Home > Guidance > Journal of the Aerological Observatory > Vol.72
Aerological Observatory of JMA started "Observations of Total Ozone and UV Solar Radiation with Brewer Spectrophotometer on the Norikura Mountains" as a joint project with Institute for Cosmic Ray Research (ICRR), University of Tokyo at the Norikura Observatory of ICRR (Brewer site: 36.11 N, 137.56 E, 2,772 m a.s.l.), locating at the Northern Japanese Alps, every summer seasons since 2009 (Ito et al.:2011, 2012). Purpose of this study is absolute calibration for Brewers based on the concept of developing Regional Brewer Calibration Centre for Asia, and study of total ozone and UV radiation (GLUV: global UV, DFUV: diffuse UV) by using Brewers (BR#174, BR#113 and BR#060) on the high mountains. In this paper, their absolute calibration results and observation results for five years from 2009 to 2013 are summarized below.
(1) By the absolute calibrations of Brewers for total O3 observations, "O3 Extra-Terrestrial Coefficients (=ETC)" of BR#174 and BR#113 could be produced as about 10 samples every year. The representative coefficients every year were stable and identical within 1% to the currently used coefficients for five years. (2) The variation of 5-years mean of total O3 at Norikura in the summer season showed the low value of about -4% compared to the value at Tsukuba (36.06 N, 140.13 E, 39 m a.s.l.) at almost same latitude. However the difference became smaller in late September. (3) The 5-years mean of daily total GLUV (CIE) at Norikura for the season indicated the value of +3%compared to the value at Tsukuba, but the value in clear day did the high value of +40%. (4) The 5-years mean of daily UV (CIE) diffusibility, RDFUV (=DFUV/GLUV), at Norikura in clear day indicated the very lower value of about 0.54 (54%) compared to the value of about 0.72 at Tsukuba, respectively. (5) The UV spectral irradiance of GLUV increased in the short wavelength range at Norikura compared to the value at Tsukuba, and showed as follows; e.g. about +29% at the wavelength of 325nm and about +60% at 300nm in clear day, respectively. (6) The altitudinal increasing rate of GLUV (CIE) in the clear day indicated the calculated amounts of about +14.6% per 1,000 m.
These calibrations and observations for five years elucidated the availability of absolute calibration for Brewers at Norikura, and many characteristic of O3 and UV radiation on the high mountains. The continuous observations with Brewers and other instrument are very important for the clarification of the seasonal variation and the coefficient trends.