Effects of Tropical Storm on Mangroves Forest Structure of Dongzhai Harbor in Hainan Island

The effects of tropical storm on the community structure of Sonneratia caseolaris-Sonneratia apetala(S.caseolaris-S.apetala) artificial mangroves and Ceriops tagal-Rhizophora stylosa(C.tagal-R.stylosa) natural mangroves were analyzed in Dongzhai Harbor in Hainan Island,and the results showed that the average tree height,crown width(CW) in east-west direction(E-W) and north-south direction(N-S) of S.caseolaris-S.apetala artificial mangroves were decreased by 2.8%,14.3% and 12.1% respectively,but the average clear bole height was increased by 60.0% after tropical storm.For C.tagal-R.stylosa natural mangroves,the average tree height and clear bole height were increased by 8.3% and 20.0%,but there was no change in CW(E-W) and CW(N-S).Therefore,tropical storm had greater effects on artificial mangroves than natural mangroves.After tropical storm,tree heights of different species increased in the following sequence:C.tagal>R.stylosa>S.apetala>S.caseolaris,and the sequence of effect degree on CW was C.tagal>R.stylosa>S.caseolaris>S.apetala,while it was C.tagal < R.stylosa < S.caseolaris < S.apetala for clear bole height.Under the effect of tropical storm,the average biomass loss and dry biomass loss of S.caseolaris-S.apetala artificial mangroves were 0.22 and 0.13 t/hm2 respectively,while there was a minimal biomass loss in C.tagal-R.stylosa natural mangroves.On the whole,the wind resistance of natural mangroves was better than artificial mangroves,and that of C.tagal was stronger than R.stylosa,while S.caseolaris was better than S.apetala.

Effects of Vertical Wind Shear on Intensity and Rainfall Asymmetries of Strong Tropical Storm Bilis (2006)

The effects of environmental vertical wind shear （VWS） on the intensity and rainfall asymmetries in Tropical Storm （TS） Bilis （2006） have been analyzed based on TRMM/TMI-estimated surface rainfall data, QuikSCAT wind fields, 850- and 200-hPa winds of the NCEP-NCAR reanalysis, precipitation data at 5-min intervals from automatic weather stations over China's Mainland, and the best track data of TS Bilis （2006）. The results show that the simultaneous and 6-hour-lagged correlation coefficients between VWS and storm intensity （the minimum central sea level pressure） are 0.59145 and 0.57438 （P 〈0.01）, respectively. The averaged VWS was found to be about 11 m s-1 and thus suppressed the intensification of Bilis （2006）. Distribution of precipitation in Bilis （2006） was highly asymmetric. The azimuthally-averaged rainfall rate in the partial eyewall, however, was smaller than that in a major outer rainband. As the storm intensified, the major rainband showed an unusual outward propagation. The VWS had a great impact on the asymmetric distribution of precipitation. Consistent with previous modeling studies, heavy rainfall generally occurred downshear to downshear-left of the VWS vector both near and outside the eyewall, showing a strong wavenumber-one asymmetry, which was amplified as the VWS increased.

EFFECTS OF LOW-LATITUDE MONSOON SURGE ON THE INCREASE IN DOWNPOUR FROM TROPICAL STORM BILIS

By using the dataset of CMA-STI Tropical Cyclone Optimal Tracks, NCEP/NCAR reanalysis and intensive surface observations, a study is performed of the influences of a low-latitude monsoon surge on the longer persistence and increase in torrential rains from the landing tropical storm Bilis. Results suggest that the southwest monsoon was anomalously active after Bilis came ashore. The westerly winds in Bilis's south side might give rise to the poleward movement of the SW monsoon, thus enlarging the pressure gradient between Bilis and the anticyclonic circulation to the south with the result of greatly intensified SW monsoon, which fueled plentiful water vapor, heat and momentum into the declining Bilis and allowed its long stay over land instead of erosion and disappearance. Before Bilis's landfall, the 2006 East Asian monsoon surge, characterized by the atmospheric ISO, experienced remarkable northward propagation. After landfall, the strong surge and powerful low frequency vapor convergence were just on the south side of Bilis, resulting in sharply increased rainfall. In addition, a broad belt of high-valued vapor fluxes extended from the eastern Arabian Sea via the Bay of Bengal, Indochina Peninsula and the South China Sea into the south of China. The belt was linked with the SW monsoon surge forming a moist tongue stretching from the Bay of Bengal to the south of China, which supplied continuously abundant vapor for Bilis along with the surge propagating poleward.

