The Role of Land–sea Distribution and Orography in the Asian Monsoon. Part I: Land–sea Distribution

A number of AGCM simulations were performed by including various land–sea distributions (LSDs), such as meridional LSDs, zonal LSDs, tropical large-scale LSDs, and subcontinental-scale LSDs, to identify their effects on the Asian monsoon. In seven meridional LSD experiments with the continent/ocean located to the north/south of a certain latitude, the LSDs remain identical except the southern coastline is varied from 40 ° to 4 ° N in intervals of 5.6° . In the experiments with the coastline located to the n...     

坡地坡向短波辐射参数化对不同天气过程的影响

为了改进太阳短波辐射参数化,运用考虑了坡地坡向短波辐射效应(SLOPE)的非静力中尺度模式GRAPES(全球/区域同化和预报系统),模拟和讨论了坡地坡向短波辐射效应在不同模式分辨率情况下对中国不同天气过程的影响.数值试验表明:(1)当水平分辨率较低且坡地平缓时,通常可忽略坡地辐射效应,但当水平分辨率较高且地形陡峭起伏时,则不能忽略;(2)在高分辨率(3 或6 km格距,下同)的情况下, 降水的增加和减少与坡地坡向引起的地表短波辐射(GSW)的减少和增加相对应,降水量的增减量大部分均为-5-5 mm;(3)在高分辨率的情况下,地表温度与地表热通量之间有较好的相关性,且大都发生在地形复杂的多山地区;(4)坡地坡向短波辐射效应引起的GSW、降水量、地表温度和地表热通量等要素的变化除了在地形复杂的多山地区比较明显之外,在其他地区也存在.这是由于考虑了坡度和坡向的作用后,影响了大气环流的变化,随着积分时间的增加,其他地区上述物理量也相应地存在一定的变化;(5)坡地坡向对短波辐射的作用,在降水量较小,云量较少的天气过程中,可以更真实地得到反映.因此,在地形复杂和水平分辨率较高情况下,需要考虑坡度坡向作用.     

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.     

Summary of Recent Climate Change Studies on the Carbon and Nitrogen Cycles in the Terrestrial Ecosystem and Ocean in China

This article reviews recent advances over the past 4 years in the study of the carbon-nitrogen cycling and their relationship to climate change in China. The net carbon sink in the Chinese terrestrial ecosystem was 0.19-0.26 Pg C yr-1 for the 1980s and 1990s. Both natural wetlands and the rice-paddy regions emitted 1.76 Tg and 6.62 Tg of CH 4 per year for the periods 1995-2004 and 2005-2009, respectively. China emitted～1.1 Tg N 2 O-N yr-1 to the atmosphere in 2004. Land soil contained～8.3 Pg N. The excess nitrogen stored in farmland of the Yangtze River basin reached 1.51 Tg N and 2.67 Tg N in 1980 and 1990, respectively. The outer Yangtze Estuary served as a moderate or significant sink of atmospheric CO 2 except in autumn. Phytoplankton could take up carbon at a rate of 6.4 ×10 11 kg yr-1 in the China Sea. The global ocean absorbed anthropogenic CO 2 at the rates of 1.64 and 1.73 Pg C yr-1 for two simulations in the 1990s. Land net ecosystem production in China would increase until the mid-21st century then would decrease gradually under future climate change scenarios. This research should be strengthened in the future, including collection of more observation data, measurement of the soil organic carbon (SOC) loss and sequestration, evaluation of changes in SOC in deep soil layers, and the impacts of grassland management, carbon-nitrogen coupled effects, and development and improvement of various component models and of the coupled carbon cycle-climate model.     

干对流调整对区域气候模拟效果的影响

利用干对流发生时大气层之间质量交换应满足守恒性原理, 改进了p-σ区域气候模式中的干对流调整方案。该方案同时调整温度、比湿和风场。利用1979~1995年NCEP/NCAR再分析资料月平均场作为初始场和侧边界强迫, 模拟1月和7月的气候特征,并用t检验和F检验方法检验敏感试验和控制试验模拟结果差异的显著性。结果表明, 无论是1月还是7月, 敏感试验与控制试验出现干对流调整的区域均一致, 但敏感试验各区域发生干对流调整的次数均比控制试验多。7月各个物理量场的差异均比1月显著。两试验模拟7月比湿场和降水量场的均值差异不明显, 而方差差异比较显著;温度场和风场的均值差异和方差差异均比较显著。敏感试验在20°N~35°N纬度带内对7月500 hPa风场的模拟有了比较明显的改进。在对7月总降水量场的模拟方面, 敏感试验在新疆北部、内蒙古中部呼和浩特一带、吉林东部以及湖北和广东地区有比较好的模拟效果, 基本消除了控制试验中的虚假大值区。     

浑善达克沙地近50年来风沙活动的湖泊记录

干旱、半干旱地区湖泊沉积物能否有效地记录大气粉尘源区的风沙活动历史对理解沙尘暴发生的气候和环境背景具有重要的意义。对于位于内蒙古浑善达克沙地南缘的夏日淖(湖)近代沉积物进行 137Cs/210Pb定年和沉积学分析显示,碎屑沉积物具有两个明显的粒度组分,其一是与当地沙丘砂粒度分布相同的中细砂组分; 另一为与大气降尘粒度相似的粉砂组分,自1957年以来反映这两个粒度组分相对变化的中值粒径和>63μm砂的含量都具有显著的变化。与浑善达克地区和中国北方气象记录对比发现,沉积物中值粒径和>63μm砂的含量分别与沙尘暴和6m/s风速(或大风)发生频次呈正相关,与温度呈负相关; 最近50年来这些沉积和气候参数具有总体一致的变化。这样的事实说明,夏日淖沉积物主要由风力搬运沉积的,其粒度与风沙活动存在内在联系,粗粒沉积物增加是风沙活动加强的结果。因此,干旱、半干旱地区湖泊中风力搬运的沉积物粒度受风沙活动强度控制,可以成为重建过去风沙活动历史的重要标志。     

