Geographical Research

The purpose of this study is estimate waiting time of frost occurrence over Iran. The daily data from 663 synoptic and climatology over Iran during 1/1/1340 to 11/10/1383 have been used. Data interpolated by Kriging method on 15×15 km pixels. The data base with dimension 15992×7187 obtained that on the rows were days and on the column were pixels. By t student test the interval mean of waiting time frost occurrence estimate for each pixels during different months and yearly in 95% confidence level. The results of this study showed that waiting time frost occurrence in the different months of year is not even over Iran country. In the January the waiting time frost occurrence is very short. In this month of year over the Zagros and elevation in the northeastern part of country waiting time frost occurrence is 1 to 3 days. In the other months waiting time frost occurrence increase. The southern parts of country in the all months of year are without frost occurrence. The changes of waiting time frost occurrence are very high in the regions that waiting time is long. Over the Ardabil، regions between Sanandaj and Hamedan، Tehran and Semnan and Shahrekord the time interval between two occurrence frost phenomena is very short rather than other parts of country.