东北5月降水在21世纪初的年代际变化及可能成因

doi:10.12006/j.issn.1673-1719.2018.082

摘要/Abstract

摘要：

基于1961—2015年东北地区的台站降水观测资料及全球环流和海温再分析资料,利用统计分析、物理量诊断等方法,探讨了东北5月降水的年代际变化,及其与大气环流和海温外强迫的关系。研究发现,东北5月降水具有和东北盛夏降水明显不同的年代际变化特征,在20世纪80年代中期至90年代初处于年代际偏少阶段,而在21世纪初转变为年代际偏多阶段。东北5月降水在21世纪初的年代际变化主要由5月东北亚低压强弱的年代际变化造成,在21世纪初,东北亚低压相对于气候态明显偏强,有利于东北降水偏多;而在20世纪80年代初至90年代初,东北亚低压减弱为较浅的低槽,导致东北降水偏少。来自北大西洋的欧亚大陆位势高度异常波列引起东北亚上空的垂直运动异常,导致了东北亚低压的上述年代际变化。5月热带北大西洋海温异常很可能是激发上述波列进而造成东北亚低压和东北5月降水在21世纪初年代际变化的外强迫信号。

关键词: 东北地区, 5月降水, 年代际变化, 东北亚低压, 北大西洋海温

Abstract:

Based on monthly gauged rainfall data in Northeast China and the global atmospheric and oceanic reanalysis dataset for 1961-2015, the decadal changes of rainfall in May over Northeast China (NEC) as well as its relationship with atmospheric circulation and sea surface temperature were investigated using statistical and diagnostic methods. Different from that in late-summer, the rainfall in May over NEC depicted negative anomalies during 1984-1993 and positive anomalies during the early 21st century. The decadal changes of rainfall in May over NEC is mainly attributed to the decadal variation of Northern East Asian Low (NEAL) in May. During the early 21st century, the NEAL was much stronger than its climatology, resulting in surplus rainfall over NEC. Nevertheless, the NEAL was weakened into a shallow trough during 1984-1993, leading to deficient rainfall over NEC. A wave train in the geopotential height field over the Eurasia causes significant vertical motion over the Northern East Asia, which contributes to the above variation of the NEAL. The sea surface temperature anomalies over the tropical North Atlantic in May is the possible external forcing generating the above wave train, which gives rise to the corresponding decadal changes of rainfall over NEC.

Key words: Northeast China, Rainfall in May, Decadal changes, Northern East Asian Low (NEAL), North Atlantic sea surface temperature

郭恒,肖子牛. 东北5月降水在21世纪初的年代际变化及可能成因[J]. 气候变化研究进展, 2019, 15(1): 12-22.

Heng GUO,Zi-Niu XIAO. Decadal variation of rainfall in May over Northeast China since the early 21st century and possible causes[J]. Climate Change Research, 2019, 15(1): 12-22.

图/表 12

图1 东北地区38个站点分布图

Fig. 1 Distributions of 38 meteorological stations in Northeast China

图2 1961—2015年东北5月降水的标准化时间序列及其11年滑动平均(a)以及降水序列的滑动t检验(b)

Fig. 2 (a) Normalized time series of rainfall in May over Northeast China during 1961-2015 and its 11-year running mean components, as well as (b) its moving t-test

图3 东北5月降水距平百分率的空间分布(a) 2004—2015年平均,(b) 1984—1993年平均注：气候态为1961—2015年。

Fig. 3 Rainfall anomalies in May over Northeast China, shown as the percentage of the rainfall departure from the 1961-2015 mean. (a) the average of 2004-2015, (b) the average of 1984-1993

图4 东北5月降水年代际偏多时段与偏少时段同期环流场的差值注：浅、深阴影区分别代表显著性水平为0.05、0.01的区域;蓝、红色分别表示负、正异常区;矢量风场合成图上填色表示经向风显著区,红线包围区域表示纬向风显著区。

