Climatology
Yagob Dinpashoh; Saeid Jahanbakhsh-Asl; Leyla Mosavi Jahani
Abstract
Introduction One of the standard models for estimation of ET0 that accepted by all hydrologists and climatologists is the FAO Penman-Monteith (FAO56PM) method. Although this model is accurate in ET0 estimation, however, it has some limitations. The main limitation of this method in in its need for various ...
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Introduction One of the standard models for estimation of ET0 that accepted by all hydrologists and climatologists is the FAO Penman-Monteith (FAO56PM) method. Although this model is accurate in ET0 estimation, however, it has some limitations. The main limitation of this method in in its need for various meteorological data, including the solar radiation, air temperature, relative humidity, dew point temperature, wind speed and actual vapor pressure. Unfortunately, all of these parameters are not readily available in all the conditions. In this regard, many researchers interested to find a simple method for accurate ET0 estimation (Sentelhas et al., 2010; Dinpashoh, 2016; and many others). Based on our best knowledge there is no comprehensive study conducted in Urmia Basin for finding a simple and accurate method that needs less weather parameters for ET0 estimation. Therefore, the main aim of this study is estimation of ET0 that needs less weather parameters in Urmia Lake basin. Materials and Methods The area under study is the Urmia Lake Basin, located in North-West of Iran. This basin is approximately lied between the 35⸰ 40´ E to 38⸰ 29´ E latitudes and 44⸰ 07´ to 47⸰ 53 longitudes. The area of this basin is about 51700 km2 which is equal to about 3.2 percent of Iran's area. Data used in this research are the daily recorded values of maximum air temperature, minimum air temperature, wind speed at 10 m height, relative humidity, sunshine duration, and some geographic information such as altitudes, latitudes and longitudes. The nine stations were selected from different points of the basin in this study. The FAO56PM method (Allen, 1998) was selected as the bench mark for ET0 estimation in all the stations. In this method the following equation was used for ET0 in the chosen sites. (1) where ET0 is the reference crop evapotranspiration (mm/day), Rn is the net solar radiation at crop surface (MJ m-2 day-1), G is the soil heat flux (MJ m-2 day-1), T is the mean air temperature at 2 m height (°C), u2 is the wind speed at a 2 m height (m/s), the term (es-ea) is the saturation vapor deficit (kPa), Δ is the slope of the vapor pressure curve at the point of air temperature (kPa/°C) and g is the psychometric constant (kPa/°C). In order to convert U from 10 m height to u2 the following equation was used (Nandagiri and Kovoor, 2005; Sentelhas et al., 2010; Dinpashoh et al., 2011): (2) where Uz is the wind speed (m/s) at z m height, and zw is the height (m) at which wind speed measured. In this study, in order to find an alternative model, which uses less weather data in estimation of ET0 the three empirical models namely Hargreaves (HG), Kimberly Penman (KPM), Priestly Taylor (PT), and Multivariate Linear and non-linear regression were used. Evaluation of the models performed using the three metrics, coefficient of determination (R2), Root Mean Square Error (RMSE), and Mean Absolute Error (MAE). Results and Discussion Results showed that, the median of the R2 values for KP was more than 0.986. The median of the R2 values for PT and HG models were found to be equal to 0.902 and 0.40, respectively. The median of RMSE for HG model was about 0.9 (mm day -1). This value for KPM and PT models were about 1.3 and 2.1 (mm day -1). The median of MAE for the selected stations for KPM was less than 1 (mm day -1). This value for HG was equal to 0.7 (mm day-1) and in the case of PT was more than 1.5 (mm day -1). Therefore, considering the MAE values and RMSE, the HG model was detected to be the suitable method foe ET0 estimation in Urmia Lake basin.
Climatology
Saeed jahanbakhsh; yagob din pazhoh; mohammad hossein aalinejhad
Volume 23, Issue 67 , April 2019, , Pages 91-107
Abstract
According to the importance of snowfall in supplying water of different regions especially mountainous areas, accurate estimation of snow water equvallent and changes of its coverage would be effective in agriculture, energy, management of reservoir and flood warnings. In this study runoff orginated ...
