Search results for "scattering"
showing 10 items of 8332 documents
The effects of different radiation parametrizations on cloud evolution
1997
With the use of the microphysical stratus model (MISTRA), investigations into the effects of variations in the radiative-transfer parametrizations on cloud development have been undertaken. Two radiative-transfer schemes were coupled with the microphysical-thermodynamical section of MISTRA, one based on the exponential sumfitting method and the other based on the correlated k-distribution method of determining gaseous absorption properties. Model runs were initiated with parameter values in accordance with measurements made over the North Sea and comparisons made between model runs where only the radiation schemes were altered. Results indicated that differences between the two schemes had …
On the direct and semidirect effects of Saharan dust over Europe: A modeling study
2007
[1] On the basis of a new regional dust model system, the sensitivity of radiative forcing to dust aerosol properties and the impact on atmospheric dynamics were investigated. Uncertainties in optical properties were related to uncertainties in the complex spectral refractive index of mineral dust. The climatological-based distribution of desert-type aerosol in the radiation scheme of the nonhydrostatic regional model LM was replaced by dust optical properties from spectral refractive indices, derived from in situ measurements, remote sensing, bulk measurements, and laboratory experiments, employing Mie theory. The model computes changes in the solar and terrestrial irradiance from a spatia…
Comparison of AERONET and SKYRAD4.2 inversion products retrieved from a Cimel CE318 sunphotometer
2012
SKYNET is an international research network of ground based sky – sunphotometers for the observation and monitoring of columnar aerosol properties. The algorithm developed by SKYNET is called SKYRAD.pack, and it is used on Prede instruments only. In this study, we have modified the SKYRAD.pack software in order to adapt it to Cimel sunphotometers. A one month database of Cimel data obtained at Burjassot (Valencia, Spain) has been processed with this program and the obtained inversion products have been compared with AERONET retrievals. In general, the differences found were consistent with the individual error assessments for both algorithms. Although the aerosol optical depth com…
A study on the sensitivities of simulated aerosol optical properties to composition and size distribution using airborne measurements
2014
We present a flexible framework to calculate the optical properties of atmospheric aerosols at a given relative humidity based on their composition and size distribution. The similarity of this framework to climate model parameterisations allows rapid and extensive sensitivity tests of the impact of uncertainties in data or of new measurements on climate relevant aerosol properties. The data collected by the FAAM BAe-146 aircraft during the EUCAARI-LONGREX and VOCALS-REx campaigns have been used in a closure study to analyse the agreement between calculated and measured aerosol optical properties for two very different aerosol types. The agreement achieved for the EUCAARI-LONGREX flights is…
Overview of aerosol properties associated with air masses sampled by the ATR-42 during the EUCAARI campaign (2008)
2013
Abstract. Within the frame of the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project the Météo-France aircraft ATR-42 performed 22 research flights, over central Europe and the North Sea during the intensive observation period in May 2008. For the campaign, the ATR-42 was equipped in order to study aerosol physical, chemical and optical properties, as well as cloud microphysics. During the campaign, continental air masses from Eastern and Western Europe were encountered, along with polar and Scandinavian air masses. For the 22 research flights, retroplume analyses along the flight tracks were performed with FLEXPART in order to classify air masses into five sector…
Spectral Observations of Optical Emissions Associated with Terrestrial Gamma-Ray Flashes
2021
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Wavelength dependence of the effective cloud optical depth
2015
This study examines the wavelength dependence of cloud optical depth. To accomplish this task two different wavelength bands of the solar spectrum were considered in the cloud optical depth retrieval which was conducted in Valencia, Spain. The first retrieval used global irradiance measurements in the UVER range taken from a YES-UVB-1 radiometer in combination with multiple scattering model estimates; while the second retrieval was obtained in the Broadband range, with measurements of global solar surface irradiance from a CM6 pyranometer and a multiple scattering model. Whilst the dependence of the cloud optical depth (τ) on the wavelength is small, the best result was displayed by the SBD…
Effective cloud optical depth for overcast conditions determined with a UV radiometers
2014
Using a sky camera, episodes characterized by overcast low clouds in the Valencia region of Spain have been selected for analysis. One year of cloud optical depth data have been produced by inverting UV erythemal irradiance measured with a UVB-1 radiometer from Yankee Environmental Systems using the LibRadtran radiative transfer model. Measurement uncertainties, aerosol single scattering albedo and cloud properties are, in order of decreasing importance, the most important factors influencing the accuracy of cloud optical depth retrieval when using UV erythemal radiometers. Statistics for cloud optical depth show a highly skewed frequency distribution best described by a gamma distribution …
Incorporation of aerosol effects in a clear-sky semi-empirical model of UVER radiation for Valencia, Spain
2011
The study develops a simple but physically based model for estimating erythemal irradiance [(UV erythemal radiation (UVER)] for cloudless urban regions with substantial aerosol load, such as that of the Valencia environment in Spain. The model estimates direct and diffuse UVER for cloudless aerosol-free conditions using the LibRadtran model with a DISORT algorithm. Aerosol optical thickness for UVER (τaER) is obtained as a residual term by comparing measured direct UVER against modelled direct UVER in the absence of aerosol load. On average, τaER is 18% higher than τ data extrapolated to 305 nm using the CIMEL CE-318. Comparison of measured direct and diffuse UVER with model estimates provi…
Sensitivity of the atmospheric temperature profile to the aerosol absorption in the presence of dust
2014
Abstract Radiative transfer simulations in the shortwave (SW) and longwave (LW) spectral regions have been carried out to investigate the time evolution of the atmospheric heating/cooling rates and their influence on the temperature profiles under different vertical distributions of the aerosol absorption. The case study is based on measurements made at Rome, Italy, on 20 June 2007, when a dust layer was present above the urban boundary layer (BL) and the column aerosol optical depth at 550 nm was about 0.37. Column-integrated aerosol optical depth and single scattering albedo, as well as vertical profiles of aerosol extinction and meteorological variables have been derived from observation…