NUMERICAL SIMULATION OF THE RELATIONSHIP BETWEEN THE MAINTENANCE AND INCREASE IN HEAVY RAINFALL OF THE LANDING TROPICAL STORM BILIS AND MOISTURE TRANSPORT FROM LOWER LATITUDES

The NCEP/NCAR reanalysis, Japan Meteorological Agency(JMA) tropical cyclone tracks and intensive surface observations are used to diagnose the features of moisture transport of tropical storm Bilis(No. 0604), which is simulated by the WRF(weather research and forecasting) mesoscale numerical model. It is shown that the Bilis was linked with the moisture channel in the lower latitudes after its landing. Meanwhile, the cross-equatorial flows over 80°-100°E and Somali were active and brought abundant water vapor into the tropical storm, facilitating the maintenance of the landing storm with intensified heavy rainfall along its path. The simulation suggested that the decreased water vapor from lower latitudes prevents the maintenance of Bilis and the development of rainfall. While the cross-equatorial flows over 80°-100°E and Somali were in favor of keeping the cyclonic circulation over land. If the moisture supply fro m the Somali jet stream was reduced, the strength and area of heavy rainfall in tropical cyclone would be remarkably weakened. Consequently, the decreased water vapor from lower latitudes can remarkably suppress the deep convection in tropical storm, then Bilis was damped without the persistent energy support and the rainfall was diminished accordingly.

OBJECTIVE CLASSIFICATION OF THE TRACKS OF TROPICAL STORMS IN THE BAY OF BENGAL

An objective analysis of tropical cyclone tracks is performed, with which the tracks of 131 tropical storms(TSs) in 1972-2011 are separated into three types that move west-, north- and northwestward, denoted as Types A, B and C, respectively. Type A(21 TSs and 16% of total) has the origin in the southwestern Bay of Bengal, with the TS in a unimodal distribution as its seasonal feature, occurring mainly in autumn; 18 of the 21 TSs(taking up 90%) land mostly on the western Bay coast(west of 85°E); 5% of Type-A TSs attains the wind speed of >42.7 to 48.9 m/s. Type A has little or no effect on Tibet. Type B(74 TSs, 56.6% of the total) has its preferable origin in the central Bay of Bengal, with the TS in a bimodal distribution as its seasonal pattern. This type denotes the travel in the north in spring,with the landfall of 67 of the 74 TSs(accounting for 91%) mainly on the middle coast of the Bay(85° to 95°E), and19% of the TSs reaching the wind velocity of >42.7 to 48.9 m/s, which exert great effect on Tibet and it is this TS track that gives strong precipitation on its way through this region. Type C(36 TSs, 27.5% of the total) has its main origin in the southern part of the bay, and these TSs are formed largely in autumn, moving in the northwest direction,and 23 of the 36 TSs(64%) land mostly on the western Bay coast, lasting for a longer time, with almost no impact upon Tibet.

SAMPLE OPTIMIZATION OF ENSEMBLE FORECAST TO SIMULATE TROPICAL STORMS(MERBOK, MAWAR, AND GUCHOL) USING THE OBSERVED TRACK

Nowadays,ensemble forecasting is popular in numerical weather prediction(NWP).However,an ensemble may not produce a perfect Gaussian probability distribution due to limited members and the fact that some members significantly deviate from the true atmospheric state.Therefore,event samples with small probabilities may downgrade the accuracy of an ensemble forecast.In this study,the evolution of tropical storms(weak typhoon)was investigated and an observed tropical storm track was used to limit the probability distribution of samples.The ensemble forecast method used pure observation data instead of assimilated data.In addition,the prediction results for three tropical storm systems,Merbok,Mawar,and Guchol,showed that track and intensity errors could be reduced through sample optimization.In the research,the vertical structures of these tropical storms were compared,and the existence of different thermal structures was discovered.One possible reason for structural differences is sample optimization,and it may affect storm intensity and track.

