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<p>This study assesses the impact of changes in water vapour continuum absorption in the MT_CKD (Mlawer-Tobin-Clough-Kneizys-Davies: versions 2.5, 3.2, 4.1.1 and 4.2)) and CAVIAR (Continuum Absorption at Visible and Infrared Wavelengths and its Atmospheric Relevance) models on the broadband radiative transfer calculations of clear-sky atmospheric fluxes and heating rates in the longwave (between 0 and 3200&#xa0;cm<sup>− 1</sup>). The calculations were carried out using the offline ECMWF radiation code and three standard atmospheres: mid-latitude summer (MLS), tropical (TRO) and subarctic winter (SAW). Calculations with the MT_CKD 4.2 model was used as reference. Changes in the continuum models have a relatively larger impact on the radiative fluxes and heating rates for the moister MLS and TRO atmospheres. Compared to calculations with the other four continuum models, the upwelling fluxes due to the use of MT_CKD 4.2 increase by up to ~ 0.68&#xa0;W m<sup>− 2</sup> and ~ 0.82&#xa0;W m<sup>− 2</sup> for the MLS and TRO atmospheres respectively in the mid-troposphere. At the surface, the downwelling fluxes computed with MT_CKD 4.2 decreases by up to ~ 1.8&#xa0;W m<sup>− 2</sup> and ~ 2.0&#xa0;W m<sup>− 2</sup> for the MLS and TRO atmospheres respectively. The use of MT_CKD 4.2 causes the heating rates in the troposphere to increase by up to ~ 5% and ~ 6% for the MLS and TRO atmospheres respectively. These differences in the computed fluxes and heating rates are non-negligible, and water vapour continuum parameterisations in radiation schemes may be revised to reflect the current understanding of continuum absorption in the longwave.</p>

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Dependence of longwave broadband clear-sky radiative fluxes and heating rates on water vapour continuum model updates

  • 期刊论文

  • 发表日期：

    2025年1月20日

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  • Kaah P. Menang

摘要

This study assesses the impact of changes in water vapour continuum absorption in the MT_CKD (Mlawer-Tobin-Clough-Kneizys-Davies: versions 2.5, 3.2, 4.1.1 and 4.2)) and CAVIAR (Continuum Absorption at Visible and Infrared Wavelengths and its Atmospheric Relevance) models on the broadband radiative transfer calculations of clear-sky atmospheric fluxes and heating rates in the longwave (between 0 and 3200 cm− 1). The calculations were carried out using the offline ECMWF radiation code and three standard atmospheres: mid-latitude summer (MLS), tropical (TRO) and subarctic winter (SAW). Calculations with the MT_CKD 4.2 model was used as reference. Changes in the continuum models have a relatively larger impact on the radiative fluxes and heating rates for the moister MLS and TRO atmospheres. Compared to calculations with the other four continuum models, the upwelling fluxes due to the use of MT_CKD 4.2 increase by up to ~ 0.68 W m− 2 and ~ 0.82 W m− 2 for the MLS and TRO atmospheres respectively in the mid-troposphere. At the surface, the downwelling fluxes computed with MT_CKD 4.2 decreases by up to ~ 1.8 W m− 2 and ~ 2.0 W m− 2 for the MLS and TRO atmospheres respectively. The use of MT_CKD 4.2 causes the heating rates in the troposphere to increase by up to ~ 5% and ~ 6% for the MLS and TRO atmospheres respectively. These differences in the computed fluxes and heating rates are non-negligible, and water vapour continuum parameterisations in radiation schemes may be revised to reflect the current understanding of continuum absorption in the longwave.