assessment and mapping of early autumn, late spring and winter freezing in khorasan razavi province using gis

abstract plants growth and development and physiological activities occur in a certain air temperature range. spit of this fact that zero temperature named as a freezing temperature, in agriculture meteorology, freezing happen in lower temperature which is different for plants that lead to their tissues damage. early autumn freezing cause damage to harvesting of cotton and sugar beet and affect on time of wheat and barley planting in khrasan razavi. there are also many damages on agricultural products due to late spring freezing each year. this problem leads to loss the flowers during the trees flowering. in order to investing this phenomenon in khorasan razavi, the autumn, spring and winter freezing were considered based on suitable temperature threshold and the occurrence probability obtained and mapped. results show that early freezing in autumn begins from the north and then spread toward the southern regions. the late freezing in spring ends in the south sooner than other areas. results also show that the winter freezing more occurs in the north.