Study and Analysis of Meteorological Effect on Shanghai Sheshan National Tourist Resorts in Shanghai

In this paper, the main meteorological disasters in the Sheshan National Tourist and Vacation Areas are analyzed by using the climate data from 1955 to 2014, such as average temperature, relative humidity, wind speed, insolation duration. The influences of meteorological parameters on this area are studied with the climate comfort evaluation and meteorological disaster climate trend. It is found that the major meteorological disasters in this area including fog, typhoon, storm, wind, thunderstorms and high temperature, were occurred in different periods with higher frequency from May to October. Nineteen comfortable ten-day periods in a year are suitable for tourist activities, during March and May, late September and the end of December. And seventeen ten-day periods in a year are not suitable for tourist activities, from January to February and from June to the middle of September. Some suggestions for tourism weather service on the basis of these results are listed in the conclusion.

The Effect of Three-Dimensional Variational Data Assimilation of QuikSCAT Data on the Numerical Simulation of Typhoon Track and Intensity

In this paper, the three-dimensional variational data assimilation scheme (3DVAR) in the mesoscale model version 5 (MM5) of the US Pennsylvania State University/National Center for Atmospheric Research is used to study the effect of assimilating the sea-wind data from QuikSCAT on the prediction of typhoon track and intensity. The case of Typhoon Dujuan (2003) is first tested and the results show appreciable improvements. Twelve other cases in 2003 are then evaluated. The assimilation of the QuikSCAT data produces significant impacts on the structure of Dujuan in terms of the horizontal and vertical winds, sea-level pressure and temperature at the initial time. With the assimilation, the 24-h (48-h) track prediction of 11 (10) out of the 12 typhoons is improved. The 24-h (48-h) prediction of typhoon intensity is also improved in 10 (9) of the 12 cases. These experiments therefore demonstrate that assimilation of the QuikSCAT sea-wind data can increase the accuracy of typhoon track and intensity predictions through modification of the initial fields associated with the typhoon.

A statistical analysis of typhoon frequency and application in design wave height

A typhoon leading is an important natural disaster to many disasters to China. A giant wave caused by it has brought large threat for an offshore project. Based on the maximum entropy principle,one new model which has 4 undetermined parameters is constructed,which is called the discrete maximum entropy probabilistic model. In practical applications,the design wave height is considered as soon as possible in a typhoon affected sea areas,the result fits the observed data well. Further more this model does not have the priority compared with other distributions as Poisson distribution. The model provides a theoretical basis for the engineering design more reasonable when considering typhoon factors comprehensively.

An Observational Study of Typhoon Imbudo in 2003

Typhoon Imbudo was a super-typhoon over the northwestern Pacific in 2003. It caused tremendous damage when it made landfalls in the Philippines and China. This paper documents observational analyses of Typhoon Imbudo during its landfall in China. All available observations are used to study its motion, intensity changes, convection, structure and precipitation. Best-track data indicate that Imbudo moved west-northwestward until 1800 UTC 23 July and then turned northwestward. FNL (final) analysis data show that the motion of Imbudo is dominated by changes of the subtropical high. At Imbudo's mature stage, the minimum sea level pressure dropped to 910 hPa and the maximum sustained winds were as high as 67 m s 1, which is the intensity of a super-typhoon. The surface wind field exhibited asymmetric characteristics. Polar-orbiting satellite imagery also manifested convective asymmetry before Imbudo made landfall in China. Analyzed the vertical wind shear, it is shown that the convection has a downshear-left pattern. All kinds of precipitation data were used to identify the asymmetric characteristic of the rainfall associated with the Imbudo. The maximum rainfalls were located in the southern boundary area between Guangxi and Guangdong. However, the lack of in situ observations limited further analyses of this typhoon.

