Prediction of all-India summer monsoon rainfall with regional and large-scale parameters

Using multiple regression, several statistical models were developed to predict Indian monsoon rainfall from conditions antecedent to the start of the monsoon season (defined as the period June-September). The predictors were selected in a stepwise fashion from a set of 11 predictors. New predictors, such as the preceeding winter to spring sea level pressure change at Bombay, India, which was a leading predictor in all the models, could alone account for 50-60 of the predictand variance. The latitudinal position of the 500-mbar ridge axis in April along 75°E longitude was generally the second predictor to be entered. The regression model based on the earliest development sample (1951-1970), however, had the Southern Oscillation Index of Tahiti-Darwin winter-to-spring sea level pressure tendency as its number two predictor

PRECIPITATION FLUCTUATIONS OVER NORTHERN-HEMISPHERE LAND AREAS SINCE THE MID-19TH CENTURY

An extensive array of measurements extending back to the mid-19th century was used to investigate large-scale changes in precipitation over Northern Hemisphere land areas. Significant increases in mid-latitude precipitation and concurrent decreases in low-latitude precipitation have occurred over the last 30 to 40 years. Although these large-scale trends are consistent with general circulation model projections of precipitation changes associated with doubled concentrations of atmospheric carbon dioxide, they should be viewed as defining large-scale natural climatic variability. Additional work to refine regional variations and address potential network inhomogeneities is needed. This study attempts to show secular precipitation fluctuations over hemispheric- and continental-scale areas of the Northern Hemisphere

The once and future pulse of Indian monsoonal climate

We present a comprehensive assessment of the present and expected future pulse of the Indian monsoon climate based on observational and global climate model projections. The analysis supports the view that seasonal Indian monsoon rains in the latter half of the 21th century may not be materially different in abundance to that experienced today although their intensity and duration of wet and dry spells may change appreciably. Such an assessment comes with considerable uncertainty. With regard to temperature, however, we find that the Indian temperatures during the late 21st Century will very likely exceed the highest values experienced in the 130-year instrumental record of Indian data. This assessment comes with higher confidence than for rainfall because of the large spatial scale driving the thermal response of climate to greenhouse gas forcing. We also find that monsoon climate changes, especially temperature, could heighten human and crop mortality posing a socio-economic threat to the Indian subcontinent. © 2010 Springer-Verlag