Summertime meteorological droughts (floods) and their associated large scale circulation patterns, stream flows and moisture conditions are investigated, using monthly mean divisional temperature and precipitation, NCEP reanalysis, stream flow, sea surface temperature and satellite observations. Reanalysis fields include monthly mean sea level pressure (SLP), 500 mb and 200 mb heights, total precipitable water (TPW), humidity profile and soil moisture.
Meteorological droughts (floods) are classified using empirical orthogonal rotated principal component analysis on a hybrid field composed of monthly mean tempearture and precipitation. A combination of high (low) temperature and deficient (excess) rainfall over the central United States Great Plains, emerged as the dominant pattern. The principal component time series associated with this pattern is a good proxy indicator of droughts (floods). Above (below) normal SLP over the border of Mexico and Texas, North Atlantic, subtropical Pacific appears to have been instrumental in producing droughts (floods). Droughts (floods) are also characterized by strong (weak) anticyclonic circulation anomalies in the middle and upper troposphere. The possible remote forcing is studied using sea surface temperature. Teleconnections of sea surface temperature and TPW over the adjacent oceans and Americas will be discussed and presented in the conference and paper.
Area averaged TPW and its anomaly over the Continental United States (CONUS) are analyzed using NASA Water Vapor Project (NVAP) satellite observations and model reanalysis. The TPW anomaly is relative high during August 1988, while July 1992 is relative low. It is interesting to note that summer 1988 is hot and dry, while July 1992 has abundant rainfall. Humidity profile and soil moisture are incorporated in the study of hydrological conditions. Impacts and conditions on streamflow are analyzed using data over the Mississippi River Basin. Various causes and effects of droughts (floods) over the U.S. Great Plains will be discussed in the paper and conference.