Mechanisms and Models for Bentonite Erosion Used for Geologic Disposal of High Level Radioactive Waste: A Review

The performance of the bentonite buffer in nuclear waste repository concept relies to a great extent on the buffer surrounding the canister having sufficient dry density. Loss of buffer material caused by erosion remains as the most significant process reducing the density of the buffer. In the worst case, the process is assumed to last as long as the free volume between the pellets in the pellets filled regions is filled with groundwater. Erosion rate and mass erosion are calculated based on the erosion model, and the measures are presented to prevent the geological disaster due to bentonite erosion. The groundwaters may solubilise the smectite particles in the bentonite and carry them away as colloidal particles. A dynamic model is developed for sodium gel expansion in fractures where the gel soaks up groundwater as it expands. The model is based on a force balance between and on smectite particles, which move in the water. Attractive van der Waals forces, repulsive electric diffuse layer (DDL) forces, gravity and buoyancy forces and forces caused by the gradient of chemical potential of the particles act to move the particle in the water. The effect of the fracture width and the frictions between particles and water and surrouding rock is analysed based on erosion model. The DDL forces strongly depend on the type of clay minerals and the type of ion and concentration in the water surrounding the particles. In the designed safe use of nuclear waste disposal (tens of thousands of years to hundreds of thousands of years), the safety of nuclear waste disposal is affected by the hydrodynamic and chemical effects, and bentonite erosion. Due to the bentonite erosion, the buffer/backfill layers become loose, and their permeability increases, which causes the nuclear element diffusion and convection, and even the nuclear disaster. In this paper, the mechanisms, models, experiments and control measures of bentonite erosion were systematically summarized. The current deficiencies of bentonite erosion were pointed out, and new methods were put forward to carry out the research for bentonite erosion. The measures were presented to prevent the geological disaster due to bentonite erosion through changes. The project is not only academic innovation, but also has a large practical significance. The research results of this project can be widely applied to the design, construction and maintenance of the bentonite buffer in nuclear waste repository.     

东亚季风区夏季陆地生态系统碳循环对东亚夏季风的响应

东亚地区陆地生态系统的时空变率表现出明显的对季风气候的响应特征。使用EOF（经验正交分解）方法分析了AVIM2动态植被陆面模式离线模拟试验模拟的1953～2004年东亚季风区夏季陆地生态系统总初级生产力（GPP）、生态系统净初级生产力（NPP）、净生态系统初级生产力（NEP）、植被呼吸以及土壤呼吸的时空分布特点,探讨了东亚夏季风对陆地生态系统碳循环影响机制。研究发现,在强季风年,江淮地区高温少雨的特点限制了光合作用,造成GPP偏低;而华南地区在强季风年气候温暖湿润,利于植被生长,GPP偏高。季风对于植被呼吸和土壤呼吸影响不明显,使得GPP和植被呼吸之差NPP的变化及NPP和土壤呼吸之差NEP的变化与GPP的变化保持一致。在强季风年江淮流域地区干热的气候条件使得NPP和NEP降低;但是在华南地区温度升高的同时降水增多使得在NPP偏高的基础上NEP也偏高。     

Turbulence Characteristics Over Complex Terrain In West China

Meteorological data of velocity components and temperature have been measured on a mast of height 4.9 m at one site in the Heihe River Basin Field Experiment (HEIFE) conducted in west China. Mean and individual turbulence parameters, power spectra/cospectra, phase angles and their changes withfetch downwind of a change in surface roughness were analyzed. The turbulence characteristics depend strongly on the prevailing wind direction, which in turn is associated with changes in the upwind surface roughness pattern. The results show that values of horizontal velocity standard deviations sigma;_u,v scaled with local friction velocity u under different stratifications are larger than those over flat terrain, while the values of _w/u have the same values as over flat terrain. The differences between variance values of the horizontal velocity components, u and v, over inhomogeneous terrain were found to be significantly smaller than those over flat terrain. Since energy densities of the w spectra, uw and wT cospectra at low frequencies are relatively lower than those of longitudinal velocity spectra, total energies of w spectra, uw and wT cospectra tend to be in equilibrium with the local terrain. The values of phase angles at the low frequency end of the frequency showed obvious differences associated with changes of roughness.     

下垫面因子影响气候形成和变化的数值试验

本文用球带范围的耦合模式，研究了地球从均一陆地地表有海陆分布，全球陆地从平坦到真实地形，陆地从一类土壤到几类土壤并存过程中大气环流的演变和气候变化状况。发现没有海陆分布时气候要素场呈纬向带状分布，大气中流场和风场表现为三圈环流和行星风系特征，当有海陆分布后，北半球无论是高层还是低层环流形势均具有和海陆分布相一致的纬向两波结构，海陆分布是形成现代大气环流格局的根本因子，高原地形使高原上的空的气压系统