S2P02 The National Science Foundation’s UV Monitoring...
1
The National Science Foundation’s UV Monitoring Network for Polar Regions: Recent Advancements and New Results The United States National Science Foundation’s UV Monitoring Network for Polar Regions is currently in its fourteenth year of operation. Antarctic network sites include McMurdo, Palmer, and South Pole Stations. Data products and their means of distribution, and measurement accuracy have advanced over time. This presentation gives an overview of the current state of the network, its instruments, and available data. The deployed spectroradiometers have been improved recently to decrease measurement uncertainties caused by the instruments’ entrance optics. New data products include daily UV doses for various weighting functions, and retrievals of total column ozone. Network data is available via the Internet, including complementing Operations Reports. UV data from recent years indicate that ozone depletion remains a persistent threat to the Antarctic environment. Unprecedented UV levels occurred in McMurdo, Palmer, and South Pole Stations in 1998. The large-size ozone hole in 2000 affected populated areas in South America when UV levels rose to record levels. The data show the high variability in UV on time scales from days to years. Trends in UV observed during the last decade of network operation are difficult to assess, however, because of the large year-to-year changes in UV, which mask possible continuous increases. Due to higher sun elevations later in the year, maximum levels at Antarctic sites occur in November and early December, months usually considered “post ozone hole”. This suggests that changes in the duration and spatial coverage of ozone depletion have greater influence on recent UV levels than the absolute magnitude of ozone losses alone. Biospherical Instruments Inc., 5340 Riley St., San Diego, CA 92110-2621, USA. Web: www.biospherical.com. E-mail: [email protected] G. Bernhard, C.R. Booth, J.C. Ehramjian S2P02 Abstract Instrumentation Instruments deployed in the National Science Foundation's UV monitoring network are SUV-100 spectroradiometers [Booth et al., 1994] operated and maintained by Biospherical Instruments Inc. The measured quantity is global (sun+sky) spectral irradiance. The SUV-100 features: • Automated operation • A spectral range of 280 - 600 nm • A spectral resolution of 1.0 nm FWHM • Built-in irradiance and wavelength standards to monitor instrument stability. Acknowledgements The United States National Science Foundation’s Polar UV Monitoring Network was established under the guidance of P. Wilkniss, former Director of the Office of Polar Programs. The network is operated and maintained by Biospherical Instruments under a contract from the NSF Office of Polar Programs (Dr. Polly Penhale) via Raytheon Polar Services. References Booth, C.R., T.B. Lucas, J.H. Morrow, C.S. Weiler, P.A. Penhale [1994]. The United States National Science Foundation's polar network for monitoring ultraviolet radiation. Antarctic Research Series, 62, 17-37. Bernhard, G., C.R. Booth, J.C. Ehramjian [2001]. Comparison of measured and modeled spectral ultraviolet irradiance at Antarctic stations used to determine biases in total ozone data from various sources, in: UV Ground- and Space-Based Measurements, Models, and Effects, Proceedings SPIE, 4482, in press. In addition, NSF network data has been referenced in more than 100 research papers published in refereed journals. For a full bibliography, please visit our web site: www.biospherical.com. Network Access Recent Advancements and New Results Recent Advancement and New Results: • Instrument Improvements • Addition of a new site • Addition of new ancillary sensors • New data products • Measurement / Model interface • Retrievals of total column ozone • Analysis of changes in UV climate • Improved data access via Internet • Guide for students and teachers The website currently features: Detailed description of instruments and sites Weekly updates on radiation levels at the network sites, both in graphical and numerical form. Access to data and Network operation reports Access to recent presentations in PDF-Format An