基于WRF模式的京津冀地区地表大气CO2浓度的模拟研究

在“双碳”目标背景下，从国家层面到地方层面，区域、城市、行业企业都在制定和实施双碳目标行动计划。CO₂模拟因其客观性和高时空分辨率等优势，在城市碳排放研究中深受重视。本研究以京津冀地区为研究区域，采用Picarro仪器高精度观测的2019—2020年CO₂数据，利用WRF模式进行CO₂传输模拟，分析了CO₂浓度变化的季节特征，评估了模式在城区中心、城郊及背景3个观测站点的模拟效果，并对边界层高度及化石燃料碳排放等可能影响CO₂浓度的因素进行了研究。3个观测站点分别为北京中国科学院大气物理研究所325 m气象塔观测站（北京站）、河北香河观测站（香河站）和上甸子区域本底观测站（上甸子站）。模拟结果表明：上甸子站优于香河站，香河站优于北京站，在冬季尤其明显；CO₂浓度的高值区主要分布在城区、电厂和工业区，尤其是唐山、石家庄和邯郸地区，大量交通、工业排放导致CO₂浓度明显上升，且高值区的范围在冬季最大；就日平均变化和日变化而言，边界层高度与CO₂浓度存在相反变化趋势；3个站点的化石燃料碳排放（FFECO2）与近地面总CO₂浓度存在正相关关系，冬春季的相关性高于夏秋季，且FFECO2的占比从大到小依次为北京站、香河站、上甸子站；CO₂传输模拟的不确定性存在空间差异和季节变化。     

海洋对人为CO2吸收的三维模式研究

文中用包含海洋化学过程和一个简单生物过程的三维碳循环模式模拟了海洋对大气CO2 的吸收 ,并分析了碳吸收的纬度分布。模拟工业革命以来海洋对大气 CO2 的吸收表明 :海洋碳吸收再加上大气 CO2 的增加只占由化石燃料燃烧、森林砍伐和土地利用的变化而释放到大气中的 CO2 的 2 /3。1 980～ 1 989年期间海洋年平均吸收 2 .0 5Gt C。海洋人为 CO2 的吸收有明显的纬度特征。模式计算的海洋 CO2 的吸收在总量与纬度分布上与观测结果比较相符。     

东亚地区二氧化碳体积分数变化特征

利用2004年以来东亚地区10个本底观测站大气φ(CO₂)观测资料,分析了各站大气φ(CO₂)的变化特征及其各站之间的差异,讨论了下垫面特征、源汇作用等对φ(CO₂)变化的影响.结果表明:10个本底站大气月均φ(CO₂)有明显的季节变化,高值多出现在冬春等寒冷季节,而低值则多出现在6—9月,属于北半球的夏季;大气φ(CO₂)日变化趋势较为一致,15时(当地时间)前后达到全天最低,随后φ(CO₂)升高,并在日落后继续积累,至清晨7时(当地时间)前后达到全天最高,之后φ(CO₂)随着太阳辐射的增强而逐渐降低,且平均φ(CO₂)水平与下垫面植被量成反比,φ(CO₂)日变化的幅度与下垫面植被量成反比.作为全球基准站之一的瓦里关山站,2004—2008年φ(CO₂)年均值逐年增加,年增长率为2.28×10^-6/a.     

锡林浩特草原CO2通量特征及其影响因素分析

利用锡林浩特国家气候观象台开路涡度相关系统、辐射土壤观测系统,测得的长期连续通量观测数据,对锡林浩特草原2009—2011年期间的CO₂通量观测特征进行了分析。结果表明:CO₂通量存在明显的年际、季节和日变化特征。3 a中NEE年际变率达到200 g·m^-2,季节变率最大达到460 g·m^-2,日变化幅度生长季最大达到0.25 mg·m^-2·s^-1。通过不同时间尺度碳通量与温度、水分、辐射等环境因子的分析,认为CO₂通量日变化主要受温度和光合有效辐射影响,而季节变化和年变化主要受降水和土壤含水量的影响。降水强度及时间分布是制约牧草CO₂吸收的关键因素,大于15%的土壤含水量有利于促进牧草生长。     

