Based on the analysis of tropical cyclone （TC） database in the Northwest Pacific （NWP） from 1945 to 2008, we not only extract the temporal variation of TC intensity and frequency, but also give their spatial distr...Based on the analysis of tropical cyclone （TC） database in the Northwest Pacific （NWP） from 1945 to 2008, we not only extract the temporal variation of TC intensity and frequency, but also give their spatial distribution both in the NWP and in the South China Sea （SCS）. The results show that there is an observational increase of TC activities, which manifests as the enhancement of the power dissipation index （PDI） and the growth of TC frequency, especially for typhoons and strong typhoons. The inbomogeneous spatial distributions of TC frequency and intensity are also provided both in the NWP and in the SCS. For example, the region of Zhongsha Islands and Dongsha Islands in the SCS （15°-22°N, 115° - 120°E）, west to the Philippine Islands is the place with frequent occurrence of strong typhoons, among which the wind speed of 7 TCs in 64 years exceeds 60 m/s.展开更多
According to Argo profiles and one-dimensional Price-Weller-Pinkel models, the oceanic barrier layer variation induced by tropical cyclones is adequately analyzed in the Northwest Pacific. Results show that tropical c...According to Argo profiles and one-dimensional Price-Weller-Pinkel models, the oceanic barrier layer variation induced by tropical cyclones is adequately analyzed in the Northwest Pacific. Results show that tropical cyclones mainly aff ect the oceanic barrier layer through intensifying and weakening pre-existed barrier layer. The former even may generate new one after tropical cyclones’ passage. The latter can make pre-existed one disappear. Local wind stress and precipitation, the dominant factors, primarily determine the variation of barrier layer. Negative eff ects of wind mainly focus on the north of 20°N. This phenomenon is more meaningful for slow tropical cyclones. Conversely, positive eff ects of wind and precipitation center on the south of 20°N in the Northwest Pacific. Some data indicate that the barrier layer variation is also closely related with initial mixed layer depth and barrier layer thickness.展开更多
The evolution of thermohaline structure at the upper ocean during three tropical cyclones(TCs)in the Northwest Pacific was studied in this study based on successive observation by two new-style underwater gliders duri...The evolution of thermohaline structure at the upper ocean during three tropical cyclones(TCs)in the Northwest Pacific was studied in this study based on successive observation by two new-style underwater gliders during fall 2018.These remote-controllable gliders with CTD sensor enabled us to explore high frequency responses of temperature,salinity,mixed and barrier layers in the upper ocean to severe TCs in this area.Results showed that three significant cooling-to-warming and stratification destructing-to-reconstructing processes at the mixed layer occurred during the lives of three TCs.The maximal cooling of SST all reached≥0.5℃although TCs with different intensities had different minimal distances to the observed area.Under potential impacts of solar radiation,tide and inertial motions,the mixed layer depth possessed significant high-frequency fluctuations during TC periods.In addition,barrier layers appeared and vanished quickly during TCs,accompanied with varied temperature inversion processes.展开更多
In this study, we investigated the influence of the Indian Ocean Dipole (IOD) on the interannual variability of tropical cyclone (TC) activity over the western North Pacific (WNP) during autumn (September November) fr...In this study, we investigated the influence of the Indian Ocean Dipole (IOD) on the interannual variability of tropical cyclone (TC) activity over the western North Pacific (WNP) during autumn (September November) from 1961 2015. We found the number of TCs making landfall in China to be significantly negatively correlated with the IOD index, which can be attributed to shifts in the location of TC formation together with the abnormal steering flow at 500 hPa. During negative IOD autumns, TC genesis regions move obviously westward due to the westward retreat of the WNP monsoon trough. The TC activity is remarkably enhanced near South China coastal areas, which is due to a contiguous 500-hPa subtropical ridge. In contrast, during positive IOD autumns, TC genesis positions obviously shift eastward and more TCs tend to exhibit recurvature around 130 E or a westward path south of 15 N led by an equatorward movement of the 500-hPa subtropical ridge with a break near 125 E. In our examination of large-scale circula- tion, we found a pair of equator-symmetric anticyclones in the lower troposphere resulting from variations in the large-scale Walker circulation induced by the anomalous sea surface temperature (SST) associated with a positive IOD. The resulting Philippines anti- cyclonic anomalies are closely related to the variability of the monsoon trough over the WNP region. Furthermore, the variations in the steering flow can be explained by the suppressed (enhanced) convective activities around the Philippines and the weakened (strengthened) local meridional circulation over East Asia in positive (negative) IOD years.展开更多
A statistic analysis has been conducted of the climatological features of Northwest Pacific typhoons over the past 50 years based on historical record from 1949 to 1996. The objects of study include theannual variatio...A statistic analysis has been conducted of the climatological features of Northwest Pacific typhoons over the past 50 years based on historical record from 1949 to 1996. The objects of study include theannual variation, distribution by season and intensity, and category of motion. Additional investigation is made ofhow the typhoon varies in terms of the geographic location of generation and the relationship between the intensity and the source area. It is revealed that most of the strong typhoons originate over waters east of 125°E withthe strongest group coming from the Mariana Is. Besides, distribution of landing typhoons is given with respect toseason and latitude. Statistics of central pressure at the point of landfall suggests that typhoons making landfallson the provinces of Zhejiang and Fujian are less frequent than in south China but have relatively high intensity.展开更多
