| Based on the global monthly rain data (PREC viz. Precipitation Monthly Anomalies Over Global Land & Oceans from 1948.1-2004.2) created by Chen et al, NCEP/NCAR reanalyzed global monthly mean wind data and SST data, this paper investigates some problems of the climate change in tropical annual and seasonal precipitation fields during 1948-2003. The main contents and results are as follows.The temporal and spatial features of annual and seasonal precipitation fields over the tropical are analyzed, and negative trend variations are found in all of the annual and seasonal precipitation fields especially in the annual one. It also shows that the interannual and decadal fluctuations of annual and seasonal precipitation are obvious.Through calculating the precipitation trend coefficient in the Tropic, it has been found that significant negative trends occur in annual and seasonal precipitation fields. Then the temporal features of precipitation trend coefficient are analyzed in detail and the positive and negative trend areas are pointed out.The drought and flood years in the Tropic have been plotted out by calculating two tropical indexes in annual and seasonal scales from 1948 to 2003, and have been tested by Monte Carlo tests. Result shows that the distribution of drought and flood years takes on a decadal feature in annual and seasonal scales.The relations between rainfall and wind fields, Hadley circulation and Pacific Walker circulation have been studied. Results suggest that the connection is close with wind fields and Pacific Walker circulation, but is irrelative with Hadley circulation.The relations between rainfall and SST, ENSO events have been analyzed. Evidences suggest that the SST has associated closely with annual and seasonal precipitation changes. It also shows that ENSO events have significant influences on annual and seasonal precipitation. Then the areas whose rainfall will increase or decrease while an El Nino event happens are pointed out. |
