The Development Of NUIST Earth System Model And Simulation Of Global Monsoon Activities During Last Glacial Maximum

To meet the multiple needs for modeling paleoclimate changes, seamless climate prediction, high-impact climate events, and projecting future global environment changes. A coupled earth system model (ESM) has been developed at the Nanjing University of Information Science and technology (NUIST) by using version 5.3 of the European Centre Hamburg Model (ECHAM), version 3.4 of the Nucleus for European Modelling of the Ocean(NEMO), version 4.1 of the Los Alamos sea ice model (CICE), and OASIS3-MCT parallel coupler. The model is driven by two kinds of external forcing to evaluate the NESM1 performance, and used to exame the global monsoon activities during the Last Glacal Maximum in four kind of LGM forcing.Firstly, the NESM1 is forced by external forcing (greenhouse gases, solar constant etc.) fixed at the level of the year 1990.Comprehensive and quantitative metrics are used to assess the model’s major modes of climate variability most relevant to subseasonal-to-interannual climate prediction. The model’s assessment is placed in a multi-model framework. The model results indicate that:the model yields a realistic annual mean and annual cycle of equatorial SST, andreasonably realistic precipitation climatology, but has difficulty in capturing the spring-fall asymmetry. The ENSO mode is reproduced well with respect to its spatial structure, power spectrum, phase locking to the annual cycle, and spatial structures of the central Pacific (CP)-ENSO and eastern Pacific (EP)-ENSO; however, the equatorial SST variability, biennial component of ENSO, and the amplitude of CP-ENSO are overestimated. The model captures realistic intraseasonal variability patterns, the vertical-zonal structures of the first two leading predictable modes of Madden-Julian Oscillation (MJO), and its eastward propagation; but the simulated MJO speed is significantly slower than observed. The Pacific Decadal Oscillation, North Atlantic Oscillation, Arctic Oscillation, Antarctic Oscillation are well produced in the simulation. The performance of NESM1 was also compared with 20 coupled models that participated in CMIP5. It was found that NESM1 is among the top models with respect to the spatial distribution of monthly SST variance, the dominant mode of DJF ENSO variability, the spatial structures of the leading S-EOF modes of the AAM rainfall variability, and particularly for simulating the precipitation variance.Secondly, the model was used to simulate the Last Glacial Maximum climate in the framework of Peoloclimate Model Intercomparison Project Phase III (PMIP3) and compared with other PMIP3 coupled models. The results indicate that the NESM1 model can well capture the cool and dry climate during the LGM period compare to the pr-Industry simulation, with a global cooling of 4.7℃ and a decreasing in precipitation by 0.3mm/day(11%). The sensitivity of precipitation to change of surface air temperature (SAT) is about 2.26%℃-1, which is consistent with previous studies. Four additional experiments are conducted to access the impact of individual forcing on LGM climate and monsoon activity. There are Ice Sheets (IS), Green House Gases (GHG), Land Sea Configuration (LSC) and Earth Orbits (EO) experiment. The global mean SAT and precipitation are decreased about 1.2℃ and 0.06mm/day in IS simulation, but the changes are hemispheric asymmetric. The North Hemisphere (NH) avereaged SAT and precipitation are reduced 2℃ and 0.14mm/day, which is not obvious in the SH. In GHG simulation, the global mean SAT and precipitation are reduced 2.6℃ and 0.15mm/day, and the changes are hemispheric symmetric. However, the changes of global mean SAT and precipitation in LSC and EO simulations are not obvious. It turns out the nolinear interaction among each forcing plays a important role in the LGM climate change. The monsoon precipitation changes are different in the four simulations. In the IS simulation, the monsoon precipitation decrease is also asymmetric over the NH and SH. The mean monsoon precipitation and annual range are reduced by 0.24mm/day and 0.34mm/day, respectively, over the NH monsoon region, while the changes in SH monsoon region are not obvious. In the GHG simulation, the global summer monsoon precipitation is significant reduced, while the global winter monsoon precipitation change is not obvious. The change of land sea configuration can increase the Asian summer monsoon but dramatic decrease the Australian winter monsoon. Further studies are needed to invesitgate the imparct of changing EO on monsoon precipitation seasaon variation.