S.M. Farmanara; B. Bakhtiari; N. Sayari
Abstract
Introduction: Drought is an extreme climate effect and a creeping phenomenon which directly affects the human life. A drought analysis usually requires characterizing drought severity, duration and frequency (SDF). These characteristic variables are commonly not independent, so this phenomenon is a complex ...
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Introduction: Drought is an extreme climate effect and a creeping phenomenon which directly affects the human life. A drought analysis usually requires characterizing drought severity, duration and frequency (SDF). These characteristic variables are commonly not independent, so this phenomenon is a complex natural disaster and climate change makes it likely to become more frequent and immense in many areas across the world. Therefore, in drought analysis, it is needed to investigate its multivariate nature and spatial variability clearly. Copula, as a model of multivariate distribution, has been used widely in hydrological studies. As the standardized precipitation index (SPI) is more accessible than other indices, it is the most commonly used indicators for analyzing the SDF of meteorological drought. Here, the study has two major focuses: 1) Fitting drought characteristics from SPI to appropriate copulas, then using fitted copulas to estimate conditional drought severity distribution and joint return periods for both historical and future time periods in Fars province. 2) Inquiring the effects of climate change on the frequency and severity of meteorological drought. Materials and Methods: Among the weather stations of Fars province, six synoptic stations were selected, which had longer historical data than others. The data used included 24-hour precipitation during 15 (2004-2018) to 33 (1986-2018) years. Three steps were carried out. Stage one: downscaling of outputs of the large scaling (CanESM2) based on two intermediate (RCP4.5) and pessimistic (RCP8.5) scenarios using SDSM, ver. 4.2.9 during the period of 2020 to 2050. Stage two: calculation of SPIand drought characteristics in the base and future periods (2050-2020). Stage three: extracting SDF curves for the base and future periods under RCP4.5 and RCP8.5 scenarios using copula. The SPIwas used to extract the drought duration and drought severity in the Fars province using GCM models under two selected scenarios (RCP4.5 and RCP8.5) from the IPCC Fifth Assessment Report (AR5) scenarios. The gamble copula function was used to construct the joint distribution function for evaluating the drought return periods in the study area. Because short-term drought prediction is more practical than long-term prediction, we used the 1-month SPI for the copulas-based analysis. Drought severity and duration were calculated based on computed SPIvalues by using the past available data. Drought duration is defined as successive months with SPIvalue less than -1 and drought severity as the accumulative SPIvalue during the period with successive SPIvalue less than -1. The normal and log-normal functions were selected as the candidate distribution function for drought duration and drought severity. Results and Discussion: The results showed that the frequency of drought occurrence in the Fars province will increase during the period of 2020-2050 under the both two scenarios. In the RCP8.5 scenario, the duration of the drought will also increase. The increase and decrease of monthly rainfall in RCP 4.5 and RCP 8.5 were 2.8 and 6.5%, respectively.The duration of the drought were obtained to be 5.25, 5.5 and 6 days at Shiraz station, with a 2 and 5 years return period, in the baseline and future periods under RCP4.5 and RCP8.5 scenarios, respectively. These values were estimated to be 4, 3.5 and 5 days at Bavanat Station.It is expected that the precipitation will decrease at Shiraz station under the two scenarios.Similarly, this amount is expected to increase and decrease at Bavanet station in the RCP4.5 and RCP8.5 scenarios, respectively. Conclusion: Changing droughts based on climate change is important in many aspects. In this study, the performance of two-variable statistical distribution of severity and duration of drought was investigated based on the copula function. The comparison of the drought period calculated using the SPIshowed that due to the climate change, the frequency of drought periods is expected to increase in the base and future periods. The results showed that the value of the precipitation changes in the RCP8.5 scenario is higher than the RCP4.5 scenario. Generally, the performance criteria showed that the SDSM had a good performance for the past and the future periods in Fars province for precipitation data. It is expected that with consideration of the amendments in the sixth report of the IPCC, more precision can be obtained in precipitation modeling. Therefore, reviewing the output of the SDF curves with the availability of the results of this report is suggested.
N. Sayari; A. Alizadeh; M. Bannayan Awal; A.R. Farid Hossaini; M.R. Hessami Kermani
Abstract
Abstract
The climate change was known to force local hydrology, through changes in the pattern of precipitation, temperature and the other hydrological variables. In this research, the impact of global warming on maximum and minimum temperature, precipitation and evapotranspiration (wheat, corn, tomato ...
