The best possible option for you is to derive mixing layer height from the radiosonde profile information. Following is a useful reference:

http://www.atmos-meas-tech.net/7/1701/2014/amt-7-1701-2014.pdf

You can download the radiosonde profiles data sets for various stations at the following link: (For New Delhi, the station number is 42182)

http://weather.uwyo.edu/upperair/sounding.html

Note that there are various other methods, but the data sets are limited. 

http://weather.uwyo.edu/upperair/sounding.html

http://www.atmos-meas-tech.net/7/1701/2014/amt-7-1701-2014.pdf

The best possible option for you is to derive mixing layer height from the radiosonde profile information. Following is a useful reference:

http://www.atmos-meas-tech.net/7/1701/2014/amt-7-1701-2014.pdf

You can download the radiosonde profiles data sets for various stations at the following link: (For New Delhi, the station number is 42182)

http://weather.uwyo.edu/upperair/sounding.html

Note that there are various other methods, but the data sets are limited. 

http://weather.uwyo.edu/upperair/sounding.html

http://www.atmos-meas-tech.net/7/1701/2014/amt-7-1701-2014.pdf

 Thanks Dr Lakshmi, this would be a great help.

If not cities exactly, you can also download it over a grid of desired size encompassing the city required. You can get this from MACC Reanalysis data website.

http://apps.ecmwf.int/datasets/data/macc-reanalysis/

Hope it helps!

 Dear Parth, thanks for providing the link, this would be really helpful.