Home > Guidance > Journal of the Aerological Observatory > Vol.68
| Title | Author | |
|---|---|---|
| Foreword | in Japanese | Hiroshi Matsubara |
| Comparative Observation for Replacing the Ozone Monitor at Tsukuba Station | in Japanese | Mikako KUDO and Hirotoshi BABA |
| Intercomparison between the ECC Ozonesonde and the KC Ozonesonde from December 2007 to February 2008 | in Japanese | Masamichi NAKAMURA, Sonoki IWANO, Makoto MATSUMOTO, Hiroshi TATSUMI and Satoshi ITO |
| Temperature Trend Considering Historical Changes of Radiosonde (Part 1) | in Japanese | Itaru UESATO, Satoshi ITO, Mariko KUMAMOTO, Ryodo SHIGEBAYASHI and Masamichi NAKAMURA |
| Reparameterization of the Ozonesonde Flight Simulation Program | in Japanese | Satoshi ITO and Junken OKUYAMA |
| Transition to the World Infrared Irradiance Standard at Tateno BSRN Station | [Abstract] | Nozomu OHKAWARA and Matsumi TAKANO |
| Development of a Pump Efficiency Measurement System for Ozonesonde using the Bag Method Flowmeter | in Japanese | Tatsumi NAKANO and Sonoki IWANO |
| Introduction of Zenith Sky Cloud Detector for Umkehr Measurement in Dobson Spectrophotometer | [Abstract] | Koji MIYAGAWA and Keisuke UENO |
| New Method for Total Cloud Amount Measurement by Fish-eye Sky Camera -Cloud Discrimination using Saturation, Blueness of Sky and Atmospheric Turbidity- |
in Japanese | Matsumi TAKANO |
| He-Ne and He-Cd Laser System for Optical Alignment of Brewer Spectrophotometer | [Abstract] | Mahito ITO |
| Spectral Sensitivity Calibration System for Broadband UV Radiometer using iHR320 Spectrometer | [Abstract] | Mahito ITO and Atsuhiko SHIMOJIMA |
| Difference of Direct Sun Ozone Measurements between Brewer MKIII and Dobson Spectrophotometers in JMA Network from 2002 (2001) to 2007 | [Abstract] | Mahito ITO and Koji MIYAGAWA |
A world infrared irradiance standard was established by the World Infrared Radiometer Calibration Center (WIRCC) at the World Radiation Center (WRC) in Davos, Switzerland, in 2006 following the recommendation at the thirteenth session of the World Meteorological Organization (WMO) / Commission for Instruments and Methods of Observation (CIMO). The Aerological Observatory of the Japan Meteorological Agency (Tateno Baseline Surface Radiation Network (BSRN) station) examined the difference in longwave radiation observations by the world standard and Tateno's own standard. The observations agreed well with each other, and the maximum difference was much less than the uncertainty in the world infrared irradiance standard. Almost no dependence on the value of longwave radiation and the body temperature of the pyrgeometer was found. Based on these results, Tateno started employing the world infrared irradiance standard in January 2008 and the longwave radiation observations at Tateno are now traceable to the World Infrared Standard Group (WISG). Tateno observes shortwave and longwave radiation with global traceability and provides the data via the BSRN data archive.
The Zenith Sky Cloud Detector (ZSCD) was developed to detect clouds present in the zenith sky. The Japan Meteorological Agency (JMA) incorporated the ZSCD into the ozone observation network to achieve real-time quality control of Umkehr observation in 2007. A Dobson spectrophotometer is used as one of the instruments for accurately monitoring the ozone layer, and JMA is performing regular observations at Sapporo, Tsukuba, Naha, and Syowa in the Antarctic. The Dobson spectrophotometer monitors the ozone layers of the Earth's atmosphere. However, the accuracy of Dobson measurements depends on the presence of clouds in the Zenith Sky. ZSCDs for detecting clouds were first developed by the National Oceanic and Atmospheric Administration (NOAA) in the 1980s. ZSCDs use an 862nm (center wavelength) interference filter for the near-infrared region and can detect light scattered by the main clouds at Zenith. This optical device is composed of an interference filter, a lens, its aperture, and a high-sensitivity, near-infrared photodiode. The amplified output is input through the A/D interface of the Dobson automated system. The Umkehr observation using ZSCD modifies the influence of clouds and can help achieve a good ozone profile. JMA developed this unit based on the ZSCD used for the Global Atmosphere Watch (GAW) ozone observation network in NOAA. The effect of the clouds of measurement N-value can evaluate the clouds using the standard deviation from time series of ZSCD output.
