Determining the Calendar of Frost on the basis of Probability of Occurrence (Case Study: Ardabil Province)
Subject Areas : environmental management
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Abstract :
Background and Purpose: Since frost hazard can affect the human life, construction activities, agriculture and energy consumption and its distribution, being aware of the time of occurrence of frost can help in managing this hazard. In the present research, for the first time, effective parameters on frost separating advection or radiation types and return periods with probability of occurrence are calculated. Data and Methodology: In this research, using synoptic stations minimum temperatures in Ardabil province, dates of frost for the first time in the fall and last time in spring extracted and frosts were separated by their types (Radiation or Advection). Principal Component Analysis (PCA) was implemented on all meteorological variables in frosty days for each station. Time series of beginning and end of radiation and advection frosts using statistical distributions were analyzed and best fit distribution were selected and calculated in SMADA website. Findings: The highest and lowest frequency of frost days, respectively have happened in Khalkhal and Parsabad stations. Monthly frost analysis showed that the highest and lowest frequency of frost days respectively happened in January and October. The earliest date for the beginning of radiation frosts and advection frost (Khalkhal), respectively, have happened on September 19 and October 10 and latest date for the beginning (ParsAbad) respectively, happened on November 12 and December 12. Discussion and Conclusion: Generally, in Ardabil province 47% of frosts started with radiation frost and 53% started with advection frost which can increase the danger of frost in late summer crops. Products must be harvested before the cold air advection (5 October, based on the results of this study). 73% of frosts were terminated with radiation frosts and 27% were terminated with advection frosts which can be concluded in the spring time. It is possible to combat the radiation frosts and there is a significant reduction in losses. Based on the analysis of probability of frost occurrence, first radiation and advection frost in Ardabil with 90% probability, respectively, will occur at 18th and 23th of October. Advection frost date average of Ardabil station with a probability of 50% is 9th of November, in Pars-Abad, 1st of December, in Khalkhal, 26th of October and on 18th of November in Meshkin Shahr station.
