IMPACT OF THE HEATING OVER SOUTH ASIA UPON THE SUBTROPICAL HIGH OVER WEST-PACIFIC

A case is reported, during which the Subtropical High over the Western Pacific (hereafter, SHWP in abbreviation) shifted northwestward and met-yu at Chaniiang River valley ended. Several numerical experiments onSHWP activity influenced by the heating over south Asia monsoon area are carried out, and the statistic significance of the results is checked. The results indicate that the enhancement of positive heating over South Asia willmotivate a wave-like series of anomaly centers, which propagate northeastward from the maximum heating center.so that a strong positive potential height anomaly center will set up from North China to Japan at Day X resultingin the enhancement of SHWP. Comparison of the influence upon SHWP by the heating over south Asia monsoonarea with that over ITCZ area south to SHWP is also carried out. It is pointed out that the heating over South Asiamonsoon area tends to favor SHWP north\vard movement while the heating over ITCZ area tends to thvor SHWPwestward stretching. As for the time to begin to influence on SHWP, the heating over south Asia monsoon areafavors the enhancement of SHWP atter Day 3 while that over ITCZ south to SHWP effects atter Day 5.

THE POSITION VARIATION OF THE WEST PACIFIC SUBTROPICAL HIGH AND ITS POSSIBLE MECHANISM

Using NCEP/NCAR daily reanalysis data and SCSMEX data, an investigation is carried out of the relationship between the position variation of the west Pacific subtropical high （WPSH） and the apparcnt heating in June 1998 based on the complete vertical vorticlty equation. It is tbund that the non-adiabatic heating plays an important role in the position variation of WPSH. In comparison with climatic mean status, the vertical change of non-adiabatic heating is stronger in the north side of WPSH in June 1998, but weaker in the south side of WPSH. The anomalous non-uniform heating induces anomalous cyclonic vorticity in South China, areas to lhe south of the Yangtze and its mid-lower valleys, but anomalous anticyclonic vorticity in the Indo-China Peninsula and South China Sea areas lead to the more southward position of WPSH than the mean.

COMPARISONS OF THE WEST PACIFIC SUBTROPICAL HIGH AND THE SOUTH ASIA HIGH BETWEEN NCEP/NCAR AND ECMWF REANALYSIS DATASETS

Comparisons of the west Pacific subtropical high with the South Asia High are made using the NCEP/NCAR and ECMWF 500 hPa and 100 hPa monthly boreal geopotential height fields for the period 1961-2000. Discrepancies are found for the time prior to 1980. The west Pacific subtropical high in the NCEP/NCAR data is less intense than in ECMWF data before 1980. The range and strength of the west Pacific subtropical high variation described by the NCEP/NCAR data are larger than those depicted by ECMWF data. The same situation appears in the 100-hPa geopotential field. These discoveries suggest that the interdecadal variation of the two systems as shown by the NCEP/NCAR data may not be true. Besides, the South Asia High center in the NCEP/NCAR data is obviously stronger than in the ECMWF data during the periods 1969, 1979-1991 and 1992-1995. Furthermore, the range is larger from 1992 to 1995.

RELATIONSHIPS BETWEEN THE POSITION VARIATION OF THE WEST PACIFIC SUBTROPICAL HIGH AND THE DIABATIC HEATING DURING PERSISTENT INTENSE RAIN EVENTS IN YANGTZE-HUAIHE RIVERS BASIN

By using NCEP/NCAR daily reanalysis data and daily precipitation data of 740 stations in China, relationships between the position variation of the West Pacific subtropical high (WPSH) and the diabatic heating during persistent and intense rains in the Yangtze-Huaihe Rivers basin are studied. The results show that the position variation of WPSH is closely associated with the diabatic heating. There are strong apparent heating sources and moisture sinks in both the basin (to the north of WPSH) and the north of Bay of Bengal (to the west of WPSH) during persistent and intense rain events. In the basin, Q 1z begins to increase 3 days ahead of intense rainfall, maximizes 2 days later and then reduces gradually, but it changes little after precipitation ends, thus preventing the WPSH from moving northward. In the north of Bay of Bengal, 2 days ahead of strong rainfall over the basin, Q 1z starts to increase and peaks 1 day after the rain occurs, leading to the westward extension of WPSH. Afterwards, Q 1z begins declining and the WPSH makes its eastward retreat accordingly. Based on the complete vertical vorticity equation, in mid-troposphere, the vertical variation of heating in the basin is favorable to the increase of cyclonic vorticity north of WPSH, which counteracts the northward movement of WPSH and favors the persistence of rainbands over the basin. The vertical variation of heating in the north of Bay of Bengal is in favor of the increase of anti-cyclonic vorticity to the west of WPSH, which induces the westward extension of WPSH.

