A new index to estimate precipitation using cloud growing rate

A new index assessing the cloud growing rate is described in this paper. It has been designed to be integrated in rainfall estimation procedures. As the highest precipitation rates occur in growing convective cores, integrating this information should enhance the precipitation estimations. The index computation relies on image processing methods. It is composed of two steps: first a watershed segmentation is applied and then an original heritage process is performed. This second step, which is based on a simple matrix computation, is adapted to the watershed algorithm as it mitigates the over-segmentation artefact. This cloud growing rate index is compared with a cooling index which is usually computed to help in identifying raining cells and it is demonstrated to be more efficient. Moreover a simple integration of this index in a widespread rainfall estimation method leads to an improvement of the diurnal cycle retrieval. Citation: Berges, J. C., I. Jobard, and R. Roca (2009), A new index to estimate precipitation using cloud growing rate, Geophys. Res. Lett., 36, L08808, doi:10.1029/2008GL036665.