The dependence of SCM precipitation and clouds on the spatial scale of large-scale forcing at SGP
Submitter:
Tang, Shuaiqi — Pacific Northwest National Laboratory
Area of research:
Atmospheric Thermodynamics and Vertical Structures
Journal Reference:
Science
Previous studies have suggested that some errors in the single-column model (SCM) simulations could be attributed to the lack of spatial variability in the specified domain-mean large-scale forcing. A recently developed, gridded, large-scale forcing data set describes the spatial variability of the forcing fields, which provide an opportunity for single-column models to better simulate spatially inhomogeneous frontal systems.
Impact
The gridded large-scale forcing data describe the spatial variability of the large-scale environment. During the passage of a frontal system, the large-scale forcing fields show different features in different part of the domain; therefore the domain-mean forcing fields may not be able to represent the actual large-scale conditions. Gridded large-scale forcing data describe the spatial variability of the forcing fields, which helps SCMs capture these spatially inhomogeneous features. By configuring the gridded large-scale forcing data into different resolutions, we can investigate the scale mismatch between model simulations with point measurements, and investigate the scale dependence of parameterizations.
Summary
We run the single-column model of CAM5 in each sub-column of the analysis domain for a deep frontal case in 2-3 March 2000 at ARM's Southern Great Plains (SGP) observatory, then average the sub-column simulations over the analysis domain. The domain-averaged sub-column simulations are then compared with SCM simulation with domain-mean forcing. The results show that the simulation with sub-column forcing reduces the delay of the precipitation onset and captures the secondary peak, which is missing in the simulation with the domain-mean forcing. It also captures the transition feature of the domain-mean high clouds. A simple example is also given to demonstrate that the gridded large-scale forcing data can be used towards testing scale-aware parameterizations.
Time series of surface precipitation and high cloud. Black line represents the domain-mean observation (Obs.). Red line represents the SCAM5 simulation with domain-mean forcing (SCM_DM). Blue line and blue shade represent the mean of the SCAM5 simulations with sub-column forcing (SCM_SC) and the spatial standard deviation, respectively.