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How to get / calculate surface pressure (surface pressure not available in CMIP6 data to be used as WRF input)


New member

I'm trying to use CMIP6 data as WRF input. However, the CMIP6 databases seem to only have the surface pressure (ps) fields at very low frequencies (day or month) and not in the 6 hourly input interval that I have for the other variables (ua, va, ta, etc). I basically actually have all the required WRF input fields to start the WRF run (well, except surface pressure). Do you know of a way how to get or calculate this variable? Some options are: A) Interpolating from daily or monthly to 6 hourly, which would not be very accurate, or B) Using geopotential height on first pressure level and orography height data, to calculate the surface pressure, assuming constant rho (1.225 kg/m^3), constant g (g=9.81 m/s^2), surface velocity approximately 0, and delta_p approximately equal to -rho*g*delta_z, so that p_surface = p_first_level+rho*g*h_first_level. Do any of these methods work? Do you know of a better way? I'd apperciate it greatly if you could help me with this.

Best Regards,
Hi, Mani,

The easy way to calculate surface pressure (psfc) is (suppose you have sea level pressure 'mslp', temperature, terrain etc)
psfc = mslp * ( 1.0 + gamma * ter / avgsfct) ** ( - g / ( Rd * gamma ) )
where gamma = 6.5E-3, g = 9.8, rd = = 287.04, "ter" is terrain height, avgsfct is surface temperature