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Based on a generated time series for the central pressure of the Siberian High, and on defining a robust Siberian High Index (SHI), the behavior of this atmospheric center of action is examined from 1949 to 2010 with regard to inter-annual variations, persistence, trends, abrupt changes, spectral analysis and interactions. The interannual variability in the central pressure of the Siberian High is considerable. The mean downward linear and non-linear trend over the entire period (1949-2010) is estimated and is found to be statistically significant at the 95 % confidence level. Low frequency variation and linearity within the SHI time series are found from the persistence analysis. Using spectral analysis, the center of action of the Siberian High is characterized by non-periodic behavior; the peaks occur only at the lowest frequency and may be related to the Sea Surface Temperature (SST) over the El Niño region. The Siberian High is affected by the Hadley circulation cell; there is no detectable connection between the Walker circulation cell and the Siberian High. SSTs over the El Niño region may affect the Siberian High. Interactions between the Siberian High and the SSTs over the tropical Atlantic Ocean are absent. The SHI is positively correlated to surface air temperatures over Saudi Arabia, and this is statistically significant in the western and north-western regions. [ABSTRACT FROM AUTHOR]

The present paper investigates the role played by blocking high systems over Europe in abnormal weather over the Kingdom of Saudi Arabia (KSA) in summer 2010. The NCEP/NCAR Reanalysis data of several meteorological elements such as surface air temperature, wind, sea level pressure, relative humidity, outgoing long wave radiation, precipitation rate, and geopotential height at level 500 hpa) for summer seasons for the period 1948-2012 and in particular of summer 2010 have been used and analyzed through the present work. Furthermore, the corresponding daily and monthly mean values of climatic indices NAO index, SOI, and El-Nino3.4 have been analyzed. The results uncovered that air current in the upper atmosphere over Europe and NAO, SOI and El-Nino3.4 have impacts on the weather conditions over KSA through the study period 1948-2012. During the period of persistence of blocking system over Europe in summer 2010, results revealed that; weather in KSA was fully controlled by two abnormal weather regimes. The first one is the European blocking system and negative anomaly of NA Of rom the north. The second one is the positive anomaly of SOI and negative anomaly of El-Nino3.4. [ABSTRACT FROM AUTHOR]