Coordinating and Integrating UV Observations in Svalbard

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1 Coordinating and Integrating UV Observations in Svalbard Georg Hansen & Tove Svendby, NILU, Norway Boyan Petkov & Vito Vitale, ISAC-CNR, Italy Piotr Sobolwski, IGFPAS, Poland Josef Elster, University of South Bohemia, Czech Rep. Kamil Laska, Masaryk University, Czech Rep.

2 Acknowledgments We thank the Research Council of Norway/ Svalbard Science Forum for funding the UV- ICARE project (Project No: 7644/E) in the frame of the Svalbard Strategic Grant program. We gratefully acknowledge the work of our colleagues, including station engineers, in gathering long-term data series.

3 The UV-ICARE project Geographic position of the stations measuring solar UV irradiance and total ozone at Svalbard. - Continuous interest in the atmospheric ozone layer and UV doses on the ground: two years with close-to-ozone-hole conditions in the Arctic in the recent decade (, 6) The ozone story is not over yet! - Previous inter-comparison activities of existing UV/ozone measurements (Ny- Ålesund, Hornsund, Barentsburg?) were not completed satisfactorily. - Establishment of new station in Longyearbyen, starting of Brewer measurements in Ny-Ålesund Revisitation of existing data series since 99s and intercomparison campaign of all current instruments

NILU s Ozone/UV monitoring instruments GUV 54 multi-wavelength moderate bandwidth filter instrument: Five UV channels (35 nm, 33 nm, 3 nm, 34 nm and 38 nm) FWHM ~ nm in

observations of 3 6 nm spectral range ( nm resolution) with diode array detector derivation of total O 3, NO, O 4 and H O columns based on DOAS approach during periods of

4 NILU s Ozone/UV monitoring instruments GUV 54 multi-wavelength moderate bandwidth filter instrument: Five UV channels (35 nm, 33 nm, 3 nm, 34 nm and 38 nm) FWHM ~ nm in UV channels Main parameter: UV doses; additionally total O 3 column, effective albedo/cloud cover Start of measurements: 995 SAOZ UV/Vis spectrometer: Zenith sky observations of 3 6 nm spectral range ( nm resolution) with diode array detector derivation of total O 3, NO, O 4 and H O columns based on DOAS approach during periods of SZA 8 93 (sunrise, sunset measurements; no measurements during summer and winter) Start of measurements: 99 Dobson spectrometer no. 8: calibrated/reliable measurements from 994 to 3

nm operational since 8 Data coverage: since 8, but with gaps in and most of

5 Instrumentation at the Dirigibile Station, Ny-Ålesund UV-RAD radiometer: measures spectral radiance in 8 channels between 3 to 4 nm FWHM ca. nm operational since 8 Data coverage: since 8, but with gaps in and most of 3 Brewer spectrometer: Operational since: 3 Calibrated in 5 in cooperation with NILU

6 Polish Polar Station Hornsund February 996: Start of measurements of UV-B radiation at the Polish Polar Station, Hornsund, Svalbard, (77.N, 5.55E), using Robertson Berger type UV meter. Operated by Institute of Geophysics, PAS. Hornsund

7 New/additional Instrumentation Since April 5: UVS-AE-T UV Radiometer Sunshine duration meter CSD- CM Pyranometer (All instruments from Kipp & Zonen)

8 Solar UV Radiation Monitoring in Longyearbyen Operated by: University of South Bohemia in České Budějovice, Czechia Coordinates: N78.39, E Altitude: 7 m a.s.l. Location: Roof of Julius Payer House, Czech Research Station, Longyearbyen In operation from: 4 August 7 Instrumentation and settings UVS-E-T radiometer (Kipp & Zonen, Holland) EdgeBox V Data Logger (EMS, Czechia) Sampling interval: 5 s Recording interval: 5 s Julius Payer House in Longyearbyen Installation of UVS-E-T radiometer Credits: Norwegian Polar Institute

