【作者】 李明娟；

【导师】 戴新刚； 许吟隆；

【作者基本信息】 兰州大学 ， 气象学， 2008， 硕士

【摘要】 陕西是我国气候高度敏感区,气象灾害种类俱全,成因独特,如旱灾、低温阴雨、连阴或连暴雨涝、洪灾、雹灾、低温冻害、大风、沙尘暴、寒潮、霜冻、干热风、大雾、龙卷风、酸雨等,而且各类气象灾害频繁发生,使得陕西地区连年遭受各类气象灾害袭击。在目前全球平均气温、海温升高的气候变化背景下,需要对该地区未来气候变化的情景以及极端气候事件发生频率变化的趋势进行研究,了解增加区域气候变化对自然环境和人类已经产生的影响。本文利用英国Hadley气候预测和研究中心的区域气候模式系统PRECIS(Providing Regional Climates for Impacts Studies),基于IPCC《排放情景特别报告》(SRES)的B2情景对陕西2071～2100年的气候变化进行预估,初步分析陕西未来气候变化的概况和极端气候事件发生的频率以及强度,重点对陕西干旱做了分析。本文首先通过对PRECIS模拟与气候基准时段(1961～1990年)的资料进行了分析对比,结果表明,PRECIS模式对陕西温度、极端温度、极端降水等模拟能力较好。B2框架和情景系列描述的世界强调区域性的经济、社会和环境的可持续发展。但是在温室气体持续增加的全球背景下,该情景下陕西2071～2100年逐月平均气温、年平均气温相对气候基准时段有所上升。未来全省年均气温都将增高,未来全省年平均气温将增大3℃以上,未来气温变率为0.17℃/10a。高值区主要还是位于陕南和关中地区,且关中地区高值区范围将有所扩大,可能延伸到渭北地区。渭北是陕西的苹果主产区,单从温度升高的角度分析,未来热量条件对苹果果实膨大、着色和收获较为有利。未来月平均气温变化幅度最大的是冬季(12、1、2三个月),其中12月和2月变化幅度超过100%,1月的幅度也约在100%,这说明未来有向暖冬变化的趋势,春末、夏季、秋初的变化幅度不大,在20%以内。从全省角度来看,未来降水总体是增加的趋势,年均增加约为100mm。未来降水变率为79mm/10a,仍然为增加的趋势。但是未来年降水量的变化幅度较大,出现异常偏多、偏少年份的可能性增加。未来陕西冬春季降水较气候基准时段偏多,平均偏多30%左右,汛期前期的降水偏少,出现伏旱的可能性增大,秋季降水总体偏多,说明未来秋季出现暴雨的可能性较大。与气候基准时段的模拟值比较,未来多年平均降水日数陕北、关中地区的降水日数有不同幅度的增多,增幅最多的是关中中东部和陕北北部,陕南地区的降水日数有所减少。未来陕西降水日数大体上是春季增多、夏秋季减少,春季透雨的来临时间将可能有所提前,夏季出现干旱的可能性增加,华西秋雨在陕西关中、陕南等地的发生频率可能会基本持平但略有减少。未来陕北暴雨日数可能会有所增加,黄河沿线暴雨日数有所增加。由于渭河流域和汉江流域各站暴雨频次均较气候观测基准时段有增加,未来渭河、汉江流域出现致洪暴雨的可能性仍然很大,而且有增加的趋势。本文按照构造的指数关系计算未来的蒸发量,B2情景下,未来蒸发量可能偏多,其中关中地区偏多20%以上,陕北地区可能大于30%。与气候基准时段的模拟值相比,陕西区域内有3个区域干旱频次较少,分别是陕北榆林南部以南到延安全市、关中东部(含渭北)以及陕南西部,幅度最大是黄河沿线;但仍有3个区域干旱频次增加,分别是陕北北部、关中西部秦岭地区和商洛地区。各等级干旱5～7月发生频率较高,这与前面分析的陕西未来夏季降水减少有关,秋冬季干旱发生频率减少,这与前面分析的华西秋雨发生的趋势大体不变有关。虽然总体上干旱发生在秋冬季的频次较少,但是4—5级干旱在秋季发生的频率有所增加,这说明降水逐年分布的不均匀性,某些年份秋冬季降水可能会出现异常偏少。未来即便全省降水会增加,但是由于持续的温度升高,未来出现极端干旱气候事件的可能性仍然增大。更多还原

