# Can I estimate the long-term surface heat transfer coefficient based on a temperature difference between the air surface and ground surface?

I want to estimate the long-term or annual heat transfer coefficient for the earth's surface in a particular area where the mean annual air surface temperature is about 13$^\circ$C, and the mean ground surface temperature is about 15$^\circ$C. How can I do this?

The general expression is $h=\frac{Q}{A \cdot \Delta T}$. So I suppose the heat flux term $Q$ is some sort of sum of the earth's outward flux and the sun's inward flux (I have a good estimate of the former: ~70mW/m^2, but I don't know the latter for this latitude. The latitude is about 37 degrees south.)

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As Mark Rovetta notes in the answer below, this is not a convective heat transfer problem - you need to account for radiation. The simple linear heat transfer coefficient h is not the answer. Radiation is proportional to the 4th power of the absolute temperature. –  Mark Oct 2 '13 at 1:05
How is this not a convective problem, there is wind? –  user22620 Dec 18 '14 at 5:18