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Improving near-cloud aerosol measurements is important for better understanding two critical aspects of climate, aerosol-cloud interactions and the direct radiative effect of aerosols. This study aims at better understanding the uncertainties that arise in satellite measurement of aerosols because current data interpretation methods don't consider 3D radiative processes. For this, the paper presents a statistical analysis of a yearlong global dataset of co-located MODIS and CALIOP observations and theoretical simulations. The results reveal that CALIOP-observed particle size and optical thickness, and MODIS-observed solar reflectance increase systematically in a wide zone around clouds. It is estimated that near-cloud changes in particle populations (including aerosols and undetected cloud particles) are responsible for roughly two thirds of the observed increase in 0.55 μm MODIS reflectance. The results also indicate that 3D radiative processes play an important role in near-cloud reflectance enhancements, while instrument blurring plays a modest role. [ABSTRACT FROM AUTHOR]

In April 2010, the volcanic ash cloud from the Eyjafjalla volcano in Iceland strongly impacted aviation in Europe. Several other incidents in the past have shown that volcanic ash can have severe consequences on aviation. One operational necessity is, therefore, to determine whether a pilot has the means to avoid flying through potentially dangerous volcanic ash just by visual observation of the sky from the cockpit of an aircraft. Here we investigate how clouds affect the visibility of a volcanic ash aerosol layer for an observer in the cockpit of an aircraft using a 3D Monte Carlo radiative transfer model MYSTIC. This study builds on the results of a previous study on the visibility of airborne volcanic ash in Weinzierl et al. (2012) where we considered the cloud-free case. With clouds, the discernibility of ash layers is substantially reduced. Even layers with comparably high mass concentrations of 2 mg m-3 might not be visible for uninformed observers. [ABSTRACT FROM AUTHOR]

Aerosol optical depth (AOD) is being measured in Innsbruck, Austria. Since 2007 a precision filter radiometer (PFR) is set up at 620 m above sea level in order to characterize the aerosol conditions at this Alpine site. The five year time series is analyzed with respect to AOD, the Angstrom coefficient a and the curvature of the 1n(τ)-1n(λ) relationship γ. Information on the fine mode particle fraction and its modal radius is obtained with a graphical method. For special cases such as Saharan dust events the King inversion algorithm is applied. The PFR measures direct irradiance at 368 nm, 412 nm, 500 nm and 862 nm. It is also employed as a network instrument in the Global Atmosphere Watch (GAW) Program of the World Meteorological Organization. The Innsbruck annual aerosol pattern reveals monthly mean AOD at 500 nm in winter between 0.05 and 0.1 and up to 0.22 in summer. Daily AOD at 500 nm remains below 0.5 for all measurement days. This seasonality in AOD is typical for mid-latitude sites. The overall mean γ is -1.53+/-0.29 and the overall mean γ is -0.53+/-0.26. These parameters indicate submicron aerosols prevailing in Innsbruck. On 93% of the days a fine mode fraction of more than 70% is detected. A fine mode radius between 0.1 μm and 0.15 μm is observed on 90% of the days. [ABSTRACT FROM AUTHOR]

In this study the main features of the hydrological cycle over the South American region are documented with three reanalysis datasets and two observation-derived precipitation products. Rather than attempting to 'close the water balance' that requires additional terms, many model dependent, we focus on the individual terms of the water cycle. An additional analysis is also presented in this work to investigate the role of the transport of moisture over the La Plata Basin (LPB) and South Atlantic Convergence Zone (SACZ) in the precipitation regimes from 1979 to 2007. [ABSTRACT FROM AUTHOR]

