Earth System Model FGOALS-s2: Coupling a dynamic global vegetation and terrestrial carbon model with the physical climate system model

Earth System Models （ESMs） are fundamental tools for understanding climate-carbon feedback. An ESM version of the Flexible Global Ocean-Atmosphere-Land System model （FGOALS） was recently developed within the IPCC AR5 Coupled Model Intercomparison Project Phase 5 （CMIP5） modeling framework, and we describe the development of this model through the coupling of a dynamic global vegetation and terrestrial carbon model with FGOALS-s2. The performance of the coupled model is evaluated as follows. The simulated global total terrestrial gross primary production （GPP） is 124.4 PgC yr-I and net pri- mary production （NPP） is 50.9 PgC yr-1. The entire terrestrial carbon pools contain about 2009.9 PgC, comprising 628.2 PgC and 1381.6 PgC in vegetation and soil pools, respectively. Spatially, in the tropics, the seasonal cycle of NPP and net ecosystem production （NEP） exhibits a dipole mode across the equator due to migration of the monsoon rainbelt, while the seasonal cycle is not so significant in Leaf Area Index （LAI）. In the subtropics, especially in the East Asian monsoon region, the seasonal cycle is obvious due to changes in temperature and precipitation from boreal winter to summer. Vegetation productivity in the northern mid-high latitudes is too low, possibly due to low soil moisture there. On the interannual timescale, the terrestrial ecosystem shows a strong response to ENSO. The model- simulated Nifio3.4 index and total terrestrial NEP are both characterized by a broad spectral peak in the range of 2-7 years. Further analysis indicates their correlation coefficient reaches -0.7 when NEP lags the Nifio3.4 index for about 1-2 months.     

The tropical intraseasonal oscillation in SAMIL coupled and uncoupled general circulation models

Simulations of tropical intraseasonal oscillation(TISO) in SAMIL,the Spectral Atmospheric Model from the Institute of Atmospheric Physics(IAP) State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) coupled and uncoupled general circulation models were comprehensively evaluated in this study.Compared to the uncoupled model,the atmosphere-ocean coupled model improved the TISO simulation in the following aspects:(1) the spectral intensity for the 30-80-day peak eastward periods was more realistic;(2) the eastward propagation signals over western Pacific were stronger;and(3) the variance distribution and stronger signals of Kelvin waves and mixed Rossby gravity waves were more realistic.Better performance in the coupled run was assumed to be associated with a better mean state and a more realistic relationship between precipitation and SST.In both the coupled and uncoupled runs,the unrealistic simulation of the eastward propagation over the equatorial Indian Ocean might have been associated with the biases of the precipitation mean state over the Indian Ocean,and the unrealistic split of maximum TISO precipitation variance over the Pacific might have corresponded to the exaggeration of the double Intertropical Convergence Zone(ITCZ) structure in precipitation mean state.However,whether a better mean state leads to better TISO activity remains questionable.Notably,the northward propagation over the Indian Ocean during summer was not improved in the mean lead-lag correlation analysis,but case studies have shown some strong cases to yield remarkably realistic northward propagation in coupled runs.     

中国地球气候系统模式的发展及其模拟和预估

地球气候系统模式是开展多学科、多圈层集成研究的重要平台,其发展是国际地学领域特别是全球变化领域竞争的前沿。中国的地球气候系统模式研发工作始于20世纪80年代,最近10年得到快速发展。研发格局上已经形成中国科学院、有关部委和高校三足鼎立的局面。文中在简要回顾中国地球气候系统模式早期发展历史的基础上,总结了中国参加第6次耦合模式比较计划的9个地球气候系统模式的技术特点,初步评估了中国4个模式对全球和东亚气候模拟的基本性能,分析了其在4种共享社会经济路径情景下对全球降水与温度的预估变化及其与平衡态气候敏感度的联系。最后,结合国际态势,从发展的角度提出未来中国气候模式研发工作需要加强的8个方向。      

青藏高原和亚洲夏季风动力学研究的新进展

亚洲夏季风环流受海陆和伊朗高原—青藏高原大地形的热力作用调控.亚洲季风所释放的巨大潜热又对大气环流形成反馈.这种相互反馈过程十分复杂,揭示其物理过程对理解气候变化格局的形成和变化以及提高天气预报及气候预测的准确率十分重要.夏季北半球副热带对流层上层环流的主要特征是存在庞大的南亚高压(SAH)以及强大的对流层上层温度暖中心(UTTM).本文介绍了温度—加热垂直梯度(T-Q_Z)理论的发展,并用以揭示SAH和UTTM的形成机制.指出沿副热带欧亚大陆东部的季风对流潜热加热及其中西部的表面感热加热和高层长波辐射冷却是导致SAH和UTTM在南亚上空发展的原因.文中还介绍了Gill模型用于上部对流层研究的局限性及解决的办法.     

