季节内振荡影响西太平洋副热带高压两次北跳的机制

苏同华; 薛峰; 陈敏艳; 董啸

doi:10.3878/j.issn.1006-9895.1609.16125

季节内振荡影响西太平洋副热带高压两次北跳的机制

doi: 10.3878/j.issn.1006-9895.1609.16125

苏同华^{1, 2,},
薛峰²,
陈敏艳¹,
董啸²

1.
福建省气象台, 福州 350001
2.
中国科学院大气物理研究所国际气候与环境科学中心, 北京 100029

基金项目:

国家自然科学基金项目 41405056

国家自然科学基金项目 41475052

福建省自然科学基金青年创新项目 2015J05078

华东区域气象科技协同创新基金合作项目 QYHZ201405

详细信息

作者简介:
苏同华, 男, 1982年出生, 博士、高级工程师, 主要从事天气预报、模式释用、东亚季风研究.E-mail:thsu1205@163.com

中图分类号: P466
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出版历程
- 收稿日期: 2016-01-28
- 网络出版日期: 2016-09-20
- 刊出日期: 2017-05-15

A Mechanism Study for the Intraseasonal Oscillation Impact on the Two Northward Jumps of the Western Pacific Subtropical High

1.
Fujian Meteorological Observatory, Fuzhou 350001
2.
International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029

Funds:

National Natural Science Foundation of China 41405056

National Natural Science Foundation of China 41475052

Fujian Natural Science Foundation 2015J05078

East China Cooperative Innovation Foundation of Meteorological Science and Technology QYHZ201405

摘要

摘要: 夏季期间，西太平洋副热带高压（简称副高）存在两次明显的北跳，其中第一次北跳导致华南前汛期结束、江淮梅雨建立，而第二次北跳则意味着江淮梅雨结束、华北雨季开始。本文基于观测资料和再分析数据，利用快速傅里叶变换和合成分析方法，深入探讨不同时间尺度季节内振荡对气候态和异常年副高两次北跳的影响机制。结果表明：在季节内尺度上，平常年和异常年影响副高两次北跳的季节内振荡的主导周期不同。气候态上，以10~20天和准60天为主；第一次北跳异常年和第二次北跳偏早年，以30~60天为主；第二次北跳偏晚年，则呈现出10~20天和30~60天两个主导周期。不论气候态还是异常年，东亚—热带西北太平洋地区低频振荡在年循环背景下均呈现出明显的北传特征，这是导致副高发生两次北跳的重要原因之一。而印度季风区低频振荡在东北向传播过程中所引起的西风东伸是造成副高第一次北跳更为明显的原因。源自澳大利亚高压的冷空气入侵所激发的暖池对流的准双周振荡则是造成气候态和偏晚年副高第二次北跳更为显著的原因。由于前期春季西北印度洋海温出现异常，造成局地低频振荡发生位相迁移，进而导致副高第一次北跳发生异常。而副高第二次北跳异常则是因为ENSO改变了暖池地区季节内振荡的尺度和振幅所造成的。
- 季节内振荡 /
- 西太平洋副热带高压 /
- 北跳 /
- 江淮梅雨 /
- ENSO
Abstract: During summertime, the WPSH (western Pacific subtropical high) exhibits two northward jumps. The first jump signals the termination of pre-flood period in southern China and the start of the Meiyu over the Yangtze-Huaihe River valley; the second jump indicates the termination of the Meiyu and the start of rainy season in northern China. Based on the fast Fourier transformation and composite analysis of observational and reanalysis data, the authors investigated the impact of the intraseasonal oscillations (ISOs) on various time-scales on the northward jumps in the normal and abnormal years. The dominant periods of the ISOs are different in normal and abnormal years, i.e. 10-20 days and quasi-60 days in normal years, 30-60 days in abnormal years of the first jump and earlier years of the second jump, 10-20 days and 30-60 days in later years of the second jump. During the annual cycle, the ISOs tend to propagate northward in the East Asian-tropical northwestern Pacific region, leading to the northward jump of the WPSH. With the northeastward propagation of the ISOs over the Indian monsoon region, a more remarkable first jump is observed due to the eastward extension of the westerly. By contrast, the biweekly oscillation of the warm pool convection triggered by the cold air invasion from the Australian high plays an important role in a more evident second jump during the normal and later years. The sea surface temperature anomaly over the northwestern Indian Ocean in the preceding spring leads to the phase migration of local ISOs and associated abnormal first jump. Besides, the time-scale and amplitude of the ISOs in the warm pool can be regulated by ENSO, resulting in the abnormal second jump.
- Intraseasonal oscillation /
- Western Pacific subtropical high /
- Northward jump /
- Meiyu over the Yangtze-Huaihe River valley /
- ENSO