An observational study focusing on the contribution of tropical cyclones(TCs)that form over the western North Pacific(WNP)to the synoptic-scale transient eddy activity(STEA)over the North Pacific during the boreal aut...An observational study focusing on the contribution of tropical cyclones(TCs)that form over the western North Pacific(WNP)to the synoptic-scale transient eddy activity(STEA)over the North Pacific during the boreal autumn and early winter in the period 1979–2019 is presented in this paper.Statistical results show that WNP TCs entering the midlatitudinal North Pacific provide significant positive effects on the pentad mean strength of STEA,which is primarily concentrated over the Kuroshio/Oyashio Extensions(KOE)and regions from east of Japan to 160°W in the lower and midto-upper troposphere,respectively.TC intensity is highly indicative of the subsequent STEA with a correlation coefficient of 0.37/0.33/0.45 at 300 hPa/500 hPa/850 hPa exceeding the 99%confidence level for the period 1979–2019.The strength of STEA in the upper troposphere associated with TCs presents a more significant linear growth with TC intensity than that at the mid-to-lower levels after the cyclones enter the KOE region,suggesting that the impact of TCs on STEA gradually increases with height.Further analyses reveal that the contribution of TCs accounts for 4%–6%of the total STEA change over the KOE region during the late autumn and early winter.In addition,the influence of TCs on STEA experienced an interdecadal decrease from the early 2000 s through the early 2010 s.展开更多
Based on the best-track dataset from the Shanghai Typhoon Institute/China Meteorological Administration,the paper provides a compre-hensive summary and analysis of tropical cyclone(TC)activities in the Western North P...Based on the best-track dataset from the Shanghai Typhoon Institute/China Meteorological Administration,the paper provides a compre-hensive summary and analysis of tropical cyclone(TC)activities in the Western North Pacific(WNP)and the South China Sea(SCS)for 2022.Using the historical climatology from 1951 to 2020,the anomalous conditions during 2022 in TC frequency,origin locations,tracks,intensity,and duration for the entire ocean basin as well as landfall events in China are examined.Results show that the overall TC frequency is slightly lower than normal,but the multiple TC events have a very high frequency of occurrence.Origin locations of TCs,which mark the starting points of their paths,show a large westward and northward deviation from climatology.Around 40%of the named TCs exhibit a shift in their direction of movement from westerly to easterly.Additionally,comparisons of the means,medians,upper and lower quartiles all indicate that the intensity of TCs in 2022 is generally lower than the climatology,with the duration of TCs at tropical storm intensity or above being shorter than usual.A notable observation is the fewer incidence of TC landfalls in China,but with a geographical concentration in Guangdong Province.These anomalous annual TC activities are influenced by related atmospheric and oceanic environmental conditions modulated by multi-scale climate variability.Thefindings provide useful information for enhancing disaster mitigation strategies in the Asia-Pacific region.展开更多
Based on geographic division over the western North Pacific(WNP),the interdecadal relationships between summer monsoon,sea surface temperature(SST) and tropical cyclones activity(including number,track and intensity) ...Based on geographic division over the western North Pacific(WNP),the interdecadal relationships between summer monsoon,sea surface temperature(SST) and tropical cyclones activity(including number,track and intensity) are examined.In the past several decades,the western Pacific subtropical high(WPSH) and tropical westerlies contribute to the interdecadal variation of TC number in the northwest and southeast of WNP respectively.The increased TC occurrence density to the east of Philippines related to TC track appears during the 1990s,in terms of both steer flow induced by WPSH and genesis location.From the interdecadal viewpoint,the tendency of TC intensity,measured by averaged accumulated cyclone energy,does well agree with that of SST,implying that SST plays an important role in TC intensity.展开更多
基金supported by the National High Technology Research and Development Program of China(863 Program,Grant No.2006AA09A103-4)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX-YW-L02)
文摘Based on the analysis of tropical cyclone （TC） database in the Northwest Pacific （NWP） from 1945 to 2008, we not only extract the temporal variation of TC intensity and frequency, but also give their spatial distribution both in the NWP and in the South China Sea （SCS）. The results show that there is an observational increase of TC activities, which manifests as the enhancement of the power dissipation index （PDI） and the growth of TC frequency, especially for typhoons and strong typhoons. The inbomogeneous spatial distributions of TC frequency and intensity are also provided both in the NWP and in the SCS. For example, the region of Zhongsha Islands and Dongsha Islands in the SCS （15°-22°N, 115° - 120°E）, west to the Philippine Islands is the place with frequent occurrence of strong typhoons, among which the wind speed of 7 TCs in 64 years exceeds 60 m/s.
