## Merra2

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dinesh_5497
Posts: 14
Joined: Wed Jun 28, 2023 1:43 pm America/New_York

### Merra2

Hi
I am not a chemistry expert, i need your support on unit conversion.
Sea Salt Surface Mass Concentration - PM 2.5 is in Kg/m3 (Volumetric method), i need to convert into mg/m2 (Deposition method).
For Example if i get 9.95 * 10^-9 kg/m3 as Sea Salt Surface Mass Concentration, what is the value in mg/m2?

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mgreene
Posts: 207
Joined: Wed Sep 25, 2019 9:35 am America/New_York
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### Re: Merra2

Hello,

Our MERRA-2 data and subject matter experts will examine your question and formulate a reply shortly.

mbosilov
Posts: 11
Joined: Thu Apr 16, 2020 9:03 am America/New_York

### Re: Merra2

Well, I'm not a chemistry expert either, but I learned unit conversions quite some time ago. Kg to mg, assuming that the constituent is the same in the conversion, then should just be a multiple of 10. I don't know how many powers of ten to tell you because its not clear if you want, milligram or microgram.

to change volume to area, then you need a length dimension. Since this is representative of the surface, you need the height of the lowest model level. The variable is called HLML and you can find that in the single level variable collection: tavg1_2d_flx_Nx (M2T1NXFLX): Surface Flux Diagnostics. Be aware that HLML varies in space and time and has units of m. so that, Kg/m2 = Kg/m3*HLML

I hope this helps

dinesh_5497
Posts: 14
Joined: Wed Jun 28, 2023 1:43 pm America/New_York

### Re: Merra2

I didn't understand it.
I searched in google and i got this
Here they have mentioned 60 m as HLML.
From the Merra2 File specification(https://gmao.gsfc.nasa.gov/pubs/docs/Bosilovich785.pdf)
I am going to use the below
tavg1_2d_aer_Nx (M2T1NXAER): Aerosol Diagnostics -> SSSMASS and SSSMASS25 .
can i use 60 as HLML for it or is it a complicated calculation

mbosilov
Posts: 11
Joined: Thu Apr 16, 2020 9:03 am America/New_York