Investigation on Spatial Distribution of Thunderstorm Rainfalls in the Northwest of Iran

Thunderstorm rainfall is considered as a very vital climatic factor because of its significant effects and often disastrous consequences upon people and the natural environment in the Northwest of Iran. The previous findings have shown that thunderstorm rainfalls occur often in spring and summer seasons and during afternoon and the early evening. Accordingly, the main purpose of current study was the investigation of spatial distribution of thunderstorm rainfalls in the Northwest of Iran by applying gamma function on the available data in the yearly and seasonal (spring and summer) scales. With this aim, initial daily thunderstorm rainfall data observed from 16 synoptic stations have been analyzed. Cluster analysis method is used for station clustering, gamma distribution for description and briefing and ArcView for spatial distribution mapping of thunderstorm rainfalls. Generally, all spatial distribution maps illustrate a decline in thunderstorm activities from west to east and from southwest to northeast of Northwest Iran because of individual or synchronous physiographic effects, synoptic systems and climatic factors.