Hossein Mohammadi Hossein Mohammadi; Ghasem Azizi; Faramarz Khoshakhlagh; Mahdi Khazaei
Abstract
Abstract
Accurate and timely estimation of evapotranspiration has a significant and critical impact on the planning of water resources and agriculture. In this research, the estimation of evapotranspiration of sugarcane in Khuzestan province has been studied, and the data used, have been air temperature, ...
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Abstract
Accurate and timely estimation of evapotranspiration has a significant and critical impact on the planning of water resources and agriculture. In this research, the estimation of evapotranspiration of sugarcane in Khuzestan province has been studied, and the data used, have been air temperature, relative humidity, wind speed and sunny hours since the establishment of synoptic station until 2014. For this purpose, the evapotranspiration values of the reference plant were first calculated using the FAO Penman-Monteith standard method and then, using available plant coefficients, the amount of sugarcane evapotranspiration was estimated at different stages of growth. The results of this study show that the average sugarcane evapotranspiration in Khuzestan province has been 3.35 mm / day in June and in the early stages of growth, 10.46 mm/day in the middle stages of growth, and 6.26 mm / day in the final stages of growth. The value of this parameter in July was estimated 3.59 mm/day in the early stages, 11.23 mm/day in the middle stages and 6.74 mm/day in the final stages of growth. Finally, the amount of evapotranspiration of sugarcane in August was estimated 3.56 mm per day in the early stages of growth, 11.12 mm/day in the middle stages and 6.67mm per day in the final stages of the growth. The maximum daily and monthly evapotranspiration has occurred in July and the minimum in June. Also, the highest daily and monthly fluctuations of sugarcane evapotranspiration have occurred in the middle stages of growth and the lowest in the early stages of growth.
Hossein Mohammadi; Mohammad Hasan Mahoutchi; Mahdi Khazaei; Esmaeil Abbasi
Abstract
Probability analyses are useful methods for recognizing and predicting phenomena such as precipitation. One of these methods is the Markov chain. The Markov chain model is a special state of the models in which the current state of a system depends on its previous states. With this method, it is possible ...
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Probability analyses are useful methods for recognizing and predicting phenomena such as precipitation. One of these methods is the Markov chain. The Markov chain model is a special state of the models in which the current state of a system depends on its previous states. With this method, it is possible to calculate the probability of the occurrence andthe return period of climatic phenomena such as precipitation.Therefore, in the present research,using the 58 year daily precipitation data (1956 - 2013) ofShiraz synoptic station, the frequency and the continuity of rainy days in this city were studied by the use of the Markov chain model. The above statisticswere arranged based on the matrix of counting the changes of the occurrence states of the dry and wet days (days without precipitation and precipitation days), then, the situation change matrix was calculated based on the maximum likelihood estimation method. The matrix was evaluated and analyzed with repeated, constant power, and daily rainfall return period. Next, the return periods of 2 to 5 day rainfall days and the return period of1 day dry days, were also evaluated. Then,the return period of the continuation of 2 to 5 day precipitation days for twelve months of the year was calculated. The results showed that the probability of precipitation occurrence (wet days) per day was %0.1167 and the probability of no precipitation occurrence (drydays) was %0.8833. It was also determined that the most probable occurrence of rainy days was during the winter, especially in January and February. For example, the return period of 2 consecutive rainy days in January was estimated to be nearly 5 days. Therefore, it was observed that Shiraz precipitation has a heterogeneoustime distribution. In other words, precipitation is not uniform and concentrated in Shiraz.
Hasan Lashkari; Mahdi Khazaie
Volume 23, SEPEHR , July 2014, , Pages 70-79
Abstract
In order to investigate synoptic patterns of heavy precipitations in Sistan va Baluchestan province, 24 year (1987-2010) daily data of 6 synoptic stations was retrieved from meteorology organization. Moreover, data like sea level pressure, geo-potential elevation of 500 and 850 milibars were exploited ...
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In order to investigate synoptic patterns of heavy precipitations in Sistan va Baluchestan province, 24 year (1987-2010) daily data of 6 synoptic stations was retrieved from meteorology organization. Moreover, data like sea level pressure, geo-potential elevation of 500 and 850 milibars were exploited from NCAR/NCEP database and then required maps were prepared in Grads software. Generally, two patters have resulted in the heavy precipitations in this province.
In the first pattern which resulted in precipitations of December12, 1995, a cyclone with contour plot of 1017.5 and 1020 milibars crossed the Arabian Sea, 24 hours before the precipitation and caused humidity spreading toward the area. In 850 milibars, a cyclone above the country results in cold weather flow and a low pressure system with a 1500 geopotenial meter contour plot passed the Bangla Gulf and the Arabian Sea and supply the necessary humidity conditions for rising in this equilibrium level.
In the second pattern which resulted in precipitations of June 5, 2010, a large low pressure system is formed 24 hours before the precipitation over southern part of Asia, which also influence south eastern and southern parts of Iran. 24 hours before the precipitation, a low altitude center covers the area under study and supply humidity and instability. On the day of precipitations, study area in 850 and 500 milibars are affected by a trough of 1475 and 5850 geopotenial meter contour plot and results in precipitation of this pattern.