Analysis on the Abnormal and Special Pathway of Number 0907 Tropical Storm "Swan"

By the comprehensive analysis on the circulation background,the pathway of tropical storm 'swan' was analyzed.The results showed that 'swan' moved toward the southwest direction.The main reasons were the spin-spin interaction of binary typhoons and the weak environmental wind field in 500 hPa.Moreover,the guidance airflow wasn't obvious,and the northeast guidance airflow in the south of continental high which was in the north of 'swan' strengthened.The asymmetric structure of wind speed near 'swan' center also favored the taxis of shift pathway.In addition,the variations of u component in south-north side and v component in east-west side of 500 hPa tropical storm center had the good prediction on the shift of 'swan'.

Variations in Dissolved Oxygen Induced by a Tropical Storm Within an Anticyclone in the Northern South China Sea

Tropical storms(TSs)can induce sea surface cooling,freshening,and phytoplankton blooms.The dissolved oxygen(DO)concentration response to TSs within an anticyclone is still unclear due to the rarity of in situ observations.In this study,we investi-gate the variations in DO concentration attributed to TS‘Haitang’within an anticyclonic eddy in the northern South China Sea based on Chinese underwater glider data.DO concentrations have a higher value at the edge of eddy than at the core.Influenced by TS,DO concentrations decrease remarkably in the subsurface layer in all three regions(inside,edge,and outside of the anticyclonic eddy).The mean DO concentrations decrease more at the edge of the anticyclone than those inside the anticyclone.The recovery time of DO concentration after TS is around one week at the edge of the anticyclone and is>10 days within the eddy.Our observations show that the DO concentrations decrease above the subsurface chlorophyll a maxima layer.Quantitative analysis shows that variations in DO concentration are dominated by horizontal advection and vertical advection terms in the subsurface layer.

What Drives the Decadal Variability of Global Tropical Storm Days from 1965 to 2019?

The tropical storm day(TSD)is a combined measure of genesis and lifespan.It reflects tropical cyclone(TC)overall activity,yet its variability has rarely been studied,especially globally.Here we show that the global total TSDs exhibit pronounced interannual(3-6 years)and decadal(10 years)variations over the past five-to-six decades without a significant trend.The leading modes of the interannual and decadal variability of global TSD feature similar patterns in the western Pacific and Atlantic,but different patterns in the Eastern Pacific and the Southern Indian Ocean.The interannual and decadal leading modes are primarily linked to El Ni?o-Southern Oscillation(ENSO)and Pacific Decadal Oscillation(PDO),respectively.The TSDs-ENSO relationship has been steady during the entire 55-year period,but the TSDs-PDO relationship has experienced a breakdown in the 1980 s.We find that the decadal variation of TSD in the Pacific is associated with the PDO sea surface temperature(SST)anomalies in the tropical eastern Pacific(PDO-E),while that in the Atlantic and the Indian Ocean is associated with the PDO SST anomalies in the western Pacific(PDO-W).However,the PDO-E and PDO-W SST anomalies are poorly coupled in the 1980 s,and this"destructive PDO"pattern results in a breakdown of the TSDs-PDO relationship.The results here have an important implication for seasonal to decadal predictions of global TSD.

The Kinetic Energy Budget and Circulation Characteristics of the Tropical Storm Irma during AMEX Phase Ⅱ

By using the data from observation on the Chinese research vessel Xiang Yang Hong No.5 and other sources during AMEX phase II, the kinetic energy budget and circulation characteristics of the tropical storm Irma were analyzed.Irma formed on the ITCZ of the Southern Hemisphere. During the formative stage of the storm, the SE trades and monsoon westerlies on both sides of the ITCZ strengthened, and more importantly, there was a strong divergent flow in upper troposphere. These contributed to the intensification of Irma. At the time when Irma formed, the Richardson number (Ri) in middle and lower troposphere was much smaller than that prior to and post the formation.When Irma intensified rapidly, the area-averaged kinetic energy in the general flow increased in the whole troposphere . The largest contribution came from kinetic energy generation term, -[v.(?)(?)] .indicates that there existed a strong ageostrophic accetration. As to the generation term , the conversion of available potential energy to kinetic energy, - |ωα|, made the largest contribution. This illustrates the importance of internal sources and of the ensemble effect of cumulus convection to the kinetic energy.To the increase of area-averaged eddy kinetic energy during the rapid intensification of Irma, the most impor tant source in the whole troposphere was the dissipation term - [E'], that should be interpreted as the. feeding of eddy kinetic energy from smaller to larger scale disturbances. Another important source was generation term, - [v' (?)(?)'], in the lower troposphere. Rather small contribution came from the energy conversion from the kinetic energy of area-mean flow to eddy kinetic energy. Therefore, the eddy kinetic energy of the developing tropical disturbance extracted both from smaller an, .arger scale motions. The former was much more important than the latter In addition, the disturbance acting as a generator and exporter, generated and exported eddy kinetic energy to the environmental atmosphere.