We present the results of continuous longwave downwelling irradiance (LDI) monitoring in Moscow from April 2008 to March 2012, which has been in operation at the Meteorological Observatory of Moscow State University (MSU MO). The measurements are carried out within wavelength range 3.5-50 μm using a precision infrared radiometer (PIR) which is regularly calibrated against international standards and tested in the Physical Meteorological Observatory in Davos (Switzerland) with accuracy comparable to the BSRN measurements (2-4 W/m2). According to these measurements the impact of various atmospheric factors on LDI has been assessed. For clear sky conditions we estimated the effects of temperature T and water vapor content W (cm). Water vapor content was evaluated from Cimel sunphotometer data (AERONET) in the 940 nm channel. A simple equation is proposed to retrieve the LDI in the absence of cloudiness and aerosol optical thickness at 500 nm (AOT500) less than 0.7 which has been compared with the results of other parameterizations. In conditions with a smoky aerosol with extremely high aerosol optical thickness the LDI dependence on AOT500 should be taken into account. According to our results the effect of extremely high AOT500 of about 5-6 provides an LDI increase of about 50 Wm-2 or 10-15%. The analysis of cloud effects reveals a significant growth of LDI in cloudy conditions up to 30% during daytime and up to 25% at night. The upper layer thin cloudiness does not affect LDI. On average, annual LDI in Moscow was 301 Wm-2 with seasonal changes of about 130 Wm-2 due to variations mainly in temperature and cloud cover. For the entire observation period the LDI changed from 424 Wm-2 in July 2009, to 136 Wm-2 in February 2012. Maximum LDI values were observed under optically thick low layer cloudiness. Minimum LDI values were observed in clear sky conditions and low temperatures. The average LDI daily range is 18-33 Wm-2 in summer and 6-18 Wm-2 in winter conditions. [ABSTRACT FROM AUTHOR]

Space-based Earth Radiation Budget (ERB) measurements are ready to take their next major evolutionary step beyond the ERBE three-satellite constellation of the 1980s. This step would complete the ERBE vision by using not just three but dozens of satellites, and it would complete the GERB vision by providing global diurnal cycle. Such a large constellation would measure true diurnal cycle, without long chains of assumptions and extrapolations, allowing ERB to take its place alongside the other synoptic variables that are assimilated in weather and climate models, and bringing ERB back to a forefront research area. This constellation approach would make it possible to study ERB for rapidly evolving large-scale phenomena. It would also allow, for the first time, the measurement of the true Earth Radiation Imbalance, a crucial quantity, much in the news of late, for testing climate models and for predicting the future course of global warming. Among many side benefits, the greatest would be that all interested nations could participate. Such nations would merely need to meet the instrument functional requirements and find rides to space, and the system could thus grow with time, allowing continuously improved sampling, rapid deployment of new technologies with minimal damage to data continuity, and economies of scale. This is really the perfect ERB system for a budget-constrained decade. [ABSTRACT FROM AUTHOR]

We propose a method for cloud UV transmission evaluating on the base of TOMS/OMI LER (Lambertian Equivalent Reflectivity) dataset, which provides more accurate retrievals of UV levels at ground in conditions with high surface albedo. For the improvement of cloud UV transmission estimates, in addition to TOMS/OMI LER data we used two datasets: low layer cloud amount data from ECMWF ERA Interim reanalysis, and surface albedo retrievals according to the method proposed in [1]. The obtained results were tested against experimental data of the Meteorological Observatory of Moscow State University (MSU MO, 55.7N, 37.5E), which included long-term measurements of erythemally weighed radiation, and UV radiation in the spectral range 300-380 nm. The comparisons were made with the cloud UV transmission estimates, obtained by the standard TOMS LER approach [2]. We showed that the cloud UV transmission estimates from the proposed method gave a better agreement with the experimental data compared with the results obtained from the standard TOMS LER approach for winter conditions with high surface albedo. During warm period the retrievals obtained from different methods are in a satisfactory agreement. [ABSTRACT FROM AUTHOR]

Several sensors are dedicated to cloud observations. Among them, POLDER/PARASOL measures total and polarized visible radiances in up to 16 directions. As for other sensors, the POLDER cloud retrieval algorithm is based on the assumption that clouds are plan-parallel, homogeneous and infinite. To assess the cloud heterogeneities impacts on POLDER radiances and thus on retrieved cloud parameters, we developed a tri-dimensional radiative transfer model called 3DMCPOL allowing the computation of total and polarized radiances of 3D cloud fields. The input cloud properties are simulated with a model called 3Dcloud, which is based on a simplified dynamic/thermodynamic scheme to get cloud characteristic shape coupled with a Fourier stochastic approach to enforce cloud scale invariance. The POLDER algorithm is next applied to the simulated radiances to assess the 3D errors on the retrieved cloud parameters. [ABSTRACT FROM AUTHOR]

