values and that the largest reduction occurs under the convective portions of the mature MCS. (3) The MCS creates a total (solar plus infrared) radiative warming in the atmosphere relative to the surrounding clear sky. The value of this total heating is governed by both infrared and solar absorption. Vertical profiles of this heating show the dominance of infrared cooling near cloud top and infrared heating inside and near cloud base. The shortwave heating rate can also be as large as the infrared cooling near the cloud top region of the tropical MCS, especially at a local noon. (4) The temporal changes in radiation profiles also demonstrate how the MCS modulates the radiation budget of the atmosphere. Specifically, the total radiation energy loss of the entire two-dimensional domain of the model atmosphere decreases and eventually becomes positive as the cloud system decays, becomes a stratiform in nature, and fills the domain. This change in the column divergence of flux translates into a total column radiative heating rate of approximately 1.7 K/d (relative to the clear sky radiative cooling rate). The solar component of this domain heating tends to be concentrated in the upper troposphere, whereas the infrared component of the heating is spread over the lower and middle troposphere. These results also show how tropical mesoscale cloud system provides an effective radiative heat source for the tropical atmosphere.

[1] The radiation budget in the Earth-atmosphere system is what drives Earth's climate, and thus measurements of this balance are needed to improve our knowledge of Earth's climate and climate change. In the present paper we focus on the analysis of the surface shortwave radiation budget (SSRB), which is the amount of energy in the solar region of the electromagnetic spectrum (0.2–4.0 μm) absorbed at the surface. The SSRB has to be modeled from the surface to the top of the atmosphere, jointly with information about the state of the atmosphere and the surface. These data come from satellites orbiting the Earth and are often missing or disturbed. Its interest is not only at global scales; rather, regional, high-spatial-resolution description is also of interest as an indicator of changes and because of its relationship to aridification from well-developed vegetation. The goal of this paper is to estimate and predict the spatiotemporal evolution of SSRB data at a regional scale in eastern Spain. Two different spatiotemporal models with covariates are considered: one is based on modeling the spatiotemporal semivariogram and the other uses the Kalman filter technique for spatiotemporal prediction. We present comparisons between these two models with respect to the simpler, purely spatial model. The results show that there is not a great benefit to use the more complicated models, although there is a marginal improvement with complexity.

[1] Vertical profiles of water vapor concentration at high latitudes (57-72 degreesN; 64-89 degreesS) were observed by the Improved Limb Atmospheric Spectrometer (ILAS) solar occultation sensor aboard the Advanced Earth Observing Satellite (ADEOS). These measurements were made continuously from November 1996 through June 1997 with some additional periods in September to October 1996. A validation study of the water vapor data processed with the version 5.20 ILAS retrieval algorithm is presented in this paper. Uncertainty and general characteristics of the ILAS water vapor measurements are briefly reviewed. Comparisons are made with data obtained by (1) the ILAS validation balloon campaigns at Kiruna, Sweden and at Fairbanks, Alaska; (2) the aircraft measurements under the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) campaign; and (3) available satellite measurements of the version 19 Halogen Occultation Experiment (HALOE) and the version 6 Stratospheric Aerosol and Gas Experiment II (SAGE II). The agreement between ILAS water vapor and all independent reliable correlative measurements in the altitude region of 15-60 km is better than 10% for the majority of cases and better than 20% for all comparisons, with the exception of some isolated cases detailed in this paper. Climatological comparisons of ILAS data with Upper Atmosphere Research Satellite (UARS) climatology and HALOE data show the overall consistency of ILAS water vapor data considering the known features of atmospheric circulation. The characteristics of ILAS measurements, i.e., high sampling frequency in polar latitudes with high vertical resolution along with the good data quality, make the ILAS water vapor data set valuable for various polar stratospheric research applications.

Changes in the concentration of greenhouse gases within the atmosphere lead to changes in radiative fluxes within the atmosphere and at its boundaries. This paper describes an experiment within the...

[1] In this paper, ozone (O3), water vapor (H2O), carbon monoxide (CO), and peroxide concentrations and photolysis rates measured in the troposphere over the North Atlantic during two Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) aircraft field campaigns are used to calculate the concentration of nitric oxide (NO) required for net photochemical O3 production (nPO3) to be positive (NOcomp). NOcomp tended to show a decrease with altitude, although it was sometimes found to be low in the marine boundary layer (MBL) where H2O concentrations were high and O3 concentrations were low. nPO3 was calculated for the spring when NO data were available and was found to be mostly negative and generally increased from about −0.5 to −0.2 ppbv hr−1 in the MBL to +0.04 ppbv hr−1 at about 7–8 km altitude. The results suggest that much of the lower and middle troposphere over the eastern North Atlantic during spring is in a state of slow net photochemical O3 destruction. However, in the upper troposphere, the system changes to one of net photochemical production, which results from the drier environment and higher NO concentrations. Furthermore, examples of net O3 production were also observed in the lower and middle troposphere associated with either in situ sources of NO or long-range transport of pollution. The paper also illustrates the sensitivity of this O3 production/loss state to H2O and NO concentrations, photolysis rates, and temperatures.

