Determination and Investigation of Dates of Beginning and End of Early and Late Freezes and Possibility of its Continuity, Intensity and Succession in Ardabil Province

Freeze is one of the serious climatic phenomena that influences different aspects of human life including agriculture, transportation and energy. Effects of freeze in agriculture section are more than other sections. Effects of freezes in agriculture section appeare more than its earliness or lateness aspects. In Ardabil Province, in most years, early and late freezes have caused serious damages to agricultural products. For example, in Farvardin 1393, gardens of Ardabil Province recompensed more than 4 billion Rials due to late spring cold. Due to this cold, 21000 Hectares of gardens of this province recompensed.
Of the causes of extensions of recompenses resulted from climatic phenomena like freezes is unknown remaining of dimensions and nature of this phenomenon. In occasions of occurrence of early and late freezes, to decrease recompenses resulting from it, it is needed to have a coherent management program; that to prepare this program, it is needed to know different aspects of this phenomenon. In this research, it is tried to determine beginning and end dates of early and late freezes and to investigate several cases of properties of these freezes along with its possibility.
Data used in this study is minimum temperature as daily in 15-year statistical period (from 1996 to 2010) in stations of Ardabil Province. After collecting and setting data, series of data were planed as Juliuseous date that first day-counting of data was considered October and beginning and end dates of freezes (lack of temperature to zero and under zero Centigrade) were analyzed. In this research, knowledge of possibilities and also an approach called Markov’s Chains were used.
Accordingly, continuity and possibility of occurrence of early and late freezes are considered in different continuities of, various intensities of early and late freezes and possibility of its occurrence and possibility of succession of different states freezes are investigated.
Analyzing beginning and end dates of occurrence of freezes shows that general trend of day-counting of beginning date of freezes in Parsabad Station is decreasing and moves toward hot season. In stations of Ardabil and Khalkhal, this trend is increading. In Khalkhal Station, beginning dates of freeze moves toward cold season with intensity of 1.07 day per year and has started later.
Investigating end dates of freezes according to regression analysis shows that general trend of day-counting of dates was decreasing by 0.517 day per year in Parsabad Station and was increasing by about 0.29 and 0.14 day per year in stations of Ardabil and Khalkhal, respectively.
Early freezes start in November in Parsabad Station and in October in stations of Ardabil and Khalkhal.
Continuity of early freezes in Parsabad Station in less than other stations so that in this station freezes have not lasted more than 2 days. In Khalkhal Station, continuity of freezes is more than other stations so that in Khalkhal Station continuity of freezes has been less.
In Parsabad Station, due to lower height temperature was higher than other stations and intensive freezes are not observed. In Khalkhal Station, number of freezes is more than other stations. In this station, 11 intensive freezes lower than -3 centigrade have occurred that there is 2.37 per cent of possibility of its occurrence in October.
The most important results resulting from above-mentioned topics are as follows: - Day-counting trend of beginning of early freezes is decreasing in Parsabad Station and is increasing in stations of Ardabil and Khalkhal. Day-counting trend of end of late freezes is decreasing.
- Early freezes begin in November in Parsabad Station and in October in stations of Ardabil and Khalkhal. Late freezes are in April in Parsabad Station and in May in stations of Ardabil and Khalkhal.
- Continuity of early freezes in Parsabad Station is less than other stations and in Khalkhal Station, continuity of freezes in more than other stations. In late freezes in Khalkhal Station, continuity of freezes has been less.
- In terms of intensity of freezes, early intensive freeze has not happened in Parsabad Station. In this area, due to low height, temperature is more than other stations and intense freezes are not observed. In Khalkhal Station, number of intensive freezes with possibility of occurrence of 2.37 per cent in October is more than other stations.
- In terms of succession of different states of freeze and without freeze, in early freezes there is the highest possibility of occurrence of freeze after freeze in Khalkhal Station with 63.31 per cent, and in late freezes in Ardabil Station, occurrence of freeze is with 61.54 per cent after the state of without freeze.