A microphysical model is presented for the surface layer marine and coastal atmospheric aerosols that is based on long-term observations of size distributions for 0.01-100 μm particles in different geographic sites. The fundamental feature of the model is a parameterization of amplitudes and widths for aerosol modes of the aerosol size distribution function (ASDF) as functions of fetch and wind speed. The shape of the ASDF and its dependence on meteorological parameters, altitudes above sea level (H), fetch (X), wind speed (U) and relative humidity (RH) are investigated. The spectral profiles of the aerosol extinction coefficients calculated by MaexPro (Marine Aerosol Extinction Profiles) are in good agreement with observational data and the numerical results obtained from the Navy Aerosol Model (NAM) and the Advanced Navy Aerosol Model (ANAM). Moreover, MaexPro was found to be an accurate and reliable tool for investigation of the optical properties of atmospheric aerosols. [ABSTRACT FROM AUTHOR]

Exposure to solar ultraviolet (UV) radiation is the main causative factor for skin cancer. UV exposure depends on environmental and individual factors, but individual exposure data remain scarce. While ground UV irradiance is monitored via different techniques, it is difficult to translate such observations into human UV exposure or dose because of confounding factors. A multi-disciplinary collaboration developed a model predicting the dose and distribution of UV exposure on the basis of ground irradiation and morphological data. Standard 3D computer graphics techniques were adapted to develop a simulation tool that estimates solar exposure of a virtual manikin depicted as a triangle mesh surface. The amount of solar energy received by various body locations is computed for direct, diffuse and reflected radiation separately. Dosimetric measurements obtained in field conditions were used to assess the model performance. The model predicted exposure to solar UV adequately with a symmetric mean absolute percentage error of 13% and half of the predictions within 17% range of the measurements. Using this tool, solar UV exposure patterns were investigated with respect to the relative contribution of the direct, diffuse and reflected radiation. Exposure doses for various body parts and exposure scenarios of a standing individual were assessed using erythemally-weighted UV ground irradiance data measured in 2009 at Payerne, Switzerland as input. For most anatomical sites, mean daily doses were high (typically 6.2-14.6 Standard Erythemal Dose, SED) and exceeded recommended exposure values. Direct exposure was important during specific periods (e.g. midday during summer), but contributed moderately to the annual dose, ranging from 15 to 24% for vertical and horizontal body parts, respectively. Diffuse irradiation explained about 80% of the cumulative annual exposure dose. [ABSTRACT FROM AUTHOR]

The microwave radiometer ADMIRARI has taken part in several NASA Global Precipitation Measurement (GPM) ground validation (GV) field experiments in different locations around the globe. ADMIRARI is a multifrequency dual-polarized microwave radiometer with the ability to distinguish the cloud and rain component of the liquid water content observed in the atmospheric column. The present is a review of ADMIRARI's participation in four GPM/GV field campaigns from March 2010 to February 2012. Each of these experiments tackled different precipitation regimes, from convective, to mixed-phase, warm to light rain and snowfall. [ABSTRACT FROM AUTHOR]

As a part of environmental studies in the southern hemisphere, the CEILAP Lidar Division with the financial support of JICA (Japan International Cooperation Agency) and the collaboration of IPSL France, mounted a ground based remote sensing site at Río Gallegos city (51° 36'S, 69° 19'W), at southern part of South America for the measurements of stratospheric ozone, with lidar remote sensing techniques and passive sensors to measure solar UV irradiance. The Patagonian region is characterized by high cloud cover during day changing strongly the distribution of UV radiation that reaches the ground surface. During the spring season some overpasses of ozone hole are masked by cloud cover avoiding the increase in UVB radiation. Solar UV radiation measured with multiband filter radiometer GUV-541 and Biometer manufactured by Biospherial Inc. San Diego and the Yankee Environmental Systems (YES) companies respectively. We present nine study days in the period 2007-2011 where total ozone column was below 250 DU focusing the impact that cloud cover had on the temporal evolution of these events. [ABSTRACT FROM AUTHOR]

