Integrated Assessment of Long-term Climate Policies: Part 2 – Model Results and Uncertainty Analysis

An integrated assessment model (IAM) is applied to explore optionsfor long-term climate policy by identifying permitted emissioncorridors. The options are determined under various assumptionsabout constraints related to acceptable impacts of climate changein terms of alterations induced in natural ecosystems in protectedareas and about acceptable mitigation costs, burden sharingprinciples, and implementation flexibility. The results show thatabout 25% of the protected areas worldwide will witness ecosystemtransformation in the next century even if the costs of emissionreduction are allowed to reach 2% of per-capita consumption. Anuncertainty analysis surveys the implications of modifyingselected key model variables on the existence and shape of theemission corridors. Within plausible ranges of parametervariations, the emission corridor turns out to be rather sensitiveto impact constraints, climatic constraints like the magnitude andrate of the global mean temperature increase, and to aerosolemission scenarios.     

Fast CO2 Retrieval Using a Semi-Physical Statistical Model for the High-Resolution Spectrometer on the Fengyun-3D Satellite

China's Fengyun-3D meteorological satellite launched in December 2016 carries the high-resolution greenhouse- gases absorption spectrometer (GAS) aimed at provi...     

利用生物圈模型 (SiB2) 模拟青藏高原那曲草原近地面层能量收支

模式所需要的参数被合理地设置之后, 根据GAME/ Tibet (GEWEX亚洲季风试验/青藏高原试验) 那曲近地层观测站的资料, 将大气强迫变量代入SiB2(Simple Biosphere model version2), 文章模拟了该观测站地表能量收支。结果表明:SiB2能够较好地模拟青藏高原的能量收支情况, 净辐射、潜热通量和土壤热通量的模拟值和观测值吻合, 它们的相对误差分别为8% (低估)、6% (低估) 和3 %(低估)。同时, SiB2高估感热通量达40%。文章还给出了能量各分量的详细比较分析。     

Estimating a Lagrangian Length Scale Using Measurements of CO2 in a Plant Canopy

Analytical Lagrangian equations capable of predicting concentration profiles from known source distributions offer the opportunity to calculate source/sink distributions through inverted forms of these equations. Inverse analytical Lagrangian equations provide a practical means of estimating source profiles using concentration and turbulence measurements. Uncertainty concerning estimates of the essentially immeasurable Lagrangian length scale ( ${\mathcal{L}}$ ), a key input, impedes the operational practicality of this method. The present study evaluates ${\mathcal{L}}$ within a corn canopy by using field measurements to constrain an analytical Lagrangian equation. Measurements of net CO₂ flux, soil-to-atmosphere CO₂ flux, and in-canopy profiles of CO₂ concentration provided the information required to solve for ${\mathcal{L}}$ in a global optimization algorithm for 30-min time intervals. For days when the canopy was a strong CO₂ sink, the optimization frequently located ${\mathcal{L}}$ profiles that follow a convex shape. A constrained optimization then fit the profile shape to a smooth sigmoidal equation. Inputting the optimized ${\mathcal{L}}$ profiles in the forward and inverse Lagrangian equations leads to strong correlations between measured and calculated concentrations and fluxes. Coefficients of the sigmoidal equation were specific to each 30-min period and did not scale with any measured variable. Plausible looking ${\mathcal{L}}$ profiles were associated with negative bulk Richardson number values. Once the canopy senesced, a simple eddy diffusivity profile sufficed to relate concentrations and sources in the analytical Lagrangian equations.     