A CHARACTERISTIC CORRELATION ANALYSIS BETWEEN THE ASIA SUMMER MONSOON MEMBERS AND THE WEST PACIFIC SUBTROPICAL HIGH

In this paper, by using the pentad-mean NCAR/NCEP reanalysis data for the period of 1958-1997, some characteristic indices of describing the activity of Asian summer monsoon system members are defined and calculated. Based on the above works, a time-lag correlation analysis method is introduced for the correlation analysis between the Asian summer monsoon system and the west Pacific subtropical high (WPSH) area index, and some meaningful interaction processes and characteristic phenomena between them are revealed and discussed accordingly. It is shown that there exists some remarkable time-lag correlations in various degree between the Asian summer monsoon system members and the WPSH area index, and they interact and feedback with each other, which consists of the whole Asian summer monsoon system.

Characteristics of the Correlation between Regional Water Vapor Transport along with the Convective Action and Variation of the Pacific Subtropical High in 1998

This paper explores the impact of the convective action over the low-latitude region, the water vapor transport around the West Pacific subtropical high (WPSH), and its convective action on the seasonal northward jump and southward withdrawal of the WPSH in summer by using the daily data set of NCEP and TBB for 1998. The research shows that in summer, the WPSH moves northward when the convection over the low-latitude tropical region intensifies and the subsidence region of the meridional vertically vertical circulation in meridional direction circulation over the region of 110?150癊 moves northward. Furthermore, as revealed by diagnostic analysis, the subtropical high moves northward after the obvious weakening of the longitudinal water vapor transport over the region around the subtropical high, but withdraws southward a pentad after the reduction of the latitudinal water vapor transport over the tropical West Pacific region. The research results show that the northward jump and southward withdrawal of the WPSH are closely related to the release of the convective latent heat at low latitudes and the water vapor transport at boundaries around WPSH and its convective action. The numerical simulation further validates the above-mentioned correlation between the variation of the action of the subtropical high and the preceding water vapor transport along with the convection characteristics.

A WAVELET PACKET ENERGY DIAGNOSIS OF SOUTH ASIAN SUMMER MONSOON INFLUENCING ON THE WEST PACIFIC SUBTROPICAL HIGH

Based on the wavelet packet decomposition/reconstruction method and the NCEP/NCAR daily reanalysis data set, the relation between the south Asian summer monsoon and the west Pacific subtropical high seasonal variation was discussed, and a corresponding summer monsoon frequency-band energy criterion was defined and introduced for diagnosing the west Pacific subtropical high. Besides, some existing characteristics and rules about the west Pacific subtropical high were further argued and proofed, a few new phenomena and correlation between the south Asian summer monsoon and the west Pacific subtropical high were also revealed and presented.

ABRUPT CHANGES OF THE WESTERN PACIFIC SUBTROPICAL HIGH AND ITS INTERANNUAL VARIATION DURING LATE SPRING AND EARLY SUMMER

The 500-hPa geopotential height data used in this paper are from NCEP/NCAR data set for the period from 1979 to 1996 (from March to July). Using pentad average, we define the intensity, westernmost ridge point and mean latitude of the subtropical high ridge. Then the wavelet transform and EOF analysis are performed. It is found that there mainly exist three interseasonal abrupt change processes, which correspond to the onset time of the South China Sea Summer Monsoon (SCSSM), the beginning and the end of the Mei-yu respectively. The interannual variation of the subtropical high in late spring and early summer presents quasi-4-year and 8-year periods.