Analysis of Heavy Rain Process in South Liaoning Province Caused by No. 1105 Tropical Storm "Meari"

[ Objective] The aim was to study the heavy rainstorm by tropical storm ＂Meari＂ in Liaoning. [ Method] Based on the ground data, radar data, numerical report data, encrypted automatic station and NCEP reanalysis data, the heavy rain process by tropical storm ＂ Meari＂ was ana- lyzed. The changes of each physical quantity were discussed while the tropical storm moving northward. [ Result] The subtropical high pressure and Mainland high pressure jointed and maintained, forced ＂ Meari＂ turned northwest. The low-level southeast jet by ＂Meari＂ provided full water trans- mission and layer unstable conditions. The heavy rain mainly distributed in the tongue area of high energy, and the total energy was a key index to predict the rainfall area. [ Condusion] The study provided reference for the report business.

Seasonal Prediction of Tropical Cyclones and Storms over the Southwestern Indian Ocean Region Using the Generalized Linear Models

Tropical cyclones (TCs) and storms (TSs) are among the devastating events in the world and southwestern Indian Ocean (SWIO) in particular. The seasonal forecasting TCs and TSs for December to March (DJFM) and November to May (NM) over SWIO were conducted. Dynamic parameters including vertical wind shear, mean zonal steering wind and vorticity at 850 mb were derived from NOAA (NCEP-NCAR) reanalysis 1 wind fields. Thermodynamic parameters including monthly and daily mean Sea Surface Temperature (SST), Outgoing Longwave Radiation (OLR) and equatorial Standard Oscillation Index (SOI) were used. Three types of Poison regression models (i.e. dynamic, thermodynamic and combined models) were developed and validated using the Leave One Out Cross Validation (LOOCV). Moreover, 2 × 2 square matrix contingency tables for model verification were used. The results revealed that, the observed and cross validated DJFM and NM TCs and TSs strongly correlated with each other (p ≤ 0.02) for all model types, with correlations (r) ranging from 0.62 - 0.86 for TCs and 0.52 - 0.87 for TSs, indicating great association between these variables. Assessment of the model skill for all model types of DJFM and NM TCs and TSs frequency revealed high skill scores ranging from 38% - 70% for TCs and 26% - 72% for TSs frequency, respectively. Moreover, results indicated that the dynamic and combined models had higher skill scores than the thermodynamic models. The DJFM and NM selected predictors explained the TCs and TSs variability by the range of 0.45 - 0.65 and 0.37 - 0.66, respectively. However, verification analysis revealed that all models were adequate for predicting the seasonal TCs and TSs, with high bias values ranging from 0.85 - 0.94. Conclusively, the study calls for more studies in TCs and TSs frequency and strengths for enhancing the performance of the March to May (MAM) and December to October (OND) seasonal rainfalls in the East African (EA) and Tanzania in particular.

Can the tropical storms originated from the Bay of Bengal impact the precipitation and soil moisture over the Tibetan Plateau?

This study investigates the impacts of tropical storms originated from the Bay of Bengal(BOBTSs) on the precipitation and soil moisture over the Tibetan Plateau(TP) in April–June(AMJ) and September–December(SOND) during 1981–2011 based on the best track dataset provided by Joint Typhoon Warning Centre(JTWC). Results indicate that there are about 1.35 BOBTSs influence the TP in each year and most of them occurred in May and October, and the BOBTSs in AMJ influence the TP with larger extension and higher latitudes than those in SOND. The maximum regional precipitation induced by the BOBTSs accounts for more than 50% for the total precipitation in the corresponding month and about 20% for the season. Further analysis reveals that the surface soil moisture anomalies induced by the BOBTSs can persist only 20–25 days in AMJ, and the case is also true for the snow depth in SOND. Numerical simulations by using the regional climate model of Weather Research and Forecasting(WRF) suggest that the soil moisture anomalies in the sub-surface can last 2 months whereas for the surface it can persist only about 20 days, which agrees well with the observation analysis. Overall, the effect of the preceding BOBTSs on the snow depth and soil moisture anomalies over the TP cannot maintain to summer, and there is no robust connection between the BOBTSs and summer precipitation anomalies in East China. Moreover, since the mid-1990 s, the spring rainfall induced by the BOBTSs over the TP seems to be enhanced to a certain degree because of the intensified BOBTSs.

