Spatio-temporal assessment of WRF, TRMM and in situ precipitation data in a?tropical mountain environment (Cordillera?Blanca,?Peru)

摘要

The estimation of precipitation over the broad range of scales of interest for climatologists, meteorologists and hydrologists is challenging at highaltitudes of tropical regions, where the spatial variability of precipitationis important while in situ measurements remain scarce largely due tooperational constraints. Three different types of rainfall products – groundbased (kriging interpolation), satellite derived (TRMM3B42), and atmosphericmodel outputs (WRF – Weather Research and Forecasting) – are compared for 1 hydrological year in order to retrieve rainfall patterns at timescalesranging from sub-daily to annual over a?watershed of approximately10?000?km2 in Peru. An ensemble of three different spatialresolutions is considered for the comparison (27, 9 and 3?km), as longas well as a range of timescales (annualtotals, daily rainfall patterns, diurnal cycle). WRF simulations largelyoverestimate the annual totals, especially at low spatial resolution, whilereproducing correctly the diurnal cycle and locating the spots of heavyrainfall more realistically than either the ground-based KED or the TropicalRainfall Measuring Mission (TRMM) products. The main weakness of krigedproducts is the production of annual rainfall maxima over the summit ratherthan on the slopes, mainly due to a lack of in situ data above3800?m?a.?s.?l.? This study also confirms that one limitation of TRMMis its poor performance over ice-covered areas because ice on the groundbehaves in a similar way as rain or ice drops in the atmosphere in terms ofscattering the microwave energy. While all three products are able tocorrectly represent the spatial rainfall patterns at the annual scale, it notsurprisingly turns out that none of them meets the challenge of representingboth accumulated quantities of precipitation and frequency of occurrence atthe short timescales (sub-daily and daily) required for glacio-hydrologicalstudies in this region. It is concluded that new methods should be used tomerge various rainfall products so as to make the most of their respectivestrengths.