1. Simulations of the snow covered sea ice surface and microwave effective temperature Rasmus T. Tonboe, Gorm Dybkjær, Jacob L. Høyer EU FP6 Damocles, EU FP7 MyOcean, Greenland Climate Center NIMBUS 7 SMMR 6V ice surface temperature Boulder 2. March 2011, 2011

2. Combined thermodynamic and emission modelling Multilayer thermodynamic model for snow and sea ice with prognostic variables: T, density, d, grain size, salinity (Tonboe, 2005). Multilayer snow and sea ice microwave emission model, the sea ice version of MEMLS: Tb, e, Teff, penetration depth (Tonboe et al. 2006).

3. Why? Boundary condition in numerical weather prediction models and sea ice models The effective temperature together with the emissivity is a prerequisite for atmospheric sounding of the troposphere over sea ice (EUMETSAT OSI SAF) Validation of models and data: e.g. MyOcean ice surface temperature

4. Negative radiation balance in winter (Net long wave) Highly stable ABL during winter Positive Fs over thick ice, latent heat is small during winter The winter sea ice energy balance

6. The microwave emissivity (6-150GHz)

7. The effective temperature (6-150GHz)

8. Compared to standard tie-points Compared to effective emissivities derived from DMSP SSM/I data (from Catherine Prigent) Simulations compared to observations

9. The 2m air temperature vs. the surface temperature Bias possibly due to positive sensible heat budget during winter for thick ice (GoSI, 1986) icy surface Simulations Bouy temperature for validation of IR ice surface temperature products?

10. Measurements collocated with satellite observations (from Phil Hwang) 6 simulated multiyear ice profiles Penetration depth is a function of (ice) temperature and vice versa Physical temperature vs. effective temperature?

11. The temperature gradient in the snow layer is large during winter Snow ice interface temperature 6GHz brightness temperature

12. Temperature sounding near 50GHz T6v=0.77*Teff50v+57.06 50GHz sea ice emissivity product is being developed in EUMETSAT. Activities ongoing at Met. Office, Meteo France…

13. Six day composite IR IST March 2010

14. Validation Buoys measure either the air temperature or for the more compact buoys a temperature within the snow pack. The surface temperature is very difficult to measure. Field measurements using stationary or airborne (IR) radiometers could provide important validation data.

15. Variability Mean [K]STD [K] 2m air T 253.210.3 Snow surf. T 251.212.0 Snow/ice interf. T 257.38.1 Tb 6V 255.36.5 emissivity 6V 0.9860.0025

16. Conclusions The steep temperature gradient gives poor T correlation between different vertical levels in the snow/ice profile. The simulations indicate that the 6GHz brightness temperature can be related to the snow/ice interface temperature rather than being an effective temperature. It is related to the effective temperature at 50 GHz and it affects the ice growth rate. The snow surface temperature is among the most important variables in the surface energy balance equation and it significantly affects ABL structure, turbulent heat exchange and ice growth rate.