Satellites provide a global view of the structure in the fields that they measure. In the mesosphere and lower thermosphere, the dominant features in these fields at low zonal wave number are contained in the zonal mean, quasi-stationary planetary waves, and tide components. Due to the nature of the satellite sampling pattern, stationary, diurnal, and semidiurnal components are aliased and spectral methods are typically unable to separate the aliased waves over short time periods. This paper presents a data processing scheme that is able to recover the daily structure of these waves and the zonal mean state. The method is validated by using simulated data constructed from a mechanistic model, and then applied to Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature measurements. The migrating diurnal tide extracted from SABER temperatures for 2009 has a seasonal variability with peak amplitude (20 K at 95 km) in February and March and minimum amplitude (less than 5 K at 95 km) in early June and early December. Higher frequency variability includes a change in vertical structure and amplitude during the major stratospheric warming in January. The migrating semidiurnal tide extracted from SABER has variability on a monthly time scale during January through March, minimum amplitude in April, and largest steady amplitudes from May through September. Modeling experiments were performed that show that much of the variability on seasonal time scales in the migrating tides is due to changes in the mean flow structure and the superposition of the tidal responses to water vapor heating in the troposphere and ozone heating in the stratosphere and lower mesosphere.

Lake Taihu is the third largest freshwater lake in China and is situated in the Middle and lower Yangtze River delta. It is characterized by its shallowness (~1.9 m), large area (~2338 km2), and high turbidity in recent years. The lake's effect on local summer precipitation is first studied in this paper through the use of an atmosphere-lake coupled model. By enlarging the light extinction coefficient, modifying the radiation scheme, and setting the roughness length to constants, the coupled model after adjustment realistically reproduces the thermal stratification and magnitude of diurnal variation over Lake Taihu, with mean biases of 0.7°C for lake surface temperature and 0.4°C for near-surface air temperature, respectively. Based on this calibrated coupled model, two high-resolution numerical simulations with and without the lake (lake grid cells replaced by cropland) were conducted to identify the lake effects. The results show that an overall effect of Lake Taihu on local summer precipitation is negative during daytime and positive during nighttime and the precipitation pattern may be modified to some extent. The lake effect varies between areas and with time of day and occurs primarily on the downwind shore. A composite analysis for a representative decreased precipitation region reveals that during daytime in the summer, the combination of decreased air temperature and latent heat flux, along with intensified divergence and downdraft, acts together to stabilize the lower atmosphere and suppress thermal convective activities, ultimately resulting in less precipitation over this region.

The U.S. National Oceanic and Atmospheric Administration (NOAA) has operated a program to continuously monitor atmospheric CO2 at Cape Matatula, American Samoa, since January 1976. This paper describes the basic operational program and reports the data through 1987. Data sets are derived from hourly means which have been selected to represent baseline conditions. All hourly mean CO2 values (with flags indicating data selection status) are archived at NOAA's Geophysical Monitoring for Climatic Change (GMCC) laboratory in Boulder, Colorado; at the Carbon Dioxide Information and Analysis Center in Oak Ridge, Tennessee; and in the microfiche version of this paper. The record from the in situ analyzer is compared with that of flask samples obtained in various ways. The overall 12-year record shows an average increase of 1.44 parts per million by volume per year. This increase amounts to 61% of the carbon dioxide emitted into the atmosphere by fossil fuel combustion during this period. The record is also characterized by the lack of a prominent seasonal cycle. The CO2 concentrations for the first half of each year are always more variable than the second 6 months, when the wind flow is dominated by strong southeasterly trades. The interannual variability of the CO2 growth rate correlates very well with that observed at other GMCC sites.

We evaluate polar ozone depletion chemistry using the specified dynamics version of the Whole Atmosphere Community Climate Model for the year 2011. We find that total ozone depletion in both hemispheres is dependent on cold temperatures (below 192 K) and associated heterogeneous chemistry on polar stratospheric cloud particles. Reactions limited to warmer temperatures above 192 K, or on binary liquid aerosols, yield little modeled polar ozone depletion in either hemisphere. An imposed factor of three enhancement in stratospheric sulfate increases ozone loss by up to 20 Dobson unit (DU) in the Antarctic and 15 DU in the Arctic in this model. Such enhanced sulfate loads are similar to those observed following recent relatively small volcanic eruptions since 2005 and imply impacts on the search for polar ozone recovery. Ozone losses are strongly sensitive to temperature, with a test case cooler by 2 K producing as much as 30 DU additional ozone loss in the Antarctic and 40 DU in the Arctic. A new finding of this paper is the use of the temporal behavior and variability of ClONO2 and HCl as indicators of the efficacy of heterogeneous chemistry. Transport of ClONO2 from the southern subpolar regions near 55–65°S to higher latitudes near 65–75°S provides a flux of NOx from more sunlit latitudes to the edge of the vortex and is important for ozone loss in this model. Comparisons between modeled and observed total column and profile ozone perturbations, ClONO2 abundances, and the rate of change of HCl bolster confidence in these conclusions.

This paper investigates nonmigrating tides from the ground to the lower mesosphere using data from a high-resolution general circulation model (KANTO GCM), as well as observational data from the Sounding of the Atmosphere using Broadband Emission Radiometry instrument on board the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite and from GPS radio occultation measurements obtained with the COSMIC/FORMOSAT-3 mission. We extract nonmigrating tides using a composite as a function of universal time in physical space, without performing a zonal wave number decomposition. The KANTO GCM clearly demonstrates that tropical nonmigrating tides are regarded as gravity waves excited by diabatic heating enhanced over two major continents, specifically Africa and South America. They propagate zonally, in a direction away from their sources; that is, west and eastward propagating waves are dominant on the western and eastern sides of the continents, respectively. These characteristics are observed in two satellite data sets as well, except that the amplitudes in the KANTO GCM are larger than those in the observations. Seasonal variations of nonmigrating tides are also investigated. It is suggested that filtering owing to the stratopause semiannual oscillation, as well as diabatic heating in the troposphere, is important for the seasonal variations of nonmigrating tides in the stratosphere and the lower mesosphere.

