Vertical Diffusion Coefficient under Stable Conditions Estimated from Variations in the Near-Surface Radon Concentration

Journal of the Meteorological Society of Japan. Ser. II

Shigeru ONOGI²  Hidekazu MATSUEDA²  Kentaro ISHIJIMA⁵  Shohei MURAYAMA³  Hiroaki KONDO³  Hirofumi SUGAWARA¹  Akira WADA⁴  Yousuke SAWA² 

[1] National Defense Academy, Yokosuka, Japan;Meteorological Research Institute, Tsukuba, Japan;National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan;Japan Meteorological Agency, Tokyo, Japan;Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan

关键词: radon concentration;    vertical diffusivity in the stable layer;    inversion layer height;    tower observation;    self-correlation;    Pasquill stability categories;   

DOI  :  10.2151/jmsj.2014-106

学科分类：大气科学

来源: Meteorological Society of Japan

【 摘 要 】

Vertical diffusion in a stable boundary layer near the surface is not clearly understood. In the present study, the vertical diffusivity of radon and the height below which the concentration of radon is high are estimated from observations made at two levels (1.5 and 100 m) on the meteorological tower in the campus of the Meteorological Research Institute, Tsukuba, Japan, in November 2006. Seven 12-hour episodes, in which radon concentration near the surface increased, were averaged to make one sequential dataset. The averaged time sequence was divided into two periods: the radon concentration near the surface increased in the first one (Period I) and was stationary in the second (Period II). The estimated vertical diffusivity was less than 0.05 m2 s-1 for Period I and was at most 0.13 m2 s-1 for Period II. The estimated thickness of the radon-rich layer was less than 50 m for the first three hours in the first period; however, inversion height was approximately 100 m. The height under which radon accumulated was somewhat lower than that at the temperature inversion in period I, which suggests that the turbulent transfer was not dominant in the process to generate the temperature inversion layer in this area. Although the vertical diffusion of radon was different between the two periods, it was difficult to distinguish them with surface observation, employed for conventional Pasquill stability categories classification.

【 授权许可】

Unknown