عنوان مقاله [English]
Humans and plants can grow in a certain temperature range and shall bear their ability against the high and low temperatures are limited. Decrease temperature of minimum thresholds of plants and occurrence of frost damage on roads every year the vast country's economy will enter. Study the tempo-spatial distribution of frost occurrence is the most fundamental climate research, which can planners to reduce cold and frost damage to guide and assist (Kamali, 151:2002).
Many studies in Iran and the world about this phenomenon have been done. The most important studies in other countries can be Suckling Studies (1988), in the southeastern United States, Watkins (1991) in the UK, Eriksson and Lindquist (2002) noted in Sweden.
The most important studies in Iran,
studies Alizadeh et al (1994) in Khorasan, Noohi (1374) in Karaj, Kamali (1995) in Tehran, Azizi and Nokhandan (2003) in Firoozkooh can be noted.
In this study the frost of Zanjan province, using statistical and probabilistic methods have been investigated. Results from analysis to different frost maps ware presented.
In this study, to assess the frost tempo-spatial distribution occurrence, indices: the beginning and end, frequency of occurrence, length of growing season and frost during the season based on Julian date used. Generally, statistical methods used in this study are as follows:
1-Some statistical distribution of the initial fitting to choose the best way to study how the distribution of data
2-Goodness of fit test for the detection of efficient test methods selected from the following:
- Chi-square test
B - Test Kolmogrov – Smirnoff
C - Correlation Analysis
3- The use of statistical distributions: normal and log normal distribution, uniform distribution
4- Zoning maps produced in the environment Arc / view model using the spline interpolation
According to the started frost map, as a core of frost Decrease around the Kheirabad station was observed and on average once every two years is likely that on days 22 and 24 October early autumn frost occurs. While the chance of frost around the Filehkaseh station, especially on 26 November is a once every two years. Range of difference between these two regions is 34 days which can be significant in terms of agriculture.
Probability distribution maps during the season and frost during the growing season are opposite each other, So that the probability map can be seen during the frost season, a marked increase in the core around the Kheirabad station during the frost season, almost equal to 200 days with a 50 percent chance once every two years there. A region to the north, during the season, less frost and especially around the filehkaseh, Khodabandeh and Khoramdeh stations and less than 150 days, and it also decreases. Therefore probability Range of during the season frost in parts of central and around the study area reaches up to 50 days. While the probability distribution maps during the growing season, a marked decrease the core around the Kheirabad station during the growing season with probability almost 170 days every two years once showed. Especially around the Filehkaseh station, this amount to 216 days, Khodabandeh and Khoramdeh station increases to 214 days. Thus, differences in occurrence during the growing season every two years in the central region and around the study area reach almost 56 days.
Overall results of this study include:
The results showed that in central and eastern stations that late spring frost occurrence in the end May also exist. The situation to the North-West Province has a reduction mode.
The results of calculations indicate increased probability distributions during the frost season in the East and Northern Regions has decreased.
Most Popular frost occurrence in Highlands Province, and lowest in parts of the province is low margin.