Some aspects on the Arctic energy budget and climatology

1. Some aspects on the Arctic energy budget and climatology Nils Gunnar Kvamstø (Nils.Kvamsto@gfi.uib.no) Input from Asgeir Sorteberg, Igor Ezau, Vladimir Alexeev and Øyvind Byrkjedal

2. OUTLINE OF THIS WEEKS LECTURES • Arctic Climatology 1 • Arctic Climatology 2 • Sea Ice – role, variability, mechanisms • Arctic climate variability and climate change

3. FRAMEWORKENERGY CONTENT IN AN ATMOSPHERIC COLUMN 0 ztop Hartmann (1994) Ch 6 ps 0

4. CHANGE OF ENERGY WITH TIME RTOA [uAE] [uAE+d(uAE)] RS, QH+QS

5. OCEANIC ENERGY BUDGET Li +Si so L – Latent heat; S – sensible heat TERRESTRIAL ENERGY BUDGET

6. The Arctic energy budget • Atmosphere: • Net radiation at top of atmosphere • Lateral transport • Surface fluxes (radiation, turbulence) • Ocean: • Surface fluxes (radiation, turbulence) • Lateral transport (water) • Latent heat (freezing/melting) • Ice transport • Land Surface: • Surface fluxes • Fresh water run off 70˚N

7. ANNUAL CYCLE ERA-40: Grided re-analysisUppala et al (2005) Annual means: dAE/dt =0, Fsfc = 11 Wm-2 Rtop=-110Wm-2 ∆F = 100Wm-2 Residual 1Wm-2 Serreze et al (2007) ∂AE/∂t <0 in autumn  Rtoa decreases (SW decr) Fsfc + ∆F increases. Damp rad effect ∂AE/∂t < 0 in spring  Rtoa increases (SW incr) Fsfc + ∆F decreases. Damp rad effect When Rtoa ≈ 0 Fsfc ≈ -∆F Both late spring and early autumn ∆F partly compensates sfc and toa fluxes

8. Annual cycle contd 0 Residuals’ space and time dependency 0 Serreze et al (2007)

9. ∆F – cosists mostly of dry static energy! ∆Fq ≈ Pr Fsfc = Rs + QE + QH, Rs dominates Often QH <0 due to inversion (small) QEalways positive Serreze et al (2007)

10. Assessment of ERA40 – comparison with sat.- and obs Data • ∆F well constrained (similar to NCEP) • Fsfc is in the upper range (2.5 – 11) (1Wm-2 = 0.1m sea ice in 1 yr!!) • Fsfc too high. Inaccurate cloud properties in ERA40 • Excessive Rtop – too high content of sensible heat • Remember satellite data are inaccurate as well Serreze et al (2007)

11. Energy flux from surface to atmosphere during winter • Largest fluxes from open ocean QH QE • Nearly 0 over land (QE into sfc [inversion] LW out) • Energy flux from atmosphere to surface during summer. • Largest over open ocean (SW and low albedo) • QE downward (melting ice & permafrost deepening active soil layer) Fsfc in ERA40 are higher than in other datasets. Indication of systematic error.But, the active soil layer may have increased(tawing) over the last decades => more heat stored larger fluxes. Serreze et al (2007)

12. Mean transport Serreze et al (2007)

13. Time series of total transport Pronounced annual cycle Weaker interannual cycle and low frequency variability. Trends? Serreze et al (2007)

14. ANNUAL ATMOSPHERIC ENERGY TRANSPORT Andresen and Sorteberg (2009)

15. Zonally averaged long term circulation – mean meridional circulation Polar cell Ferrel cell Deviations from mean matters as well –eddies v u Wallace and Hobbs (2006) Poleward transport by mean meridional circulation =

16. ATMOSPHERIC TRANSPORT BY EDDIES Mean height of 500 hPa surface January Hartmann (1994) Ch 6

17. ATMOSPHERIC TRANSPORT Total poleward heat tr = (tr by MMC) + (tr by qs eddies) + (tr by high freq eddies)

18. Annual average northward energy flux units in 1015 W

19. Zonally averaged northward flux of heat by eddies Hartmann (1994) Ch 6

20. ATMOSPHERIC HEAT TRANSPORT HEAT TRANSPORT ACROSS 60ºN MMC - MEAN MERIDIONAL CIRCULATION SE - STATIONARY EDDIES TE - TRANSIENT EDDIES Largest portion below 500hPa Max in 800-900hPa (1200-2500m) Not much in the Atmospheric Boundary Layer

21. LONGITUDINAL DEPENDENCE OF ΔF W and E of N. American through The seasonal in/out flow of energy is longitude dependent Both quasistationary waves and eddies contribute. Strong signatures from quasistationary waves in figure Transport below 3000m -> N.Atl more pronounced here

22. Ocean budget (+ atmosphere over ocean area only) 3 neglected 2,4,5,6 -> observed => 1 residual 5 – ice drift in the fram strait 4 – estimated from model runs. Sum out/inflow Fram, Bering, Barents, Can Arc (may be dependent on comp method) Serreze et al 2007

23. S0/OE Transport terms are steady => Annual cycle generated by Fsfc Seasonal cycle comes mostly from Barents sea. Large heat content on Nov – due to adv – This contributes to secondary max in Li in Dec Cycle gets lagged with depth

24. ARCTIC CLIMATOLOGYQUALITY CHECKED ARCTIC STATIONSFORCLIMATE STUDIES START YEAR Polyakov, 2003

25. EXAMPLES OF SOME DRIFITING STATIONS FRAM (1893-1896) MAUD (1922-1924) T-3 (1952-1971) NP-STATIONS (1952-1993) RUSS. PATROL SHIPS (1952-1983) DARMS (1958-1975) Russ. Drifting Automatic Radiometeorological Stations Example: NP-22 (1973-1982) Example: Pol (1953-1959, 1972) Arctic Climatology Atlas, 2002

