32nd Conference on Broadcast Meteorology/31st Conference on Radar Meteorology/Fifth Conference on Coastal Atmospheric and Oceanic Prediction and Processes

Sunday, 10 August 2003: 4:15 PM
Small scale variability of Mediterranean precipitation during HIRE'98
Alexis Berne, Wageningen University, Wageningen, Netherlands; and G. Delrieu, J. D. Creutin, and R. Uijlenhoet
Poster PDF (208.8 kB)
The variability of Mediterranean rainfall is a crucial point for (i) atmospheric modelling (quality assessment of numerical simulations, microphysical processes involved, data assimilation); (ii) hydrological modelling (identification of the main mechanisms generating flash-floods in the Mediterranean environment); and (iii) rainfall measurement network design.

In this paper, we investigate the rainfall variability using data from a set of complementary rain sensors. In particular, a network of 25 rain gauges, an X-band RHI and an S-band CAPPI radar were employed during the HIRE'98 experiment in Marseille, France (autumn 1998). We performe a structural analysis based on the variogram calculated in two dimensions for the radar reflectivity field (in dBZ) corresponding to the three most intense rain events.

The variability of rainfall is studied in the vertical through the analysis of the RHI measurements (1 min. and 125 m resolution). The 2D variograms show a strong anisotropy of the rainfall field. The mean structure is consistent with the generating cell model.

In the horizontal, the 2D variograms based on the CAPPI measurements display a strong anisotropy as well as they suggest the existence of nested structures. The time evolution of the 2D variograms show the influence of advection on the structure of the rainfall field.

Finally, the comparison of the average 1D variograms obtained from the rain gauge network on one hand and the CAPPI measurements on the other indicates a similarity in the rainfall structure assessment obtained from these two sources.

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