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Influence of Superparameterization and a Higher‐Order Turbulence Closure on Rainfall Bias Over Amazonia in Community Atmosphere Model Version 5
Author(s) -
Zhang Kai,
Fu Rong,
Shaikh Muhammad J.,
Ghan Steven,
Wang Minghuai,
Leung L. Ruby,
Dickinson Robert E.,
Marengo Jose
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2017jd026576
Subject(s) - atmosphere (unit) , atmospheric sciences , environmental science , convection , precipitation , atmospheric model , humidity , turbulence , cloud physics , climatology , relative humidity , meteorology , cloud computing , geology , physics , computer science , operating system
Abstract We evaluate the Community Atmosphere Model Version 5 (CAM5) with a higher‐order turbulence closure scheme, named Cloud Layers Unified By Binomials (CLUBB), and a Multiscale Modeling Framework, referred to as the “superparameterization” (SP) with two different microphysics configurations to investigate their influences on rainfall simulations over southern Amazonia. The two different microphysics configurations in SP are the one‐moment cloud microphysics without aerosol treatment (SP1) and two‐moment cloud microphysics coupled with aerosol treatment (SP2). Results show that both SP2 and CLUBB effectively reduce the low biases of rainfall, mainly during the wet season, and reduce low biases of humidity in the lower troposphere with further reduced shallow clouds and increased surface solar flux. These changes increase moist static energy in the lower atmosphere and contribute to stronger convection and more rainfall. SP2 appears to realistically capture the observed increase of relative humidity prior to deep convection, and it significantly increases rainfall in the afternoon; CLUBB significantly delays the afternoon peak rainfall and produces more precipitation in the early morning, due to more gradual transition between shallow and deep convection. In CAM5 and CAM5 with CLUBB, occurrence of more deep convection appears to be a result of stronger heating rather than higher relative humidity.