Negative 3 D pressure (P)

[Din19]

Hello.

I have negative values of pressure (3D variable P) in the wrfout files just for one day (06:00 August 23,2018 -06:00 August 24,2018).

I use ERA-Interim reanalysis data as input.

What could be the possible reason behind the negative values of pressure?

Any help is appreciated.

Thank you.

 

[Ming Chen]

Please look at the full pressure, i.e., pressure = P + PB.
Does the pressure field look reasonable?

 

[Din19]

Please look at the full pressure, i.e., pressure = P + PB.
Does the pressure field look reasonable?

Thank you for your reply. When I add P and PB, I get positive values.
For example, on August 23, 2018, at 07:00 hours, the spatial average of P is - 106 Pa, while the spatial average for PB is 98657. 3 Pa.

Is it okay?
If I want to calculate the RH at 2m, should I use PSFC together with t2 and q2 in the formula(instead of p)? and will this formula (1.E2 * (p*q2/(q2*(1.-0.622) + 0.622))/(611.2*exp(17.67*(t2-273.15)/(t2-29.65)))) be still applicable?

Thank you

 

[Ming Chen]

When looking at pressure field, you should always look at the full pressure (P+PB) instead of P. The value looks reasonable.

yes you can use PSFC to calculate 2-m RH.

 

[Din19]

@Ming Chen Thank you very much for your help. Highly appreciate it.