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A comparative analysis of open source data on the water spectral lines intensities in the frequency range from 0 to 1.75 THz was carried out. The analyzed data are significant for radiation propagation models. The calculations by the method of effective Hamiltonians and the variational method, as well as experimental data were taken into account. The uncertainty of intensity was found to be less than 2% for lines of the ground vibrational state with an intensity of more than 10−27 cm/molecule and about 5–10% for weaker lines. For strong (more than 10−26 cm/molecule) rotational lines of the ν2 state, the intensity uncertainty ranged from 2 to 5% and increased up to 5–10% for weak lines. For all rotational lines of the 2ν2, ν1, and ν3 states, the uncertainty was no more than 5–10%. The presented data show that most of the considered lines can be assigned a higher (by 1–2 steps according to the classification adopted in HITRAN) category of intensity accuracy. [ABSTRACT FROM AUTHOR]

Photoelectrons are produced on the dayside of Mars via solar Extreme Ultraviolet (EUV) and X‐ray ionization and are also frequently observed on the nightside as a result of field‐aligned transport. Based on the Solar Wind Electron Analyzer (SWEA) measurements made on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we show that the shape of the photoelectron energy distribution exhibits interesting cross‐terminator variations, in that the He II peak becomes less pronounced and the 10 − 50 eV smooth background becomes hardened, both more evident at lower altitudes. These observations could be understood as the outcome of "atmospheric absorption" via photoelectron collisions with ambient neutrals during day‐to‐night transport. Such a scenario could successfully interpret the diversity of the MAVEN SWEA observations such as the dawn‐dusk and north‐south asymmetries, the impacts of crustal magnetization, upstream solar wind conditions, and solar EUV and X‐ray radiation, all using the 10–50 eV spectral hardness as a diagnostic. In particular, the magnetic control of the cross‐terminator spectral reshaping is proposed as the outcome of varying day‐to‐night magnetic connectivity which naturally implies varying field‐aligned atmospheric column for "absorption." Crude estimates suggest that an "absorbing" atmospheric column of ≈1.5 × 1015 cm−2 is required for a significant photoelectron spectral reshaping beyond the EUV terminator. Therefore the observations reported here may shed light on the extension of the cross‐terminator magnetic field lines, as complementary to the day‐to‐night magnetic connectivity inferred from the occurrence of nightside photoelectrons. Plain Language Summary: Photoelectrons are an omnipresent population of the Martian ionosphere, which are produced exclusively on the dayside via photoionization and are also frequently observed on the nightside as a result of cross‐terminator transport. They are of broad interest because they make significant contributions to local ionization, heating, and airglow emission in the Martian upper atmosphere. In addition, the occurrence of nightside photoelectrons has been commonly used as a diagnostic of the day‐to‐night magnetic connectivity near Mars. Photoelectrons may also undergo significant spectral reshaping beyond the EUV terminator, an issue that has been paid little attention to but is potentially important for shedding light on the extension of the magnetic connectivity. This study is devoted to such a topic using SWEA measurements made on board the MAVEN spacecraft. We propose that collisions with atmospheric neutrals continuously modify the photoelectron energy distribution from a highly non‐thermal, structured one toward a thermal, featureless one. This scenario successfully interprets many aspects of the observed cross‐terminator variation, such as the dawn‐dusk and north‐south asymmetries, the impacts of crustal magnetization, upstream solar wind conditions, and solar activity. Key Points: The shape of the photoelectron energy distribution varies systematically across the Martian terminatorThe variation is the direct outcome of atmospheric absorption, which is more pronounced at low altitudesBoth crustal magnetization and upstream solar wind conditions affect the variation by modifying the field‐aligned atmospheric column [ABSTRACT FROM AUTHOR]