Fig. 4 Differences of (a) 200 hPa zonal wind, (b) 500 hPa geopotential height and (c) 850 hPa wind in May between 2004-2015 and 1984-1993 (Light and dark shaded areas indicate the anomalies are significant at the 0.05 and 0.01 confidence level, respectively; blue and red color shaded areas indicate confident negative and positive anomalies; shaded areas and areas encircled by red lines in the 850 hPa wind field indicate confident meridional and zonal wind anomalies, respectively)

图5 东北亚地区不同时段平均的5月850 hPa位势高度场（单位：gpm)、矢量风场（单位：m/s）和涡度场

Fig. 5 The 850 hPa geopotential height (unit: gpm), wind vectors (unit: m/s), and relative vorticity (unit: 10-5 s-1) in May over the Northern East Asia. (a) 1961-2015, (b) 2004-2015, (c) 1984-1993

图6 1961—2015年5月东北亚低压指数的标准化时间序列及其11年滑动平均

Fig. 6 The normalized time series of Northern East Asian Low index and 11-year running mean components for the period 1961-2015

图7 东北5月降水年代际偏多时段(a)和年代际偏少时段(b)平均的5月垂直环流场异常分布注：117.5?~132.5?E平均,垂直速度已扩大100倍;浅、深阴影区分别表示显著性水平为0.05、0.01的区域;蓝、红色分别表示上升、下沉异常区。

Fig. 7 The anomalous vertical movement averaged over 117.5?~132.5?E in May in (a) the average of 2004-2015, and (b) the average of 1984-1993, shown as the departure from the 1961-2015 mean (The vertical speed is amplified by 100, light and dark shaded areas indicate the anomalies are significant at the 0.05 and 0.01 confidence level, respectively; blue and red color shaded areas indicate confident ascending and descending motion)

图8 东北5月降水年代际偏多时段与偏少时段的5月位势高度场的差值注：位势高度场的单位为gpm;浅、深填色区分别表示显著性水平为0.05、0.01的区域;蓝、红色分别表示负、正异常显著区。

Fig. 8 Differences of 200 hPa (a), 500 hPa (b) and 850 hPa (c) geopotential height (unit: gpm) in May between 2004-2015 and 1983-1993 (Light and dark shaded areas indicate the anomalies are significant at the 0.05 and 0.01 confidence level, respectively; blue and red color shaded areas indicate confident negative and positive anomalies)

图9 东北5月降水年代际偏多时段与偏少时段的全球海温场的差值注：浅、深填色区分别表示显著性为0.05、0.01的区域;蓝、红色分别表示负、正异常区;这里冬季指12月至次年2月,春季指3—5月,夏季指6—8月。

Fig. 9 Differences of global sea surface temperature in winter (a), spring (b) and summer (c) between 2004-2015 and 1984-1993 (Light and dark shaded areas indicate the anomalies are significant at the 0.05 and 0.01 confidence level, respectively; blue and red color shaded areas indicate confident negative and positive anomalies)

图10 前期冬季12月至当年8月热带北大西洋海温指数、高纬度北大西洋指数分别与东北5月降水的相关系数演变

Fig. 10 The correlation coefficent from preceding December to current August between the Northeast China rainfall in May and the tropical North Atlantic sea surface temperature index and the high-latitude North Atlantic sea surface temperature index, respectively

图11 1961—2015年5月热带北大西洋海温指数的标准化时间序列及其11年滑动平均

Fig. 11 The normalized time series of the tropical North Atlantic sea surface temperature index and 11-year running mean components for the period 1961-2015

图12 热带北大西洋海温指数正异常年(a)和负异常年(b)合成东北亚地区5月850 hPa位势高度场和矢量风场

Fig. 12 Composition of the 850 hPa geopotential height and wind vectors in May over the Northern East Asia in anomalous positive (a) and negative (b) years of the tropical North Atlantic sea surface temperature index

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