【作者】 徐红；

【导师】 王文；

【作者基本信息】 南京信息工程大学 ， 气候系统与全球变化， 2012， 硕士

【摘要】 Palmer(?)旨数基于水平衡原理建立的,具有明确的物理意义。所以Palmer指数评估干旱时,不仅能指示干旱的程度,还能很好的显示干旱发生的时间,但Palmer(?)旨数空间的不连续性,在研究区域旱涝时要对其进行订正。通过相近气候的美国东南部和淮河流域干旱特征对比,以及国内几次有重要参考意义的Palmer指数修正结果研究,发现各区域不同的旱涝等级对后期的影响程度存在很大的差异。因此,本文应用淮河流域36测站的逐日温度、风速、日照时数等站点资料等对Palmer指数进行订正,适当调整前期旱涝对后期的影响程度,使其更适合淮河流域旱涝研究,并用Mann-Kendall突变检验方法、滑动t检验法、Morlet小波分析淮河流域温度、降水及旱涝指数的分布特征。并利用NCEP/NEAR逐月风场及位势高度场,通过合成分析方法,分析了淮河流域旱涝年南亚高压异常引起的淮河流域旱涝年环流异常的机制。研究结果表明：(1)因为区域不同旱涝等级对有无降水的敏感度不同,适当调整Palmer(?)指数前期旱涝对后期的影响程度,计算的淮河流域Palmer指数对淮河流域旱涝的强度及时间反应更切合实际。(2)通过基于Palmer(?)旨数的区域指数结果分析,可以看出整个淮河流域而言,冬、春、夏、秋呈：湿润化—干旱化—湿润化—干旱化相间分布态势。冬、夏季趋于湿润而两个过渡季春、秋干旱化加剧。春季变干趋势和2007年IPCC第四次报告中指出很可能因为全球变暖导致的春季发生事件时间提前吻合。因为春季温度升高提前,致使蒸发增加,或温度的间接影响,有可能是春季趋于干旱的一个原因。(3)因指数的机理不同,对同一地区旱涝的反应也会有很大的差异。PDSI指数反应干旱时,不仅考虑当期降水异常,还考虑了前期的水分状况,干旱发生的累积效应可以在PDSI指数上有很好的体现。降水变率变化对各种指数反应的旱涝有很大的影响。(4)淮河流域夏季存在明显的偏旱期,而干旱的分布形势不尽相同。1966-1978年汛期降水和暴雨量较平均态波动不大,PDSI指数反应的干旱有明显的峰值现象。1992-2001年汛期降水和暴雨量异常明显,即变率较大,PDSI指数反应的干旱分布比较平滑。从夏季温度上看,在1966-1978年出现持续的降温期；而1992-2001年对应温度升温期。因而可以推断温度的升高很可能造成极端降水的增加,因而,温度的变化不仅仅直接影响蒸发而影响干旱,还可能通过降水对旱涝起调节作用。(5)利用NCEP逐月风场、位势高度场、水汽场等资料,通过合成分析方法分析了流域旱、涝年环流及水汽输送的异常。110°E-140°E、35°N-50°N区域是南亚高压影响东亚一个关键区域,也是引起的淮河流域旱涝年环流异常的关键区。100hPa南亚高压向东北方向的伸缩和东亚高纬经向环流活动有密切的关系,也是副高异常的征兆,南亚高压通过对流层-平流层的相互作用影响着副高的活动。淮河流域异常年南亚高压的异常主要集中在夏季前期,而副高的异常主要在夏季后期,这个突显了南亚高压异常具有一定的预测意义。更多还原

【Abstract】 Palmer Drought Severity Index (PDSI) based on water balance principle is meaningful in physics.So PDSI could not only indicate the drought severity degree, but also when the drought would occurre. But the modification should be done because of the spatial discontinuities.The results of comparing the drought condition in Huaihe River Basin and the USA Southeas t region, as well as several modified Palmer index results show that the drought/wet conditions in different areas would affect the condition later differently. And based on the conventional surface observations daily temperature, wind, sunlight hours and other information from36stations there, a modification of PDSI with appropriate adjustment of the influence of early period drought/wet condition is carried out to indicate the drought/wet more accurately. A few of discussions about the distribution characteristics of the annual or seasonal precipitation and temperature in Huaihe River Basin was carried out with the Mann-Kendall mutation testing, moving t test, Morlet wavelet analysis and so on.Using NCEP/NEAR monthly wind and geopotential height field, the analysis of circulation anomaly in flood and drought years in the Huaihe River Basin caused by South Asia high were investigated,and the results show that:(1) Because of the sensitivity of an area to precipitation changed when it was in different drought/wet grade, appropriate adjustment of the influence of pre-period in the calculation of PDSI, the results reflect the drought or flood more accurately.(2) The area index based on Palmer Drought Severity Index distributions showed that in the recent50years, the area index based on Palmer Drought Severity Index distributions showed that the climate condition trends for winter, spring, summer, autumn were more wetter-drier-wetter-drier in the whole of Huaihe River basin. And this coincided with the increasing (decreasing) frequency and intensity in precipitation in summer (spring and autumn). There was a good coincidence between the drying trend in spring and the spring event happened earlier properly in the IPCC report in2007. The evaporation increased because of the tempreture rising, or the indirect effects of temperature rising may promote drought condition in spring.(3) It would be different that different index reflecting thedroughts/flood condition due to the Index mechanism in the same area. With the consideration of both the current rainfall anomalies and pre-period moisture conditions, PDSI showed well response to the cumulative effect of drought/flood.The precipitation variability would influence the response to climate condition with different index.(4)There were obvious drought periods in summer while the drought situation was different in Huaihe River Basin. The rainfall and rainstorm in summer fluctuated slightly, and peak drought was obvious in1966-1978.Otherwise,the rainfall and rainstorm in summer fluctuated greatly, and arid distribution by PDSI index was relatively smooth in1992-1999.The temperature dropped down sustaintly in1966-1978, and a warming period in1992-1999. It could be inferred that the temperature increasing was likely to promote the extreme precipitation, therefore, temperature change would not only impact on the drought through evaporation directly, but also on extreme precipitation indirectly.(5) Analysis of the circulation and water transportation abnormally were carried out based on monthly NCEP winds field, geopotential height field and specific humidity field. The east Asia influenced by the South Asia High especially through the area at110°E-140°,35°N-50°N. There was good coincidence between the South Asia high anomaly at100hPa and the drought/wet condition in Huaihe River Basin, and a good sigh for subtropical high anomaly. And the South Asia high may reflect the circulation above Huaihe River though the troposphere and stratosphere interactions. The South Asia high anomaly happened mainly in the early summer, and the subtropical high anomaly in the later summer, and it showed well that the South Asia high may be a good sigh for the climate anomaly.更多还原