NOAA, through the Joint Polar Satellite System (JPSS) program, in partnership with the National Aeronautical and Space Administration, launched the Suomi National Polar-orbiting Partnership (S-NPP) satellite, a risk reduction and data continuity mission, on 28 October 2011. The JPSS program is executing the S-NPP Calibration and Validation program to ensure that the data products comply with the requirements of the sponsoring agencies. The Ozone Mapping and Profiler Suite (OMPS) consists of two telescopes feeding three detectors measuring solar radiance scattered by the Earth's atmosphere directly and solar irradiance by using diffusers. The measurements are used to generate estimates of total column ozone and vertical ozone profiles for use in near-real-time applications and extension of ozone climate data records. The calibration and validation efforts are progressing well, and both Level 1 (Sensor Data Records) and Level 2 (Ozone Environmental Data Records) have advanced to release at Provisional Maturity. This paper provides information on the product performance over the first 22 months of the mission. The products are evaluated through the use of internal consistency analysis techniques and comparisons to other satellite instrument and ground-based products. The initial performance finds total ozone showing negative bias of 2 to 4% with respect to correlative products and ozone profiles often within ±5% in the middle and upper stratosphere of current operational products. Potential improvements in the measurements and algorithms are identified. These will be implemented in coming months to reduce the differences further.

Aerosols play a significant yet complex and central role in the Earth's radiation budget, and knowledge of long-term changes in the atmospheric turbidity induced by aerosols is therefore fundamental for a better understanding of climate change. However, there is little available information on changes in aerosol concentration in the atmosphere, especially prior to the 1980s. The present paper reviews publications reporting the suitability of sunshine duration records with regard to detecting changes in atmospheric aerosols. Some of the studies reviewed propose methods for estimating aerosol-related magnitudes, such as turbidity, from sunshine deficit at approximately sunrise and sunset, when the impact of aerosols on the solar beam is more easily observed. In addition, there is abundant evidence that one cause of the decadal changes observed in sunshine duration records involves variations in atmospheric aerosol loading. Possible directions for future research are also suggested: in particular, detailed studies of the burn (not only its length but also its width) registered by means of Campbell-Stokes sunshine recorders may provide a way of creating time series of atmospheric aerosol loading metrics dating back to over 120 years from the present.

Tides forced by large-scale weather systems in the tropical troposphere introduce significant longitudinal and local time variability in the upper atmosphere. This paper presents variability of tidal harmonics of the latent heating from 2002 to 2011 associated with the El Nino–Southern Oscillation (ENSO) and the tidal wind response in the mesosphere/lower thermosphere (MLT) region. Emphasis is on the strong ENSO cycle 2009–2011. Latent tidal heating rates are computed from TRMM satellite precipitation data, with added radiative heating from MERRA reanalysis, as functions of time, latitude, and altitude. The heating rates for the two most affected nonmigrating tides (DE3 and DE2) are examined and compared with MLT tidal wind variability from TIDI/TIMED. Principal component analysis (PCA) is used to identify the tidal modes most affected by ENSO. Our results indicate that the tidal response to ENSO is largest during winter for both of the tides, with the largest response occurring in the DE3 tidal winds during the La Nina phase, with an increase of roughly 70% for the winter months of 2010/2011, and negligible response during the El Nino phase. The ENSO effect in the tidal forcing closely resembles the first symmetric and antisymmetric Hough modes of DE3 and DE2, thus being an efficient mechanism to transmit the ENSO signal into the MLT tides.

This paper addresses the aerosol effects on radiation and the feedback on meteorology and photochemical activity, applying the online model RAMS/ICLAMS. The model treats meteorology and chemical pollutants on an interactive way. Cloud condensation nuclei (CCN), giant cloud condensation nuclei, and ice nuclei are treated as predictive quantities. The calculation of the aerosol optical properties accounts for size-resolved mineral dust and size- and humidity-dependent optical properties of sea salt. The simulations with and without aerosol impacts reveal the complex direct and indirect mechanisms through which the alteration of radiation fluxes influences meteorology and photochemical processes. For the specific dust event, the reduction in the surface shortwave radiation over cloudless regions affected by dust averages at ~ −75 W m−2 at 12:00 UTC per unit dust loading (1 g m−2). The increase on downwelling longwave radiation over the same areas and time averages at ~ 40 W m−2 per unit dust loading (1 g m−2). Surface upwelling longwave radiation over Mediterranean exhibits a complex daytime behavior. During midnight, the inclusion of dust leads to larger upwelling longwave radiation fluxes over the African continent. The net downward longwave radiation over cloudless areas exhibits an increase both during noon and midnight with the inclusion of dust. The results show that the vertical structure of the dust layer governs the magnitude of the feedback on radiation. The activation of natural particles as CCN causes small changes in radiation fluxes and temperature. Precipitation is influenced more by the indirect rather than the direct and semidirect effects.

