Home > Guidance > Journal of the Aerological Observatory > Vol.65
| Title | Author | |
|---|---|---|
| Foreword | in Japanese | Michio Hirota |
| (Frontispiece) The Historical Wind Aloft Chart at TATENO | in Japanese | Toyoo Abe |
| Trend of Upper Air Temperature over Japan - Analysis of 5 Weather Stations, Sapporo, Tateno, Kagoshima, Naha and Minamitorishima - | in Japanese | Koichi NAKASHIMA |
| Investigation Concerning Collected Fall Sondes | in Japanese | Mariko KUMAMOTO, Masashi SATO, Masami HINOHARA and Tetsuji KANEKO |
| Use of the Prediction Information System of Radiosonde Flight | in Japanese | Shohei IWATSUBO |
| Diffuse Spectral UVB Observation using Brewer Spectrophotometer and Simple Shadow Unit | [Abstract] | Mahito ITO |
| Reflected Spectral UVB Routine Observation on the Ground Surface using Modified Brewer Spectrophotometer at Tsukuba in 2004 | [Abstract] | Mahito ITO |
| Responsivity Trends of Broadband UV Radiometers by NIST Lamp Calibration and Difficulty of Observation | [Abstract] | Mahito ITO |
| On the Net-Radiometer CNR1 (Part III) - Influence of Heater for Dew Condensation Prevention and Experimental Production of Solar Radiation Cover Device - | in Japanese | Katsue NAGAI and Hiroshi NAGANUMA |
| On the Characteristics of CG4 Pyrgeometer (Part I) | in Japanese | Hiroshi NAGANUMA and Katsue NAGAI |
| Development of the Cloud Screening Algorithm in Sunphotometer Observation | in Japanese | Osamu IJIMA |
| WMO/GAW Intercomparison of Dobson Ozone Spectrophotometers in Boulder, USA | [Abstract] | Koji MIYAGAWA |
| WMO/GAW Regional Dobson Spectrophotometer QA/SAC for Manila, Philippines | [Abstract] | Koji MIYAGAWA and Hannagrace F. Cristi |
| Intercomparison of Dobson Ozone Spectrophotometer in Yonsei University, Korea | [Abstract] | Koji MIYAGAWA, Jhoon Kim and Hi Ku Cho |
A Brewer spectrophotometer with simple shadow unit for observing diffuse spectral UVB was developed at the Aerological Observatory, Tsukuba. This paper presents the results of diffuse spectral UVB measurements carried out from June (summer) to December (winter) in 2004. They are summarized as follows; 1) Simple shadow unit comprised of free frame and a black ball was mounted on Brewer spectrophotometer MKII #058. Shadow effect of the free frame was confirmed to be negligible comparing with Brewer #052 on a clear day. By comparing with Brewer #052 (replaced by #113 on a temporary basis) the responsivity of unshadowed Brewer #058 was monitored during the measurements. They agreed within 1 percent under selected clear and fine sky conditions. The daily responsivity trend of Brewer #058 was also traced in the same way as routine UV observation. 2) Shadowed Brewer #058 and unshadowed #052 (#113) were run by time-controlled scan uz.rtn which is a special routine for instrument intercomparison. UVB diffuse ratios (diffuse/global) were calculated for a total of twenty clear and fine days. The diffuse ratio showed a daily pattern of shallow sinusoidal concave with the minimum value at noon. During the daytime from 9.5 to 14.5 JST (Japan Standard Time) the mean ratio was about 0.81 (0.77 for clear, 0.87 for the rest)and the minimum 0.77 (0.74 for clear, 0.88 for the rest) in contrast with the deep flat pan pattern of solar diffuse ratio the mean value of which was about 0.19 for clear days. As a whole the UVB diffuse ratio was 3.5 to 4 times larger than the solar diffuse ratio around noon. Linear wavelength-dependence of the spectral UVB diffuse ratio was recognized and the gradient was about -0.3 %/nm. The UVB diffuse ratio decreased toward winter but the tendency was weaker than the solar diffuse ratio. 3) Relations between UVB diffuse ratio and some atmospheric conditions were examined. Due to remarkable difference of the daily pattern, the solar diffuse ratio related to the UVB diffuse ratio roughly as 0.1 versus 0.6 (0.5 for summer, 0.7 for late autumn to winter), 0.4 versus 0.98 (0.96 for summer, nearly 1.0 for late autumn to winter), and 0.5 versus the saturated value of 1.0, respectively. Atmospheric turbidity, visibility and cloud amount affected the UVB and solar diffuse ratios in a similar way but the steepness of the correlation curves were fairly different.