江苏地区二氧化碳浓度时空分布特征分析

利用瓦里关和上甸子大气本底站观测的月平均CO₂浓度数据对GOSAT卫星反演的CO₂浓度数据进行验证,结果表明GOSAT产品与台站观测数据有较好的一致性.利用2009年6月—2011年5月GOSAT反演的CO₂浓度数据,分析了江苏地区CO₂浓度的时空变化特征,结果表明:1)975 hPa高度层CO₂浓度高于850 hPa高度层,CO₂浓度的水平变化要小于垂直变化;2)在季节变化上,CO₂浓度冬季最高,夏季最低,这可能与植被光合作用的强弱变化有关;比较前后两年的CO₂浓度数据,夏季和秋季的增速较快,冬季和春季的增速较慢;3)在日变化上,发现徐州和南京站02时CO₂浓度最高,14时CO₂浓度最低,这可能也与植被光合作用的强弱有关.     

山西省城市大气CO2本底筛分对比及特征分析

基于典型城市站太原站2018年3月—2019年2月的大气CO₂在线观测资料，利用筛分法（Meteorological filtering method，MET）和黑碳示踪法（Black Carbon tracer，BC）进行本底/非本底的筛分，得到了本底浓度的变化特征。结果表明，太原大气CO₂浓度季均值冬季最高，夏季最低；不同季节呈"单峰型"日变化特征，日振幅均在26.0×10^-6以上；4个季节CO₂浓度与地面风速存在显著负相关关系；CO₂浓度抬升区域主要受当地工业布局的影响，最大抬升幅度在秋季达17.4×10^-6；使用气象筛分法（MET）得到年均本底浓度为（431.4±19.9）×10^-6，人为排放等对其影响为23.5×10^-6，年振幅比同纬度其它本底站大，为34.5×10^-6；黑碳示踪法（BC）得到冬季季均本底浓度为（445.0±22.9）×10^-6，比MET筛分法得到的季均值高0.8×10^-6，两种筛分法得到的CO₂浓度变化趋势一致。     

大气CO2富集对根际NaCl盐渍的人参果植株干物质生产和水分利用的影响

对单株砂培盆栽的半木质化枝条扦插生根的一月龄人生果(Solanum muricatum Ait.)栽培品种"Xotus",每周浇两次200mL NaCl质量浓度分别为0mg·L^-1和25mg·L^-1的Hoagland营养液处理2个月,第二个月在控制空气CO₂体积分数为(350±10)×10^-6、(700±10)×10^-6和(1050±10)×10^-6的植物生长箱内试验。结果表明,人参果植株干物质生产量和耗水量受根际NaCl盐渍而下降,又随大气CO₂升高而增加。根际NaCl盐渍能增大植株叶片蒸腾系数、根/冠比和干物质向枝干和根部分配的比例及积累量,降低根系吸收水分的效率和耗水量。升高大气CO₂能促进叶片发育及干物质向地上部其他器官和地下部组织分配,增加总叶面积、比叶干重和各种器官中干物质增长量,提高干物质生产率和水分利用率。根际经25mg·L^-1NaCl盐渍处理的植株,总干物质增长量和水分利用率相应下降50%～54%和24%～37%;与350×10^-6CO₂的处理的植株相比,700×10^-6及1050×10^-6CO₂的处理分别使这两项指标提高到79%～106%和61%～88%以及133%～189%和99%～142%。大气CO₂富集能改善受NaCl盐渍的植株干物质生产力、提高水分利用率。根际NaCl盐渍和大气CO₂富集对人参果植株干物质生产和水分利用有生物互作效应。它们的共同作用会促进植株干物质的增长及叶片中合成的干物质向其他器官分配,提高干物质生产率和水分利用率,同时减少总叶面积、枝条和根系干重、根系吸水效率、植株耗水量和叶片蒸腾系数。因此,全球大气CO₂富集将有利于该作物的干物质生产和水分利用。     

