O. Yevteev, M. Shatunova, V. Perov, L.Dmitrieva-Arrago ,

1. The surface temperature variations due to the changes in solar flux and cloud water content (CWC) (COSMO-RU simulation results) O. Yevteev, M. Shatunova, V. Perov, L.Dmitrieva-Arrago, Hydrometeorological Center of Russia, 2010

2. Heat conductivity equation and surface heat budget Ts – surface temperature Tso – soil temperature Ts = Tso,k=1 Hsfcsensible heat flux Fqsfclatent heat flux Qrad,net surface radiation budget, Qrad,net = QS+QLW z1 z2 Tso • soil density, с soil heat capacity, • z – model’s levels inside soil layer

3. Surface radiation budget Sr – solar radiation absorbed by surface Lr– surface effective radiation (thermal) d – emissivity coefficient Qsw – solar radiative flux A – surface albedo sTso4 – surface longwave flux Eatm – long wave radiation of the atmosphere

4. Comparison of the surface heat budget components (W/m2) Results for the particular point (mid-latitude) could help to evaluate needed accuracy of the fluxes calculation Sr – solar radiation absorbed by surface Lr– surface effective radiation (thermal) H– turbulent sensible heat flux F– latent heat flux G– soil flux

5. HMC Spectral model temperature forecast evaluation Central Federal District , March, 2010 5

6. Cloud optical properties calculation Cloud extinction and absorption coefficients (Khvorostianov, 1980) δ - cloud water content, ρ – particle density, - mean radius Cloud particles size distribution function Cloud optical thickness , Δh – cloud thickness Cloud single scattering albedo

7. Radiation characteristics of the cloudy atmosphere and the underlying surface in dependence on the Liquid Water Content (Mid latitude summer atmosphere, one layer cloud, mean droplet radius 6 mkm, Solar zenith angle 60) 7

8. Radiation characteristics of the atmosphere and the underlying surface in dependence on the Mean Droplet Radius (Mid latitude summer atmosphere, one layer cloud, LWC 0.1 g/m3, Solar zenith angle 60) 8

9. Cooling rates (К/day) for the low level cloud in dependence on the mean droplet radius and LWC Cooling rates (К/day) for the middle level cloud in dependence on the mean droplet radius and LWC 9

10. The investigation of the surface temperature sensibility to the variations of the radiation fluxes and Cloud Water Content • Background simulation • “FLUX” experiment – values of the solar radiation absorbed by surface were increased on 30 W/m2 in the cloudy grid points • “CWC” experiment – values of the integral CWC were increased on 25% • Following pictures represent the mentioned experiments results obtained after 9h of the model’s simulation from 17.07.10, 0:00 Greenwich time : • Low level cloud cover; • Difference of the surface temperature “Ts (experiment) – Ts (background)”

11. “FLUX” experiment (+30 W/m2 ) Low level cloud cover Surface temperature difference

12. “CWC” experiment (+25%) Low level cloud cover Surface temperature difference

13. Conclusions • Surface temperature proves to be sensitive to the variation of the incoming solar flux and cloud microphysical properties (CWC) • The increasing of absorbed solar radiation by surface at 30 W/m2 brings to changes of the surface temperature at 1-2 grad, with maximum values up to 3 grad. • The increasing of the integral CWC at 25% brings to change of the surface temperature at 1 grad, mainly, with maximum values up to 3 grad. • All results are obtained without control of the cloud cover variations during the experiments. • The presented results show that physical processes in the atmosphere should be described with the most possible accuracy.

14. Thank you for attention!