Tropical storm-forced near-inertial energy dissipation in the southeast continental shelf region of Hainan Island

Near-inertial motion is an important dynamic process in the upper ocean and plays a significant role in mass, heat, and energy transport across the thermocline. In this study, the dissipation of wind-induced near-inertial energy in the thermocline is investigated by using observation data collected in July and August 2005 during the tropical storm Washi by a moored system at(19°35′N, 112°E) in the continental shelf region off Hainan Island. In the observation period, the near-inertial part dominated the observed ocean kinetic energy and about 80% of the near-inertial energy dissipated in the upper layer. Extremely strong turbulent mixing induced by near-inertial wave was observed in the thermocline, where the turbulent energy dissipation rate increased by two orders of magnitude above the background level. It is found that the energy loss of near-inertial waves in the thermocline is mainly in the large-scales. This is different from the previous hypothesis based on "Kolmogorov cascade" turbulence theory that the kinetic energy is dissipated mainly by small-scale motions.

A New Prediction Model for Tropical Storm Frequency over the Western North Pacific Using Observed Winter-Spring Precipitation and Geopotential Height at 500 hPa

A new seasonal prediction model for annual tropical storm numbers （ATSNs） over the western North Pacific was developed using the preceding January-February （JF） and April-May （AM） grid-point data at a resolution of 2.5° × 2.5°. The JF and AM mean precipitation and the AM mean 500-hPa geopotential height in the Northern Hemisphere, together with the JF mean 500-hPa geopotential height in the Southern Hemisphere, were employed to compose the ATSN forecast model via the stepwise multiple linear regression technique. All JF and AM mean data were confined to the Eastern ttemisphere. We established two empirical prediction models for ATSN using the ERA40 reanalysis and NCEP reanalysis datasets, respectively, together with the observed precipitation. The performance of the models was verified by cross-validation. Anomaly correlation coefficients （ACC） at 0.78 and 0.74 were obtained via comparison of the retrospective predictions of the two models and the observed ATSNs from 1979 to 2002. The multi-year mean absolute prediction errors were 3.0 and 3.2 for the two models respectively, or roughly 10% of the average ATSN. In practice, the final prediction was made by averaging the ATSN predictions of the two models. This resulted in a higher score, with ACC being further increased to 0.88, and the mean absolute error reduced to 1.92, or 6.13% of the average ATSN.

Impacts of Four Types of ENSO Events on Tropical Cyclones Making Landfall over China's Mainland Based on Three Best-track Datasets

Impacts of EI Nino Modoki （ENM）, La Nina Modoki （LNM）, canonical EI Nifio （CEN） and canonical La Nifia （CLN） on tropical cyclones （TCs） that made landfall over China's Mainland during 1951-2011 are analysed using best-track data from China, the USA and Japan. Relative to cold phase years （LNM and CLN）, landfalling TCs in warm years （ENM and CEN） have a farther east genesis location, as well as longer track lengths and durations, both in total and before landfall. ENM demonstrates the highest landfall frequency, most northerly mean landfall position, and shortest after-landfall sustainability （track length and duration）, which indicate a more frequent and extensive coverage of China's Mainland by TCs, but with shorter after-landfall influence. CEN has low landfall frequency and the most southerly mean landfall location. LNM has the most westerly genesis location, being significantly farther west than the 1951-2011 average and leading to short mean track lengths and durations both in total or before landfall, all of which are significantly shorter than the 1951-2011 average. Variations in the low-level wind anomaly, vertical wind shear, mid-level relative humidity, steering flow, the monsoon trough and the western Pacific subtropical high （WPSH） can to some extent account for the features of frequency, location, track length and duration of landfalling TCs. Since ENSO Modoki is expected to become more frequent in the near future, the results for ENSO Modoki presented in this paper are of particular significance.

