IMPACT OF ENSO ON THE PRECIPITATION OVER CHINA IN WINTER HALF YEAR
-
摘要: 利用1979—2010年观测和再分析资料，诊断分析ENSO对中国华南冬半年降水的影响及其机制。结果表明，在El Niño冬半年期间，东亚沿岸上空对流层低层南风的增强导致了水汽输送明显偏多，水汽在华南辐合，使得大气可降水量和比湿增加，降水显著偏多。而在La Niña冬半年期间，这些大气要素并没有呈现显著的相反变化，负异常的量值很弱并在统计上不显著。通过进一步分析El Niño和La Niña冬半年期间季节内振荡的特点，给出一种华南冬半年降水对ENSO信号不对称响应的物理解释。El Niño期间，热带西太平洋到南海地区的季节内振荡不活跃，与El Niño相联系的西北太平洋反气旋性环流异常造成的水汽输送以及水汽辐合在华南能够稳定维持，致使华南降水明显偏多。但在La Niña冬半年期间，季节内振荡很活跃，与La Niña相联系的西北太平洋气旋性环流异常受到季节内时间尺度的扰动影响，ENSO的年际变化信号被季节内振荡破坏，使得西北太平洋和华南的年际异常信号不能得到稳定维持，导致与ENSO信号相联系的年际变化在统计上不显著。因此，热带西太平洋到南海地区的季节内振荡强度在El Niño和La Niña冬半年期间的差异，是华南冬半年降水对ENSO信号不对称响应的一个主要原因。Abstract: The impact of ENSO on the precipitation over China in winter half year is investigated by using observed and reanalysis datasets in 1979—2010. The results show that positive precipitation anomalies with statistical significance appear over southern China in El Niño episodes, which are caused by the enhanced warm and humid southwesterliesalong the East Asian coast in the lower troposphere. The enhanced southwesterlies transport more water vapor to southern China, and the convergence of water vapor over southern China increases the precipitable water and specific humidity in the atmosphere. In La Niña episodes, no reverse precipitation anomalies with statistical significance appear over southern China. Although atmospheric elements are changed reversely, they are not statistically significant as those in El Niño periods. The possible physical mechanism of the asymmetric impact of ENSO cycles on the precipitation over southern China is investigated by analyzing the intraseasonal oscillations (ISOs) in El Niño and La Niña, respectively, in winter half year. By comparing the characteristics of ISOs in El Niño and La Niña, a physical mechanism is proposed to explain the asymmetric responses of the precipitation over China toENSOin winter half year. In El Niño episodes, over western North Pacific (WNP) and South China Sea (SCS) the ISOs are inactive and exert little effect on the water vapor transport and convergence, inducing the positive precipitation anomalies with statistical significance over southern China in El Niño episodes. In La Niña episodes, however, the ISOs are active, which weaken the interannual variation signals of ENSO over WNP and southern China and lead to the insignificance of the interannual signals related to ENSO. Therefore, the asymmetric responses of precipitation over China to ENSO in winter half yearare possibly caused by the difference of intraseasonal oscillations over WNP and SCS between El Niño and La Niña.
-
图 3 El Niño (a) 和La Niña (b) 的冬半年水汽输送矢量距平 (矢量，单位：g/(cm·hPa·s)) 及其散度 (等值线，单位：10-6 g/(cm2·hPa·s))
阴影区表示统计检验达到5%的信度区域。
图 5 El Niño (a、c) 和La Niña (b、d) 的冬半年OLR距平 (单位：W/m2) (a、b) 和方差 (单位：W2/m4)(c、d) 方框范围为110~140 °E，5.0~17.5 °N。
图 6 El Niño (实线) 和La Niña (虚线) 冬半年期间5.0~17.5 °N之间平均的850 hPa季节内振荡动能距平 (单位：m2/s2)
a. 20~70 d；b. 10~20 d。
图 7 El Niño (a、c) 和La Niña (b、d) 冬半年20~70 d (a、b) 和10~20 d (c、d) 的OLR季节内振荡方差距平
单位：W2/m4。方框说明同图 5。
-
[1] RASMUSSON E M, WALLACE J M. Meteorological aspect of El Niño/Southern Oscillation[J]. Sci, 1983, 222(4 629): 1 195-1 202. [2] 符淙斌.埃尔尼诺/南方涛动现象与年际气候变化[J].大气科学, 1987, 11(2): 209-220. [3] HUANG R H, WU Y F. The influence of ENSO on the summer climate change in China and its mechanisms[J]. Adv Atmos Sci, 1989, 6(1): 21-32. [4] WANG B, WU R, FU X. Pacific-East Asian teleconnection: How does ENSO affect East Asian climate[J]. J Clim, 2000, 13(9): 1 517-1 536. [5] ZHANG R H, SUMI A, KIMOTO M. Impact of El Niño on the East Asian monsoon: A diagnostic study of the '86/87 and '91/92 events[J]. J Meteor Soc Japan, 1996, 74(1): 49-62. [6] HUANG R H, ZHANG R H, ZHANG Q Y. The 1997/98 ENSO cycle and its impact on summer climate anomalies in East Asia[J]. Adv Atmos Sci, 2000, 17(3): 348-362. [7] WU R G, HU Z Z, KIRTMAN B P. Evolution of ENSO related rainfall anomalies in East Asia and the processes[J]. J Clim, 2003, 16(22): 3 741-3 757. [8] LI C Y. Interaction between anomalous winter monsoon in East Asia and El Niño events[J]. Adv Atmos Sci, 1990, 7(1): 36-46. [9] 陶诗言, 张庆云.