The Aerological Observatory completed new optical alignment systems for accurate optical alignment of Brewer spectrophotometers in the Japan Meteorological Agency (JMA) network. The systems consist of a Helium-Neon (632.8nm) laser system with a beam expander, an optical bench, a laser holder and adjusters, a Helium-Cadmium (441.6/325.0nm) laser system with a lens unit, and a turntable with adjustable feet for leveling. 1) The He-Ne (632.8nm) system is useful for aligning all MKII optics from foreoptics to photomultiplier, and MKIII optics from foreoptics to the tilted lens. 2) The 441.6nm laser of the He-Cd system can align MKII and MKIII optics from foreoptics to the tilted lens. The 325.0nm laser of the same system can align all MKII and MKIII optics with high accuracy. No difference was observed in laser beam axes between 441.6nm and 325.0nm lasers when the switching shutter was operated. The 325.0nm laser is useful for measuring wavelength shift, optical resolution, and stray light. 3) The turntable can align the foreoptics and the spectrometer with their laser systems.
The Aerological Observatory developed a new spectral sensitivity calibration system for broadband UV radiometers in the Japan Meteorological Agency (JMA) network. The system consists of an NIST lamp unit, a deuterium lamp unit, fore-optics, an iHR spectrometer, and rear-optics. NIST tungsten-halogen 1000W DXW and FEL lamps or a 30W deuterium lamp can be selected as the light source. A GR600 (GR1200) grating for UV produces light at a wavelength of 150 to 3000nm (150 to 1500nm), using minimum drive step size of 0.002nm. The theoretical spectral resolution depends on the kind of grating and slit width, (e.g. the theoretical spectral resolution is 2.5nm wavelength when GR600 was used at 0.5mm in slit width).
Tests using the system clarified the following. 1) Grating tests: UVB (UVA) outputs of a broadband UV radiometer (UV-S-AB-T) using GR1200 decrease 33% (25%) compared to the output using GR600; 2) Slit width tests: UVB (UVA)outputs can be produced by slit widths from 0.5 to 2.0mm (1.0 to 2.0mm); 3) Slit height tests: Outputs were recognized only at a slit height of open (15mm); 4) Lamp irradiance tests: High UVB and UVA irradiances are produced by FEL type NIST lamps; the deuterium lamp cannot be used in the UVA output test; 5) Wavelength position accuracy test: The wavelength position shifted less than 2nm when GR1200 was used. The GR1200 scanning by the spectrometer needs "calibrate menu" must be calibrated every time before tests.
The spectral sensitivity of the UV radiometer was determined by the system as followings. Spectral irradiances of the system could be calculated every 1nm (±0.5nm) from 280 to 400nm wavelength by scanning using the Brewer MKIII Spectrophotometer. The spectral irradiances produced remarkable spectral sensitivity of UV radiometer UV-S-AB-T (peak sensitivity at a wavelength of 301.0nm for UVB scanning and 359.0nm for UVA scanning). UVB responsivity of the instrument calculated by the spectral sensitivity was consistent with the value determined by NIST lamp calibration, but UVA responsivity differed by about 15%.
