Preliminary evaluation of the European Centre for Medium-Range Weather Forecasts' (ECMWF) Nature Run over the tropical Atlantic and African monsoon region

Abstract

Moteorological observing systems are continuously being developed to improve our knowledge of the atmosphere and our forecasting capabilities. Observing System Simulation Experiments (OSSEs) are a general technique to assess a priori the potential impact of future instruments, which is particularly important in the case of spaceborne systems. One crucial component of OSSEs is the Nature Run (NR), representing a virtual atmosphere from which observations can be simulated so that the impact of future instruments can be assessed. A community-based, 13-month T511 NR was designed in an international collaborative effort and was produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) to build a next-generation OSSE capability. This new Joint OSSE NR is being analyzed with emphasis on tropical development over the western African monsoon region and the tropical Atlantic. The NR representation of the African Easterly Jet and the characteristics of African Easterly Waves including their propagation and development in tropical-cyclone like vortices are investigated. This is the first NR that encompasses one entire Atlantic tropical cyclone season producing realistic tropical cyclone activity. As such it is a valuable tool to perform OSSEs to assess the possibie impact of future instruments targeting hurricanes. Copyright 2007 by the American Geophysical Union.