[1] Two new diagnostic quantities called solenoidal vorticity (SV) and potential solenoidal vorticity (PSV) are defined in this paper for a moist atmosphere based on the generalized moist potential vorticity (GMPV). SV and PSV are introduced to incorporate vorticity information along the isentropic surfaces that GMPV (or PV) has lost. SV is the scalar product of vorticity and the moist solenoidal term ∇ p × ∇ α*, while PSV is the scalar product of vorticity and (∇ p × ∇ α*) × ∇ θ* (a new vector). Application of GMPV, SV, and PSV to a diagnostic study of a heavy rainfall case shows that SV reflects the coupling of vertical wind shear and the baroclinity of the moist atmosphere weighted by the vertical gradient of pressure, while PSV reflects the coupling of vertical wind shear and baroclinity, the static stability, and the vertical gradient of pressure. Although all three quantities exhibit strong signals over the observed precipitation region, SV and PSV are more capable of distinguishing between precipitation and non-precipitation areas. The following three main factors are concluded to contribute to the very different distribution patterns of GMPV, SV, and PSV: static stability,the vertical gradient of pressure, and different ways of coupling vertical wind shear and baroclinity. These factors are responsible for the good performance of SV and PSV in tracing and predicting heavy rainfall, as demonstrated by the correlation coefficient between SV (PSV) and the rainfall amount obtained from long time series analyses. The results of this study suggest that SV and PSV are good detectors of heavy rainfall and may be used as precipitation prediction parameters.

[1] We present a new approach to constrain and validate atomic oxygen (O) concentrations in the mesopause region (~ 80 to ~ 100 km). In a prior companion paper [Mlynczak et al., 2013], we presented O-atom concentrations in the mesopause region inferred from measurements of day ozone and night hydroxyl emission rates made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument. The approach presented here uses the constraint of global, annual mean energy balance to derive atomic oxygen concentrations, consistent with rates of radiative cooling by carbon dioxide (CO2) and solar heating due to molecular oxygen (O2). The mathematical difference between these cooling and heating rates, on a global annual mean basis, effectively constrains the maximum heating rate for the sum of all other processes. The remaining terms, solar heating due to ozone plus a series of exothermic chemical reactions can be expressed as functions of O. This new approach enables a simple mathematical expression that yields the vertical profile of global annual mean “radiatively constrained” atomic oxygen in the mesopause region. The radiatively constrained atomic oxygen depends only on the CO2 cooling rates, O2 solar heating rates, and standard reaction rate coefficients and enthalpies. Radiative cooling and solar heating rates used in these analyses are derived from measurements made by the SABER instrument on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite. There is excellent agreement between the SABER radiatively constrained atomic oxygen and that derived from the SABER ozone and OH emission measurements over most of the mesopause region. Radiatively constrained atomic oxygen represents an upper limit on the global average O-atom concentration in the mesopause region.

[1] Atomic oxygen (O) is a fundamental component in chemical aeronomy of Earth's mesosphere and lower thermosphere region extending from approximately 50 km to over 100 km in altitude. Atomic oxygen is notoriously difficult to measure, especially with remote sensing techniques from orbiting satellite sensors. It is typically inferred from measurements of the ozone concentration in the day or from measurements of the Meinel band emission of the hydroxyl radical (OH) at night. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite measures OH emission and ozone for the purpose of determining the O-atom concentration. In this paper, we present the algorithms used in the derivation of day and night atomic oxygen from these measurements. We find excellent consistency between the day and night O-atom concentrations from daily to annual time scales. We also examine in detail the collisional relaxation of the highly vibrationally excited OH molecule at night measured by SABER. Large rate coefficients for collisional removal of vibrationally excited OH molecules by atomic oxygen are consistent with the SABER observations if the deactivation of OH(9) proceeds solely by collisional quenching. An uncertainty analysis of the derived atomic oxygen is also given. Uncertainty in the rate coefficient for recombination of O and molecular oxygen is shown to be the largest source of uncertainty in the derivation of atomic oxygen day or night.

[1] The Upper Mesosphere–Lower Thermosphere (UMLT) region of the atmosphere is known to vary on many temporal and spatial scales. However, this region of the atmosphere is very difficult to measure and monitor continuously. In this paper, we demonstrate an intriguing connection between mesopause temperatures and the intensity of very low frequencies (VLF) narrowband (NB) signals reflected off the lower ionosphere. The temperature data used are from the SABER instrument onboard the TIMED satellite, while the VLF data are obtained from various ground-based receiving systems. The results of the analysis show a high anticorrelation between temperature and VLF amplitude. It is shown that the variability of the UMLT temperatures and VLF amplitudes can be explained by global seasonal solar irradiance changes (~72% of the variability), while the remaining variability has its origins from other sources (~28%). High-resolution mesopause temperature estimates might be achieved in the future by combining VLF NB observations and calculated solar irradiance variability (as a function of hour, day, and location, i.e., latitude).

[1] Parameterizations of incoming longwave radiation are increasingly receiving attention for both low and high elevation glacierized sites. In this paper, we test 13 clear-sky parameterizations combined with seven cloud corrections for all-sky atmospheric emissivity at one location on Haut Glacier d'Arolla. We also analyze the four seasons separately and conduct a cross-validation to test the parameters’ robustness. The best parameterization is the one by Dilley and O'Brien, B for clear-sky conditions combined with Unsworth and Monteith cloud correction. This model is also the most robust when tested in cross-validation. When validated at different sites in the southern Alps of Switzerland and north-western Italian Alps, all parameterizations show a substantial decrease in performance, except for one site, thus suggesting that it is important to recalibrate parameterizations of incoming longwave radiation for different locations. We argue that this is due to differences in the structure of the atmosphere at the sites. We also quantify the effect that the incoming longwave radiation parameterizations have on energy-balance melt modeling, and show that recalibration of model parameters is needed. Using parameters from other sites leads to a significant underestimation of melt and to an error that is larger than that associated with using different parameterizations. Once recalibrated, however, the parameters of most models seem to be stable over seasons and years at the location on Haut Glacier d'Arolla.