In atmospheric ozone monitoring careful data quality control is essential for correct analysis and evaluation of long-term ozone trends. In this connection, the first World Meteorological Organization (WMO) summary report on the comparison of total ozone measurements of Dobson and Brewer spectrophotometers (WMO:2003) states that the simultaneous operation of Dobson and Brewer instruments at the same station is highly recommended to improve the reliability of the total ozone measurements of the station, and indicates some seasonal change in the trend of total ozone difference between Brewer and Dobson. Recently, Vanicek (2006) presented the analysis results of the relation between high-quality simultaneous Dobson, Brewer ground and satellite total ozone observations, and suggested the difference between Brewer and Dobson to be attributed to the influence of temperature on ozone absorption coefficients and total sulfur dioxide. The Japan Meteorological Agency (JMA) Brewer MKIII UV network is run concurrently with a long-term Dobson ozone network comprised of stations at Sapporo, Tsukuba, Kagoshima, Naha, and Syowa Antarctica including Minamitorishima with Brewer MKII, which has replaced the old Brewer MKII UV network that operated from January 1990 to December 2001. These overlapped networks continue to store quasi-simultaneous total ozone comparison data as well as SO2. This paper presents the ds O3 observation results and the direct sun (ds) O3 difference between Brewer and Dobson without data correction by Brewer internal lamp tests as long-term and high-quality multiple Dobson-Brewer comparisons in the same network. The observation results from 2002 (2001) to 2007 are summarized below.
1) Monthly mean of daily ds O3 differences, expressed as the ratio of (BR-DB)/DB, ranged from +1.4 to -2.3%(maximum amplitude: 3.7%) at Sapporo (43.1N/141.3E), +1.5 to -3.1% (4.6%) at Tsukuba (36.1N/140.1E), +1.8 to -2.1% (3.9%) at Kagoshima (31.6N/130.5E), +1.1 to -1.7% (2.8%) at Naha (26.2N/127.7E), and +4.5 to -5.0% (9.5%)at Syowa Antarctica (69.0S/39.6E). The seasonal variation of ds O3 difference was clear at Syowa Antarctica and Tsukuba.
2) Seven-day average of daily ds O3 differences indicated "small seasonal differences" of the maximum from November to December and the minimum in June at Sapporo, "medium seasonal differences" of the maximum in January and the minimum from June to July at Tsukuba, "medium seasonal differences" of the maximum from December to January and the minimum from May to July at Kagoshima, "no seasonal difference" at Naha, and "large seasonal differences" of the maximum from April to September and the minimum from November to December at Syowa Antarctica.
3) The relations of "ds SO2" (daily mean of ds SO2), "AVG air mass" (daily mean of air mass at observation) and "O3 STD" (daily standard deviation of ds O3) with Brewer, versus the ds O3 difference are as follows. The first dependency of ds O3 difference on "ds SO2" was found at all stations, excluding Syowa Antarctica where the level of SO2 is very low. The slope of the linear regression was about -0.003 (from -0.0015 to -0.0048). A 10m atm-cm increase of SO2 thus produces about a 3% increase of Dobson ds O3. The second dependency on "AVG air mass" was not discernible at Kagoshima and Naha but was rather clear at Sapporo (slope: +0.00007), Tsukuba (slope: +0.00014) and Syowa Antarctica (slope: +0.00025). The third dependency on "O3 STD" was observed at Naha and Syowa Antarctica, and the slope was about -0.0014 and -0.0016.
4) The daily ds O3 difference between some Brewer observations (including MKII and MKIII) and Dobson observations in the last five years at Tsukuba also indicated seasonal variations. In contrast, the ds O3 difference between Brewer MKIII and Brewer MKII, expressed as the ratio of (BR MKII-BR MKIII)/(BR MKIII), did not exhibit seasonal variations.
5) The seasonal variation of ds O3 differences between Brewer and Dobson observations was reduced to a large extent by adjusting the Brewer ETC constants for ds O3 observation, but could not be removed completely.
6) The relation of temperature in Brewer instruments with the ds O3 differences was not clear.
7) Dependency of the ds O3 difference on turbidity (τ) with pyrheliometer was found at all stations, including Syowa Antarctica where the level of turbidity is very low. The percentage of the ds O3 difference decreased to -1% as turbidity increased from τ= 3.0 to 6.0, excluding Syowa Antarctica. The seasonal variation of daily turbidity at all stations was the same as the ds O3 difference.
8) SO2 is introduced by volcanic eruption as well as air pollution at all these stations but Syowa Antarctica. It is clear that the ds O3 difference, expressed as the value of BR MKIII-DB (m atm-cm), was closely related to the increased ds SO2 (m atm-cm) during ds O3 measurements. For example, the ds O3 difference of 6m atm-cm at air mass 2.5 on 276 JD 2004 was almost the same value of the ds SO2 at the time. These examples quantitatively verify the results of 3).