Methods to Evaluate Subcolumn Profiles Based on Two-Point Diagnostics
[1];
[2];
[3];
[3];
- National Center for Atmospheric Research (NCAR), Boulder, CO (United States)
- University of Wisconsin, Milwaukee, WI (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Fachhochschule Aachen, Jülich (Germany)
In atmospheric models, stochastic generation of subgrid-scale profiles or “subcolumns” has been used for a variety of purposes. Such subcolumns can be generated from subgrid probability density functions (PDFs) at different vertical levels, when such PDFs are available. To do so, the generator needs to decide how strongly points should be correlated in the vertical, that is, how much the values should be overlapped. This is sometimes called “PDF overlap.” To assess vertical correlation in a simplified, observable setting, here the vertical correlation of vertical velocity in subcloud layers is examined. Doppler lidar is used to evaluate the vertical profiles of vertical velocity produced by a large-eddy simulation (LES) model and the Subgrid Importance Latin Hypercube Sampler (SILHS) subcolumn generator. In order to diagnose unrealistic features in subcolumn profiles, various statistical diagnostics are examined here, including the bivariate PDF of vertical velocity at two separated points (i.e., altitudes), the two-point velocity correlation, the integral correlation length, the PDF of two-point velocity differences, and the skewness and kurtosis of two-point velocity differences. The profiles produced by LES match lidar well, except that they are too smooth at small scales. The profiles produced by SILHS exhibit sharp jumps from updraft to downdraft that are not observed in the lidar data. To reduce the generation of these unrealistically sharp jumps, the SILHS sampling method is revised. The diagnostics confirm that the revised sampling method reduces the overprediction of sharp jumps.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER)
- Grant/Contract Number:
- AC05-76RL01830; SC0020398
- OSTI ID:
- 2476060
- Report Number(s):
- PNNL-SA--193873
- Journal Information:
- Journal of Geophysical Research. Atmospheres, Journal Name: Journal of Geophysical Research. Atmospheres Journal Issue: 20 Vol. 129; ISSN 2169-897X
- Publisher:
- American Geophysical Union; WileyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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