[Bmin][BF4]+AMP复合溶液捕集温室气体CO2

采用基于离子液体[Bmin][BF₄]+AMP作为捕集CO₂的复合溶液,在膜吸收-热再生循环装置上,研究了该复合溶液捕集CO₂的过程和传质性能;通过阻力层传质模型,比较了预测值与实验值.结果表明：在相同条件和较高负载下,复合溶液具有较高的传递推动力和更高的传质系数;模型预测值和实验值符合较好,平均误差为12.8%.实验证明复合溶液的传质性能优于单一溶液.     

大气CO2浓度升高及气候变化对作物冠层光合影响的数值模拟

利用美国Licor-6200光合作用测定仪,对黄淮海地区代表性冬小麦品种鲁麦23号叶片光合作用速率进行了较为全面的测定,分别确定了冬小麦叶片光—光合作用响应曲线和CO₂—光合作用响应曲线,在此基础上,建立了叶片光合作用模式,并进而建立了一个具有瞬时时间尺度,空间积分为叶片尺度的冬小麦冠层模式,利用模式分别分析了大气中CO₂浓度升高和温度变化对冠层光合作用的不同影响,并在此基础上进一步进行了综合数值分析。单因子分析表明:晴天状况下,冠层光合速率随CO₂浓度升高而上升,当CO₂浓度由330×10^-6上升至660×10^-6时,冠层光合日总量可增加19.7%;冠层光合速率随辐射增加而增大,辐射量增加10.0%,冠层光合日总量可增加6.7%;冠层光合速率随温度升高而下降,温度升高1℃,冠层光合日总量减少2.9%。多因子综合数值分析表明:在辐射量较大的气候背景下,冠层光合日总量对温度和CO₂变化响应更加敏感。本文的实测数据为研究气候变化对中国农业影响提供了最基本的可靠模型参数,冠层光合模型为未来改进作物模型提供了理论基础。     

CO2浓度渐增对气温影响的敏感性试验

使用辐射对流模式,研究了中纬度冬季气温对于CO₂浓度变化的敏感性。结果表明:气温变幅随CO₂浓度渐增呈现先快后慢的非线性特征;气温变幅具有一定的稳定性。     

A SIMULATION OF CO2 UPTAKE IN A THREE DIMENSIONAL OCEAN CARBON CYCLE MODEL*

A three-dimensional ocean carbon cycle model which is a general circulation model coupled with simple biogeochemical processes is used to simulate CO₂ uptake by the ocean.The OGCM used is a modified version of the Geophysical Fluid Dynamics Laboratory modular ocean model(MOM2).The ocean chemistry and a simple ocean biota model are included.Principal variablesare total CO₂,alkalinity and phosphate.The vertical profile of POC flux observed by sediment traps is adopted,the rain ratio,a ratio of production rate of calcite against that of POC,and the bio-production efficiency should be 0.06 and 2 per year,separately.The uptake of anthropogenic CO₂ by the ocean is studied.Calculated oceanic uptake of anthropogenic CO₂ during the 1980s is 2.05×10¹⁵g(Pg)per year.The regional distributions of global oceanic CO₂ are discussed.     

Estimates of anthropogenic CO<Subscript>2</Subscript> uptake in a global ocean model

