The Effect Of Time Series On The Local Meteoric Water Line In Different Climate Regions

Local meteoric water line(LMWL)has been the important component in the stable isotope of precipitation study.However,previous studies have not notified the length of stable isotope dataset(years)and different methods should be applied to establish local meteoric water line for different kind of climate regions.The study analyzed and compared the differences in the establishment of LMWL under precipitation isotope data of different climate regions,different regression methods and time scales.There are six different linear regression methods(OLSR,RMA,MA and their precipitation weighted regression),and to explore the optimal method for the establishment of LMWL in the Loess Plateau and the other three regions(Braunschweig,Saskatoon,and Almeria).The results show that all of the OLSR based slopes of the LMWL are lower than GMWL.It suggested that there is an existence of the influence of the secondary evaporation intensity under the cloud.It is showed that OLRS regression should be used in semi-humid region with both event-based or monthly data.OLSR based slopes of either event-based or monthly data in arid region are significantly different from PWRMA based slopes with event-based data.In the semi-arid region,the OLSR based slope significantly differed from the PWRMA based slope using event-based precipitation data(p< 0.05),but did not significantly differ from monthly precipitation data(p> 0.05).Moreover,Small precipitation amount and data size is so sensitive to LMWL in more arid region.the slope of LMWL established by precipitation samples over 3 years shows good stability.More humid region does not have certain pattern of slope distribution regarding sample size and precipitation amount.LMWL in humid-semi-humid areas is greatly affected by the distance between land and sea and local hydrological environment.Therefore,timescale needed for establishing LMWL is more longer in more humid region.The results of this study provide a reliable LMWL for isotopic hydrological research on the Loess Plateau,and clarify the influence of precipitation data sets based on different time scales on the establishment of LMWLs in different climatic regions.It is suggested that the local climate conditions should be taken into full consideration in the establishment of LMWL,and an appropriate linear regression method should be selected for the establishment of LMWL.