extensive list of references Standard data products include amongst others: Full resolution spectra of global irradiance in ASCII format Tables in ASCII comma separated value (CSV) format with: Spectral Irradiance at specific wavelengths Spectral Integrals (e.g. UV-A and UV-B) Biologically weighted irradiance (e.g. CIE-erythema) Daily Doses Available data cover the period from 1989 to present. Network Sites Network information and data are published on our web site: Austral Sites Palmer, 65°S Ushuaia, 55°S McMurdo, 78°S South Pole, 90°S Austral network sites. Boreal network sites currently include San Diego, CA (32° N); and Barrow, Alaska (71° N). A new site at Summit, Greenland (72° N) will be added soon. Total column ozone values derived from SUV-100 measurements can be used to validate satellite ozone data. The graph shows results from the South Pole, demonstrating the good agreement between SUV-100 and Dobson ozone observations, and the effect of profiles on the results. The 5-10% bias between TOMS and Dobson measurement at high- latitude southern-hemisphere sites is confirmed with the SUV- 100 data. See [Bernhard et al., 2001] for more details. 0.9 0.95 1 1.05 1.1 1.15 1.2 Oct-2000 Nov-2000 Dec-2000 Jan-2001 Date Solar Elevation > 15° S.E.<10° Ratio Referenced to CMDL-Dobson SUV-100 using CMDL-Profiles; Bass and Paur Cross Section SUV-100 using AFGL Subarctic Summer Profile; Bass and Paur SUV-100 using CMDL-Profiles; Molina and Molina Cross Section EarthProbe TOMS V.7 Overpass www.biospherical.com Location of new SUV-150 at Summit, Greenland 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 290 310 330 350 370 Wavelength in nm Measurement / Model 0.01 0.1 1 10 100 1000 Ratio Measurement / Model Measured Irradiance Spectral Irradiance [mW/(m² nm)] South Pole, SZA=68.6° The fore-optics of all network instruments were upgraded during 2000 and exhibit now negligible azimuth errors. The picture shows a new apparatus to characterize the angular response of the instrument at the South Pole. A new network site will be added in October 2001 at “Summit”, Greenland (72°N, 38°E), located in the center of the ice sheet. The deployed instrument will be a re-engineered SUV-150 spectroradiometer with fiber optics. Compared to the SUV-100 it will feature better angular response, wavelength resolution, and detection limit. An interface between network data and the radiative transfer model UVSPEC/libRadtran* has been developed. Comparisons of cosine-corrected SUV-100 measurements and model results typically agree to within ±5% for solar zenith angles smaller than 80°. This allows for calculation of ozone values from SUV-100 data with high accuracy (see block at right), check the quality of measurements, and study the radiative transfer. * Available at www.libradtran.org 0 1 2 3 4 5 6 7 8 9 1988 1989 1992 1993 1996 1997 2000 Year Daily Erythemal Dose [kJ/m²] Palmer Station Daily doses were recently added to the suite of standard network data products. The graph above shows daily erythemal dose at Palmer Station covering 13 annual cycles. South Pole 0 0.04 0.08 0.12 1-Oct 1-Nov 2-Dec 2-Jan Month 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 Daily Setlow Dose (kJ/m²) 30-Nov 20-Nov Palmer 0 1 2 3 4 5 6 1988 1990 1992 1994 1996 1998 2000 Year Sep; (38±48)% / 10yr; R² = 0.27 Oct; (11±57)% / 10yr; R² = 0.02 Nov; (59±54)% / 10yr; R² = 0.38 Dec; (25±42)% / 10yr; R² = 0.18 Average Daily CIE Dose (kJ/m²) Changes in UV levels over the year were studied by analyzing average monthly erythemal daily doses. There is a large year-to-year variability in UV owing to differences in column ozone. UV levels for the time period 1988-2000 are generally increasing, but trends are not significant at the 2 - level. This suggests that a time span of 13 years is too short for solid trend assessments of UV data. Record UV levels occurred in McMurdo, Palmer, and South Pole Stations in 1998. Highest UV levels usually occur in late November when relatively high sun elevations coincide with low ozone values. 