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利用1960—2004年我国586个气象站的逐日降水观测资料,对每个季节和每个站点,以雨日降水量升序排列的第90个百分位值定义极端日降水阈值,分析揭示了我国四季极端雨日数的时空变化特征、与海表温度异常的关系以及相联系的大气环流异常型。结果表明,我国长江流域极端雨日数在冬季和夏季呈显著增加趋势,华北地区极端雨日数在冬季显著增加、而在夏季显著减少,华南地区极端雨日数在春季显著增加,东北地区极端雨日数在冬季和春季显著增加,而西北地区极端雨日数在四季均显著增加。各季极端雨日数在线性趋势变化之上表现年际和年代际变化特征,并且其典型异常型明显不同,春、秋季表现为长江以南与以北地区反位相的"偶极型"变化,夏季表现为长江流域与华南、华北地区反位相的"三极型"变化,冬季表现为全国大部分地区同位相的"单极型"变化。我国季节极端雨日数与印度洋-太平洋海表温度异常的关系主要表现为与ENSO的关系,而ENSO影响我国极端降水异常是通过相应的大气环流异常型来实现的。  相似文献
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With daily precipitation records at 586 stations in China for 1960-2004, this study investigates the spatio-temporal variation of the number of extreme wet days (NEWD) for each season in China and its relationship with SST anomalies and associated atmospheric circulation anomaly patterns, in which a threshold of extreme precipitation for a season and a station is defined as the value of the 90th percentile when the precipitation records for wet days during the season are ranked in an increasing order. Results show that there are significant increases of the NEWD along the Yangtze River valley during winter and summer, in North China during winter, in South China during spring, in Northeast China during winter and spring, and in Northwest China throughout the seasons, while there is a remarkable decrease in North China during summer. Besides the linear trend, the NEWD also exhibits considerable interannual and interdecadal variabilities. After eliminating the linear trend, the NEWD anomalies show distinct seasonal patterns. The NEWD anomalies are characterized by a "dipole" mode with opposite phases between northern and southern China in spring and autumn, a "tri-pole" mode with opposite phases between Yangtze River valley and southern and northern China in summer, and a "monopole" mode with the same phase over most of China in winter. The relationship of the NEWD anomalies in China with the SST anomalies in Indian and Pacific Oceans is found to be mainly dependent on the ENSO, and associated atmospheric circulation anomaly patterns for the ENSO’s impact on the NEWD in China are identified.  相似文献
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1960-2011年洞庭湖区年降水量变化特征   总被引:1,自引:0,他引:1  
以洞庭湖区24个气象站1960--2011年降水量资料为基础数据,利用气候倾向率、Mann—Kendall突变检验法、小渡分析等方法分析了洞庭湖区年降水量的变化特征,并采用正交分解函数EOF、旋转正交分解函数REOF计算了洞庭湖区年尺度的标准化降水指数(SPI),分析了洞庭湖区的旱涝时空分布特征。结果表明:洞庭湖区年降水量空间上由北向南逐渐增加,时间上没有显著变化趋势。1963年洞庭湖年降水量发生突变。洞庭湖区年降水量存在6、9a和16—17a振荡周期。洞庭湖区旱涝频繁,极端气候事件有增加的趋势。洞庭湖区年降水量在空间上具有较好的一致性,即普遍干旱或洪涝,但也存在南北反相变化即南部干旱北部洪涝或南部洪涝北部干旱的特点。洞庭湖区年降水量存在南部、西北部和中部3个异常气候区。  相似文献
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