Studies in the past have shown that solar shortwave radiation that has been Raman scattered in the ocean, and therefore undergone a wavelength shift, can contribute significantly to the signals observed by remote sensing satellites. While radiative transfer models that qualitatively approximate the effect of water Raman scattering on the water leaving irradiance have been available for a while, we have developed a new version of the radiative transfer code MOMO, which enables the accurate and fully angle resolved inclusion of inelastic scattering sources, and therefore allows detailed quantitative analyses of the effect on the light field in the ocean-atmosphere system. This article focuses on a study performed with this new model on the impact of azimuthally averaging the Raman scattering phase function, which is done in some RT models and significantly decreases computation time, on the water-leaving radiance. [ABSTRACT FROM AUTHOR]

Microphysical and radiative measurements in boundary-layer mixed-phase clouds were collected during a May-June 2008 tethered balloon campaign in Ny-Ålesund, Norway in the high Arctic. The instruments deployed on the tethered balloon platform included a radiometer, a cloud particle imager, and a meteorological package. The mean intensities estimated from the radiometer measurements on the balloon were used to quantify the vertical structure of the mixed phase cloud system, while the downward irradiances measured by an upward looking ground-based radiometer were used to constrain the total cloud optical depth. The time evolution of the liquid water and ice particle cloud optical depths was estimated by using a comprehensive radiative transfer model. [ABSTRACT FROM AUTHOR]

Airborne spectral radiative data are used for estimation of bluing of radiation within clouds. The kind of vector with three components (irradiance or radiance at UV, visible and near IR channels) is considered and its transformation within cloud is analyzed. A similar procedure has used for the case of clear atmosphere. Russian spectral observation of upward and downward fluxes and NASA observation with Cloud Absorption Radiometer (CAR) of diffused intensity in 8 spectral channels are taken for consideration in cloudy and clear atmosphere. Spectral dependence of the scattering coefficient in clouds was revealed for retrieved optical parameters from radiative observations of both kinds. Possible explanation is proposed that confirms mutual influence of molecular and Mie multiple scattering in the cloudy media. [ABSTRACT FROM AUTHOR]

The EPS-SG Multi-Viewing Multi-Channel Multi-Polarization Imaging Mission (3MI) is a radiometer dedicated to aerosol characterization for climate monitoring, air quality forecasts and Numerical Weather Prediction (NWP). The purpose of the 3MI concept, likewise that of the heritage missions POLarization and Directionality of the Earth's Reflectances (POLDER) and Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL), is to reconstruct a multi-spectral (from 410 to 2130 nm), multi-polarization (-60°, 0°, and +60°), and multi-angular (14 views) image of the Earth outgoing radiance at the top of the atmosphere (TOA) in order to resolve the directional anisotropy and the microphysical properties of aerosol. [ABSTRACT FROM AUTHOR]

Mineral dust aerosols are, for example, relevant for the radiative transfer in Earth's atmosphere. An important source of information on this aerosol type is provided by remote sensing using lidar systems and sun/sky photometers. We investigate the sensitivity of lidar and photometer observations to the microphysical aerosol properties in a numerical study. Knowledge of this sensitivity is required for the development of microphysical retrieval algorithms. Until recently, such retrieval algorithms were applied only to lidar or photometer observations. Quite different sensitivities for lidar and photometer are found in our study, suggesting that synergistic effects can be expected from combining the observations from both techniques. Furthermore, we compare the modeled aerosol properties to observations of Saharan mineral dust aerosols performed during the SAMUM field campaign. We determined aerosol ensembles that are consistent with the lidar as well as the photometer observations, confirming the feasibility of combining the observations from both techniques. The consistent aerosol ensembles are based on the desert mixture from the OPAC aerosol dataset, and were improved by considering mixing of absorbing and non-absorbing irregularly shaped particles. [ABSTRACT FROM AUTHOR]

