Estimating horizontal winds in and around typhoons is important for improved monitoring and prediction of typhoons and mitigating their damages.Here,we present a new algorithm for estimating typhoon winds using multip...Estimating horizontal winds in and around typhoons is important for improved monitoring and prediction of typhoons and mitigating their damages.Here,we present a new algorithm for estimating typhoon winds using multiple satellite observations and its application to Typhoon Soulik(2018).Four kinds of satellite remote sensing data,along with their relationship to typhoon intensity,derived statistically from hundreds of historical typhoon cases,were merged into the final product of typhoon wind(MT wind):(1)geostationarysatellite-based infrared images(IR wind),(2)passive microwave sounder(MW wind),(3)feature-tracked atmospheric motion vectors,and (4)scatterometer-based sea surface winds(SSWs).The algorithm was applied to two cases(A and B)of Typhoon Soulik and validated against SSWs independently retrieved from active microwave synthetic aperture radar(SAR)and microwave radiometer(AMSR2)images,and vertical profiles of wind speed derived from reanalyzed data and dropsonde observations.For Case A(open ocean),the algorithm estimated the realistic maximum wind,radius of maximum wind,and radius of 15 m/s,which could not be estimated using the reanalysis data,demonstrating reasonable and practical estimates.However,for Case B(when the typhoon rapidly weakened just before making landfall in the Korean Peninsula),the algorithm significantly overestimated the parameters,primarily due to the overestimation of typhoon intensity.Our study highlights that realistic typhoon winds can be monitored continuously in real-time using multiple satellite observations,particularly when typhoon intensity is reasonably well predicted,providing timely analysis results and products of operational importance.展开更多
To understand structural changes and forecast error,a case study of binary typhoons in the western North Pacific(WNP)of 2018 was investigated using best track and reanalysis data.Soulik was generated on August 16 and ...To understand structural changes and forecast error,a case study of binary typhoons in the western North Pacific(WNP)of 2018 was investigated using best track and reanalysis data.Soulik was generated on August 16 and Cimaron was generated on August 18,respectively.The 19 th typhoon Soulik and 20 th typhoon Cimaron co-existed from August 18 to 24 and approached each other.Soulik was located on the western side and Cimaron was located on the eastern side of the WNP.They were located approximately 1300 km from each other at 00 UTC August 22.The Soulik structure began changing around August 22 and became weak and slow,while Cimaron maintained its intensity,size,and moving speed.This observational evidence is likely caused by the binary interaction between two typhoons within a certain distance and environmental steering flow,such as the location of the North Pacific high and strong jet stream of the northern flank of the North Pacific high.Soulik was initially forecasted to make landfall and reach Seoul;however,its track changed from northward to northeastward from August 21 to 23 according to both official guidance and unified model(UM).Four global numerical weather prediction models forecasted different tracks of Soulik.UM and JGSM forecasted a northward track whereas ECMWF and GFS showed a northeastward track for 12 UTC August 21 through 12 UTC August 24.The latter models were similar to the best track.The track forecast error and spread of Soulik were larger than those of Cimaron.The mean absolute error of the maximum wind speed of Soulik was similar to the average of total typhoons in 2018.展开更多
Since January 2012,the National Satellite Ocean Application Service has released operational wind products from the HY-2A scatterometer(HY2-SCAT),using the maximum-likelihood estimation(MLE) method with a median filte...Since January 2012,the National Satellite Ocean Application Service has released operational wind products from the HY-2A scatterometer(HY2-SCAT),using the maximum-likelihood estimation(MLE) method with a median filter. However,the quality of the winds retrieved from HY2-SCAT depends on the sub-satellite cross-track location,and poor azimuth separation in the nadir region causes particularly low-quality wind products in this region. However,an improved scheme,i.e.,a multiple solution scheme(MSS) with a two-dimensional variational analysis method(2DVAR),has been proposed by the Royal Netherlands Meteorological Institute to overcome such problems. The present study used the MSS in combination with a 2DVAR technique to retrieve wind data from HY2-SCAT observations. The parameter of the empirical probability function,used to indicate the probability of each ambiguous solution being the "true" wind,was estimated based on HY2-SCAT data,and the 2DVAR method used to remove ambiguity in the wind direction. A comparison between MSS and ECMWF winds showed larger deviations at both low wind speeds(below 4 m/s) and high wind speeds(above 17 m/s),whereas the wind direction exhibited lower bias and good stability,even at high wind speeds greater than 24 m/s. The two HY2-SCAT wind data sets,retrieved by the standard MLE and the MSS procedures were compared with buoy observations. The RMS error of wind speed and direction were 1.3 m/s and 17.4°,and 1.3 m/s and 24.0° for the MSS and MLE wind data,respectively,indicating that MSS wind data had better agreement with the buoy data. Furthermore,the distributions of wind fields for a case study of typhoon Soulik were compared,which showed that MSS winds were spatially more consistent and meteorologically better balanced than MLE winds.展开更多
基金supported by the‘Development of Typhoon and Ocean Applications’project,funded by ETRI,which is a subproject of the‘Development of Geostationary Meteorological Satellite Ground Segment(NMSC-2019-01)’program funded by NMSC of KMAThis research was a part of the project titled“Construction of Ocean Research Station and their Application Studies”funded by the Ministry of Oceans and Fisheries in republic of Korea.
