海表温度差异对1998及2016年8月西北太平洋热带气旋生成频数的影响

doi:10.12006/j.issn.1673-1719.2018.150

摘要/Abstract

摘要：

基于1970—2016年Hadley中心海温资料、NCEP/NCAR再分析资料和ECHAM4模式,研究了各海盆海表温度异常（SSTA）对1998和2016年这两个超级厄尔尼诺衰减年8月西北太平洋热带气旋（TC）生成及大尺度环流变化的可能影响。结果表明,热带印度洋和大西洋在1998与2016年几乎相反的SSTA型态是导致TC生成频数显著差异的主要原因之一,而热带和北太平洋SSTA在1998与2016年均分别在珠江三角洲和日本以南形成气旋性环流。1998年8月热带印度洋和大西洋SSTA产生的西北太平洋反气旋环流响应强于太平洋SSTA产生的气旋性环流异常,使西北太平洋受异常反气旋控制,减少TC的生成。2016年在三个大洋SSTA共同作用下,西北太平洋受异常气旋控制导致TC生成频数偏多。太平洋经向SSTA模在北半球副热带强迫出东西反向的跷跷板形势,在西北太平洋对流层产生的响应与实际变化相反,因此太平洋经向模对西北太平洋TC生成没有正的贡献。

关键词: 西北太平洋, 热带气旋生成频数（TCGN), 数值模式, 海表温度异常（SSTA）

Abstract:

Based on the Hadley Center sea surface temperature data, NCEP/NCAR reanalysis data from 1970 to 2016 and numerical modeling simulation (ECHAM4), the possible effects of sea surface temperature anomalies (SSTA) in 1998 and 2016, which are the super El Ni?o attenuation years, on tropical cyclone (TC) formation and large-scale circulation in the Western North Pacific in August were studied. It is suggested that the SSTA, which was almost opposite in the tropical Indian Ocean and the Atlantic Ocean in 1998 and 2016, is one of the main reasons for the significant difference in the TC genesis number. Tropical and North Pacific SSTA can exert low pressure cyclonic circulation in the Pearl River Delta and south of Japan respectively in August 1998 and August 2016. The anomalous anti-cyclonic response of the tropical Indian Ocean and Atlantic SSTA in 1998 was stronger than the cyclonic anomaly generated by the Pacific SSTA. Therefore, the Western North Pacific Ocean is subject to anti-cyclonic circulation, which makes the TC genesis number less. In 2016, under the combined action of three oceans, the anomalous cyclone in the Western North Pacific led to more TC genesis number. The Pacific meridional mode structure forced an east-west overturning circulation anomaly in the subtropical North Pacific, and the response over the Western Pacific Ocean was opposite to that observed. Therefore, the Pacific meridional model has no positive contribution to the TC genesis number in the Western North Pacific.

Key words: Western North Pacific, Tropical cyclone genesis number (TCGN), Numerical model, Sea surface temperature anomaly (SSTA)

方珂,余锦华. 海表温度差异对1998及2016年8月西北太平洋热带气旋生成频数的影响[J]. 气候变化研究进展, 2019, 15(2): 119-129.

Ke FANG,Jin-Hua YU. Influence of sea surface temperature difference on the tropical cyclone genesis number in the Western North Pacific in August 1998 and August 2016[J]. Climate Change Research, 2019, 15(2): 119-129.

图/表 9

图1 1997—1998年(a)和2015—2016年(b)各指数变化情况

Fig. 1 Sea surface temperatures averaged indices of 1997-1998 (a) and 2015-2016 (b). The shading represents a period in July-October

表1 1998和2016年7—10月热带气旋频数（TCGN）及其距平

Table 1 The TCGN and its anomalies from July to October in 1998 and 2016

月份	1998年		2016年		平均值（1970—2016年）
月份	原值	距平	原值	距平	平均值（1970—2016年）
7	2	-2.1	4	--0.1	4.1
8	3	-2.1	9	3.9	5.1
9	5	0	5	0	5.0
10	3	-0.7	4	0.3	3.7
7—10	13	-4.9	22	4.1	17.9

图2 1970—2016年8月TC生成位置

Fig. 2 TC generation position in August from 1970 to 2016. The frame is the main generation area of TC

图3 1970—2016年8月TCGN和各环境要素异常的区域（105°E~180°,10°~30°N）平均变化情况

Fig. 3 The TCGN and regional average (105°E-180°, 10°-30°N) of environmental factors at August from 1970 to 2016 (a) TCGN, (b) anomalous relative vorticity at 850 hPa, (c) anomalous relative humidity at 600 hPa, (d) anomalous zonal vertical wind shear between 850-200 hPa. The solid black line represents the average and the black dotted line represents one standard deviation

