Assessment of the Impact of Solar Spectral Irradiance on Near‐Infrared Clear‐Sky Atmospheric Absorption and Heating Rates

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 À1 (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. Plain Language SummaryThere have been disagreements in the measurement of the amount of solar energy arriving outside the Earth's atmosphere as infrared, a region with a significant quantity of solar energy. But very little attention has been paid to the effect of these differences in climate modeling. This work examines the impact that the differences in this infrared solar energy have on its absorption by the atmosphere and subsequent heating of the atmosphere by gases such as water vapor and carbon dioxide. Results show that the differences in this infrared solar energy lead to significant differences in absorbed solar energy and heating of the atmosphere. Compared with older measurements of the infrared solar energy, calculations using two recent measurements produce comparable absorption in the atmosphere as well as heating of the atmosphere. This can be interpreted as a good sign that disagreements in measurements of infrared solar energy are decreasing, but some caution should be taken when choosing a measured infrared solar energy for climate simulations. MENANG 6460Key Points:• This work investigates how differences in observed near-infrared solar spectral irradiances affect clear-sky absorption and heating rates • Compared to the widely used ATLAS 3 spectrum, differences of up to 8% in absorption and 11% in heating rates were obtained • Calculations using solar spectral irradiances from recent reanalyses of ground-based and satellite-based data are in closer agreement

Transition Zone Radiative Effects in Shortwave Radiation Parameterizations: Case of Weather Research and Forecasting Model

“…This notable uncertainty observed in the total irradiance, mainly originates from the uncertainty associated with simulation of diffuse irradiance at the transition zone ( = 98% and = 100%). If we assume the whole atmosphere as one atmospheric layer, according to the equation 3 given in Menang () the shortwave heating rate (H, K day −1 ) for the whole column of the reference atmosphere (ΔP = 956 hPa) based on RRTMG simulations would be equal to 2.10 K day −1 . Accordingly, the different treatment of the transition zone at OD = 1.00 will result in a H dispersion range (ΔH) of about 2.50 and 2.43 K day −1 for the cases I‐a and L‐a, respectively.…”

A New Version of the SOLAR-ISS Spectrum Covering the 165 – 3000 nm Spectral Region

“…Moreover, the measurement campaign of the Continuum Absorption in the Visible and Infrared and its Atmospheric Relevance (CAVIAR 2; 1400 -2500 nm) project (Elsey et al, 2017) shows a good agreement with the SOLAR-ISS spectrum, but significant differences from the ATLAS 3 solar spectrum (∼7%). Menang (2018) specifies that the rigorous analysis methods and updated calibrations employed to derive CAVIAR 2 and SOLAR-ISS SSI are strong indicators that these two spectra may be more reliable. With the launch of the Total and Spectral solar Irradiance Sensor (TSIS-1) mission in December 2017, new solar spectral irradiance observations (200 -2400 nm) are available (http://lasp.colorado.edu/data/tsis) since March 2018 af-ter two months of instrument commissioning (Richard et al, 2016;Richard et al, 2018).…”