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图 1 1979~2007年夏季平均的（a）降水（单位：mm d^-1）、（b）500 hPa位势高度场（单位：gpm）以及（c）OLR场（单位：W m^-2）的气候态分布（等值线）和标准差（填色）。图中的实线方框为下文分析中所选取的三个关键区，其范围分别为：（a）（28°N~33°N，107°E~123°E）、（b）（20°N~27.5°N，120°E~135°E）、（c）（5°N~15°N，115°E~140°E）

Figure 1. Climatological distribution (contours) and standard deviation (shaded) of (a) summer precipitation (units: mm d^-1), (b) 500-hPa geopotential height (units: gpm), and (c) outgoing longwave radiation (OLR, units: W m^-2) averaged in the summer during 1979–2007. The rectangles respectively indicate the three key regions for the following analysis: (a) (28°N–33°N, 107°E–123°E), (b) (20°N–27.5°N, 120°E–135°E), (c) (5°N–15°N, 115°E–140°E)

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图 2 关键区（20°N~27.5°N，120°E~135°E）500 hPa位势高度（单位：gpm）的（a）气候平均逐日变化曲线（用5天滑动平均表示，实线）和年循环曲线（虚线）以及（d）去除年循环的季节内振荡曲线和（g）相应的功率谱分析。（b、e、h）同（a、d、g），但为长江中下游地区（28°N~33°N，107°E~123°E）的降水分布曲线（单位：mm d^-1）。（c、f、i）同（a、d、g），但为暖池（5°N~15°N，115°E~140°E）的OLR分布曲线（单位：W m^-2）。（d、e、f）中季节内振荡曲线为5天滑动平均变化曲线减去年循环曲线后所得的曲线；（g、h、i）中实线为功率谱，虚线为95%信度水平的标准红噪音谱

Figure 2. (a) Climatological daily curves (5-day running mean, solid line) and annual cycles (dashed line) of geopotential height (GH, units: gpm), (d) intraseasonal oscillation curves (units: gpm) with the annual cycles removed, and (g) their power spectra at 500 hPa in the key region (20°N–27.5°N, 120°E–135°E). (b, e, h) As in (a, d, g), but for precipitation (units: mm d^-1) in the middle and lower reaches of the Yangtze River (28°N–33°N, 107°E–123°E). (c, f, i) As in (a, d, g), but for OLR (units: W m^-2) in the warm pool (5°N–15°N, 115°E–140°E). The intraseasonal oscillation curves in (d, e, f) are obtained from 5-day running means minus annual cycles. Solid lines in (g, h, i) represent the power spectra of the intraseasonal oscillation, and the dashed lines indicate the standard red-noise spectra at the 95% confidence level

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图 3 去除年循环后500 hPa关键区（20°N~27.5°N，120°E~135°E）平均的位势高度小波分析的（a）小波谱（左）和功率谱（右）以及（b）小波分析的实部。图a中的网格区域为通过95%信度水平卡方检验的区域

Figure 3. The wavelet analysis of area-mean geopotential height at 500 hPa with the annual cycle removed in the key region (20°N–27.5°N, 120°E–135°E): (a) Wavelet spectrum (left) and power spectrum (right); (b) the real part. Net regions in Fig. 3a indicate the regions pass at the 95% confidence level by chi-square test

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图 4 去除年循环后的（a）关键区（20°N~27.5°N，120°E~135°E）500 hPa位势高度（单位：gpm）、（b）长江中下游降水（单位：mm d^-1）以及（c）暖池OLR（单位：W m^-2）的季节内振荡曲线。黑线表示5~90天振荡，蓝线表示10~20天振荡，红线表示40~90天振荡

Figure 4. The intraseasonal oscillation curves (with the annual cycle removed) of (a) geopotential height (GH, units: gpm) in the key region (20°N–27.5°N, 120°E–135°E), (b) precipitation (units: mm d^-1) in the middle and lower reaches of the Yangtze River, and (c) OLR (units: W m^-2) in the warm pool. Black, blue, and red lines indicate intraseasonal oscillation with periods of 5–90 days, 10–20 days, and 40–90 days, respectively

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图 5 （a，b）10~20天和（c，d）40~90天滤波后副高两次北跳阶段500 hPa位势高度的差值场（单位：gpm）。（a）和（c）为6月15~24日与6月5~14日之差；（b）和（d）为7月25日到8月3日与7月15~24日之差