【Abstract】 Shaanxi province is a climate high-sensitive region of China,enduring various meteorological disasters as drought,low temperature,consecutive cloudy or torrential rains,flooding,hail storm,low-temperature freezing,wind, sand storm,cold wave,frost disaster,dry warm wind,fog,tornado and acid rain etc.Each occurs frequently with a unique cause,which attacks Shaanxi region successive annually.Under the climate change background of global average air temperature and sea surface temperature increase,it is necessary to study future climate change scenario,occurrence frequency change trend of extreme climate events in this region,and investigate existing impacts of increasing regional climate change on natural environment and human.In this paper,the PRECIS(Providing Regional Climates for Impacts Studies,an RCM system developed at the UK Met Office Hadley Center for Climate prediction and Research) is used to estimate climate change from 2071 through 2100 in accordance with SRES B2 scenario of IPCC,and further analyze future climate change situation and extreme climate events occurrence frequency and intensity in Shaanxi,emphasizing on drought.Firstly,compared simulation results of PRECIS with observation data,the results indicate that PRECIS has a good simulating capability of Shaanxi temperature,extreme temperature and extreme precipitation.In a world under SRES B2 scenario,regional economic,social and environmental sustainable development is emphasized.However,under the global background of transient green house gases increase,in 2071 through 2100,the monthly average air temperature and annual average air temperature of Shaanxi increased according to baseline period under scenario B2.In future,annual average air temperature would increase more than 3℃throughout the province.The air temperature change rate would be 0.168℃/10a.The high value center would concentrate on Shaannan(south Shaanxi) and Guanzhong(middle of Shaanxi).The Guanzhong high value center would expand to Weibei(north of Guanzhong),where is a main apple production area.Analyzing only on temperature,the future heat condition would be favorable for apple expansion,coloring and harvest.The maximum change extent of future monthly average air temperature appears in winter(December,January,and February),in which change extent in December and February exceed 100%,and in January approximately 100%. It shows there is a trend of turning into warm winter in future.In spring,summer and autumn,the change extent is less than 20%.Provincially,precipitation shows an accelerating trend in total.Annual average increase is approximately 100mm.In future,precipitation change rate is 79mm/10a,still on an increasing trend.But,the change extent is large,which increases probability of abnormal more or less year.Compared to normal year, in an abnormal more year,precipitation would exceed 600mm.While in a less year,it would reduce approximate 500mm.Precipitation in winter and spring tend to be 30%more than baseline period (1961-1990).Precipitation in early period of flood season is less,raising the drought occurrence probability.Precipitation in autumn is generally more, indicating a big torrential rain occurrence probability in autumn.Compared with baseline simulation data,average yearly precipitation day numbers of Shaanbei(north Shaanxi) and Guanzhong increase in dfferent extents,the maximum in mid-east of Guanzhong and north of Shaanbei, whereas in Shaannan,it decreases.Generally,Shaanxi precipitation day numbers presents increase in spring and decrease in summer and autumn.The soaking rain in spring would probably emerge early.Summer drought probability would increase.The occurrence frequency of Huaxi durative rains in autumn in Guanzhong and Shaannan would probably remain equal but slightly less.Torrential rain day numbers of Shaanbei would probably increase, especially of the regions along the Yellow river.Because the torrential rain occurrence frequency of stations in Weihe valley and Hanjiang valley would increase compared to climatic observations of baseline period,in these two valleys,there would still exist a high probability of flood-induced torrential rain occurrence,and this trend probably increases.In this paper,evaporation is calculated under constructed exponential relationship.Under B2 scenario,future evaporation would be probably more,in which 20%more in Guanzhong,30%more in Shaanbei.Compared to baseline period,there are three regions in Shaanxi with lower drought frequency,respectively,south of south Yulin to Yanan,east of Guanzhong and west of Shaannan.The maximum appears along the Yellow river.Nevertheless,there are still three regions with increasing drought frequency,north Shaanbei,west Guanzhong Qingling Trend,and Shangluo region respectively.Drought of different grades occurs frequently between May and July,which is correlated with the analyzed results,summer precipitation decrease.Drought frequency decreasing in autumn and winter is related to former analyzed trend of Huaxi durative rains in autumn.Although,Drought frequency decreases in autumn and winter in general, 4-5 grade drought increases in autumn,which indicates that yearly precipitation is distributed unevenly.In certain years,precipitation in autumn and winter would probably be abnormally less.Even if precipitation throughout the province increases,with continuing temperature increase,there still exists a high probability of extreme climatic drought event occurrence.更多还原