A global ocean general circulation model (L30T63) is employed to study the uptake and distribution of anthropogenic CO₂ in the ocean. A subgrid-scale mixing scheme called GM90 is used in the model. There are two main GM90 parameters including isopycnal diffusivity and skew (thickness) diffusivity. Sensitivities of the ocean circulation and the redistribution of dissolved anthropogenic CO₂ to these two parameters are examined. Two runs estimate the global oceanic anthropogenic CO₂ uptake to be 1.64 and 1.73 Pg C yr^-1 for the 1990s, and that the global ocean contained 86.8 and 92.7 Pg C of anthropogenic CO₂ at the end of 1994, respectively. Both the total inventory and uptake from our model are smaller than the data-based estimates. In this presentation, the vertical distributions of anthropogenic CO₂ at three meridional sections are discussed and compared with the available data-based estimates. The inventory in the individual basins is also calculated. Use of large isopycnal diffusivity can generally improve the simulated results, including the exchange flux, the vertical distribution patterns, inventory, storage, etc. In terms of comparison of the vertical distributions and column inventory, we find that the total inventory in the Pacific Ocean obtained from our model is in good agreement with the data-based estimate, but a large difference exists in the Atlantic Ocean, particularly in the South Atlantic. The main reasons are weak vertical mixing and that our model generates small exchange fluxes of anthropogenic CO₂ in the Southern Ocean. Improvement in the simulation of the vertical transport and sea ice in the Southern Ocean is important in future work.     

Ocean dynamics determine the response of oceanic CO2 uptake to climate change

The increase of atmospheric CO₂ concentrations due to anthropogenic activities is substantially damped by the ocean, whose CO₂ uptake is determined by the state of the ocean, which in turn is influenced by climate change. We investigate the mechanisms of the ocean’s carbon uptake within the feedback loop of atmospheric CO₂ concentration, climate change and atmosphere/ocean CO₂ flux. We evaluate two transient simulations from 1860 until 2100, performed with a version of the Max Planck Institute Earth System Model (MPI-ESM) with the carbon cycle included. In both experiments observed anthropogenic CO₂ emissions were prescribed until 2000, followed by the emissions according to the IPCC Scenario A2. In one simulation the radiative forcing of changing atmospheric CO₂ is taken into account (coupled), in the other it is suppressed (uncoupled). In both simulations, the oceanic carbon uptake increases from 1 GT C/year in 1960 to 4.5 GT C/year in 2070. Afterwards, this trend weakens in the coupled simulation, leading to a reduced uptake rate of 10% in 2100 compared to the uncoupled simulation. This includes a partial offset due to higher atmospheric CO₂ concentrations in the coupled simulation owing to reduced carbon uptake by the terrestrial biosphere. The difference of the oceanic carbon uptake between both simulations is primarily due to partial pressure difference and secondary to solubility changes. These contributions are widely offset by changes of gas transfer velocity due to sea ice melting and wind changes. The major differences appear in the Southern Ocean (?45%) and in the North Atlantic (?30%), related to reduced vertical mixing and North Atlantic meridional overturning circulation, respectively. In the polar areas, sea ice melting induces additional CO₂ uptake (+20%).     

Factors influencing anthropogenic carbon dioxide uptake in the North Atlantic in models of the ocean carbon cycle

The uptake and storage of anthropogenic carbon in the North Atlantic is investigated using different configurations of ocean general circulation/carbon cycle models. We investigate how different representations of the ocean physics in the models, which represent the range of models currently in use, affect the evolution of CO₂ uptake in the North Atlantic. The buffer effect of the ocean carbon system would be expected to reduce ocean CO₂ uptake as the ocean absorbs increasing amounts of CO₂. We find that the strength of the buffer effect is very dependent on the model ocean state, as it affects both the magnitude and timing of the changes in uptake. The timescale over which uptake of CO₂ in the North Atlantic drops to below preindustrial levels is particularly sensitive to the ocean state which sets the degree of buffering; it is less sensitive to the choice of atmospheric CO₂ forcing scenario. Neglecting physical climate change effects, North Atlantic CO₂ uptake drops below preindustrial levels between 50 and 300 years after stabilisation of atmospheric CO₂ in different model configurations. Storage of anthropogenic carbon in the North Atlantic varies much less among the different model configurations, as differences in ocean transport of dissolved inorganic carbon and uptake of CO₂ compensate each other. This supports the idea that measured inventories of anthropogenic carbon in the real ocean cannot be used to constrain the surface uptake. Including physical climate change effects reduces anthropogenic CO₂ uptake and storage in the North Atlantic further, due to the combined effects of surface warming, increased freshwater input, and a slowdown of the meridional overturning circulation. The timescale over which North Atlantic CO₂ uptake drops to below preindustrial levels is reduced by about one-third, leading to an estimate of this timescale for the real world of about 50 years after the stabilisation of atmospheric CO₂. In the climate change experiment, a shallowing of the mixed layer depths in the North Atlantic results in a significant reduction in primary production, reducing the potential role for biology in drawing down anthropogenic CO₂.     

