In this study, the clear sky hourly global and net solar irradiances at the surface determined using SUNFLUX, a simple parameterization scheme, for three stations （Gaize, Naqu, and Lhasa） on the Tibetan Plateau were evaluated against observation data. Our modeled results agree well with observations. The correlation coefficients between modeled and observed values were 〉 0.99 for all three stations. The relative error of modeled results, in average was 〈 7%, and the root-mean-square variance was 〈 27 W m-2. The solar irradiances in the radiation model were slightly overestimated compared with observation data; there were at least two likely causes. First, the radiative effects of aerosols were not included in the radiation model. Second, solar irradiances determined by thermopile pyranometers include a thermal offset error that causes solar radiation to be slightly underestimated. The solar radiation absorbed by the ozone and water vapor was estimated. The results show that monthly mean solar radiation absorbed by the ozone is 〈 2% of the global solar radiation （〈 14 W m-2）. Solar radiation absorbed by water vapor is stronger in summer than in winter. The maximum amount of monthly mean solar radiation absorbed by water vapor can be up to 13% of the global solar radiation （95 W m-2）. This indicates that water vapor measurements with high precision are very important for precise determination of solar radiation.
In this study, we simulated and analyzed the monthly variations of stable water isotopes in different reservoirs at Manaus, Brazil, using the Community Land Model (CLM) that incorporates stable isotopic effects as a diagnostic tool for understanding stable water isotopic processes, filling the observational data gaps and predicting hydrometeorological processes. The simulation results show that the δ 18O values in precipitation, vapor and surface runoff have distinct seasonality with the marked negative correlations with corresponding water amount. Compared with the survey results by the International Atomic Energy Agency (IAEA) in co-operation with the World Meteorological Organization (WMO), the simulations by CLM reveal the similar temporal distributions of the δ 18O in precipitation. Moreover, the simulated amount effect between monthly δ 18O and monthly precipitation amount, and MWL (meteoric water line) are all close to the measured values. However, the simulated seasonal difference in the δ 18O in precipitation is distinctly smaller than observed one, and the simulated temporal distribution of the δ 18O in precipitation displays the ideal bimodal seasonality rather than the observed single one. These mismatches are possibly related to the simulation capacity and the veracity in forcing data.
