1、欧亚大陆春季积雪的年代际变化与大气环流的联系及其对中国春季降水的可能影响,张人禾左志燕 武炳义 容新尧中国气象科学研究院,报告内容,背景介绍资料和方法欧亚大陆春季积雪( SWE) 变异特征春季欧亚大陆积雪与中国降水的联系春季欧亚大陆积雪影响中国降水的物理过程春季华南降水与欧亚大陆积雪,报告内容,背景介绍资料和方法欧亚大陆春季积雪( SWE) 变异特征春季欧亚大陆积雪与中国降水的联系春季欧亚大陆积雪影响中国降水的物理过程春季华南降水与欧亚大陆积雪,在年际时间尺度上,西伯利亚西部积雪偏多伴随着华南降水增多 ( Wu and Kirtman,JC,2007).,积雪对大气产生影响的方式有: 1) 通
2、过反射率效应控制太阳入射辐射;2)大气和陆面之间的热绝缘;3)溶雪时产生热汇效应;4)溶雪时的水源作用 (Yasunari et al., 1991; Ellis and Leathers, 1998).,春季北极海冰对中国夏季降水有重要影响 (Wu, et al., GRL,2009),欧亚大陆春季积雪减少,西北太平洋夏季海温升高,90-01和75-89夏季降水差,89-75和60-74夏季降水差,(Zhang et al., 2008, AMS; Han and Zhang, 2009, AAS),报告内容,背景介绍资料和方法欧亚大陆春季积雪( SWE) 变异特征春季欧亚大陆积雪与中国降水
3、的联系春季欧亚大陆积雪影响中国降水的物理过程春季华南降水与欧亚大陆积雪,资料,美国国家雪冰中心提供的由卫星(SMMR,the Scanning Multichannel Microwave Radiometer)获取的月平均雪水当量(Snow Water Equivalent,SWE),时段:19792004;分辨率:11(Armstrong and Brodzik 2005);由中国气象局气象信息中心提供的中国595站月平均降水观测资料,时段:19792004;月平均温度、风和位势高度来自NCEP/NCAR再分析资料(v1),时段:19482006。,报告内容,背景介绍资料和方法欧亚大陆春季
4、积雪( SWE) 变异特征春季欧亚大陆积雪与中国降水的联系春季欧亚大陆积雪影响中国降水的物理过程春季华南降水与欧亚大陆积雪,EOF1时间系数,春季SWE的EOF第一模态,西伯利亚区域(5570N, 60120E)平均的标准化春季SWE,春季SWE与西伯利亚区域平均值的相关系数(涂色区为信度超过0.01的显著区域),Correlation coefficient,EOF1,41.7%,西伯利亚区域(5570N, 60120E)平均的标准化春季SWE,春季SWE EOF1时间系数,低值(LSWEI)与高值(HSWEI)时段合成 SWE 的差值(单位:mm;涂色区为信度超过 0.05 的显著区域),
5、EOF1,Siberia,Composite difference,报告内容,背景介绍资料和方法欧亚大陆春季积雪( SWE) 变异特征春季欧亚大陆积雪与中国降水的联系春季欧亚大陆积雪影响中国降水的物理过程春季华南降水与欧亚大陆积雪,春季降水 EOF 第一模态,春季累积降水气候平均值 (mm) 19792004,Composite difference between the LSWI and HSWI cases,Distribution of stations (composite difference exceeds the 0.1 significance level; triangle
6、s: positive; dots: negative),Climatology,Composite difference,EOF1,Station,Normalized values of RI (gray bars) and SWE (black bars) over Siberia for the period 19792004,Correlation coefficient: 0.7,The differences are significantly positive at 32 stations and significantly negative at 39 stations. N
7、ormalized spring rainfall is averaged for the negative and positive stations, respectively, and the difference between them is used as an index (hereafter RI),报告内容,背景介绍资料和方法欧亚大陆春季积雪( SWE) 变异特征春季欧亚大陆积雪与中国降水的联系春季欧亚大陆积雪影响中国降水的物理过程春季华南降水与欧亚大陆积雪,Composite difference of the net surface heat flux between t
8、he LSWI and HSWI cases. Shaded areas exceed the 0.1 level of significance,Climatology of the net surface heat flux during 19792004,Surface heat flux:,Climatology,Composite difference,Wave Activity flux (unit: m2 s2),Climatology of meridional and vertical zonal-mean WAF,Climatology of meridional and
