Moving Cellular Structure of Fog Echoes Obtained with a Millimeter-Wave Scanning Doppler Radar at Kushiro, Japan

Abstract

Observations of fogs with a millimeter-wave scanning Doppler radar were conducted at Kushiro in Hokkaido, Japan, in the summer seasons of 1999 and 2000. Three typical types of plan position indicator (PPI) displays were observed: cellular echoes with high radar reflectivity factors (∼−10 dBZ), uniformly distributed echoes with high reflectivities (∼−10 dBZ), and uniformly distributed echoes with low reflectivities (∼−30 dBZ). The authors focused on advection fog with cellular echoes observed on 5 August 1999 and 31 July 2000. Echoes showed structures of cells with a reflectivity of −10 dBZ and with intervals of about 1 km. This echo pattern moved northward (i.e., from the sea to the land). There was a vertical shear of the horizontal wind at a height around 200 m in both cases, and structures of each cell were upright above the shear line and were leaning below it. The direction and the speed of the echo pattern in both PPI and range–height indicator (RHI) displays agreed well with that of the horizontal wind at heights above the shear (200 m). In the echo cells, existence of drizzle drops is implied.

Effects of Synoptic-Scale Control on Long-Term Declining Trends of Summer Fog Frequency over the Pacific Side of Hokkaido Island

“…The altitude of each observatory is lower than 45 m above mean sea level, indicating that the observatories are situated in a typical fog-layer thickness of several hundred meters, as reported in earlier observations (Yanagisawa et al 1986;Uematsu et al 2005). Further information for each observatory is summarized in Table 1.…”

“…7a), the temperature decreased with height and relative humidity was higher than 90%, which indicates fog occurrence in the shallow moist mixing layer. The mean height of the moist mixing layer was slightly shallower than that shown in the case studies in which the fog layer reached several hundred meters above sea level (Yanagisawa et al 1986;Uematsu et al 2005). Above the mixing layer, a temperature inversion was present up to approximately 400 m above sea level.…”

“…example, a sea-fog layer developed that was up to several hundred meters high (Yanagisawa et al 1986;Uematsu et al 2005) and was capped at the top by a strong inversion layer (Haraoka et al 1995). The atmospheric vertical structure during NFDs has not yet been adequately understood, however.…”

The Fog Remote Sensing and Modeling Field Project

“…2003; Uematsu et al 2005). Because of a large variability in fog particle spectra as in the present study, the relationship between the radar reflectivity and the cloud microphysical parameters needs to be researched.…”

Fog observations with a millimeter-wave scanning radar at Miyoshi basin, Japan

“…They examined the relationship between the echo intensity and other meteorological parameters, such as the distribution of fog particles and the visibility at some observation sites. Our group has also observed sea fogs with mmwave radars at Kushiro in the summer season of 1999-2002, and found the wave-like structure of fog echoes (Uematsu et al, 2004).…”