Uptake and Storage of Anthropogenic CO2 in the Pacific Ocean Estimated Using Two Modeling Approaches

A basin-wide ocean general circulation model(OGCM) of the Pacific Ocean is employed to estimate the uptake and storage of anthropogenic CO 2 using two different simulation approaches.The simulation(named BIO) makes use of a carbon model with biological processes and full thermodynamic equations to calculate surface water partial pressure of CO 2,whereas the other simulation(named PTB) makes use of a perturbation approach to calculate surface water partial pressure of anthropogenic CO 2.The results from the two simulations agree well with the estimates based on observation data in most important aspects of the vertical distribution as well as the total inventory of anthropogenic carbon.The storage of anthropogenic carbon from BIO is closer to the observation-based estimate than that from PTB.The Revelle factor in 1994 obtained in BIO is generally larger than that obtained in PTB in the whole Pacific,except for the subtropical South Pacific.This,to large extent,leads to the difference in the surface anthropogenic CO 2 concentration between the two runs.The relative difference in the annual uptake between the two runs is almost constant during the integration processes after 1850.This is probably not caused by dissolved inorganic carbon(DIC),but rather by a factor independent of time.In both runs,the rate of change in anthropogenic CO 2 fluxes with time is consistent with the rate of change in the growth rate of atmospheric partial pressure of CO 2.     

Learning about the ocean carbon cycle from observational constraints and model simulations of multiple tracers

A key question in studies of the potential for reducing uncertainty in climate change projections is how additional observations may be used to constrain models. We examine the case of ocean carbon cycle models. The reliability of ocean models in projecting oceanic CO₂ uptake is fundamentally dependent on their skills in simulating ocean circulation and air–sea gas exchange. In this study we demonstrate how a model simulation of multiple tracers and utilization of a variety of observational data help us to obtain additional information about the parameterization of ocean circulation and air–sea gas exchange, relative to approaches that use only a single tracer. The benefit of using multiple tracers is based on the fact that individual tracer holds unique information with regard to ocean mixing, circulation, and air–sea gas exchange. In a previous modeling study, we have shown that the simulation of radiocarbon enables us to identify the importance of parameterizing sub-grid scale ocean mixing processes in terms of diffusive mixing along constant density surface (isopycnal mixing) and the inclusion of the effect of mesoscale eddies. In this study we show that the simulation of phosphate, a major macronutrient in the ocean, helps us to detect a weak isopycnal mixing in the upper ocean that does not show up in the radiocarbon simulation. We also show that the simulation of chlorofluorocarbons (CFCs) reveals excessive upwelling in the Southern Ocean, which is also not apparent in radiocarbon simulations. Furthermore, the updated ocean inventory data of man-made radiocarbon produced by nuclear tests (bomb ¹⁴C) enable us to recalibrate the rate of air–sea gas exchange. The progressive modifications made in the model based on the simulation of additional tracers and utilization of updated observational data overall improve the model’s ability to simulate ocean circulation and air–sea gas exchange, particularly in the Southern Ocean, and has great consequence for projected CO₂ uptake. Simulated global ocean uptake of anthropogenic CO₂ from pre-industrial time to the present day by both previous and updated models are within the range of observational-based estimates, but with substantial regional difference, especially in the Southern Ocean. By year 2100, the updated model estimated CO₂ uptake are 531 and 133 PgC (1PgC?=?10¹⁵ gram carbon) for the global and Southern Ocean respectively, whereas the previous version model estimated values are 540 and 190 PgC.     

Can ocean iron fertilization mitigate ocean acidification?

