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Long-term Stability and Oceanic Mean state Simulated by the Coupled Model FGOALS-s2

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Advances in atmospheric sciences 2013年第1期30卷 175-192页

作者：林鹏飞俞永强刘海龙 state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences

We describe the long-term stability and mean climatology of oceanic circulations simulated by version 2 of the Flexible Global Ocean-Atmosphere-Land System model （FGOALS-s2）. Driven by pre-industrial forcing, the integration of FGOALS-s2 was found to have remained stable, with no obvious climate drift over 600 model years. The linear trends of sea SST and sea surface salinity （SSS） were -0.04℃ （100 yr）-1 and 0.01 psu （100 yr）-1, respectively. The simulations of oceanic temperatures, wind-driven circulation and thermohaline circulation in FGOALS-s2 were found to be comparable with observations, and have been substantially improved over previous FGOALS-s versions （1.0 and 1.1）. However, significant SST biases （exceeding 3℃） were found around strong western boundary currents, in the East China Sea, the Sea of Japan and the Barents Sea. Along the eastern coasts in the Pacific and Atlantic Ocean, a warm bias （〉3℃） was mainly due to overestimation of net surface shortwave radiation and weak oceanic upwelling. The difference of SST biases in the North Atlantic and Pacific was partly due to the errors of meridional heat transport. For SSS, biases exceeding 1.5 psu were located in the Arctic Ocean and around the Gulf Stream. In the tropics, freshwater biases dominated and were mainly caused by the excess of precipitation. Regarding the vertical dimension, the maximal biases of temperature and salinity were located north of 65°N at depths of greater than 600 m, and their values exceeded 4℃ and 2 psu, respectively.

关键词： FGOALS stability mean state biases

Annual Frequency of Tropical Cyclones Directly Affecting Guangdong Province:Prediction Based on LSTM-FC

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Journal of Tropical Meteorology 2022年第1期28卷 45-56页

作者：胡娅敏陈韵竹何健刘圣军闫文杰赵亮汪明圣李芷卉王娟怀董少柔刘新儒 Guangdong Climate Center Guangzhou 510641 China School of Mathematics and Statistics Central South UniversityChangsha 410083 China state key laboratory of numerical modeling for Atmosphere sciences and geophysical fluid dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029 China

Tropical cyclone(TC)annual frequency forecasting is significant for disaster prevention and mitigation in Guangdong *** on the NCEP-NCAR reanalysis and NOAA Extended Reconstructed global sea surface temperature(SST)V5 data in winter,the TC frequency climatic features and prediction models have been *** 1951-2019,353 TCs directly affected Guangdong with an annual average of about *** have experienced an abrupt change from abundance to deficiency in the mid to late 1980 with a slightly decreasing trend and a normal distribution.338 primary precursors are obtained from statistically significant correlation regions of SST,sea level pressure,1000hPa air temperature,850hPa specific humidity,500hPa geopotential height and zonal wind shear in *** those 338 primary factors are reduced into 19 independent predictors by principal component analysis(PCA).Furthermore,the Multiple Linear Regression(MLR),the Gaussian Process Regression(GPR)and the Long Short-term Memory Networks and Fully Connected Layers(LSTM-FC)models are constructed relying on the above 19 *** three different kinds of test sets from 2010 to 2019,2011 to 2019 and 2010 to 2019,the root mean square errors(RMSEs)of MLR,GPR and LSTM-FC between prediction and observations fluctuate within the range of 1.05-2.45,1.00-1.93 and 0.71-0.95 as well as the average absolute errors(AAEs)0.88-1.0,0.75-1.36 and 0.50-0.70,*** for the 2010-2019 experiment,the mean deviations of the three model outputs from the observation are 0.89,0.78 and 0.56,together with the average evaluation scores 82.22,84.44 and 88.89,*** prediction skill comparisons unveil that LSTM-FC model has a better performance than MLR and *** conclusion,the deep learning model of LSTM-FC may shed light on improving the accuracy of short-term climate prediction about TC *** current research can provide experience on the development of deep learning in this field and help to achieve furthe

关键词： tropical cyclone frequency long short-term memory network fully connected layers Gaussian process regression multiple linear regression

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Long-term Behaviors of Two Versions of FGOALS2 in Preindustrial Control Simulations with Implications for 20th Century Simulations

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Advances in atmospheric sciences 2013年第3期30卷 577-592页

