•The boundary conditions of Fu's equations in Budyko Framework are highlighted.•Equilibrium evaporation coefficient was adjusted by Fu's equations' interrelation.•We improved the complementary ...principle function for better evaporation estimate.•Our blended function substantially enhances annual E estimation performance.•The improved method shows the highest improvement of daily E in extreme climates.
The complementary principle function presents a framework for estimating evaporation but faces long-term challenges in calibration with a free parameter-equilibrium evaporation coefficient. The blending the evaporation precipitation ratio with complementary principle function is proposed to provide a physical basis for estimation of the equilibrium evaporation coefficient within the Budyko framework; however, it overlooks the limited possible maximum evaporation and precipitation condition from Fu’s equations. In this study, we expanded the numerical ambiguity boundary conditions of Fu’s equations and introduced a new parameter γc into the blended function to fully capture the environmental conditions, aiming to mitigate errors related to extreme climates. The result indicated our improved blended function performed better than the original function. Compared to the original function, the estimated annual average evaporation across stations improved from 0.12 to 0.57 in coefficient of determination (R2) and from 322.83 mm to 172.47 mm in Root Mean Square Error. For daily evaporation estimation, the Nash-Sutcliffe Efficiency coefficient (NSE) increased from 0.32 to 0.47 and R2 increased from 0.38 to 0.48 in all validation sites. The modified blended method showed a better performance in most of the AmeriFLUX stations, especially with the highest improvement in extremely dry and wet sites. Our new approach represents a promising evaporation method in extreme climate conditions and provides support for future research to identify the rigorous equation constraints of Budyko equations.
Assessing net primary productivity (NPP) dynamics and the contribution of land-use change (LUC) to NPP can help guide scientific policy to better restore and control the ecological environment. Since ...1999, the “Green for Grain” Program (GGP) has strongly affected the spatial and temporal pattern of NPP on the Loess Plateau (LP); however, the multifaceted impact of phased vegetation engineering measures on NPP dynamics remains unclear. In this study, the Carnegie-Ames-Stanford Approach (CASA) model was used to simulate NPP dynamics and quantify the relative contributions of LUC and climate change (CC) to NPP under two different scenarios. The results showed that the average NPP on the LP increased from 240.7 gC·m−2 to 422.5 gC·m−2 from 2001 to 2020, with 67.43% of the areas showing a significant increasing trend. LUC was the main contributor to NPP increases during the study period, and precipitation was the most important climatic factor affecting NPP dynamics. The cumulative amount of NPP change caused by LUC (ΔNPPLUC) showed a fluctuating growth trend (from 46.23 gC·m−2 to 127.25 gC·m−2), with a higher growth rate in period ΙΙ (2010–2020) than in period Ι (2001–2010), which may be related to the accumulation of vegetation biomass and the delayed effect of the GGP on NPP. The contribution rate of LUC to increased NPP in periods Ι and ΙΙ was 101.2% and 51.2%, respectively. Regarding the transformation mode, the transformation of grassland to forest had the greatest influence on ΔNPPLUC. Regarding land-use type, the increased efficiency of NPP was improved in cropland, grassland, and forest. This study provides a scientific basis for the scientific management and development of vegetation engineering measures and regional sustainable development.
•Precipitation is the main climatic factor for NPP growth on the Loess Plateau.•Land-use change (LUC) contributed more to NPP growth than to climate change.•The rise efficiency of NPP in 2010–2020 was higher than that in 2001–2010.•NPP variations caused by LUC were the greatest for the grassland conversion to forest.
•Streamflow and baseflow are affected by climate change and human activities.•The ABIT method is used to separate baseflow in typical basin of Qinling Mountains.•Precipitation has closer ...relationships with streamflow in comparison with baseflow in the Bahe River, while potential evapotranspiration is opposite.
Streamflow and its components, such as baseflow, are momentous links of the hydrological cycle, and their spatiotemporal variations are affected by both climate change and human activities (CCHU). However, discrepancies in the influence of CCHU on streamflow and hydrological components are not fully understood. In this study, meteorological factors (precipitation and potential evapotranspiration) and hydrological variables (streamflow and baseflow) were analyzed to quantify the responses of the streamflow and baseflow in the Bahe River to the CCHU during 1959–2016. The hydrometeorological variables in the Bahe River showed a downward trend, except for the baseflow at the Luolicun hydrological station (LLC), while the mutation point at the Maduwang hydrological station (MDW) was in 1989, and LLC was mutated in 1980 and 1989. Precipitation was closely related to streamflow in comparison with baseflow (r = 0.871 ± 0.034), whereas potential evapotranspiration was the opposite. The streamflow and baseflow at MDW had closer relationships with precipitation than at LLC (r = 0.828 ± 0.077), while LLC was more affected by potential evapotranspiration (r = −0.698 ± 0.004). Streamflow and baseflow upstream of the Bahe River were mainly affected by human activities (67–75 % and 74–78 %, respectively), and baseflow midstream due to climate change (90–147 %). The contributions of climate change and human activities to midstream streamflow were 37–75 % and 25–63 %, respectively. Our findings highlight the responses of streamflow and baseflow to environmental changes, which will enhance our understanding of the response mechanisms of the hydrological cycle in a changing environment.
This research was focused on the homogeneous precipitation synthesis of a series of Eu3+ ion-activated ellipsoidal La2O2SO4 phosphors based on the La2(SO4)3-CO(NH2)2 reaction system. The structural ...identification, thermal analysis, morphology and luminescence properties of the as-prepared products were characterized with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG/DSC), field emission scanning electron microscopy (FESEM) and photoluminescence (PL) spectra. Pure La2O2SO4 ellipsoidal particles with a long radius of about 2 µm and a short radius of about 1 µm were successfully prepared by calcining a rhombus-like precursor at 800 °C for 2 h in air. The formation mechanism of the precursor and its corresponding calcination product were also proposed. Photoluminescence results revealed that the strongest red emission peak was centered at 619 nm upon 249-nm ultraviolet (UV) light excitation in La2O2SO4:x%Eu3+ (x = 3, 6, 9, 12 and 15) phosphors. The exchange interaction was responsible for the concentration quenching mechanism of the 5D0→7F2 transition of Eu3+ ions in the La2O2SO4 host lattice. The optimal x value was 15 and the corresponding decay process showed a single exponential decay behavior whose lifetime t and color correlation temperature (CCT) were calculated to be 2.112 ms and 2752 K, respectively.
