Representing 3‐D cloud radiation effects in two‐stream schemes: 2. Matrix formulation and broadband evaluation

Citations Over TimeTop 10% of 2016 papers

Abstract

Abstract Estimating the impact of radiation transport through cloud sides on the global energy budget is hampered by the lack of a fast radiation scheme suitable for use in global atmospheric models that can represent these effects in both the shortwave and longwave. This two‐part paper describes the development of such a scheme, which we refer to as the Speedy Algorithm for Radiative Transfer through Cloud Sides (SPARTACUS). The principle of the method is to add extra terms to the two‐stream equations to represent lateral transport between clear and cloudy regions, which vary in proportion to the length of cloud edge as a function of height. The present paper describes a robust and accurate method for solving the coupled system of equations in both the shortwave and longwave in terms of matrix exponentials. This solver has been coupled to a correlated‐ k model for gas absorption. We then confirm the accuracy of SPARTACUS by performing broadband comparisons with fully 3‐D radiation calculations by the Monte Carlo model “MYSTIC” for a cumulus cloud field, examining particularly the percentage change in cloud radiative effect (CRE) when 3‐D effects are introduced. In the shortwave, SPARTACUS correctly captures this change to CRE, which varies with solar zenith angle between −25% and +120%. In the longwave, SPARTACUS captures well the increase in radiative cooling of the cloud, although it is only able to correctly simulate the 30% increase in surface CRE (around 4 W m −2 ) if an approximate correction is made for cloud clustering.

Related Papers

• → Pseudo bond graph tunnel greenhouse model with accurate longwave/shortwave radiations model(2018)4 cited
• → A new method to diagnose the contribution of anthropogenic activities to temperature: temperature tagging(2012)3 cited
• → A new method to diagnose the contribution of anthropogenic activities to temperature: temperature tagging(2013)2 cited
• → Long-Term, Continuous Net Radiation (Incoming Shortwave and Longwave Minus Outgoing Shortwave and Longwave) Time Series from Measurement Sites in Dry Creek Experimental Watershed, Southwest Idaho(2018)
• → Interactive comment on “Bias correction of surface downwelling longwave and shortwave radiation for the EWEMBI dataset” by Stefan Lange(2017)