作者：林鹏飞刘海龙俞永强周天军 state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences

Climate drift in preindustrial control （PICTL） simulations can lead to spurious climate trends and large uncertainties in historical and future climate simulations in coupled models. This study examined the long- term behaviors and stabilities of the PICTL simulations in the two versions of FGOALS2 （the Flexible Global Ocean-Atmosphere-Land System model Version 2）, which have been submitted to the Coupled Model Inter- comparison Project Phase 5 （CMIP5）. As verified by examining time series of thermal fields and their linear trends, the PICTL simulations showed stable long-term integration behaviors and no obvious climate drift [the magnitudes of linear trends of SST were both less than 0.04℃ （100 yr）-1] over multiple centuries. The changed SSTs in a century （that corresponded to the linear trends） were less than the standard deviations of annual mean values, which implied the internal variability was not affected. These trend values were less than 10~0 of those of global averaged SST from observations and historical runs during the periods of slow and rapid warming. Such stable long-term integration behaviors reduced the uncertainty of the estimation of global warming rates in the historical and future climate projections in the two versions of FGOALS2. Compared with the trends in the Northern Hemisphere, larger trends existed in the SST and sea ice extents at the middle to high latitudes of the Southern Hemisphere （SH）. To estimate the historical and future climate trends in the SH or at some specific regions in FGOALS2, corrections needed to be carried out. The similar long-term behaviors in the two versions of FGOALS2 may be attributed to proper physical processes in the ocean model.

关键词： FGOALS climate drift preindustrial run global warming

Relationships between the Limit of Predictability and Initial Error in the Uncoupled and Coupled Lorenz Models

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Advances in atmospheric sciences 2012年第5期29卷 1078-1088页

作者：丁瑞强李建平 state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences

In this study, the relationship between the limit of predictability and initial error was investigated using two simple chaotic systems： the Lorenz model, which possesses a single characteristic time scale, and the coupled Lorenz model, which possesses two different characteristic time scales. The limit of predictability is defined here as the time at which the error reaches 95% of its saturation level; nonlinear behaviors of the error growth are therefore involved in the definition of the limit of predictability. Our results show that the logarithmic function performs well in describing the relationship between the limit of predictability and initial error in both models, although the coefficients in the logarithmic function were not constant across the examined range of initial errors. Compared with the Lorenz model, in the coupled Lorenz model in which the slow dynamics and the fast dynamics interact with each other--there is a more complex relationship between the limit of predictability and initial error. The limit of predictability of the Lorenz model is unbounded as the initial error becomes infinitesimally small; therefore, the limit of predictability of the Lorenz model may be extended by reducing the amplitude of the initial error. In contrast, if there exists a fixed initial error in the fast dynamics of the coupled Lorenz model, the slow dynamics has an intrinsic finite limit of predictability that cannot be extended by reducing the amplitude of the initial error in the slow dynamics, and vice versa. The findings reported here reveal the possible existence of an intrinsic finite limit of predictability in a coupled system that possesses many scales of time or motion.

关键词： limit of predictability initial error Lorenz model coupled Lorenz model

Multiscale Combined Action and Disturbance Characteristics of Pre-summer Extreme Precipitation Events over South China

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Advances in atmospheric sciences 2023年第5期40卷 824-842页

作者： Hongbo LIU Ruojing YAN Bin WANG Guanghua CHEN Jian LING Shenming FU state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary sciences University of Chinese Academy of SciencesBeijing 100049China key laboratory of Cloud-Precipitation Physics and Severe Storms(LACS) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China International Center for Climate and Environment sciences(ICCES) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

The dominant frequency modes of pre-summer extreme precipitation events(EPEs)over South China(SC)between1998 and 2018 were *** 67 identified EPEs were all characterized by the 3-8-d(synoptic)frequency ***,multiscale combined modes of the synoptic and three low-frequency bands[10-20-d(quasi-biweekly,QBW);15-40-d(quasi-monthly,QM);and 20-60-d(intraseasonal)]accounted for the majority(63%)of the EPEs,and the precipitation intensity on the peak wet day was larger than that of the single synoptic *** was found that EPEs form within strong southwesterly anomalous flows characterized by either lower-level cyclonic circulation over SC or a deep trough over eastern ***-filtered disturbances revealed the direct precipitating systems and their life ***-scale disturbances are dominated by mid-high latitude troughs,and the cyclonic anomalies originate from downstream of the Tibetan Plateau(TP).Given the warm and moist climate state,synoptic-scale northeasterly flows can even induce *** the QBW and QM scales,the disturbances originate from the tropical Pacific,downstream of the TP,or mid-high latitudes(QBW only).Each is characterized by cyclonic-anticyclonic wave trains and intense southwesterly flows between them within a region of large horizontal pressure *** intraseasonal disturbances are confined to tropical regions and influence SC by marginal southwesterly *** is concluded that low-frequency disturbances provide favorable background conditions for EPEs over SC and synoptic-scale disturbances ultimately induce EPEs on the peak wet *** should be simultaneously considered for EPE predictions over SC.