Since 2004, accurate top-of-the-atmosphere (TOA) broadband reflected solar and emitted thermal fluxes are available from the Geostationary Earth Radiation Budget (GERB) instruments on board the Meteosat Second Generation satellites. In the EUMETSAT Climate Monitoring SAF, those data are used to estimate monthly and daily mean TOA radiation products as well as a monthly mean diurnal cycle product. The daily and the diurnal cycle products take advantage of the geostationary orbit of GERB. Although the averaging process of geostationary observations could seem to be an easy task, different issues have to be taken into account to derive datasets with the highest possible accuracy. The main ones concern (i) the approach used to deal with missing data in the averaging process, (ii) the homogenization of radiometric level between different GERB instruments, and (iii) the correction of drift in instrument sensitivity. Furthermore, from the user point of view, realistic characterization of the monthly, daily and diurnal cycle accuracies is needed. To this end, the inter-comparisons with similar products from CERES (e.g. EBAFs and SYN1deg) is especially interesting as the products for these 2 missions are based on totally independent assumptions and modeling steps. In this paper we present the new Climate Monitoring SAF GERB dataset, the validation results and comparisons with CERES. [ABSTRACT FROM AUTHOR]

The results of long-term (1980-2011) photosynthetically active radiation (PAR) monitoring, which have been held at the Meteorological Observatory of Moscow State University (MSU MO) are presented. The PAR measurements are carried out within wavelength ranges 380-710 nm and 400-700 nm using modified thermoelectrically pyranometer (1980-2001) and LI-COR quantum sensor (from 1999 to the present) with the accuracy 7-10%. Main attention was paid to the variability of the magnitude of the relationship between the broadband total solar radiation (Q) and PAR (QPAR). The dependence of this ratio (qPAR=QPAR/Q) on various meteorological factors is investigated. The simple empirically derived model for PAR estimation is developed. Based on these methods the long-term variations of PAR during the XX Century in the Moscow region was obtained. [ABSTRACT FROM AUTHOR]

Ozone and ultraviolet (UV) radiation are two important issues in the study of Earth's atmosphere. The anthropogenic perturbation of the ozone layer has induced change in the amount of UV radiation that reaches the Earth's surface, mainly through the Antarctic ozone hole. Also clouds have been identified as the main modulator of UV amount over short time scales. While clouds can decrease direct radiation, they can produce an increase in the diffuse component, and as a consequence the surface UV radiation may be higher than during an equivalent clear sky scenario. In particular this situation can be important when a low ozone column and partially cloud coverered skies occur simultaneously. These situations happen frequently in southern Patagonia, where the CEILAP Lidar Division has established the Atmospheric Observatory of Southern Patagonia, an atmospheric remote sensing site near the city of Río Gallegos (51°55'S, 69°14'W). In this paper, the impact of clouds on UV radiation is investigated by the use of ground based measurements from the passive remote sensing instruments operating at this site, mainly broad and moderate narrow band filter radiometers. Cloud modification factors (CMF, ratio between the measured UV radiation in a cloudy sky and the simulated radiation under cloud-free conditions) are evaluated for the study site. CMFs higher than 1 are found during spring and summer time, when lower total ozone columns, higher solar elevations and high cloud cover occur simultaneously, producing extreme erythemal irradiance at the ground surface. Enhancements as high as 25% were registered. The maximum duration of the enhancement was around 30 minutes. This produces dangerous sunbathing conditions for the Río Gallegos citizen. [ABSTRACT FROM AUTHOR]

Atmospheric data assimilation is formulated as a nonlinear optimization problem. A large-scale optimization algorithm is applied to the problem. An efficient method is developed for computing the gradient of the objective function. A numerical experiment is presented. [ABSTRACT FROM AUTHOR]