East Asia is a major dust source in the world. Mineral dusts in the atmosphere and their interactions with clouds and precipitation have great impacts on regional climate in Asia, where there are large arid and semiarid regions. In this review paper, we summarize the typical transport paths of East Asian dust, which affect regional and global climates, and discuss numerous effects of dust aerosols on clouds and precipitation primarily over East Asian arid and semiarid regions. We hope to provide a benchmark of our present understanding of these issues. Compared with the aerosols of Saharan dust, those of East Asian dust are more absorptive of solar radiation, and its direct radiative forcing at the top of atmosphere is nearly positive or nil. It means that aerosols of East Asian dust can influence the cloud properties not only by acting as cloud condensation nuclei and ice nuclei (via first indirect effect, second indirect effect, and invigoration effect) but also through changing the relative humidity and stability of the atmosphere (via semidirect effect). Converting visible light to thermal energy, dust aerosols can burn clouds to produce a warming effect on climate, which is opposite to the first and second indirect effects of aerosols. The net dust aerosol radiative effects are still highly unclear. In addition, dust can inhibit or enhance precipitation under certain conditions, thus impacting the hydrological cycle. Over Asian arid and semiarid regions, the positive feedback loop in the aerosol-cloud-precipitation interaction may aggravate drought in its inner land.

In this paper, we reconstruct the vertical profile of volcanic ash emissions by assimilating satellite data and ground‐based observations using a modified trajectory‐based 4D‐Var (Trj4DVar) approach. In our previous work, we found that the lack of vertical resolution in satellite ash column data can result in a poor estimation of the injection layer where the ash is emitted into the atmosphere. The injection layer is crucial for the forecast of volcanic ash clouds. To improve estimation, Trj4DVar was implemented, and it has shown increased performance in twin experiments using synthetic observations. However, there are some cases with real satellite data where Trj4DVar has difficulty in obtaining an accurate estimation of the injection layer. To remedy this, we propose a modification of Trj4DVar, test it with synthetic twin experiments, and evaluate real data performance. The results show that the modified Trj4DVar is able to accurately estimate the injection height (location of the maximal emission rate) by incorporating the plume height (top of the ash plume) and mass eruption rate data obtained from ground‐based observations near the source into the assimilation system. This will produce more accurate emission estimations and more reliable forecasts of volcanic ash clouds. Also provided are two strategies on the preprocessing and proper use of satellite data.

In the late southern winter of 1998, Centre National d'Etudes Spatiales (CNES), the French Space Agency, released six 10-m-diameter, superpressure balloons from a location near Quito, Ecuador. Three balloons collapsed soon after launching, but the remaining three drifted westward for a few weeks at altitudes between 19 and 20 km. Two of those balloons crossed the Pacific Ocean before falling above the “maritime continent,” while the other completed a revolution around the Earth and crossed the Pacific for a second time before its final fall. Despite the small number and the relatively short duration of the flights, the balloons provided a unique in situ data set for the lower equatorial stratosphere. This part 1 of a two-part paper describes this data set and analyzes outstanding features in the planetary scales. Part 2 focuses on gravity-wave scale. It is argued that balloon trajectories over the Pacific are primarily determined by the westward drift during the easterly phase of the equatorial quasi-biennial oscillation (QBO) and the meridional velocity field of a mixed Rossby-gravity (Yanai) wave with an apparent period of 4 days and zonal wave number 4. This wave appears to have two episodes of amplification during the balloon flights. It is also argued that the balloons show evidence of oscillations with periods between 2 and 4 days and of a Kelvin wave with an apparent period close to 10 days and zonal wave number 1. In this way, the balloon behavior provided a pictorial view of air parcel trajectory in the equatorial lower stratosphere. It is stated that larger balloon campaigns can provide excellent in situ data sets for studies on the dynamics and composition of the middle atmosphere.

Biomass consumption and carbon release rates during the process of forest clearing by fire in five test plots are presented and discussed. The experiments were conducted at the Caiabi Farm, near the town of Alta Floresta, state of Mato Grosso, Brazil, in five square plots of 1 ha each, designated A, B, C, D, and E, with different locations and timing of fire. Plot A was located in the interface with a pasture, with three edges bordering on the forest, and was cut and burned in 1997. Plots B, C, D, and E were located inside the forest. Plot B was cut and burned in 1997. Plot C was inside a deforested 9-ha area, which was cut and burned in 1998. Plot D was inside a deforested 4-ha area, which was cut in 1998 and burned in 1999. Plot E was inside a deforested 4-ha area, which was cut and burned in 1999. Biomass consumption was 22.7%, 19.5%, 47.5%, 61.5%, and 41.8%, for A, B, C, D, and E, respectively. The effects of an extended curing period and of increasing the deforested area surrounding the plots could be clearly observed. The consumption, for areas cut and burned during the same year, tended toward a value of nearly 50% when presented as a function of the total area burned. The aboveground biomass of the test site and the amount of carbon before the fire were 496 Mg ha−1 and 138 Mg ha−1, respectively. Considering that the biomass that remains unburned keeps about the same average carbon content of fresh biomass, which is supported by the fact that the unburned material consists mainly of large logs, and considering the value of 50% for consumption, the amount of carbon released to the atmosphere as gases was 69 Mg ha−1. The amounts of CO2 and CO released to the atmosphere by the burning process were then estimated as 228 Mg ha−1 and 15.9 Mg ha−1, respectively. Observations on fire propagation and general features of the slash burnings in the test areas complete the paper.

