CONTRAST ANALYSIS OF APRIL TYPHOONS LEO AND NEOGURI CONTRAST ANALYSIS OF APRIL TYPHOONS LEO AND NEOGURI

CONTRAST ANALYSIS OF APRIL TYPHOONS LEO AND NEOGURI

  • 期刊名字:热带气象学报(英文版)
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  • 论文作者:LU Shan,WU Nai-geng
  • 作者单位:Guangzhou Central Meteorological Observatory
  • 更新时间:2020-12-06
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Vol.17 No.4JOURNAL oF TROPICAL METEOROLOGYDecember 2011Article ID: 1006-8775(201 1) 04-0409-09CONTRAST ANALYSIS OF APRIL TYPHOONS LEO AND NEOGURILU Shan(卢山), WU Nai- geng (吴乃庚)(Guangzhou Central Meteorological Observatory, Guangzhou 510080 China).Abstract: The conventional observations data, NCARNCEP-2 reanalysis data, and NOAA outgoinglongwave radiation data are used to investigate different characteristics of Leo and Neoguri, two Apriltyphoons that ever made landfall on the continent of China over the past 60 years. The results showed thatboth Leo and Neoguri occurred during the La Nina events. Strong convective activity, weak vertical windshear and upper-level divergence were in favor of the formation of these April typhoons. Leo originatedfrom a monsoon depression and Neoguri evolved from an easterly wave. The meandering moving track ofLeo atributed to strong northeast monsoon and a weak and changeable subtropical high; the steady movingtrack of Neoguri was govemed by a strong and stable subtropical high. Leo and Neoguri had similar terrainconditions and intensities during landfall but were different in precipitation as water vapor transport andduration of kinetic uplifting resulted in apparent discrepancies between them.Key words: April typboons; formation mechanisms; moving track; typhoon precipitationCLC number: P444Document code: Adoi: 10.3969/j.issn.1006-8775.201 1.04.0111 INTRODUCTIONSimulating the strengthening mechanism of the SCSTropical cyclones (TCs) are the synoptic systermsTCs just off the coast in prime summer, Chen et al.013showed that waving motion within the interiorthat are most destructive of meteorological disasters.structure of a TC that bears some similarity to theBeing able to generate thyearround, theyRossby wave is making important contribution to theconcentrate in July- October1-3]. By long-time practice,offshore intensifying mechanism of TCs in the SCS.summing-up, exploration and research, meteorologistsAnalyzing the development of the SCS TCs with thehave done much on TCs' generation mechanisms,Outgoing Longwave Radiation (OLR) data, Luo etchanges in structure and motion, landfalling processes,al.!4J defined an index of gradient variations of OLRheavy rainfall they bring about as well as forecastingcontours to describe its relationships with thetechniquest 10. Chen has made comprehensivedevelopment of tropical depressions in the SCS.overviews and summaries on the progress made overAlthough some significant achievements have beenthe past few years in China in TC research!3One of the waters most frequented by TC activity,made on the research on TCs in the SCS, they arethe South China Sea (referred as ScS hereafter) canmostly about their behavior in summer and the yearlysecond rainy season in the south of China. In spring,have TCs the year round. Much effort has been spentTCs appear in the SCS with small frequencies and lowon the characteristics of the SCS TCsIn theirintensities, and more than half of them migrate fromstudies on the spatiotemporal distribution of the TCsthe Philippine Sea. It is known from surveys throughactive during June- October in the SCS over the pasthistorical data that there are only two TCs in April,50 years, Li et al.!" pointed out that chief maritimeone being Leo (coded 9902) and the other Neogurifactors affecting the frequency of TCs in the SCS are(0801), in the period from 