Propagation measurements at Ku-band over an earth-space path have been carried out at Kolkata (22°34′N, 88°29′E) by receiving a signal at 11.172 GHz from the satellite NSS-6 (geostationary at 95°E) since June 2004. The amplitudes of the co-polar signal and the cross-polar component have been monitored along with rain rate and drop size distribution measurements by an optical raingauge and a Joss-type disdrometer, respectively. The relationship between rain attenuation over the earth-space path and the rain rate gives an assessment of raining conditions along the satellite path. Fast fluctuations of the satellite signal amplitude are studied to indicate the effect of small scale irregularities associated with the rain events. TRMM satellite data obtained with PR and TMI indicate that the rain rate has a distinct control of rain height which increases with the former, the relationship depending on the type of rain. The propagation measurements and TRMM data have been used to study the features of rain at Kolkata. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Polarimetric Doppler radars provide an impressive experience to remotely observe the internal motions in convective storms and infer precipitation types as well as amounts. The emphasis herein is on measurements of rain. Hence, a review of recent results on relations between drop size distribution parameters is given. A description of the preferred technology for polarimetric weather radars follows. Polarimatric variables are introduced and propagation issues affecting polarimetric measurements are discussed. It is demonstrated that the relations between the polarimetric variables and rainfall yield superior estimates. Ways to restore attenuated signals are broth forth; application of these produces, at short wavelengths, estimates of unprecedented accuracy. Ample examples illustrating advantages of rain measurements with polarimetric radar are given. Overall the accuracy of polarimetric method is two to three times better than the accuracy of the method that relies only on reflectivity. Undisputed advantage of polarimetry is its discriminatory power to separate rain echoes from artifacts thus providing measurements where it is raining. A great untapped potential for retrieving parameters of the drop size distribution is also demonstrated. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Rain severely affects the propagation of electromagnetic waves above 10 GHz. Attenuation and depolarization of signals are caused by the presence of the rain drops. Rain attenuation depends in a complex manner, on the dropsize distributions, temperature and terminal velocity of rain drops, vertical and horizontal structure of the rain cell, wave length of the signal etc. depolarization depends on the non-spherocity of the rain drops. In this Review, the subject has been introduced in Section 1. In Section 2, the theory of rain attenuation has been described. Various dropsize distributions which depend on the point rain rate, on the basis of rain measurements are given in this section. In order to describe the behaviour and effects of the rain completely statistical models have been developed which are described in Section 3 on the basis of world wide measurements. This Section includes the statistical cumulative distribution of rain fall rate, rain attenuation models for terrestrial and earth-space paths, frequency and path length scaling, worst month statistics and cross-polarization statistics. Comparison between various statistical models is given in Section 4. In Section 5 we have discussed the applicability of various statistical models for different geographical regions described on the basis of extensive measurements. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

There is good observationnal evidence that the Steep Decay Phase (SDP) that is observed in most Swift GRBs is the tail of the prompt emission. The most popular model to explain the SDP is Hight Latitude Emission (HLE). Many models for the prompt emission give rise to HLE, like the popular internal shocks (IS) model, but some models do not, such as sporadic magnetic reconnection events. Knowing if the SDP is consistent with HLE would thus help distinguish between different prompt emission models. In order to test this, we model the prompt emission (and its tail) as the sum of independent pulses (and their tails). A single pulse is modeled as emission arising from an ultra-relativistic thin spherical expanding shell. We obtain analytic expressions for the flux in the IS model with a Band function spectrum. We find that in this framework the observed spectrum is also a Band function, and naturally softens with time. The decay of the SDP is initially dominated by the tail of the last pulse, but other pulses can dominate later. Modeling several overlapping pulses as a single broader pulse would overestimates the SDP flux. One should thus be careful when testing the HLE. [ABSTRACT FROM AUTHOR]