The Structure and Rainfall Features of Tropical Cyclone Rammasun (2002)

Tropical Rainfall Measuring Mission (TRMM) data [TRMM Microwave Imager/Precipitation Radar/Visible and Infrared Scanner (TMI/PR/VIRS)] and a numerical model are used to investigate the structure and rainfall features of Tropical Cyclone (TC) Rammasun (2002). Based on the analysis of TRMM data, which are diagnosed together with NCEP/AVN [Aviation (global model)] analysis data, some typical features of TC structure and rainfall are preliminary discovered. Since the limitations of TRMM data are considered for their time resolution and coverage, the world observed by TRMM at sev- eral moments cannot be taken as the representation of the whole period of the TC lifecycle, therefore the picture should be reproduced by a numerical model of high quality. To better understand the structure and rainfall features of TC Rammasun, a numerical simulation is carried out with mesoscale model MM5 in which the validations have been made with the data of TRMM and NCEP/AVN analysis.

The Role of β-effect and a Uniform Current on Tropical Cyclone Intensity

A limited-area primitive equation model is used to study the role of the β-effect and a uniform current on tropical cyclone (TC) intensity. It is found that TC intensity is reduced in a non-quiescent environment compared with the case of no uniform current. On an f-plane, the rate of intensification of a tropical cyclone is larger than that of the uniform flow. A TC on a β-plane intensifies slower than one on an f-plane. The main physical characteristic that distinguishes the experiments is the asymmetric thermodynamic (including convective) and dynamic structures present when either a uniform flow or β-effect is introduced. But a fairly symmetric TC structure is simulated on an f-plane. The magnitude of the warm core and the associated subsidence are found to be responsible for such simulated intensity changes. On an f-plane, the convection tends to be symmetric, which results in strong upper-level convergence near the center and hence strong forced subsidence and a very warm core. On the other hand, horizontal advection of temperature cancels part of the adiabatic heating and results in less warming of the core, and hence the TC is not as intense. This advective process is due to the tilt of the vortex as a result of the β-effect. A similar situation occurs in the presence of a uniform flow. Thus, the asymmetric horizontal advection of temperature plays an important role in the temperature distribution. Dynamically, the asymmetric angular momentum (AM) flux is very small on an f-plane throughout the troposphere. However, the total AM exports at the upper levels for a TC either on a β-plane or with a uniform flow environment are larger because of an increase of the asymmetric as well as symmetric AM export on the plane at radii >450 km, and hence there is a lesser intensification.

Impacts of TRMM SRR assimilation on the numerical prediction of tropical cyclone

Impacts of the four-dimensional variation （4DVAR） assimilation of Tropical Rainfall Measuring Mission （TRMM）/TMI surface rainfall rate （SRR） on the initialization and simulation of TC Danas in 2001 are studied. A number of sensitivity experiments are designed to evaluate the performance of assimilation during the particular stage when Danas developed from a tropical depression towards a typhoon, as well as an abrupt turning. Under the dynamic and thermodynamic constraints of meso-scale model and the 4DVAR, the TRMM SRR data are directly assimilated in high horizontal resolution （ 18 kin）. On the basis of the adjustment of initial model field, 4DVAR of TRMM SRR considerably improved the depiction of TC＇ s structure and rainfall. The same explanation can also be given to the enhancement of simulation on TC＇ s intensity and track. In comparison with the popular idea of twice steps of SRR assimilation, namely, 4DVAR pins 1DVAR, the retrieval error is expected to be avoided in the procedure of direct 4DVAR. In addition, the TRMM SRR 4DVAR within a high-resolution model can take into account as much information as observed and is expected to be performed in operational use if the observed rainfall data are routinely available.

Moisture Analysis of a Squall Line Case Based on Precipitable Water Vapor Data from a Ground-Based GPS Network in the Yangtze River Delta

A squall line swept eastward across the area of the Yangtze River Delta and produced gusty winds and heavy rain from the afternoon to the evening of 24 August 2002. In this papers the roles of moisture in the genesis and development of the squall line were studied. Based on the precipitable water vapor （PWV） data from a ground-based GPS network over the Yangtze River Delta in China, plus data from a Pennsylvania State University/National Atmospheric Center （PSU/NCAR） mesoscale model （MM5） simulation, initialized by three-dimensional variational （3D-VAR） assimilation of the PWV data, some interesting features are revealed. During the 12 hours prior to the squall line arriving in the Shanghai area, a significant increase in PWV indicates a favorable moist environment for a squall line to develop. The vertical profile of the moisture illustrates that it mainly increased in the middle levels of the troposphere, and not at the surface. Temporal variation in PWV is a better precursor for squall line development than other surface meteorological parameters. The characteristics of the horizontal distribution of PWV not only indicated a favorable moist environment, but also evolved a cyclonic wind field for a squall line genesis and development. The ＂＋2 mm＂ contours of the three-hourly PWV variation can be used successfully to predict the location of the squall line two hours later.

