The Study of Effects of Climate Change on Length of Growing Season in Several Climatic Regions of Iran

In agricultural meteorology، the growing season is the period of each year when crops can be grown with the view of thermal condition. This period is generally between the first and last frost dates in autumn and spring in which temperature is above a specific threshold. There are two other definitions using a 50C threshold. One of the methods to study future climate is using the general circulation models (GCMs)، but these models have low temporal and spatial resolution and they can’t show local changes. In this study، statistical model LARS-WG has been used for downscaling GCMs outputs under A2 and B1 emission scenario conditions in several climatic regions of Iran during period of 1961-2004 for estimation of growing season length (GSL). The results showed that growing season with 00C threshold under the two scenarios will increase during 2020 to 2050 in Mashhad، Tehran and Rash stations and will decrease Kerman and Gorgan and Tabriz in comparison with their past climates. GSL with 50C threshold under two scenarios will increase in all stations except for Shiraz station. In general GSL for all three definitions under both scenarios would increase in Mashhad، Rasht and Tehran. In case of Esfahan، no significant trend was observed using 00C threshold and B1 scenario، and increasing trend for rest of the conditions.