Why some fields have undefined values anywhere?

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oib
Posts: 118
Joined: Mon Jan 31, 2011 3:29 pm

Why some fields have undefined values anywhere?

Post by oib » Fri Nov 25, 2011 11:27 am

EMS WRF version 3.1.1.5.1
NMM core
CU_PHISICS = 0

I'm finding that a lot of fields like these

acpcpsfc, surface Convective precipitation [kg/m^2]
cdconclm, atmos column Convective cloud cover [%]
cpratsfc, surface Convective precipitation rate [kg/m^2/s]
...
have anywhere, anytime UNDEFINED values.

Why this happens?
Is there a way to solve the problem?

meteoadriatic
Posts: 1565
Joined: Wed Aug 19, 2009 10:05 am

Re: Why some field has undefined values anywhere?

Post by meteoadriatic » Fri Nov 25, 2011 11:40 am

Because you disabled CU.

These are fields that are produced only by cumulus parametrization schemes. So when these schemes are off, these fields are empty. Nothing to worry about. When you disable CU scheme, then convection is explicitly handled by model dynamics. But keep in mind that you ideally need horizontal resolution 4km or better to properly handle convection up/downdrafts without help of CU scheme. Still, these fields will be empty in every case.

oib
Posts: 118
Joined: Mon Jan 31, 2011 3:29 pm

Re: Why some field has undefined values anywhere?

Post by oib » Fri Nov 25, 2011 1:43 pm

Thanks a lot meteoadriatic!
I needed these fields because I was looking for a way to distinguish the convective clouds (cumulus) and non convective clouds ;)
Any suggestions on how we can make this distinction?

meteoadriatic
Posts: 1565
Joined: Wed Aug 19, 2009 10:05 am

Re: Why some field has undefined values anywhere?

Post by meteoadriatic » Fri Nov 25, 2011 3:15 pm

Well, by omega. Cumulus clouds are where vertical speeds are high, and stratiform clouds would be where speeds are low. So for example you can overlay two fields; cloud cover in shaded mode and vertical speed in contours, so that you display only updrafts (not downdrafts) and only those updrafts that are above some threshold. Then, in those areas where there is cloud cover and updrafts are above some threshold, you can assume there is culumus cloudness. That's the best I can think out right now.

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