Garingumo apskaičiavimo metodų palyginimas įvertinant Lietuvos klimatines sąlygas
| Date |
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2008 |
Straipsnyje analizuojama 13 skirtingu garingumo skaiciavimo priklausomybiu ir garomacio duomenys. Darbo tikslas – nustatyti šiu priklausomybiu taikymo galimybes Lietuvos klimatin mis salygomis, ju tarpusavio ryšius ir skaiciavimu paklaidas, kartu palyginti daugeli metu naudojama priklausomybe garingumui skaiciuoti pagal oro dr gm s deficita su Maisto ir žem s ukio organizacijos prie Jungtiniu Tautu (FAO) bei Tarptautin s sausinimo ir dr kinimo komisijos (ICID) rekomenduojama Penman – Monteith priklausomybe. Didžiausi garingumo, apskaiciuoto pagal analizuotas priklausomybes, nuokrypiai nustatyti skaiciuojant ji pagal temperaturines (išskyrus Hargreaves) priklausomybes. Iš radiaciniams metodams priskiriamu priklausomybiu garingumas, apskaiciuotas pagal Turc priklausomybe, tiksliausiai atitiko garinguma, apskaiciuota pagal kitiems metodams priskirtas priklausomybes. Glaudžiausias ryšys nustatytas taikant kompleksinio tipo priklausomybes. Pagal Lietuvos klimatin mis salygomis išvesta priklausomybe nuo oro dr gm s deficito (LT – m) garingumo reikšmiu mažiausias procentinis skirtumas buvo taikant temperaturine Hargreaves ir kompleksine FAO – 56 PM priklausomybes, o didžiausias – taikant Ivanov. Garingumas, apskaiciuotas pagal empirines priklausomybes, yra didesnis už išgaravima nuo vandens paviršiaus.
Evaluation of thirteen different methods for calculating reference evapotranspiration methods was carried out in order to determine the accuracy of different models under the Lithuanian climatic conditions. The article aimed at determining the correlative relations and standard errors of results obtained according to all considered dependencies as well as the dependency used for many years under the Lithuanian climatic conditions to calculate reference evapotranspiration according to air moisture deficit (LT – m). It was found that there is considerable variability among the methods (1.6 – 2.6 times). Application of combination type equations gave the best approximation among the methods. The temperature-based methods appeared to be the least accurate ones (with the exception of Hargreaves dependency). From the equations attributed to radiation methods the reference evapotranspiration, calculated according to Turc equation, most exactly conformed to the evapotranspiration, calculated according to the equations attributed to other methods. Comparison of the results obtained according to Lithuanian (LT – m) dependency and the ones calculated according to other equations showed that the smallest standard error of estimates (SEE – 7.59 – 7.70 mm/decade) was determined when Penman – Monteith dependency was used. The reference evapotranspiration, calculated according to combination methods, was bigger (by 4 – 28 %) than that calculated according to the Lithuanian one (LT – m), while the one calculated according to radiation Turc and Makkink was smaller (by 2-16 %) on average. Having compared evapotranspiration and evaporation from water surface values according to Penman – Monteith equation the SEE was 7.2 mm/decade.