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Clarification Needed for the PRECIS generated SO2 data
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Author:  prasanta [ Tue Apr 22, 2014 5:14 pm ]
Post subject:  Clarification Needed for the PRECIS generated SO2 data

I am Prasanta Kumar Bal, Scientist Centre for Climate Change and Adaptation research , Anna University, Chennai, India.

I have completed the PRECIS model runs for AR4 simulations by using HadCM3Q LBC data.

I need some clarifications to analyze SO2 data.

I have collected observation data for the Chennai city, Tamil Nadu which is in mg/m3 (observation data is ambient so2 data i.e after the emission, how much so2 is remained in the atmosphere. This is not the stack emission data from the industry )

so which parameter I need to select from the PRECIS output which are listed as below to validate with the observational data? The output is in kg/m2/sec. How to convert kg/m2/sec to mg/m3?

Stash code Description Units

58 sulpher dioxide emmisions kg/m2/sec

101 so2 mass mixing ratio kg/kg

121 natural so2 emissions kg/m2/sec

126 high level so2 emissions kg/m2/sec

Please can you provide me the description about the each stash code.


Prasanta Kumar Bal

Author:  dmhg [ Tue Apr 22, 2014 5:17 pm ]
Post subject:  Re: Clarification Needed for the PRECIS generated SO2 data

Dear Prasanta,
I relay the response from Simon, who is quoting another colleague at the Met Office:

Given what the observational data are, it looks like STASH code 00-101 ("SO2 MASS MIXING RATIO AFTER TSTEP") from the lowest model layer would be the obvious thing to compare against.

(1) As the name says, this is mass mixing ratio, so would need to be multiplied by air density to convert to kg/m3 (and then to mg/m3).

(2) As with all sulphur-cycle variables, this one is mass mixing ratio of S-in-SO2, i.e. only the mass of the sulphur atom is considered. If the observations are of the mass of SO2 (which is likely), then as well as multiplying by air density, 00-101 will need to be multplied by the ratio of the atomic weights of SO2 and S (which, conveniently enough, in this case is just a multiplication by 2: S=32, O=16, so SO2/S = (32+16+16)/32 = 2)

Thank you,
David on behalf of Simon T and the PRECIS team

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