Abstract
Water budgets terms, evapotranspiration (E), precipitation (P), runoff (N), moisture convergence (MC) and both surface as well as atmospheric residual terms have been computed with National Centers for Environmental Prediction (NCEP) (1948-2007) and European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-40 (1958-2001) reanalysis data sets for Central Southwest Asia (CSWA).The domain of the study is 45° - 75°E & 25° - 40°N. Only the land area has been used in these calculations. It is noted in the comparison of both reanalysis data sets with Global Precipitation Climatology Centre (GPCC) that all three data sets record different precipitation before 1970. The maximum is from NCEP and the minimum with ERA-40. However, after 1970 all the data sets record almost the same precipitation. ERA-40 computes two phases of MC. Before 1975, the domain acts as a moisture source, whereas after 1975 it behaves as a moisture sink. The region CSWA is divided into six sub areas with rotational principle factor analysis and we distinguish them by different approached weather systems acting on each area. Finally, NCEP yearly precipitation is further divided into seasons; winter (November to April) and summer (May to October) and two phases have been noted. The variation in winter precipitation is more than summer during last 60-year analysis.
Highlights
Central Southwest Asia, which mainly includes, Iran, Afghanistan, Pakistan, Tajikistan, Iraq and Saudi Arabia, is located between 45 ̊ - 75 ̊E and 25 ̊ - 40 ̊N, from mid-latitudes to the tropics, with the Arabian Sea to the south, Great Himalayas and Karakoram to the east, the Caspian Sea and Russian states in north and the Black Sea and Tigris river basin in west
Evapotranspiration (E), precipitation (P), runoff (N), moisture convergence (MC) and both surface as well as atmospheric residual terms have been computed with National Centers for Environmental Prediction (NCEP) (1948-2007) and European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-40 (1958-2001) reanalysis data sets for Central Southwest Asia (CSWA).The domain of the study is 45 ̊ - 75 ̊E & 25 ̊ - 40 ̊N
The land area has been used in these calculations. It is noted in the comparison of both reanalysis data sets with Global Precipitation Climatology Centre (GPCC) that all three data sets record different precipitation before 1970
Summary
Central Southwest Asia, which mainly includes, Iran, Afghanistan, Pakistan, Tajikistan, Iraq and Saudi Arabia, is located between 45 ̊ - 75 ̊E and 25 ̊ - 40 ̊N, from mid-latitudes to the tropics, with the Arabian Sea to the south, Great Himalayas and Karakoram to the east, the Caspian Sea and Russian states in north and the Black Sea and Tigris river basin in west. Upland and mountain parts of Pakistan with adjacent areas of India have a dry continental and subtropical climate with a main feature being the southwest monsoon, which lasts for 4 months, from June to September. The region lies at the boundary of three climate regimes These are: 1) the cold Siberian High in winter over Central Asia; 2) the monsoon Asian Low in summer over India; and 3) eastward propagating secondary low-pressure systems traveling through the Mediterranean and adjacent areas during non-summer seasons. Our study area is the central southwest Asia covers an area of approximately 4.67 × 1012 m2, (Figure 1)
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