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According to the importance of snowfall in supplying water of different regions especially mountainous areas, accurate estimation of snow water equvallent and changes of its coverage would be effective in agriculture, energy, management of reservoir and flood warnings. In this study runoff orginated from snow melting in ShahrChay basin under the terms of climate change calculated. For this purpose, snow cover for water year of 2012-2013 were extracted in ENVI software by using daily images of Modis satellite.Then, GIS software the physiographic specification of the basin was obtained. In the next step, data of snow cover, meteorological variables and other necessary parameters to SRM model provided as an input of model and run_off from snow melt was simulated. Then output of the 6 models of atmospheric general circulation with title of 3 scenarios nomely A1B , A2 and B1 converted to a downscaleing by using LARS-WG model. By comparing the output of 6 models in the future period to period based on monthly statistical, the best model and scenario for generation of air temperature and precipitation data in the period 2030-2011 were selected. As a result the HADCM3 model under the scenario A1B was used for generation of precipitation and the MPEH5 under scenarios A2 was used for generation of temperature data. In order to estimate the rate of change of runoff orginated from snowmelt rate of change of monthly data of air temperature and precipitation of the base time period as well as future time period under selected model and scenarios was entered to SRM model in simulation time period. Results for all of the scenarios show that runoff orginated from snowmelt in late spring will be reduced. The peak flow appeared earlier in comparison with base time period and its value would be larger than base time period.
All other Geographic fields of studies , Interdisciplinary
yagob Dinpazhouh
Abstract
The aim of this study is trend analysis of streamflows of east Azerbaijan using the non-parametric methods. For this purpose the information of consentration of water quality ions (Ca, Mg, Cl, Na, HCo3, pH, So4, TDS, EC, SAR, Total Cations, Total Anions and Na%) of ten hydrometric stations (1983-2008) ...
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The aim of this study is trend analysis of streamflows of east Azerbaijan using the non-parametric methods. For this purpose the information of consentration of water quality ions (Ca, Mg, Cl, Na, HCo3, pH, So4, TDS, EC, SAR, Total Cations, Total Anions and Na%) of ten hydrometric stations (1983-2008) were used. To test trends the Mann-Kendal scheme after removing all significant autocorrelation effects from the data were used. To estimate trend line slope the non-parametric Sen´s estimator method was used. Results showed that trends of positive ions and EC were upward for most of the stations. Those stations which had negative trend in streamflow also exhibited positive trend in concentration of chemical elements of surface water. Furthermore, investigation of streamflow water quality using the Wilcox on method showed that the quality of water declined comparing the last decades. The reason of such declination attributed to the decreasing trend of streamflow and conveying pollutant materials into the rivers.
Climatology
Rasool Mirabbasi Najafabadi; yaghoob Dinpashoh
Volume 19, Issue 52 , June 2015, , Pages 277-301
Abstract
The aim of this study is the analysis of surface wind speed in monthly and annual times scales in Iran using four different versions of the Mann-Kendall method: i) conventional Mann-Kendall method (MK1); ii) Mann-Kendall method following removing the effect of significant lag-1 auto-correlation (MK2); ...
