The relationship between large-scale and convective states in the tropics - Towards an improved representation of convection in large-scale models

Jakob, Christian¹ 

[1] Monash Univ., Melbourne, VIC (Australia)

关键词: Tropical convection;    Climate models;   

DOI  :  10.2172/1171131
RP-ID  :  DOE-MONASH--0002731-1
PID  :  OSTI ID: 1171131

学科分类：环境科学（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

This report summarises an investigation into the relationship of tropical thunderstorms to the atmospheric conditions they are embedded in. The study is based on the use of radar observations at the Atmospheric Radiation Measurement site in Darwin run under the auspices of the DOE Atmospheric Systems Research program. Linking the larger scales of the atmosphere with the smaller scales of thunderstorms is crucial for the development of the representation of thunderstorms in weather and climate models, which is carried out by a process termed parametrisation. Through the analysis of radar and wind profiler observations the project made several fundamental discoveries about tropical storms and quantified the relationship of the occurrence and intensity of these storms to the large-scale atmosphere. We were able to show that the rainfall averaged over an area the size of a typical climate model grid-box is largely controlled by the number of storms in the area, and less so by the storm intensity. This allows us to completely rethink the way we represent such storms in climate models. We also found that storms occur in three distinct categories based on their depth and that the transition between these categories is strongly related to the larger scale dynamical features of the atmosphere more so than its thermodynamic state. Finally, we used our observational findings to test and refine a new approach to cumulus parametrisation which relies on the stochastic modelling of the area covered by different convective cloud types.