JOURNAL OF NATURAL RESOURCES ›› 2014, Vol. 29 ›› Issue (6): 990-1002.

• Resources Evaluation •

### Change in Extreme Precipitation Events over Tibet from 1961 to 2012

DU Jun1,2, LU Hong-ya2, JIAN Jun3

1. 1. Institute of Plateau Meteorology, China Meteorological Administration, Chengdu 610071, China;
2. Tibet Climatic Center, Lhasa 850001, China;
3. Shannan Meteorological Service of Tibet, Tesdang 856000, China
• Received:2013-04-07 Revised:2013-08-22 Published:2014-06-24

Abstract:

Variations and trends in extreme climate events are more sensitive to climate change than the mean values, and so have received much attention. In this study, the features for ten indices of precipitation extremes over Tibet are examined, broadly based on daily precipitation data during the period 1961-2012 from 18 meteorological stations. The methods of 10-year smoothing average, linear regression, Mann-Kendall test and continuous wavelet transform were employed to delineate the rate of change, abrupt change points, statistical significance of the trends, and periodicity of extreme precipitation indices. The results show that Consecutive Dry Days (CDD) exhibit significant decreasing trend during the recent 52 years, so does the maximum 5-day precipitation (RX5day), but the variation trend of the latter is not significant. In contrast, there is not an obvious linear variation trend in very wet day precipitation (R95) and number of medium precipitation days (R10mm), whereas other six extreme precipitation indices have non-significant increasing trends. Compared with over the globe, the Qinghai-Tibet Plateau and its surrounding areas, regression slopes of CDD and continuous wet days (CWD) over Tibet are obviously greater, but regression slopes of maximum 1-day precipitation (RX1day), R95 and extremely wet day precipitation (R99) are apparently smaller. Except for CDD, other extreme precipitation indices can be quadratically regressed against altitude. Moreover, R10mm is positively associated with longitude. With regard to the period of variation, almost all extreme precipitation indices vary at three or four years scale, and most indices have such periods as 12 a, 15 a and 16 a. In terms of the change point, CDD occurs in 1974, much earlier than such indices as R10mm, CWD and wet day precipitation (in the late 1980s). From the spatial distribution characteristics of extreme precipitation indices, the variation trend in western Naqu is more distinct, and most of the extreme precipitation indices are observed to be dropping in most parts of the middle reaches in the Yarlung Zangbo River. On the other hand, escalating trends in extreme precipitation value and precipitation intensity are found in southern Shannan and southeastern Nyingchi.

CLC Number:

• P426.6