基金Supported by the National Program on Global Change and Air-Sea Interaction(No.GASI-IPOVAI-04)the National Key Research and Development Program of China(No.2017YFC1404000)the National Natural Science Foundation of China(No.41276001)
文摘According to Argo profiles and one-dimensional Price-Weller-Pinkel models, the oceanic barrier layer variation induced by tropical cyclones is adequately analyzed in the Northwest Pacific. Results show that tropical cyclones mainly aff ect the oceanic barrier layer through intensifying and weakening pre-existed barrier layer. The former even may generate new one after tropical cyclones’ passage. The latter can make pre-existed one disappear. Local wind stress and precipitation, the dominant factors, primarily determine the variation of barrier layer. Negative eff ects of wind mainly focus on the north of 20°N. This phenomenon is more meaningful for slow tropical cyclones. Conversely, positive eff ects of wind and precipitation center on the south of 20°N in the Northwest Pacific. Some data indicate that the barrier layer variation is also closely related with initial mixed layer depth and barrier layer thickness.
基金The National Key R&D Program of China under contract No.2018YFC0309800the National Natural Science Foundation of China under contract Nos 41666001,41576006,41676015 and U1709202+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA13030302the Chinese Academy of Sciences Frontier Basic Research Project under contract No.QYJC201910
文摘The evolution of thermohaline structure at the upper ocean during three tropical cyclones(TCs)in the Northwest Pacific was studied in this study based on successive observation by two new-style underwater gliders during fall 2018.These remote-controllable gliders with CTD sensor enabled us to explore high frequency responses of temperature,salinity,mixed and barrier layers in the upper ocean to severe TCs in this area.Results showed that three significant cooling-to-warming and stratification destructing-to-reconstructing processes at the mixed layer occurred during the lives of three TCs.The maximal cooling of SST all reached≥0.5℃although TCs with different intensities had different minimal distances to the observed area.Under potential impacts of solar radiation,tide and inertial motions,the mixed layer depth possessed significant high-frequency fluctuations during TC periods.In addition,barrier layers appeared and vanished quickly during TCs,accompanied with varied temperature inversion processes.
基金supported by Open Fund of the Key Laboratory of Ocean Circulation and Waves (No. KLOCW 1902)Chinese Academy of Sciences and the National Natural Science Foundation of China (No. 41505050)
文摘In this study, we investigated the influence of the Indian Ocean Dipole (IOD) on the interannual variability of tropical cyclone (TC) activity over the western North Pacific (WNP) during autumn (September November) from 1961 2015. We found the number of TCs making landfall in China to be significantly negatively correlated with the IOD index, which can be attributed to shifts in the location of TC formation together with the abnormal steering flow at 500 hPa. During negative IOD autumns, TC genesis regions move obviously westward due to the westward retreat of the WNP monsoon trough. The TC activity is remarkably enhanced near South China coastal areas, which is due to a contiguous 500-hPa subtropical ridge. In contrast, during positive IOD autumns, TC genesis positions obviously shift eastward and more TCs tend to exhibit recurvature around 130 E or a westward path south of 15 N led by an equatorward movement of the 500-hPa subtropical ridge with a break near 125 E. In our examination of large-scale circula- tion, we found a pair of equator-symmetric anticyclones in the lower troposphere resulting from variations in the large-scale Walker circulation induced by the anomalous sea surface temperature (SST) associated with a positive IOD. The resulting Philippines anti- cyclonic anomalies are closely related to the variability of the monsoon trough over the WNP region. Furthermore, the variations in the steering flow can be explained by the suppressed (enhanced) convective activities around the Philippines and the weakened (strengthened) local meridional circulation over East Asia in positive (negative) IOD years.
