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[机构公布] 2011年西北太平洋热带气旋活动的预测验证和

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匿名  发表于 2012-8-9 20:09 |阅读模式
Verification of Forecasts of Tropical Cyclone Activity over the Western North Pacific and
Number of Tropical Cyclones Making Landfall in South China and the Korea and Japan region
in 2011
2011年西北太平洋热带气旋活动的预测验证和
在南中国、韩国和日本地区登陆的热带气旋数目
1.     Introduction
1.简介

Since 2000, City University of Hong Kong has been issuing real-time predictions of the annual number of tropical cyclones (TCs) affecting the western North Pacific (WNP).  Verifications of the predictions have shown that the predictions are mostly correct within the error bars.  We also began to predict the number of TCs making landfall in South China (SC) and the <st1:country-region w:st="on">Korea and <st1:country-region w:st="on">Japan region (KJ) in 2009 and 2010 respectively.
自2000年以来,香港城市大学一直公布西北太平洋(WNP)每年热带气旋影响数量(TCS)的实时预测。该预测的验证表明大多预测是正确的,在误差允许的范围内。我们也分别开始预测2009年和2010年在中国南方(SC)、韩国和日本地区(KJ)热带气旋登陆的数量。

These are all statistical predictions with predictors drawn from a large group of indices that represent the atmospheric and oceanographic conditions in the previous year up to the spring of the current year.  The most prominent ones include the proxies for El Ni&ntilde;o/Southern Oscillation (ENSO), the extent of the subtropical ridge, and the intensity of the India-Burma trough.  Details can be found in Chan et al. (1998, 2001), and Goh and Chan (2010a, b).
这些都是根据在过去一年到本年度春季的各种大气和海洋条件指数,组算得出的统计预测。最突出的包括厄尔尼诺/南方涛动(ENSO)的变量、副热带高压脊的程度以及印缅槽的强度。详情可在Chan等人(1998年,2001年)以及Goh 和 Chan(2010a,b)。

a. Summary of the forecasts issued
a.发布的预测概要

TC activity over the WNP
1)西北太平洋的TC活动

Our April forecasts issued on 09 May 2011 suggested “near-normal activity for all the categories”.  The June forecasts (issued on 04 July 2011) gave a similar forecast.  Detailed numbers are summarized in Table 1, together with the observed numbers based on the warnings from JTWC and the Tokyo Regional Specialised Meteorological Center (RSMC) (Table 2).
我们四月的预测在2011年5月09日发布,提出“所有类别的TC活动接近正常”。 六月的预测(2011年7月04日发布)发表了类似的预测。详细的数字概要在表1, JTWC和东京的区域专门气象中心(RSMC)根据观测到的数字发出的警告(见表2)。

Disagreement occurred among the warning centres on the intensity of one of the systems.  Tokage was considered by RSMC Tokyo as having reached tropical storm intensity but not by JTWC.
预警中心之间对其中一个系统的强度发生分歧。Tokage(蝎虎)被东京RSMC视为已达到热带风暴强度,但JTWC并不认为。

South China
2)中国南方

The April forecast called for an above normal number of TCs making landfall along the South China coast in the early season (May to August), a normal number in the late season (September to December), and an above normal number overall.  The forecast issued in June also suggested the number of landfalling TCs to be above normal for the main season (July to December).  Table 1 shows a summary of these forecasts, along with the observed number in 2011 and the normal values.
4月份的预测提出,在风季初(五月至八月)沿中国南方沿海登陆的热带气旋高于正常数量,风季晚期(九月至十二月)为正常数量,总体上高于正常数量。六月发表的预测还提出旺季(七月至十二月)登陆的热带气旋数量高于正常。随着2011年观测到的数量和正常值,这些预测的概要显示在表1。

Korea and Japan region
3)韩国和日本地区

  The April forecast called for an above normal number of TCs making landfall in the <st1:country-region w:st="on">Korea and <st1:country-region w:st="on">Japan region for the whole TC season.  The June forecast further raised the TC number for the main season (July to December). Table 1 is a summary of the predictions made.
4月份的预测提出,整个TC季节在韩国和日本地区登陆的热带气旋数目高于正常。 6月份的预测,进一步提升了旺季的(七月至十二月)TC数。表1是预测的概要。

b. Verification and discussion

b.验证与讨论
1) TC activity over the WNP
1)西北太平洋的TC活动
The TC activity over the WNP in 2011 was below normal.  Based on the JTWC warnings, the number of TCs with at least tropical storm intensity is 20 (Table 2), which is 7 less than the normal number (the normal being 27) (see also Fig. 1).  The typhoon activity is also below normal, with 10 typhoons which is 7 less than the normal number (the normal being 17).  Our forecasts from both April and June over-predicted the TC activity and the possible reasons of which are discussed below.
西北太平洋2011年TC活动低于正常。根据JTWC的警告,热带风暴强度的热带气旋数目至少是20个(表2),这比正常(正常是27)少7个(参见图1)。台风活动也低于正常值,有10个台风,比正常数量少7个(正常为17个)。我们的预测来自四月和六月预测到的TC活动,其中可能的原因将在下面讨论。

As pointed out in the April forecast, the TC activity over the WNP appears to enter an inactive period since 1998.  In the last 13 years, only two years (2001 and 2004) have the above-normal TC activity and the activity in most of the other years is below normal.  Indeed, the inactive TC period 1998–2010 appeared to continue into 2011 and the number of tropical storms and typhoons in 2011 is below the climatological mean, which is the 12th out of the last 14 years since 1998 with a below-normal TC activity.  Because this downward trend was not included in the prediction scheme, the predictions for 2011 suffer from the same problem as in the last few years in that they are all over-predictions.
4月份的预测已指出,自1998年以来,西北太平洋出现的TC活动进入非活跃期。在过去的13年中,只有两年(2001年和2004年)的TC活动高于正常,大多数的年份TC活动低于正常值。事实上,2011年延续了1998年至2010年的TC不活跃期, 2011年的热带风暴和台风的数量低于气候平均值,这也是1998年以来,过去14年中的第12个TC活动年份低于正常。由于在预测方案中并没有包括这种下降趋势,2011年的预测遭受同样的问题,在过去的几年中,他们都超过预测的数量。

The La Ni&ntilde;a event developed in 2010 weakened in the spring of 2011 but redeveloped in the summer.  The mean Jun-Nov Ni&ntilde;o3.4 index is -0.64, indicating a weak La Ni&ntilde;a event in this period.  The changes in atmospheric circulation associated with the La Ni&ntilde;a event might be the factor affecting the TC activity.  Previous studies suggest that in a La Ni&ntilde;a year, easterly anomalies are generally found over the tropical WNP, resulting in the weakening of the monsoon trough and hence a lower TC activity (Wang and Chan 2002) (Table 3).  In the 2011 TC season, strong easterly anomalies are found over the entire tropical WNP, with the maximum amplitude between 150[sup]o[/sup]E and 180[sup]o[/sup]E (Fig. 2).  As a result, the monsoon trough is much weaker than normal in the eastern part of the WNP.  At the same time, the June-October vertical wind shear pattern shows positive anomalies over the subtropical WNP east of 150[sup]o[/sup]E, indicating a stronger than normal vertical wind shear in this region (Fig. 3).  Hence, the atmospheric conditions are therefore not favourable for TC genesis and development especially for the eastern part of the WNP.  Indeed, the mean genesis location shifted westward and only three TCs formed over the tropical WNP east of 150[sup]o[/sup]E, which is the typical pattern associated with a La Ni&ntilde;a event.
2010年开始的拉尼娜现象在2011年春季减弱,但在夏季重建。Ni&ntilde;o3.4的6 -11月平均指数为-0.64,表明此期间弱的拉尼娜现象。与拉尼娜现象有关的大气环流变化可能是TC活动的影响因素。以往的研究表明,在拉尼娜年,热带西北太平洋通常都发现东风距平,导致季风槽削弱,因此TC活动较低(王和陈2002年)(   见表3)。2011年的TC季节,整个热带西北太平洋被发现强劲的东风距平,最大振幅在150°E和180°E(图2)之间。因此,西北太平洋东部的季风槽比正常弱得多。与此同时,西北太平洋副热带高压位于150°E以东, 显示6-10月的垂直风切变模式正距平,表明这一地区(图3)比正常的垂直风切变强。因此,大气条件不利于TC的发生和发展,尤其是西北太平洋东部的部分。事实上,平均的成因位置西移,只有三个热带气旋形成于150°E以东的西北太平洋热带,这是与拉尼娜现象有关的典型模式。

2) South China
2)中国南方

The observed number of TCs making landfall along the coast of region South China was 3 in the early season, 2 in the late season, 3 in the main season, and 5 in the whole season. Apart from the prediction for the late season, which was perfect, the predictions for the number of landfalling TCs in the early and main seasons were overestimated, which also led to an overestimation of the predicted value for the whole season.
风季早期沿中国南方沿海登陆的热带气旋观测数是3个,季节后期2个,整个季节5个,其中旺季3个。除对晚季的预测外,这是完美的,在早期和旺季登陆的热带气旋数量预测被高估,这也导致了整个季节的预测值高估。

The number of TCs making landfall along the coast of South China depends on the TC activity over the WNP and the South China Sea (SCS) and the changes in the large-scale steering flow.  The 500-hPa wind pattern in the early season shows that the anomalous zonal winds are small in the subtropical WNP west of 140°E (Fig. 4a).  The changes in steering flow are not obvious in this region and the landfalling activity is therefore near normal in the early season.  Thus, our April forecast over-estimated the number of landfalling TCs in the early season.  The pattern for the main season shows westerly anomalies between 10°N and 20°N (Fig. 4b), which tend to steer TCs away from the SCS.  Together with the below-normal overall TC activity over the WNP, fewer TCs entered the SCS from east of the Philippines and came close to the South China coast.  In addition, the number of TCs formed over the SCS was also below the climatological mean.  Thus, the number of landfalling TCs in the main season was below normal, which was lower than the predicted number from the June forecast.
沿中国南方沿海登陆的热带气旋数目取决于西北太平洋和中国南海(SCS)的TC活动以及大规模引导环流的变化。在风季初的500 hPa风场模式显示140°E以西的西北太平洋副热带高压(图4a)纬向风距平较小。引导环流的变化并不明显,因此本地区在风季初登陆的活动接近正常。所以,我们4月份的预测高估了风季初的热带气旋登陆数量。对于旺季的模式显示出10°N和20°N(图4b)之间西风异常,这往往引导热带气旋远离南海。再加上西北太平洋的总体TC活动低于正常,热带气旋从菲律宾以东进入南海并靠近中国南方沿海的数量更少。此外,形成于南海的热带气旋数目也低于气候平均值。因此,在旺季登陆的热带气旋数量也低于正常值,这低于6月份预测的预测数目。

3) Korea and Japan region
3)韩国和日本地区

The observed number of TCs making landfall in the Korea and Japan region was 5 in the main season and 7 in the whole season.   Our forecasts from both April and June correctly predicted the above-normal landfalling activity in the main and whole seasons (Table 1).  However, the June forecast slightly over-estimated the number of landfalling TCs in the main season.
在韩国和日本地区登陆的TCS观察数目在主季是5和整个风季是7。我们从四月及六月的预测中正确地预见旺季及整个季节的登陆活动高于正常(见表1)。然而,旺季登陆的热带气旋数目略高于6月份的预测。

As stated in the April forecast, our prediction for the above-normal number is based on the possible anomalous low at 500-hPa south of Japan in the peak season (July to September).  Indeed, an anomalous low is found just south of Japan in the peak season, resulting in a break in subtropical high near this region (Fig. 5).  Thus, more TCs recurved and entered the Korea and Japan region, which partly explain the above-normal TC landfalling activity.
4月份的预测指出,我们预测的数量高于正常是基于旺季(七月至九月)在日本南部的500百帕可能异常薄弱。事实上,在旺季日本以南发现异常薄弱,导致该地区附近的副热带高压断裂(图5)。因此,更多的热带气旋转向并进入了韩国和日本地区,这部分阐释了TC登陆活动高于正常。

References
参考文献
Chan, J. C. L., J. E. Shi and C. M. Lam, 1998: Seasonal forecasting of tropical cyclone activity over the western North Pacific and the  South China Sea. Weather Forecasting, 13, 997-1004.
Chan, J. C. L., J. E. Shi and K. S. Liu, 2001: Improvements in the seasonal forecasting of tropical cyclone activity over the western North Pacific. Weather Forecasting, 16, 491-498.

Goh, A. Z. C., and J. C. L. Chan, 2010a: An Improved Statistical Scheme for the Prediction of Tropical Cyclones Making Landfall in South China. Weather and Forecasting, 25, 587-593.
Goh, A. Z. C., and J. C. L. Chan, 2010b: Variations and Prediction of the Annual Number of Tropical Cyclone Affecting <st1:country-region w:st="on">Korea and <st1:country-region w:st="on">Japan. International Journal of Climatology, DOI: 10.1002/joc.2258.
Wang, B. and Chan, J. C. L., 2002: How strong ENSO events affect tropical storm activity over the western North Pacific. J. Climate, 15, 1643-1658.
        

Table 1.  Forecasts of TC activity in 2011 issued in April and June.  The observed activity based on both the JTWC and RSMC-Tokyo warnings and the normal values are also shown.
表1。在2011年四月及六月发布的2011年热带气旋活动的预测。观测到的活动根据JTWC和东京RSMC的警告,同时还列出正常值。
2011预测值观测值正常值
 46 JTWCRSMC 
西北太平洋
TCS的数目313127---31
至少是热带风暴强度的热带气旋数目2727202127
台风数目1615101017
在中国南方登陆数
早季(5-8月)5---3---3
晚季(9-12月)2---2---2
旺季(6-12月)---73---4
整个季节(5-12月)6---5---5
在韩国及日本地区登陆数
旺季(7-9月)---75---3
整个季节(5-12月)6---7---4

      
Table 2. 2011 summary of tropical cyclones over the western North Pacific and tropical cyclones making landfall in South China and the Korea and Japan region.
表2。2011年通过西北太平洋,在中国南方、韩国和日本地区登陆的热带气旋总结。
 热带气旋至少是热带风暴强度的热带气旋有台风强度的热带气旋在中国南方登陆的热带气旋在韩国和日本地区登陆的热带气旋
 01. 01W01. Aere01. Songda01. Sarika01. Songda
02. 02W02. Songda02. Ma-on02. Haima02. Meari
03. Aere03. Sarika03. Nock-ten03. Nock-ten03. Ma-on
04. Songda04. Haima04. Muifa04. Nesat04. Muifa
05. Sarika05. Meari05. Merbok05. Nalgae05. Talas
06. Haima06. Ma-on06. Nanmadol 06. Kulap
07. Meari07. Nock-ten07. Roke 07. Roke
08. Ma-on08. Muifa08. Sonca  
09. Tokage*09. Merbok09. Nesat  
10. Nock-ten10. Nanmadol10. Nalgae  
11. Muifa11. Talas   
12. Merbok12. Noru   
13. 13W13. Kulap   
14. Nanmadol14. Roke   
15. Talas15. Sonca   
16. Noru16. Nesat   
17. Kulap17. Haitang   
18. Roke18. Nalgae   
19. Sonca19. Banyan   
20. Nesat20. Washi   
21. Haitang    
22. Nalgae    
23. Banyan    
24. 24W    
25. 25W    
26. 26W    
27. Washi    
总数27 (JTWC)20 (JTWC) /10 (JTWC) /57
21 (RSMC)10 (RSMC)
预测数目(4月发布)     
312716
预测数目(6月发布)     
312715
*蝎虎被东京RSMC视为已达到热带风暴强度,但JTWC没有认可  
        

Table 3.  Number of tropical storms and typhoons and number of typhoons in an La Ni&ntilde;a year.  Green and blue shadings indicate the above-normal and below-normal TC activity respectively.
表3。热带风暴和台风的数量以及拉尼娜年台风数量。绿色阴影表示TC活动高于正常,蓝色阴影表示TC活动低于正常。
拉尼娜年
热带风暴和台风的数目
台风的数目
活跃期
1964
39
26
1970
24
12
1971
35
24
1973
21
12
1974
32
15
1975
20
14
1995
26
15
非活跃期
1984
27
16
1988
26
14
1998
17
9
1999
24
12
2000
25
15
2007
23
15
2010
14
8
2011
20
10
        

2011_ver_Fig1.png
Fig. 1.  Annual number of tropical storms and typhoons between 1960 and 2011. The horizontal line indicates the climatological mean.  Red circle and blue squares indicate the El Ni&ntilde;o and La Ni&ntilde;a years respectively.
图1。1960年和2011年之间热带风暴和台风的每年数量。水平线表明气候平均值。红色圆圈表明厄尔尼诺,蓝色正方形表明拉尼娜年。
        

2011_ver_Fig2.png
Fig. 2.  850-hPa wind anomalies (vector) between June and October in 2011.  Shadings indicate the zonal wind speed (interval = 1.0 m s[sup]-1[/sup]).
图2。2011年6月和10月之间的850 hPa风场距平(向量)。阴影表示纬向风速(间距= 1.0 m s[sup]-1[/sup])。
        


2011_ver_Fig3.png
Fig. 3. 850-200-hPa vertical wind shear anomalies between June and October in 2011.
图3。2011年6月和10月之间的850-200百帕垂直风剪切距平。
        


2011_ver_Fig4.png
Fig. 4.  500-hPa wind anomalies (vector) in the (a) early and (b) main seasons for 2011.  Shadings indicate the zonal wind speed (interval = 1.0 m s[sup]-1[/sup]).
图4。2011年(a)早期和(b)旺季的500百帕风距平(向量)。阴影表示纬向风速(间距= 1.0 m s[sup]-1[/sup])。
        

2011_ver_Fig5.png
Fig. 5.  500-hPa geopotential height anomalies between July and September in 2011.  Thick contours indicate the geopotential height (contour interval = 10 m) ≥ 5860 m.
图5。2011年7月至9月间的500 hPa位势高度距平。厚厚的轮廓显示位势高度(等值线间距= 10米)≥5860米。

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表3。热带风暴和台风的数量以及拉尼娜年台风数量。绿色阴影表示TC活动高于正常,蓝色阴影表示TC活动低于正常。

绿色阴影?蓝色阴影?
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 楼主| 发表于 2012-8-9 20:38 | 显示全部楼层

回 loppyname 的帖子

loppyname:表3。热带风暴和台风的数量以及拉尼娜年台风数量。绿色阴影表示TC活动高于正常,蓝色阴影表示TC活动低于正常。

绿色阴影?蓝色阴影? (2012-08-09 20:30)
发图搞不好
帖子中涉及地图来源广泛,图中所涉及的行政区域以中国官方认定的为准。
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 楼主| 发表于 2012-8-9 20:41 | 显示全部楼层
 拉尼娜年热带风暴和台风的数目台风的数目
活跃期19643926
19702412
19713524
19732112
19743215
19752014
19952615
非活跃期19842716
19882614
1998179
19992412
20002515
20072315
2010148
20112010

表3
帖子中涉及地图来源广泛,图中所涉及的行政区域以中国官方认定的为准。
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