Simulating midsummer climate over southern Africa using a nested regional climate model

Abstract

Abstract. The Commonwealth Scientific and Industrial Research Organisation (CSIRO)Division of Atmospheric Research limited area model (DARLAM) is used to simulate midsummer (January) climate over southern Africa. Using a one-way nesting procedure, lateral boundary and initial conditions are supplied by the CSIRO nine-level Mark 2 general circulation model (GCM), CSIRO9. In general, the DARLAM results are improved in comparison with those from CSIRO9, although certain deficiencies in the GCM climatology over southern Africa are also present in the nested model results. DARLAM captures the spatial pattern of observed rainfall and interannual rainfall variability over the region as a whole more accurately than CSIRO9. Over most parts of the subcontinent, interannual rainfall variability simulated by DARLAM is not significantly different from observations. Over the steep escarpment region of south-east South Africa, DARLAM simulates more rainfall than CSIRO9 and significantly more rainfall than observed. Over Madagascar, DARLAM simulates more rainfall than CSIRO9, but less than observed, and interannual variability is also significantly less than the observed variability.

Performance assessment of three convective parameterization schemes in WRF for downscaling summer rainfall over South Africa

“…This is an important outcome of the present study since some of the previous studies (Joubert et al 1999;Engelbrecht et al 2002;Hudson and Jones 2002;Boulard et al 2012) had difficulties to reproduce the observed ENSO-southern Africa rainfall relationship in their regional climate modeling experiments. The present study has successfully reproduced the strength of observed ENSO-South Africa rainfall relationship over the period Fig.…”

“…RCMs have previously been used as dynamical downscaling aids for studying regional climates over southern Africa (Joubert et al 1999;Engelbrecht et al 2002;Hud-son and Jones 2002;Tadross et al 2006;Kgatuke et al 2008;Landman et al 2009). The weather research and forecasting (WRF) model (Skamarock et al 2008) is increasingly being used as RCM for downscaling studies over southern Africa (Cre´tat et al 2011(Cre´tat et al , 2012Ratnam et al 2012Ratnam et al , 2013Cre´tat and Pohl 2012;Boulard et al 2012;Vigaud et al 2012).…”

Performance comparison of some dynamical and empirical downscaling methods for South Africa from a seasonal climate modelling perspective

“…However, given the most suitable domain, physical parameterizations and lower boundary conditions, a multi-year integration is required in order to properly recognize anomalous behaviour relative to the regional model's time-averaged behaviour (Goddard et al, 2001), which requires a large amount of computer time and storage space. However, nested modelling approaches are capable of simulating the details of regional climate over southern Africa with greater skill than global models (Joubert et al, 1999). Owing to the large expense involved when using a combination of GCMs and regional models and to a lesser extent a combination of GCMs and empirical downscaling methods, the GCM-based approaches to seasonal rainfall estimation should produce rainfall forecasts with skill that outscores that of simple empirical modelling.…”

A Numerical Simulation Study of the Indian Summer Monsoon of 1994 using NCAR MM5

“…As examples, some of the papers that address climate variability, and related topics of different regions, are provided as examples here; a few of these papers also study the climate change scenarios, along with present day climate simulations as control. These are, over the United States (Dickinson et al 1989;Giorgi 1990;Giorgi et al 1994;Dai et al 1999), Australia (McGregor andWalsh 1993, 1994;Walsh and McGregor 1995), New Zealand (Renwick et al 1998), Europe (Giorgi et al 1990;Marinucci 1996a, 1996b), south Africa (Joubert et al 1999), south America (Nicolini et al 2002;Misra et al 2002), east Asia (Kida et al 1991;Liu et al 1994;Hirakuchi and Giorgi 1995;Sasaki et al 1995;Fukutome et al 1999;Kato et al 1999;Leung et al 1999;Kato et al 2001;Mabuchi et al 2000), China (Zheng et al 2002;Liu et al 2003;Wang et al 2003), east Africa (Sun et al 1999a(Sun et al , 1999b and India (Bhaskaran et al 1996(Bhaskaran et al , 1998Bhaskar Rao et al 2001) etc. Several studies suggest that the finer features of the regional climate are better simulated by the regional climate models, as compared to those by GCMs or reanalysis.…”