瓦里关山大气二氧化碳浓度变化及地表排放影响的研究

利用非色散红外气体分析方法，在不受人为污染直接影响的瓦里关山进行了大气CO2的连续测量，给出了我国内陆高原大气CO2本底浓度的变化特征，观测表明内陆大气CO2随陆地植被的生长而有明显的日变化及季节的周期变化，其季节变化规律与全球大气CO2本底值的地理分布相一致。瓦里关山大气CO2的年增长率在1993年明显偏低，1994年又有较快的“回升”。地表CO2排放的观测研究还给出了冬季高原草甸土壤的排放特征，测量表明在冬季陆地植被光合作用基本停滞的情况下，土壤CO2的排放率相对增强，其最大排放量可达170 mg/m2·h以上。     

简单生物圈模式 (SiB2) 中湍流能量通量对近地层两类阻抗系数的敏感性研究

陆—气之间的能量交换是通过近地层湍流热量和水汽通量来实现的.以往的研究表明近地层阻抗对湍流能量通量有着不同程度的影响,但是关于陆面模式中阻抗系数的取值范围却始终没有统一的标准.为了深入了解简单生物圈模式 (SiB₂) 中近地层阻抗系数取值变化对湍流能量通量的影响,我们以那曲站为例,分别采用传统的逐个因子分析法和考虑参数间相互作用的部分因子分析法定量地研究了夏季该观测站近地层湍流能量通量分别对冠层阻抗系数C₁和地表阻抗系数C₂的敏感性响应.结果表明,感热通量对地表阻抗系数C₂更为敏感,而潜热通量则对冠层阻抗系数C₁较为敏感;感热通量随C₁增加而增大,随C₂增加而减小,而潜热通量则随C₁或C₂的增加而减小;不管是感热通量还是潜热通量,它们对阻抗系数的敏感度随阻抗系数的增大而减小,而对阻抗系数的相对敏感度则随阻抗系数的增大而增大.最后,结合那曲站夏季下垫面稀疏短草的分布特点分析了造成感热通量和潜热通量敏感变化各异的原因.     

气溶胶-气候耦合模式系统BCC_AGCM2.0.1_CAM气候态模拟的初步评估

本文讨论了国家气候中心第二代大气环流模式BCC_AGCM2.0.1和加拿大气溶胶理化模式CAM所组成的耦合模式系统对5种典型气溶胶(硫酸盐、黑碳、有机碳、沙尘和海盐)和气候要素的模拟效果。结果表明,耦合系统对5种典型气溶胶的模拟总体上比较合理,尤其是对硫酸盐、沙尘和海盐的模拟比BCC_AGCM2.0.1原有的月平均气溶胶资料有很大的改进。耦合系统模拟的全球平均气候态参量与观测/再分析资料比较一致,在总云量、陆地表面温度和降水等方面要略优于原月平均气溶胶资料的模拟结果。耦合系统对沙尘和海盐气溶胶模拟的改进使得撒哈拉沙漠和南半球中纬度海洋大气顶净太阳辐射的模拟也有所改进,而这将直接影响地表温度尤其是陆地表面温度。而不同气溶胶方案在赤道海洋上引起的云反馈不仅引起辐射的改变,还将对降水产生明显影响。     

Adaptation, Spatial Heterogeneity, and the Vulnerability of Agricultural Systems to Climate Change and CO2 Fertilization: An Integrated Assessment Approach

In this paper we develop economic measures of vulnerability to climate change with and without adaptation in agricultural production systems. We implement these measures using coupled, site-specific ecosystem and economic simulation models. This modeling approach has two key features needed to study the response of agricultural production systems to climate change: it represents adaptation as an endogenous, non-marginal economic response to climate change; and it provides the capability to represent the spatial variability in bio-physical and economic conditions that interact with adaptive responses. We apply this approach to the dryland grain production systems of the Northern Plains region of the United States. The results support the hypothesis that the most adverse impacts on net returns distributions tend to occur in the areas with the poorest resource endowments and when mitigating effects of CO₂ fertilization and adaptation are absent. We find that relative and absolute measures of vulnerability depend on complex interactions between climate change, CO₂ level, adaptation, and economic conditions such as relativeoutput prices. The relationship between relative vulnerability and resource endowments varies with assumptions about climate change, adaptation, and economic conditions. Vulnerability measured with respect to an absolute threshold is inversely related to resource endowments in all cases investigated.     

