The occurrence of extreme monthly temperatures and precipitation in two global regions
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There has been a lot of focus on the occurrence of extreme weather events and their connection to climate change and variability. Much of this previous work has been related to individual events rather than for mean monthly conditions. This study examined the occurrence of extreme conditions in the monthly temperature and precipitation, and some correlations, for two geographically disparate regions of the Northern Hemisphere. These regions are the central USA (cUSA), and the southwest region of Russia (swRUS). For this research, an extreme temperature event was defined as a month that was three seasonal standard deviations from the period mean. Since precipitation is not normally distributed, the three (two) wettest and driest events of every month were chosen for the cUSA (swRUS) region in order to provide for a data set that was of similar size to the temperature data set for each region. The results demonstrate that in cUSA, there was preference for the occurrence of warm anomalies during periods of mean regional temperature increase and vice versa. For swRUS, there was a preference for the occurrence of cold anomalies early in the data set, and warm anomalies in the later part, although this period is one of steadily increasing mean temperatures for the region. There was a strong association at both locations between extreme months and the phase of the El Nino-Southern Oscillation (ENSO). In both regions, cold monthly anomalies were associated with persistent and strong upstream blocking events. Finally, two case studies are examined for the cUSA region.
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