A Potential High-Score Scheme for the Prediction of Atlantic Storm Activity

A new empirical approach for the seasonal prediction of annual Atlantic tropical storm number (ATSN) was developed using precipitation and 500 hPa geopotential height data from the preceding January February and April May.The 2.5°×2.5° resolution reanalysis data from both the US National Center for Environmental Prediction/the National Center for Atmospheric Research (NCEP/NCAR) and the European Center for Medium-Range Weather Forecasting (ECMWF) were applied.The model was cross-validated using data from 1979 2002.The ATSN predictions from the two reanalysis models were correlated with the observations with the anomaly correlation coefficients (ACC) of 0.79 (NCEP/NCAR) and 0.78 (ECMWF) and the multi-year mean absolute prediction errors (MAE) of 1.85 and 1.76,respectively.When the predictions of the two models were averaged,the ACC increased to 0.90 and the MAE decreased to 1.18,an exceptionally high score.Therefore,this new empirical approach has the potential to improve the operational prediction of the annual tropical Atlantic storm frequency.

Asymmetric Distribution of Convection in Tropical Cyclones over the Western North Pacific Ocean

Forecasts of the intensity and quantitative precipitation of tropical cyclones（TCs） are generally inaccurate, because the strength and structure of a TC show a complicated spatiotemporal pattern and are affected by various factors. Among these, asymmetric convection plays an important role. This study investigates the asymmetric distribution of convection in TCs over the western North Pacific during the period 2005–2012, based on data obtained from the Feng Yun 2（FY2）geostationary satellite. The asymmetric distributions of the incidence, intensity and morphology of convections are analyzed.Results show that the PDFs of the convection occurrence curve to the azimuth are sinusoidal. The rear-left quadrant relative to TC motion shows the highest occurrence rate of convection, while the front-right quadrant has the lowest. In terms of intensity, weak convections are favored in the front-left of a TC at large distances, whereas strong convections are more likely to appear to the rear-right of a TC within a 300 km range. More than 70% of all MCSs examined here are elongated systems, and meso-β enlongated convective systems（MβECSs） are the most dominant type observed in the outer region of a TC. Smaller MCSs tend to be more concentrated near the center of a TC. While semi-circular MCSs [MβCCSs, MCCs（mesoscale convective complexes）] show a high incidence rate to the rear of a TC, elongated MCSs [MβECSs, PECSs（persistent elongated convective systems）] are more likely to appear in the rear-right quadrant of a TC within a range of 400 km.

Nourishment and disaster mitigation efficiency of feeding sand on the dry section of a dissipative beach

To explore the nourishment effect and disaster reduction efficiency of a fully dissipative dry beach under the impact of storms,this paper uses the measured topography and hydrodynamic data to establish a one-dimensional numerical model of the XBeach beach profile.By numerically modeling the change in the nourished profile for different dry beach widths under normal waves and storm conditions and the recovery process of the profile after the storm,the degree of response in dry beach nourishment for the fully dissipative beach is analyzed.The results show that under normal wave conditions,the response of the nourished dry beach is obvious.Sediment on the dry beach erodes heavily,and the shoreline moves landward over a long distance.With the increase in the width and size of the dry beach,the wave height at the bottom of the backshore profile decreases,the wave height attenuation rate increases continuously,and the wave elimination effect is remarkable.When the storm incident wave intensifies,the wave height attenuation rate of the nourished dry beach decreases,indicating that the smaller the storm intensity is,the more significant the wave reduction effect of the nourished dry beach is.At the same time,different profile arrangements of nourished dry beaches suffer from different degrees of erosion under storm conditions,with significant changes in profile morphology.With intensified storm action,the intensity of sediment erosion in the nourished dry beach increases,the nourishment is weakened,and the recovery effect of the profile after the storm is not obvious.The results of the numerical modeling highlight that the dry beach nourishment method can resist storms to a certain extent,but the overall effect is relatively limited.

THE TYPHOON DISASTERS AND RELATED EFFECTS IN CHINA

China is one of the countries which were affected very seriously by tropical cyclones. In this paper, the active features of tropical cyclones which affected and landfell over China, the distinguishing characteristics of typhoon disasters and related formation laws have been studied, and the impact of trphoon disasters on China's socio-economic development have been discussed. The study reveals that typhoon disasters which affected China are characterized by high freqency in occurrence, violent in sudden occurrence, remarkable effects in China,widescope in impact and severe intensities in disasters, and this type of disaster was caused by huge gales, rainstorms, storm surges and reatal chain-disasters.Typhoon disasters have not only caused great casualties but also exerted severe effects on every economic departments in China. There is an annual increasing tendency in direct economic loss caused by taphoon disasters and since 1990, the annual average economic loss has totalled up to over lo billion RMB yuan.