Temporal Evolution and Spatial Structure of the Local Easterly Wind "Kiyokawa-Dashi" in Japan PART I: Coherent Doppler Lidar Observations

Abstract

The Kiyokawa-dashi (strong local wind) was observed with a coherent Doppler lidar at the exit of the Mogami Valley, in Kiyokawa (38.80 N, 140.01 E, 20 m MSL) . When the Kiyokawa-dashi blew, the synoptic patterns tended to be high-pressure in the east and low-pressure in the west. After the Kiyokawa-dashi was extracted, the data measured by the coherent Doppler lidar with a high spatial and temporal resolution were then utilized to investigate it. On the basis of the range height indicator and Plane position indicator scans, the coherent Doppler lidar was able to detect the three-dimensional dynamical structure of the Kiyokawa-dashi up to 8-10 km downstream from the Kiyokawa observation site. The coherent Doppler lidar clearly showed that a low-level critical layer (horizontal wind speed A 0 m s À1 ) existed at altitudes of 0.5-1.2 km, and that a strong easterly/southeasterly wind confined below the critical layer blows away about 10-km downstream of the Mogami Valley. Intensive upward/downward vertical motion under the critical layer was indicated by the velocity-azimuth display scan. The line-of-sight wind speeds obtained by high-frequency plane position indicator scans were high, not only near the exit of the Mogami Valley but also over the entire Shonai plain, and the distributions of the line-of-sight wind speeds were almost steady, indicating the existence of transient disturbances.

Effects of Solar Radiation Amount and Synoptic-scale Wind on the Local Wind "Karakkaze" over the Kanto Plain in Japan

“…Introduction (Arakawa 1971, Yoshino 1986) such as the "YamajiKaze" (Furukawa 1966, Saito andIkawa 1991, Saito Japan is mountainous (Fig. 1), and thus produces a 1994), "Hirodo-Kaze" (Nakamura et al 2002, Fudeyasu variety of thermally anddynamically driven local winds et al 2008), "Kiyokawa-Dashi" (Takeuchi 1986, Yamagishi and Kato 1996, Ishii et al 2007 tern (Yoshino 1986) (Fig. 2).…”

The Temporal Evolution and Spatial Structure of the Local Easterly Wind “Kiyokawa-dashi” in Japan PART II: Numerical Simulations

“…4b). The value of this pressure di¤erence is much more than is generally associated with Kiyokawa-dashi (Ishii et al 2007), and/or the hybrid mountain/gap flow (Colle and Mass 1998a;Liu et al 2000;Flamant et al 2002), or sea-level gap flow (Colle and Mass 2000). Therefore, the case in this paper would be produced by the strong pressure gradient field.…”

“…In the present study, the three-dimensional structure and dynamics of Kiyokawa-dashi for the case discussed in Part I observed on August 30, 2004 (Ishii et al 2007) were examined using highresolution numerical simulations by NHM. Several sensitivity experiments, for example on the horizontal resolution, vertical structure, and surface roughness, were conducted for comparison and verification with respect to the CDL observation.…”

The Formation of Sharp Multi-Layered Wind Structure over Tokyo Associated with Sea-breeze Circulation

“…A ground-based coherent Doppler lidar system developed at the National Institute of Information and Communications Technology (NICT-CDL; Ishii et al 2007) was used in this study. At NICT-CDL, a transceiver system that was manufactured by Coherent Technologies, Inc., a two-axis mirror scanning system, and a data acquisition system were equipped.…”