The Third Draft, 2 November 1999
The climate is determined by the radiative balance of the Earth-atmosphere system, where it depends on the input of solar radiation, the total amount of greenhouse gases, clouds, and aerosols. As an important factor affecting radiative budget, atmospheric aerosol particles influence climate in two ways, direct and indirect. They can scatter and absorb solar radiation, thereby directly changing the planetary radiation budget. In the while, aerosols, especially soluble aerosols can modify the microphysics and optical properties of cloud by acting as cloud condensation nuclei (CCN) enhancing the reflectivity of low-level water clouds, and can also alter the development of precipitation by influencing the mean cloud drop size and affecting cloud lifetime and hydrological cycle, thereby indirectly affect global climate. Taken together, the estimated combined effects of atmospheric aerosols on the earth radiation budget today may be comparable in magnitude but opposite in sign to those caused by greenhouse forcing.
Unlike the principal anthropogenic greenhouse gases, aerosols influence on climate much more complex. It not only depends on aerosol physical and chemical properties, such as particle size, chemical composition, single-particle optical properties, but also depends on its source emission, spatial distribution, temporal variation and so on. Scientific studies have shown that the global patterns of radiative forcing caused by aerosol are highly non-uniform, the maximum magnitude of the forcing lie in central Europe, northern American and eastern China. At present, in some locations, especially in above areas, the cooling effect of some kinds of aerosols can be large enough to more than offset the warming due to greenhouse gases. Although aerosol particles have some potential climatic importance, they are poorly characterized in global climate model and regional climate model. The reason is lack of their observational data of chemical and physical properties, geographical distribution, source emission, mass and size distribution as well as time trend. Therefore, academic exchange, cooperation and multiple observations are necessary to understand clearly the properties of aerosol particles.
As the development of economy, the source emission over East Asia has been increasing in recent years. A large number of SO2 gases resulting from anthropogenic activities such as fossil fuel combustion, coal refine, and ore smelting, automobiles, chemical industries and so on are emitted into the atmosphere and result in the concentration of sulfate aerosols increase. Those sulfate particles, on the one hand, lead to serious environmental problems. According to Chinese scientific researches, some evident "acid rain" occurs over southwestern China, southeastern China and the central China. The acidification become more and more severe and the domain of the "acid rain" become larger with the time. On the other hand, a great number of sulfate particles cause a series of climate problems. Scientific studies show that the global radiation and direct radiation in most part of China take on an obvious decreasing trend during the past 30 years. The mean temperature has decreased in the middle and low reaches of Yangzi River under the background of global warming since 1980s. Those areas are cooling regions and the cooling center locates in Sichuan basin of China. The analyzed results show that the increasing concentration of sulfate caused by industrial SO2 emission may be one of the principal factors, which lead to temperature decrease.
In addition to anthropogenic sulfate, other aerosols such as desert dust, soot, biomass burning and sea salt particles can also have significant effects on regional climate. For example, duststorms in western China can inject a large amount of desert dust into atmosphere. The dust can be exported over the Pacific Ocean, which may alter chemical and radiative processes in the remote troposphere. Anyway, more and more scientists have paid their attention to the studies of aerosols.
Prior to the 1980s, Our working group have noted the potential environmental and climatic importance of aerosols as a result of more and more severe "acid rain", "air pollution", "global climate change", and increasing sandstorm events. A series of experiments and theoretical analyses in aerosol investigation have been carried out. A great amount of data and some analyzed results have been obtained, some of which have been submitted to several international conferences. The detailed information and results will be given in the following.
Table 1. Measurements of aerosols at several locations
|Beijing||39.9o N, 116.3oE||Since 1996||NASDA|
|ShangDianzi||40.65oN, 117.10oE||In 1998||WMO|
|Since 1997||Chiba University|
|Since 1998||Chiba University|
|Guangdong||24.05oN, 114.2oE||In 1998|
|Lin'an, RBS||30.30oN, 119.73oE||Since 1991||WMO/PEM-WEST|
|Hefei||31.31oN, 117.16oE||Since 1992||AIOFM,
|LongFengshan, RBS||44.73oN, 127.60oE||Since 1991||WMO/PEM-WEST|
|WaLiguan, GAW Site||36.17oN, 100.54oE||Since 1991||WMO/PEM-WEST|
RBS: Regional Background Sites, GAW: Global
Scientific research showed that much of the Pacific is heavily impacted by long range transport of sulfur or Kosa from Asia. A series of investigation have been made in the Asia-Pacific regions to investigate aerosol composition. Since 1985, our working group have participated in some international cooperation projects and collected many aerosol samples in different regions. Some of those samples are shown in the following.