26. 2m temperature JANUARY APRIL Arctic Climatology Atlas, 2002

27. 2m temperature JULY OCTOBER Arctic Climatology Atlas, 2002

28. TEMPERATURES AT SVALBARD

29. Northern hemisphere temperature Johannessen, 2003

30. PRECIPITATION JANUARY APRIL Arctic Climatology Atlas, 2002

31. PRECIPITATION JULY OCTOBER Arctic Climatology Atlas, 2002

32. PRECIPITATION AT SVALBARD

33. PRECIPITATION GADIENTS COAST/INNLAND

34. MEASURING ARCTIC PRECIPITATION

35. Annual fractions of liquid, solid and mixed precipitation at Svalbard Airport

36. SNOWDEPTH OVER THE ICE JANUARY APRIL Arctic Climatology Atlas, 2002

37. SNOWDEPTH OVER THE ICE JULY OCTOBER Arctic Climatology Atlas, 2002

38. SURFACE SHORTWAVE RADIATION: SW↓ 80ºN OBSERVATIONAL BASED Curry and Ebert (1992) SATELITE BASED (ISCCP, 1985) Rossow and Chang (1995) JUNE Curry et al., 1996

39. DOWNWARD LONGWAVE RADIATION AT SURFACE : LW↓ 80ºN OBSERVATIONAL BASED Curry and Ebert (1992) SATELITE BASED (ISCCP, 1985) Rossow and Chang (1995) JUNE Curry et al., 1996

40. CLOUD FRACTION 60-90ºN OBSERVATIONALLY BASED (varying sky illumination corrected, Hahn et al., 1994) OBSERVATIONALLY BASED SATELLITE BASED (ISCCP, new cloud detection algorithm) SATELLITE BASED (ISCCP) Curry et al., 1996

41. TOTAL CLOUDCOVER LOW CLOUDCOVER APRIL JANUARY Arctic Climatology Atlas, 2002

42. TOTAL CLOUDCOVER LOW CLOUDCOVER JULY Arctic Climatology Atlas, 2002

43. CLOUDS 1. Norwegian Sea Regime High cloudiness all year round Relatively large amounts of cumulus in winter caused by warm water under cold air 2. East Siberian Regime Very clear in winter due to anticyclone Very dry Cirrus dominates 3. Polar Ocean Regime Pronounced spring/summer maximum due to stratus Forms over cooler ice surface (warm advection. latent heat cooling)

44. LOCAL EFFECT OF CLOUDS ON THE RADIATION BUDGET CLOUD RADIATIVE FORCING at a given level z is the difference in net radiation between cloudy and clear sky usually given in W/m2 f LW longwave radiation SW shortwave radiation

45. LOCAL EFFECT OF CLOUDS ON THE SURFACE RADIATION BUDGET 80ºN SURFACE POSITIVE: WARMING AT SURFACE NEGATIVE: COOLING AT SURFACE OBSERVATIONALLY BASED Curry and Ebert (1992) JUNE Curry et al., 1996

46. LOCAL EFFECT OF CLOUDS ON THE SURFACE RADIATION BUDGET 80ºN SURFACE NET CLOUD FORCING CRF POSITIVE: CLOUDS CAUSE WARMING AT SURFACEMOST OF THE YEAR EXCEPT SUMMER CRF NEGATIVE: CLOUDS CAUSE COOLING AT SURFACEDURING SUMMER OBSERVATIONAL BASED Curry and Ebert (1992) SATELITE BASED (ISCCP, 1985) Rossow and Chang (1995) JUNE Large uncertainty! Curry et al., 1996

47. LINKS BETWEEN ENERGY BUDGET AND CLIMATOLOGY SUMMARY: Most times of the year two big terms are: 1. Heating by lateral advection 2. Cooling by longwave radiation to space In summer: 1. Heating by lateral advection 2. Cooling by surface (latent heat from ice/snow melting) ANNUAL SUMMER WINTER Nakamura and Oort, 1973 REMEMBER THE TRANSTORT IS A VERTICAL AND HORIZONTAL INTEGRAL

48. WINTERTIME ATMOSPHERIC CIRCULATION ANDLOW LEVEL TEMPERATURE

49. LOW LEVEL ATMOSPHERIC CIRCULATION Semipermanent Highs and Lows The Arctic is characterized by "semipermanent" patterns of high and low pressure. These patterns are semipermanent because they appear in charts of long-term average surface pressure. Aleutian Low This semipermanent low pressure center is located near the Aleutian Islands. Most intense in winter, the Aleutian Low is characterized by many strong cyclones. Travelling cyclones formed in the subpolar latitudes in the North Pacific usually slow down and reach maximum intensity in the area of the Aleutian Low. Icelandic Low This low pressure center is located near Iceland, usually between Iceland and southern Greenland. Most intense during winter, in summer, it weakens and splits into two centers, one near Davis Strait and the other west of Iceland. Like its counterpart the Aleutian Low, it reflects the high frequency of cyclones and the tendency for these systems to be strong. In general, migratory lows slow down and intensify in the vicinity of the Icelandic Low.

50. ATMOSPHERIC LOW LEVEL CIRCULATION Siberian High The Siberian High is an intense, cold anticyclone that forms over eastern Siberia in winter. Prevailing from late November to early March, it is associated with frequent cold air outbreaks over east Asia. Beaufort High The Beaufort High is a high pressure center or ridge over the Beaufort Sea present mainly in winter. The North American High is a relatively weak area of high pressure that covers most of North America during winter. This pressure system tends to be centered over the Yukon, but is not as well-defined as its continental counterpart, the Siberian High.