جستجوی مقالات مرتبط با کلیدواژه "normalized rainfall curves" در نشریات گروه "آب و خاک"
تکرار جستجوی کلیدواژه «normalized rainfall curves» در نشریات گروه «کشاورزی»-
در این مطالعه، با استفاده از آمار روزانه ایستگاه هواشناسی تبریز به بررسی منحنی های بارش نرمال (NRC) پرداخته شد. برای این منظور، مقدار بارش روزانه به همراه تعداد روزهای بارانی به صورت تراکمی در نظر گرفته شد و به ترتیب، با و نشان داده شد، آنگاه منحنی های NRC براساس معادله های و بسط داده شد، این روش هم برای تمامی روزهای دوره آماری و هم برای هر ماه، به طور جداگانه، در طول دوره آماری به کار گرفته شد. مقادیر پارامترهای مدل ها با روش بهینه سازی و با گزینه solver در نرم افزار اکسل تخمین زده شدند. افزون بر این، چند مدل دیگر ریاضی (از جمله، مدل چندجمله ای درجه nام، توانی، توانی اصلاح شده، نمایی، نمایی پیوسته و...) نیز برای داده های و توسط نرم افزار Curve Expert 1.3 بسط داده شد. در نهایت، مدل با کمترین مقدار RMSE و بیشترین مقدار به عنوان مناسب ترین مدل معرفی گردید. نتایج نشان داد که تقریبا در همه موارد، مدل کمترین مقدار RMSE (4858/0 میلی متر) و بیشترین مقدار (9996/0) را دارا بود. بنابراین، مدل مذکور به عنوان مناسب ترین مدل برای بسط منحنی های NRC تبریز انتخاب شد. در مقیاس ماهانه، معیار RMSE از کمینه 22/0 میلی متر (در ماه سپتامبر) تا بیشینه 67/0 میلی متر (در ماه آوریل) تغییر می کند. در حالی که مقادیر این دو ماه، به ترتیب، 9999/0 و 9993/0 به دست آمد.
کلید واژگان: بارش روزانه, تبریز, توزیع زمانی, مدل تجربی, منحنی های بارش نرمالIn this study, by use of the daily rainfalls of Tabriz weather station the normalized rainfall curves (NRC) were investigated. For this purpose, the cumulative amount of daily rainfalls with the cumulative number of rainy days were considered and shown by and , respectively. Then, the NRCs were extracted according to the equations of and . This approach was applied to all days and every months of the data recording time period, separately. The parameters of models were estimated using the solver option in Excel software by the optimization method. Moreover, some of the other mathematical models (including the n-th degree polynomial, power, modified power, exponential, continuous exponential, etc.) were derived for and data by the Curve Expert 1.3 software. Among the all extracted models, a model having the lowest RMSE and highest was introduced as the most appropriate one. The results showed that, approximately, in the all cases the model with the lowest RMSE value (0.4858 mm) and the largest amount of (0.9996) was known as the most appropriate model to derive the NRCs of Tabriz station. Furthermore, in monthly time scale the amount of RMSE varied from 0.22 mm (in September) up to 0.67 mm (in April). The values for these two months obtained as 0.9999 and 0.9993, respectively.
Keywords: Daily rainfall, Experimental model, Normalized rainfall curves, Tabriz, Temporal distribution -
در این مطالعه، از بارش های روزانه ایستگاه های تبریز، مراغه، ارومیه و مهاباد جهت بررسی منحنی های بارش نرمال شده (NRC) استفاده شد. منحنی های بارش نرمال شده، نشان دهنده تغییرات درصد تجمعی مقادیر بارش های روزانه ( ) به ازای درصد تجمعی تعداد روزهای همراه با بارش ( ) است. برای بررسی این منحنی ها، از دو مدل رایج در هیدرولوژی شامل و استفاده شد، افزون بر این، پانزده مدل دیگر (از جمله، توانی، نمایی و...) نیز برای ایستگاه ها مورد آزمون واقع شد. این کار، هم برای تمامی روزهای بارانی دوره آماری و هم برای بارش های روزانه هر ماه به طور جداگانه (در هر ایستگاه) تکرار شد. از بین مدل های مذکور، مناسب ترین مدل با توجه به آماره های RMSE و انتخاب گردید. نتایج نشان داد که تقریبا در همه ایستگاه ها، مدل کمترین مقدار RMSE و بیشترین مقدار را دارا بود و به عنوان مناسب ترین مدل برای بسط منحنی های بارش نرمال شده انتخاب شد. با این حال، در ماه آوریل (در تبریز) مدل نمایی سه پارامتری و در ماه اوت (در مهاباد) مدل چندجمله ای درجه 4 به عنوان مدل مناسب انتخاب گردید. افزون بر این، اختلاف آماره این دو مدل با مشاهدات (در هر دو سری) کمتر از 0001/0 به دست آمد. در پرباران ترین و کم باران ترین ماه های سال، دامنه تغییرات RMSE بین 2559/0 میلی متر در آوریل (مراغه) و 6709/0 میلی متر در آوریل (تبریز) و مقادیر بین 9992/0 در اوت (مراغه) و 9999/0 در آوریل (مراغه) حاصل شد. در حالت کلی، می-توان نتیجه گرفت که در نیمی از روزهای همراه با بارش، کمتر از پانزده درصد کل عمق بارش نازل می شود.