Abstract
In this study, a WRF (Weather Research and Forecasting) model is used as a cloud-resolving model to simulate a squall line observed on 20 May 2011 in the Southern Great Plains (SGP) of the United States. The model output is then used to examine the relationships between convective precipitation and coarse-grained variables averaged over a range of subdomain sizes equivalent to various global climate model horizontal resolutions. The objective is to determine to what extent convection within the subdomains can be related to these “large-scale” variables, thus that they can potentially serve as closure in convective parameterization. Results show that convective precipitation is well correlated with the vertical velocity at 500 hPa, column integrated moisture convergence and CAPE change due to large-scale advective forcing (dCAPE) for various subdomain sizes, but the correlation decreases with decreasing subdomain size. dCAPE leads convective precipitation for all subdomain sizes examined; however, the lead time decreases with decreasing subdomain size. Moisture convergence leads convective precipitation for subdomain sizes greater than 32 km but has no lead time for smaller subdomain sizes. Mid-tropospheric vertical velocity has no lead time or slightly lags convective precipitation. The lead/lag composite analysis with respect to maximum precipitation time indicates that peaks of large-scale variables increase with decreasing subdomain size. The peaks of 500 hPa vertical velocity and column integrated moisture convergence occur at the same time as maximum precipitation, but maximum dCAPE leads maximum precipitation by twelve minutes.
Highlights
It is well known that moist convection interacts with large-scale fields; convection acts as a heat source for the large-scale circulation, which destabilizes the atmosphere and the large-scale forcing supplies water vapor and energy to convection
convective available potential energy (CAPE) change due to large-scale advective forcing for various subdomain sizes, but the correlation decreases with decreasing subdomain size. dCAPE leads convective precipitation for all subdomain sizes examined; the lead time decreases with decreasing subdomain size
The essence of convective parameterization closure is to seek a relationship between convection and large-scale or Global Climate Model (GCM) grid–scale variables, such as convective available potential energy (CAPE) and moisture convergence, and to use such relationships to determine the amount of convection, given the large-scale fields
Summary
It is well known that moist convection interacts with large-scale fields; convection acts as a heat source for the large-scale circulation, which destabilizes the atmosphere and the large-scale forcing supplies water vapor and energy to convection. Zhang [8,9] proposed a free tropospheric quasi-equilibrium (FTQE)-based convective closure to relate convection to CAPE generation by large-scale circulation. Zhang examined several large-scale variables used in convective parameterization closures using a cloud-resolving model (CRM) simulation of unorganized tropical convection by Zeng et al [19]. They found that moisture convergence has the best relationship with convection among all closure variables they examined. We seek to determine the scale-dependence (or independence) of such relationships on GCM resolution for organized convection in midlatitudes This has important implications for convective parameterization. Examine the relationship between precipitation and large-scale forcing using MC3E analysis data and CRM simulation data in Section 4 and Section 5, respectively
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
