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

Abstract

A climatological and numerical study of "Karakkaze," a type of local wind in Japan, was conducted. First, winter days under a winter-type synoptic pressure pattern with daily minimum relative humidity of less than 40% were classified according to strong wind (wind speed � 9 ms −1 , Karakkaze day), medium wind (6 ms −1 � wind speed < 9 ms −1 ), and weak wind (wind speed < 6 ms −1 ). Secondly, the spatial patterns of the surface wind in each category are confirmed by the Japan Meteorological Agency (JMA)-Automated Meteorological Data Acquisition System (AMeDAS) observation data. In addition, we compared the boundary-layer wind of the three categories using wind speed data from the observation tower of the Meteorological Research Institute (MRI) in Tsukuba and from the JMA wind profiler in Kumagaya. Finally, we performed one-dimensional numerical experiments using a column Planetary Boundary Layer (PBL) model to evaluate the impact of solar radiation and upper-level wind on the formation of the Karakkaze.The results are summarized as follows. On the strong-wind days, strong northwesterly winds appear in the area along the Arakawa River and the Tonegawa River from Maebashi. The surface wind speed has a clear diurnal variation with a peak in the early afternoon. Such a diurnal variation is observed up to a 200 m level, but this diurnal pattern nearly reverses itself between 200 m and 400 m levels. On weak-wind days, the diurnal variation pattern is similar to that in other two categories, but the reversed pattern appears at a 100 m level, not at a 200 m level.Stronger surface winds appear under a clearer winter-type pressure pattern. The correlation coefficient is 0.632 between the daily maximum surface wind speed and the daily mean wind speed at a height of 2759 m, whereas the correlation is 0.284 between the surface wind speed and daily sunshine duration, which, in a previous study, was suggested to be the most significant factor.Numerical experiments indicate that a large amount of solar radiation is a necessary condition for a strong daytime wind, but this is not a sufficient explanation for the difference in the surface wind speed between weak and strong-wind days.

A Climatological Study of the Local “Karakkaze” Wind, with a Focus on Temperature Change

“…1b) from 2000 to 2016. The present study specifically defined the formation of Karakkaze based on the following four criteria derived from previous studies (e.g., Yoshino 1975;Kusaka et al 2011): (1) wind speed at a height of 10 m at Maebashi must be more than 8 m s −1 , (2) the most frequent wind direction at 10 m at Maebashi must be between 270° and 360° while a strong wind is blowing, (3) relative humidity at 2 m at Maebashi must be < 40% when the most strong wind blows on the event, and (4) there must be no precipitation at Maebashi while the strong wind is blowing. We defined a Karakkaze event as a period that satisfied the above criteria and during which the wind speed was 4 m s −1 or more.…”

“…The islands are thus in an environment that favors the development of strong winds caused by terrain, and many local winds occur in Japan (Yoshino 1975;Kusaka and Fudeyasu 2017). Well-known examples of such local winds include the Karakkaze (Yoshino 1975(Yoshino , 1978Kusaka et al 2011), Matsubori-kaze (Yoshino 1975;Kurose et al 2002), Hirodo-kaze (Yoshino 1975;Fudeyasu et al 2008), Yamaji-kaze (Saito and Ikawa 1991;Saito 1993), and Kiyokawadashi (Yoshino 1975;Ishii et al 2007;Sasaki et al 2010).…”

“…Recent studies, however, have found diurnal cycles of the wind and temperatures on Karakkaze days (e.g., Yamagishi 2002;Yomogida and Rikiishi 2004;Kusaka et al 2011). In particular, wind speed and air temperature generally increase in the morning and decrease at night.…”

Spatio-Temporal Variation of High-Temperature Events in Hokkaido, North Japan

“…6b). The mechanical effect of strong winds, which occasionally breaks the surface inversion layer, is an additional factor in night-time high-temperature events (White 2009;Kusaka et al 2011). In the case of January 13, 2000, however, the wind speed was not strong at Saroma (Fig.…”

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

“…Kondo (1983) called these increased daytime wind speeds thermal convective winds. Kusaka et al (2011) also reported that strong local surface winds on the Kanto Plain during winter, so-called Karakkaze, have a clear diurnal variation and show a strong correlation with the upper-level wind speed but a weak correlation with the daily sunshine duration. The wind speed near the top of the PBL is relatively weak in the daytime, but it is strengthened at night because the development of a stable atmosphere decouples low-level winds, and general winds flow over the PBL (Blackadar 1957).…”