The first results of direct expedition measurements of atmospheric absorption of electromagnetic waves in the sub-terahertz frequency range of 0.1–1 THz, carried out in order to select an optimal site from the point of view of the microwave astroclimate for development of an observatory that can become an element of the radio interferometer of the Suffa observatory and, in the future, enter into collaboration with the Event horizon telescope (EHT), are presented in brief. The EHT, presenting an image of the shadow of a black hole, today consists of a dozen antennas located around the globe, and at present has no elements in its network in northern Eurasia. The studies performed may be useful not only for radio astronomy problems, but also for space communications, radar of the Moon, asteroids, and the detection of space debris objects. The first results of direct measurements of propagation of subterahertz waves at the selected sites confirmed the initial hypothesis of the expedition. This hypothesis was formulated on the basis of an analysis of meteorological data, as well as satellite data on atmospheric absorption in other ranges: optics and low-frequency radio bands. It was assumed that the work in the subterahertz frequency range in the eastern part of the northern Caucasus is more promising than in the western Caucasus. The western part is more attractive because today there are a number of observatories already operating, and the installation of one more antenna would have been much easier in terms of the necessary infrastructure and required highly qualified personnel. The hypothesis of the predominance of the eastern part was convincingly confirmed in the completed research by comparing the absorption in the 2- and 3-mm bands from the previously surveyed areas of the Western Caucasus (Terskol peak, Pastukhov mountain, KMO, BTA, RATAN-600 sites, etc.) with those studied during the expedition in 2021 for the Eastern sites on the Mayak (Gunib), Stolovaya, and Shalbuzdag mountains. Even measurements at the highest peak not only in the Western Caucasus, but also in Europe, at Mount Elbrus, carried out as part of this expedition, gave results worse than those in Dagestan and North Ossetia, confirming the futility of further search for a place for an effective subterahertz instrument in the eastern part of the North Caucasus. [ABSTRACT FROM AUTHOR]

We estimated the Korea Shortwave Radiation Budget (KSRB) providing new insights into the Korea climate system. Monthly averaged clear-sky, overcast-sky, and all-sky flux measurements with cloud amounts from 2000 to 2015 were used to assess the impacts of cloud on the KSRB. A deterministic model for shortwave radiation transfer was utilized with climatological data to compute the monthly mean of KSRB at the surface, in the atmosphere and at the top-of-atmosphere (TOA). For 10 Korean stations ranging from 33.5°N to 37.7°N, the daily mean of incoming solar flux at TOA is 345.2 Wm−2. 45.5% of that is transmitted to the surface, 25.0% is absorbed in the atmosphere and 29.5% is reflected directly back to space by the cloud, atmosphere and ground surface under all-sky conditions. Under clear- and overcast-sky conditions, 63.2% and 24.9% are transmitted to the surface, 17.8% and 37.1% are absorbed in the atmosphere, whereas 19.0% and 38.0% are reflected to space, respectively, showing a remarkably invariant value with respect to locations. Clouds in all- (or overcast-) sky atmosphere diminish surface solar irradiances (SSI) from 218.1 Wm−2 to 156.9 Wm−2 (or 85.8 Wm−2) and enhance atmospheric absorptions (AA) from 61.5 Wm−2 to 86.3 Wm−2 (or 128.2 Wm−2). Clouds also enhance the reflected irradiances (RI) at the TOA from 65.6 Wm−2 to 102.0 Wm−2 (or 131.2 Wm−2) for all- (or overcast-) skies. As a result, the all- (or overcast-) sky shortwave (SW) cloud forcing (CF) is −61.2 Wm−2 (or −132.3 Wm−2) at the surface, AA is 24.8 Wm−2 (or 66.7 Wm−2) in the atmosphere and RI is 36.4 Wm−2 (or 65.6 Wm−2) at the TOA, respectively. Consequently, it is found that the values for SW-CF at the surface is 1.7 times and 2.0 times greater than that at the TOA in the KSRB under all- and overcast-sky conditions, respectively. We have also compared the KSRB with the global shortwave radiation budget (GSRB) and discussed on the shortwave radiation budget. [ABSTRACT FROM AUTHOR]