Assessment of Dynamic Downscaling of the Extreme Rainfall over East Asia Using a Regional Climate Model

This study investigates the capability of the dynamic downscaling method (DDM) in an East Asian climate study for June 1998 using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research non-hydrostatic Mesoscale Model (MM5).Sensitivity experiments show that MM5 results at upper atmospheric levels cannot match reanalyses data,but the results show consistent improvement in simulating moisture transport at low levels.The downscaling ability for precipitation is regionally dependent.During the monsoon season over the Yangtze River basin and the pre-monsoon season over North China,the DDM cannot match observed precipitation.Over Northwest China and the Tibetan Plateau (TP),where there is high topography,the DDM shows better performance than reanalyses.Simulated monsoon evolution processes over East Asia,however,are much closer to observational data than reanalyses.The convection scheme has a substantial impact on extreme rainfall over the Yangtze River basin and the pre-monsoon over North China,but only a marginal contribution for Northwest China and the TP.Land surface parameterizations affect the locations and pattern of rainfall bands.The 10-day re-initialization in this study shows some improvement in simulated precipitation over some sub-regions but with no obvious improvement in circulation.The setting of the location of lateral boundaries (LLB) westward improves performance of the DDM.Including the entire TP in the western model domain improves the DDM performance in simulating precipitation in most sub-regions.In addition,a seasonal simulation demonstrates that the DDM can also obtain consistent results,as in the June case,even when another two months consist of no strong climate/weather events.     

利用简单生物圈模式SiB2模拟锡林浩特草原地表湍流通量

利用简单生物圈模式SiB2模拟了2007年7月1日至9月30日期间锡林浩特草原的地表能量分配、CO2通量、地表有效辐射温度和土壤湿度.采用锡林浩特国家气候观象台野外试验基地实地测量资料确定SiB2所需要的参数和初始值后,由该资料中30 min一次的太阳短波辐射、大气长波辐射、水汽压、气温、水平风速和降水驱动SiB2,最...     

Evaluation of Simulated CO_2 Concentrations from the CarbonTracker-Asia Model Using In-situ Observations over East Asia for 2009–2013

The CarbonTracker(CT) model has been used in previous studies for understanding and predicting the sources, sinks, and dynamics that govern the distribution of atmospheric CO_2 at varying ranges of spatial and temporal scales. However, there are still challenges for reproducing accurate model-simulated CO_2 concentrations close to the surface, typically associated with high spatial heterogeneity and land cover. In the present study, we evaluated the performance of nested-grid CT model simulations of CO_2 based on the CT2016 version through comparison with in-situ observations over East Asia covering the period 2009–13. We selected sites located in coastal, remote, inland, and mountain areas. The results are presented at diurnal and seasonal time periods. At target stations, model agreement with in-situ observations was varied in capturing the diurnal cycle. Overall, biases were less than 6.3 ppm on an all-hourly mean basis, and this was further reduced to a maximum of 4.6 ppm when considering only the daytime. For instance, at Anmyeondo, a small bias was obtained in winter, on the order of 0.2 ppm. The model revealed a diurnal amplitude of CO_2 that was nearly flat in winter at Gosan and Anmyeondo stations, while slightly overestimated in the summertime. The model's performance in reproducing the diurnal cycle remains a challenge and requires improvement. The model showed better agreement with the observations in capturing the seasonal variations of CO_2 during daytime at most sites, with a correlation coefficient ranging from 0.70 to 0.99. Also, model biases were within-0.3 and 1.3 ppm, except for inland stations(7.7 ppm).     