A great amount of data has been collected from above experiments. Some of them have been submitted to several international conferences. The following are some preliminary analyzed results
Radiative properties of aerosols
Chemical properties of aerosols
Scientific efforts to understand the spatial and temporal distribution patterns, as well as potential environment and climate effects of aerosols involve a combination of laboratory experiments, field observations, and modeling analysis. Laboratory experiments provide the basic physical and chemical properties of aerosol particles. Field observations are usually designed to study aerosol properties on a limited region. Since laboratory experiments and field observations by themselves can not fully elucidate complex atmospheric phenomena like acid deposition, sandstorm and so on, models that allow multiple processes to occur simultaneously are required for data analysis. Therefore, numerical modeling provides the only means to assess the impact of aerosols on environment and climate, and also the only means to provide such a theoretical basis to investigate the relationships between the emissions, atmospheric transport, chemical and removal process, and the resultant aerosol distribution. Prior to 1980s, our working group began to work on the modeling researches and have developed some numerical models, which were used to investigate the temporal and spatial patterns of aerosols, aerosol evolution, and interactions between aerosol and cloud. Some significant simulated outputs have been made. In the following, the models and analyzed results are shown.
II.1 Radiative Transfer Model
An effective and fast K-distribution and CK-distribution radiation model developed by us has been coupled to GOALS/LASG. IAP to study radiative transfer, radiative forcing and climate effects of trace gases and aerosols. The model can consistently treat the radiative processes of both shortwave and longwave regimes, especially the case with co-existence of multiple scattering and absorption. The new radiation scheme is well-modularized and easy to be improved. The coupled model shows significant improvement in simulated outputs, especially in the thermal structure of the atmosphere and the zonal averaged wind, which are directly related to the diabetic heating processes.
II.2 Two dimensional seasonal nonlinear energy balance model
A two-dimensional seasonal nonlinear energy balance model also has been developed to simulate the climate forcing of aerosols. The simulated results showed that the climate effect of tropospheric aerosol presents strong regional characteristics, especially in considering non-linear feedback. The radiative forcing of stratospheric aerosols are also calculated. It was found that the radiative forcing caused by stratospheric aerosols is not only related to its horizontal variation, but also to the surface albedo. The surface temperature showed a great decrease in late 1992 due to the Pinatubo aerosols, but the perturbation became very small in mid-1996.
II.3 Three-dimensional chemical transport model (CTM)
A three-dimensional regional Eulerian model of sulfur transport, which includes dynamic transport, turbulent diffusion, gas-phase and aqueous chemistry, wet and dry depositions, as well as emission processes, have been developed to investigate temporal and spatial variations of anthropogenic sulfate column burden over Eastern Asia during mid-1990s on the base of recent emission data of anthropogenic sulfur dioxide (SO2) at a horizontal resolution of 1o�1o. The model has been proved to have a good resolution and sensitivity. The simulated results indicate anthropogenic SO2 emission in China, especially in eastern China which is a fast economically developing region, have been one of the major contributions to Eastern Asia and global total emission. Human activities in Eastern Asia result in a rapid increase in sulfate column burden not only in pollution areas but also in offshore water. Anthropogenic column sulfate distribution has obvious seasonal and spatial pattern. The relatively large magnitude of summertime sulfate column loadings move to the north of China as compared with wintertime. In pollution area, 2 peak loadings of monthly sulfate are found to occur in September and May respectively and the maxima loadings in September. In terms of vertical distribution, the sulfate concentration decreases rapidly with height, and most of the sulfate is found in the bottom 4 km of the troposphere; In offshore water, the anthropogenic sulfate burden which show the magnitude of transport from eastern China is higher in autumn and winter than that in spring and summer. In Tibetan Plateau, only one peak loadings is found, maximum occurs in summer and minimum in winter. In winter, the sulfate concentration decreases with height over Tibetan Plateau; but in summer, the maxima concentration occurs in the height of 300 m due to sulfate convergence in the lower troposphere. In the meanwhile, anthropogenic sulfate concentration at each level over the Tibetan Plateau in summer are almost a factor of 10 higher than that in winter because of strong upwelling motion of sulfate to the upper troposphere.
II.4 Size-resolved aerosol evolution model
A size-resolved atmospheric aerosol model including the basic aerosol dynamic processes such as coagulation, condensation, deposition and nucleation is developed to simulate the production and evolution of aerosols in remote marine boundary layer. The Simulated results show that production of new particles depends on both the size distribution of the preexisting particles (total number and diameter) and SO2 concentration. Coupled with a simple DMS oxidation model, the processes from DMS emissions to CCN formation are simulated under typical meteorological condition in the remote marine boundary layer. The calculation supported that DMS from ocean plankton can be the main source of aerosols and CCN over the oceans. And only 25% of total particles formed from gas-particle processes exceed 0.1 m m in diameter after 4 days, which indicated that the fine particles in remote marine atmosphere are produced from homogeneous nucleation and acid condensation. There is a non-linear relation between CCN number concentration (formed from gas-to-particle processes) and sulfate mass concentration in aerosols.