Abstract We use global aerosol optical depth data from CALIOP with a radiation transfer model to investigate the aerosol direct radiative effect (DRE) and its sensitivity to the aerosol vertical resolution. Our study spans three years (2007–2009) and uses cloud data from ISCCP D2 to take into account cloud-aerosol radiative interactions on a monthly 2.5° × 2.5° resolution. The three-year global average all-sky aerosol DRE at the surface, in the atmosphere, and at the top of atmosphere (TOA) was calculated to be −4.23, 2.40, and −1.83 Wm−2, respectively. As expected, local DREs and atmospheric heating rates are shown to vary significantly. The largest magnitudes of the DREs are observed in regions with heavy aerosol load consisting of both natural and anthropogenic particles, such as desert dust, biomass burning and urban/industrial pollution. At TOA the aerosol effect is generally of negative sign, though a planetary heating effect is found in regions characterized by both absorbing aerosol and large surface albedo, such as deserts. Clouds scatter and absorb solar radiation, which generally decreases the aerosol cooling at the surface and the aerosol warming in the atmosphere. However, the latter effect is attenuated due to the enhancement of radiation absorption by the above-cloud aerosols. As a result, clouds decrease the aerosol TOA (planetary) cooling, and sometimes even cause aerosol warming (e.g. over the tropical South Atlantic). The cloud effect on the aerosol DRE depends strongly on the aerosol optical properties and the aerosol load fraction above low clouds. Comparing the effect of the observed aerosol vertical profile against an exponentially decreasing profile, we find a small sensitivity for the surface DRE, but larger for the atmospheric column and the top of the atmosphere. Under all-sky conditions, when continental aerosols are lifted higher in the atmosphere, the outgoing shortwave radiation at TOA decreases, due to the increase of UV and visible radiation absorption by particles while higher oceanic aerosols generally increase the outgoing shortwave radiation through more efficient backscatter and decrease of the NIR radiation absorption by atmospheric gases below aerosol particles. Highlights • A radiation transfer model produces the global aerosol direct radiative effect (DRE) from vertically resolved AOD from CALIOP • We present the 3-year DRE at the surface, in the atmosphere, and at the TOA, on a 2.5° × 2.5°, monthly resolution • We present global annual and seasonal DRE maps at the surface, at the TOA, in the atmosphere, as well as heating rates • We provide vertical profiles for both AOD and heating rates for 9 of the most aerosol-laden areas of the globe • The aerosol-cloud radiative interplay is examined and the significant effect of the above-cloud aerosols is studied • We investigate the DRE sensitivityby comparing exponentially decreasing with height profiles and the ones measured by CALIOP • The sensitivity of DRE to aerosol height is very different for the UV-Vis part of the spectrum compared to the NIR part [ABSTRACT FROM AUTHOR]

The amplitude and phase distortions of radar echo signal will cause the emergence of undesirable ghost scattering points, which degrade the quality of terahertz (THz) radar images. In this paper, a physics-based procedure is presented to predict the atmospheric attenuation and dispersion characteristics at THz frequencies, which is mainly based on the line-by-line calculation method with a specific modification in phase-shift prediction. The line-by-line parameters provided by the high-resolution transmission spectroscopic database and atmospheric condition parameters obtained from the Air Force Geophysics Laboratory reference atmospheric constituent profiles are adopted to predict the atmospheric transmittance and the phase shift for specific transfer paths. The results are compared with measured data to demonstrate the accuracy, while the proposed procedure is used to analyze the impacts of atmospheric transfer characteristics on radar imaging via the high-resolution range profile simulation. The signal distortion is interpreted in terms of paired echoes to illustrate the importance of frequency band selection for high-resolution imagery at THz frequencies. [ABSTRACT FROM AUTHOR]

Highlights • Three band pass filters are used to quickly estimate the oxygen band-average transmission near 762 nm. • Three-channel structure capturing bandpass signals simultaneously eliminates variation effect of intensity and turbulence. • A transmission model is established based on line-by-line algorithm to derive path length from band-average transmission. Abstract A three-channel filter-based non-imaging passive ranging system based on oxygen absorption is proposed and demonstrated. This system utilizes three band pass filters to quickly estimate the oxygen band-average transmission near 762 nm, and uses three simultaneous spectral measurement channels which are defined by the different band pass filters to capture the three band pass signals of the target. A short range experiment from 100 m to 300 m and a long range experiment at 1945 m are conducted with a 1000 W halogen lamp, and the measured band-average oxygen transmission of the both experiments are compared to the predicted curve derived from the line-by-line transmission model to estimate the range. Averaged range error of 2.14% is achieved in the short range experiment and range error of 6.72% is obtained in the long range experiment. [ABSTRACT FROM AUTHOR]

