Water–air temperature relationships in a Devon river system and the role of flow

The nature of the water–air temperature relationship, and its moderation by discharge, were investigated for catchments ranging in size from 2·1 to 601 km² in the Exe basin, Devon, UK and for data relating to hourly, daily and weekly time bases. The sensitivity and explanatory power of simple water–air temperature regression models based on hourly data were improved by incorporation of a lag, which increased with catchment size, although relationships became more sensitive and less scattered as the time base of data increased from hourly to weekly mean values. Significant departures from linearity in water–air temperature relationships were evident for hourly, but not for daily mean or weekly mean, data. A clear tendency for relationships between water and air temperatures to be stronger and more sensitive for flows below median levels was apparent, and multiple regression analysis also revealed water temperature to be inversely related to discharge for all catchments and time‐scales. However, discharge had a greater impact in accounting for water temperature variation at shorter time‐scales and in larger catchments. Copyright © 2003 John Wiley & Sons, Ltd.     

Precipitation and temperature trends for the Southwest China: 1960–2007

Daily temperature and precipitation data from 136 stations of Southwest China (SWC) during the last five decades, from 1960 to 2007, were analysed to determine the spatial and temporal trends by using the Mann–Kendall trend test. Results show that SWC has become warmer over the last five decades, especially in the recent 20–25 years. The increasing trends in winter months are more significant than those in the months of other seasons, and spatially Tibet, Hengduan mountains area and west Sichuan Plateau have larger temperature trend in magnitude than the other regions have. A downward trend was detected in Sichuan Basin also, but the region with cooler temperature was shrinking due to the statistically significant increasing trend of temperature after 1990s. Both annual and seasonal means of daily maximum and minimum temperatures show an increasing trend, but trend magnitude of minimum temperature was larger than that of maximum temperature, resulting in the decrease of diurnal temperature range for SWC in the last 50 years. Annual precipitation showed slightly and statistically insignificant increasing trend, but statistically significant increasing trend has been detected in winter season while autumn witnessed a statistically significant decreasing trend. The results could be a reference for the planning and management of water resources under climate change. Copyright © 2010 John Wiley & Sons, Ltd.