LOCAL EASTERLY WIND “KIYOKAWA-DASHI” OBSERVED BY COHERENT DOPPLER LIDAR IN JAPAN DURING THE SUMMER 2004 Shoken Ishii (1) , Kaori Sasaki (2) , Kohei Mizutani (1) , Tetsuo Aoki (1) , Hiromitsu Kanno (2) , Dai Matsushima (3)(4) , Weiming Sha (3) , Akira Noda (3) , Masahiro Sawada (3) , Masashi Ujiie (3) , Yousuke Matsuura (3) , Toshiki Iwasaki (3) (1) National Institute of Information and Communications Technology, 4-2-1 Nukuikita-machi Koganei-shi Tokyo 184-8795 Japan, sishii@nict.go.jp (2) National Agricultural Research Center for the Tohoku Region, 4 Akahira Shimo-kuriyagawa Morioka-shi Iwate 020-0198 Japan, kaoris@affrc.go.jp (3) Graduate School of Science, Tohoku University, 6-3, Aoba, Aramaki, Aoba, Sendai, Miyagi, 980-8578, Japan, sha@wind.geophys.tohoku.ac.jp (4) Chiba Institude of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan, matsushima.dai@it-chiba.ac.jp ABSTRACT The two-axis scanning coherent Doppler lidar and 4 weather stations were used to examine the three-dimensional structure and dynamics of the Kiyokawa-dashi. The line-of-sight (LOS) wind speed distributions were measured by the 2 m eye-safe two-axis scanning coherent Doppler lidar with three scan modes, the range height indicator, the plan position indicator, and the velocity-azimuth display. The range height indicator showed fine structures that the Kiyokawa-dashi existed below the critical level (horizontal wind velocity = 0 m/sec) at an altitude of about 600 m, and that the depth of the Kiyokawa-dashi was very shallow. Although the plan position indicator suggested that the Kiyokawa-dash was almost stationary, the indicator showed that the Kiyokawa-dash had small fluctuations within a short time. The LOS wind speed distributions obtained by the coherent Doppler lidar measurements were used to compare with the wind speed distributions simulated by using a non-hydrostatic mesoscale numerical model with a horizontal grid spacing of 1 km. Although there was small bias between them, the LOS wind speed distributions were consistent approximately the simulated wind distributions. 1. INTRODUCTION In this study, the temporal evolution and spatial structure of the local easterly wind “Kiyokawa-dashi” in Japan is investigated by the observational data obtained with the 2 m eye-safe two-axis scanning coherent Doppler lidar (CDL), and four weather stations. The Kiyokawa- dashi is one of the most well-known local winds which occur over the Shonai plain in Yamagata. The characteristics of the Kiyokawa-dashi are low temperature and low humidity, and continuing duration of one day to about 1 week. The occurrence of the Kiyokawa-dashi results in the white head of rice plant and the rice blast, and causes severe crop damage. Many studies address various evolution mechanics of the Kiyokawa-dashi, such as acceleration of down- stream flow [1], gap wind [2], and deformation of atmospheric airflow passing over Gassan and Asahi (38.15 N, 139.55 E) ranges [3]. Since, however, only minimal data from ground-based meteorological studies and from short-term pilot balloon observations has been available [4], spatial information about of the Kiyokawa-dashi has been limited. Thus observational analyses of the atmospheric flow are significant for a better understanding of the evolution of the Kiyokawa-dashi. The main objectives of this study are to investigate wind profiles of the Kiyokawa-dashi to contribute to the investigation of the Kiyokawa-dashi and to improve the computational algorithm to obtain vertical and horizontal wind profile. For the objectives, we observed wind speed distributions of the Kiyokawa-dashi, and compared with those simulated by the numerical prediction division unified nonhydrostatic model of the Meteorological Research Institute.