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Title: A flexible importance sampling method for integrating subgrid processes

Numerical models of weather and climate need to compute grid-box-averaged rates of physical processes such as microphysics. These averages are computed by integrating subgrid variability over a grid box. For this reason, an important aspect of atmospheric modeling is spatial integration over subgrid scales. The needed integrals can be estimated by Monte Carlo integration. Monte Carlo integration is simple and general but requires many evaluations of the physical process rate. To reduce the number of function evaluations, this paper describes a new, flexible method of importance sampling. It divides the domain of integration into eight categories, such as the portion that contains both precipitation and cloud, or the portion that contains precipitation but no cloud. It then allows the modeler to prescribe the density of sample points within each of the eight categories. The new method is incorporated into the Subgrid Importance Latin Hypercube Sampler (SILHS). Here, the resulting method is tested on drizzling cumulus and stratocumulus cases. In the cumulus case, the sampling error can be considerably reduced by drawing more sample points from the region of rain evaporation.
 [1] ;  [1]
  1. Univ. of Wisconsin, Milwaukee, WI (United States)
Publication Date:
Grant/Contract Number:
Published Article
Journal Name:
Geoscientific Model Development (Online)
Additional Journal Information:
Journal Name: Geoscientific Model Development (Online); Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 1991-9603
European Geosciences Union
Research Org:
Univ. of Wisconsin – Milwaukee, Milwaukee, WI, (United States)
Sponsoring Org:
USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21)
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; independent-column approximation; stratiform cloud microphysics; probability density-functions; community atmosphere model; boundary-layer clouds; large-eddy simulation; large-scale models; part i; marine stratocumulus; parameterization
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1268218