亚洲冬夏季风对ENSO事件的响应[J].大气科学, 1998, 22(4):399-407. [10] 陈文. El Niño和La Niña事件对东亚冬、夏季风循环的影响[J].大气科学, 2002, 26(5):595-610. [11] ZHOU L T, WU R G. Respective impacts of the East Asian winter monsoon and ENSO on Winter Rainfall in China[J]. J Geophys Res, 2010, 115, D02107, DOI:10.1029/2009JD012502. [12] 金祖辉, 陶诗言. ENSO循环与中国东部地区夏季和冬季降水关系的研究[J].大气科学, 1999, 23(6):663-672. [13] ZHANG R H, SUMI A, KIMOTO M. A diagnostic study of the impact of El Niño on the precipitation in China[J]. Adv Atmos Sci, 1999, 16(2): 229-241. [14] 倪允琪, 邹力, 张向东, 等. ENSO及其对亚洲季风和我国气候变化影响的研究[J].气象科学, 1995, 15(4):30-45. [15] ZHANG R H. Relations of water vapor transports from Indian monsoon with those over East Asia and the summer rainfall in China[J]. Adv Atmos Sci, 2001, 18(5): 1 005-1 017. [16] 黄荣辉, 陈际龙, 刘永.我国东部夏季降水异常主模态的年代际变化及其与东亚水汽输送的关系[J].大气科学, 2011, 35(4):589-606. [17] 王林, 冯娟.我国冬季降水年际变化的主模态分析[J].大气科学, 2011, 35(6):1 105-1 116. [18] HUANG R H, CHEN J L, WANG L, et al. Characteristics, processes and causes of the spatio-temporal variabilities of the East Asian monsoon system[J]. Adv Atmos Sci, 2012, 29(5): 910-942. [19] 李秀珍, 梁卫, 温之平.华南秋、冬、春季水汽输送特征及其与降水异常的联系[J].热带气象学报, 2010, 26(5):626-632. [20] WEN M, ZHANG R H. Quasi-biweekly oscillation of the convection around sumatra and low-level tropical circulation in Boreal Spring[J]. Mon Wea Rev, 2008, 136(1): 189-205. [21] 林爱兰, 李春晖, 谷德军, 等.热带季节内振荡对广东6月降水的影响[J].热带气象学报, 2013, 29(3): 353-363. [22] KALNAY E, KANAMITSU M, KISTLER R, et al. The NCEP/NCAR 40-year reanalysis project[J]. Bull Amer Meteor Soc, 1996, 77(3): 437-471. [23] SMITH T M, REYNOLDS R W. Improved extended reconstruction of SST (1854—1997)[J]. J Clim, 2004, 17(12): 2 466-2 477. [24] LIEBMANM B, SMITH C A. Description of a complete interpolated outgoing longwave radiation dataset[J]. Bull Amer Meteor Soc, 1996, 77: 1 275-1 277. [25] CHANG C P, ZHANG Y, LI T. Interannual and interdecadal variation of the East Asian summer monsoon and tropical Pacific SSTs, Part Ⅱ: Meridional structure of the monsoon[J]. J Clim, 2000, 13(24): 4 326-4 340. [26] LAU K M, CHANG C P. Planetary scale aspects of the winter monsoon and atmospheric teleconnections[M]//Monsoon meteorology. CHANG C P, KRISHNAMURTI T N. Oxford: Oxford University Press, 1987: 161-201. [27] MORRISSEY M L. A statistical analysis of the relationship among rainfall, outgoing longwaveradiation and the moisture budget during January—March 1979[J]. Mon Wea Rev, 1986, 114(5): 931-982. [28] LI C Y. The relationship between low frequency atmospheric oscillation and SST in equatorial Pacific[J]. Chinese Sci Bull, 1999, 44(12): 78-82. [29] REN B H, HUAN R H. 10~25-day intraseasonal variation of convection and circulation associated with the thermal state of the western pacific warm pool during boreal summer[J]. Adv Atmos Sci, 2002, 19(2): 321-336. [30] REN B H, HUANG R H. 30~60-day oscillations of convection and circulation associated with the thermal state of the western pacific warm pool during boreal summer[J]. Adv Atmos Sci, 2003, 20(5): 781-793. [31] DUCHON C E. Lanczos filtering in one and two dimensions[J]. J Appl Meteor, 1979, 18(8): 1 016-1 022. -
下载:
点击查看大图
图(8)
计量
- 文章访问数: 1128
- HTML全文浏览量: 63
- PDF下载量: 529
- 被引次数: 0
粤公网安备 4401069904700003号