S Tajbakhsh - I.R.of Iran Meteorological Organization,Tehran,Iran
P Ghaffarian - I.R.of Iran Meteorological Organization,Tehran,Iran
J.B Jamali - Atmospheric Science and Meteorological Research Center (ASMERC), Tehran, Iran

In this paper air craft icing has been simulated using regional NWP (MM5) outputs in an atmospheric system which passed over Tehran-Mehrabad Airport on 6th of January 2008. It is attempted to estimate the threshold values of some MM5 outputs which are important in icing, such as vertical velocity, relative humidity and liquid water content and compare with the values of other studies