【作者】 张颖娴；

【导师】 许吟隆；

【作者基本信息】 中国农业科学院 ， 气象学， 2009， 硕士

【摘要】 在全球变暖的大背景下,自20世纪70年代以来,在更大范围地区,尤其是在热带和副热带,观测到了强度更强、持续更长的干旱,大多数陆地上的强降水事件发生频率有所上升。近50年来观测到了极端温度的大范围变化,冷昼、冷夜和霜冻的发生频率已减小,而热昼、热夜和热浪的发生频率已增加。在某种程度上,极端气候事件发生频率和强度的变化对人类和各项社会生产活动的影响更为严重,因此研究未来可能的极端气候事件变化具有重要的意义。本文采用了英国Hadley气候预测与研究中心的区域气候模式系统PRECIS来进行宁夏地区极端气候事件的情景分析。首先利用1979～1993年ECMWF再分析数据驱动PRECIS对宁夏地区该时期气候进行模拟,对比分析各极端气候指标的模拟结果和观测结果,验证模式模拟极端气候事件的空间分布和年际变化特征的能力;然后将PRECIS模拟的气候基准时段(1961～1990年)的极端气候指标与观测结果进行对比分析,验证模式模拟极端气候事件发生频率的能力;在模式验证的基础上,对模拟数据的订正方法进行初步探讨,并将订正方法应用到情景数据的订正中;最后在考虑订正的基础上,基于政府间气候变化专门委员会(IPCC)《排放情景特别报告》(SRES)的A2和B2情景,对宁夏地区2071～2100年相对于气候基准时段的极端气候事件的可能变化进行了分析。通过本文的研究可以得到以下主要结论:(1) PRECIS能够模拟出极端温度和降水指标的各项特征,模式对温度的模拟具有明显暖偏差,这使得各极端温度指标的模拟值同观测值之间存在系统的偏差。对模拟的温度值订正后,各极端温度指标的订正值保持原有模拟结果本身的波动,并减小了模拟的系统偏差。降水量的模拟值比观测值普遍偏大,这使得极端降水指标的模拟值同观测值存在偏差,对模拟的降水量订正后,各极端降水指标在大多数情况下与观测值的吻合程度好于订正前的模拟值。(2)相对于气候基准时段,至21世纪最后30年,宁夏地区的年极端温度值将显著升高,A2情景下的增温幅度大于B2情景下的增温幅度,宁夏北部的增温幅度大于南部山区的增温幅度。暖日和暖夜事件将显著增加,冷日和冷夜事件将减少。A2情景下极端温度事件的变化比B2情景下更为剧烈,夏秋季节暖日事将件显著增多,冷日事件将显著减少,春季变化不显著。宁夏地区的日较差将减小,尤其冬季和春季减小显著,北部地区减小显著。夏季日数将显著增加,最大连续霜冻日数将显著减少,生长季将延长,这三个极端指标在A2情景下的变化比B2情景下的变化更为剧烈,南部地区的变化比其它地区的变化更为剧烈。(3)相对于气候基准时段,至21世纪最后30年,宁夏地区极端降水事件的日数整体呈现微弱的增加趋势,但逐年变化趋势并非一致增加,而是存在年际波动;北部地区极度降水日数略有增加,南部地区少变化,夏秋季节极端降水日数有少量增加,冬季少变化。宁夏地区大雨日数、简单降水强度和最大连续5日降水量都呈现微弱的增加趋势,北部地区的增加量为全区最多。另外宁夏地区的最大连续干日数将减少,北部地区将减少最多。更多还原

【Abstract】 With global warming, more intense and longer droughts have been observed over larger areas since the 1970s, particularly in the tropics and subtropics. The frequencies of heavy rainfall events have increased over most of land areas. Widespread changes in extreme temperature have been observed over the last 50 years. Cold days, cold nights and frost have become less frequent, while warm days, warm nights and heat waves have become more frequent. It is of great significance to research the possible future changes in extreme climate events because the changes in frequency and intensity of extreme climate events will severely affect human and social activities to some extent.In this paper, the PRECIS, a regional climate model system developed at the UK Met Office Hadley Center for Climate Prediction and Research, is employed to address scenario projection for extreme climate events in Ningxia Provence. First of all, to validate PRECIS capacity to simulate spatial distribution and interannual variability of extreme climate events by comparing the extreme climate indices derived from simulation of PRECIS, which is driven by ECMWF 1979-1993 reanalysis data, with those from observed data. Secondly, to validate PRECIS’s ability to simulate frequency of extreme climate events by comparing the Baseline (1961-1990) extreme climate indices derived from output of PRECIS with those from observed data. Thirdly, the correction methodology to simulated data of PRECIS is preliminarily discussed based on above validation, and is applied to scenario data. Finally, on the basis of correction to output of PRECIS, to analyse the changes of extreme climate events in the future (2071～2100) relative to Baseline under SRES A2 and B2 scenarios of IPCC.The main conclusion of this research can be summarized in the following items:(1) PRECIS has capability to simulate the characteristics of extreme indices of temperature and precipitation, but shows obvious overestimates in simulated temperature and precipitation comparing with observed data which cause the systematic bias between simulated extreme indices and observations. After correction to simulated data, the extreme temperature indices maintain their original fluctuation while the systematic bias has been reduced and the extreme precipitation indices are more consistent with observed data.(2) Relative to Baseline, in the last 30 years of 21st century, the annual extreme temperature would increase remarkably, and the increment under A2 scenario is larger than that under B2 scenario, and the increment in the northern region of Ningxia is larger than that in southern mountain area of Ningxia. Warm days and warm nights would increase notably and cold days and cold nights would decrease. The extreme temperature events under A2 scenario would change more severely than under B2 scenario. Warm days would increase remarkably and cold days would decrease in summer and autumn, while changes of warm days and cold days are not noticeable in spring. DTR would decrease, especially in winter and spring and in northern region. SU would increase remarkably, CFD would decrease remarkably, and GSL would extend. These three extreme temperature indices would change more acutely under A2 scenario than B2 scenario and would change more acutely in southern area of Ningxia than that in other areas. (3) Relative to Baseline, in the last 30 years of 21st century, the days of the extreme precipitation events would show a slender increasing trend as a whole, but annual changes are inconsistent and appear an interannual fluctuation. The extreme precipitation events would increase slightly in northern area of Ningxia, and would show fewer changes in southern area. The extreme precipitation events would increase a little in summer and autumn and change rarely in winter. Over Ningxia, R20mm, SDII and RX5day would increase a little, and the increment would be the largest in northern area. In addition, CDD would decrease, and decrease most in northern area.更多还原