SEASONAL PERSISTENCE OF THE WEST PACIFIC SUBTROPICAL HIGH AND ITS RELATIONSHIP WITH THE SURFACE HEAT FLUX ANOMALY

This paper investigates the interannual variation of the West Pacific Subtropical High(WPSH) intensity based on the data compiled by the Chinese National Climate Center.Monthly reanalysis data from National Centers for Environmental Prediction and National Center for Atmospheric Research(NCEP/NCAR) are also used to study the lead-lag relationship between WPSH intensity and surface heat flux anomalies.The three major findings are as follows:First,WPSH intensity presents good seasonal persistence,especially from winter to the ensuing summer.Persistence is more significant after 1977,especially from spring to summer,and from summer to autumn;persistence of anticyclonic anomalies are significantly better than cyclonic anomalies.Second,surface heat flux tends to present opposite anomalous patterns between the strong and weak years of the WPSH intensity,which is especially valid at the latent heat flux over the ocean.Simultaneous correlations between surface heat flux and WPSH intensity in each of the seasons are marked by similar key areas.Finally,surface heat flux from the preceding winter of a strong summer WPSH is quite similar to strong spring WPSH,but the positive anomalies over the northwest Pacific and south of Japan are notably stronger.The situations in the weak years are similar except for those over the northwest Pacific:winter surface heat flux shows negative anomalies for a weak spring WPSH,but positive anomalies for a weak summer WPSH.It is suggested that surface heat flux in the previous winter plays an important role in maintaining the WPSH intensity in the ensuing spring and summer.

RELATIONSHIP BETWEEN WEST PACIFIC SUBTROPICAL HIGH AND ENSO AND ITS INFLUENCE ON RAINFALL DISTRIBUTION OF RAINY SEASON IN FUJIAN

Relationship between the variations of West Pacific subtropical high indices in the summer half of the year and preceding SST in North Pacific was examined based on a data set of 1951 2000. The correlation between the subtropical high indices and preceding SST in the equatorial East Pacific was the strongest among the others, and has great persistency from last autumn to spring. It is indicated that ENSO events appeared about six months earlier than the change of the subtropical high activities, and the subtropical high intensities enhanced (weakened) and western ridge point was westward (eastward) in the year of El Nino (La Nina) events. It was also observed that there were similar interdecadal oscillation and abrupt variations between Nino3 SST, subtropical high intensities and rainfall of rainy season in Fujian. Therefore, experiments were made on rainfall distribution of rainy season in Fujian. The results showed that the distribution was directly affected by the subtropical high activities, pronouncedly caused by ENSO effect.

MOVEMENT OF THE RIDGE LINE OF SUMMER WEST PACIFIC SUBTROPICAL HIGH AND ITS POSSIBLE MECHANISM

The analysis of the 40-year averaged daily data in this paper suggests that the vertical structure and movement of subtropical high (SH) ridge in summer evidently differ in different areas,which is close related with spatially nonuniform heating.The SH ridge over the West Pacific tilts northwards with height,while one over the Central Pacific tilts southwards.The northward movements of the Central/West Pacific SH ridges both show distinct low frequency oscillations of 10-20 days,and the movement over the East Asian monsoon area shows obvious oscillations of quasi-40-days as well.The analysis shows that the solar radiation drives the seasonal meridional movement of SH,while the spatially nonuniform heating modifies its movement speed and intensity,thus resulting in its anomalous motion.

