Missing Layers in M2I6NPANA

[michaelwindsorcurtin]

Hello,

I am an applied economics student seeking to study the effects of pollution using temperature inversions. I apologise for any lack of meteorological and physics knowledge I may be demonstrating. As a part of it I am using the MERRA-2 data set to measure temperature inversions specifically M2I6NPANA.

I am finding that in the lower layers there a number of missing layers for certain coordinate pairs. I initially thought that it was due to altitude differences but which layers are present vary by time of day as well. I matched it with surface pressure M2I1NXLFO (aggregated at the 6 hour level) but found there were many cases where the surface pressure was higher than the missing values would imply or lower than what the present values would imply. I am wondering whether I made an issue data processing, I used CURL to download from NASA using R then converted it to Stata (a common statistical package in Econ), or whether these missing layers are due to other meteorological phenomenon. I have attached a screenshot showing my findings.

[mbosilov]

Please see the MERRA-2 FAQ https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/FAQ/ number 10. Meteorology is not extrapolated to grid points for pressure levels greater than the surface pressure (under ground).

[michaelwindsorcurtin]

Thank you very much for your quick response that FAQ page answers many of my questions however I am still wondering the reason why what values are missing are time dependant. In the FAQ page it states:
"There are some regions and pressure levels where the number of valid values may be available for a fraction of the times."
I am still slightly confused as to why available pressure levels can vary by time if they are taking data from the same area each time. The altitude of a place can't change so drastically can it? Is the data coming from slightly different areas within the grid each time, leading to different surface pressures, or are there slight fluctuations in pressure that cause this?

[mbosilov]

surface pressure increases and decreases with the weather, so around the edge of mountains, those changes will lead to more or less grid points undefined (underground).