بررسي رابطه زمان و وقوع سالانه در كاهش طول دوره رشد محصولات كشاورزي اردبيل

The Survey of Relation of Annually Freezing Period in Decreasing the Duration of Agricultural Crop Growth Period of Ardebil

The main objective of this article is studying the freezing phenomenon and its influence on Ardebil township agricultural crop production. Minimum daily temperature data of the Ardebil Meteorology Station (from 1977 up 1998) were used and different statistical methods were applied. Results indicate that the period of freezing tend to untimely fall freezing (towards beginning of fall) and late spring freezing (from beginning of spring to middle of it) and the duration of growth season in often selected years is more than its mean. The coefficient of weak correlation was set up and the untimely and late freezing did not have remarkable influence. The regression coefficient proved that dates of freezing and duration of growth seasons had gradually changes and oscillation. In return for each increasing unit in time unit (year), so that the process line of spring freezing tended to middle of spring and the fall freezing from beginning of fall tended to middle of it and consequently duration of growth season had decreased. The mean of happening time was not fixed, but difference in some days toward its mean had changes and oscillation from year to year.