图4 1998、2016年8月各个环境要素异常的空间分布及TC生成的位置(a,b) 850 hPa相对涡度异常,(c,d) 850 hPa风场异常,(e,f) 600 hPa相对湿度异常,(g,h) 向外长波辐射异常,(i,j) 850~200 hPa纬向风切变异常

Fig. 4 The spatial distribution of environmental factors anomaly and the location of TC generation at August in 1998 and 2016 (a, b) anomalous relative vorticity at 850 hPa, (c, d) anomalous wind vector at 850 hPa, (e, f) anomalous relative humidity at 600 hPa, (g, h) anomalous outgoing long wave radiation, (i, j) anomalous zonal vertical wind shear between 850-200 hPa. The “X” is the position of the TC generation

图5 1998年(a)和2016年(b) 8月SSTA和850 hPa风场异常的空间分布

Fig. 5 Spatial distribution of SSTA (shadow) and anomalous wind vector at 850 hPa in August in 1998 (a) and 2016 (b)

表2 敏感性试验设计

Table 2 Target regions for the numerical experiments

试验名称	范围	异常强迫
1998ALL	0°~360°,30°S~60°N	1998年观测SSTA
2016ALL	0°~360°,30°S~60°N	2016年观测SSTA
1998TIO	40°~110°E,30°S~30°N	1998年观测SSTA
2016TIO	40°~110°E,30°S~30°N	2016年观测SSTA
1998NA	85°W~0°,20°~60°N	1998年观测SSTA
2016NA	85°W~0°,20°~60°N	2016年观测SSTA
1998TA	85°W~15°E,20°S~20°N	1998年观测SSTA
2016TA	85°W~15°E,20°S~20°N	2016年观测SSTA
1998NP	125°E~100°W,20°~60°N	1998年观测SSTA
2016NP	125°E~100°W,20°~60°N	2016年观测SSTA
1998TP	110°E~80°W,20°S~20°N	1998年观测SSTA
2016TP	110°E~80°W,20°S~20°N	2016年观测SSTA
1998PMM-like	175°E~95°W,21°S~32°N	1998年时间系数乘SSTA模态
2016PMM-like	175°E~95°W,21°S~32°N	2016年时间系数乘SSTA模态

表3 8月各环境要素区域（105°E~180°, 10°~30°N）平均响应的ECHAM4模拟结果

Table 3 Response of average environmental factors over the region at 105°E-180°, 10°-30°N from ECHAM model simulation in August

模拟年份	环境要素	ALL	TIO	TA	NA	TP	NP	PMM-like
1998	相对涡度/(10^-6/s)	-2.15	-1.57	-0.82	-0.18	0.45	0.71	0.41
	相对湿度/%	-0.68	-1.62	-0.08	-0.11	2.38	1.79	0.69
	纬向风切变/(m/s)	-0.44	0.66	-0.79	-0.48	-1.11	-1.67	0.18
2016	相对涡度/(10^-6/s)	0.31	0.34	-0.22	0.06	-0.15	0.31	-0.33
	相对湿度/%	1.04	0.89	0.84	-0.19	0.54	0.72	-0.23
	纬向风切变/(m/s)	-1.80	-0.55	-0.41	-0.70	-1.37	-0.24	-1.56

图6 8月北半球环境要素对各海盆SSTA强迫的响应注：灰色等值线为叠加的SSTA（单位：℃),阴影为海平面气压（单位：Pa,仅给出通过95%信度水平),矢量为850 hPa风场（单位：m/s,仅给出通过90%信度水平),红色（绿色）等值线为正值（负值）流函数（单位：107 m2/s,仅给出通过95%信度水平),黑色等值线为位势高度（单位：gpm;d图为200 hPa,f图为500 hPa)。

Fig. 6 Response of environmental factors in the Northern Hemisphere to SSTA of each basin in August. Gray contour is the prescribed SSTA (unit: °C), shading is sea level pressure (unit: Pa, only differences exceeding 95% confident level are shown), vector is 850 hPa wind (unit: m/s, only differences exceeding 90% confident level are shown), red (green) contour is positive (negative) stream function (unit: 107 m2/s, only differences exceeding 95% confident level are shown), the black contour is the geopotential height (unit: gpm; d is 200 hPa, f is 500 hPa)

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