0 1 2 3 4 5 6 7 1-Jan 20-Feb 10-Apr 30-May 19-Jul 7-Sep 27-Oct 16-Dec Date Erythemal Daily Dose (kJ/m²) 1991-1999 Average 1991-1999 2000 2001 Ushuaia: Erythemally (CIE) Weighted 12-Oct-2000, 140 DU The outskirts of the record-size ozone hole in 2000 moved over Ushuaia for several days in October. On 12-Oct-2000, TOMS reported 140 DU. The erythemal daily dose on this day was the highest October-dose ever observed by the NSF spectroradiometer. The plot shows that UV levels were significantly higher than typical summer values for Ushuaia. Multi-channel filter instruments (type GUV-511) will soon be deployed at all network sites. They will provide real-time UV measurements at 305, 320, 340, and 380 nm, as well as PAR measurements. Data will be available via the Internet, updated every minute. These data may guide researchers on station for finding the best timing for UV-effect experiments. A new interface to access network data via the Internet is currently under development. Users can select specific data products for a given site and time period by filling out simple forms (see left picture). Requested data are either displayed graphically (see right picture), or provided as a custom-generated data file for download. Full-resolution UV spectra will automatically be compressed to optimize file-transfer. The example to the right shows spectral irradiance at 300 and 340 nm measured at Palmer station during October and November 2000. Data at 300 nm decreased rapidly after 23-Oct-2000 as the ozone hole was shrinking and its center moving toward the Atlantic Ocean. Data at 340 nm is not affected by the ozone concentration. A “Teacher and Student's Guide to Ozone and UV” will soon be added to our web site. It was compiled by the high-school students Kirstin Price and Scott Baker, who were interns at Biospherical Instruments. The SUV-100 spectroradiometer.
Transcript of S2P02 The National Science Foundation’s UV Monitoring...
The National Science Foundation’s UV Monitoring Network for Polar Regions: Recent Advancements and New Results
The United States National Science Foundation’s UV Monitoring Network for Polar Regions is currently in its fourteenth year ofoperation. Antarctic network sites include McMurdo, Palmer, andSouth Pole Stations. Data products and their means of distribution, and measurement accuracy have advanced over time. This presentation gives an overview of the current state of the network, its instruments, and available data. The deployed spectroradiometers have been improved recently to decrease measurement uncertainties caused by the instruments’ entrance optics. New data products include daily UV doses for various weighting functions, and retrievals of total column ozone. Network data is available via the Internet, including complementing Operations Reports.
UV data from recent years indicate that ozone depletion remains a persistent threat to the Antarctic environment. Unprecedented UV levels occurred in McMurdo, Palmer, and South Pole Stations in 1998. The large-size ozone hole in 2000 affected populated areas in South America when UV levels rose to record levels. The datashow the high variability in UV on time scales from days to years. Trends in UV observed during the last decade of network operation are difficult to assess, however, because of the large year-to-year changes in UV, which mask possible continuous increases. Due tohigher sun elevations later in the year, maximum levels at Antarctic sites occur in November and early December, months usually considered “post ozone hole”. This suggests that changes in the duration and spatial coverage of ozone depletion have greater influence on recent UV levels than the absolute magnitude of ozone losses alone.
Biospherical Instruments Inc., 5340 Riley St., San Diego, CA 92110-2621, USA. Web: www.biospherical.com. E-mail: [email protected]
G. Bernhard, C.R. Booth, J.C. Ehramjian
S2P02
Abstract Instrumentation
Instruments deployed in the National Science Foundation's UV monitoring network are SUV-100 spectroradiometers[Booth et al., 1994] operated and maintained byBiospherical Instruments Inc. The measured quantity is global (sun+sky) spectral irradiance. The SUV-100 features:
• Automated operation • A spectral range of 280 - 600 nm• A spectral resolution of 1.0 nm FWHM• Built-in irradiance and wavelength standards to
monitor instrument stability.