1949 up to the present, thatrelated to the EI Nito Southern Oscillation (ENSO).formed over the SCS and made landfall in China. InMay through September is an active season for themid-April, Neoguri became the earliest typhoon everSCS TCs, with September having. the highestsince 1949 that generated over the SCS and landed onfrequency, as indicated in Yang et al."4 studying theChina later. As it is quite difficult to analyze andpatterm of cyclogenesis of these TCs for 1949- -2003.forecast this type of TCs and to advise onReceived 2010-06 25; Revised 2011-07-20; Accepted 2011-10-15Foundation item: Research on Techniques of Forecasting and Pre-warming Typhoons Landing on or SeriouslyAffecting Guangdong, a Project of Guangdong Science and Technology Bureau 20072060401016) NathrolScience Foundation of China (40730951)中国煤化工Biograpby: LU Shan, senior engineer, primarily undertaking research on and forMHCNMHGCorresponding author: LU Shan, e-mail: shan. lu@grmc.gov.cnNo.4LU Shan(卢山) and WU Nai-geng (吴乃庚)415followed a simpler path because of an intense andcycle amount at 127.4 mm at Puning observation site)stable subtropical high pressure that dominated it:while Neoguri was associated with heavy-rain level ofmovement (Fig. 8).precipitation (with maximum cycle amount at 314.0mm at Chaoyang observation site).30NAs Leo and Neoguri landed where heavy rainusually occurs, similarities exist in their topographica)25Nconditions of mountain ranges and amplifying effectof the underlying surface on typhoon-spawned heavyrain. Therefore, dynamic lifing and water vapour will20Nbe our focus of analysis.204PR5.1 Comparison and analysis of vertical motion and15Nconvergence/divergenceFigure 9 gives the altitude-time evolutions of10Nregionally averaged vertical velocity and divergence.Substantial dynamic differences are found prior to andafter the landfall of Leo and Neoguri. The two5|typhoons were examined in terms of the value andheight of the centre of vertical velocity. For Leo, -0.15Pa/s distributes in a range of 800 -600 hPa with the100E105E110E115E120E125E130E135E 140E centre value, -0.18 Pa/s, at the level of 700 hPa, andintense ascending motion occurs just one day before30N .landfall. For Neoguri, -0.15 Pa/s spreads over a rangeb)of 900- 400 hPa with the centre value, -0.21 Pa/s,appearing at the height of 650 hPa, and intense25N .ascending motion maintains more than two days. BothLeo and Neoguri are marked with low-level20N 'convergence and upper-level divergence, though withthe convergent layer of Leo extended to as high asL2owR600 hPa while that of Neoguri only to 800 hPa. On the15N-other hand, Neoguri, due to upper-level divergence,184PR-had a stronger sucking effect than Leo. Thecomparisons of dynamic conditions indicated thatNeoguri is much more advantageous than Leo as faras the background for heavy precipitation isconcerned.5N5.2 Comparison and analysis of water vapour“TOOE 105E110E115E120E125E130E135E140EAbundant water vapour is particularly importantFig. 8. 5870-gpm contours at 500 hPa for April 27- May 2,to the formation and persistent development of the1999 (a) and Apil 15- 20, 2008 (b).severe precipitation brought about by tropicalcyclones3,4. Comparisons of water vapour flux fields5 COMPARISONS OF THE PRECIPITATIONat 850, 700, and 500 hPa showed that water vapour,BETWEEN LEO AND NEOGURIaround the point of landfall, is more favourable withNeoguri than with Leo, a result indicated byBy the time of landfall, both Leo and Neoguri hadexamining either the source or the amount of waterreduced to the category of tropical depression withvapour transport (Figure omitted). At landfall,compromised core structure, making them possessNeoguri had two belts of water vapour transport, thesimilar intensity at landfall. After landfall, they