全球变暖背景下济南及其周边地区极端温度与降水事件变化分析

Analysis on the Changes of Extreme Temperature and Precipitation Events in Ji’nan and Its Surrounding Areas Under the Background of Global Warming

选用19702015年济南及其周边地区的47个台站数据,采用气候统计方法,对济南及其周边地区的极端气候的时空分布特征进行了分析。研究发现,济南及其周边地区近地层的气温1970年在同经度带、同纬度带中均为显著增长趋势。夏日日数、热持续日数在1990年以前多呈现和“南低北高”相反的空间分布,1990年后“南低北高”的空间分布特征更加明显。济南及其周边地区暖夜日数、暖昼日数在19701995年偏少,在19952015年呈现一致性偏多,并有增强趋势。大部分极端降水指数具有较为统一的空间一致性,平均日降水强度在19701990年表现为鲁中南部及鲁西北北部偏小、鲁西北南部及鲁中东部偏大的反位相分布型,1990年后呈反位相分布型。年总降水量及平均日降水强度在1990年前后发生突变。1990年以来,500 hPa位势高度从欧洲东部开始自西北向东南呈现出“正负正”的三明治式分布,欧亚地区易形成两高一低的环流形势,冷空气易南下与西南暖湿气流在山东交汇,形成有利于降水的天气形势。19912015年的风场与气候态平均差值显示,700 hPa风场自孟加拉湾至山东地区偏南暖湿气流显著增强,925 hPa为水平辐合区,辐合易使低层水汽聚集,200 hPa为水平辐散区,这种高层辐散低层辐合的上下层配置,使垂直上升运动增强。水汽、热量等物理量的垂直输送,使降水系统发展。济南及其周边地区东边界中高层及近地面层存在水汽通量正值区,中低层为水汽通量负值区,西边界在中低层存在水汽通量正值区,其余为大范围负值区;南边界上除中层外,其余大部分层次上是显著的水汽通量输出区,北边界与南边界的水汽通量情况相反。

The surface observation data of 47 stations and NCAR/NCEP data from 1970 to 2015 in Ji’nan and its surrounding area are selected to use in this paper.Based on the climate statistical method,the extreme climatic characteristics in Ji’nan and the surrounding area are analyzed.The main results are as follows:The near-surface temperature in Ji’nan and its surrounding areas has a significant increasing tendency since 1970 in the same latitude and longitude zone.Before 1990,summer days and heat persistent days mostly showed the reverse phase distribution pattern of“low in South and high in north”,and after 1990,the typical distribution pattern of“low in South and high in north”increased.The numbers of warm nights and warm days in Ji’nan and its surrounding areas were relatively small during 19701995,but consistently showed an increasing trend in 19952015.Most extreme precipitation indices have relatively uniform spatial consistency.From 1970 to 1990,the average daily precipitation intensity showed a reverse phase distribution pattern,which means the precipitation was less in the central and southern part and the northwestern part of Shandong province,but more in the southern part of northwestern Shandong and the central and eastern part of Shandong province.After 1990,precipitaion had an inverse-phase distribution pattern.The annual total precipitation and the average daily precipitation intensity changed abruptly around 1990.Since 1990,the 500 hPa geopotential height has presented the“positive-negative-positive”distribution.The circulation situation of“two ridges and one trough”was easy to form in Eurasia,and cold airs traveled southward,converging with the warm-humid southwest airflows in Shandong,forming a synoptic situation conducive to precipitation.Compared with the average of climate state,during 19912015,the 700 hPa warm-humid southerly airflow from Bay of Bengal to the south of Shandong province strengthened significantly.The 925 hPa was the horizontal convergence zone which makes the water vapor in the lower layer aggregate easily,and the 200 hPa was the horizontal divergence area,forming the configuration of high-level divergence and low-level convergence,which enhanced the vertical upward motion.Therefore,the vertical transport of water vapor,heat and other physical quantities drives the development of precipitation system.In the east boundary,there is a positive area of water vapor flux in the mid-high level and near-surface level,while in the mid-low level the water vapor flux is negative.On the other hand,in the west boundary,there is a positive zone of water vapor flux in the middle and low levels,and the rest is a large negative area.In the south boundary,except the middle layer,the significant water vapor flux output area is found at most layers.The water vapor flux in the north boundary is the opposite to that of the south boundary.