Abstract
Abstract. Measuring rain rates over complex terrain is afflicted with large uncertainties, because rain gauges are influenced by orography and weather radars are mostly not able to look into mountain valleys. We apply a new method to estimate near surface rain rates exploiting attenuation data from commercial microwave links in the alpine region of Southern Germany. Received signal level (RSL) data are recorded minutely with small data loggers at the towers and then sent to a database server via GSM (Global System for Mobile Communications). Due to the large RSL fluctuations in periods without rain, the determination of attenuation caused by precipitation is not straightforward. To be able to continuously process the RSL data from July 2010 to October 2010, we introduce a new method to detect wet and dry periods using spectral time series analysis. Its performance and limitations are presented, showing that the mean detection error rates of wet and dry periods can be reduced to 10% for all five links. After, the wet/dry classification rain rates are derived from the RSL and compared to rain gauge and weather radar measurements. The resulting correlations differ for different links and reach values of R2 = 0.81 for the link-gauge comparison and R2 = 0.85 for the link-radar comparison.
Highlights
For the improved understanding of all aspects of the regional water cycle, knowledge of the spatio-temporal distribution of precipitation is of crucial importance
We operate three rain gauges at the slope beneath the steepest link connecting the center of Garmisch-Partenkirchen (700 m a.s.l.) and the summit of Mount Wank (1780 m a.s.l.) to better capture the inhomogeneity of precipitation caused by the orography
To derive meaningful precipitation information from microwave link data, the fluctuations of the Received signal level (RSL) have to be distinguished from those caused by precipitation and those caused by other effects
Summary
For the improved understanding of all aspects of the regional water cycle, knowledge of the spatio-temporal distribution of precipitation is of crucial importance. Improved and scientifically sound water availability information, still suffers from limited quality of available spatial rainfall products This is true in regions with complex orography and complex precipitation variability where the established precipitation measurement methods (rain gauges and radar) are prone to errors. A new possibility to gain additional information on precipitation is to use attenuation data from microwave links. The potential of exploiting attenuation data from commercial microwave links networks has been studied both in theory and praxis to derive line integrated rain rates (Leijnse et al, 2007b; Schleiss and Berne, 2010; Townsend and Watson, 2011; Overeem et al, 2011), spatial rainfall fields (Zinevich et al, 2008) and humidity measurements (David et al, 2009). The rain rates produced by the algorithm are compared with gaugeand radar-derived quantities
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