Abstract

A climatology of convection initiation (CI) events has been developed using radar reflectivity data in southwestern Germany and eastern France over the period of May-August of 2000 - 2008. The nine-year summertime climatology results are compared with the results from the summer of 2007, during w... Show moreA climatology of convection initiation (CI) events has been developed using radar reflectivity data in southwestern Germany and eastern France over the period of May-August of 2000 - 2008. The nine-year summertime climatology results are compared with the results from the summer of 2007, during which the Convective and Orographically-induced Precipitation Study (COPS) field campaign was conducted. A detailed case study of a COPS day, on 6 August 2007, using two Doppler on Wheels (DOW; Wurman et al. 1997) mobile radar systems, GPS tomography water vapor fields and WRF mesoscale modeling simulations, will also be presented to illustrate potential mechanisms affecting CI on that day. The radar climatology study region included the Vosges Mountains of France, the Rhine Valley which straddles France and Germany, the Black Forest Mountains and the Swabian Mountains of Germany. Convection occurred frequently during the summer months throughout the study region. The CI density illustrates preferential storm development in the mountainous regions. There is a strong mid-day peak of the CI events suggesting that diurnal heating is critical for CI in the region. COPS was conducted with the objective of obtaining improved understanding of convective processes and short-term quantitative precipitation forecasting (QPF) in low-mountain regions (Wulfmeyer et al. 2008). The COPS summer exhibited preferential CI density (CI events per area) in the mountainous regions but not as pronounced as the climatology. Compared with the frequency of daytime, locally-forced CI occurrences during the climatology, the COPS summer appeared to exhibit more synoptically-forced CI. The 6 August 2007 case study illustrates daytime CI along the slopes of the Vosges Mountains. The storms strengthen and merge as they propagate across the Rhine Valley, produce an outflow boundary and cause further CI events in the valley. Preliminary results of this case study will be presented. Show less