کلید واژگان: بارش روزانه, توزیع زمانی و مکانی, مدل تجربی, منحنی های بارش نرمال شدهJournal of water and soil, Volume:31 Issue: 5, 2018, PP 1481 -1496IntroductionStudy of various aspects of daily rainfalls is so crucial from the view of scientific management of water resources in every region. Iran is located in subtropical high-pressure belt, which had low annual rainfall. The precipitation regime is very irregular both in time and space. The East and West Azarbaijan provinces are known as the important areas of agriculture, especially cereal production in Iran. Therefore, study of temporal and spatial distribution of daily rainfalls is very important in this region. The purpose of this study is to extract the best model for normalized rainfall curves (NRC) in the four selected stations namely, Tabriz, Maragheh, Urmia and Mahabad.Materials And MethodsIn this study, daily rainfalls of four stations namely, Tabriz, Maragheh, Urmia and Mahabad were used to fit the normalized rainfall curves (NRC). For this purpose, the two custom hydrologic models i.e. and were employed for NRCs. In order to find the values of (cumulative percentage of daily rainfalls) firstly the amount of daily rainfalls observations were arranged in ascending Order. Then, cumulative percent of rainfall calculated during the time period. The NRC curves of each station, plotted by drawing the versus for a total statistical period, separately. This was done for a given month (eg, January) data across the whole period and whole day's rainfall during the consecutive months of the years of the study period. In the latter case, the daily rainfalls of the first month of the first year of the study period were written consecutively in a distinct column of Excel spreadsheets. Then, daily rainfalls of the second year were written similarly, following the first years data. Daily rainfalls of the third, fourth and so on were written consecutively in the same mentioned column of Excel spreadsheets. Similarly, another column attributed to the number of rainy days in the studied period. Then, the values of non-zero daily rainfalls (arranged in ascending order) accumulated consecutively, and the resulted value were divided to the total number of observed rainfalls in the period (R). Similarly cumulative rainy days were divided to the total days (N). Moreover, the other fifteen models (including the power, exponential ...), were tested for the stations observations separately. Among the mentioned models, the most suitable one is selected according to RMSE and criteria.Results And DiscussionResults showed that the maximum amount of daily rainfall experienced in Mahabad station in the rainiest month of the year or April (equivalent to 68 mm per day). The minimum value of daily rainfall belonged to the August (equivalent to 6 mm per day). The shape of NRCs created in this study for period in each of the four stations, showed that these curves were concave in almost all of the cases. This implies that a small amount of rainfall fell in a long period. In addition, the results showed that nearly in all of the stations the model of had the lowest value of RMSE and the largest value of . Therefore, this model selected as the most suitable one for NRCs of the stations. Although, the Exponential Association (3) model (in Tabriz) in April and the 4th degree Polynomial model (in Mahabad) in August selected as the most suitable model for them. Furthermore, the difference of statistics for the two models (at both of the time series) obtained as less than 0.0001. In the rainiest month and driest month of a year, the range of RMSE varied between 0.2559 mm in April (Maragheh) and 0.6709 mm in April (Tabriz). Moreover, the values varied between 0.9992 in August (Maragheh) and 0.9999 in April (Maragheh). In general, it can be concluded that the amount of precipitation receives in half of the rainy days is less than fifteen percent of the total rainfall depth. In this study, the values of of the most appropriate model for Tabriz, Urmia, Maragheh, Mahabad obtained as equal to 0.9996, 0.9997, 0.9996 and 0.9994, respectively.ConclusionsAmong the 17 candidate models, the model number 2 showed the highest , and the lowest RMSE. Therefore, the model was selected as the most appropriate model for drawing NRCs. Also, the mentioned model, were selected as the most appropriate model for all the months (in the four stations). The results showed that the NRCs were concave and in most cases, a small amount of total rainfall fell during the large number of days. In addition, in the two stations namely, Tabriz and Urmia the amount of rainfall receives in the 25, 50, 75 and 90 percent of rainy days were about two, 10, 30 and 60 percent of the total rainfall depth, respectivelyKeywords: Daily rainfall, Experimental model, Normalized rainfall curves, Temporal, spatial distribution
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