Sentinel 5P How Convert mol / m^2 to ppb?


#1

I write because I have a question, in the carbon monoxide manual maps the images are in ppb units, but if I visualize in product in Panoply I have them in mol m-2, I would like to know how do they convert to ppb because I would like to be able to buy with a regulation.

Thank you

Regards.


#2

Conversion of Sentinel 5Pā€™s total tropospheric column concentrations to ground-level ppb is not trivial, because the former quantifies the amount of NO molecules in the whole of the troposphere, and the latter, which regulations are interested in, relates to concentrations close to the ground. It is impossible to do this properly without having some additional data (about the atmospheric profile of the gas, elevation of the ground etc.).

For more discussion on this problem see https://earthscience.stackexchange.com/questions/8860/convert-omi-no2-vertical-column-density-molecules-cm2-into-mixing-ratio-ppm and https://www.researchgate.net/post/How_can_I_convert_the_unit_from_molecules_cm2_to_ppm .

To get an order-of-magnitute estimate for the ppb value, you could just divide the value by the height of the troposphere (0.1 mol * m^-2 / 10 km => 0.00001 mol * m^-3), then use a gas-concentration-converter (such as this one) to get the ppb value (0.00001 mol * m^-3 ~> 224 ppb).

The images in the user manual come from a research article ā€œMapping carbon monoxide pollution from space down to city scales with daily global coverageā€, where the authors state the following about adapting the total column measurement to match the ground measurement:

The retrieved CO column of TROPOMI is adapted to the altitude of the station by either cutting off the scaled mixing ratios profile at the station altitude or extending it assuming a constant elongation of the mixing ratio to lower altitude