Q:

Data source of the planetary boundary layer (PBL)

PBL is one key physical quantities aimed at analysing the condition of air pollution in an area of interest.
From WRF simulation, I can get the variable PBLH whixh represents the PBL height.
But, is there any free data source offering the observing PBL height all over the World?  
For now, I can get the weather data from the NOAA weather center. The data based on observations at airports doesn't conclude the quantitative information of PBL.   
Any recommendation would be appreciate! 

A:

Not exactly. The PBL is a quantity more or less derived. you may be able to derive it from upper air observations, but a direct observation of it is not yet available. Here are some methods: https://e-reports-ext.llnl.gov/pdf/235179.pdf
The question you are asking is the equivalent of "Can we observe the Jet stream?" We cannot observe the jet stream, but we can observe the winds, from which we infer the jet stream.

A:

The PBL depth is not easy to observe. It is the layer where the atmosphere is turbulent due to friction at the surface and convection. During daytime this leads to well-mixed potential temperature and specific humidity profiles and you can estimate where the well-mixed area ends. This, however, is complex, because you need accurate measurements of that. Even in radio-soundings it is hard to find the top of the PBL.
With more advanced equipment, as a ceilometer, you can use backscatter profiles, but these are more local measurements.
In short, a world wide set does not exist and probably (re)analysis data is the best you can get.
An interesting analysis can be found here:
http://kiwi.atmos.colostate.edu/pubs/Ahlgrimm-Randall.2006.pdf