THE IMPACT OF INITIAL FORCED WIND ON THE PREDICTABILITY OF THE ZEBIAK-CANE COUPLED OCEAN-ATMOSPHERE MODEL

With simultaneous observed sea surface temperature anomaly (SSTA), the difference betweenNCEP/NCAR 925hPa reanalysis wind stress anomaly (NCEPWSA) and FSU wind stress anomaly (FSUWSA) isanalyzed, and the prediction abilities of Zebiak-Cane coupled ocean-atmosphere model (ZC coupled model) withNCEPWSA and FSUWSA serving respectively as initialization wind are compared. The results are as follows.The distribution feature of NCEPWSA matches better with that of the observed SSTA than counterpart ofFSUWSA both in 1980s and in 1990s; The ZC ocean model has a better skill under the forcing of NCEPWSAthan that of FSUWSA, especially in 1990s. Meanwhile, the forecast abilities of the ZC coupled model in 1990sas well as in 1980s have been improved employing NCEPWSA as initialization wind instead of FSUWSA.Particularly, it succeeded in predicting 1997/1998 El Nio 6 to 8 months ahead; further analysis shows that onthe antecedent and onset stages of the 1997/1998 El Nio event, the horizontal cold and warm distributioncharacteristics of the simulated SSTA from ZC ocean model, with NCEPWSA forcing compared to FSUWSAforcing, match better with counterparts of the corresponding observed SSTA, whereby providing betterpredication initialization conditions for ZC coupled model, which, in turn, is favorable to improve the forecastability of the coupled model.

An Overview of Tropical Cyclone and Tropical Meteorology Research Progress

There has been much progress in the study of tropical cyclones and tropical meteorology in China in the past few years. A new atmospheric field experiment of tropical cyclone landfall with the acronym of CLATEX (China Landfalling Typhoon Experiment) was implemented in July-August 2002. The boundary layer characteristics of the target typhoon Vongfong and the mesoscale structural features of other land-falling typhoons were studied. In addition, typhoon track operational forecasting errors in the last decade have been reduced because the operational monitoring equipment and forecast techniques were improved. Some results from the research program on tropical cvclone landfall, structure and intensity change, inten-sification near coastal waters, interaction between tropical cyclone and mid-latitude circulation, and the interaction among different scales of motion are described in this paper. Four major meteorological scien-tific experiments in China with international cooperation were implemented in 1998: the South China Sea monsoon field experiment (SCSMEX), the Tibetan Plateau field experiment (TIPEX), the Huaihe River basin energy and water cycle experiment (HUBEX), and the South China heavy rain scientific experiment (HUAMEX). Although these field experiments have different scientific objectives, they commonly relate to monsoon activities and they interact with each other. The valuable intensive observation data that were obtained have already been shared internationally. Some new findings have been published recently. Other research work in China, such as the tropical air-sea interaction, tropical atmospheric circulation, and weather systems, are reviewed in this paper as well. Some research results have shown that the rainfall anomalies for different regions in China were closely related to the stages of El Nino events.

On the Multiple Equilibrium of the Development of Tropical Cyclone in Nonlinear CISK Model

By using non-static atmosphere equations including basic current, heating force and friction, we discuss the balance amplitude of vertical motion in the conditions of constant heating force, linear and non-linear interaction between large-scale ascending motion and diabatic heating force. In the non-linear condition, the multiple equilibrium feature of the tropical cyclone development is discussed and the reason of the sudden varying of tropical cyclone intensity is studied preliminarily.

Geometric Characteristics of Tropical Cyclone Eyes before Landfall in South China Based on Ground-Based Radar Observations

The geometric characteristics of tropical cyclone（TC） eyes before landfall in South China are examined using groundbased radar reflectivity. It is found that the median and mean eye area decrease with TC intensity, except for the severe typhoon category, and the eye size increases with height. The increasing rate of eye size is relatively greater in upper layers.Moreover, the ratio of eye size change in the vertical direction does not correlate with TC intensity. No relationship is presented between the ratio of eye size change in the vertical direction and the vertical wind shear. No relationship between the vertical change in eye size and the eye size at a certain level is found, inconsistent with other studies. No relationship exists between the vertical change in eye size and the intensity tendency. The eye roundness values range mainly from 0.5 to 0.7, and more intense TCs generally have eyes that are more circular.