In this paper we demonstrate how ground-based measurements of selected airglow emission features may be used to determine the vertical distribution of atomic oxygen in the upper mesosphere and lower thermosphere. The technique used is based on a method first suggested by Sharp and McDade [1996] and exploits differences between the kinetics of specific oxygen airglow features to determine key parameters related to the atomic oxygen vertical distribution. The technique is applied to ground-based measurements of the OI 557.7 nm green line, the O 2 Atmospheric (0-1) band, and the OH Meinel (9-4) band emissions made at Cachoeira Paulista, Brazil (23°S, 45°W) from January 1987 to June 1994. In order to compare the results obtained here with observations, the derived atomic oxygen density profiles are used to forward calculate hydroxyl nightglow profiles which are then compared with profiles measured by the Wind Imaging Interferometer (WINDII) experiment on board the Upper Atmosphere Research Satellite (UARS). This comparison shows good agreement for the seasonally averaged nocturnal behavior of both the peak altitude and the peak volume emission rate.

Adjacency effect is known to reduce apparent surface contrast by decreasing the top of the atmosphere radiance over bright pixels and increasing the brightness of the dark pixels. This effect is systematic and thus becomes important for the land remote sensing applications developed for use with either dark or bright targets. In this paper we trace the error caused by adjacency effect in the data processing chain from aerosol retrieval over dark targets to the atmospheric correction of the top of the atmosphere radiance. A systematic overestimation of the retrieved aerosol optical thickness and underestimation of surface albedo is demonstrated in accurate numeric simulations for a variety of atmospheric conditions and surface models. Results obtained suggest that 3-D radiation effects should be taken into account not only in the atmospheric correction algorithms but also in the aerosol retrieval over land at a high-to-medium (up to 1 km) resolution of sensor.

This paper presents a chemical assimilation system based on the variational method. It has been applied to an off-line stratospheric three-dimensional chemical trans- port model. This technique determines the best model initial conditions that minimize the model errors when compared to a set of observations for a predefined time window. The system is applied to the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) measurements for the November 5-11, 1994, mission. Observed species are O3 ,C H4, HNO3 ,C lONO2 ,N 2O5 ,N 2O, and CFC-11. For an assimilation pe- riod of 12 hours, CRISTA observations are well estimated by the assimilation system. These results vary according to the species considered and depend on the CRISTA's ob- servational error. In particular, assimilated ozone differ from CRISTA by less than 5%. Analyses have been compared with independent observations in order to validate the as- similation system. It was found that observations by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment and the Halogen Occultation Experiment (HALOE) agree well with the analyses. These comparisons suggested systematic differences between CRISTA and HALOE or ATMOS. Unconstrained constituents like NOx and HCl are in- fluenced through chemical coupling and show small discrepancies with ATMOS and HALOE data.

The compound 1,2,2,2-Tetrafluoroethyl Trifluoromethyl Ether, CF3OCHFCF3 (HFE-227), is currently being considered as a potential replacement for certain halocarbons, particularly for perfluorocarbons (PFCs), as a dry etching gas in the semiconductor industry. For this reason, it is important to determine the potential environmental effects resulting from the use and emissions of this compound. In this paper, the atmospheric lifetime, radiative forcing, and Global Warming Potentials (GWPs), an important measure of the potential effects of a gas on climate, are evaluated for this compound using our zonally averaged chemical transport and radiative transfer models of the atmosphere. To our knowledge, this is the first time this compound has been evaluated with such atmospheric models. In order to calculate the lifetime and radiative forcing, the rate constants and infrared cross sections of this compound were measured in laboratories at Illinois and Purdue, and results are reported here. The model-evaluated atmospheric lifetime is 11.3 years, mainly due to reaction with OH radicals. The model-evaluated instantaneous-clear-sky radiative forcing is 0.38 W m−2 ppbv−1, about 45% lower than previously estimated [Imasu et al., 1995]. However, the model-estimated cloudy-sky adjusted forcing, needed to calculated GWPs, is about 25% lower than the model-estimated instantaneous-clear-sky forcing. The GWPs are calculated to be 3400, 1200, and 370 for 20, 100, and 500 year time horizons, respectively.

The net exchange of CO 2 between the biosphere and atmosphere is realized as a difference between the fluxes associated with photosynthesis and respiration. This paper contrasts the turbulent transport mechanics of two dominant pathways affecting this exchange. Using high-frequency measurements from an experiment conducted at the Duke Forest in North Carolina, wavelet analysis is applied to time series of carbon dioxide and water vapor concentrations in order to (1) determine the dominant eddy sizes involved in the net exchange of these constituents, (2) resolve the eddy size and timescales involved in the intermittent release of CO 2 from the forest floor to the atmosphere, and (3) relate the boundary layer turbulent characteristics to the transport of air enriched in CO 2 from soil respiration. During the daytime hours, when photosynthesis and soil respiration are active in this pine forest and evapotranspiration is taking place, air enriched in both CO 2 and water vapor is indicative of transport from the forest floor. Thus the coherent turbulent structures associated with these transport events are identified and conditionally analyzed from the time series by wavelet transforms, which retain information in the time domain as well as the frequency domain. The dominant flux-carrying eddies between the canopy and atmosphere were approximately 63 m in diameter, about four times the height of the canopy. Eddies that were most effective in transporting air enriched in CO 2 from below the canopy to the atmosphere were found to be approximately 8 m in diameter, on the order of one half the canopy height. Conditional sampling shows that the prevalence of air enriched in both CO 2 and water vapor is related to the rate of turbulent kinetic energy production measured from 24 approximately half-hour time series corresponding to unstable atmospheric conditions.