Ocean iron fertilization has been proposed as a method to mitigate anthropogenic climate change, and there is continued commercial interest in using iron fertilization to generate carbon credits. It has been further speculated that ocean iron fertilization could help mitigate ocean acidification. Here, using a global ocean carbon cycle model, we performed idealized ocean iron fertilization simulations to place an upper bound on the effect of iron fertilization on atmospheric CO₂ and ocean acidification. Under the IPCC A2 CO₂ emission scenario, at year 2100 the model simulates an atmospheric CO₂ concentration of 965 ppm with the mean surface ocean pH 0.44 units less than its pre-industrial value of 8.18. A globally sustained ocean iron fertilization could not diminish CO₂ concentrations below 833 ppm or reduce the mean surface ocean pH change to less than 0.38 units. This maximum of 0.06 unit mitigation in surface pH change by the end of this century is achieved at the cost of storing more anthropogenic CO₂ in the ocean interior, furthering acidifying the deep-ocean. If the amount of net carbon storage in the deep ocean by iron fertilization produces an equivalent amount of emission credits, ocean iron fertilization further acidifies the deep ocean without conferring any chemical benefit to the surface ocean.     

Oceanic transport and storage of carbon emissions

Using a global carbon cycle model (GLOCO) that considers seven terrestrial biomes, surface and deep ocean layers based on the HILDA model and a single mixed atmosphere, we analyzed the response of atmospheric CO₂ concentration and oceanic DIC and DOC depth profiles to additions of carbon to the atmosphere and ocean. The rate of transport of carbon to the deepest oceanic layers is rather insensitive to the atmosphereic-ocean surface gas exchange coefficient over a wide range, hence discrepancies between researchers on the precise global average value of this coefficient do not significantly affect predictions of atmospheric response to anthropogenic inputs. Upwelling velocity, on the other hand, amplifies oceanic response by increasing primary production in the upper ocean layers, resulting in a larger flux into DOC and sediments and increased carbon storage; experiments to reduce the uncertainty in this parameter would be valuable.The location of the carbon addition, whether it is released in the atmosphere or in the middle of the oceanic thermocline, has a significant impact on the maximum atmospheric CO₂ concentration (pCO₂) subsequently reached, suggesting that oceanic burial of a significant fraction of carbon emissions (e.g. via clathrate hydrides) may be an important management option for limiting pCO₂ buildup. Our analysis indicates that the effectiveness of ocean burial decreases asymptotically below about 1000 m depth. With a constant emissions scenario (at 1990 levels), pCO₂ at year 2100 is reduced from 501 ppmv considering all emissions go to the atmosphere, to 422 ppmv with ocean burial at a depth of 1000 m of 50% of the fossil fuel emissions. An alternative scenario looks at stabilizing pCO₂ at 450 ppmv; with no ocean burial of fossil fuel emissions, the rate of emissions has to be cut drastically after the year 2010, whereas oceanic burial of 2 GtC/yr allows for a smoother transition to alternative energy sources.     

A simple carbon cycle representation for economic and policy analyses

Integrated Assessment Models (IAMs) that couple the climate system and the economy require a representation of ocean CO₂ uptake to translate human-produced emissions to atmospheric concentrations and in turn to climate change. The simple linear carbon cycle representations in most IAMs are not however physical at long timescales, since ocean carbonate chemistry makes CO₂ uptake highly nonlinear. No linearized representation can capture the ocean’s dual-mode behavior, with initial rapid uptake and then slow equilibration over ∽10,000 years. In a business-as-usual scenario followed by cessation of emissions, the carbon cycle in the 2007 version of the most widely used IAM, DICE (Dynamic Integrated model of Climate and the Economy), produces errors of ∽2^°C by the year 2300 and ∽6^°C by the year 3500. We suggest here a simple alternative representation that captures the relevant physics and show that it reproduces carbon uptake in several more complex models to within the inter-model spread. The scheme involves little additional complexity over the DICE model, making it a useful tool for economic and policy analyses.