Temperature and precipitation trends and dryness/wetness pattern in the Zhujiang River Basin, South China, 1961-2007

Spatial and temporal characteristics of temperature and precipitation in the Zhujiang River Basin, South China, are analysed in order to identify tendencies in dryness and wetness. Trend tests are applied to daily temperature and precipitation data from 1961 to 2007 of 192 weather stations. Nine indicators are applied in order to detect cycles of dryness and wetness and are compared with the drought indices Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI). Tendencies in temperature and precipitation characteristics can be observed. Significant positive trends (> 90% confidence level) can be found for annual temperature, number of warm days, longest warm period, no rain days, and longest dry period. A significant increase in temperature by more than 0.7 K from 1961 to 2007 can be observed in the entire basin and the coastal and far western areas in particular. Negative trends are observed for annual cool days, cool period, wet days, and wet period. Almost no significant trends in annual mean and extreme precipitation are detected. Rain days decreased, and a tendency to longer dry periods and shorter wet periods can be observed. The magnitude of indices describing dryness has increased in the Zhujiang River Basin, and dry periods have become longer while wet periods have shortened in time. Rainfall intensity has increased along the coastline and in the far west of the catchment. This tendency can be partially explained by the weakening of the East Asian Summer Monsoon. Regarding the high temperature increases, the influences of the urban heat island effect due to urbanization and industrialization, especially along the coast and at the delta, should be considered. The high station density and data quality are very useful for describing detailed changes in wetness and dryness in the Zhujiang River basin. (C) 2010 Elsevier Ltd and INQUA. All rights reserved.