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Effects of Sea Spray Evaporation and Dissipative Heating on Intensity and Structure of tropical cyclone

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Advances in Atmospheric Sciences 2012年第4期29卷 810-822页

作者：程小平费建芳黄小刚郑静 Institute of Meteorology PLA University of Science and Technology 73061 Troop of PLA

To examine effects of sea spray evaporation and dissipative heating on structure and intensity of a real tropical cyclone, the sea spray flux parameterization scheme was incorporated into the fifth-generation Penn- sylvania State University National Center for Atmospheric Research Mesoscale Model （MM5）. Sensitivity tests were performed with varying the spray source function intensities and with and without dissipation heating. The numerical results indicate that sea spray evaporation increases the interfaeial sensible heat flux, which is increased by 16% for the moderate spray and 47% for the heavy spray, but has little effect on the interfaeial latent heat flux. The net effect of sea spray evaporation is to decrease the total sensible heat flux and to increase the total latent heat flux. The total enthalpy flux is increased by 1% and 12% with moderate and strong spray amounts, respectively. Consistent with these results, the intensity of the tropical cyclone is increased by 5% and 16% in maximum 10-m wind speed, respectively, due to sea spray evapora- tion. Sea spray evaporation and dissipative heating modify the tropical cyclone structure in important but complex ways. The effect of sea spray on the near-surface temperature and moisture depends on the spray amounts and its location within the tropical cyclone. Within the high-wind region of a tropical cyclone, the lower atmosphere becomes cooler and moister due to the evaporation of sea spray. However, the dissipative heating offsets the cooling due to sea spray evaporation, which makes the lower atmosphere warmer.

关键词： sea spray dissipative heat tropical cyclone

A primary study of the correlation between the net air-sea heat flux and the interannual variation of western North Pacific tropical cyclone track and intensity

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Acta Oceanologica Sinica 2011年第6期30卷 27-35页

作者： WU Liang WEN Zhiping HUANG Ronghui Center for Monsoon and Environment Research/Department of Atmospheric Sciences Sun Yat-sen University Guangzhou 510275 China Center for Monsoon System Research Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

A singular value decomposition （SVD） analysis is carried out to reveal the relationship between the interannual variation of track and intensity of the western North Pacific tropical cyclones （WNPTCs） in the tropical cyclone （TC） active season （July–November） and the global net air-sea heat flux （Q net ） in the preceding season （April–June）. For this purpose, a tropical cyclone track and intensity function （TIF） is defined by a combination of accumulated cyclone energy （ACE） index and a cyclone track density function. The SVD analysis reveals that the first mode is responsible for the positive correlation between the upward heat flux in the tropical central Pacific and the increased activity of western North Pacific （WNP） TIF, the second mode for the positive correlation between the upward heat flux in the North Indian Ocean and the northeastward track shift of WNPTCs and the third mode for the negative correlation between the upward heat flux in mid-latitude central Pacific and the northwest displacement of the WNP TC-active center. This suggests that Q net anomalies in some key regions have a substantial remote impact on the WNP TC activity.

关键词： tropical cyclone western North Pacific the net air-sea heat flux （Q net ） interannual variation

Boundary-Layer Wind Structure in a Landfalling tropical cyclone

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Advances in Atmospheric Sciences 2006年第5期23卷 737-749页

作者：唐晓东谈哲敏 Key Laboratory of Mesoscale Severe Weather/Ministry of Education Department of Atmospheric Sciences Nanjing University Nanjing 210093

In this study, a slab boundary layer model with a constant depth is used to analyze the boundary-layer wind structure in a landfalling tropical cyclone. Asymmetry is found in both the tangential and radial components of horizontal wind in the tropical cyclone boundary layer at landfall. For a steady tropical cyclone on a straight coastline at landfall, the magnitude of the radial component is greater in the offshoreflow side and the tangential component is greater over the sea, slightly offshore, therefore the greater total wind speed occurs in the offshore-flow side over the sea. The budget analysis suggests that：（1） a greater surface friction over land produces a greater inflow and the nonlinear effect advects the maximum inflow downstream, and （2） a smaller surface friction over the sea makes the decrease of the tangential wind component less than that over land. Moreover, the boundary layer wind structures in a tropical cyclone are related to the locations of the tropical cyclone relative to the coastline due to the different surface frictions. During tropical cyclone landfall, the impact of rough terrain on the cyclone increases, so the magnitude of the radial component of wind speed increases in the offshore-flow side and the tangential component outside the radius of maximum wind speed decreases gradually.