bothsouthwest branch of airflow from the Bay of Bengalmoved into the westerly zone and followed ato the coastal southern China and a southerly airflownortheast track. The two storms were much alike withover the SCS, which formed a centre of water vapourregard to the environmental flow field prior to andflux over“中国煤化工8axis runsafter landfall, such as the location and shape of theWSW-ENE) at the core,subtropical high, low-latitude troughs and ridges, andwith the maxiTYHCNMHGg/(cmhPas).the wind field, but differ dramatically in the rainfallWith the slow advancement of the centre withamount they brought about. Leo was associated withNeoguri over to the eastem part of Guangdong, waterrainfall on the scale of heavy rain (with maximumvapour flux began to decrease on April 21. The case.No.4LU Shan(卢山and WU Nai-geng (吴乃庚)417[]. Acta Meteor. Sinica, 2001, 59(4): 429 -439.81-87.[7] FIORINO, ELSBERRY R L. Some aspects of vortex[15] LU Shan, WU Nai-geng, XUE Zhi-deng. Research on thestructure related to tropical cyclone motion []. J. Atmos, Sci,enhancement of tropical cyclone rainstorm influenced by1989, 46: 975-990.monsoon trough of South China Sea [J Meteor, Mon, 2008,[8] YUAN Jin-nan, WAN Qi-lin, HUANG Yan-yan, et al. The34(6): 53-59.experiments of ensemble prediction of the track of tropical[16] WU Nai-geng, LIN Liang-xun, LI Tian-ran, et al.cyclone in South China Sea [J]. J. Trop. Mcteor, 2006, 22(2):Diagnosis of northward-deflecting track of typhoon Prapiroon105-112caused by the environmental f1ow field and typhoon structurecaused比[9] LI Ying, CHEN Lian-shou, ZHANG Sheng-jun, et al.variation [J]. Meteor. Mon., 2007, 3311): 9-15.Statistical characteristics of tropical cyclone making landfalls[17] HU Chun-mei, DUAN Yihong, YU Hui, et al. Theon China [J. J. Trop. Meteor, 2004, 20(1): 14-23.diagnostic analysis of the rapid change in tropical cyclones[10] CHEN Lian-shou. The evolution on research andintensity before landfall in South China []. J, Trop. Meteor,operational forecasting techniques of tropical cyclones [0. J.2005, 21(4): 377-382.Appl. Meteor, 2006, 17(6): 672-681.[18] KANAMITSU M, EBISUZAKI w, WOOLLEN J, et al.[11] LI Chun-bui, LIU Chun-xia, CHENG Zheng-quan. TheNCEP-DOE AMIP-II Reanalysis (R-2) [小. Bull. Amer. Meteor.characteristics of temporal and spatial distribution of tropicalSoc., 2002: 83: 1631-1643.cyclone frfrequencies over the South China Sea and is afecting[19] CAMARGO S J, SOBEL A H. Westerm North Pacificoceanic factors in the past 50yrs [0 J. Trop. Meteor, 2007,tropical cyclone intensity and ENSO [J]. J. Clim, 2005, 18(15):23(4): 341-347.[12] YANG Ya-xin. Occurence regularity of tropical cyclone[20] CHAN J C L. Tropical Cyclone activity in the NorthWestin South China Sea 小J. Shanghai Maritime Univ, 2005,Pacific in relation to the El Nino/Southem Oscillation26(4): 16-19.phenomenon [J]. Mon. Wea. Rev, 1985, 113(4): 599-606.[13] CHEN Guang-hua, QIU Guo-qing. A case simulation[21] HUANG Yong, LI Chong-yin, WANG Ying, et al.study on offshore intensification mechanism of tropical cycloneInterdecadal variability of tropical cyclone formation in thein South China Sea [J Acta Meteor. Sinica, 2005, 63(3):northwest Pacifie [J] J. PLA Univ. Sci. Technol. (Nat. Sci.Edit), 2008, 25 (1): 81-87. .14] LUO Qiu-hong, WU Nai-geng, HE Xia-jiang.[22] FENG Li-hua. Relationship between tropical cyclonesRelationship of OLR and development of tropical cyclone overlanding in China and sea surface temperature in the Pacific [J.South China Sea [0. Quart. J. Appl. Meteor, 2004, 15(1):Acta Geograph. Sinica, 2003, 58 (2): 209-214.Citation: LU Shan and WU Nai-geng. Contrast analysis of April typhoons Leo and Neoguri. J. Trop. Meter, 2011, 17(4): 409-417.中国煤化工MYHCNMHG

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