The Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 （FGOALS-s2） was used to simulate realistic climates and to study anthropogenic influences on climate change. Specifically, the FGOALS-s2 was integrated with Coupled Model Intercomparison Project Phase 5 （CMIP5） to conduct co- ordinated experiments that will provide valuable scientific information to climate research communities. The performances of FGOALS-s2 were assessed in simulating major climate phenomena, and documented both the strengths and weaknesses of the model. The results indicate that FGOALS-s2 successfully overcomes climate drift, and realistically models global and regional climate characteristics, including SST, precipita- tion, and atmospheric circulation. In particular, the model accurately captures annual and semi-annual SST cycles in the equatorial Pacific Ocean, and the main characteristic features of the Asian summer monsoon, which include a low-level southwestern jet and five monsoon rainfall centers. The simulated climate variabil- ity was further examined in terms of teleconnections, leading modes of global SST （namely, ENSO）, Pacific Decadal Oscillations （PDO）, and changes in 19th-20th century climate. The analysis demonstrates that FGOALS-s2 realistically simulates extra-tropical teleconnection patterns of large-scale climate, and irregu- lar ENSO periods. The model gives fairly reasonable reconstructions of spatial patterns of PDO and global monsoon changes in the 20th century. However, because the indirect effects of aerosols are not included in the model, the simulated global temperature change during the period 1850 2005 is greater than the observed warming, by 0.6℃. Some other shortcomings of the model are also noted.
The spectral version 1.1 of the Flexible Global Ocean–atmosphere–land System （FGOALS1.1-s） model was developed in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophys- ical Fluid Dynamics at the Institute of Atmospheric Physics （LASG/IAP）. This paper reports the major modifications to the physical parameterization package in its atmospheric component, including the radiation scheme, convection scheme, and cloud scheme. Furthermore, the simulation of the East Asian Summer Monsoon （EASM） by FGOALS1.1-s is examined, both in terms of climatological mean state and interannual variability. The results indicate that FGOALS1.1-s exhibits significant improvements in the simulation of the balance of energy at the top of the atmosphere： the net radiative energy flux at the top was 0.003 W m-2 in the 40 years fully coupled integration. The distribution of simulated sea surface temperature was also quite reasonable, without obvious climate drift. FGOALS1.1-s is also capable of capturing the major features of the climatological mean state of the EASM： major rainfall maximum centers, the annual cycle of precipitation, and the lower-level monsoon circulation flow were highly consistent with observations in the EASM region. Regarding interannual variability, simulation of the EASM leading patterns and their relationship with sea surface temperature was examined. The results show that FGOALS1.1-s can reproduce the first leading pattern of the EASM and its close relationship with the decaying phase of the ENSO. However, the model lacked the ability to capture either the second major mode of the EASM or its relationship with the developing phase of the ENSO.
Responses of the Asian Summer Monsoon(ASM) in future projections have been studied based on two core future projections of phase five of the Coupled Model Intercomparison Project(CMIP5) coordinated experiments with the IAP-coupled model FGOALS_s2(the Flexible Global Ocean-Atmosphere-Land System Model).The projected changes of the ASM in climatological mean and interannual variability were respectively reported.Both the South Asian Summer Monsoon(SASM) and the East Asian Summer Monsoon(EASM) were intensified in their climatology,featuring increased monsoon precipitation and an enhanced monsoon lower-level westerly jet flow.Accordingly,the amplitude of the annual cycle of rainfall over East Asia(EA) is enhanced,thereby indicating a more abrupt monsoon onset.After the EA monsoon onset,the EASM marched farther northward in the future scenarios than in the historical runs.In the interannual variability,the leading pattern of the EASM,defined by the first multi-variable EOF analysis over EA,explains more of the total variances in the warmest future scenario,specifically,Representative Concentration Pathway(RCP8.5).Also,the correlation coefficients analysis suggests that the relationship between the EASM interannual variations and ENSO was significantly strengthened in the future projections,which may indicate improved predictability of the EASM interannual variations.
The influence of soil moisture on Asian monsoon simulation/prediction was less studied, partly due to a lack of available and reliable soil moisture datasets. In this study, we firstly compare several soil moisture datasets over the Tibetan Plateau, and find that the remote sensing products from the Advanced Microwave Scanning Radiometer for Earth Observing System （AMSR-E） can capture realistic temporal variations of soil moisture better than the two reanalyses （NCEP and ECMWF） during the pre-monsoon seasons. Using the AMSR-E soil moisture product, we investigate the impacts of soil moisture over the Tibetan Plateau on Asian summer monsoon onset based on a Spectral Atmospheric Model developed at IAP/LASG （SAMIL）. Comparison between results with and without the assimilation of remotely sensed soil moisture data demonstrates that with soil moisture assimilated into SAMIL, the land-sea thermal contrast during pre-monsoon seasons is more realistic. Accordingly, the simulation of summer monsoon onset dates over both the Bay of Bengal and South China Sea regions are more accurate with AMSR-E soil moisture assimilated. This study reveals that the application of the soil moisture remote sensing products in a numerical model could potentially improve prediction of the Asian summer monsoon onset.
