长江源区1961~2020年气象要素对水文要素影响的周期性分析

Periodic analysis of the influence of meteorological factors on hydrological factors in the source region of the Yangtze River during 1961—2020

分析长江源区气象要素对水文要素的变化趋势及演变周期,并对未来气候变化情境下水文变化进行预测,为未来气候变化应对策略提供科学依据。收集、测定、整理长江源区1961~2020年的气象水文资料(气温、降水量、流量),采用线性回归、Mann-Kendall突变检验和Morlet小波分析法对长江源区气象水文要素进行了周期性分析,运用CMIP5模型中的21种模式的模拟结果,结合RCPs的3种气候情景并耦合SWAT模型,预测未来长江源区地表径流的变化,得到未来气候变化下,长江源区地表径流对气候变化的响应。结果表明:1961~2020年,长江源区年平均气温、年最高气温、年最低气温均呈现显著升高的趋势,年平均气温的升温率最大。年降水量和年流量呈现增加趋势,但趋势不显著(P<0.05)。年平均气温存在22年、10年和4年的周期,其中22年周期最为显著。年最高气温存在27~29年和18~20年的周期,27~29年周期最为显著。年最低气温未来可能会有一个大的周期震荡。年降水量存在27年、14年和7年和3年的周期,其中27年周期最显著。年流量存在27~30年、13年、9年、7年、3年的周期,其中27~30年为这一阶段的主周期。在27年周期变化中,年流量的变化由年降水所致。温度、降水量、流量在不同周期上都存在多次交替变化。在CMIP5模型的3种情景下,地表径流的年际变化很大,总体呈现出下降趋势。RCP2.6气候模式下,2048年径流量最大;RCP4.5气候模式下,2035年径流量最大;RCP8.5气候模式下,2036年径流量是最大的。加强源区气候变化应对策略迫在眉睫。

In order to effectively cope with climate change, the change trend and evolution cycle of meteorological conditions for hydrological factors were studied at the source region of Yangtze River. The hydrological changes were further predicted under the different scenarios of future climate change. On the basis of temperature, precipitation and discharge data from 1961-2020, the key factors of meteorology and hydrology were periodically analyzed through the methods of Linear Regression, Mann-Kendall mutation test and Morlet Wavelet analysis. The response of surface runoff to future climate change was predicted by combining with the simulation results of 21 models in CMIP5 model under 3 climate scenarios of RCPs coupled with SWAT model. The results show that the annual average temperature, annual maximum temperature and annual minimum temperature presented a significant increasing trend from 1961 to 2020, and the warming rate of annual average temperature was the largest. At the same time, the similar trends were also reflected on the annual precipitation and annual discharge whereas they were not significant(P< 0.05). Th evolution cycles for the annual mean temperature were 22-year, 10-year and 4-year respectively, and the 22-year cycle is the most remarkable. The annual maximum temperature had two cycles of 27 ~ 29 years and 18 ~ 20 years, and the former cycle was the most significant. The annual minimum temperature had a potential large periodic oscillation in the future. The annual precipitation presented four cycles of 27-year, 14-year, 7-year, and 3-year, and the 27-year cycle was the most obvious. There were five cycles of 27 to 30 years, 13 years, 9 years, 7 years and 3 years for annual flow, of which 27 to 30 years was the main cycle of this stage. In the 27-year cycle, the change of annual discharge was attributable to the annual precipitation. There were many alternating changes for temperature, precipitation and flow under different cycles. Under the three scenarios of CMIP5 model, the great interannual variation was discovered for surface runoff, which also showed the overall decreasing trend. The maximum surface runoffs under the RCP2.6, RCP4.5 and RCP8.5 climate model were appeared in 2048, 2035 and 2036 respectively. Therefore, it is urgent to strengthen coping strategies for climate change of the Yangtze River source region in future.