The distribution of rain rates (R) is of great interest in many fields. For example, hydrological applications such as flood forecasting depend on an accurate representation of the excess rainfall—driven by R—that does not infiltrate the soil. It is also of great concern to radio wave propagation—the theme of this symposium. Probability distribution functions (pdf) of R can now be obtained from spaceborne radar observations. Effort to evaluate these pdfs using ground observations is presented. The evaluation of instantaneous rainfall products and rain rate estimates from space is quite a challenge. Scatter plots of pixel-by-pixel comparisons of space-based R estimates with ground-based radar R estimates are extremely noisy because of sample volume discrepancies, timing and navigation mismatches, and uncertainties in the observed-radar reflectivity rain-rate Ze-R relations. Furthermore, comparisons of rainfall over daily, weekly or even monthly time scales suffer from the temporal sampling errors of the satellite where the revisit time is on the order of hours or days (e.g., the Tropical Rainfall Measuring Mission [TRMM] satellite, the future Global Precipitation Measurement [GPM] mission satellite). Consequently, an alternative approach of comparing space-based radar pdfs with pdfs derived from co-located ground-based radar observations is attractive for evaluating satellite-based precipitation products, such as those from TRMM precipitation radar (PR). We will present comparisons of R estimates from the TRMM PR and co-located data from gauge-adjusted ground-based radar (WSR-88D) estimates obtained during nine years of observations. These results provide an overview of how well the satellite retrieved estimates—based on the new NASA TRMM radar rainfall products—compare to the ground-based estimates. These comparisons are part of a new framework for global verification of space-borne radar estimates of precipitation based on comparing pdfs of R. The framework demonstrates how a hydrologic approach that uses statistical properties of precipitation to estimate the uncertainties can be combined with a meteorological approach that uses physical properties of rainfall. The presentation provides insights into the uncertainties in space-based and ground-based radar estimates of rain rate distributions, and a discussion of opportunities and challenges to determine and reduce these uncertainties. This presentation combines results which are summarized in [1], [2], and [3]. Examples of comparison are provided in the following figures. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The exploitation of satellites for communication purposes has increased considerably during the last decades. The performance of satellite systems operating above 10 GHz essentially depends on the propagation characteristics of the transmission medium. A major hurdle in our efforts to go to higher frequencies in communications is the rain factor; this is especially true in satellite communications and for tropical latitudes where the rain rates are high. Presently in India an overwhelming segment of satellite telecommunications is through the 4GHz down link frequency from Indian geostationary satellites. There is compulsion to move up in frequencies beyond 10 GHz to take larger bandwidth and also much lower scintillation problem in the Ionosphere. However, this move to higher frequencies has to be constrained because of the tropospheric effects at higher frequencies caused primarily by rain attenuation and also to some extent by tropospheric scintillations and water varpour attenuation. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Radar Altimetry from space, primarily developed for making precise cm level measurements of ocean surface height, has proved to be a highly versatile technique in providing valuable information about other enclosed water bodies like lakes, oceanic and polar ice surfaces as well as the Earth’s ionosphere and the atmosphere. Sophisticated radar altimeters orbiting in space since 1992, make measurements of the pulse travel time, profile and energy backscattered from the ocean surface, simultaneously at two microwave frequencies. These pulse parameters are significantly affected by the presence of various ionospheric and atmospheric constituents, including the presence of rain in the propagation path. In this paper, we discuss the rain related effects on the radar altimeter measurements from space. Simultaneous availability of backscatter echo measurements at two widely separated frequencies in the C and Ku bands permit the estimation of rain induced attenuation of the microwave signal in its two-way journey through the raining column in the atmosphere. The application of differential C-Ku band attenuation in the development of algorithms for estimation over rainfall rate over the global oceans, pioneered by Bhandari and Varma (1995), is described and discussed. Over the last decade, the differential attenuation technique has been exploited extensively to map and study global oceanic rainfall in a comprehensive manner, based on dual frequency radar altimetric measurements from TOPEX/Poseidon, Jason and Envisat satellite missions. The paper would attempt to review the progress and accomplishments to date. Complementary and supplementary aspects of rainfall estimation from radar altimeters, in comparison to other space based methods, would also be highlighted. Attention would be focused on future radar altimeter missions addressing, in particular, the narrow-swath limitation of the present day radar altimeters. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Rainfall plays a vital role in Indian agriculture hence economy of the country, but very crucial and risky due to its erratic/ unpredictable behavior and uneven distribution. Since monsoonal vagaries in eastern India are very frequent hence involve a great risk in Argil. Production and quality of atmosphere at desired level. Though prediction of onset of monsoon with total quantum of rainfall is available through different agencies but still not accurate and not in consonance of observed behavior. Therefore, surface weather data of meteorological elements needs to be critically examined for prediction of onset of monsoon, rainfall rate and its variability with space and time and strategy to cope the uncertainty of risk (drought and flood etc) needs to be evolved. In the present study an analysis of rainfall of Eastern India (Eastern U.P., Bihar and Jharkhand) has been made for rainfall partitioning, rate of rainfall and its variation with space and time. A location specific six parameter model were developed with multiple correlation technique to predict the medium and long range rainfall forecast and found 65% accurate for long range and 79% accurate to medium range. This will not only help to predict the accurate rainfall but also provides a clue for assessment of quality of rainfall under different aerosol levels of atmosphere which ultimately led to link designers with radio wave propagation. In addition, correlation of physical variables of atmosphere like vapor pressure deficit, dew point and relative humidity were also made with quantum of rainfall, rate of rainfall and its quantitative characteristics in the study area as to understand the mechanism behavior of atmosphere for space research. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]