The characteristics of evapotranspiration estimated by the complementary relationship actual evapotranspiration (CRAE), the advection-aridity (AA), and the modified advection-aridity (MAA) models were investigated in six pairs of rural and urban areas of Japan in order to evaluate the applicability of the three models the urban area. The main results are as follows: 1) The MAA model could apply to estimating the actual evapotranspiration in the urban area. 2) The actual evapotranspirations estimated by the three models were much less in the urban area than in the rural. 3) The difference among the estimated values of evapotranspiration in the urban areas was significant, depending on each model, while the difference among the values in the rural areas was relatively small. 4) All three models underestimated the actual evapotranspiration in the urban areas from humid surfaces where water and green spaces exist. 5) Each model could take the effect of urbanization into account.
Paper presents comparison of the daily reference crop (grass vegetation cover) potential evapotranspiration results calculated by the two modifications of the Penman-Monteith type equation. The first modification was published in FAO recommendation (Allen at al., 1998), PM-FAO, the second is modification according to Budagovskiy (1964) and Novák (1995), PM-BN. Both are used in soil water simulation models HYDRUS-1D and GLOBAL. Calculations were performed for frost-free seasons of the years 2000-2009, using the meteorological station Gabčíkovo (South Slovakia) meteorological data and canopy characteristics. The results indicate significant differences in daily and seasonal potential evapotranspiration. Reasons for those differences are discussed; they should be in different net radiation and aerodynamic resistance estimation methods.
In the paper a methodology for estimating monthly potential evapotranspiration (E0) as an input for hydrological balance modelling in the upper Hron River basin was developed. Four different methods were used to calculate monthly potential evapotranspiration in 6 climate stations in the basin - the Tomlain method based on equations of energy balance, the FAO method based on equations of radiation balance and empirical parameters, and 2 empirical methods - the Thornthwaite and Ivanov methods. Because of the relatively different results of E0 values estimated by these 4 methods, the physically based Tomlain method was considered as a reference method. Other methods containing empirical parameters were calibrated to estimate E0 with the best agreement to the Tomlain method. Calibration was done for each method and individual climate station, as well as for the whole region and was aimed to find a regional set of parameters for methods of E0 calculation. The method of genetic algorithm was used for the calibration. The efficiency of E0 computed by each of the calibrated methods was compared with the Tomlain method and the results were used for modelling of the hydrological balance in the basin. and Článok opisuje metodiku určovania mesačnej potenciálnej evapotranspirácie (E0) na povodí horného Hrona ako vstupu do hydrologického bilančného modelu s mesačným časovým krokom. Mesačná potenciálna evapotranspirácia je v modeli určovaná jednou zo 4 vybraných metód - metódou založenou na riešení energetickej bilancie, rozpracovanou Tomlainom, FAO metódou založenou na riešení radiačnej bilancie a 2 empirickými metódami výpočtu podľa Ivanova a Thornthwaitea. Podľa uvedených metód bol urobený výpočet E0 v 6 klimatických staniciach na povodí horného Hrona. Pretože metóda výpočtu podľa Tomlaina je založená na riešení rovníc energetickej bilancie, výsledky výpočtu E0 podľa nej boli ďalej považované za referenčné. Ostatné použité metódy, obsahujúce aj rovnice s empirickými parametrami boli kalibrované tak, aby výsledky výpočtu E0 týmito metódami boli v čo najlepšej zhode s výsledkami výpočtu E0 podľa Tomlainovej metódy. Kalibrácia metód na výpočet E0 bola urobená pre každú metódu a stanicu zvlášť. Následne boli pre každú metódu súbežnou kalibráciou vo všetkých staniciach určené regionálne parametre týchto metód, vhodné pre celé povodie. Pri kalibrácii parametrov boli využité metódy genetického algoritmu, ako objektívna funkcia bol použitý Nash-Sutcliffe koeficient. Výsledky výpočtu E0 sú v článku porovnané a využité na modelovanie priemerných mesačných prietokov v záverečnom profile povodia.
Pedunculate (Quercus robur) and sessile (Quercus patraea) oak, dominant species in European hardwood forests, are declining in many regions throughout Europe and extreme climatic events (summer drought, winter frost) are considered to be key factors contributing to this decline via a negative effect on wood formation. An extensive sampling of scattered oak trees within a landscape of small groves and flower meadows in the White Carpathians, a hilly chain in the warm south-eastern part of the Czech Republic, was undertaken in order to determine the association between growth in diameter and climate over the last 100 years. The association with climate was evaluated by comparing latewood, earlywood and total ring widths with monthly climatic data over the period 1900–2006, using a combination of response function and pointer year analyses. The two approaches clearly showed that late wood growth of oak trees, growing on deep calcium-rich soils, which dry out in summer, is mainly associated with rainfall in May–June, while early wood growth is associated with previous autumn and winter temperatures. Extreme growth years coincided with an abnormally wet or dry May–June periods, which are often associated with cool or hot Junes. Deficient water balances resulting from low rainfall and high temperatures during the summer period are negatively associated with late wood formation and hence total annual growth increment. The results provide support for a crucial role of climate change (decline in rainfall and increase in summer temperatures over the last three decades) among other external factors in the high number of oaks dying prematurely in the White Carpathian wooded grasslands. Prolonged periods of unfavourable climatic conditions cause attenuated trees to become prone to fungal attack and mistletoe hemiparasites, which predispose the oaks to damage or death, especially solitary pedunculate oaks.
Longwave radiation, as part of the radiation balance, is one of the factors needed to estimate potential evapotranspiration (PET). Since the longwave radiation balance is rarely measured, many computational methods have been designed. In this study, we report on the difference between the observed longwave radiation balance and modelling results obtained using the two main procedures outlined in FAO24 (relying on the measured sunshine duration) and FAO56 (based on the measured solar radiation) manuals. The performance of these equations was evaluated in the April–October period over eight years at the Liz experimental catchment and grass surface in the Bohemian Forest (Czech Republic). The coefficients of both methods, which describe the influence of cloudiness factor and atmospheric emissivity of the air, were calibrated. The Penman-Monteith method was used to calculate the PET. The use of default coefficient values gave errors of 40–100 mm (FAO56) and 0–20 mm (FAO24) for the seasonal PET estimates (the PET was usually overestimated). Parameter calibration decreased the FAO56 error to less than 20 mm per season (FAO24 remained unaffected by the calibration). The FAO56 approach with calibrated coefficients proved to be more suitable for estimation of the longwave radiation balance.