51. Weather Types Affect Rain Microstructure: Implications for Estimating Rain Rate
- Author
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Andreas Hamann, Joan Bech, Annette Menzel, Nicole Estrella, and Wael Ghada
- Subjects
Convection ,Quantitative precipitation estimation ,010504 meteorology & atmospheric sciences ,Meteorology ,0207 environmental engineering ,rain spectra ,02 engineering and technology ,Thies ,disdrometer ,weather circulations ,convective ,stratiform ,radar reflectivity–rain rate relationship ,01 natural sciences ,law.invention ,Disdrometer ,law ,Synoptic scale meteorology ,Cloud condensation nuclei ,Radar ,020701 environmental engineering ,lcsh:Science ,Weather ,0105 earth and related environmental sciences ,Temps (Meteorologia) ,Humidity ,Wind direction ,ddc ,Pluja ,Rain and rainfall ,General Earth and Planetary Sciences ,Environmental science ,lcsh:Q - Abstract
Quantitative precipitation estimation (QPE) through remote sensing has to take rain microstructure into consideration, because it influences the relationship between radar reflectivity Z and rain intensity R. For this reason, separate equations are used to estimate rain intensity of convective and stratiform rain types. Here, we investigate whether incorporating synoptic scale meteorology could yield further QPE improvements. Depending on large-scale weather types, variability in cloud condensation nuclei and the humidity content may lead to variation in rain microstructure. In a case study for Bavaria, we measured rain microstructure at ten locations with laser-based disdrometers, covering a combined 18,600 h of rain in a period of 36 months. Rain was classified on a temporal scale of one minute into convective and stratiform based on a machine learning model. Large-scale wind direction classes were on a daily scale to represent the synoptic weather types. Significant variations in rain microstructure parameters were evident not only for rain types, but also for wind direction classes. The main contrast was observed between westerly and easterly circulations, with the latter characterized by smaller average size of drops and a higher average concentration. This led to substantial variation in the parameters of the radar rain intensity retrieval equation Z–R. The effect of wind direction on Z–R parameters was more pronounced for stratiform than convective rain types. We conclude that building separate Z–R retrieval equations for regional wind direction classes should improve radar-based QPE, especially for stratiform rain events.
- Published
- 2020