关键词： boundary-layer wind tropical cyclone landfall surface drag

An improved wind speed algorithm for “Jason-1” altimeter under tropical cyclone conditions

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Acta Oceanologica Sinica 2014年第7期33卷 83-88页

作者： QIN Bangyong ZHOU Xuan ZHANG Honglei YANG Xiaofeng LU R ong YU Yang SHI Lijiana State Key Laboratory of Remote Sensing Science Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences Beijing 100101 China P. O. Box 5111 Beijing 100094China National Satellite Ocean Application Service State Oceanic Administration Beijing 100081 China

Rain effect and lack of in situ validation data are two main causes of tropical cyclone wind retrieval errors. The National Oceanic and Atmospheric Administration＇s Climate Prediction Center Morphing technique （CMORPH） rain rate is introduced to a match-up dataset and then put into a rain correction model to remove rain effects on ＂Jason-1＂ normalized radar cross section （NRCS）; Hurricane Research Division （HRD） wind sPeed, which integrates all available surface weather observations, is used to substitute in situ data for establishing this relationship with ＂Jason-l＂ NRCS. Then, an improved ＂Jason-l＂ wind retrieval algorithm under tropical cyclone conditions is proposed. Seven tropical cyclones from 2003 to 2010 are studied to validate the new algorithm. The experimental results indicate that the standard deviation of this algorithm at C-band and Ku-band is 1.99 and 2.75 m/s respectively, which is better than the existing algorithms. In addition, the C-band algorithm is more suitable for sea surface wind retrieval than Ku-band under tropical cyclone conditions.

关键词： altimeter wind speed, rain effect tropical cyclone

A New Method for Calculating the Wind Speed Distribution of a Moving tropical cyclone

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Advances in Atmospheric Sciences 2010年第1期27卷 69-79页

作者：胡邦辉杨修群谭言科王咏青范勇 Institute of Severe Weather and Climate Nanjing University Institute of Meteorology PLA University of Science and Technology Nanjing University of Information Science and Technology

Based on gradient wind equations, including frictional force, and considering the effect of the movement of a tropical cyclone on wind speed, the Fujita Formula is improved and further simplified, and the numerical scheme for calculating the maximum wind speed radius and wind velocity distribution of a moving tropical cyclone is derived. In addition, the effect of frictional force on the internal structure of the tropical cyclone is discussed. By comparison with observational data, this numerical scheme demonstrates great advantages, i.e. it can not only describe the asymmetrical wind speed distribution of a tropical cyclone reasonably, but can also calculate the maximum wind speed in each direction within the typhoon domain much more accurately. Furthermore, the combination of calculated and analyzed wind speed distributions by the scheme is perfectly consistent with observations.

关键词： tropical cyclone maximum wind speed radius wind velocity distribution

Effects of tropical cyclone Activity on the Boundary Moisture Budget over the Eastern China Monsoon Region

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Advances in Atmospheric Sciences 2017年第6期34卷 700-712页

作者： Xiaobin LIN Zhiping WEN Wen ZHOU Renguang WU Ruidan CHEN Center for Monsoon and Environment Research and Department of Atmospheric Sciences Sun Yat-Sen University Guy Carpenter Asia-Pacific Climate Impact Centre School of Energy and EnvironmentCity University of Hong Kong Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of Sciences

In summer, water vapor over the eastern China monsoon region （ECMR） comes mainly from low latitudes and is modu- lated by tropical cyclone （TC） activity in East Asia （EA）. This study examines the variability of water vapor transport over the ECMR, especially of the moisture inflow via the southern and eastern boundaries. The results of composite and correlation analyses, using data from 1979 to 2010, reveal significant differences in moisture budgets along the boundaries between TC days and non-TC days. Almost 80% of the water vapor transport via the eastern boundary occurs during TC days, while at the southern boundary most inflow occurs on non-TC days. The ratio of the total water vapor transport between TC and non-TC days is about 4：6. In addition, the E1 Nifio-Southem Oscillation （ENSO） exhibits a remarkable influence on moisture trans- port over EA and the contributions of moisture inflow on TC days increase （reduce） in E1 Nifio （La Nifia） years. Moreover, different types of TCs, based on their tracks, have different effects on the moisture budgets along the southern and eastern boundaries. When TCs enter EA （but not the ECMR）, they favor the moisture inflow via the eastern boundary and hinder the moisture inflow via the southern boundary. After TCs enter the ECMR, the inhibition of moisture inflow via the southern boundary will be weakened, and more water vapor can be brought into the ECMR. For some recurring TCs with an increase in TC activity in the midlatitudes, the influence is uncertain in different cases. The results herein suggest that TC activity is an important factor that influences the boundary moisture budgets in the ECMR.