Acknowledgements
The United States National Science Foundation’s Polar UV Monitoring Network was established under the guidance of P. Wilkniss, former Director of the Office of Polar Programs. The network is operated and maintained by Biospherical Instruments under a contract from the NSF Office of Polar Programs (Dr. Polly Penhale) via Raytheon Polar Services.
ReferencesBooth, C.R., T.B. Lucas, J.H. Morrow, C.S. Weiler, P.A. Penhale [1994]. The United States National Science Foundation's polar network for monitoring ultraviolet radiation. Antarctic Research Series, 62, 17-37.
Bernhard, G., C.R. Booth, J.C. Ehramjian [2001]. Comparison of measured and modeled spectral ultraviolet irradiance at Antarctic stations used to determine biases in total ozone data from various sources, in: UV Ground- and Space-Based Measurements, Models, and Effects, Proceedings SPIE, 4482, in press.
In addition, NSF network data has been referenced in more than 100 research papers published in refereed journals. For a full bibliography, please visit our web site: www.biospherical.com.
Network Access
Recent Advancements and New Results
Recent Advancement and
New Results:
• Instrument Improvements
• Addition of a new site
• Addition of new ancillary sensors
• New data products
• Measurement / Model interface
• Retrievals of total column ozone
• Analysis of changes in UV climate
• Improved data access via Internet
• Guide for students and teachers
The website currently features:
�Detailed description of instruments and sites
�Weekly updates on radiation levels at the network sites, both
in graphical and numerical form.
�Access to data and Network operation reports
�Access to recent presentations in PDF-Format
�An extensive list of references
Standard data products include amongst others:
�Full resolution spectra of global irradiance in ASCII format
�Tables in ASCII comma separated value (CSV) format with:
� Spectral Irradiance at specific wavelengths
� Spectral Integrals (e.g. UV-A and UV-B)
� Biologically weighted irradiance (e.g. CIE-erythema)
� Daily Doses
Available data cover the period from 1989 to present.
Network Sites
Network information and data are published on our web site:Austral Sites
Palmer, 65°S
Ushuaia, 55°S
McMurdo, 78°S
South Pole, 90°S
Austral network sites. Boreal network sites currently include San Diego, CA (32° N); and Barrow, Alaska (71° N). A new
site at Summit, Greenland (72° N) will be added soon.
Total column ozone values derived from SUV-100 measurements can be used to validate satellite ozone data. The graph shows results from the South Pole, demonstrating the good agreement between SUV-100 and Dobson ozone observations, and the effect of profiles on the results. The 5-10% bias between TOMS and Dobson measurement at high-latitude southern-hemisphere sites is confirmed with the SUV-100 data. See [Bernhard et al., 2001] for more details.
0.9
0.95
1
1.05
1.1
1.15
1.2
Oct-2000 Nov-2000 Dec-2000 Jan-2001
Date
Solar Elevation > 15°S.E.<10°
Rat
io R
efer
ence
d to
CM
DL-
Dob
son
SUV-100 using CMDL-Profiles; Bass and Paur Cross Section
SUV-100 using AFGL Subarctic Summer Profile; Bass and Paur
SUV-100 using CMDL-Profiles; Molina and Molina Cross Section
EarthProbe TOMS V.7 Overpass
www.biospherical.com
Location of new SUV-150 at Summit, Greenland
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
290 310 330 350 370Wavelength in nm
Mea
sure
men
t / M
odel
0.01
0.1
1
10
100
1000
Ratio Measurement / Model
Measured Irradiance
Spe
ctra
l Irr
adia
nce
[mW
/(m² n
m)]South Pole, SZA=68.6°
The fore-optics of all network instruments were upgraded during 2000 and exhibit now negligible azimuth errors. The picture shows a new apparatus to characterize the angular response of the instrument at the South Pole.