文摘A statistic analysis has been conducted of the climatological features of Northwest Pacific typhoons over the past 50 years based on historical record from 1949 to 1996. The objects of study include theannual variation, distribution by season and intensity, and category of motion. Additional investigation is made ofhow the typhoon varies in terms of the geographic location of generation and the relationship between the intensity and the source area. It is revealed that most of the strong typhoons originate over waters east of 125°E withthe strongest group coming from the Mariana Is. Besides, distribution of landing typhoons is given with respect toseason and latitude. Statistics of central pressure at the point of landfall suggests that typhoons making landfallson the provinces of Zhejiang and Fujian are less frequent than in south China but have relatively high intensity.
基金sponsored jointly by the National Key Basic Research Program(2018YFC1505905)National Natural Science Foundation of China(Grant Nos.41975090,41922033,41675077,and 42005025)+2 种基金Scientific Research Program of National University of Defense Technology(18/19-QNCXJ)the Jiangsu Collaborative Innovation Center for Climate Change in Nanjing Universitythe Jiangsu Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters。
文摘An observational study focusing on the contribution of tropical cyclones(TCs)that form over the western North Pacific(WNP)to the synoptic-scale transient eddy activity(STEA)over the North Pacific during the boreal autumn and early winter in the period 1979–2019 is presented in this paper.Statistical results show that WNP TCs entering the midlatitudinal North Pacific provide significant positive effects on the pentad mean strength of STEA,which is primarily concentrated over the Kuroshio/Oyashio Extensions(KOE)and regions from east of Japan to 160°W in the lower and midto-upper troposphere,respectively.TC intensity is highly indicative of the subsequent STEA with a correlation coefficient of 0.37/0.33/0.45 at 300 hPa/500 hPa/850 hPa exceeding the 99%confidence level for the period 1979–2019.The strength of STEA in the upper troposphere associated with TCs presents a more significant linear growth with TC intensity than that at the mid-to-lower levels after the cyclones enter the KOE region,suggesting that the impact of TCs on STEA gradually increases with height.Further analyses reveal that the contribution of TCs accounts for 4%–6%of the total STEA change over the KOE region during the late autumn and early winter.In addition,the influence of TCs on STEA experienced an interdecadal decrease from the early 2000 s through the early 2010 s.
基金supported by the Shanghai Science and Technology Commission Project(23DZ1204701)the National Natural Science Foundation of China(42105042)。
文摘Based on the best-track dataset from the Shanghai Typhoon Institute/China Meteorological Administration,the paper provides a compre-hensive summary and analysis of tropical cyclone(TC)activities in the Western North Pacific(WNP)and the South China Sea(SCS)for 2022.Using the historical climatology from 1951 to 2020,the anomalous conditions during 2022 in TC frequency,origin locations,tracks,intensity,and duration for the entire ocean basin as well as landfall events in China are examined.Results show that the overall TC frequency is slightly lower than normal,but the multiple TC events have a very high frequency of occurrence.Origin locations of TCs,which mark the starting points of their paths,show a large westward and northward deviation from climatology.Around 40%of the named TCs exhibit a shift in their direction of movement from westerly to easterly.Additionally,comparisons of the means,medians,upper and lower quartiles all indicate that the intensity of TCs in 2022 is generally lower than the climatology,with the duration of TCs at tropical storm intensity or above being shorter than usual.A notable observation is the fewer incidence of TC landfalls in China,but with a geographical concentration in Guangdong Province.These anomalous annual TC activities are influenced by related atmospheric and oceanic environmental conditions modulated by multi-scale climate variability.Thefindings provide useful information for enhancing disaster mitigation strategies in the Asia-Pacific region.
基金Supported by Special Scientific Research Project for Public Interest (Grant No.GYHY200806009)National Basic Research Program of China (Grant No.2009CB421505)
文摘Based on geographic division over the western North Pacific(WNP),the interdecadal relationships between summer monsoon,sea surface temperature(SST) and tropical cyclones activity(including number,track and intensity) are examined.In the past several decades,the western Pacific subtropical high(WPSH) and tropical westerlies contribute to the interdecadal variation of TC number in the northwest and southeast of WNP respectively.The increased TC occurrence density to the east of Philippines related to TC track appears during the 1990s,in terms of both steer flow induced by WPSH and genesis location.From the interdecadal viewpoint,the tendency of TC intensity,measured by averaged accumulated cyclone energy,does well agree with that of SST,implying that SST plays an important role in TC intensity.
