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An improved PDF cloud scheme for climate simulations
Author(s) -
KuwanoYoshida Akira,
Enomoto Takeshi,
Ohfuchi Wataru
Publication year - 2010
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.660
Subject(s) - planetary boundary layer , environmental science , turbulence , meteorology , large eddy simulation , cloud computing , atmospheric model , boundary layer , potential temperature , inversion (geology) , turbulence kinetic energy , computer science , mechanics , geology , physics , paleontology , structural basin , operating system
An efficient grid‐scale cloud scheme for climate simulation is implemented in the atmospheric general circulation model for the Earth Simulator (AFES). The new cloud scheme uses statistical partial condensation using joint‐Gaussian probability distribution functions (PDFs) of the liquid water potential temperature and total water content, with standard deviations estimated by the moist Mellor–Yamada level‐2 turbulence scheme. It also adopts improved closure parameters based on large‐eddy simulations and a revised mixing length that varies with the stability and turbulent kinetic energy. These changes not only enable better representation of low‐level boundary layer clouds, but also improve the atmospheric boundary layer structure. Sensitivity experiments for vertical resolution suggest that O(100–200 m) intervals are adequate to represent well‐mixed boundary layers with the new scheme. The new scheme performs well at relatively low horizontal resolution (about 150 km), although inversion layers near the coast become more intense at a higher horizontal resolution (about 50 km). Copyright © 2010 Royal Meteorological Society