CMA-CPSv3对夏季南亚高压和西太副高的预测能力评估

为了评估CMA-CPSv3模式对影响我国夏季降水的两个高压系统-南亚高压和西太平洋副热带高压的预测能力,利用该模式2001-2020年3月、5月起报的回报结果和ERA5再分析数据,首先评估了该模式对两个高压系统特征指数的预测能力,然后分析了不同起报时间对东亚地区夏季环流系统的预测能力,最后对比了两个高压系统预测同好年和同差年夏季环流系统、水汽输送特征的差异以及对我国夏季降水的影响,并探讨了两个高压系统预测偏差的可能原因。研究表明:(1)CMA-CPSv3模式对西太副高和南亚高压的平均脊线位置的预测效果最好,预测的强度指数和面积指数明显偏强、偏大;与3月起报相比,5月起报的预测结果对西太副高的预测有一定的提高。(2)CMA-CPSv3模式较好地预测了100 hPa和500hPa环流形势,其中温度场和风场的预测效果较好,但预测的南亚高压和西太副高的范围整体偏强。(3)预测的两个高压系统同好年和同差年,两个高压脊线位置预测较好,预测的面积和强度均明显偏强,同好年的预测偏差较小;能够较好地预测出东亚地区水汽通量的空间分布和我国夏季降水分布格局。(4)预测的两个高压系统所在经度区域的上升运动较ERA5结果偏弱,可能是引起预测的南亚高压和西太副高范围偏大、强度偏强的原因之一。

2007年我国秋季降水异常的成因分析

利用NCEP再分析资料和观测的我国160个台站的降水资料,分析了2007年秋季我国北方地区降水异常偏多的时空特征和大尺度环流特征,重点分析了2007年夏秋季开始的La Nia事件对2007年秋季降水和大气环流的影响。结果表明:2007年我国秋季降水出现了典型北多南少的分布,尤其是9月和10月北方地区降水异常偏多。这段时期内,印缅槽偏强,高原东侧的西南季风异常活跃,加强了来自孟加拉湾和南海的水汽向我国北方地区的输送,同时巴尔喀什湖—贝加尔湖高度场偏低,利于不断分裂的冷空气南下,由于西太平洋副热带高压脊线偏北,使冷暖空气主要交汇在我国北方地区。秋季降水EOF第二模态表现为南北反相的分布,与赤道中东太平洋海温异常有密切关系,解释了我国秋季降水10%以上的方差贡献。2007年我国秋季降水和大气环流都表现出了典型La Nia事件影响的特征。

重庆近48年来高温天气气候特征及其环流形势

利用重庆23个气象观测站196042007年逐日最高气温观测资料，NCEP／NCAR再分析数据集中的高度场格点资料，运用EOF、REOF等方法，探讨重庆高温日数的空间分布特征，并对多高温天气的2006年和少高温天气年748月的环流特征进行了分析。结果表明：重庆高温天气主要出现在7～8月份，高温日数具有显著的年代际和区域性差异，20世纪70年代最多，80年代最少，沿长江、乌江为高温多发带。一致性异常分布是重庆高温日数的最主要空间模态；高温日数的异常空间分布可分为以下3个关键区：重庆中西部、重庆东南部、重庆东北部。乌拉尔山至鄂霍次克海地区阻塞高压偏弱，东亚大槽偏浅；100hPa高空南亚高压偏东，500hPa高空副高偏北偏西，形成一种上高下高的叠加形势是重庆7～8月出现多高温天气的主要原因。

四川盆地夏季水汽输送特征及其对旱涝的影响

利用1981—2000年夏季观测资料,分析了四川盆地夏季平均的水汽输送状况及四川盆地典型旱涝年的水汽输送差异特征,并在此基础上,初步分析了四川盆地旱涝异常的大气环流背景。结果表明:四川盆地的夏季水汽主要来源于青藏高原、孟加拉湾及南海地区。当西太平洋副热带高压偏北偏西时,其外侧东南风可以把南海水汽带到盆地西部,孟加拉湾及青藏高原水汽受到阻挡被迫停留在盆地西部,形成了盆地西部异常的水汽辐合,东部异常的水汽辐散,由此导致四川盆地西涝东旱。反之,当西太平洋副热带高压偏南偏东时,其西南侧的南海水汽不能到达盆地西部,只能到达盆地东南部,而孟加拉湾及青藏高原水汽则可以进入盆地东部,在盆地东部形成异常的水汽辐合,在西部形成异常的水汽辐散,造成四川盆地西旱东涝。

