Diurnal Variations in Lower-Tropospheric Wind over Japan Part I: Observational Results using the Wind Profiler Network and Data Acquisition System (WINDAS)

Abstract

This study investigates diurnal variations in lower-tropospheric wind over Japan during [2002][2003][2004][2005][2006][2007][2008] using data from 31 stations of the Wind profiler Network and Data Acquisition System (WINDAS) and the Automated Meteorological Data Acquisition System (AMeDAS). The diurnal and semidiurnal components are extracted and analyzed to identify the dominant processes for each height range and for each season. Near the surface, the diurnal component is controlled by local wind systems (e.g., land-sea breezes) throughout the year. At 1-3 km, the diurnal component is primarily controlled by the return currents of local wind systems, with additional influence by other disturbances; the superposition of these two wind systems generates amplitude maxima in spring (@0.5 m s À1 ) and autumn (@0.6 m s À1 ). At 3-5 km, the diurnal wind in DJF-MAM is controlled by mediumscale eastward traveling waves, which generate the amplitude maximum (@0.8 m s À1 ) in winter-spring. In JJA-SON, the diurnal component is controlled by a large-scale wind system with an amplitude of @ 0.3 m s À1 , probably related to the diurnal tide. At stations located on small islands located south of the Japanese mainland, the diurnal wind within the lower troposphere has di¤erent characteristics from those described above throughout the year. Throughout Japan, the semidiurnal wind component is controlled by the semidiurnal migrating tide above @ 1 km, and is influenced by local wind systems below @1 km. The amplitude of the semidiurnal tide below 5 km is largest in DJF (@0.4 m s À1 ) and smallest in JJA (@0.2 m s À1 ).

Diurnal variations of upper tropospheric and lower stratospheric winds over Japan as revealed with middle and upper atmosphere radar (34.85°N, 136.10°E) and five reanalysis data sets

“…Thus, a comprehensive understanding of diurnal variations in the tropopause and the stratosphere is important. However, as noted by Sakazaki and Fujiwara [2010a, 2010b] (hereafter referred to as SF10a and SF10b, respectively), there are relatively few previous studies on diurnal variations particularly below ∼20 km in the midlatitudes; these studies are briefly summarized in the following paragraphs. This lack of reports is mainly because only a few subdiurnal upper air measurements have been conducted in the troposphere and the lower stratosphere.…”

“…Two studies, SF10a and SF10b, recently investigated diurnal wind variations in the lower troposphere (below ∼5 km) over Japan, predominantly using data from 31 stations of the wind profiler network in Japan (WINDAS) and from five analysis/reanalysis data sets. The authors found that the diurnal wind component was caused by at least four (not two) different phenomena: (1) local wind systems, (2) diurnal eastward moving eddies, which propagate eastward with a horizontal wavelength of ∼1500 km and a zonal phase speed of 10 to 15 m s −1 , (3) medium‐scale waves, and (4) atmospheric tides.…”

“…As for the diurnal eastward moving eddies (2 above), SF10b suggested that they were probably excited at mountainous regions and interpreted as the edge waves trapped at the lower boundary in the baroclinic atmosphere [ Eady , 1949]. With regard to the semidiurnal wind component, SF10a confirmed the importance of the migrating tide above ∼1 km. Below ∼1 km, the semidiurnal wind component encompassed local wind systems and was examined by Sakazaki and Fujiwara [2008].…”

Diurnal Variations in Lower-Tropospheric Wind over Japan Part II: Analysis of Japan Meteorological Agency Mesoscale Analysis Data and Four Global Reanalysis Data Sets

“…In a companion paper, Sakazaki and Fujiwara (2010; hereafter referred to as SF10) investigated diurnal variations in lower tropospheric wind over Japan, using a 6-year data set obtained by the Wind profiler Network and Data Acquisition System (WINDAS) in Japan. The authors examined the characteristics of diurnal and semidiurnal components of zonal wind (u) and meridional wind (v) for each height range and for each season.…”

Diurnal Variations of Surface Wind Speed Observed in the Mountainous Area of Central Japan during Sunny Summer Days

“…Therefore, previous surface wind analyses in central Japan using AMeDAS data (e.g., Suzuki and Kawamura 1987) mostly reflect the land-sea and mountain-valley circulations along the valleys. Recently, the JMA wind profiler network has detected diurnal wind components in the lower troposphere, and the contribution of return currents of the local wind system was investigated at the 1-to 3-km level (Sakazaki and Fujiwara 2010). To assess the influence of global warming on environmental changes in the Japanese Alps region, an inter-university cooperative project (JALPS) was established in 2010 at the University of Tsukuba, Shinsyu University, and Gifu University.…”