Validation of FASE (FASCODE for the Environment) and MODTRAN3: updates and comparisons with clear-sky measurements

Abstract

FASE is a line-by-line (LBL) atmospheric radiation code, grounded in the original USAF FASCODE (Fast Atmospheric Signature Code) line shape decomposition algorithm. The Department of Energy Atmospheric Radiation Measurement (ARM) Program and the AF/PL Geophysics Directorate jointly supported FASE which now envelops both agencies' important upgrades. ARM's LBLRTM (LBL Radiative Transfer Model authored by S.A. Clough and P.D. Brown of AER, Inc.) expanded the FASCODE algorithms to specifically address scientific and coding issues of particular concern to the climate community including: H20 and C02 continua, lineshape, radiance algorithms, sampling, vectorization, array parameterization, spectral ranges and inputloutput modes. These features have then been recombined with FASCODE non-LTE and laser options, plus shared common elements from MODTRAN (Moderate Resolution Transmittance Model, a 2 cm-band model) evolution. These include a new solar irradiance and UV cross sections. Examples of the feedback and validation between FASE and MODTRAN3 will be presented. INTRODUCTIONThe prime focus of the FASCODE for the Environment (FASE) program is to make available to the atmospheric spectroscopy community the results of on-going work sponsored by the ARM program, Department of Energy (DOE), and the Air Force Phillips Laboratory, Department of Defense (DoD). The goal of the program is to create an atmospheric radiance and transmittance model which is user-friendly and contains the latest atmospheric physics. In addition, advances from the wider radiative transfer community will be incorporated where appropriate within program constraints and resources.The origins ofFASE lie in FASCOD1B, a line-by-line code where the Voigt function has been decomposed into four primary functions to account for the Lorentz and Doppler components1 as well as associated wing continua. This rapid line-by-line code was developed by Clough and Kneizys2 and evolved into FASCOD3P (preliminary)3. DOE initiated separate funding of the FASCOD3P algorithm in 1990, leading to the Line-by-Line Radiative Transfer Model (LBLRTM)4 with major new contributions. The basic approach to developing FASE is severalfold: (1) to modify the overall program structure of FASCODE ILBLRTM so as to improve the flexibility and maintainability of the code without significant re-coding; (2) to incorporate a number of coding improvements (also to benefit the flexibility and maintainability); (3) to improve the user interface and access to individual portions of the code; and (4) to add new modules which incorporate updated physics and 194 / SPIE Vol. 2578 O-8194-1942-7/95/$6.OO Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/16/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

Parameterizing daytime downward longwave radiation in two Korean regional flux monitoring network sites

“…There are several ways to estimate R ld : (1) direct measurements by the pyrgeometers in weather stations (Wang and Liang, 2009); (2) simple physical or empirical models using the screen height measurements of the air temperature and the air humidity usually measured in most weather stations (Sridhar and Elliott, 2002;Duarte et al, 2006;Kjaersgaard et al, 2007;Choi et al, 2008); and (3) more sophisticated radiative transfer models such as LOWTRAN, MODTRAN, and STREAMER incorporated to estimate the reliable actual emission and absorption process in the atmosphere (Kneizys et al, 1988;Snell et al, 1995;Key and Schweiger, 1998). The direct measurements of R ld using pyrgeometers are challenging due to the high cost of the measurement instruments compared to those of surface shortwave radiation using pyranometers (Sridhar and Elliott, 2002;Duarte et al, 2006;Wang and Liang, 2009).…”

Assessment of clear and cloudy sky parameterizations for daily downwelling longwave radiation over different land surfaces in Florida, USA

“…Lacking the required data and measurements noted above, R ld can be calculated using screen height measurements of air vapor pressure and temperature from weather stations via simple physical or empirical models [ Sellers , 1965; Idso and Jackson , 1969; Brutsaert , 1975; Satterlund , 1979; Sugita and Brutsaert , 1993; Prata , 1996; Crawford and Duchon , 1999; Rizou and Nnadi , 2007]. More reliable R ld estimation can be obtained by radiative transfer models such as MODTRAN [ Snell et al , 1995]. However, required input data such as vertical profiles of temperature and air vapor are not typically available [ Niemela et al , 2001; Duarte et al , 2006].…”

Parametric model to estimate clear‐sky longwave irradiance at the surface on the basis of vertical distribution of humidity and temperature

“…The clear‐sky downwelling longwave irradiance at the surface can also be estimated using radiative transfer model such as SBDART [ Ricchiazzi et al , 1998], MODTRAN [ Snell et al , 1995], LOWTRAN [ Kneizys et al , 1988] by taking into account actual emission and absorption phenomena in the atmosphere. To be accurate and to represent actual conditions, radiative transfer calculation require realistic input data (i.e., temperature and humidity profile, aerosol properties) at each time step.…”