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The aim of this study is the analysis of surface wind speed in monthly and annual times scales in Iran using four different versions of the Mann-Kendall method: i) conventional Mann-Kendall method (MK1); ii) Mann-Kendall method following removing the effect of significant lag-1 auto-correlation (MK2); iii) Mann-Kendall method after the removing the effect of all significant auto-correlation coefficients (MK3); and Mann-Kendall method with considering the Hurst coefficient (MK4). Data used here are wind speed records in both monthly and annual time scales in the period of 1966-2005. For this purpose, 22 stations were selected across Iran’s area. Nonparametric Sen’s method was used for estimation of wind trend line slope. Results showed that although a combination of positive and negative trends observed both in monthly and annual time scales, however, the number of stations having the negative trends were more than that of the positive trends. In the annual time scale, the strongest negative trend line slope was -0.074 ms-1y-1 belonging to Fasa station, and the strongest positive trend line slope was 0.141 ms-1y-1 belonging to Zabol station. In monthly time scale, the strongest negative trend line slope was -0.1 ms-1y-1 observed in Fasa station and the the strongest positive trend line slope was 0.18 ms-1y-1 observed in Zabol station. Results showed that the median of the trend line slopes for all months (except February and November) was negative. Therefore, in general, it can be concluded that in the most of stations in Iran wind speed trend in all months (except February and November) was negative.
Yagoub Dinpazhooh; Faege Niazi; Hamed Mofid
Volume 19, Issue 51 , April 2015, , Pages 145-169
Abstract
The aim of this study is trend analysis of meteorological parameter including mean wind speed, min, max and mean air temperature, difference between the min and max temperature, pan evaporation, average relative humidity, sunshine hours, total precipitation, the number of days with precipitation more ...
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The aim of this study is trend analysis of meteorological parameter including mean wind speed, min, max and mean air temperature, difference between the min and max temperature, pan evaporation, average relative humidity, sunshine hours, total precipitation, the number of days with precipitation more than 1, 5 and 10 mm, the number of days with dust, number of the days with snow and the number of days with visibility less than 2Km, degree days based on 18 and 21 oC at Tabriz station during 1970-2005 in three time scales, monthly, seasonal and annually using the non-parametric Mann-Kendall (MK) method. Trend analysis was conducted using two methods, which are conventional MK (for series having insignificant autocorrelation coefficients) and modified MK (for other series) in three significant levels, 1%, 5% and 10%. Trend slopes were calculated using Sen’s estimator. Results showed that in annual time scale, pan evaporation, min, max and mean temperature and degree days based on 18 and 210C have significant increasing trends at 5% level but precipitation, number of the days with precipitation more than 1 and 5 mm and degree days based on 180C have decreasing trend (at 5% level). Other parameters did not show significant trend in annual time scale. Trend slope of annual precipitation was -2.28 mm/year and trend slopes of all three elements, average, max and min temperature were 0.06 0C/year. Observed trends in studying parameters indicate climate change in Tabriz.
Saeed Jahanbakhsh Asl; Ali . Mohammad Khorshiddoost; yaghoob Din Pazhooh; Fatemeh Sarafroozeh
Volume 18, Issue 50 , February 2015, , Pages 107-133
Abstract
Trend analysis of 27 indices related with extreme temperature and precipitation during 1961-2011 were conducted in Tabriz using the non-parametric Mann-Kendall test and Sen’s Estimator Slope methods. Furthermore Generalized Extreme Value distribution fitted to observational extreme events. Values ...
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Trend analysis of 27 indices related with extreme temperature and precipitation during 1961-2011 were conducted in Tabriz using the non-parametric Mann-Kendall test and Sen’s Estimator Slope methods. Furthermore Generalized Extreme Value distribution fitted to observational extreme events. Values of quantiles of the variables were estimated for different return periods. Results indicated that during the past half century, trends of indices for summer days, tropical nights and warm nights were upward and statistically significant. Trends of indices related to ice days and cool days were downward and significant. Minimum values of daily minimum and maximum temperature in year indicate significant increasing trends. Indices of number of days with precipitation greater or equal to 10 and 15 mm, consecutive wet days, total precipitation in wet days and total precipitation when rainfall is greater than 95 and 99 percentiles have experienced significant decreasing trends. After fitting GEV distribution to annual values of daily minimum and maximum temperature as well as daily maximum precipitation in Tabriz Growth curves and Q-Q plats were illustrated. Investigation of plots indicated that this distribution function has more capability in fitting of time series of extreme value even in tails of the distribution.