文摘Estimating horizontal winds in and around typhoons is important for improved monitoring and prediction of typhoons and mitigating their damages.Here,we present a new algorithm for estimating typhoon winds using multiple satellite observations and its application to Typhoon Soulik(2018).Four kinds of satellite remote sensing data,along with their relationship to typhoon intensity,derived statistically from hundreds of historical typhoon cases,were merged into the final product of typhoon wind(MT wind):(1)geostationarysatellite-based infrared images(IR wind),(2)passive microwave sounder(MW wind),(3)feature-tracked atmospheric motion vectors,and (4)scatterometer-based sea surface winds(SSWs).The algorithm was applied to two cases(A and B)of Typhoon Soulik and validated against SSWs independently retrieved from active microwave synthetic aperture radar(SAR)and microwave radiometer(AMSR2)images,and vertical profiles of wind speed derived from reanalyzed data and dropsonde observations.For Case A(open ocean),the algorithm estimated the realistic maximum wind,radius of maximum wind,and radius of 15 m/s,which could not be estimated using the reanalysis data,demonstrating reasonable and practical estimates.However,for Case B(when the typhoon rapidly weakened just before making landfall in the Korean Peninsula),the algorithm significantly overestimated the parameters,primarily due to the overestimation of typhoon intensity.Our study highlights that realistic typhoon winds can be monitored continuously in real-time using multiple satellite observations,particularly when typhoon intensity is reasonably well predicted,providing timely analysis results and products of operational importance.
基金the“Research and Development for Numerical Weather Prediction”and“Support to Enhancement of Convergence Technology of Analysis and Forecast on Severe Weather”under Grant(KMA2018-00122)the Korea Meteorological Administration Research and Development Program
文摘To understand structural changes and forecast error,a case study of binary typhoons in the western North Pacific(WNP)of 2018 was investigated using best track and reanalysis data.Soulik was generated on August 16 and Cimaron was generated on August 18,respectively.The 19 th typhoon Soulik and 20 th typhoon Cimaron co-existed from August 18 to 24 and approached each other.Soulik was located on the western side and Cimaron was located on the eastern side of the WNP.They were located approximately 1300 km from each other at 00 UTC August 22.The Soulik structure began changing around August 22 and became weak and slow,while Cimaron maintained its intensity,size,and moving speed.This observational evidence is likely caused by the binary interaction between two typhoons within a certain distance and environmental steering flow,such as the location of the North Pacific high and strong jet stream of the northern flank of the North Pacific high.Soulik was initially forecasted to make landfall and reach Seoul;however,its track changed from northward to northeastward from August 21 to 23 according to both official guidance and unified model(UM).Four global numerical weather prediction models forecasted different tracks of Soulik.UM and JGSM forecasted a northward track whereas ECMWF and GFS showed a northeastward track for 12 UTC August 21 through 12 UTC August 24.The latter models were similar to the best track.The track forecast error and spread of Soulik were larger than those of Cimaron.The mean absolute error of the maximum wind speed of Soulik was similar to the average of total typhoons in 2018.
基金Supported by the National High Technology Research and Development Program of China(863 Program)(No.2013AA09A505)the Shandong Joint Fund for Marine Science Research Centers(No.U1406404)+1 种基金the National Natural Science Foundation of China(No.41106152)he National Key Technology R&D Program of China(No.2013BAD13B01)
文摘Since January 2012,the National Satellite Ocean Application Service has released operational wind products from the HY-2A scatterometer(HY2-SCAT),using the maximum-likelihood estimation(MLE) method with a median filter. However,the quality of the winds retrieved from HY2-SCAT depends on the sub-satellite cross-track location,and poor azimuth separation in the nadir region causes particularly low-quality wind products in this region. However,an improved scheme,i.e.,a multiple solution scheme(MSS) with a two-dimensional variational analysis method(2DVAR),has been proposed by the Royal Netherlands Meteorological Institute to overcome such problems. The present study used the MSS in combination with a 2DVAR technique to retrieve wind data from HY2-SCAT observations. The parameter of the empirical probability function,used to indicate the probability of each ambiguous solution being the "true" wind,was estimated based on HY2-SCAT data,and the 2DVAR method used to remove ambiguity in the wind direction. A comparison between MSS and ECMWF winds showed larger deviations at both low wind speeds(below 4 m/s) and high wind speeds(above 17 m/s),whereas the wind direction exhibited lower bias and good stability,even at high wind speeds greater than 24 m/s. The two HY2-SCAT wind data sets,retrieved by the standard MLE and the MSS procedures were compared with buoy observations. The RMS error of wind speed and direction were 1.3 m/s and 17.4°,and 1.3 m/s and 24.0° for the MSS and MLE wind data,respectively,indicating that MSS wind data had better agreement with the buoy data. Furthermore,the distributions of wind fields for a case study of typhoon Soulik were compared,which showed that MSS winds were spatially more consistent and meteorologically better balanced than MLE winds.
