shideh shams; Mohammad Mousavi baygi
Abstract
Introduction: Air temperature as an important climatic factor can influence variability and distribution of other climatic parameters. Therefore, tracking the changes in air temperature is a popular procedure in climate change studies.. According to the national academy in the last decade, global temperature ...
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Introduction: Air temperature as an important climatic factor can influence variability and distribution of other climatic parameters. Therefore, tracking the changes in air temperature is a popular procedure in climate change studies.. According to the national academy in the last decade, global temperature has raised 0.4 to 0.8⁰C. Instrumental records show that, with the exception of 1998, the 10 warmest year (during the last 150 years), occurred since 2000, and 2014 was the warmest year. Investigation of maximum and minimum air temperature temporal trend indicates that these two parameters behave differently over time. It has been shown that the minimum air temperature raises noticeably more than the maximum air temperature, which causes a reduction in the difference of maximum and minimum daily air temperature (daily temperature range, DTR). There are several factors that have an influence on reducing DTR such as: Urban development, farms’ irrigation and desertification. It has been shown that DTR reduction occurs mostly during winter and is less frequent during summer, which shows the season’s effect on the temperature trend. Considering the significant effects of the climatological factors on economic and agricultural management issues, the aim of this study is to investigate daily air temperature range for yearly, seasonal and monthly time scales, using available statistical methods.
Materials and Methods: Daily maximum and minimum air temperature records (from 1950 to 2010) were obtained from Mashhad Meteorological Organization. In order to control the quality of daily Tmax and Tmin data, four different types of quality controls were applied. First of all, gross errors were checked. In this step maximum and minimum air temperature data exceeding unlikely air temperature values, were eliminated from data series. Second, data tolerance was checked by searching for periods longer than a certain number of consecutive days with exactly the same temperatures. Third, a revision of internal consistence was done, verifying that daily Tmax always exceeds daily Tmin. Fourth, the temporal coherency was tested by checking if consecutive temperature records differ by more than 8 degrees. The homogeneity of the series was tested by means of the Standard Normal Homogeneity test, the Buishand range and the Pettitt tests, on yearly, seasonal and monthly time scales. Breakpoint can be detected by means of these methods. In addition, Von Neumann ratio test was used to explore the series’ randomness. Having investigated data’s randomness in this study, series’ trend was determined by the Kendal-Tau test. Furthermore, the slope of the series’ trend was calculated using the Sen’s slope method.
Results Discussion: Results indicated a decreasing trend in DTR during last 60 years (1951-2010) in Mashhad climatological station. Moreover, the results revealed that the slope of yearly DTR was decreasing (-0.029 ⁰C per year), which indicates that minimum air temperature values raise more maximum air temperature values. A breakpoint was detected during 1985. During 1951-1985, the average amount of DTR was 14.6⁰C, while this parameter reduced to 12.9⁰C for the period 1985-2010. The Kendall-Tau test was used to obtain the significance of trend during 1951-2010, 1951-1985 and 1985-2010. The results showed that during 1951-2010, DTR significantly reduced at a rate of 0.29oC per decade. However, between 1951 and 1985, DTR trend increased at a rate of 0.61oC per decade, while DTR trend between 1985 and 2010 reduced at a rate of 0.19 ⁰C per decade, which was not significant (P-value=5%). In the seasonal DTR series, the highest trend’s slope was calculated for the summer data (-0.43 ⁰C in a decade), while the lowest one accrued in spring (-0.15⁰C in a decade). From 1951 to 1985, DTR had an increasing trend, due to minimum air temperature’s downward trend. But from the late 1980 to 2010, as it was expected, downward DTR trend was observed, because during this period minimum air temperature increases more than the maximum air temperature, thus the difference between Tmax and Tmin was reduced. Monthly DTR analysis also revealed a decreasing trend from 1951 to 2010, except for March and April, which had a non-significant increasing trend. In monthly DTR series, as it was expected, similar to the yearly and seasonal time series, the breakpoints accrued around 1985 in 8 out of 12 months. During February, March, April and November no significant breakpoint was detected.
Conclusion: DTR decreasing trend indicated that minimum air temperature increase was greater than maximum. This can cause a significant effect on the agricultural sector, hence in an appropriate agricultural management, these points should be considered. For example, changing the sowing time is one of the decisions which a manager can make.
Sh. Shams; Mohammad Mousavi baygi
Abstract
Mashhad is Iran second most populous city, where in terms of tourism, economy and agriculture is very important. Regarding to the importance of the change of climatic factors and its effect on future policy, in this study the max and minimum temperature changes in the scale of yearly, seasonally, monthly ...
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Mashhad is Iran second most populous city, where in terms of tourism, economy and agriculture is very important. Regarding to the importance of the change of climatic factors and its effect on future policy, in this study the max and minimum temperature changes in the scale of yearly, seasonally, monthly and daily, was investigated by means of SNHT, Buishand, Pettitt, Von-neumann and kendall-tau. The results of this study indicate a temperature increase of Mashhad, comparison of the results showed that during the past 60 years (1951-2010), minimum temperature increased 2times more than maximum temperature (0.062 versus 0.031). Test results also showed temperature increasing in all seasons, but just winter maximum temperature increasing trend was not significant in 95% confidence level. Also the highest rate of temperature increasing was belonged to autumn minimum temperature, with the slope of 0.074. Like the difference between annual series, in all season minimum temperature increasing trend is higher than maximum trend, comparing trends in monthly maximum and minimum temperatures show similar results. It also was shown that the minimum temperature trend rose approximately near the year 1985, while maximum temperature break point is near 1995.
T. Honar; A. Sabet Sarvestani; A.A. Kamgar Haghighi; Sh. Shams
Abstract
Abstract
The propose of this study was evaluation of CropSyst Model on growth simulation and yield stimation of canola under different irrigation treatments. Canola (Talaye) was sown under 5 treatment and 4 replicants in completed randomized block designs at the college of Agriculture, Shiraz Universityduring ...
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Abstract
The propose of this study was evaluation of CropSyst Model on growth simulation and yield stimation of canola under different irrigation treatments. Canola (Talaye) was sown under 5 treatment and 4 replicants in completed randomized block designs at the college of Agriculture, Shiraz Universityduring 2007-2008. During the growth season dry mass and LAI was meseaured frequently, then model was calibrated by the resukts. Obtained results showed very good esyimation by the simulation model, as the correlation coefficient square between dry mass and LAI in defferent treatments were more than 0.99 and 0.95, respectively. Also correlation coeficient between meseaured and simulated crop yeild was 0.96, that shows the accuracy of model in simulation on crop parameter. Also the model was valuated by independent data. Obtained results showed the accuracy of model simulation in dry matter as the correlation cofficient was achieved 0.9. Also LAI simulation in all treatments had good reults, as generaly is reliable in canola investigations.
Keywords: Simiulatinng models, Alfalfa, Leaf area index