We present spectrally analyzed high-resolution balloon measurements of vertical temperature and horizontal wind in the troposphere and lower stratosphere in French Guyana (≈5°N, 52°W) made in 1996/1997. The paper is principally concerned with spectra at vertical scales from a few kilometers down to 100 m. A special balloon has been developed to solve scales below 500 m. For the first time, the equatorial region has been studied extensively at this resolution. We have found wind and temperature spectra following the canonical shape in the logarithmic representation with a slope of ≈−3 for wavenumbers ≧10−3 cycle/m with day-to-day significant amplitude variations but a mean spectrum constant with the seasons. We have found isotropic wave horizontal direction of propagation for the troposphere and anticorrelated with the quasi-biennial oscillation in the stratosphere. The vertical propagation of wave has been found symmetric in the troposphere but highly asymmetric in the stratosphere with dominant upward propagation. We were not able to find any correlation between deep moist convection and wave activity. The ratio kinetic to potential energy spectra, which is the ratio of velocity spectra to temperature spectra multiplied by N2T¯2b/g2 for the troposphere and stratosphere, is constant versus the vertical wavenumber and in good agreement with a model intrinsic frequency spectrum varying as ω−p with 5/3 ≤ p ≤ 2 and without necessity of energy enhancement near the inertial frequency which is close to zero at the latitude measurements.

We derive rates of energy deposition in the mesosphere due to the absorption of solar ultraviolet radiation by ozone. The rates are derived directly from measurements of the 1.27-microns oxygen dayglow emission, independent of knowledge of the ozone abundance, the ozone absorption cross sections, and the ultraviolet solar irradiance in the ozone Hartley band. Fifty-six months of airglow data taken between 1982 and 1986 by the near-infrared spectrometer on the Solar-Mesosphere Explorer satellite are analyzed. The energy deposition rates exhibit altitude-dependent annual and semi-annual variations. We also find a positive correlation between temperatures and energy deposition rates near 90 km at low latitudes. This correlation is largely due to the semiannual oscillation in temperature and ozone and is consistent with model calculations. There is also a suggestion of possible tidal enhancement of this correlation based on recent theoretical and observational analyses. The airglow-derived rates of energy deposition are then compared with those computed by multidimensional numerical models. The observed and modeled deposition rates typically agree to within 20%. This agreement in energy deposition rates implies the same agreement exists between measured and modeled ozone volume mixing ratios in the mesosphere. Only in the upper mesosphere at midlatitudes during winter do we derive energy deposition rates (and hence ozone mixing ratios) consistently and significantly larger than the model calculations. This result is contrary to previous studies that have shown a large model deficit in the ozone abundance throughout the mesosphere. The climatology of solar energy deposition and heating presented in this paper is available to the community at the Middle Atmosphere Energy Budget Project web site at http://heat-budget.gats-inc.com.

Wintertime cold-air outbreaks from the polar ice and land surfaces over the open sea lead to organized convective patterns (OCP) in the atmosphere, visible as cloud streets and cellular cloud structures on satellite images. Large amounts of energy are transferred from the ocean to the atmosphere and convective organized flows contribute substantially to the vertical fluxes of heat, moisture and momentum in the boundary layer. However, little is known about the frequency of OCP occurrence. The paper is aimed to fill this gap and presents a climatology of OCP occurrence over the Greenland Sea and Barents Sea. The study is based on daily NOAA satellite images of 10 winters (November till March) for the years from 1985/1986 to 1994/1995. It covers the area from 70°N to 82.5°N and from 20°W to 60°E and is subdivided into 40 subareas with a grid size of 10 degrees in longitude and 2.5 degrees in latitude. OCP occur in more than 50% of the time averaged over the 10 winters. Complete absence of OCP is observed in less than 5% of the time. OCP occur most frequently over the Westspitsbergen current and around the border between the Greenland Sea and the Barents Sea. Cloud streets are the dominating OCP mode close to the ice edge, whereas cellular structures dominate at farther distances. Variability of OCP occurrence may be large on all timescales. A relation between ice extent and frequency of OCP occurrence is present occasionally.

Observational studies reveal the oscillatory nature of coupled stratosphere-troposphere variability, which is characterized by a slowly downward propagating anomalous zonal-mean zonal wind during the winter. The term “slowly” is employed compared to the rapid variation associated with stratospheric sudden warmings. In fact, strong stratospheric warming events are embedded in this slowly propagating variability as is shown in a companion paper [Kodera et al., this issue]. In the present study, the mechanism producing such variability at all levels of the atmosphere is investigated by developing a simple model that extends from the Earth's surface to 80 km altitude. The model is a quasi-geostrophic channel model similar to that used by Holton and Mass [1976], but it includes two meridional Fourier components and latitudinal variation in the gradient of the Coriolis parameter. By this extension, the present model can incorporate both the subtropical and polar night jet and also treat the horizontal propagation of planetary waves as well as vertical propagation. The results of the simulation reproduce qualitatively well the main observed features: Interaction between the planetary waves and zonal-mean flow produces oscillations in the winter stratosphere, and zonal wind anomalies created in the subtropics of the stratopause propagate downward into the polar region of the troposphere, which provoke changes in the meridional propagation of tropospheric planetary waves.