Spectroscopic information on atmospheric gases, such as absorption line positions, intensities and widths, is important for radiative transfer calculations in climate and weather models. The widely used HIgh resolution TRANsmission (HITRAN) spectroscopic database is updated regularly. A line‐by‐line radiative transfer model has been used to investigate the impacts of the updates of HITRAN from 2008 to 2016 on clear‐sky calculations of absorption and solar heating rates in the near‐infrared region from 4,000 to 10,000 cm−1 (1.0–2.5 µm). These calculations were carried out for the tropical and sub‐arctic atmospheres at solar zenith angles of 30° and 75° using HITRAN absorption line parameters for H2O, CO2, O3, N2O, CO, CH4 and O2 as well as the MT_CKD 2.5 (Mlawer‐Tobin‐Clough‐Kneizys‐Davies) continua for H2O, CO2, O3 and O2. It was found that the improvements in HITRAN absorption line parameters led to modest increases in the spectrally integrated absorbed downward solar fluxes and heating rates. The differences in absorbed fluxes are larger between HITRAN2016 and HITRAN2008 (maximum difference ∼1.3%) than between HITRAN2016 and HITRAN2012 (largest difference ∼0.3%). The corresponding maximum differences in heating rates are less than 2%. In order to improve accuracy, HITRAN2016 should be used in preference to earlier line‐lists for calculating near‐infrared absorbed solar fluxes and heating rates; but for calculations of clear‐sky heating rates in the near‐infrared region that do not require better than 2% accuracy, line parameters from HITRAN2012 and HITRAN2008 may still be used. Although the revisions of HITRAN led to relatively small differences in the spectrally integrated quantities, the improved quality of near‐infrared line parameters will have a significant impact on other atmospheric applications such as the measurements of CO2 concentrations at a precision of less than 1% in Greenhouse Gases Observatory Satellite (GOSAT) and Orbiting Carbon Observatory‐2 (OCO‐2) missions. [ABSTRACT FROM AUTHOR]

Highlights • Reconciliation of ozone microwave data in the HIRAN and JPL databases. • Explanation of theory for centrifugal distortion of permanent dipole. • Far-infrared absolute intensity measurement. • Impact of intensity adjustment for ozone remote sensing. Abstract This note provides a citable reference to a database reconciliation effort for ozone pure rotational intensities. The permanent dipole moment and theoretical adjustments for centrifugal distortion are utilized in a predictive calculation that is compared to experimental measurements. This prediction has been available in the JPL spectral line catalog since 2005, but has been at odds with the HITRAN database, which was originally based on an atlas provided by Flaud (HITRAN 1992) and subsequently scaled by 4% (HITRAN 2004). Using a modified partition function and isotopic abundance factor, the JPL 2005 prediction has now been utilized to create a self-consistent entry as an interim update to the HITRAN2016 database. Ramifications of the intensity change for users of HITRAN versions 2004–2012 are discussed. New pure rotational intensity measurements were carried out supporting the validity of the JPL 2005 database. [ABSTRACT FROM AUTHOR]

Flame temperature, which is an important parameter in combustion diagnostics, provides a better understanding of flame radiative characteristics and can be deduced from the flame emission spectrum. However, in a combustion process with a large-scale flame that requires field measurement, considerable attenuation of the signature from the flame source occurs owing to the absorption of cold molecules in the atmosphere, which produces uncertainties while estimating the flame temperature. We analyze the effect of atmospheric absorption on the flame temperature estimation uncertainty with the optical emission spectroscopic method. We determine the flame temperature of IR (infrared) countermeasure flare combustion by fitting the reference spectrum model applying atmospheric absorption and without applying atmospheric absorption. Line-by-line modeling is conducted using a high-temperature molecular spectroscopic database. The instrument function of the spectrometer is applied, and the atmospheric transmission information is obtained by using the moderate-resolution atmospheric transmission database. In addition, we calculate the estimated flame temperature uncertainty without applying atmospheric absorption when the atmospheric path length, molecular concentration, and flame temperature are varied. Through the analysis, we suggest the wavelength range where the atmospheric absorption is negligible so that the uncertainty is minimized without applying it. Finally, we determine the flame temperature of the IR flare detected with an absolutely calibrated radiometric spectrometer by considering atmospheric absorption. All the fitting results show good agreement with experimental data. [ABSTRACT FROM AUTHOR]

