Chilling accumulation pattern analysis of Iran cold regions based on CH models،Utah،CP

The accumulation of chilling during the dormancy period for fruit trees is very important. Failure to chilling requirement will reduce performance and waste of resources. Successful cultivation of horticultural products depends on suitable climatic conditions. Dormancy is considered one of the most important stages in the life cycle of temperate plants. Horticulture and fruit production are one of the most important parts of the country. The bulk of the country's exports are covered with arid and frosty crops. Providing winter chilling to the temperate regions is critical to the lack of attention to this, causing the loss of capital and resources. Measuring different areas through weather stations is an effective step in understanding the climate potential of each area to understand the accumulation of cold. Considering the trend of global warming and climate change, today, the assessment of global warming has been the focus of global studies. The study indicated that a comprehensive study with more stations and long-period hourly data on cold accumulation and calibration of different estimator models was not carried out. Therefore, the present study aims to analyze the winter cold accumulation of cold regions of Iran based on CH, Utah and CP models using statistics. The long-term temperature of three hours of observation of meteorological stations has been designed and carried out.
Methods and Matrial: In this study, the weather temperature data during the recession period was extracted from the Iranian Meteorological Organization (IMO( from 1985 to 2013. The 9744000 hour temperature record for the three different models of estimation of cold accumulation during the dormancy period was set up from November to March. For each model, 3258000 data is provided for the hourly temperature to determine the time series of the accumulation of cold. In order to estimate the accumulation of cold in the country through the meteorological stations studied, three common models of estimation of cold accumulation, chilling hours (CH), Utah units and dynamic model (CP) were used. The non-parametric Mann-Kendall method was used to process the time series changes and the validation criteria were used to calibrate different models performance of accumulation of chilling. Linear interpolation was used to convert the temperature of three hours to the hourly temperature. In this method, the temperature is collected three hours later, at a temperature of three hours, and added to the previous temperature by three-hour intervals. It should be noted that this method is used independently for each three hour period of air temperature based on the temperature before and after it. Operation of this method is provided in the Excel software programming environment for each station and each year from November to March. In order to validate different models of need for cold, MAE, MBE and RMSE validation criteria were used to determine the performancr models of chilling accumulation.

The output of different models showed that the pattern of the accumulation of cold influenced from the height of each region. In all models of higher stations they still have the necessary accumulation of chill. Typically, Yasuj station with a lower latitude has the higher accumulation of chiiling in the doamancr period. The structure of each model is different for quantifying the chilling requirement fruit trees. In the chilling hours model, temperatures above zero to 7.2 are more likely to play a role in the Utah model, because temperatures above 7 to 10 are also chilling effect, so the data obtained in Utah model are higher, which can not be a strong reason for this superiority model. Therefore, it is better to match the different species of chilling requirement trees with the potential of climate and the accumulation of high-temperature multiplier for each region.
The coefficient of variation in the accumulation of cold in the model of CH is higher at higher station with higher chilling. Based on the Utah model, this coefficient of variation is observed in the stations, Ghouchan, Golmakan, Mashhad and Torbat Heydarieh, and in the dynamic model at Tabriz, Sarab and Fasa stations. Estimating hourly temperatures over a long period of data based on different models shows that the highest rate of high accumulation at the beginning of the statistical period has been studied and occurred over the past decades. In fact, cold and relatively cold winters in the past have been more capable of providing more power to accumulate cold over the past decades. In the last two decades, the decrease in peak cloud accumulation has become apparent. The results of stations in Ardebil, Mako, Meshkinshahr, Khoy and Sarab with hours of freezing between 1,000 and 1,200 hours indicate that being located in higher latitudes can not be a reason to provide the required capital for high-demand fruit trees such as late apple, because the Extreme temperature and lower than zero degrees in the accumulation of cold do not only play a role, but also have a negative effect. So the high latitude is not a strong reason to provide the cold caaumulation deciduous with high chilling requirement. The results of the validation tests indicate that the dynamic model, according to MAE and RMSE, has a higher performance among the models.

The evolution of the long-term temperature of the observed stations for the estimation of the accumulation of cold showed that, Based on the model of cold chilling hours (CH), the accumulation of cold from 775 to 1445 hours, Based on Utah's model, the accumulation of heat from 1191 to 2121 units of heat Based on the Dynamic Model (CP), the accumulation of cold temperatures varies between 63 and 96 portions in cold and temperate regions of Iran The elevation factor of the sea level plays an important role in estimating the accumulation of cold in each of the models. In terms of time variation according to the long-term time series, the frequency of peak accumulation in the past decades has been more than recent decades. In fact, the cold season in the past has been more than a decade of cooling power. The trend of cold storm changes based on non-parametric Mann-Kendall test showed that there were significant changes in significant changes in the stations at Isfahan and Shahrekord stations at a significant level of 0.05. Although there was no significant trend at most stations, the trend slope of the trend line at most stations is important. These conditions can be attributed to the effects of global warming through mild winters in recent decades. The results of the validation criteria of the models for estimating cold accumulation showed that the dynamic model with less error rate in the prediction of cold accumulation has a higher performance than other models. The results of this research are important in providing a comprehensive and initial model of cold accumulation in temperate and cold regions of the Iran in order to adapt the varieties consistent with the climate potential and the pattern of the accumulation of cold in each region.