Have you got any wind data for building air mass backward trajectories for a month?
As I understand, you should obtain zonal and meridional wind components (analysis grid data or model forecast grid data) for that.
If you want, I can provide you some papers about constructing trajectories. Then you should find my answer for a certain RG member's question. The link is given below. I had attached many papers to my archived answer which was among the first ten answers (page number 1 of the answers).
I think I can give you some advices if you provide more detailed information. If you are not familiar with trajectories at all, I could help you in constructing some simple sequence of numerical calculations. Feel free to ask additional questions.
HYSPLIT gives you a plot over a map of the trajectory. If you use HYSPLIT from the NOAA website, you can produce a KMZ file that can be plotted with Google Earth. MATLAB can do it if you have the mapping toolbox.
from hysplit you can save endpoints files in ascii format corresponding different days of the month. you can use idl or matlab to plot them. I can give my idl code used in this paper if you need.
Ojha, N., M. Naja, K. P. Singh, T. Sarangi, R. Kumar, S. Lal, M. G. Lawrence, T. M. Butler, and H. C. Chandola (2012), Variabilities in ozone at a semi-urban site in the Indo-Gangetic Plain region: Association with the meteorology and regional processes, J. Geophys. Res., 117, D20301, doi:10.1029/2012JD017716.
I suggest you to have a look at the openair library for R http://www.openair-project.org/PDF/OpenAir_Manual.pdf There are several ways of plotting backtrajectories. You can even cluster the trajectories. Regards.
You can follow the answers given by Prof. Hopke, Dr. Firoz Khan and Dr.Narendra Ojha. I would also like to add one more option that you may use is the Origin Pro software, it is very easy to plot them in Origin Pro. Back trajectories can even be plotted using MS Excel, however excel will take much time in comparison to IDL, MATLAB or Origin. In case of any problem you can write to me at [email protected]