Abstract: In the near infrared (near IR), differences in both the absolute level and spectral resolution of available observation‐based solar spectral irradiances (SSI) are very significant. In this paper, a very high‐resolution line‐by‐line radiative transfer model has been used to investigate the effect of the differences in the absolute level of SSI on the clear‐sky total absorbed solar irradiance and solar heating rates in the near IR from 4,000 to 10,000 cm−1 (2.5–1 μm), for a midlatitude summer atmosphere. Absorption calculated using observed SSI from the surface, aircraft, and satellite are between 2 and 8% lower than that for the widely used ATmospheric Laboratory for Applications and Science (ATLAS) 3 spectrum. Tropospheric and stratospheric heating rates produce by these spectra are also lower than that produced by the ATLAS 3 spectrum by about 3–9% and 4–11%, respectively. However, there is a closer agreement between near IR absorbed irradiances and heating rates computed using two most recent observed spectra. That notwithstanding, it is recommended that the uncertainty in the choice of the SSI in near IR radiative transfer modeling should be quantified. [ABSTRACT FROM AUTHOR]

The IR absorption spectra of pure carbon dioxide in the region of the forbidden ν 2  + ν 3 vibrational transition at 3004 cm −1 have been recorded using a Fourier-transform spectrometer. A multipass-optical cell with the path length of 100 m was used in the study. The data were taken at room temperature of 294.8 K with a resolution of 0.02 cm −1 over the spectral region 2500–3500 cm −1 . A sample pressures varied from 207 to 463 kPa (2.04–4.57 atm). The measured binary absorption coefficients provide the band integrated intensity value of (2.39 ± 0.04) ∗ 10 −4  cm −2  amagat −2 . The result is compared with those from previous works. The observed band profile features are discussed. [ABSTRACT FROM AUTHOR]

This manuscript reports an effort to improve the absolute accuracy of ozone intensities in the 10 µm region via a transfer of the precision of the rotational dipole moment onto the infrared measurement. The approach determines the ozone mixing ratio through alternately measuring seven pure rotation ozone lines from 692 to 779 GHz. A multispectrum fitting technique was employed. The results determine the column with absolute accuracy of 1.5% and the intensities of infrared transitions measured at this accuracy reproduce the recommended values to within a standard deviation of 2.8%. [ABSTRACT FROM AUTHOR]

The objective of the present work is to compare the projections of surface solar radiation (SSR) simulated by four regional climate models (CCLM, RCA4, WRF, ALADIN) with the respective fields of their ten driving CMIP5 global climate models. First the annual and seasonal SSR changes are examined in the regional and in the global climate models based on the RCP8.5 emission scenarios. The results show significant discrepancies between the projected SSR, the multi-model mean of RCMs indicates a decrease in SSR of −0.60 W/m per decade over Europe, while the multi-model mean of the associated GCMs used to drive the RCMs gives an increase in SSR of +0.39 W/m per decade for the period of 2006-2100 over Europe. At seasonal scale the largest differences appear in spring and summer. The different signs of SSR projected changes can be interpreted as the consequence of the different behavior of cloud cover in global and regional climate models. Cloudiness shows a significant decline in GCMs with −0.24% per decade which explains the extra income in SSR, while in case of the regional models no significant changes in cloudiness can be detected. The reduction of SSR in RCMs can be attributed to increasing atmospheric absorption in line with the increase of water vapor content. Both global and regional models overestimate SSR in absolute terms as compared to surface observations, in line with an underestimation of cloud cover. Regional models further have difficulties to adequately reproduce the observed trends in SSR over the past decades. [ABSTRACT FROM AUTHOR]

The intensity of the atmospheric diagnostic fine-structure line of the O 2 molecule at 118.75 GHz is revised based on multiple measurements with a resonator spectrometer in pure O 2 and O 2 –N 2 mixture at pressures ranging from 250 to 1500 Torr and temperatures within 278–327 K. The resulting intensity of 1.000(3) ⋅ 1 0 − 25 cm/molec confirms the earlier measurements and allows decreasing the uncertainty down to ∼ 0.3%. An excellent agreement with the result of calculations presented in HITRAN is demonstrated, suggesting that the 10%–20% uncertainty recommended by the database for all fine structure lines is too large. [Display omitted] • Revision of the intensity of the O 2 molecule line at 118 GHz is carried out. • Experimental data acquired at temperatures 278–327 K are analyzed. • Resulting value 1.000(3)*10−25 cm/mol agrees with databases and earlier measurements. [ABSTRACT FROM AUTHOR]