9、vertical WAF at 90E,composite difference of WAF between the LSWI and HSWI cases at 90E,composite difference of zonal-mean WAF between the LSWI and HSWI cases,Climatology; 90E,Climatology; zonal-mean,Difference; 90E,Difference; zonal-mean,The Arctic Oscillation (AO),Composite difference of SLP (mb) b
10、etween the LSWI and HSWI cases,Composite difference of geopotential height at 500 hPa (gpm) between the LSWI and HSWI cases,SLP,500 hPa,Horizontal moisture flux divergence,Climatology of the horizontal wind field (vectors, m s1) and horizontal moisture flux divergence (contours and shading, g /(s cm
11、 mb) 107) at 850 hPa for the period 19792004. Shaded areas represent moisture flux divergence exceeding 0.5,Composite difference between LSWI and HSWI cases. and shaded areas indicate composite difference exceeding the 0.1 significance level,Climatology,Composite difference,Vertically integrated wat
12、er vapor,8.9,16.3,14.4,10.2,11.6,-0.2,1.87,5.76,2.01,6.10,-11.6,7.58,23.5,24.4,-0.06,2.82,6.98,3.83,8.05,-1.57,3.1,2.3,2.83,1.0,0.64,0.65,0.06,0.72,0.77,1.56,0.64,1.4,2.0,1.6,-0.3,1.44,0.82,1.73,0.23,southeastern China (2027.5N, 105120E), southwestern China (2030N, 95102.5E), Northeast China (4045N,
13、 117.5130E), and northwestern China (37.545N, 7595E),Climatology,Composite difference,Climatology of vertically integrated water vapor in spring,Composite difference of vertically integrated water vapor in spring between LSWI and HSWI,2.0,Summary (1),春季欧亚大陆积雪在1979-2004年期间表现为下降趋势。1979-1987年间为正异常,1988
14、-2004年期间未负异常。伴随着春季欧亚大陆SWE的减少,春季降水负异常出现在中国东南和东北,正异常出现在西南和西北。春季欧亚大陆积雪减少,中纬度向上和向北的准定常波通量减弱,对流层中下层极区附近气压降低,中纬度地区气压增高,出现明显的AO正位相。在中国区域与高气压相联系的流场,减弱了东北和东南的水气辐合,使得降水减弱;而西北和东南增强的水汽辐合使得降水增加。,报告内容,背景介绍资料和方法欧亚大陆春季积雪( SWE) 变异特征春季欧亚大陆积雪与中国降水的联系春季欧亚大陆积雪影响中国降水的物理过程春季华南降水与欧亚大陆积雪,R=-0.43,Southwest: (-189.7mm) 1979-2
15、004: 587.9mm 1979-1989: 677.3mm,Southeast: (+126.3mm) 1979-2004: 122.4mm 1979-1989: 248.7mm,(southeast)-(southwest),(b),(1990-2004)-(1979-1989),500hPa,850hPa,55-70N, 60-120E,Linear regressed field,500hPa,850hPa,Summary (2),无论在年际还是在年代际时间尺度上,中国东南和西南的降水呈现出反位相变化。中国东南19791987 年间降水偏多,19882004年间降水偏少。 中国西南19791987年间降水偏少,19882004年间降水偏多。 中国华南降水的年代际变化可能与春季欧亚大陆积雪减少相联系的西伯利亚高压的增强有关。,Thanks!,