ATMOSPHERIC MOISTURE BUDGET DURING A BANGLADESH FLOOD EVENT

Using two features of high-resolution global modelling, i.e. physical initialization and residue free moisture budgets we have examined a fl ooding episode over Bangladesh. This study exploits the nowcasting cap ability of the high-resolution model initialization procedure. An inte resting outcome, of averaging daily computations for an entire month, was that the atmospheric moisture budget over Bangladesh was not revea ling the nature of the flooding event. This resulted in a divergence o f moisture flux, a loss of column moisture and evaporation exceeding p recipitation over a computational volume enclosing the flood area. The same type of results were obtained when monthly mean data were used. The most meaningful interpretations were only possible when the time a veraging of the budget was performed for the duration of the heavy rai n period. The nature of the floods is rather episodic and some of thes e, such as the one illustrated here, lasted for a short duration yet p roduced a drastic rise of surface water. Averaging periods for atmosph eric moisture budgets for such events requires more care than simply r esorting to month- or season-long periods.