O segundo satélite da Missão Espacial Completa Brasileira (SCD2/MECB) foi colocado em órbita em 23 de Outubro de 1998 e carrega a bordo um experimento de células solares. Célula solar de silício é um dispositivo semicondutor, que pode medir a intensidade da radiação visível e parte da radiação infravermelha (400-1100 nm). O experimento permite medir simultaneamente a insolação direta e parte da radiação solar que é refletida pela Terra para o espaço. Os dados do experimento célula solar são transmitidos em tempo real pela telemetria do satélite e recebidos pela estação terrestre em Cuiabá, MT-Brasil (16°S; 56°W). Este fato limita a cobertura espacial para um círculo sobre a América do Sul. O albedo planetário é obtido dentro desta cobertura e seus valores podem ser agrupados em períodos temporais (anual, sazonal ou mensal), ou podem ser estudados para várias localizações (latitude e longitude) durante a vida do satélite. O coeficiente de transmissão atmosférica ou índice de claridade (Kt), medido em estações meteorológicas na superfície da Terra, junto com o valor medido simultaneamente do albedo planetário, permite calcular o coeficiente de absorção atmosférica (Ka). O método desenvolvido neste trabalho para avaliar Ka considera que o albedo planetário é composto por duas partes: uma refletividade local e uma refletividade não local. Considerando este novo conceito, é definida uma taxa de absorção atmosférica (denominada Ra) que é a razão entre Ka e a potência de irradiância solar líquida, que não atravessou a atmosfera (100%-Kt). A taxa de absorção atmosférica assim definida é independente da cobertura de nuvens. O histograma de freqüência de Ra mostra os valores de 0,86±0,07 e 0,88±0,09 sobre as cidades de Botucatu-SP e do Rio de Janeiro-RJ, durante os anos de 1999 até 2006, respectivamente.The second satellite of the Brazilian Complete Space Mission (SCD2/MECB) was launched on October 23, 1998 and it hosts on board a solar cell experiment. Silicon solar cell is a semiconductor device that senses visible and near infrared (400-1100 nm) radiations. The experiment permits the simultaneous inference of direct insolation and the insolation that is reflected outside of Earth. The data of the solar cell experiment are transmitted in real time by the satellite telemetry and are received by the ground station of Cuiabá, MT-Brazil (16°S, 56°W). This fact limits their spatial coverage to a circle on the South America. The planetary albedo is obtained inside this coverage area and the data can be grouped into periods of time (annual, seasonal or monthly) or studied for several places (latitude and longitude) during the life of the satellite. Atmospheric transmission coefficient or clearness index (Kt), measured at meteorological stations around the Earth surface, together with simultaneous measured of the planetary albedo permits to calculate the atmospheric absorption coefficient (Ka). The developed method in this work for evaluating the Ka considers that the planetary albedo is composed by two parts: the local and the non local reflectivity. Considering this new concept, an atmospheric absorption ratio (called here Ra) is defined as the quotient between Ka and the net solar irradiance power that is not transmitted through the atmosphere (100%-Kt). The atmospheric absorption ratio defined by this way is not cloud cover dependent. The frequency histogram of Ra indicates the values of 0.86±0.07 and 0.88±0.09 on the cities of Botucatu-SP and Rio de Janeiro-RJ respectively, during the years of 1999 to 2006.

• The first study of the effect of temperature on the speed-dependence effect for oxygen fine-structure lines. • Significantly different temperature behavior of pressure broadening γ 0 and its speed-dependence γ 2 for different N. • Change of the sign of temperature exponent of γ 2. • Accurate parameters of the line center pressure shifting. The microwave spectrum of oxygen, which consists of the fine-structure lines, is a tool for atmospheric research. An accurate line shape profile is necessary for modeling of the atmospheric absorption and interpreting the radiometric data. In this study, more than 500 recordings of the oxygen millimeter wave lines were obtained in a wide range of pressures (0.3–1500 Torr) and temperatures (235–357 K) using two experimental techniques that differ in principle of operation. High quality of the experimental spectra and negligible baseline allowed accurate analysis of the line shape using the quadratic speed-dependent Voigt profile. Line shape parameters for six fine-structure oxygen lines (N = 1+,1−, 7+, 11+, 15+, and 19−), including self-broadening and self-shifting, were refined. The parameters of the speed dependence of the collision relaxation rate demonstrated significantly different temperature behavior for different rotational states. In particular, the ratio γ 2 /γ 0 reveals temperature independence for the lowest rotational state; the dependence becomes notable with the growth of rotational excitation. For practical use, the empirical functions were fitted to the experimental temperature and rotational dependences of the line shape parameters. [ABSTRACT FROM AUTHOR]