A new network site will be added in October 2001 at “Summit”, Greenland (72°N, 38°E), located in the center of the ice sheet. The deployed instrument will be a re-engineered SUV-150 spectroradiometer with fiber optics. Compared to the SUV-100 it will feature better angular response, wavelength resolution, and detection limit.
An interface between network data and the radiative transfer model UVSPEC/libRadtran* has been developed. Comparisons of cosine-corrected SUV-100 measurements and model results typically agree to within ±5% for solar zenith angles smaller than 80°. This allows for calculation of ozone values from SUV-100 data with high accuracy (see block at right), check the quality of measurements, and study the radiative transfer.
* Available at www.libradtran.org
0
1
2
3
4
5
6
7
8
9
1988 1989 1992 1993 1996 1997 2000
Year
Da
ily E
ryth
em
al D
ose
[kJ
/m²]
Palmer Station
Daily doses were recently added to the suite of standard network data products. The graph above shows daily erythemal dose at Palmer Station covering 13 annual cycles.
South Pole
0
0.04
0.08
0.12
1-Oct 1-Nov 2-Dec 2-JanMonth
1988198919901991199219931994199519961997199819992000
Dai
ly S
etlo
w D
ose
(kJ
/m²)
30-Nov
20-Nov
Palmer
0
1
2
3
4
5
6
1988 1990 1992 1994 1996 1998 2000Year
Sep; (38±48)% / 10yr; R² = 0.27Oct; (11±57)% / 10yr; R² = 0.02Nov; (59±54)% / 10yr; R² = 0.38Dec; (25±42)% / 10yr; R² = 0.18
Ave
rag
e D
aily
CIE
Do
se (
kJ/m
²)
Changes in UV levels over the year were studied by analyzing average monthly erythemal daily doses. There is a large year-to-year variability in UV owing to differences in column ozone. UV levels for the time period 1988-2000 are generally increasing, but trends are not significant at the 2�-level. This suggests that a time span of 13 years is too short for solid trend assessments of UV data.
Record UV levels occurred in McMurdo, Palmer, and South Pole Stations in 1998. Highest UV levels usually occur in late November when relatively high sun elevations coincide with low ozone values.
0
1
2
3
4
5
6
7
1-Jan 20-Feb 10-Apr 30-May 19-Jul 7-Sep 27-Oct 16-DecDate
Ery
them
al D
aily
Dos
e (k
J/m
²)
1991-1999Average 1991-199920002001
Ushuaia: Erythemally (CIE) Weighted
12-Oct-2000, 140 DU
The outskirts of the record-size ozone hole in 2000 moved over Ushuaia for several days in October. On 12-Oct-2000, TOMS reported 140 DU. The erythemal daily dose on this day was the highest October-dose ever observed by the NSF spectroradiometer. The plot shows that UV levels were significantly higher than typical summer values for Ushuaia.
Multi-channel filter instruments (type GUV-511) will soon be deployed at all network sites. They will provide real-time UV measurements at 305, 320, 340, and 380 nm, as well as PAR measurements. Data will be available via the Internet, updated every minute. These data may guide researchers on station for finding the best timing for UV-effect experiments.
A new interface to access network data via the Internet is currently under development. Users can select specific data products for a given site and time period by filling out simple forms (see left picture). Requested data are either displayed graphically (see right picture), or provided as a custom-generated data file for download. Full-resolution UV spectra will automatically be compressed to optimize file-transfer. The example to the right shows spectral irradiance at 300 and 340 nm measured at Palmer station during October and November 2000. Data at 300 nm decreased rapidly after 23-Oct-2000 as the ozone hole was shrinking and its center moving toward the Atlantic Ocean. Data at 340 nm is not affected by the ozone concentration.
A “Teacher and Student's Guide to Ozone and UV” will soon be added to our web site. It was compiled by the high-school students Kirstin Price and Scott Baker, who were interns at Biospherical Instruments.
The SUV-100 spectroradiometer.
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