High-resolution representation of the mechanisms responsible for the initiation of isolated thunderstorms over flat and complex terrains: analysis of CSIP and COPS cases

Abstract

Two important measurement campaigns took place in Europe in the last years, the Convective Storm Initiation Project (CSIP) and the Convective and Orographically-induced Precipitation Study (COPS) to gain a better understanding of why deep convection develops. In both campaigns, a dense network of instruments was deployed for detailed observation of the boundary layer characteristics. This paper investigates the usefulness of the combination of high-resolution surface, GPS, and radiosonde measurements to ascertain the likelihood of deep convection in particular for the complex terrain of the COPS domain. Two convection episodes were analysed for this purpose, one from the CSIP campaign and one from the COPS experiment. This study shows that despite the high spatial resolution of the radiosonde network in comparison to current observations, it was necessary to ascertain higher-resolution data sets illustrating the spatial variability of humidity, atmospheric stability, and convective inhibition. GPS and radiosonde data were used to determine high-resolution humidity fields, yielding high-resolution convection-related parameters’ fields representing atmospheric instability and inhibition in the area. The surface data provided a high-resolution representation of the near-surface convergence zones, which acted as triggering mechanism. The use of GPS measurements and surface stations, in addition to radiosonde measurements, turned out to be especially helpful to determine the regions of increased likelihood of deep convection.