Retrievals of atmospheric composition from near-infrared measurements require measurements of airmass to better than the desired precision of the composition. The oxygen bands are obvious choices to quantify airmass since the mixing ratio of oxygen is fixed over the full range of atmospheric conditions. The OCO-2 mission is currently retrieving carbon dioxide concentration using the oxygen A-band for airmass normalization. The 0.25% accuracy desired for the carbon dioxide concentration has pushed the required state-of-the-art for oxygen spectroscopy. To measure O 2 A-band cross-sections with such accuracy through the full range of atmospheric pressure requires a sophisticated line-shape model (Rautian or Speed-Dependent Voigt) with line mixing (LM) and collision induced absorption (CIA). Models of each of these phenomena exist, however, this work presents an integrated self-consistent model developed to ensure the best accuracy. It is also important to consider multiple sources of spectroscopic data for such a study in order to improve the dynamic range of the model and to minimize effects of instrumentation and associated systematic errors. The techniques of Fourier Transform Spectroscopy (FTS) and Cavity Ring-Down Spectroscopy (CRDS) allow complimentary information for such an analysis. We utilize multispectrum fitting software to generate a comprehensive new database with improved accuracy based on these datasets. The extensive information will be made available as a multi-dimensional cross-section (ABSCO) table and the parameterization will be offered for inclusion in the HITRANonline database. [ABSTRACT FROM AUTHOR]

The IR spectra of water vapor–carbon dioxide mixtures as well as the spectra of pure gas samples have been recorded using a Fourier-transform infrared spectrometer at a resolution of 0.1 cm −1 in order to explore the effect of colliding CO 2 and H 2 O molecules on their continuum absorptions. The sample temperatures were 294, 311, 325 and 339 K. Measurements have been conducted at several different water vapor partial pressures depending on the cell temperature. Carbon dioxide pressures were kept close to the three values of 103, 207 and 311 kPa (1.02, 2.04 and 3.07 atm). The path length used in the study was 100 m. It was established that, in the region around 1100 cm −1 , the continuum absorption coefficient C H 2 O + C O 2 is about 20 times stronger than the water–nitrogen continuum absorption coefficient C H 2 O + N 2 . On the other hand, in the far wing region (2500 cm −1 ) of the ν 3 CO 2 fundamental band, the binary absorption coefficient C C O 2 + H 2 O appears to be about one order of magnitude stronger than the absorption coefficient C C O 2 + C O 2 in pure carbon dioxide. The continuum interpretation and the main problem of molecular band shape formation are discussed in light of these experimental facts. [ABSTRACT FROM AUTHOR]

Mid-infrared atmospheric absorption bands centered at 4.3 \mu\mboxm are applied in target detection. Image simulation, as an important tool for the adaption and optimization of a sensor, ought to be conducted for the development of instruments using this spectral range. In this paper, a top-of-atmosphere (TOA) image simulation method is proposed, and this method is tested on two bands of the sensor SPIRIT III (band S1: 4.21–4.37 \mu\mboxm, S2: 4.23–4.47 \mu\mboxm). Band translation models are established for the generation of surface emissivity images, and an analytic radiative transfer model is modified and utilized to simulate TOA radiance fast and accurately. Accuracy analysis of the proposed method shows relative errors of within $\pm$6% and $\pm$1% in simulated surface emissivity and TOA radiance, respectively. Moreover, image simulation is often used for band selection in the sensor design stage. To illustrate how our proposed simulation method was applied in band selection, we used simulated TOA radiance of bands S1 and S2 as an example and compared their possibility of false alarms caused by high-temperature objects. Experimental results show that high-temperature objects are more unlikely to become false alarms on band-S1 images. Therefore, the spectral range of S1 is a better option for target detection application than S2. This TOA simulation method can be also applied in band selection among other 4.3- \mu\mboxm absorption bandwidths, as was done in this paper. [ABSTRACT FROM AUTHOR]