Recent Progress in the Impact of the Tibetan Plateau on Climate in China

Studies of the impacts of the Tibetan Plateau （TP） on climate in China in the last four years are reviewed. It is reported that temperature and precipitation over the TP have increased during recent decades. From satellite data analysis, it is demonstrated that most of the precipitation over the TP is from deep convection clouds. Moreover, the huge TP mechanical forcing and extraordinary elevated thermal forcing impose remarkable impacts upon local circulation and global climate. In winter and spring, stream flow is deflected by a large obstacle and appears as an asymmetric dipole, making East Asia much colder than mid Asia in winter and forming persistent rainfall in late winter and early spring over South China. In late spring, TP heating contributes to the establishment and intensification of the South Asian high and the abrupt seasonal transition of the surrounding circulations. In summer, TP heating in conjunction with the TP air pump cause the deviating stream field to resemble a cyclonic spiral, converging towards and rising over the TP. Therefore, the prominent Asian monsoon climate over East Asia and the dry climate over mid Asia in summer are forced by both TP local forcing and Eurasian continental forcing.
Due to the longer memory of snow and soil moisture, the TP thermal status both in summer and in late winter and spring can influence the variation of Eastern Asian summer rainfall. A combined index using both snow cover over the TP and the ENSO index in winter shows a better seasonal forecast.
On the other hand, strong sensible heating over the Tibetan Plateau in spring contributes significantly to anchor the earliest Asian monsoon being over the eastern Bay of Bengal （BOB） and the western Indochina peninsula. Qualitative prediction of the BOB monsoon onset was attempted by using the sign of meridional temperature gradient in March in the upper troposphere, or at 400 hPa over the TP. It is also demonstrated by a numerical experiment and theoretical study that the heating over the TP lea     

The flexible global ocean-atmosphere-land system model, Grid-point Version 2: FGOALS-g2

This study mainly introduces the development of the Flexible Global Ocean-Atmosphere-Land System Model: Grid-point Version 2 (FGOALS-g2) and the preliminary evaluations of its performances based on results from the pre-industrial control run and four members of historical runs according to the fifth phase of the Coupled Model Intercomparison Project (CMIP5) experiment design. The results suggest that many obvious improvements have been achieved by the FGOALS-g2 compared with the previous version,FGOALS-g1, including its climatological mean states, climate variability, and 20th century surface temperature evolution. For example,FGOALS-g2 better simulates the frequency of tropical land precipitation, East Asian Monsoon precipitation and its seasonal cycle, MJO and ENSO, which are closely related to the updated cumulus parameterization scheme, as well as the alleviation of uncertainties in some key parameters in shallow and deep convection schemes, cloud fraction, cloud macro/microphysical processes and the boundary layer scheme in its atmospheric model. The annual cycle of sea surface temperature along the equator in the Pacific is significantly improved in the new version. The sea ice salinity simulation is one of the unique characteristics of FGOALS-g2, although it is somehow inconsistent with empirical observations in the Antarctic.     

国家自然科学基金大气科学学科二级申请代码下设研究方向与关键词解读:D0511大气数值模式发展

为响应国家自然科学基金委员会“优化学科布局”改革,大气科学学科于2020年完成了申请代码调整,明确了“分支学科”“支撑技术”“发展领域”三大板块的新布局。调整后大气数值模式发展被设置为“支撑技术”板块中的独立代码（D0511）。大气数值模式本质是基于物理或化学过程,应用数值算法求解偏微分方程组的数值解。大气数值模式发展应以攻克关键核心技术为导向,提升我国在该领域综合国际竞争力。为了服务大气数值模式发展领域的基金项目申请和评审,推动学科进一步发展,本文对国家自然科学基金大气科学学科二级申请代码D0511大气数值模式发展下设的研究方向和关键词进行了解读。系统介绍了D0511的设置背景、下设研究方向及关键词的总体框架。在对关键词进行解读的同时,基于文献计量方法和Web of Science数据库对该代码下不同方向的词频和研究热点进行了分析和讨论。结合近两年申请情况分析了关键词的使用情况,并就关键词的选择和优化提出了建议。后续还将在关键词设置基本指导思想不变的前提下,根据实际需求不断完善其具体内容。本文有助于申请人更好地理解及选择D0511下设的研究方向与关键词,亦可作为D0511研究方向和关...     