A modified Brewer spectrophotometer, together with the calibration method, was developed at the Aerological Observatory in Tsukuba to observe reflected UVB radiation on the ground surface (Ito:2004). Using the Brewer system reflected spectral UVB measurement of the grass field was made from December 2003 to January 2005 to characterize the seasonal variation. The measurement was carried out in parallel with the routine global UVB observation on the rooftop. The results excluding snowfall days are summarized as follows; 1) Monthly reflected UVB had the maximum in April (July for global UVB) and minimum in December (December for global UVB). The monthly maximum UVB reflectivity of 0.020 was observed in March and the minimum of 0.012 in October. Annual mean of the monthly UVB reflectivity was 0.016 comparing with 0.183 for solar radiation. 2) As for the case of daily total of the reflected UVB, the maximum of the upper limit envelope appeared at around 100 JD (early April)and the minimum at around 355 JD (late December) whereas the maximum of global UVB was found at around 180 JD (late June) and the minimum at around 360 JD (late December). In the same way, the maximum daily UVB reflectivity of 0.024 was found at around 95 JD (early April). The minimum daily UVB reflectivity of 0.012 to 0.014 appeared in summer through autumn, which was disturbed by intermittent field mowing. The variation of the UVB reflectivity in this period seemed to represent the “absorbing effect of UVB by vegetation”. 3) Spectral UVB reflectivity of dried grass surface indicated linear wavelength-dependence of higher reflectivity at longer wavelength, but no significant wavelength-dependence for green grass cover. 4) Seasonal change of UVB reflectivity was similar to the solar reflectivity in winter to spring seasons. On the other hand, they differed in summer to autumn due to strong absorption of UVB by vegetation.
Aging characteristics of seventeen broadband UV radiometers, namely nine of Kipp & Zonen (UV-S-AB-T), one Sin-Tec (UV-S-AB-T) and seven of Eko (MS210, MS212WF, MS212W) were analyzed on the basis of NIST lamp calibration results. They showed a variety of responsivity trends. Some of them indicated high stability or monotonous degradation with exposure time, while another gained higher responsivity by insolation. In the latter case the responsivity seemed to reach saturated value in a few months or years depending on the instrument. For many of the instruments the rate of responsivity change was 5 to 10 percent per year and the maximum was over 40 percent. Two instruments of the same manufacturer, one of which was exposed continuously and the other kept indoors, seemed to show a similar responsivity degradation of about 90 percent during fourteen years, which suggests a certain degrading factor other than insolation. The broadband radiometers calibrated by NIST lamp were compared with Brewer spectrophotometer by measuring the solar UVB irradiance. The irradiance ratios to Brewer scattered in the range of 0.8 to 1.2 for five of the same type with an exception of 2.0. Two of another type indicated a senseless ratio of 22. The cause of such large discrepancy remains unresolved.
