Question about PBLH

[michaelwindsorcurtin]

I am currently looking at the height of the Planetary Boundary Layer in order to study its impact on pollution. I am just wondering whether the height in meters is relative to sea level or to the first observed layer? I have searched through documentation but cannot find an answer. This is important as I am studying areas with large variations in altitude above sea level so if it is indeed calculated relative to sea level I will need to adjust it accordingly.

[GES DISC - xpan2]

Which data do you refer to, MERRA-2 or any observations? The PBLH might be defined differently in different data. Please refer to this paper:

Ding, F., Iredell, L., Theobald, M., Wei,J., & Meyer, D. (2021). PBL height from AIRS, GPS RO, and MERRA-2 products in NASA GES DISC and their 10-year seasonal mean intercomparison. Earthand Space Science, 8, e2021EA001859.https://doi.org/10.1029/2021EA001859.

[michaelwindsorcurtin]

Apologies I should have specified I was looking at the MERRA-2 dataset. Looking at the paper you provided it seems to use geopotential height which is based on sea level.

[GES DISC - xpan2]

PBLH in MERRA-2 is the height about ground level, not sea level.

[michaelwindsorcurtin]

Thank you very much for your answer and clarification. I am wondering where this is stated or is the usage of height above ground level implicit in the calculation of PBLH?

[mbosilov]

Thanks for your interest in MERRA-2. The MERRA-2 system (actually all GMAO systems) do not extrapolate profiles to where P > Ps, except a few quantities for thickness calculations. So yes, it is implicit.