Variation Of Growing Season Length (GSL) Over Second Half Of 20th In Irna
2007
Sedaghat Kerdar, A., Atmospheric Science and Meteorological Research Center (ASMERC), Iran | Rahimzadeh, F., Atmospheric Science and Meteorological Research Center (ASMERC), Iran
The variation of the growing season length during the last decades is one of the important impacts of global warming. It has been intensified by occurrence of early Spring and late Autumn freezing. The length of growing season has been increased in mid and higher latitudes of the northern hemisphere in association with the global warming. For this purpose, there are varieties of indices, but it is necessary to introduce a plant-free definition for applications, such as climate models and it's changes for interpretation of global warming, appropriate description of forest and farm land. One of the definition is growing season length (GSL) indices was defined by commission for climatology\\ climate variability(CLIVAR). It is found by counting the number of days between first span of at least 6 days with daily mean temperature greater than 5°c after July 1st (Jan 1st in southern hemisphere) and first span of 6 days with daily mean temperature less than 5°. igh quality and homogenous daily temperature data sets from 16 Iranian synoptic stations for period of 1951-2003 were used for the study of variation of GSL accompanied by number of frost days and icing days. It was found that these indices are not appropriate for stations like Bushehr and Abadan where located in southern part of the country. It was determined that there are positive trends for GSL in most of the stations where located in the central and northern parts of the country. The highest values of these trends, 7 to 12 days per decades belongs to Kermanshah, Mashhad and Tehran respectively. The number of frost days has decreased in most of the stations too.
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