西太平洋副高与ENSO的关系及其对福建雨季降水分布的影响

利用1951～2000年北太平洋海温和副高特征量资料,探讨夏半年副高与前期海温的关系,发现影响副高活动的海温关键区赤道东太平洋前期信息最明显,从前期秋季持续至春季都保持与夏半年各月副高强度、西伸脊点位置的高相关;ENSO事件的形成超前于副高强度的转折约半年时间;El Nino年副高持续偏强偏西,La Nina年则相反,脊线位置也有所反映,但不如强度与西伸显著。在此基础上进一步分析表明,福建雨季降水、副高强度与Nino 3区海温存在着大约相一致的年代际振荡与突变时间;雨季降水分布的异常直接受到副高活动的影响,而副高活动又明显受ENSO循环的制约,因而关注赤道东太平洋海温异常及ENSO信息对福建雨季降水分布趋势的预测具有重要意义。

2004年北半球大气环流及对中国气候异常的影响

20 0 4年上半年,赤道中、东太平洋大气、海洋状况总体上处于正常状态。7月以来,赤道中、东太平洋海表温度明显增暖;2 0 0 4年西太平洋副热带高压持续偏强,夏季西伸脊点位置偏东、脊线位置偏北;6月上中旬贝加尔湖以西地区50 0hPa高度场偏高,7月中旬和8月中旬贝加尔湖地区高度场偏高;2 0 0 4年南海季风爆发时间接近常年,南亚夏季风偏强;青藏高原50 0hPa高度场偏高,冬季积雪较常年稍偏多;2 0 0 4年上半年,赤道太平洋对流活动普遍受到抑制,7月后期开始,1 6 0°W以西海域上空对流活动较常年明显增强。2 0 0 4年中国气候异常可能是下垫面热力异常和大气环流异常共同作用的结果。

夏季青藏高原移动性对流系统与中国东部降水的相关关系

利用国际卫星云气候计划提供的1985—2002年共18年的MCSs路径跟踪资料、NCEP/NCAR逐月再分析资料和中国138个地面常规观测站资料,分析了夏季起源于青藏高原地区的移动性MCSs的主要时空分布特征,探讨了青藏高原MCSs与中国降水的关系。通过对MCSs爆发异常强弱年高度和风差值场的分析,概括出青藏高原MCSs影响中国降水的可能机制。结果表明:夏季青藏高原移动性MCSs主要生成于青藏高原东南部,其爆发时间具有明显的日变化特征,它们能够传播到我国中东部及南亚许多地区;夏季MCSs对我国降水具有重要影响,它们与中国夏季降水的相关系数分布以4条正、负相间的东西向分布带的形势存在,从南到北依次为"-+-+",这与我国夏季降水带的变化形势非常一致;南亚高压、西太平洋副热带高压和东北冷涡的强度、位置变化与高原MCSs生成的多少密切相关,并通过它们对我国夏季降水带的分布造成重要影响。

重庆春季连阴雨的气候特征和气候信号分析

利用1961—2012年3—5月NCEP/NCAR再分析资料、NOAA的海温、重庆34个站气象资料和74项环流特征指数,分析了重庆春季连阴雨的时空变化特征及其与同期的大气环流、西太平洋副热带高压(西太副高)、前期冬季的海温、OLR、大气环流以及西太副高之间的关系。结果表明:重庆春季连阴雨有发生频率高的特征,3月最容易发生影响范围广,持续时间长的连阴雨,其次是5月。连阴雨明显的时段重庆受影响的范围广,持续时间较长,气温偏低。东北部和西部地区出现频次较低,东南部较高。连阴雨分布主要为全市一致型和东西相反型。春季巴伦支海地区和青藏高原的500 hPa高度场偏低,贝加尔湖以东地区偏高,欧亚中高纬环流形势有利于冷空气南下和西太副高的减弱东退是重庆的连阴雨发生的主要因素。冬季拉尼娜事件的发生、赤道150°E地区的对流加强和鄂霍次克海地区中高层大气高压脊的建立都有利于来年春季重庆连阴雨的发生。

OLR资料描述西太平洋副热带高压的一种方法

文介绍了用OLR场表达逐日西太平洋副热带高压的一种方法 ,并指出用这种表达能够克服用 588dagpm等高线勾划副热带高压单体的失真现象。