关键词： extreme precipitation event dominant frequency band multiscale combined action disturbance chara-cteristics South China

Performance of FGOALS-s2 in Simulating Intraseasonal Oscillation over the South Asian Monsoon Region

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Advances in atmospheric sciences 2013年第3期30卷 607-620页

作者：胡文婷段安民吴国雄 state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences

The capability of the current version of the air-sea coupled climate model, the Flexible Global Ocean- Atmosphere-Land System model, Spectral Version 2 （FGOALS-s2）, in simulating the boreal summer in- traseasonal oscillation （ISO） over the south Asian monsoon （SAM） region is diagnosed, in terms of dominant period, propagation direction, and vertical structure. Results show that the coupled model can reasonably simulate the main features of observed ISO propagation compared to the chosen AGCM. These features in- clude the eastward movement of intraseasonal 850-hPa zonal wind over the Arabian Sea and Bay of Bengal, the vertical structure in active phases, and the realistic phase relationship between ISO and underlying SST. However, the eastward propagation cannot be reproduced in the uncoupled model. This suggests that air- sea interaction is important in generating intraseasonal variability over the SAM region. Nevertheless, some deficiencies remain in the coupled model, which may relate to physical processes depicted by the cumulus parameterization and PBL schemes within its atmospheric component.

关键词： intraseasonal oscillation numerical simulation eastward propagation air-sea interaction

The Significant Relationship between the Arctic Oscillation (AO) in December and the January Climate over South China

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Advances in atmospheric sciences 2011年第2期28卷 398-407页

作者：杨辉 state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences

Using NCEP/NCAR reanalysis data, the China rainfall and surface temperature data of the China Meteorological Administration, and the Arctic Oscillation （AO） indices of NOAA, the author investigates relationships between the AO and the precipitation and temperature over China. There exists a good relationship between the AO index in December and the succeeding January precipitation over South China, indicating that when the December AO index is positive （negative）, the January precipitation over South China increases （decreases）. A remarkable negative correlation between the December AO index and the January surface temperature also exists over South China, indicating that when the December AO index is positive （negative）, the January temperature over South China drops （rises）. The occurrence of this anomalous climate is related to the anomalies of the atmospheric circulation systems. The December AO greatly influences circulation anomalies in January. A positive phase of the AO is found to lead to a stronger subtropical jet over the south side from the Iran Plateau to the Tibetan Plateau. Consequently, it results in a deepening pressure trough around the Bay of Bengal, which transports the warm and wet air to South China continuously. The Siberian High in January is stronger and extends farther southeastward. It results in continual cold air at 1000 hPa pouring into South China, inducing low temperature. Cooperating with the trough of the Bay of Bengal, anomalous precipitation occurs over South China. For the negative phase of the December AO, the opposite situation is observed.

关键词： Arctic Oscillation precipitation surface temperature large-scale circulation

Rainfall Assimilation Using a New Four-Dimensional Variational Method:A Single-Point Observation Experiment

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Advances in atmospheric sciences 2011年第4期28卷 735-742页

作者：刘娟娟王斌 state key laboratory of numerical modeling for atmospheric sciences & geophysical fluid dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences

Accurate forecast of rainstorms associated with the mei-yu front has been an important issue for the Chinese economy and society. In July 1998 a heavy rainstorm hit the Yangzi River valley and received widespread attention from the public because it caused catastrophic damage in China. Several numerical studies have shown that many forecast models, including Pennsylvania state University National Center for atmospheric Research’s fifth-generation mesoscale model （MM5）, failed to simulate the heavy precipitation over the Yangzi River valley. This study demonstrates that with the optimal initial conditions from the dimension-reduced projection four-dimensional variational data assimilation （DRP-4DVar） system, MM5 can successfully reproduce these observed rainfall amounts and can capture many important mesoscale features, including the southwestward shear line and the low-level jet stream. The study also indicates that the failure of previous forecasts can be mainly attributed to the lack of mesoscale details in the initial conditions of the models.

关键词： data assimilation dimension-reduced projection four-dimensional variational data assimilation (DRP-4DVar) rainstorm numerical simulation

Effect of Chlorophyll-a Spatial Distribution on Upper Ocean Temperature in the Central and Eastern Equatorial Pacific

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Advances in atmospheric sciences 2008年第4期25卷 585-596页

作者：林鹏飞刘海龙张学洪 state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences

Effect of the spatial distributions of chlorophyll-a concentration on upper ocean temperature and currents in the equatorial Pacific is investigated through a set of numerical experiments by using an ocean general circulation model. This study indicates that enhanced meridional gradient of chlorophyll-a between the equator and off-equatorial regions can strengthen zonal circulation and lead to a decrease in equatorial sea surface temperature （SST）. However, the circulation changes by themselves are not effective enough to affect SST in the equatorial cold tongue （CT） region. The comparison between the experiments indicates that the CT SST are more sensitive to chlorophyll-a distribution away from the equator. The off-equatorial chlorophyll-a traps more solar radiation in the mixed layer, therefore, the temperature in the thermoeline decreases. The cold water can then be transported to the equator by the meridional circulation within the mixed layer. Furthermore, the relation among CT SST, the surface heat flux, and the equatorial upwelling are discussed. The study implies the simulation biases of temperature on the equator are not only related to the local ocean dynamics but also related to some deficiency in simulating off-equatorial processes.

关键词： sea surface temperature the equatorial cold tongue chlorophyll-a