Figure 5. Differences at 500-hPa geopotential height (units: gpm) between post-jump and pre-jump periods of the western Pacific subtropical high (WPSH) with (a, b) the 10–20-day band pass filtering and (c, d) the 40–90-day band pass filtering. (a, c) 15–24 June minus 5–14 June; (b, d) from 25 July to 3 August minus 15–24 July

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图 6 同图 5，但为850 hPa风场和OLR场。箭头表示风场（单位：m s^-1），填色表示OLR（单位：W m^-2），下同

Figure 6. As in Fig. 5, but for 850-hPa wind and OLR. Arrows represent wind (units: m s^-1), shadings represent OLR (units: W m^-2), the same below

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图 7 气候态副高第一次北跳阶段40~90天滤波的850 hPa风场（单位：m s^-1）和OLR场（单位：W m^-2）：（a）第一次北跳前20天（5月26日）；（b）北跳前10天（6月5日）；（c）北跳日（6月15日）；（d）北跳后10天（6月25日）

Figure 7. The 40–90-day band pass filtered wind (units: m s^-1) at 850 hPa and OLR (units: W m^-2) on (a) the twentieth day before the first jump (26 May), (b) the tenth day before the first jump (5 June), (c) the first jump date (15 June), (d) the tenth day after the first jump (25 June) of the climatological mean WPSH

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图 8 同图 7，但为副高第二次北跳阶段：（a）北跳前20天（7月5日）；（b）北跳前10天（7月15日）；（c）北跳日（7月25日）；（d）北跳后10天（8月4日）

Figure 8. As in Fig. 7, but for the second jump stage: (a) The twentieth day before the jump (5 July); (b) the tenth day before the jump (15 July); (c) the jump date (25 July); (d) the tenth day after the jump (4 August)

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图 9 10~20天滤波后的OLR（单位：W m^-2）随时间沿西北方向传播的剖面。传播路径以（5°S，150°E）为起点，（25°N，120°E）为终点，向西北方向每隔2.5°选取一个点，一共13个点。考虑到横坐标宽度有限，为清晰起见，横坐标方向仅标出4个点的经、纬度

Figure 9. The cross section of the 10–20-day band pass filtered OLR (units: W m^-2) propagating along northwest direction with time. The northwestward pathway starts at (5°S, 150°E) and ends at (25°N, 120°E). The total number of points is 13 with the interval of 2.5°. For clarity, only 4 points are marked in the abscissa

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图 10 气候态副高第二次北跳阶段10~20天滤波的850 hPa风场（单位：m s^-1）和OLR场（单位：W m^-2）：（a）北跳前15天（7月10日）；（b）北跳前10天（7月15日）；（c）北跳前5天（7月20日）；（d）北跳日（7月25日）

Figure 10. The 10–20-day band pass filtered wind (units: m s^-1) at 850 hPa and OLR (units: W m^-2) on (a) the fifteenth day before the second jump (10 July), (b) the tenth day before the second jump (15 July), (c) the fifth day before the second jump (20 July), (d) the second jump date (25 July) of the climatological mean WPSH

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图 11 副高两次北跳异常年关键区（20°N~27.5°N，120°E~135°E）500 hPa位势高度的功率谱：（a）副高第一次北跳偏早年（1980、1984、1988、1989、1991、1996、1999、2008年）；（b）副高第一次北跳偏晚年（1982、1986、1992、1994、1995、1997、2002、2005年）；（c）副高第二次北跳偏早年（1981、1984、1985、1988、1994、1997、2001年）；（d）副高第二次北跳偏晚年（1980、1982、1987、1993、1998、2003年）。黑色实线：北跳异常年合成的功率谱；黑色虚线：95%信度水平的红噪音谱

Figure 11. The power spectra of 500-hPa geopotential height averaged over the key region (20°N–27.5°N, 120°E–135°E) in the years of abnormal jumps of WPSH: (a) Earlier years for the first jump (1980, 1984, 1988, 1989, 1991, 1996, 1999, 2008); (b) later years for the first jump (1982,1986, 1992, 1994, 1995, 1997, 2002, 2005); (c) earlier years for the second jump (1981, 1984, 1985, 1988, 1994, 1997, 2001); (d) later years for the second jump (1980, 1982, 1987, 1993, 1998, 2003). The solid black lines indicate the composite for the abnormal years, and the black dashed lines indicate the corresponding red-noise spectrum at the 95% confidence level

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图 12 副高第一次北跳偏早年合成的北跳阶段30~60天滤波的850 hPa风场（单位：m s^-1）和OLR场（单位：W m^-2）：（a）第一次北跳前20天（5月16日）；（b）前10天（5月26日）；（c）北跳日（6月5日）；（d）北跳后10天（6月15日）

