Mapping Statistical Characteristics of Frosts in Iran

Abstract

ABSTRACT:To model and map the statistical characteristics of frost in Iran, the data related to the minimum daily temperature for a 15-year period (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) was obtained from Iran Meteorological Organization. Then using multivariate regression models, the relationship among five statistical characteristics, i.e. the mean Julian day of the first frost, mean Julian day of the last frost, mean number of frost days per year, mean length of the frost period and mean length of growing season were modeled by three geoclimate factors: elevation, longitude and latitude. The precision of each model was explored using four hypotheses: linearity of the relationship between independent variables and the dependent variable, normality of errors, constancy of error variance and lake of correlation of errors were tested, and their precisions were confirmed. At the second stage, contour lines resulting from STRM were converted to the point features class. Altogether, 661'474 points were gathered from all over Iran. Then, the studied five frost characteristics were generalized to 661'474 points; then, the regionalization maps of statistical characteristics of frost were obtained for Iran using Kriging interpolation method. The results showed that the temperature of highland areas above 4'200 m above sea level always was at least zero and below zero during the year, and also the coastal strip of southern Iran had no frost. Elevation was the most effective factor in the spatial arrangement for the frequency of occurrence of Julian day of the first frost. The most effective factors in spatial arrangement for the frequency of occurrence of Julian day of the last frost, length of frost period and length of growing season were elevation and latitude. Finally, spatial arrangement for the frequency of occurrence of the frost days was also a function of three factors of elevation, longitude and latitude. The dominant role of elevation in spatial arrangement for the occurrence of the first frost day in Iran showed that the occurrence of the first frost day in Iran could be of the type of radiation frosts and the dominant role of elevation and latitude demonstrated that late-winter frosts can be mostly of the type of advection frosts. Therefore, arrangement of statistical features of frost in Iran is both a function of geo -climate factors and the synoptic systems which have entered the country.

A study of frost occurrence and minimum temperatures in Iran

“…This is directly related to elevation and location of these stations, their situation in the position of external synoptic systems, physical and geomorphological functions and local weather. Mahmoudi (2014) showed that temperatures over highland areas which reach up to 4200 m above the sea level were always greater than 0 • C or below 0 • C at some point of the year and, additionally, the coastal zone of southern Iran had no frost. Elevation becomes the main factor for the frequency of frost incidence.…”

“…The results showed that the earliest autumn frost and the latest spring frost occur in the Taftan Mountains, and the latest autumn frost and the earliest spring frost occur within the western and southeastern regions. Mahmoudi (2014) examined the use of multivariate regression trends, modelled the relationship among five statistical characteristics (i.e., the mean Julian day of the first frost, mean Julian day of the last frost, suggested range of frost days each year, the duration of the frost period and the average period of the growing season by way of three geo-climate elements: elevation, longitude and latitude). The results showed that the temperature of the highland regions which reached up to 4200 m above sea level was usually 0 • C and colder throughout the year, and additionally, the coastal strip of southern Iran had no frost.…”

Change and attribution of frost days and frost‐free periods in China

“…The spatial distribution of frost events is influenced by a range of factors. Typically, locations situated at higher latitudes and altitudes are more susceptible to experiencing more frequent frost events compared to those situated at lower latitudes and altitudes (Kalma et al, 1992; Mahmoudi, 2014). Moreover, the climatic conditions, such as temperature, precipitation, atmospheric circulation, and other factors, significantly affect the frequency and duration of FDs and FFPs (Seok et al, 2017).…”

“…Changes in frost events are influenced by a multitude of factors, including geographical position, atmospheric circulation patterns and meteorological variables such as air temperature, humidity, wind and cloud cover (Kalma et al, 1992; Mahmoudi, 2014; Masaki, 2022; Seok et al, 2017; Shen et al, 2014). In the absence of warming, theoretical frameworks and empirical studies associate anomalous frost timing with atmospheric circulation anomalies.…”