34th Conference on Radar Meteorology


On the quality of merged radar-raingauge QPE: Effects due to radar calibration errors, network density, and temporal accumulation

Carlos A. Velasco-Forero, Universitat Politècnica de Catalunya, Barcelona, Spain; and D. Sempere-Torres and G. Pegram

From the very beginning of the use of meteorological radar to estimate quantitative precipitation, the techniques to combine radar and raingauge estimates have been seen as the ultimate step to provide high quality rainfall field estimates.

Much work has been done on that subject and several families of geostatistical approaches have been developed to deal with the challenge of obtaining merged rainfall fields that preserve the direct measurements of rain gauges retaining the detailed spatial structure of rainfall observed in weather radar fields.

Particularly, in the last few years some of these methodologies have been adapted to deal with both the temporal and spatial anisotropy characterizing rainfall fields as well as with the constraints induced by their real-time operational use.

However few studies have been able to characterize the quality of these estimates, since once the radar data available are merged with the available raingauges it is hard to get an independent estimate that could be used as reference field representing the rainfall at the same spatial and temporal resolution.

In this work two collocated radars (3 km apart) that simultaneously registered the same rainfall events together with a dense raingauge network located in the Catalonia Hydrometeorological Observatory (NE Spain) are used to contrast and test the initial quality of the radar QPE and the goodness of the radar-raingauge merging techniques proposed.

Particularly the effect of overestimations/underestimations due to initial calibration errors of both radars in the QPE products and its effects on the quality of the merged estimates are analyzed. The analysis is extended to examine the effect of the length of the period of the temporal accumulation of data, looking for an optimum value, and the effect of the variation in the density of the available raingauges used in the estimation.

A first analysis of the dependence of the quality merged fields with the radar calibration error, the density of the network, the temporal accumulation and the type of rainfall event is also provided.

Poster Session 14, Quantitative Precipitation Estimation and Hydrological Applications
Thursday, 8 October 2009, 1:30 PM-3:30 PM, President's Ballroom

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