The WMO/GAW intercomparison of Dobson ozone spectrophotometer was held from 7 to 30 September 2004 at the National Oceanic and Atmospheric Administration (NOAA) in Boulder, USA. During the intercomparison, the Asian standard Dobson No.116 was compared with the world standard Dobson No.83 in collaboration with the ozone group at the Climate Monitoring and Diagnostics Laboratory (CMDL) of NOAA where the world Dobson standard is maintained. The purpose of this event was to calibrate total ozone measurement as well as the improvement of umkehr measurement for vertical ozone profile. The first comparison measurements of total ozone were carried out in the morning hours on 9 September. The error of No.116 was 0.0 percent when referred to the total ozone of 300 m atm-cm, which proved no substantial calibration shifting occurred from the old factor determined three years before at Mauna Loa in Hawaii. The internal optics of No.116 was generally in good condition though a dirt spot was found on a mirror. The right-side mirror was replaced with a German quartz-coated mirror provided by CMDL. After the mirror replacement optical adjustment and instrument maintenance of No.116 were performed. The final comparison of total ozone was carried out on 17 September and the new calibration factor of No.116 was determined. Umkehr comparison measurements for evaluating the characteristics of vertical ozone profile by Dobson spectrophotometer were tried several times during the period, and two sets of ozone vertical profiles were obtained. ECC ozonesonde was also launched twice on 15 September when one of the umkehr measurements was successfully completed. The comparison result of umkehr and ECC ozonesonde measurements will be utilized as a reference for evaluating the Dobson umkehr measurement. The Asian standard Dobson No.116 was upgraded to the new automatic Dobson system of Windows version in 2001. During this intercomparison all the measurements and lamp tests were processed in fully automatic mode using the Windows comparison programs of the new system.
The World Meteorological Organization Global Atmospheric Watch (WMO/GAW) has assigned the Japan Meteorological Agency (JMA) to be the Quality Assurance/Science Activity Center (QA/SAC) for Asia and southwest Pacific region (Region II/V). The Aerological Observatory of JMA in Tsukuba is responsible for the calibration of all the Dobson spectrophotometers in the region in order to come up with quality assured and globally standard total ozone data. One of the activities of the JMA QA/SAC is the field survey. An expert from JMA QA/SAC made the first field survey in the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), Philippines in March 22-31, 2004 to evaluate, repair and calibrate the Dobson Spectrophotometer (No.52). Before the arrival of the expert, Dobson No.52 stopped its operation in preparation for the site transfer. Meanwhile during the instrument check-up some parts are found to be defective and replacement was performed. The observers were briefed with the observation method and proper instrument maintenance. The computer software with training was provided for the total ozone data management. The instrument is now operational in the new site but there is still an urgent need for intercomparison with the standard Dobson No.116.
At Yonsei University in Korea, the ozone observation using Dobson ozone spectrophotometer is the 20th year since the commencement in 1984. The international ozone workshop (Joint International Workshop on Ozone and ILAS-II Science Team Meeting), which commemorated the 20th anniversary of ozone observation in Korea, was held at Yonsei University in November 2004. Associating with the workshop, Yonsei University performed the instrument calibration of Dobson No.124 for maintaining the measurement accuracy of ozone observation. The intercomparison of Dobson in Seoul was the first trial performed by shipping the traveling reference Dobson calibrated by the Asian regional standard No.116 in Japan. The Dobson No.124 is maintained at Global Environment Laboratory, Yonsei University and the result of ozone observation is reported to the World Ozone and Ultraviolet Radiation Data Centre (WOUDC). In the Dobson intercomparison at Yonsei University, comparison measurements, instrument maintenance, in-depth lamp tests, and the technical study were carried out during the two weeks. Finally, the Dobson No.124 was adjusted to an accuracy of less than 1 percent in total ozone comparing with the traveling reference. As in this case in Korea, on-site Dobson calibration by traveling reference instrument and the expert avoids possible characteristic shift of the comparison instrument due to transportation. Additional merits are the best-suited technical advice offered through the survey on the site environment, personnel, operation practice and data handling, as well as the information sharing of the latest technology among the participants. The practical discussion and strategy in accordance with the needs of the site is the key to successful station updating.