欧亚大陆春季积雪的年代际变化与...

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

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)

8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0

2 0

3 0

4 0

5 0

- 6 0

- 4 0

- 2 0

0

2 0

4 0

6 0

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 80 90 100 110 120 130 140

20

30

40

50

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

89-75和 60-74夏季降水差

（ Zhang et al., 2008, AMS; Han and Zhang, 2009, AAS ）

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： 1979–2004 ；分辨率：1º1º（ 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： 1979–2004 ；月平均温度、风和位势高度来自 NCEP/NCAR 再分析资料（ v1 ），时段： 1948–2006 。

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1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

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2003

2004

EOF1 时间系数

春季 SWE 的 EOF 第一模态

-2. 5-2

-1. 5-1

-0. 50

0. 51

1. 52

2. 5

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

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2003

2004西伯利亚区域 (55–70N, 60–120E) 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%

-2. 5-2

-1. 5-1

-0. 50

0. 51

1. 52

2. 5

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

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2003

2004西伯利亚区域 (55–70N, 60–120E) 平均的标准化春季 SWE

-3-2-10123

1979

1980

1981

1982

1983

1984

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1986

1987

1988

1989

1990

1991

1992

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2004

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 )

EOF1 Siberia

Composite difference

春季降水 EOF 第一模态春季累积降水气候平均值 (mm) 1979–2004

Composite difference between the LSWI and HSWI cases

Distribution of stations (composite difference exceeds the 0.1 significance level; triangles:

positive; dots: negative)

Climatology


EOF1

Station

-3

-2

-1

0

1

2

3

1979

1980

1981

1982

1983

1984

1985

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1987

1988

1989

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2004

SWE RI

Normalized values of RI (gray bars) and SWE (black bars) over Siberia for the period 1979–2004

Correlation coefficient: 0.7

The differences are significantly positive at 32 stations and significantly negative at 39 stations. Normalized spring rainfall is averaged for the negative and positive stations, respectively, and the difference between them is used as an index (hereafter RI)

LHSHLWSWNH

Composite difference of the net surface heat flux between the LSWI and HSWI cases. Shaded

areas exceed the 0.1 level of significance

Climatology of the net surface heat flux during 1979–2004

Surface heat flux:

Climatology


Wave Activity flux (unit: m2 s–2)

Climatology of meridional and vertical zonal-mean WAF

Climatology of meridional and 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) between the LSWI and HSWI cases

Composite difference of geopotential height at 500 hPa (gpm) between the LSWI and H

SWI cases

SLP 500 hPa

Horizontal moisture flux divergence

Climatology of the horizontal wind field (vectors, m s–1) and horizontal moisture flux divergence (contours and shading, g /[(s cm mb) 107)] at 850 hPa for the period 1979–2004. 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


Vertically integrated water 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 (20–27.5N, 105–120E), southwestern China (20–30N, 95–102.5E), Northeast China (40–45N, 117.5–130E), and northwestern China (37.5–45N, 75–95E)

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， 1988-2004 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。

-2. 5-2

-1. 5-1

-0. 50

0. 51

1. 52

2. 5

1979

1980

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2004

Southeastern China Southwestern China

R=-0.43

Southwest: (-189.7mm) 1979-2004: 587.9mm 1979-1989: 677.3mm

Southeast: (+126.3mm) 1979-2004: 122.4mm 1979-1989: 248.7mm

-2. 5-2

-1. 5-1

-0. 50

0. 51

1. 52

1979

1980

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2004

RAI N

(southeast)-(southwest)

(b)

(1990-2004)-(1979-1989)

500hPa

850hPa

55°-70°N, 60°-120°E

Linear regressed field

500hPa850hPa

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 1979–1987 年间降水偏多， 1988–

2004 年间降水偏少。中国西南 1979–1987 年间降水偏少， 1988–2

004 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。

欧亚大陆春季积雪的年代际变化与...

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