32nd Conference on Broadcast Meteorology/31st Conference on Radar Meteorology/Fifth Conference on Coastal Atmospheric and Oceanic Prediction and Processes

Wednesday, 6 August 2003
Ka-band radar observations of orographic snow clouds and flows across a steep mountain ridge
Kenichi Kusunoki, MRI, Tsukuba, Japan; and M. Murakami, N. Orikasa, Y. Tanaka, K. Iwanami, M. Maki, P. SangGoon, R. Misumi, K. Hamazu, and H. Kosuge
Poster PDF (563.7 kB)
This paper documents the flow and precipitation around the Mikuni Mountains, Japan, for a case of winter monsoon (relatively steady northwesterly flow). This study utilized data from "The Joint Project of the orographic Snow Cloud Modification", which was designed to observe orographic snow clouds and identify seeding opportunities over the Mikuni Mountains. In this study, the data from two Ka-band Doppler radars provided unique datasets. These high-resolution radars were deployed on the windward and leeward slopes, respectively, and composites were constructed from RHI/PPI scans oriented toward each other. The results are as follows.

1) Relatively laminar flows on the windward side became turbulent when the flows past the mountain ridge.

2) Precipitation enhancement in the radar reflectivity was observed on the windward slope and the turbulence area adjacent to the ridge on the leeward slope.

3) An acceleration of the horizontal wind speed and a hydraulic jump-like feature associated on the lee side were shown.

4) PPI scans from the lee- side radar revealed the presence of an unsteady separated wake in which vortex shedding occurred.

5) The behavior of echo cells was qualitatively consistent with the upstream Froude number (Fr) effect: When Fr was relatively large, echo pattern suggests that the air parcel flow almost directly across the mountain ridge, while cells flow around the summit in the case when Fr was small.

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