Assessing and Predicting the Temporal and Spatial Distribution of Beginning and Ending of Frost in the Northern Region of Iran

The aim of this study was to investigate temporal and spatial distribution of beginning and ending of frost at the base and future period in the northern region of the country. For this goal¡ the minimum temperature data of several synoptic stations in the study area including Bandar Anzali¡ Rasht¡ Gorgan¡ Ramsar¡ Nowshahr and Babolsar have been used. In this research¡ the period 1976-2005 and 2012-2039 is considered as the base and the future period¡ respectively. It is noted that the data of ECHO-G model have been used for determining of beginning and ending of frost in the daily scale. In this paper¡ we have used from ARC GIS software for mapping of beginning and ending of frost. The obtained results show that the beginning date of frost is a function of latitude and follow up of Eastward arrangement. In other words¡ with moving from West to East¡ beginning of frost comes sooner. The results suggest that future frost will start earlier and will end sooner. Namely¡ the beginning date of frost will move from early winter to late autumn. The results indicated that the beginning date of frost in the eastern region in the coming period (29 November) will occur about 10 days earlier than last period (19 November). This value is lower in the western regions and will reach from 12 January to 7 January in the coming period. In central and southern parts of the study area¡ the frost will occur seven days earlier and will be reached from 26 December to 19 December. The results also show that in most areas studied¡ ending date of frost will take place 0-23 days earlier than last year and in compared with the last period (7 March)¡ it will occur on 12 February. So¡ the growing season length in northern regions will increase in future periods. The maximum number of frost days associated with East coast and West coast has the lowest number of frost days. .