Rainfall variable fluctuate in space and time. To make rainfall model for one rgion you must to take in considerationj tha the rainfall amount and distribution are affected by many factors including geographical, such as longitude, latitude, altitude; distance from sea; seasonality, like air humidity movement, temperature, atmospheric pressure and topography.

Dear Sandun Dassanayake,

There are some reliable sources (link given below) which you can refer.

http://journals.ametsoc.org/doi/pdf/10.1175/JAMC-D-13-082.1

http://www.gfdl.noaa.gov/bibliography/related_files/jjp1001.pdf

https://ncas.ac.uk/index.php/en/all-docman-documents/individual-science-highlights/climate/1112-science-highlights-stephanie-johnson/file

http://onlinelibrary.wiley.com/doi/10.1029/2005GL023350/epdf

http://www.nature.com/nature/journal/v489/n7415/pdf/nature11390.pdf

http://www.nature.com/nature/journal/v509/n7499/pdf/nature13260.pdf

I hope these will be very helpful to you.

All the best !

You may want to use some of the major satellite-measured (and bias corrected with ground measurement) precipitation dataset such as TRMM V7 and GSMaP_Gauge.

These products cover global sub-daily rainfall nearly 20 years (10-30km resolution). 

http://sharaku.eorc.jaxa.jp/GSMaP/

Dear Sandun,

You may have two main sources of Meteorological data. The first is ground based meteorological recording stations which might be owned by national meteorological  authority of your country. Second sources Satellite meteorology such as NASA's GPM-Precipitation Measurement Missions and TRMM-The Tropical Rainfall Measuring Mission, a joint mission of NASA and the Japan Aerospace Exploration Agency, they provide ground validated data. Follow the links below to fetch data of your interest.

https://pmm.nasa.gov/data-access/downloads/trmm

https://pmm.nasa.gov/index.php?q=data-access/downloads/gpm

dear all,

thank you very much, highly appreciate your comments on this. 

If you have observed time-series, you can simulate longer periods by using a resampling strategy. This one allows preserving complex rainfall characteristics found in tropical climates:

https://doi.org/10.5194/hess-18-3015-2014

Here you find a tutorial to use the same technique with a free software:

https://bitbucket.org/orianif/g2s_time_series_tutorial/src/master/

Hope it helps,

Fabio