关键词： tropical cyclone boundary moisture budget eastern China monsoon region

Climatological and Seasonal Variations of the tropical cyclone Genesis Potential Index Based on Oceanic Parameters in the Global Ocean

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Journal of Ocean University of China 2021年第6期20卷 1307-1315页

作者： PAN Lixia WANG Xin ZHOU Lei WANG Chunzai State Key Laboratory of tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Innovation Academy of South China Sea Ecology and Environmental Engineering Chinese Academy of SciencesGuangzhou 510301China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China University of Chinese Academy of Sciences Beijing 100049China School of Oceanography Shanghai Jiao Tong UniversityShanghai 200030China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China

This study investigates the global performance of the tropical cyclone(TC)genesis potential index based on oceanic parameters(GPI_(ocean))proposed by Zhang et al.(2016).In six major TC formation basins,GPI_(ocean)can represent the seasonal variations of TC genesis over most basins,except for the North Indian Ocean(NIO).The monthly climatological GPI_(ocean)shows only a single peak in the NIO,which cannot describe the bimodal pattern of the annual cycle of TC genesis.To determine the cause of the poor performance of GPI_(ocean)in the NIO,the relative contributions of different parameters related to GPI_(ocean)are calculated and compared with those related to the genesis potential index developed by Emanuel and Nolan(2004)(GPI04).Results show that the net longwave radiation on the sea surface is responsible for the single peak of TC genesis in the NIO in boreal summer.Compared with GPI04,vertical wind shear is not involved in GPI_(ocean).Vertical wind shear is the dominant factor inhibiting TC genesis in the NIO in boreal summer.Therefore,the absence of vertical wind shear in GPI_(ocean)results in the failure of the annual cycle of TC genesis in the NIO.

关键词： North Indian Ocean tropical cyclone genesis potential index

Convective Asymmetries Associated with tropical cyclone Landfall: β-Plane Simulations

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Advances in Atmospheric Sciences 2010年第4期27卷 795-806页

作者：黄伟梁旭东 Shanghai Typhoon Institute China Meteorological Administration

The physical processes associated with changes in the convective structure of an idealized tropical cyclone （TC） during landfall on a beta-plane were studied using the fifth-generation Pennsylvania State University- National Center for Atmospheric Research Mesoscale Model, version 3 （MM5）. The simulation results suggested that the suppression of moisture supply and increased friction acted to enhance the convection from the left and front quadrants of the TC to the front and right of the TC during different periods of landfall. When surface moisture flux was turned off, convection in other parts of the quadrant was clearly suppressed and the total rainfall was reduced. When surface friction was increased, precipitation showed a marked increase after the TC made landfall. Wetter air at low and intermediate levels, and drier air at high levels around the onshore side of the coastline led to a high value of convective available potential energy （CAPE）. Consequently, convection was enhanced immediately downstream of this area when the surface moisture flux was cut off. When surface friction was increased, the physical process was similar prior to landfall. After landfall, increased convergence at the onshore side of the land resulted in enhanced convection in front of the TC. Consistent with previous findings, our results suggest that during landfall the TC structure changes from one of thermodynamic symmetry to asymmetry due to differential moisture flux between the land and sea surface. The asymmetry of the thermodynamic structure, which can be explained by the distribution of CAPE, causes an asymmetric rainfall structure.

关键词： tropical cyclone landfall convective asymmetry

Simulated Sensitivity of the tropical cyclone Eyewall Replacement Cycle to the Ambient Temperature Profile

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Advances in Atmospheric Sciences 2017年第9期34卷 1047-1056页

作者： Xulin MA Jie HE Xuyang GE Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory of Meteorological DisasterNanjing University of Information Science and Technology

In this study, the impacts of the environmental temperature profile on the tropical cyclone eyewall replacement cycle are examined using idealized numerical simulations. It is found that the environmental thermal condition can greatly affect the formation and structure of a secondary eyewall and the intensity change during the eyewall replacement cycle. Simulation with a warmer thermal profile produces a larger moat and a prolonged eyewall replacement cycle. It is revealed that the enhanced static stability greatly suppresses convection, and thus causes slow secondary eyewall formation. The possible processes influencing the decay of inner eyewall convection are investigated. It is revealed that the demise of the inner eyewall is related to a choking effect associated with outer eyewall convection, the radial distribution of moist entropy fluxes within the moat region, the enhanced static stability in the inner-core region, and the interaction between the inner and outer eyewalls due to the barotropic instability. This study motivates further research into how environmental conditions influence tropical cyclone dynamics and thermodynamics.

关键词： tropical cyclone eyewall replacement cycle ambient temperature profile