The performance of broiler chickens is directly influenced by temperature changes and the occurrence of heat stress, whether it is cold or hot. The present study aims to assess the cooling and heating degree days in different stages of broiler chicken production in Khorasan Razavi province. To achieve this objective, daily average temperature data were collected from 13 synoptic stations during the statistical period of 1988-2018. Cooling and heating degree days were calculated for each week of production using specific thresholds, and their spatial distribution was analyzed. Furthermore, the relationship between cooling and heating degree days and geographical features was evaluated. The findings indicate a decrease in cooling degree days and an increase in heating degree days as latitude increases. The northern and western regions of the province exhibited a greater need for heating throughout all stages of broiler chicken production, whereas the eastern and southern regions had higher cooling requirements at different production stages. Overall, the northeastern, southern, and western marginal areas of the province, including Khaf, Gonabad, Kashmar, Sarakhs, and Sabzevar, exhibited the lowest cooling and heating needs during the 6-week period of broiler chicken production, making them suitable climates for this economic activity.

The velation between crop yield and air temperature during growth stage, can be evaluated in different ways. Growth and development rate, dry mather production, quality and quantity of yield are the important factors for screening genotypes of plant species like wheat and rapeseed that grown in cold region of Iran as a winter crops. It is a long time that means of delay temperature and physiological base temperature (GDD) used for determine of interaction effects between environmental temperature and crop yields in the several of studies. This study to have an intention use the other temperature index for screening of winter rappelled varieties under different cold temperature under the technical term Chilling degree-days (CDD). The sum of minimum daily temperature below zero during the rosette stage of rapeseeds at four cold region of Iran (karaj, zanjan, hamedan and shahre-kord) is a criterion for quantified of cold temperature days, cold acclimation of winter rapeseeds and Growth and development rate, dry matter productions, quality and quantity of yield.

Introduction: One of the practical indices in determining required energy for providing climatic comfort is the degree day index.The total mean deviation of daily temperature of human comfort temperature (threshold temperature) is called degree day temperature that provides many applications in estimating required energy in cooling and heating section. It is notable that various studies around the world have used different temperatures to calculate HDD and CDD considering their climatic and geographical location. In Iran, 18 degrees centigrade is used for HDD and 24 degrees centigrade for CDD calculation, while climatic and geographical diversity of Iran causes new base temperatures to be recommended for HDD and CDD calculations. The present study plans to present a proper base temperature for calculating HDD and CDD with regard to specific characteristics of each city's climate.....

With the proliferation of regional climate simulation software, it is possible to simulate various scenarios such as the impact of filling a lake with water or drying of water of a lake and its impact on the climate surrounding area, in the computer virtual world. This lake, as one of the major lakes in the North West of the country, sometimes in periods of drought, is facing the threat of loss of water. This factor can be effective on climate components of the surrounding areas including HDD and CDD indices changes as components for energy supply and demand. Therefore, in this study, using the software TAPM, two scenarios of a Lake full of water (the real condition of the lake) and drying lake were done to simulate the HDD and CDD indices changes for town of Marivan, which is located in the vicinity of the lake. But before that, on the basis of actual and daily data of minimum and maximum temperatures for 1990 to 2010, the HDD and CDD was calculated for Marivan. According to the long-term observations, it was determined that there is a significant process only for the HDD and CDD index for March. These changes, respectively for the HDD and CDD indices, with statistics (R =-0. 54; t =-2. 20) and (t = 0. 38; R = 0. 41) confirm reducing the need for heating energy and increased demand for cooling energy in this month. Also, the outputs show that, in the scenario of dry lake, the HDD has increased in most cold months compared with a lake filled with water, and on the other hand, the CDD also show an increase in warm months. On the other hand, based on an annual average, the findings showed that drying lake will reduce 30-degree day calorie of energy demand for heating and increase 111 degree-days calorie of energy demand for cooling.

Evaluating the susceptibility of regional climates to climate change provides a framework for realistically analyzing potential future climate changes. This paper investigates the impact of human activities on variations in extreme precipitation in Iran by evaluating data provided from 286 rain-gauge stations during 1967-2010 and general circulation simulation results of the CanESM2 model. This investigation was based on six forcing factors, including natural external factors (volcanic aerosols, solar radiation), anthropogenic and a combination of them, Green House Gases (GHGs), changes in land use, and anthropogenic aerosols. Seven precipitation indices, namely Rx1day (annual maximum 1-day precipitation), Rx5day (annual maximum 5-day precipitation), R10mm (annual count of days with daily precipitation exceeding 10 mm), R20mm (annual count of days with daily precipitation exceeding 20 mm), CDD (consecutive dry days), CWD (consecutive wet days), and PRCPTOT (annual total wet day precipitation), have been analyzed via the optimal fingerprint method. The results revealed that Rx1day, Rx5day and CWD increased, while R10mm, R20mm, CDD, and PRCPTOT decreased among which CDD and Rx1day indices showed significant variations, with values of 18.4% and 10.9%, respectively. Furthermore, the obtained results implied that only the impact of anthropogenic forcing, with a value of 1.4, was detected and attributed to variations in CDD. Additionally, anthropogenic forcing caused an increase in the return period of a 20-year event by 1.9 years for CDD. Although human-induced forcing factors presented marked trends in some cases, their effects were not generally detected and attributed to the change in the observations, apart from one exception.

Estimation of energy needed for heating or cooling buildings during cold or warm season, is one of the most important parameters in architectural designs. This energy is a function of climatic values named heating (HDD) or cooling (CDD) degree-days .In this study, as a first step, a computational model is developed which calculates daily values of HDD and CDD based on mean monthly air temperatures, for a network of 218 stations .In the second step, the spatial distribution of HDD and CDD was analyzed by multiple regression method. Based on the equations obtained, the HDD and CDD at each point of country could be estimated. In the next step, considering some thresholds for HDD, the 7 climatic groups from H1 (Mild) to H7 (Extra cold), were identified. With similar method the regions were divided into 5 groups as function of their cooling degree-days need, from C1(mild) to c5 very warm . In addition, four humidity groups were added to the classification system. As a result the proposed classification, was defined by general formula of HiCjRk where i, j and k (only for costal zones) vary from 1 to 7, 1 to 5 and 1 to 4, respectively. Finally, based on criteria of classification, the climatic classification map of Iran with the 1:1000000 scales at GIS media was provided.