基于统计降尺度的渭河流域未来日极端气温变化趋势分析

Trends of Daily Extreme Air Temperature in the Wei River Basin in the Future

本文基于GCM输出和统计降尺度技术,在渭河流域应用统计降尺度模型SDSM(Statistical Downscaling Model),选取日最高和最低气温作为预报量,分析了渭河流域未来最高气温与最低气温的变化趋势。利用NCEP再分析数据与站点实测数据选择合适的预报因子并建立大尺度环流因子和预报量之间的经验统计关系,其中数据序列分为1961年～1990年和1991年～2000年2个时段,分别用于模型率定和验证;然后,应用确立的统计关系将HadCM3输出的未来数据(包括A2、B2两种情景)降尺度到站点尺度,基准期选取1961年～1990年。研究结果表明:渭河流域未来日最高和最低气温总体呈增温趋势,其增温幅度在A2情景下比B2情景下高;两种情景下,日最高气温增温幅度较日最低气温略大;日最高和最低气温在2020s、2050s和2080s时期的空间变化趋势较为一致;日最高和最低气温的空间变化在A2和B2情景下大体呈现出由流域西北部向东南部逐渐变弱的趋势。

Global climate change can have significant impact on local and regional hydrological regime, which will in turn affect the ecological, social and economical systems. However, the study on impact of climate change upon hydrologic regime has not been investigated. The main reason is that Global Circulation Models, which are widely used to simulate the climate scenarios in the future, do not provide daily and local data that are reliable enough for hydrological modeling. At present, this problem is usually resolved with downscaling methods. A Statistical Downscaling Model （SDSM） is applied to the case study in the Wei River basin. In this paper, daily maximum and minimum air temperature （Tmax/Tmin） are selected as the predictands. The selection of appropriate downscaling predictors is based on the relationship between meso-scale atmospheric variables and daily Tmax/Tmin series in the basin, which are obtained from the NCEP re-analysis data set and observed data respectively. Data series i...更多s divided into two groups with time ranges of 1961-1990 and 1991-2000, in order to calibrate and validate the model respectively. Then, the outputs form A2 and B2 scenarios simulated by using HadCM3 are downscaled to station level. Finally, the future trends of daily Tmax and Tmin, in three periods, which are the 2020s （2010-2039）, the 2050s （2040-2069）, and the 2080s （2070-2099） in the Wei River basin, are analyzed according to the baseline of 1961-1990. The results show that some meso-scale circulation variables are closed related to Tmax/Tmin in the basin, including surface mean temperature, near surface specific humidity, 500 hPa and 850 hPa geopotential heights and there is an obvious increasing trend in daily Tmax and Tmin in the future. Both daily Tmax and Tmin show a greater increasing range in A2 scenario that in B2 scenario, while daily Tmax shows a greater increasing range than Tmin in both scenarios. The spatial distributions of daily Tmax and Tmin are similar over the periods of the 2020s, 2050s and 2080s. The daily increments of Tmax and Tmin in A2 and B2 scenarios become smaller from the northwest to the southeast of the basin. Since the air temperature is important for runoff generation, the warmer temperature in the future could have great impacts on the runoff and the sand in the basin. The results of this paper can be used as reference for the generation of climate change scenarios in the impact assessment of climate change, it is also indicated that the responses of hydrological regime to climate change need further to be investigated.