9 Total ozone measurements at Ny-Ålesund Data series composed of groundbased (since 99: SAOZ, Dobson, GUV) and satellite data (979-99: TOMS-Nimbus 7, -Meteor-3) Separate trends before (and including) 997 and after 997: -7.%/decade (annual, ) -.4%/decade (annual, 998-5) Large seasonal differences: -.7%/dec. (March-May, ).%/dec. (March-May, 998-5) -.6%/dec. (June-August, ) -.6%/dec. (June-August, 998-5) Time series of monthly mean total ozone (mixed sources) at Ny-Ålesund (upper panel); residuals of months March-October after removal of annual cycle and trends before and after 997 (lower panel).

UV measurements and trends Ny-Ålesund Annual doses (day 6 85): continuous GUV data, except 5 Annual dose trend: -.8%/decade (non-significant) Large variability in monthly trends: Spring equinox: -8.

10 UV measurements and trends Ny-Ålesund Annual doses (day 6 85): continuous GUV data, except 5 Annual dose trend: -.8%/decade (non-significant) Large variability in monthly trends: Spring equinox: -8.% / decade (marked cloud transmittance reduction: more clouds?) June: -.7% / decade (cloud transmittance reduction: less snow?) July: +5.8% / decade (cloud transmittance increase: less clouds?) September: -.5% / decade (cloud transmittance reduction: less snow?)

11 Comparison of longest UV time series Daily erythemal dose (kj m - ) Daily erythemal dose (kj m - ) 3 3 Ny-Ålesund Hornsund Years Daily erythemal dose time series at Ny-Ålesund (upper panel) and Hornsund (lower panel) as measured with the GUV filter instrument (Ny-Ålesund) and combined Robertson Berger UV meter (996 4) and UVAE-T Kipp & Zonen radiometer (4 6) at Hornsund

12 Spectral analysis of time series AMPLITUDE A (kj m - ) Ny-Ålesund Hornsund Prominent features: - Annual cycle - Semi-annual cycle: albedo/snow cover? - 4-monthly cycle:? - Separation of long-term and short-term variations for further analysis at a period of 7 days PERIOD (days)

13 Long- vs. short-term variations Daily erythemal dose (kj m - ) Long period component (kj m - ) Short period component (kj m - ) Ny-Ålesund Years Hornsund Years Long-term variations very similar at the two stations, but larger amplitudes of short-term variations at Hornsund

14 Comparison, continued Daily erythemal dose DH (kj m-) at Hornsund Measured values Long period component Short period component Daily erythemal dose DN (kj m ) at Ny-Ålesund DH = *DN R ² =.8 DH = *DN R ² =.98 Very good (mean) correlation between long-term components (but much larger deviations in individual years), obviously less spreading in Ny-Ålesund short-term variations

15 Comparison GUV UV-RAD Comparison of two different instruments at the same location: only started Very good dynamic agreement between the two instruments, but systematic offset (higher doses derived from GUV) Candidate for explanation: radiation transfer model systematic discrepancy in effective cloud transmittance

16 Summary and Outlook UV-ICARE - an effort to expand the UV network to all settlements on Svalbard and to coordinate and homogenize the different measurement techniques Re-analysis and comparison of existing UV data (ca. years) ongoing Negative trend (statistically non-significant) of annual integrated dose since the late 99s Large variability of monthly integrated doses: probably combined effect of ozone recovery, changes in cloudiness, reduced snow cover season, reduced aerosol load End of April 8: inter-comparison campaign in Ny-Ålesund including instruments from all stations with UV measurements

Centre for Polar Ecology, Faculty of Sciences, University of South Bohemia in České Budějovice, Czech Republic

Centre for Polar Ecology, Faculty of Sciences, University of South Bohemia in České Budějovice, Czech Republic The operation of the Czech Arctic Research Infrastructure Josef Svoboda Station (as a part of the Czech Polar Research Infrastructure, CzechPolar2) was supported by the project LM2015078 CzechPolar2 -