A parameterized yet accurate model of ozone and water vapor transmittance in the solar-to-near-infrared spectrum |
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| Authors: | Weiyi Liu Jinhuan Qiu |
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| Institution: | Key Laboratory of Middle Atmosphere and Global Environment Observation,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing
100029;Key Laboratory of Middle Atmosphere and Global Environment Observation,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing
100029 |
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| Abstract: | A parameterized transmittance model (PTR) for ozone and water vapor monochromatic transmittance calculation in the solar-to-near-infrared
spectrum 0.3–4 μm with a spectral resolution of 5 cm?1 was developed based on the transmittance data calculated by Moderate-resolution Transmittance model (MODTRAN). Polynomial
equations were derived to represent the transmittance as functions of path length and airmass for every wavelength based on
the least-squares method. Comparisons between the transmittances calculated using PTR and MODTRAN were made, using the results
of MODTRAN as a reference. Relative root-mean-square error (RMSre) was 0.823% for ozone transmittance. RMSre values were 8.84%
and 3.48% for water vapor transmittance ranges of 1-1×10?18 and 1-1×10?3, respectively. In addition, the Stratospheric Aerosol and Gas Experiment II (SAGEII) ozone profiles and University of Wyoming
(UWYO) water vapor profiles were applied to validate the applicability of PTR model. RMSre was 0.437% for ozone transmittance.
RMSre values were 8.89% and 2.43% for water vapor transmittance ranges of 1-1×10?18 and 1-1×10?6, respectively. Furthermore, the optical depth profiles calculated using the PTR model were compared to the results of MODTRAN.
Absolute RMS errors (RMSab) for ozone optical depths were within 0.0055 and 0.0523 for water vapor at all of the tested altitudes.
Finally, the comparison between the solar heating rate calculated from the transmittance of PTR and Line-by-Line radiative
transfer model (LBLRTM) was performed, showing a maximum deviation of 0.238 K d?1 (6% of the corresponding solar heating rate calculated using LBLRTM). In the troposphere all of the deviations were within
0.08 K d?1. The computational speed of PTR model is nearly two orders of magnitude faster than that of MODTRAN. |
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| Keywords: | parameterization transmittance atmospheric absorption |
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