During the Arecibo Initiative in Dynamics of the Atmosphere (AIDA) campaign there were several unusual observations of the O 2 Atmospheric (0,1) and OH Meinel (6,2) brightness fluctuations being nearly 180° out of phase. In this paper we discuss data from May 8-9, 1989, during which meteor radar and airglow instrumentations were operating and thus wind data were available. We show that the nearly out-of-phase result on this night is due to the fact that the OH Meinel brightness and temperature are out of phase while the O 2 atmospheric temperature and brightness are nearly in phase. The characteristics of the wave causing the out of phase fluctuations are derived and comparisons are made between results obtained by the Aerospace nightglow camera and those obtained by the York University airglow camera [Zhang et al., 1993]. Although there are differences between them, both of the instrumental data sets are consistent with the presence of a wave with a horizontal wavelength ≥600 km and a period of several hours. An analysis of these data shows that the out-of-phase relationship is most likely due to strong wave reflection in the lower thermosphere caused by thermal gradients and wind shears.

As the contamination of β-hexachlorocyclohexane (β-HCH) in the Arctic air, seawater, and biota is an environmental concern, there is a need for emission inventories of β-HCH to be used by the modeling community to predict the fate and transport of β-HCH. This paper presents such emission inventories for β-HCH. The total global usage of β-HCH between 1945 and 2000 is estimated at 850 kt, 230 kt of which was emitted to the atmosphere over the same time period. Usage of β-HCH was estimated to be around 36 kt in 1980 and 7.4 kt in 1990. Total β-HCH emissions in 1980 were 9.8 kt with 83% attributed to the application in 1980 and 17% to soil residues due to prior applications. Total β-HCH emissions in 1990 were 2.4 kt with 78% attributed to the application in 1990 and 22% to soil residues. While it assumed that no usage of technical HCH occurred in 2000, the global β-HCH emissions in this year due to soil residues were estimated at 66 t. It has shown that the global β-HCH emissions have undergone a “southward t...

There is a general consensus that warm temperatures throughout Precambrian were caused by very high CO2 or CH4 atmospheric concentrations. Episodes of glaciation in the early and late Proterozoic were caused by a reduction in these greenhouse gases through intensive weathering or large reduction in the methane producing bacteria population. There are suggestions that these episodes were global because the continents occupied low latitudes at or near the time of glaciation. Here it is reported that high-obliquity throughout the Precambrian serves as a mechanism for producing warm temperatures throughout the Archean and glaciation in the late Proterozoic. In this paper, Global climate model simulations using high-obliquity values that range from 54° to 70° are undertaken. These simulations use a simple 50-m slab ocean, a faster rotation rate corresponding to an 18 hour day, an idealized supercontinent located in the tropics which has a north-south mountain chain and CO2 concentrations which range from 170 to 3400 ppmv. Further, four simulations under global ocean conditions, faster rotation rate and reduced solar constant (15 and 20%) using present-day and high-obliquity values have been undertaken. The simulations show warm conditions with high-obliquity but Snowball Earth conditions for the present-day obliquity in the global ocean simulations. Near Snowball Earth conditions also occur for the tropical supercontinent simulation for an obliquity of 70° and CO2 concentrations less than 1020 ppmv. Together, these simulations show that for high-obliquity the ocean remains relatively warm while land areas are cooled because of their lower heat capacity. Large fluxes of latent heat from the ocean balance the longwave energy lost at the top of the atmosphere thereby keeping high latitudes warm during winter seasons. It is suggested from this results that lower and upper limits of 65°–70° for obliquity serve as a solution for the Faint-Young Sun Paradox and low-latitude Proterozoic. Finally, the high-obliquity-climate relationship sheds some insight on the carbon isotope (δ13C) excursions during the late Proterozoic.

During the Tropical Ocean-Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) intensive observing period (IOP) (November 1992 to February 1993), two pronounced Madden-Julian oscillation (MJO) events were observed and have been intensively studied. To provide a necessary climatological basis for the case study as well as to evaluate how typical the COARE MJO cases are and to what degree conclusions made from these cases can be generalized, we compare the MJOs that occurred during the COARE IOP with a 15-year climatology. In this paper, along with a description of the characteristics of large-scale background including flow patterns, OLR and SST, the emphasis is placed on the intensity and propagation of the oscillations exhibited in organized convection and atmospheric circulation. Moreover, the maintenance of perturbation kinetic energy (PKE) associated with 30- to 60-day variability containing the MJOs is compared as well. The COARE IOP occurred in a lingering period between the persistence and the rejuvenation of the warm ENSO episode of 1992–1993. The intraseasonal oscillations in the convective activity and large-scale circulation are intensified during the IOP, and the maximum intensification is located in the region of central Pacific. Two MJO events in the COARE IOP are typical in terms of phase propagation. The major features of the energy transformation processes, such as the predominant role of the generation of the perturbation available potential energy (PAPE) by convective heating and its conversion into the PKE in the maintenance of the MJOs, found in the COARE IOP, are also displayed in the climatology indicating the generality of the results obtained from the COARE case study.

This paper describes the development of a process-based water and energy balance model for use in high latitudes under both summertime and wintertime conditions. The model is developed as a part of the Boreal Ecosystem-Atmosphere Study (BOREAS). The model differs from its original version in the representation of hydrological processes specific to climatic and ecologic conditions in high latitudes: the impact of an organic layer on the water and energy balance of the boreal forest; the parameterization of frozen ground and snow accumulation and ablation; and the effect of open water bodies on the calculation of the radiative energy and water budget. The model can be run either in a fully distributed or an aggregated statistical mode. The resulting macroscale hydrological model can be used, off line, to study the energy and water balance of the boreal forest and potentially can be used as a land-atmosphere parameterization in atmospheric models.