The assessment of change Trend in Agro Climatological parameters that influence the growth of citrus Case study: Northern parts of Iran

The main aim of this research is the assessment of change trend in agro climatological parameters that influence the growth of citrus in the north of Iran. Thereby the daily data of min and max temperature, sunshine and precipitation for 6 number stations of the area under study provided from Iranian meteorological organization. At the next stage, the other parameters including temperature range, mean temperature, Growing Degree Day (GDD), Heliothermal Units (HTU) and Photothermal Units (PTU) has been calculated in the monthly, seasonal and annually scales. Then, Man Kendal trend test and linear method have been used for trend analysis in the above mentioned scales. The results of this research show the significant positive trend in min, max and mean temperature, GDD, HTU and PTU. The temperature range had significant negative trend. Precipitation has positive trend in 5% level of significant in a few stations in the monthly scale and it hasnt significant trend in the seasonal and annually scales. If the variables such as minimum temperature, max temperature, mean temperature, Heliothermal Units, Photothermal Units and temperature difference continue theirs increased and decreased rations respectively, would have harmful effect in the Citrus growth.