Assessment of Indian summer monsoon simulation by Community Atmosphere Model (CAM3)

Seasonal prediction of Indian Summer Monsoon (ISM) has been attempted for the current year 2011 using Community Atmosphere Model (CAM) developed at the National Centre for Atmospheric Research (NCAR). First, 30?years of model climatology starting from 1981 to 2010 has been generated to capture the variability of ISM over the Indian region using 30 seasonal simulations. The simulated model climatology has been validated with different sets of observed climatology, and it was observed that the simulated climatological rainfall is affected by model bias. Subsequently, a bias correction procedure using the Tropical Rainfall Measuring Mission (TRMM) 3B43 rainfall has been proposed. The bias-corrected rainfall climatology shows both spatial and temporal variability of ISM satisfactorily. Further, four sets of 10-member ensemble simulations of ISM 2009 and 2010 have been performed in hindcast mode using observed sea surface temperature (SST) and persistence of April SST anomaly, and it has been found that the bias-corrected model rainfall captures the seasonal variability of ISM reasonably well with some discrepancies in these two contrasting monsoon years. With this positive background, the seasonal prediction of ISM 2011 has been carried out in forecast mode with the assumption of persistence of May SST anomaly from June through September 2011. The model assessment shows an 11% deficiency in All-India Rainfall (AIR) of ISM 2011. In particular, the monthly accumulated rains are predicted to be 101% (17.6?cm), 86% (24.3?cm), 83% (21.0?cm) and 95% (15.5?cm) of normal AIR for the months of June, July, August and September, respectively.     

Modelling Sea Surface Temperature (SST) in the Hudson Bay Complex Using Bulk Heat Flux Parameterization: Sensitivity to Atmospheric Forcing,and Model Resolution

ABSTRACT

Sea surface temperature (SST) from four Nucleus for European Modelling of the Ocean (NEMO) model simulations is analyzed to study the bulk flux parameterization to compute SST over the Hudson Bay Complex (HBC) for the summer months (August and September) from 2002 to 2009. The NEMO simulation was forced with two atmospheric forcing sets with different resolutions: the Coordinated Ocean-ice Reference Experiment, version 2 (COREv2), as the lower resolution and the Canadian Meteorological Centre’s Global Deterministic Prediction System Reforecasts (CGRF) as the higher resolution. The CGRF forcing is also implemented in the third and fourth runs using different runoff data and different NEMO resolutions (1/12° versus 1/4°). Results show that all four modelled SSTs followed observed SST patterns, with regional differences in SST bias between simulations with different atmospheric forcing. The SST differences are small between simulations forced with the same atmospheric forcing but with different model resolution or runoff. This implies that the model resolution and runoff have a small effect on the simulated SST in the HBC. Moreover, to better capture the effect of near-surface temperature (T_air) on simulated SST, we conducted three analyses using the Haney flux linearization formula. Results from these assessments did not indicate any direct influence on the model-simulated SSTs by T_air. Looking at the heat flux as a signature for SST showed that both averaged spatial distribution and time series of net heat flux produced by the three CGRF forcing simulations were higher than the net heat flux generated by the CORE 2 simulation. This was generally true for all four components of the total heat flux (sensible, latent, shortwave, and longwave) individually as well. Total heat flux in summer is governed by the shortwave heat flux, with values up to 120?W?m^?2 in August, and the longwave heat flux is the main contributor to the total heat flux differences. These heat flux differences lead to corresponding colder model SSTs for the CGRF runs and warmer SSTs for the CORE 2 simulations.     

A Numerical Study of Sensitivity of the Physical Dissipative Technique to Precipitation Parameterization in a Mesoscale Model

1. IntroductionRecently, the improvement of accuracy in the out-puts of a numerical mesoscale model by the physi-cal dissipative technique is reached (Liu et al., 2002;Liu and Liu, 2003). The effect of improvement ofthis technique differs not only from model to model,but from scheme to scheme of parameterization em-ployed in the same model. The rapid developmentof the computer technology makes possible the com-plicated numerical experiments by a model with highresolution and multiple domains …     

The sensitivity of ground surface temperature prediction to soil thermal properties Using the Simple Biosphere Model (SiB2)

