双月刊

ISSN 1006-9895

CN 11-1768/O4

近几十年中国西北夏秋季干湿年代际变化及成因初步分析
作者:
作者单位:

1.中国科学院大气物理研究所;2.中国科学院大学;3.中山大学大气科学学院

作者简介:

通讯作者:

基金项目:

国家自然科学基金资助项目(42088101, 41730964)和南方海洋科学与工程广东省实验室(珠海)创新团队建设项目(311020001)


Preliminary Analysis on the Interdecadal Change and Cause of Summer and Autumn Dryness and Wetness over Northwest China in Recent Decades
Author:
Affiliation:

School of Atmospheric Science, Sun Yat-sen University

Fund Project:

  • 摘要
  • |
  • 图/表
  • |
  • 访问统计
  • |
  • 参考文献
  • |
  • 相似文献
  • |
  • 引证文献
  • |
  • 资源附件
    摘要:

    本文利用观测和再分析资料,分析了1961~2014年中国西北地区(35°-50°N,75°-95°E)夏秋季节干湿线性变化趋势特征,定量计算了蒸散量和降水量对干湿变化趋势的贡献,同时分析了其年代际变化特征及其相关的大尺度环流和水汽收支变化。结果表明,西北夏季和秋季干旱变率在四季中最大,是干旱最易发生季节。西北地区在1961~2014年夏秋季显著变湿,其中蒸散和降水在西北地区的线性变湿趋势中占主要作用,降水量的增加和蒸散量的减少对西北变湿都有正贡献,二者趋势总贡献率夏季为93.4%,秋季为67.5%。夏秋季西北干湿变化的年代际转折在1987年前后,自1987年后,夏季西北年代际变湿,主要受到蒸散量和降水量变化影响,地面风速减小所造成的蒸散量降低有利于该地区年代际变湿;西北地区水汽输送通量异常辐合导致其降水量增加。水汽诊断分析进一步表明,夏季降水量的增加主要来自于局地蒸发的增强,贡献率达到约80%,表明局地蒸发是降水的重要水汽源。此外,夏季水汽平流项为正值(即水汽通量辐合加强),有利于降水量增加,该贡献主要由与风速有关的动力学分量引起。而秋季,1987年后西北地区的净辐射通量和地面风速减小共同导致该地区蒸散量降低,进而造成西北地区的年代际变湿。

    Abstract:

    Based on the observation and reanalysis data during 1961–2014, the spatial and temporal features of the dry and wet changes in summer and autumn in Northwest China (35°-50°N, 75°-95°E) are investigated. We examine the contribution of evapotranspiration and precipitation to the linear trend of dryness and wetness. Meanwhile, the large-scale atmospheric circulations and water vapor budget related to interdecadal characteristics of dryness and wetness are analyzed. Results show that the drought variability in summer and autumn in Northwest China is the largest in the four seasons, and these two seasons are the highest probability of drought. However, there was a significant increasing trend of wetness in Northwest China from 1961 to 2014, in which evapotranspiration and precipitation play a significant role in the upwards trend in humidity over Northwest China. The increase in precipitation and the decrease in evapotranspiration both positively contribute to the trend of wetness in Northwest China. The total contribution rate of the two trends is 93.4% in summer and 67.5% in autumn. The interdecadal shift from dry to wet happened in summer and autumn around 1987 over Northwest China. Since 1987, the interdecadal humidification was mainly affected by changes in evapotranspiration and precipitation over Northwest China in summer. The decrease in evapotranspiration has a positive contribution to the humidification of the area, which is caused by the decrease in surface wind speed. The anomalous convergence of water vapor transport flux has led to an increase in precipitation in Northwest China. The water vapor diagnostic analysis further shows that the increase in precipitation mainly comes from the enhancement of local evaporation, with a contribution rate of 80%, indicating that local evaporation is an essential source of water vapor for precipitation. In addition, the summer water vapor advection term is positive (that is, water vapor flux convergence is strengthened), which has a positive contribution to the increase in precipitation. This contribution is mainly caused by the dynamic component related to wind speed. In comparison, the decrease in net radiation flux and surface wind speed simultaneously led to a decrease in evapotranspiration in Northwest China in autumn after 1987, which caused interdecadal humidification in the region.

    参考文献
    相似文献
    引证文献
引用本文
分享
文章指标
  • 点击次数:
  • 下载次数:
  • HTML阅读次数:
  • 引用次数:
历史
  • 收稿日期:2021-07-06
  • 最后修改日期:2021-12-23
  • 录用日期:2021-12-31
  • 在线发布日期: 2022-01-18
  • 出版日期: