熱帶氣象學(xué)：南海高壓的年代際變化特征及其與我國(guó)華南降水的聯(lián)系

1、2020/10/7,1,南海高壓的年代際變化特征及其與我國(guó)華南降水的聯(lián)系,2020/10/7,2,目錄,引言 資料與方法 南海高壓指數(shù)的定義 南海高壓的年代際變化特征 南海高壓與華南降水的關(guān)系 總結(jié)與討論,引言南海高壓研究進(jìn)展,3,4,引言南海高壓研究進(jìn)展,The South China Sea high (SCSH) generally refers to a closed high pressure system, which appears over the Indo-China Peninsula or the South China Sea (SCS) at the mid-trop

2、osphere. The SCSH, a component of subtropical high systems, frequently appears from September to the following April. Comparison with the subtropical high over the Pacific Ocean shows that the SCSH fluctuates sharply and has a relatively short life cycle. According to the previous studies, the SCSH

3、is closely related with rainfall variability over South China, due to a warm and moist flow located to the northwest of this anticyclone (Liang, 1995).,5,引言南海高壓研究進(jìn)展,Some efforts have been devoted during the past decades into investigating the variation of the SCSH during the boreal summer (e.g. Wang

4、, 1985; Chen, 1998; Lin, 2000; Wan, 2008). Some researches also pointed out that the SCSH is closely associated with summer rainfall. Although some efforts have been made to understand the SCSH variation over the tropics in boreal summer, relatively few studies have focused on its variation in winte

5、rtime, as well as the relationship with the rainfall over South China.,For instance, Wang (1985) defined an intensity index of the SCSH by the point grids where the 500-hPa geopotential height is greater than 5880gpm over the SCS (100E120E, 10N),6,引言南海高壓研究進(jìn)展,Our focus here is on: the definition an a

6、ppropriate occurrence index, so as to better describe the change of SCSH during wintertime at the mid-tropospheric. the relationship between the SCSH and wintertime rainfall over South China possible processes responsible for the formation of South China rainfall based on a vertically integrated moi

7、sture static energy (MSE) equation,7,資料與方法資料出處及方法簡(jiǎn)介,8,資料與方法資料出處及方法簡(jiǎn)介,daily variables derived from the National Centers for Environmental PredictionNational Center for Atmospheric Research (NCEPNCAR) reanalysis data from 1948 to 2010 (NCEP-1; Kalnay et al. 1996); daily precipitation data from of 752

8、weather stations in China from 1959 to 2010, compiled by the Chinese Meteorological Administration; Hadley Centre Sea Ice and Sea Surface Temperature datasets (HadISST; Rayner et al., 2003) ; Composite analysis and empirical orthogonal function (EOF) analysis.,9,南海高壓指數(shù)定義建立指數(shù)10N -22.5N)某格點(diǎn)的八個(gè)方向上的位勢(shì)高度

9、（即周圍16個(gè)格點(diǎn)）均小于該格點(diǎn)，且周圍每個(gè)格點(diǎn)上的渦度小于 -110-5s-1,則認(rèn)為在南海存在閉合高壓?jiǎn)误w； -南海區(qū)域范圍內(nèi)，700hpa高度場(chǎng)上的3135gpm特征線所圍的區(qū)域內(nèi)所有格點(diǎn)數(shù)相加，其值與南海區(qū)域所有格點(diǎn)數(shù)之比需大于0.3； -在區(qū)域（110E-120E、15N-25N）內(nèi)v風(fēng)的區(qū)域平均值需大于0.,11,南海高壓面積指數(shù)： -在110E-120E、10N-20N區(qū)域范圍內(nèi)，700hPa逐日高度圖上3135gpm等高線所圍的網(wǎng)格點(diǎn)數(shù)之和。,南海高壓強(qiáng)度指數(shù)： -南海（中南半島）高壓強(qiáng)度指數(shù)：在110E-120E、10N-20N（95E -110E、10N-20N）區(qū)域范圍內(nèi)

10、，700hPa逐日高度圖上將網(wǎng)格點(diǎn)高度值等于3135gpm的編碼為1,3140gpm的編碼為2余此類推累加所得值。,南海高壓指數(shù)定義建立指數(shù) blue). d Variance spectra of IPO index (black solid curve) and Indian Ocean SST PC1 (red solid curve), and their corresponding 95 % significance levels (dashed lines).,24,南海高壓變化特征年代際變化&成因,圖3.2 1976/77前后冬季500hPa位勢(shì)高度場(chǎng)年代際差值,楚翠姣 2013

