Advances towards the development of a cloud-resolving model in South Africa

Mary-Jane M Bopape,Francois A Engelbrecht,Willem A Landman,David A Randall

doi:10.1590/sajs.2014/20130133

Abstract

Recent advances in supercomputing have made feasible the numerical integration of high-resolution cloud-resolving models (CRMs). CRMs are being used increasingly for high-resolution operational numerical weather prediction and for research purposes. We report on the development of a new CRM in South Africa. Two bulk microphysics parameterisation schemes were introduced to a dynamical core of a two-dimensional Non-hydrostatic σ-coordinate Model (NSM) developed in South Africa. The resulting CRM was used to simulate two 12-day periods and an 8-day period observed during the Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. The response of the NSM to the large-scale forcing which occurred over the three periods, and which included both suppressed and active convection, was examined. The NSM is shown to be able to capture the differences in the three experiments and responds correctly to the large-scale forcing (i.e. it is able to distinguish between suppressed and active regimes). However, the model simulations are cooler and drier than the observations. We demonstrate progress made in the development of a CRM in South Africa, which can be used to study the attributes of convective rainfall over the region.

Highlights

Non-hydrostatic atmospheric models have been used primarily for research purposes since the 1960s, as their application to operational weather forecasting and climate simulation was hindered by computational restrictions
The PURDUE-LIN scheme was run both with graupel (PURDUE-LIN1) and without graupel (PURDUE-LIN2)
The simulations were found to be colder and drier compared to observations, for all the experiments performed and for all options of microphysics schemes used

Summary

Introduction

Non-hydrostatic atmospheric models have been used primarily for research purposes since the 1960s, as their application to operational weather forecasting and climate simulation was hindered by computational restrictions. G h pressure (hPa) transition and suppressed periods within the longer periods were all of different durations. The PURDUE-LIN scheme was run both with graupel (PURDUE-LIN1) and without graupel (PURDUE-LIN2). The NSM with newly added microphysics is shown to be able to capture general differences in the experiments.

Results

Conclusion