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!
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.