纬向平均环流预报的系统性误差及其改进

大量的月预报实例分析表明,纬向平均环流(本文指高度场纬向平均分量)存在明显的系统性预报误差,且在总误差中占有可观的份额。国内外其它模式也存在类似的现象。为克服这一困难,本文尝试了“结合”(hybrid)的途径。应用重构相空间理论和非线性时空序列预测方法,在大量历史资料的基础上,构造了月尺度逐侯纬向平均高度场(零波分量)距平场的非线性预报模型。然后,将非线性预报和谱模式动力预报结合起来,即将非线性预报结果转化为模式需要的预报量,再在模式积分过程中的每一步取代其相应部分,实施过程订正。初步试验结果表明,这种途径有效地减少了模式纬向环流的预报误差;特别是通过非线性波流相互作用,还改善了部分波动分量的预报。

Predicting PM_(2.5) Concentration in the Yangtze River Delta Region Using Climate System Monitoring Indices and Machine Learning

Changing meteorological conditions during autumn and winter have considerable impact on air quality in the Yangtze River Delta(YRD)region.External climatic factors,such as sea surface temperature and sea ice,together with the atmospheric circulation,directly affect meteorological conditions in the YRD region,thereby modulating the variation in atmospheric PM_(2.5) concentration.This study used the evolutionary modeling machine learning technique to investigate the lag relationship between 144 climate system monitoring indices and autumn/winter PM_(2.5) concentration over 0-12 months in the YRD region.After calculating the contribution ratios and lagged correlation coefficients of all indices over the previous 12 months,the top 36 indices were selected for model training.Then,the nine indices that contributed most to the PM_(2.5) concentration in the YRD region,including the decadal oscillation index of the Atlantic Ocean and the consistent warm ocean temperature index of the entire tropical Indian Ocean,were selected for physical mechanism analysis.An evolutionary model was developed to forecast the average PM_(2.5) concentration in major cities of the YRD in autumn and winter,with a correlation coefficient of 0.91.In model testing,the correlation coefficient between the predicted and observed PM_(2.5) concentrations was in the range of 0.73-0.83 and the root-mean-square error was in the range of 9.5-11.6μg m-3,indicating high predictive accuracy.The model performed exceptionally well in capturing abnormal changes in PM_(2.5) concentration in the YRD region up to 50 days in advance.

OVERVIEW OF SEVERE TYPHOON FITOW AND ITS OPERATIONAL FORECASTS

Severe typhoon Fitow(1323)brought persistent and heavy rainfall to Zhejiang and the Shanghai area after it made landfall at Fujian Province of China in October 2013,breaking the rainfall records of several counties and districts in Zhejiang.In this paper,we provide an overview of the characteristics of Fitow’s landfall,including its track,intensity,structural evolution,heavy rainfall,and wind.We also describe some of the associated disastrous impacts.Finally,we provide verifications of operational forecasts of its track,intensity and rainfall.Though the track and intensity is well predicted,the rainfall persistence and enhancement in the second stage in Shanghai and north Zhejiang areas are not predicted out at all.The analysis presented in this paper provides forecasters and researchers with some valuable information on Fitow,which could form a useful basis for further studies.

THE EFFECT OF THE LONG WAVE OVER THE NORTHERN HEMISPHERE ON TYPHOON TRACKS OVER THE NORTHWESTERN PACIFIC

The normal typhoon paths with 109 cases during the period from 1960 to 1979 have been analysed in this study. These paths are divided into 7 categories. The effect of the position and intensity of large- scale wave on each category has been examined. It has been discovered, as a result, that this effect is rather evident. On the other hand, the teleconnection between different centers of anion does exist. A simple theoretical analysis indicates that the teleconnection is related to the propagation of wave energy. Thus, to predict correctly typhoon path, not only the steering flow of typhoon, but also, more significantly, the behavior of large-scale wave over the Northern Hemisphere must be taken into consideration.

