Spatial continuity of alpine precipitation

We use radar reflectivity to determine a set of typical variograms of Alpin e precipitation, a summary statistic of spatial continuity. Variogram analy ses benefit from the high resolution of reflectivity estimates in time and space. Spatial continuity of precipitation plays a key role in studying the representativity of point observations (gauge and disdrometer data, reflec tivity profiles), and in distinguishing between stratiform and convective r ain. Because of the direct influence of the orography on precipitation phys ics we expect a complex picture of variograms in the Alps. In fact, the var iogram significantly varies in time and space, and so does the representati vity. The error of a gauge-estimate for the average hourly rainfall in a dr ainage basin may be negligible in stratiform rain but serious in a meso-sca le convective system. Further, the nugget variance of variograms is used to estimate the uncertainty of reflectivity measurements (e.g. caused by rema ining signal fluctuation). For polar pixels we found nugget variances rangi ng from 0.3 to 1.9dB(2)(Z). (C) 2000 Elsevier Science Ltd. All rights reser ved.