Direct measurement of depth of the ~ 1900 nm feature (F 1900 ) caused by molecular water is not possible from hyperspectral data acquired under natural illumination. Proxy measures for depth were evaluated to estimate the true depth of F 1900 from such data. Suitable proxy measures were identified using data acquired by a high-resolution spectrometer (under artificial and natural illumination) and by a hyperspectral imaging sensor (under artificial illumination), with different amounts of simulated atmospheric noise. The best performing proxy measures were used to estimate depth from hyperspectral imagery acquired in the field under natural illumination. Proxy measures comprised a ratio of reflectance, continuum-removed depth at a single wavelength and continuum-removed depth integrated over several wavelengths. For high resolution spectra, a ratio of reflectance at 2017 nm and 1967 nm (Ratio 2017/1967 ) and the continuum-removed depth at 1967 nm (CRD 1967 ) were strongly correlated with depth R 2 = 0.98–0.99 and R 2 = 0.95–0.96, respectively. For hyperspectral imagery acquired in the laboratory, Ratio 2017/1967 and CRD 1967 were strongly correlated with depth across all levels of atmospheric noise (R 2 = 0.94–0.98 and 0.94–0.97, respectively). Proxy measures using integrated depth performed relatively poorly (R 2 = 0.65–0.86). In independent tests, depth of F 1900 was consistently overestimated by CRD 1967 but not by Ratio 2017/1967 . Validation of field imagery was done by comparing depth predicted by the proxy measures with depth measured from laboratory imagery of collocated samples from the field. Ratio 2017/1967 derived from a polynomial fit to the data between 1961 and 2134 nm (RatioP 2017/1967 ) most closely approximated measured depth. Ratio 2017/1967 , derived from the original data either under or overestimated depth. Measures of continuum-removed depth generated from the original data (CRD 1967 ) and from a polynomial fit to the original data (CRDP 1967 ) overestimated the depth of F 1900 . This study showed that the depth of F 1900 can be predicted from data acquired under natural illumination however, the choice of proxy measure can have a significant impact upon quantitative estimates. [ABSTRACT FROM AUTHOR]

It is commonly accepted that an important role of the phytochrome lies in signalling the proximity of competing plants. However, not all photoresponses conveyed by the phytochrome can be explained by the competition only. Because a better description of the natural variability of solar spectral irradiance is necessary to recognize the other roles of the phytochrome, long-lasting spectroradiometric measurements have been performed. Special attention has been paid to the relations between the far-red and red bands of the solar spectrum, which have an impact on the phytochrome. The effect of atmospheric moisture on far-red irradiance (attenuated in the 720 nm band of water vapour absorption) is described. The far-red irradiance, active in the 'high irradiance response' of the phytochrome, and the red/far-red ratio, important for the 'low fluence response', may vary very strongly relative to the atmospheric moisture. Together with other facts known from photophysiology, the results of the measurements enabled us to formulate a thesis that the phytochrome monitors the amount of water vapour and opens appropriate metabolic pathways to cope with the danger of drought. The recognition of this novel role of the phytochrome might broaden the knowledge in the area of plant photomorphogenesis and ecology. [ABSTRACT FROM AUTHOR]

The airborne prism experiment (APEX) is an imaging spectrometer developed by a joint Swiss–Belgian consortium composed of institutes (University of Zurich, Flemish Institute for Technological Research) and industries (RUAG, OIP, Netcetera), supported by the European Space Agency's PRODEX programme. APEX is designed to support the development of future space-borne Earth observation systems by simulating, calibrating or validating existing or planned optical satellite missions. Therefore, periodic extensive calibration of APEX is one major objective within the project. APEX calibration under laboratory conditions is done at its dedicated calibration and characterization facility at the German Aerospace Center (DLR) in Oberpfaffenhofen, Germany. While environmental influences under laboratory conditions are reduced to a minimum, the effects of atmospheric absorption and the properties of the underlying calibration infrastructure may still influence the measurements and subsequently the accuracy of the sensor spectral response estimations. It is demonstrated that even a lightpath of ∼2 m through the atmosphere or the monochromator grating can have significant impact on the spectral response estimation of the sensor. A normalization approach described in this letter is able to compensate for these effects. The correction algorithm is exemplarily demonstrated on actual measurements for the short wavelength-IR range channel. [ABSTRACT FROM PUBLISHER]