气候系统模式FGOALS-s1.1对热带降水年循环模态的模拟

文中评估了中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG/IAP)新一代耦合气候模式Fgoals_s1.1对热带降水年循环模态的模拟能力。通过与观测表层海温(SST)强迫的大气模式SAMIL试验结果比较,分析了海气耦合过程对年循环模态模拟效果的影响。结果表明Fgoals_s1.1能合理再现热带地区降水年循环模态的基本特征。Fgoals_s1.1模拟出了年平均降水场中的主要降水中心,但模拟的赤道和南太平洋降水偏多,而北太平洋降水则偏少。Fgoals_s1.1的季风模态降水呈现与观测一致的关于赤道反对称的特征,其模拟偏差大部分来自大气分量,尤其是在赤道外。Fgoals_s1.1的主要缺陷在于它对春秋非对称模态模拟能力低于单独大气模式,这主要是由于耦合模式模拟的SST距平的年循环位相与观测相反。SST纬向梯度的位相偏差使得太平洋沃克环流和印度洋的反沃克环流在春季强于秋季,最终导致模拟的春秋非对称模态的偏差。Fgoals_s1.1模拟的季风区范围接近观测,存在的问题在于模拟的西北太平洋季风区、东亚季风区都偏小。本文结果表明,大气模式偏差仅是Fgoals_s1.1在降水年循环模态模拟上的偏差的部分来源,改进模式模拟的SST,特别是赤道地区SST季节循环,是今后Fgoals_s1.1发展过程中急需解决的问题。     

Simulations of the East Asian subtropical westerly jet by LASG/IAP AGCMs

Performances of two LASG/IAP(State Key Laboratory of Numerical Modeling for Atmospheric Sci- ences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics)Atmospheric General Circulation Models(AGCMs),namely GAMIL and SAMIL,in simulating the major characteristics of the East Asian subtropical westerly jet(EASWJ)in the upper troposphere are examined in this paper.The mean vertical and horizontal structures and the correspondence of the EASWJ location to the meridional temperature gradient in the upper troposphere are well simulated by two models.However,both models underestimate the EASWJ intensity in winter and summer,and are unable to simulate the bimodal distribution of the ma- jor EASWJ centers in mid-summer,relative to the observation,especially for the SAMIL model.The biases in the simulated EASWJ intensity are found to be associated with the biases of the meridional temperature gradients in the troposphere,and furthermore with the surface sensible heat flux and condensation latent heating.The models capture the major characteristics of the seasonal evolution of the diabatic heating rate averaged between 30°-45°N,and its association with the westerly jet.However,the simulated maximum diabatic heating rate in summer is located westward in comparison with the observed position,with a rela- tively strong diabatic heating intensity,especially in GAMIL.The biases in simulating the diabatic heating fields lead to the biases in simulating the temperature distribution in the upper troposphere,which may further affect the EASWJ simulations.Therefore,it is necessary to improve the simulation of the meridional temperature gradient as well as the diabatic heating field in the troposphere for the improvement of the EASWJ simulation by GAMIL and SAMIL models.     

青藏高原增暖对东亚夏季风的影响——大气环流模式数值模拟研究

20世纪50年代以来,随着全球海表面温度年代际变化和全球变暖现象的出现,东亚夏季风降水和环流场也出现相应的年代际变化。是什么原因引起这个长期的变化趋势？研究表明青藏高原增暖可能是导致东亚夏季风年代际变化的重要因子之一。为了能够更好地理解青藏高原地表状况对下游东亚季风的影响,作者使用德国马普气象研究所大气环流模式（ECHAM）进行一系列数值试验。在两组敏感性试验中,通过改变高原上的地表反照率从而达到改变地表温度的目的。数值试验结果表明:青藏高原增暖有助于增强对流层上层的南亚高压、高原北侧西风急流和高原南侧东风急流以及印度低空西南季风;与此同时,东亚地区低层西南气流水汽输送增强。高原增暖后降水场的变化表现为:印度西北部季风降水增加,长江中下游以及朝鲜半岛梅雨降水增多;在太平洋副热带高压控制下的西北太平洋地区和孟加拉湾东北部,季风降水减少。对数值模拟结果的初步诊断分析表明:在感热加热和对流引起的潜热加热相互作用下,南亚高压强度加强,东亚夏季低层西南季风增大、梅雨锋降水增强,高原东部对流层上层的副热带气旋性环流增加,以及对流层低层的西太平洋副热带高压增强。另外,在青藏高原增暖的背景下,孟加拉湾地区季风降水减弱。本项研究有助于更好地理解东亚夏季风年代际变化特征和未来气候变化趋势。