Prediction of high impact rainfall events over Bangladesh using high resolution MM5 model

An attempt has been made to predict the high impact rainfall events of summer monsoon over Bangladesh using the Fifth-Generation PSU/NCAR Mesoscale Model (MM5) conducting two historical rainfall events on 11 June 2007 and 14 September 2004.The model was run on two way triple-nested domains at 45, 15, 5 km horizontal resolutions using Anthes-Kuo cumulus parameterization schemes (CPS) with MRF planetary boundary layer (PBL). Bangladesh is the main focus area in this study. Thus Bangladesh is taken as inner most (D3) domain with 5 km horizontal resolution to study the variability of predicted rainfall. The model predicted rainfall was compared with TRMM 3B42V6 and BMD observed rainfall.

The MM5 model produces realistic prediction of high impact rainfall events in terms of intensity and structure. The predictions have been made for Day-1 (24-h), Day-2 (48-h) and Day-3 (72-h) in advance. The predictions are more accurate for Day-1 (24-h) and Day-2 (48-h). The prediction deteriorates as the prediction time increases. The prediction has been found to be good even for longer prediction time [(more than Day-2 (48-h)] for relatively stronger case (i.e., 11 June 2007). The prediction accuracy is low for relatively weak case (i.e., 14 September 2004) specially over Day-2 (48-h) of prediction. The prediction may be updated in every 24 hours which would provide more realistic prediction.

Keywords: Prediction; Rainfall; High Impact; TRMM; MM5 Model

DOI: http://dx.doi.org/10.4038/sljp.v12i0.3122

Sri Lankan Journal of Physics, Vol. 12 (2011) 43-58