1. Variability of Arctic Cloudiness from Satellite and Surface Data Sets University of Washington Applied Physics Laboratory Polar Science Center Axel J. Schweiger, Jeff Key 1, Xuanji Wang 1, Jinlun Zhang, Ron Lindsay 1) University of Wisconsin, SSEC

2. Questions: What is the variability of clouds over the Arctic Seas? Association with atm. circulation How does this variability impact sea ice?

3. Time Series of Cloud Fraction from TOVS Path-P and Surface Observations NP stations March 90Sept. 90 Schweiger et. al 1999

4. Spatial Variability Mean Seasonal Cloud Fraction Winter DJF Summer JJA 50% 90%

5. Climatology: Huschke, 1969 Canadian Arctic

6. TOVS Path-P Cloud Trends 1980-1998 (Ocean north of 60N) Winter DJF Spring MAM - 5%/decade+ 5%/decade

7. TOVS and APP Trends 1980-1998 (Ocean N of 60N) Winter DJF Spring MAM

8. TOVS Path-P and APP Trends 1980-1998 Summer JJA Fall SON

9. NP Surface Obs: 1955-1991 Winter DJF Spring MAM 3-year Running Mean See also Makshtas et al. 1999

10. ERA-40 and TOVS Cloud Winter (DJF)

11. Decadal Trends in Path-P Clouds Spring MAM +16% Winter DJF -16%

12. Circulation changes and Clouds Spring MAM -3 mb/Decade Change in SLP Spring MAM +16%/ Decade Change in Cloud Fraction

13. Changes in Cloud Fraction and Winds in Spring (MAM) Change in meridional component of thermal wind (Francis et al. subm.) 2 ms -1 /dec +15%/ Decade Change in Cloud Fraction

14. Changes in P-E (TOVS) -0.25 cm/month From Groves and Francis, 2002 Winter DJF -16% Nov-May 1998/90 – 1989/80

15. Surface Air Temperature

16. Surface Temperature Trend Winter (DJA) from IABP Cloud Fraction -16% Surface Air Temperature Trend

17. Correlation of Cloud Fraction with northern annular mode (NAM) Spring MAM Summer JJA R >0.6

18. Downwelling fluxes from TOVS at SHEBA SW FluxLW Flux RMS: 22 Wm -2 RMS: 20 Wm -2 Measured Flux

19. Trends in Fluxes Spring (MAM) ~+10 Wm -2 /Decade LWSW ~-10 Wm -2 /Decade

20. Mean Ice Thickness Variable vs. Mean SW fluxes

21. Effect of SW radiation on Ice Thickness Decrease in Ice Thickness SW Cloud Effect on Ice Thickness

22. Mean Ice Thickness Variable Tair (Control) vs. Mean Tair

23. Mean Ice Thickness Variable Tair - Mean Tair Sept 1991 Sep 1998

24. Conclusions Over the Arctic Ocean cloudiness in winter has decreased by 5%/decade Spring cloudiness has increased by about 5%/decade Cloud fraction from two different satellite-derived data sets show similar trends in cloudiness (though questions about winter remain) Strong regional variations exist Spring increase in cloudiness appears to be associated with changes in circulation Spring/Summer cloudiness is strongly associated with NAM Effect of clouds trends on SW/LW fluxes in spring time nearly cancel. Winter time LW decreased by about 2 Wm-2/Decade Effect of SW/Thermal forcing changes are relatively small over the 1980-1998 period but shows strong regional variations

25. Downwelling Fluxes Spring (MAM) SW -3.5 Wm -2 /decade LW +4.8 Wm -2 /decade

26. Downwelling Fluxes Winter (DJF) LW -2 Wm -2 /decade

27. Clouds in GCMs, 2xCO 2 Summer (April- Sept.) Winter (Oct.- Mar.)

28. Comparison with Climatology: Path-P, ISCCP-D2, Hahn (1995) (N80)

29. Trends?

30. TOVS Path-P Data Set Temperature, Humidity Profiles, Cloud- Fraction, Height, Surface Parameters from TOVS using 3I algorithm 100 km, daily resolution 1979-1998 (2001) Available from NSIDC Schweiger et al. 2002 (JGR, Sheba Issue) http://psc.apl.washington.edu/pathp