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Abstract
The climate change was known to force local hydrology, through changes in the pattern of precipitation, temperature and the other hydrological variables. In this research, the impact of global warming on maximum and minimum temperature, precipitation and evapotranspiration (wheat, corn, tomato and sugar beet) of Kashafrood basin under two climate change scenarios (A2 and B2), and the output of two GCM models (HadCM3 and CGCM2) for three period of times (2010-2039, 2040-2069 and 2070-2099), were investigated. For evaluation two scenarios were downscaled into local level with Automated Statistical Downscaling (ASD) model. Precipitation was expected to decrease and/or increase, depends on applied GCM. The results indicated that the annual precipitation decreased for three periods under CGCM2 model and also for two scenarios (A2 and B2) as much as 13%-16% decreasing, the annual precipitation for three periods under HadCM3 model and two scenarios (A2 and B2) as much as 2%-8% increasing. The maximum and minimum temperatures in the Kashafrood basin was predicted, which increased by CGCM2 and HadCM3 models with two scenarios. Based on the HadCM3 model, maximum and minimum temperatures were expected to increase 2.4 0C to 5.8 0C and 0.6 0C to 3.8 0C, respectively; for 2070-2099 periods. For CGCM2 model, maximum and minimum temperatures were expected to increase 0.06 0C to 2.59 0C and 0.1 0C to 1.9 0C respectively; for 2070-2099. Evapotranspiration under A2 and B2 scenarios and HadCM3 model was increased but increasing in evapotranspiration with CGCM2 model under both scenarios was not significant in many cases. The comparison of two models and also two scenarios indicated that more critical status for A2 scenario by using two GCM models for this basin.
Keywords: Climate change, General circulation model, Downscaling, HadCM3, CGCM2, Kashaf rood basin, Evapotranspiration
A. Alizadeh; N. Sayari; M.R. Hessami Kermani; M. Bannayan Aval; A.R. Farid-Hosseini
Abstract
چکیده
تغییر اقلیم دارای اثرات مستقیمی بر فرآیندهای هیدرولوژیکی نظیر تبخیر از سطح آب، تعرق از گیاه، تغذیه آبهای زیرزمینی، رواناب یا ذوب برف دارد. در این مقاله اثرات احتمالی ...
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چکیده
تغییر اقلیم دارای اثرات مستقیمی بر فرآیندهای هیدرولوژیکی نظیر تبخیر از سطح آب، تعرق از گیاه، تغذیه آبهای زیرزمینی، رواناب یا ذوب برف دارد. در این مقاله اثرات احتمالی تغییراقلیم بر تبخیر و تعرق در آینده بررسی شده است. به همین دلیل تأثیر تغییراقلیم بر دما (حداقل، حداکثر و میانگین) و بارش تحت سناریوی A2 و برای سه دوره 2039-2010، 2069-2040 و 2099-2070 و با استفاده از ریزمقیاس نمایی آماری و خروجی های مدل گردش عمومی جو HadCM3 در حوضه کشف رود مورد بررسی قرار گرفت. در مرحله بعدی با استفاده از پارامترهای پیش بینی شده، تبخیر و تعرق گیاهان الگوی کشت این حوضه شامل گندم، چغندرقند، گوجه فرنگی، سیب و ذرت با استفاده از روش هارگریوز و سامانی محاسبه و برای دوره های مختلف مورد مقایسه قرار گرفتند. نتایج حاصل نشان داد که دما (حداقل، حداکثر و میانگین) در هر سه دوره پیش بینی نسبت به دوره پایه 1990-1961 افزایش خواهد یافت. میانگین سالانه بارش پیش بینی شده در دوره های مذکور تفاوت معنی داری نداشت ولی توزیع آن در فصلهای مختلف تغییر خواهد کرد. بدینصورت که مقدار بارش برای ماههای زمستان و تابستان کاهش و برای ماههای پائیز و بهار افزایش خواهد یافت. میزان تبخیر و تعرق محاسبه شده برای تمامی ماهها و برای تمامی دوره ها تحت تأثیر دما افزوده خواهد شد. نتایج نشان می دهد که در صورت افزایش دمای هوا به میزان 1، 2 و 4 درجه سانتی گراد نیاز آبی الگوی کشت گیاهان در دشت کشف رود به ترتیب 6، 10 و 16 درصد افزایش پیدا خواهد کرد.
