Hi there,

I’m trying to get the parts-per-billion/million of tropospheric NO2.

So far Harp is able to show how it can convert from ‘tropospheric column number density’ to NO2 column density (kg/m2) by using the HARPDUMP utility.

NO2_column_density {time} [kg/m2] (double) from

NO2_column_number_density {time} [molec/m2] (double)

I’m not clear on this output as it seems like it would average over the total column rather than the tropospheric column that I’m interested in.

This question has been looked at for another harp product here.

And the documentation shows that derivations are possible, though it’s not easy to understand how to make this work with the derive function.

Some advice on this would be much appreciated. And if I could make a small observation, the documentation around the derive function could be made simpler to understand. Ie. how does the information in the documentation about algorithms relate to how one would use the derive function?

Sorry if this is basic knowledge for some but I don’t quite get it yet.

D