total ozone monitoring by groundbased instruments as part of gaw
DESCRIPTION
TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW. J. Staehelin 1 , R.Stübi 2 , U. Köhler 3 and A Redondas 4 1 Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology Zürich, Switzerland - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/1.jpg)
TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS
AS PART OF GAW J. Staehelin 1, R.Stübi 2, U. Köhler 3
and A Redondas 4
1 Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology Zürich, Switzerland
2 Federal Office of Meteorology and Climatology, MeteoSwiss, CH-1530 Payerne, Switzerland
3 Meteorological Observatory Hohenpeissenberg, Regional Dobson Calibration Centre RA VI, Albin-Schwaiger-Weg 10, D-82383
Hohenpeissenberg, Germany 4 Regional Brewer Calibration Center – Europe, Izaña Atmospheric Research
Center, AEMET- Meteorological State Agency, Spain, C/ La Marina 20, 6 Planta, 38071 Santa Cruz de Tenerife Spain
![Page 2: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/2.jpg)
1. Introduction
CIMO guideChapter 17
![Page 3: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/3.jpg)
Challenge:Total ozone series of Arosa
long-term changes: small
![Page 4: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/4.jpg)
Outline
2. Instruments and method3. Dobson network4. Brewer network5. Experience with networks6. Future7. Conclusions
![Page 5: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/5.jpg)
2. Instruments and methodoperated by MeteoSwiss at Arosa:
2 Dobson instruments 3 Brewer instruments (2 single and 1 double Brewer)
Dobson instrumentEarlier version: 1920th
method presently used: IGY: 1958
Brewer spectrophotometer commerc. available: middle of 1980th
completely automated, SO2 column, UV-B
![Page 6: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/6.jpg)
Basic measurement principle (most precise measurements: direct sun)
Sun photometry, wavelength region: 305-340 nm
I (λ) = Io(λ) exp (-α(λ) X μ - β (λ) (ps/po) mR - δ (λ) ma)
X: total ozone amount (in Dobson units (DU)I (λ): solar irradiance at the wavelength λ measured at the Earth’s surface
Io (λ): intensity outside the Earth’s atmosphere
α(λ) is the monochromatic ozone absorption coefficient μ: relative slant path through ozone (air mass factor)
β(λ): Rayleigh scattering coefficientps: station pressure; po: mean sea level pressure at 1013.25 hPa;
mR: relative optical air mass corresp. to Rayleigh scattering (extinction)
δ(λ): aerosol optical depth ma: relative optical air mass corresp. to aerosol scattering (extinction)
![Page 7: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/7.jpg)
Wavelengths used in Dobson (wavelength pairs (AD)) and Brewer instruments
(other Russian filter instruments and SAOZ (absorption in visible)
![Page 8: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/8.jpg)
Calibration of instruments Io (λ): intensity outside the Earth’s atmosphere
• Extrapolation for = 0)Langley plot method
• Requirement: clean atmosphere and stable ozone for one half day
• Difficult to ensure in extratropics• Langley plot calibration for standard
instruments in Mauna Loa observatory (Hawaii)
![Page 9: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/9.jpg)
3. Dobson network
Calibration of station instruments: Dobson intercomparisons (every 4 years) (Ulf Köhler): Responsibility of Regional Calibration Centers
Central CalibrationLaboratory: NOAA, Boulder, USA(R. Evans)
![Page 10: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/10.jpg)
4. Brewer networkCentral Calibration Laboratory: Environment Canada, Toronto
(T. McElroy) : Triad: 3 Brewer instruments, regular Langley plot calibration of one instrument at Mauna Loa Observatory
European regional Brewer calibration center: Izaña (Tenerife) (A. Redondas): triad of Brewer spectrophotometers, regularly calibrated by the Langley plot method (redundancy in calibration scale)
Calibration of station instruments (every 2 years):• Canadian instruments: EC • for European instr.: European Brewer calibration center• Private companies (needs financing by stations)- IOS (International Ozone Service)- Kipp and Zonen (company producing Brewer instrument)
![Page 11: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/11.jpg)
-1.0%
-0.5%
0.0%
0.5%
1.0%
1970 1975 1980 1985 1990 1995 2000 2005
1976 scale 1987 scale 1991 scale 1993 scale D065 Abs. Cal at MLO
Average Percent difference normalized to total ozone=300 DU, averaged over Mu=3, 2, 1
5. Experience with networks Dobson
Stability of calibration of World primary Dobson instrument (D083): Percent difference in calculated total ozone based on corrections to D083 A and D tables from Langley plot calibrations at Mauna Loa Observatory, Hawaii (Evans et al., 2004 and Komhyr et al., 1989).
![Page 12: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/12.jpg)
Relative differences between standrad Dobson instruments and compared station instruments during initial calibrations of the
intercomparisons since 1969 (from Köhler et al., 2004).
![Page 13: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/13.jpg)
Experience with network: Brewer
• Brewer instruments: More advanced technology (fully automated, more flexible)
• Different institutions involved in calibration of station instruments (private companies, need funding from stations)
• Biannual Brewer workshop: information of new developments, training of station personnel, exchange in experience
![Page 14: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/14.jpg)
Comparison with satellite measurementsAbsolute and relative (in percent from the total number) number of sites with
‘‘no issues’’ (see text) in the record in 5 bins for Dobson, Brewer, and filter instrument sites located between 60oS and 60oN (from Fioletov et al., 2008).
0
20
40
60
80
100
1978-1985 1986-1990 1991-1995 1996-2000 2001-2006
0
10
20
30
40
50
60
1978-1985 1986-1990 1991-1995 1996-2000 2001-2006
Dobson Brewer Filter
Nu
mb
er o
f sta
tio
ns
![Page 15: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/15.jpg)
6. Future
![Page 16: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/16.jpg)
Ozone anomalies from model CMAM and measurements; Cly (Shepherd, 2008)
more ozone at lower stratosphere: greenhouse gas
![Page 17: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/17.jpg)
7. Conclusions• For column ozone: two independent networks
operated under the auspices of GAW/WMO• Networks: high quality measurements (except
in polar regions at low solar elevation): suitable for long-term trend analysis and validation of satellite measurements
• Satellite instruments: limited life times, merged satellite series required for long-term trend analysis. High quality ground based networks need continuation !
![Page 18: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/18.jpg)
Conclusions, cont.
• Ozone layer will recover from Ozone Depleting Substances (ODS, e.g. CFCs) (Montreal Protocol, 1987)
• Beneficial effect of Montreal Protocol on ozone layer by data analysis: controversial
• Demand for continuation of stratospheric ozone monitoring in future: Prediction of “super” recovery (more O3 in extratropical tropopause region): climate change
![Page 19: TOTAL OZONE MONITORING BY GROUNDBASED INSTRUMENTS AS PART OF GAW](https://reader035.vdocuments.us/reader035/viewer/2022070418/5681580c550346895dc57a60/html5/thumbnails/19.jpg)
Acknowledgement: SAG-OzoneGeir Braathen (WMO) Johanna Tamminen (IGACO-O3/UV)
Frank Baier, Jack Fishman, Sophie Godin-Beekmann, Robert Evans1, Ulf Koehler12, Takeshi Koide12, Ed Hare, Tom McElroy2, Alberto Redondas2, Herman Smit, Rene Stübi12, Johannes Staehelin (chair), Richard Stolarski, Ronald van der A, Karel Vanicek12, Mark Weber
1: involved in Dobson measurements2: involved in Brewer measurements