Using the Simple Biosphere Model (SiB2), soil thermal properties (STP) were examined in a Tibetan prairie during the monsoon period to investigate ground surface temperature prediction. We improved the SiB2 model by incorporating a revised force-restore method (FRM) to take the vertical heterogeneity of soil thermal diffusivity (k) into account. The results indicate that (1) the revised FRM alleviates daytime overestimation and nighttime underestimation in modeled ground surface temperature (T_g), and (2) its role in little rainfall events is significant because the vertical gradient of k increases with increasing surface evaporation. Since the original formula of thermal conductivity (λ) in the SiB2 greatly underestimates soil thermal conductivity, we compared five algorithms of λ involving soil moisture to investigate the cause of overestimation during the day and underestimation at night on the basis of the revised FRM. The results show that (1) the five algorithms significantly improve T_g prediction, especially in daytime, and (2) taking one of these five algorithms as an example, the simulated T_g values in the daytime are closer to the field measurements than those in the nighttime. The differences between modeled T_g and field measurements are mostly within the margin of error of ±2 K during 3 August to 4 September 1998.     

Simulation and Analysis of China Climate Using Two-Way Interactive Atmosphere-Vegetation Model （RIEMS-AVIM）

In this paper, an Atmosphere-Vegetation Interaction Model （AVIM） is coupled to the Regional Integrated Environment Model System （RIEMS）, and a 10-year integration for China is performed using the RIEMS-AVIM. The analysis of the results of the 10-year integration shows that the characters of the spatial distributions of temperature and precipitation over China are well simulated. The patterns of simulated surface sensible and latent heat fluxes match well with the spatial climatological atlas： the values of winter surface sensible and latent heat fluxes are both lower than climatological values over the whole country. Summer surface sensible heat flux is higher than climatological values in western China and lower in eastern China, while summer surface latent heat flux is higher than climatological values in the eastern and lower in the western. Seasonal variations of simulated temperature and precipitation of RIMES-AVIM agree with those of the observed. Simulated temperature is lower than the observed in the Tibetan Plateau and Northwest China for the whole year, slightly lower in the remaining regions in winter, but consistent with the observed in summer. The simulated temperature of RIEMS-AVIM is higher in winter and lower in summer than that of RIEMS, which shows that the simulated temperature of RIEMS-AVIM is closer to the observed value. Simulated precipitation is excessive in the first half of the year, but consistent with the observed in the second half of the year. The simulated summer precipitation of RIEMS-AVIM has significant improvement compared to that of RIEMS, which is less and closer to the observed value. The interannual variations of temperature and precipitation are also fairly well simulated, with temperature simulation being superior to precipitation simulation. The interannual variation of simulated temperature is significantly correlated with the observed in Northeast China, the Transition Region, South China, and the Tibetan Plateau, but the correlation between precipitation simu     

一维辐射-对流模式对云辐射强迫的数值模拟研究

利用一维辐射－对流气候模式, 详细研究了云量、云光学厚度以及云高等要素的变化对大气顶和地面太阳短波辐射和红外长波辐射通量以及云的辐射强迫的影响, 给出了计算这些物理量的经验拟合公式。结果表明, 云具有极为重要的辐射－气候效应。云量、云光学厚度以及云高即使只有百分之几的变化, 所带来的辐射强迫也可以与大气二氧化碳浓度加倍所产生的辐射强迫（3.75 W/m2）相比拟。例如, 当分别给它们+3%的扰动时, 即取云量变化0.015, 云光学厚度变化0.27, 以及云高变化0.15 km时（在实际的地球大气中, 这种尺度的变化是完全可能发生的）, 那么,可以得到地气系统的太阳短波辐射强迫-3.10 W/m2以及红外长波辐射强迫-1.77 W/m2, 二者之和为-4.78 W/m2, 已经完全可以抵消大气二氧化碳浓度加倍所产生的辐射强迫。但是, 当云量、云光学厚度以及云高向相反方向产生类似扰动时, 所产生的辐射强迫可能极大地放大二氧化碳浓度增加所产生的增强温室效应。因此, 研究结果揭示出, 不管是为了解释过去的气候变化, 还是预测未来的气候变化, 亟待加强在一个变化了的气候环境（例如地面温度升高）下, 云将发生何种变化的研究。