RAPID INTENSIFICATION NEAR LANDFALL OF TYPHOON VICENTE(2012)

Typhoon Vicente(2012) underwent rapid intensification(RI) within 24 h before landfall in China's Mainland. Analysis of the large-scale environment and characteristics of Vicente identifies the aforementioned intensification as classic RI. The process occurred in an environmental flow with a deep-layer shear ranging from 5 ms-1 to 8 ms-1. Convection caused by persistent vertical shear forcing of the vortex was observed primarily in the downshear left quadrant of the storm. However, radar and satellite observations indicate that the northern convection of the inner core of Vicente quickly developed in the down-shear right three hours near landfall.

Classification of ozone pollution and analysis of meteorological factors in the Yangtze River Delta

Serious regional ozone(O_(3))pollution often plagues the Yangtze River Delta(YRD).The formation mechanism of these regional pollution events,including the meteorological and emission factors leading to these pollution events and how to affect the distribution of O_(3),still needs further research and exploration.In this study,we first define the standard of O_(3)regional pollution in the YRD,and then select 248 regional pollution cases from 2015 to 2020 according to the defined standard.For the pollution cases in pollution months(May and June),PCT(principal component analysis in T-mode)classification method is used to classify the ozone concentration distribution in YRD area.The regional distribution of the O_(3)concentrations in the YRD is divided into five types,and the overall type(Type 1)accounts for 15%,which is related to the control of YRD area by high-pressure center.Under the control of high pressure,the weather is sunny with the high temperature,and this weather condition is favorable for ozone generation and intercity transmission,causing extensive pollution.The double center type(Type 2)accounts for 8%.This type of YRD is controlled by the front of the high pressure(the high-pressure center is located in North China),and the weather in the middle and north is conducive to the generation and transmission of O_(3).Inland type(Type 3)accounts for 24%.The main body of this type of high pressure is located in Mongolia.The easterly wind in YRD area is conducive to the inland transmission of O_(3)precursors.The northern coastal type(Type 4)accounts for 44%.This type of YRD area is mainly controlled by the weak pressure field.The weather in the northern coastal area is sunny and the solar radiation for a long time is conducive to the formation of O_(3).The southern coastal type(Type 5)accounts for 10%,the solar radiation is strong in the southern region mainly under the influence of the post-offshore high pressure.This study provides new insights into the relationship between O_(3)pollution distribution types and atmospheric circulation in YRD area,and reveals the difference of potential meteorological impacts of different O_(3)pollution distribution types.

Synergetic roadmap of carbon neutrality and clean air for China

It is well recognized that carbon dioxide and air pollutants share similar emission sources so that synergetic policies on climate change mitigation and air pollution control can lead to remarkable co-benefits on greenhouse gas reduction,air quality improvement,and improved health.In the context of carbon peak,carbon neutrality,and clean air policies,this perspective tracks and analyzes the process of the synergetic governance of air pollution and climate change in China by developing and monitoring 18 indicators.The 18 indicators cover the following five aspects:air pollution and associated weather-climate conditions,progress in structural transition,sources,inks,and mitigation pathway of atmospheric composition,health impacts and benefits of coordinated control,and synergetic governance system and practices.By tracking the progress in each indicator,this perspective presents the major accomplishment of coordinated control,identifies the emerging challenges toward the synergetic governance,and provides policy recommendations for designing a synergetic roadmap of Carbon Neutrality and Clean Air for China.

NUMERICAL STUDY ON THE EFFECTS OF SEA SURFACE TEMPERATURE ON TROPICAL CYCLONE INTENSITY-PART I:NUMERICAL EXPERIMENT OF THE TROPICAL CYCLONE INTENSITY RELATED TO SST

In the context of a model of tropical cyclone intensity based on an improved meso-scale atmospheric model, numerical simulation is performed of the track and intensity variation of tropical cyclones (TC) arising from sea surface temperature (SST) variation over a specified sea region. Evidence suggests that the model is capable of modeling quite welt the track and intensity of TC: SST variation leads to an abrupt change in the cyclone intensity: the response of the cyclone to the abrupt SST change lasts 8—12 h.