Improved algorithm for calculations of Rayleigh-scattering optical depth in standard atmospheres (original) (raw)

A General Model of the Atmospheric Scattering in the Wavelength Interval 300 - 1100nm

2009

We have presented and developed new theoreticempirical models of the extinction coefficients of the molecular scattering in the lower, close to the ground troposphere. We have included the indicatrices of backscattering. The models have been presented using general analytical functions valid for the whole wavelength interval 300-1100 nm and for the whole interval of visibility from 0.1 km up to 50 km. The results have been compared in quantity with the model and experimental data of other authors. The modeling of troposphere scattering is necessary for the analysis and design of all optoelectronic free space systems: atmospheric optical communication systems, location systems for atmospheric research (LIDAR), optical radiometric systems.

Aerosol optical depth over the oceans: Analysis in terms of synoptic air mass types

Journal of Geophysical Research, 1995

The results of spectral aerosol optical depth measurements in the Pacific Ocean, Baltic Sea, and North Atlantic are considered with regard to air mass types. It is found that the optical properties of continental and maritime air mass types differ significantly for the data employed in this study. A synoptical air mass context was also employed in demonstrating the correlation between near infrared aerosol optical depth Xa(1640 nm) and wind speed as well as for investigations into the relationship between deck level relative humidity and the aerosol optical depth at 550 nm. Simulations, employing well-known aerosol parameterization models, of the aerosol optical depth spectra for various air mass types show good agreement with the experimental results in the visible and near infrared range. Introduction Comprehensive studies wherein one investigates the spatial and temporal links between optical depth variations and synoptic air mass parameters over the oceans is of great importance if we are to understand the mechanisms which define the optical state of the atmosphere. The results of these investigations are of interest in pure atmospheric optics as well as to such disciplines as remote sensing where the atmospheric optical state is an essential element in the radiometric calibration procedure of surface images. Spatial and temporal information extracted from aerosol optical measurements is required in radiative climatological applications such as those which focus on the refinement of general circulation models. Relationships between air mass type and its optical characteristics in a maritime atmosphere have been studied by a number of researchers [

Atmospheric Optical Propagation

2008

The Atmospheric Optical Propagation project is developing a suite of accurate models for optical propagation in the marine atmospheric boundary layer. Our objective is to provide an atmospheric effects characterization package for existing and emerging Navy applications.

The relationship between atmospheric light scattering coefficient and visibility

Atmospheric Environment (1967), 1969

Ahatraet-Koschmieder's formula relating visibility to the extinction coefiicient (L, = 3.9/b) has bayl veri6ed by comparing simultaneous measurements of both variables at one site. These data suegest that the meteorological e determined Corn a point measurement of the scattering coe&ient with an integrating nephelometer, is approximately equal to the prevailing visibility determined by an observer looking at prominent dark objects. The quantitative r~ti~p between visibility, total atmospheric scattering coefBcient, and aerosol mass concentration is presented and compared with the ciassical theoretical relationship,

Aerosol light-scattering enhancement due to water uptake during the TCAP campaign

2014

Aerosol optical properties were measured by the DOE/ARM (US Department of Energy Atmospheric Radiation Measurements) Program Mobile Facility during the Two-Column Aerosol Project (TCAP) campaign deployed at Cape Cod, Massachusetts, for a 1-year period (from summer 2012 to summer 2013). Measured optical properties included aerosol light-absorption coefficient (σ ap) at low relative humidity (RH) and aerosol light-scattering coefficient (σ sp) at low and at RH values varying from 30 to 85 %, approximately. Calculated variables included the single scattering albedo (SSA), the scattering Ångström exponent (SAE) and the scattering enhancement factor (f (RH)). Over the period of measurement, f (RH = 80 %) had a mean value of 1.9 ± 0.3 and 1.8 ± 0.4 in the PM 10 and PM 1 fractions, respectively. Higher f (RH = 80 %) values were observed for wind directions from 0 to 180 • (marine sector) together with high SSA and low SAE values. The wind sector from 225 to 315 • was identified as an anthropogenically influenced sector, and it was characterized by smaller, darker and less hygroscopic aerosols. For the marine sector, f (RH = 80 %) was 2.2 compared with a value of 1.8 obtained for the anthropogenically influenced sector. The air-mass backward trajectory analysis agreed well with the wind sector analysis. It shows low cluster to cluster variability except for air masses coming from the Atlantic Ocean that showed higher hygroscopicity. Knowledge of the effect of RH on aerosol optical properties is of great importance for climate forcing calculations and for comparison of in situ measurements with satellite and remote sensing retrievals. In this sense, predic-tive capability of f (RH) for use in climate models would be enhanced if other aerosol parameters could be used as proxies to estimate hygroscopic growth. Toward this goal, we propose an exponential equation that successfully estimates aerosol hygroscopicity as a function of SSA at Cape Cod. Further work is needed to determine if the equation obtained is valid in other environments.

Reconstruction of the Scattering Coefficient in the Lower Troposphere Using Ground-Based Measurements

Journal of the Atmospheric Sciences, 2002

The model proposed provides for reconstruction of the aerosol scattering coefficient profile. In so doing one needs for, as input data, the scattering coefficient value of the dry aerosol substance at the near ground level measured at the wavelength of 0.52 µm, relative air humidity, aerosol optical thickness, and mean temperature of air in the low troposphere. The model assumes the account for correlation between the values of scattering coefficient at different altitudes, as well as the dependence of the height of mixing layer on the heating of the lower atmospheric layers. The errors in reconstructing the vertical profiles of the aerosol scattering coefficient are analyzed for different ways of taking into account the external factors and input parameters. It is shown that the use of such an approach provides a decrease in the rms error in reconstruction even at this stage approximately by 30% for winter and by 3 to 4 times for summer in comparison with the rms deviation of this parameter in the initial data sets.