[GRASS-user] Evapotranspiration Estimation

[Ghansah_Benjamin_IWM]

Dear Sirs,

Please I am estimating evapotranspiration (i.evapo.pt) from satellite imagery using GRASS 7.0.2. However, I have the following concerns that I will be glad if you could help me solve:

1. I used the relation i.evapo.pt [-z] net_radiation=name soil_heatflux=name air_temperature=name atmospheric_pressure=name priestley_taylor_coeff=float output=name

I have image file of the **net_radiation, soil_heatflux, air_temperature (**Which I assume is the same as the surface temperature)

The priestley_taylor_coeff constant 1.26 is used.

However, I don’t know how to compute or derive a map for the atmospheric_pressure

Can you help me out with it?

2. I also computing the sensible heat flux ( i.eb.hsebal01)

I have successfully obtained all of the other parameters except the aerodynresistance.

I will be glad if you can direct me on how to obtain this also

Thank you,

Best regards

Benjamin Ghansah

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