中国西北地区东部雨日的气候特征及其与低空风场的相关性研究

doi:10.7522/j.issn.1000-694X.2013.00126

摘要/Abstract

摘要：

利用中国西北地区东部61个气象站1960—2009年逐日降水资料,分析了雨日数的演变特征。研究发现：200 mm年降水量等值线的两侧存在明显差异,南部半干旱区处于夏季风北部边缘地带,受季风影响,雨日数年际波动大;北部干旱区年雨日数较少且相对稳定。在气旋性风切变辨识算法支持下,本文运用NCEP全球再分析资料风场资料,研究了近50年西北地区东部低空气旋性风切变的演变特征。分析发现,雨日数和低空气旋性风场切变数存在较为显著的正相关,但这种相关性存在明显的季节差异,秋、冬、春3季相关显著,夏季较差。进一步研究发现：水汽条件在雨日数和低空气旋性风切变的关系中起着重要的作用,特别在春、夏两季影响更为明显;秋季青藏高原北部绕流水汽输送带的强弱也直接决定低空气旋性风切变和雨日数的相关性的高低。

关键词: 雨日数, 西北地区, 低空气旋性风切变, 水汽条件

Abstract:

The observed data from 61 stations during 1960-2009 are used to investigate the climatic character of precipitation days in the east of Northwest China. The analysis results indicate that when we chose the contour line of 200 mm annual precipitation as the demarcation value, the northern zone is the arid region and the southern zone is the semi-arid region. The semi-arid region is right situated in the boundary of monsoon zone and the precipitation days change obviously with the inter-annual and inter-decadal variation of monsoon; The precipitation days are few and stable in the arid region. Based on the cyclonic wind shear identification algorithm, the NCEP/NCAR reanalysis wind field data are used to investigate the characters of low-level wind shear. We find the precipitation days and the low-level wind shear frequency are strongly coupled, and there are sharp seasonal differences for the relationship, which is not significant in summer but significant in the other three seasons. Water vapor plays an important role in the relationship between low-level wind shear and precipitation days, especially in spring and summer. The conveyor belt of water vapor over the Tibetan Plateau and its surroundings decides the relationship between the low-level wind shear and precipitation days, especially in autumn.

Key words: precipitation days, Northwest China, low-level cyclonic wind shear, water vapor

中图分类号:

P467

姜旭, 赵光平. 中国西北地区东部雨日的气候特征及其与低空风场的相关性研究[J]. 中国沙漠, 2013, 33(3): 888-895.

JIANG Xu, ZHAO Guang-ping. The Climatic Character of Precipitation Days in the East of Northwest China and the Correlation between the Precipitation Days and Low-level Wind Shear[J]. JOURNAL OF DESERT RESEARCH, 2013, 33(3): 888-895.

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