Figure 12. The composites of 30–60-day band pass filtered wind (units: m s^-1) at 850 hPa and OLR (units: W m^-2) during earlier years of the first jump stage: (a) The twentieth day before the first jump (16 May); (b) the tenth day before the first jump (26 May); (c) the first jump date (5 June); (d) the tenth day after the first jump (15 June)

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图 13 同图 12，但为副高第一次北跳偏晚年：（a）北跳前20天（6月5日）；（b）北跳前10天（6月15日）；（c）北跳日（6月25日）；（d）北跳后10天（7月5日）

Figure 13. As in Fig. 12, but for later years of the first jump: (a) The twentieth day before the first jump (5 June); (b) the tenth day before the first jump (15 June); (c) the first jump date (25 June); (d) the tenth day after the first jump (5 July)

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图 14 副高第一次北跳异常年合成的30~60天滤波区域（0°~10°N，50°E~70°E）平均的OLR（单位：W m^-2）逐日变化曲线。虚线为偏早年合成，实线为偏晚年合成

Figure 14. Daily curves of the composite 30–60-day band pass filtered OLR (units: W m^-2) averaged in the key region (0°–10°N, 50°E–70°E) for the abnormal years of the first jump. The dashed line and the solid line indicate the earlier years and the later years, respectively

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图 15 副高第一次北跳时间与前期（a）3月、（b）4月、（c）5月海温的相关系数分布。阴影：通过95%信度水平检验的区域

Figure 15. Correlation coefficients between the first jump time of WPSH and sea surface temperature (SST) in (a) March, (b) April, (c) May. Shaded areas indicate the correlation coefficients at the 95% confidence level based on the Student's t test

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图 16 副高第二次北跳偏早年合成的北跳阶段30~60天滤波的850 hPa风场（单位：m s^-1）和OLR场（单位：W m^-2）：（a）第二次北跳前20天（6月15日）；（b）北跳前10天（6月25日）；（c）北跳日（7月5日）；（d）北跳后10天（7月15日）

Figure 16. The composites of 30–60-day band pass filtered wind (units: m s^-1) at 850 hPa and OLR (units: W m^-2) during earlier years of the second jump stage: (a) The twentieth day before the second jump (15 June); (b) the tenth day before the second jump (25 June); (c) the second jump date (5 July); (d) the tenth day after the second jump (15 July)

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图 17 同图 16，但为副高第二次北跳偏晚年：（a）第二次北跳前20天（7月20日）；（b）北跳前10天（7月30日）；（c）北跳日（8月9日）；（d）北跳后10天（8月19日）

Figure 17. As in Fig. 16, but for later years of the second jump: (a) The twentieth day before the second jump (20 July); (b) the tenth day before the second jump (30 July); (c) the second jump date (9 August); (d) the tenth day after the second jump (19 August)

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图 18 副高第二次北跳异常年合成的10~20天滤波的关键区（20°N~27.5°N，120°E~135°E）平均的500 hPa位势高度（单位：gpm）逐日变化曲线。虚线为偏早年合成，实线为偏晚年合成

Figure 18. Daily curves of the composite 10–20-day band pass filtered geopotetial height (units: gpm) at 500 hPa averaged in the key region (20°N–27.5°N, 120°E–135°E) for the abnormal years of the second jump. The dashed line and the solid line indicate the earlier years and later years, respectively

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图 19 副高第二次北跳偏晚年合成的10~20天滤波的850 hPa风场（单位：m s^-1）和OLR场（单位：W m^-2）：（a）第二次北跳前15天（7月25日）；（b）第二次北跳前10天（7月30日）；（c）第二次北跳前5天（8月4日）；（d）第二次北跳日（8月9日）

Figure 19. The composites 10–20-day band pass filtered wind (units: m s^-1) at 850 hPa and OLR (units: W m^-2) during later years of the second jump stage: (a) The fifteenth day before the second jump (25 July); (b) the tenth day before the second jump (30 July); (c) the tenth day before the second jump (4 August); (d) the second jump date (9 August)

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表 1 气候态及异常年副高两次北跳时间

Table 1. Climatological and abnormal northward jump time of the western Pacific subtropical high (WPSH)

副高北跳	类型	北跳候（日期）	北跳日
第一次	气候态	34候（6月15~19日）	6月15日
	偏早年	32候（6月5~9日）	6月5日
	偏晚年	36候（6月25~29日）	6月25日
第二次	气候态	42候（7月25~29日）	7月25日
	偏早年	38候（7月5~9日）	7月5日
	偏晚年	45候（8月9~13日）	8月9日

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