IAWBM Simulation Of Stable Isotope In Atmospheric Precipitation And Its Comparison With GNIP Measured Values

The general circulation model of water stable isotope can well reproduce the temporal and spatial distribution characteristics of stable isotopes in precipitation.In this paper,using dataset from 1979 to 2014 simulated by isotope Atmospheric Water Balance Model?iAWBM?,the spatial and temporal distribution of the stable isotope in global precipitation.At the same time,the simulation results of iAWBM are compared with the GNIP observations.Firstly,spatial distribution of the mean annual?¹⁸O,the mean seasonality of?¹⁸O,the precipitation amount effect,the temperature effect and Global Meteoric Water Line?GMWL?in global precipitation are analyzed.Secondly,the temporal variations of?¹⁸O,the linear relationship between?¹⁸O and meteorological factors?precipitation and temperature?,the Local Meteoric Water Line?LMWL?in precipitation at typical GNIP sites are analyzed.Meanwhile,the simulation results of iAWBM are compared with the GNIP observations,in order to inspect the capability of iAWBM simulating the water stable isotope cycle and improve the understanding of isotope effects in the cycle.According to a series of analyses,we obtain some valuable conclusions as follows.The simulation of iAWBM reproduces the latitude effect,continental effect and altitude effect of stable isotope in global precipitation.The spatial distribution of the simulated seasonality of?¹⁸O in precipitation is basically in agreement with the global patterns of the GNIP observations.In the northern hemisphere,?¹⁸O values are mostly lower in the warmer months?from April to September?than that in the colder months?from October to next March?in low latitude,but opposite in high latitude.The simulated precipitation amount effect is dominant in low-mid latitude oceans and monsoon areas;there is anti-precipitation amount effect in the mid-high latitudes of the mainland.Similarly,the simulated temperature effect is dominant in mid-high latitudes inland areas;there are also temperature effect in individual areas near the equator.The typical nine sites selected from GNIP sites are Hong Kong,Vienna,Yakutsk,Ottawa,Bangkok,Bogota,Kunming,Harare and Rarotonga.In the simulation results of temporal variation of?¹⁸O in precipitation,the model has simulated the general trend of?¹⁸O at each site.In the simulation results of precipitation effect,the model has simulated six sites'?Hong Kong,Bogota,Bangkok,Kunming,Harare and Rarot Tonga?significant precipitation effects;at the same time,the simulated precipitation effect is stronger than the actual precipitation effect.In the simulation results of tempreture effect,the model has simulated out three sites'?Vienna,Yakutsk,Ottawa?significant tempreture effect;the simulated temperature effect of Yakutsk station is very close to the actual situation,but other sites'temperature effect is weaker than the actual situation.The Global Meteoric Water Line observed by GNIP is:?²H=8.14?¹⁸O+11.55;the Global Meteoric Water Line simulated by iAWBM is:?²H=7.93?¹⁸O+10.19.The slope and intercept of the simulated GMWL are little different from the observed results.The model shows that there is a very good correlation between?¹⁸O and?²H at each site;The model has a good simulation effect on the slope of LMWL in each site,but in Vienna,Yakutsk,Kunming,the difference between the simulated values and the measured values of intercepts is slightly large.