واژه های کلیدی: مدلهای گردش عمومی جو، ریزمقیاس نمائی آماری، تبخیر وتعرق گیاه، حوضه کشف رود، تغییراقلیم
N. Sayari; M. Bannayan Aval; A. Alizadeh; M.B. Behiar
Abstract
Abstract
Accurate prediction of hourly minimum temperature is required for various crop models which simulate photosynthesis and transpiration. Such data can be used for crop protection and reducing the crops injuries due to freezing as well. Our objective of this study is employing trigonometric and ...
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Abstract
Accurate prediction of hourly minimum temperature is required for various crop models which simulate photosynthesis and transpiration. Such data can be used for crop protection and reducing the crops injuries due to freezing as well. Our objective of this study is employing trigonometric and pattern recognition (k-NN) approaches to evaluate their potential in prediction of hourly temperature for the whole 24 hours and also minimum temperature time occurrence. Our observed data contain every 3 hours minimum temperature data for 16 years of synoptic Mashhad climate station. Various scenarios were employed to predict the minimum temperature for first of Aban and first of Ordibehesht using, 1 day, 7 days, 110 days and 315 days observed data for next day minimum temperature prediction. Our results showed that if there is no full access or partly access to the minimum temperature data then the trigonometric function including Sine function is able to reproduce the required data. k-NN approach showed that as the distance of data to target data decreased the accuracy of prediction increased.
Keywords: Minimum temperature, Freezing, Sine model, Sine-Expo model, Prediction, Mashhad
K. Davary; S.H. Nemati; B. Ghahraman; N. Sayari; P. Shahinrokhsar
Abstract
This experiment was conducted at research greenhouse of college of agriculture, Ferdowsi University of Mashhad in 1381-1382. The experiment was designed based on the splitted plots in the form of completely randomized design and in four replications. Irrigation intervals were in three levels of 12, 4, ...
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This experiment was conducted at research greenhouse of college of agriculture, Ferdowsi University of Mashhad in 1381-1382. The experiment was designed based on the splitted plots in the form of completely randomized design and in four replications. Irrigation intervals were in three levels of 12, 4, and 2 times per day at primary plots, and three substrates of new perlite, used perlit, and rice bran at secondary plots. We used Paris Island as the lettuce seed. Wet weight, dry weight, and height were influenced from irrigation interval. Accordingly which 4- and 12-day irrigation intervals resulted in 466.39 and 386.94 g corresponding to highest and lowest dry weight, respectively and 12-day irrigation interval arose increase in lettuce height. Significant differences for wet and dry weights were found under different substrates. High wet and dry weights were due to used perlit and rice bran substrates, respectively. There were no significant interactions between irrigation interval and substrate on all of the growth properties of lettuce.
A. Alizadeh; N. Sayari; J. Ahmadian; A. Mohamadian
Abstract
Abstract
Saffron (Crocus sativus, L.) is one of the most important economical crops for Khorasan farmers. Almost all saffron yield in Iran comes from Khorasan provinces. First irrigation times is the crucial factors which affect the amount and quality of yield based upon an on farm investigation it ...
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Abstract
Saffron (Crocus sativus, L.) is one of the most important economical crops for Khorasan farmers. Almost all saffron yield in Iran comes from Khorasan provinces. First irrigation times is the crucial factors which affect the amount and quality of yield based upon an on farm investigation it was found that when air temperature reaches to 12 ۫c The most amount of flower is yielded. Also it was found that 2 to 3 weeks after irrigation flowering starts. The one irrigation should be applied in such a way that after this period of time saffron could be harvested. In this study the most appropriate date for the time of irrigation with 50, 75 and 95% probability was derived for different points of Khorasan provinces. Also Khorasan provinces were zoning for this purpose. Based on results, flowering date and first irrigation time for saffron are very different and depended on climate and temperature of studied zone. In the locations with higher elevation above the sea level and lower daily air mean temperature, usually flowering date and first irrigation time are very soon in the autumn early while decreasing of elevation above the sea level and increasing of daily air mean temperature, flowering date and first irrigation time are in the mid autumn or even autumn late.
Keywords: Saffron, Khorasan, temperature, flowering, first irrigation
