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Evaluation of ACCESS model cloud properties over the Southern Ocean area using multiple‐satellite products
Author(s) -
Luo San,
Sun Zhian,
Zheng Xiaogu,
Rikus Lawrie,
Franklin Charmaine
Publication year - 2015
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.2641
Subject(s) - cloud fraction , environmental science , shortwave , liquid water content , shortwave radiation , cloud computing , satellite , cloud top , parametrization (atmospheric modeling) , longwave , meteorology , cloud height , liquid water path , cloud forcing , climate model , radiative transfer , remote sensing , atmospheric sciences , cloud cover , radiation , climate change , geology , computer science , geography , physics , oceanography , quantum mechanics , astronomy , operating system
Radiation field and cloud properties over the Southern Ocean area generated by the Australian Community Climate and Earth System Simulator (ACCESS) are evaluated using multiple‐satellite products from the Fast Longwave And Shortwave radiative Fluxes (FLASHFlux) project and NASA/GEWEX surface radiation budget (SRB) data. The cloud properties are also evaluated using the observational simulator package COSP, a synthetic brightness temperature model (SBTM) and cloud liquid‐water path data (UWisc) from the University of Wisconsin satellite retrievals. All of these evaluations are focused on the Southern Ocean area in an effort to understand the reasons behind the short‐wave radiation biases at the surface. It is found that the model overestimates the high‐level cloud fraction and frequency of occurrence of small ice‐water content and underestimates the middle and low‐level cloud fraction and water content. In order to improve the modelled radiation fields over the Southern Ocean area, two main modifications have been made to the physical schemes in the ACCESS model. Firstly the autoconversion rate at which the cloud water is converted into rain and the accretion rate in the warm rain scheme have been modified, which increases the cloud liquid‐water content in warm cloud layers. Secondly, the scheme which determines the fraction of supercooled liquid water in mixed‐phase clouds in the parametrization of cloud optical properties has been changed to use one derived from CALIPSO data which provides larger liquid cloud fractions and thus higher optical depths than the default scheme. Sensitivity tests of these two schemes in ACCESS climate runs have shown that applying either can lead to a reduction of the solar radiation reaching the surface and reduce the short‐wave radiation biases.