Synoptic Analysis of Upper- Cold Air Pool Effects on Generating or Intensifying Rainfall in the Warm Season in East Azerbaijan

Abstract

In synoptic meteorology, establishment of cold air masses at the middle and upper levels of the atmosphere is called cold air cell or cold air pool (Cold Pool). In this study the role of the cold pool in developing or intensifying the precipitation was examined by studying the synoptic maps for the period from 2007 to 2013 and 118 cases were identified. Synoptic maps, thermodynamic diagram (SkewT) and the distribution of rainfall on the selected days were investigated over East Azerbaijan province. The results showed that cold pool appears in three different synoptic patterns, temperature trough, closed cell or combination of trough and cell (at different levels). Although cold pool has been observed in warm season but the highest frequency appears in May. Investigation of rainfall recorded at the meteorological stations showed that 64% rainfall and 12.2% intense rainfall that has caused flood had been occurred in the establishment of cold pool. The results of thermodynamic diagrams' information indicated that although in most cases of atmospheric instabilities is confirmed by the indicator but in some cases weaknesses was observed in defining air instability which shows that dynamic condition (compared to the thermodynamic) is dominant during the establishment of cold pool. Finally, whenever the temperature difference in 850 and 500 level gets higher the probability of occurrence of intense rainfall, hail and flood are increased.

Keywords

• cold pool
• synoptic analysis
• thermodynamic diagram (skewt)
• precipitation
• flood
• east azerbaijan