Proceedings of ERAD (2004): 315–319 c  Copernicus GmbH 2004 ERAD 2004 Study on the extratropical transition of typhoon 0310 (Etau) observed by wind profilers and weather radars H. Fujita 1 , M. Teshiba 1 , Y. Umemoto 1 , Y. Shibagaki 2 , H. Hashiguchi 1 , M. D.Yamanaka 3,4 , and S. Fukao 1 1 Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan 2 Osaka Electro-Communication University, Osaka, Japan 3 Graduate School of Science and Technology, Kobe University, Kobe, Japan 4 Frontier Research Center for Global Change, Tokyo, Japan Abstract. As the typhoon observation technique using a wind profiler is gradually developed, it became possible to see the detailed structures of wind behavior in the vicinity of the typhoon center these days. In this study, we examined the extratropical transition of Typhoon 0310 (Etau) in the aspects of wind behavior and precipitation observed with Wind pro- filer Network and Data Acquisition System (WINDAS) op- erated by Japan Meteorological Agency (JMA). There was a wide precipitating region in the front side, that is, in the north quadrant of the typhoon. As the typhoon was approaching to the main island of Japan, the precipitating region became gradually narrow. The convective precipitating clouds were observed in the vicinity of typhoon center. Strong cyclonic wind in the front side of the typhoon was observed. The cyclonic wind was getting weak and the strongest cyclonic wind region went away from typhoon center as the typhoon moved to the north-eastward. We observed inflow in lower altitude region (below 2 km) and outflow in higher altitude region (above 2 km). Both the inflow and outflow were get- ting stronger as the typhoon moved to north-eastward. 1 Introduction There are several structural differences between tropical cy- clone (typhoon) and extratropical cyclone. In spite of the ex- istence of these differences, tropical cyclone gradually tran- sits into extratropical cyclone in mid-latitudes. The process of the extratropical transition of tropical cyclone is not com- pletely understood yet. In order to understand the structural variation accompanied with an extratropical transition, it is necessary to observe the detailed structure of typooon, espe- cially in the vicinity of typhoon center. However, this de- tailed structure cannot be seen by the conventional obser- vation technique such as aircrafts, meteorological satellites, ground-based weather radars and so on, because of the lim- Correspondence to: H. Fujita (h-fujita@rish.kyoto-u.ac.jp) itation of the instruments. On the other hand, wind profilers are one of the most powerful instruments for typhoon ob- servations, since they can obtain profiles of wind fields with the high time and height resolutions in any weather condi- tions. Recent years in Japan, as typhoon observational tech- niques using wind profilers gradually developed, the detailed structure of typhoon came to be seen and the researches of typhoon using wind profilers were begun these days. For example, Teshiba et al. (2001) and Shibagaki et al. (2003) examined the wind fields relative to typhoon center around the Japan Islands based on wind profiler observations. They showed intence cyclonic wind in the front side of typhoon and inflow and outflow in lower and in higher height, re- spectivery. It seems that these characteristics in the vicin- ity of typhoon center are representative for the typhoon ap- proached to the Japan Islands. However, as a few number of typhoon apploaches to Japan every year and the typoon observation technique using wind profiler developed recent year, there are few instance of typhoon observation using wind profiler. Therefore, we need further researches of ty- phoon approached to Japan Islands with wind profiler. In this study, we used observation data of typhoon 0310 (Etau) with wind profilers in plural sites from 7 to 10 August 2003, and examined wind fields of typhoon accompanied to extratropical transition. We show the analysis result of wind fields especially three WINDAS sites (Shimizu, Kochi and Takamatsu, see Fig. 1) in this paper. These sites are approxi- mately located in the same distance from the closest point of approach of typhoon center and are the same azimuth angle relative to the typhoon center. Therefore, we consider that we can see not the nonaxi-symmetric structure of typhoon but the wind variation accompanied to the extratropical tran- sition by the comparison to the wind fields of the three sites. In addition to three sites, we show the result at Naze where typhoon center passed just over the radar site.