11、,25,南海高壓變化特征年代際變化&成因,圖3.3 1976/77前后冬季500hPa位勢(shì)高度場(chǎng)年代際差值 （77年后減77年前），打點(diǎn)地區(qū)為T檢驗(yàn)通過(guò)95%的信度檢驗(yàn)區(qū),全球海溫,北太平洋,太平洋,熱帶印度洋,熱帶西太,熱帶太平洋,熱帶中東,熱帶印太,楚翠姣 2013,26,南海高壓與華南降水聯(lián)系&成因,27,站點(diǎn)選擇： -本文所指的華南地區(qū)包括廣東、廣西、海南三省，剔除建站時(shí)間較晚、缺測(cè)時(shí)間較長(zhǎng)、地理位置偏遠(yuǎn)（如西沙站）等站點(diǎn)后共有50個(gè)站點(diǎn)的逐日降水資料 。,資料長(zhǎng)度： -時(shí)間長(zhǎng)度為1959 年1 月1 日到2011 年11 月31 日，處理為冬半年后共包括52 年。,南海高壓指數(shù)定義建

12、立指數(shù)&強(qiáng)度指數(shù),28,降水率N： -式（4.2.1）表征N 的具體定義，在南海高壓出現(xiàn)當(dāng)天，當(dāng)N10%（即多于5 個(gè)站點(diǎn)有降水記錄），則認(rèn)為該天有降水。,南海高壓指數(shù)定義建立指數(shù)&強(qiáng)度指數(shù),29,南海高壓與華南降水聯(lián)系&成因,Fig. 2. The time series of (upper) the SCSH days (red line) and (bottom) the SCSH indices for 19482010. In upper column, the green line represents the days of SCSH when rainfall rate (N)

13、 is greater than 10%, while the black one represents that when N is greater than 60%. The definition of rainfall rate (N) is seen in section 4.1. In the bottom column, the red line and the green line denote the SCSHI and SCSA, respectively.,90%,51%,30,南海高壓變化特征年代際變化&成因,Q2： 南海高壓的強(qiáng)度、形態(tài)等因素都會(huì)引起華南地區(qū)降水的變化，

14、其主導(dǎo)因素是什么？ Q3： 南海高壓形態(tài)特征與華南地區(qū)降水范圍的聯(lián)系？其物理過(guò)程如何？,31,南海高壓與華南降水聯(lián)系&成因,Fig. 6. Spatial pattern of the rainfall when (a) N60% and (b) N10%.,32,南海高壓與華南降水聯(lián)系&成因,Fig. 7. Spatial pattern of (upper) 700hPa geopotential height (contour, unit: gpm), , (middle) 925hPa horizontal wind and (bottom) vertical integrated w

15、ater vapor flux (vector) for the (left) N60% and (right) N10%. In upper column, 850hPa pressure velocity is shaded. The shading represents that the wind speed is greater than 5 m/s in middle column. In (e) and (f), the shading denotes the corresponding divergence.,33,濕靜力能方程： -,南海高壓指數(shù)定義建立指數(shù)&強(qiáng)度指數(shù),Cite

16、d from: Chou et al. (2009),其中：,34,南海高壓與華南降水聯(lián)系&成因,Fig. 8. Same as Fig. 7, but for the temperature advection, moisture transportation and the net heat flux into the atmosphere column.,35,濕靜力能方程： -,南海高壓指數(shù)定義建立指數(shù)&強(qiáng)度指數(shù),In sum, the shape of the SCSH could significantly influence the rainfall extent over So

17、uth China. the contributions of the temperature and moisture advections to the moist static energy are positive, resulting in extensive rainfall over the South China.,36,總結(jié)與討論,37,總結(jié)與討論,To examine the occurrence of the SCSH, a new definition of the SCSH days is proposed in the present paper. About 20

18、29 days of SCSH were detected during the 63 winters from 1948 to 2010 based on the new establishment index. It is found that this definition could realistically capture the main feature of the SCSH. To investigate the intensity of the SCSH, the intension and area indices are also defined here. Both the two time series show a pronounced upward trend since 1976/77, indicating the interdecadal intensification and extensiveness of the SCSH after the mid-1970s.,38,總結(jié)與討論,Furthermore, the relationship between the SCSH and rainfall over South China is