II.5 One-dimensional aerosol-cloud model
A one-dimensional high-order turbulence closure model coupled with the explicit aerosol and cloud micro-physical processes has been set up to simulate the processes in the stratocumulus-topped boundary layer (STBL). The preliminary results show the basic physical processes in the STBL can be well described by the model. But there are some problems in simulation of the microphysical processes. We are still working on it and paying much attention on feedback of turbulence on aerosol and cloud processes.
I. Goal and Objective
This program is designed to understand the basic distributions and variation features of aerosols in our country, to reveal preliminarily the main mechanism of their variation, and put forward a predictive view in future and their possible impacts on the climate, environment and ecology. The most noticeable characteristics of this program are the multi-disciplinary cross-combination of the atmospheric science, photochemistry, environmental science and ecological science, etc., the combination of multi-methodology including composite field observation, chemical simulation in Laboratory, theoretical analysis and numerical simulation.
II. Research Emphases and Project Implementation
In order to implement the scientific objective of this program, the following aspects are identified for the study.
II.1 Field observation
Although a series of researches including field observations and modeling analysis have been done since 1980s, we are not yet able to perform integrated assessments to predict the social and economic impacts of changes in aerosols. One of the main reasons is lack of enough observational data, which provide chemical and physical properties, source emission, mass and size distribution of aerosols in different regions of China. Anyway, a widely spaced network of stations is very helpful to predicting quantitatively aerosols from existing models. The potential sites are list below. Most of these sites which almost covers the main source of aerosols over China, have been or are being used. A few potential sites such as Chendu, Xingjiang, Yantai and Qingdao, Lanzhou, Xi'an, and Heihe basin will be added. Some new instruments such as Lidar systems will be added in Xingjiang and Dunhuang.
Xingjiang Uygur Autonomous Region
Dunhuang (40.2oN, 94.7oE), western of Gansu Province
Heihe Basin, western of Gansu Province
Yinchuan (38.5oN, 106.2oE), Ningxia Hui Autonomous Region
Lanzhou, Gansu province
Xi'an, shanxi Province
WaLiguan(36.17oN, 100.54oE), Qinghai Province, GAW site
Lhasa (29.65oN, 91.13oE), Tibet
Chendu, Sichuan Province
Northeastern China LongFengshan(44.73oN, 127.60oE), Helongjiang province, RBS
Eastern and central China
Beijing (39.9oN, 116.3oE)
ShangDianzi (40.65oN, 117.10oE), Beijing
Yiantai (37.5oN, 121.4oE), Shandong Province
Qingdao, Shandong Province
Hefei (31.31oN, 117.16oE), Anhui Province
Shouxian (32.6oN, 116.8oE), Anhui Province
Lin'an (30.30oN, 119.73oE), Zhejiang Province, RBS
Southern China Guangdong (24.05oN, 114.2oE ), Guangzhou Province
Here RBS means Regional Background Sites, GAW means Global Atmospheric Watch.
Beijing (39.9oN, 116.3oE)
Lanzhou, Gansu province
Hefei (31.31oN, 117.16oE), Anhui Province
With the progress of sensors boarded on the near future satellite, such as GLI, POLDER and OCTS on ADEOS II, MODIS and MISR on EOS-AM I, the multispectral, multiangular and polarization measurements which provide more and more information of aerosols than ever will be available. In order to make efficient use of this information, many researches will be working on.
II. 2 Analysis and Numerical Simulation.
Analysis and numerical simulation will emphasize on the following scientific issues
The makeup of our working group is as following
Guang-yu Shi, Professor, Institute of Atmospheric Physics, CAS, Beijing, 100029, China, email@example.com, Tel: +86-10-6204-0674, Fax: +86-10-6204-6358
Xiao-ye Zhang, Professor, State Key Laboratory of Loess & Quaternary Geology, Institute of Earth Environment, CAS, P.O. Box 17, Xi'an, 710054, China, firstname.lastname@example.org, Tel & Fax: +86-29-552-4748.
Chun-sheng Zhao, Associate Professor, Department of Geophysics, Peking University, Beijing, 1000871, China, email@example.com, Tel: +86-10-6275-1131
Jie Tang, Associate Professor, Chinese Academy of Meteorological Science, China Meteorological Administration, Baishiqiao Rd. 46, Beijing, 100081, China, firstname.lastname@example.org, Tel: +86-10-6840-7238, Fax: +86-10-6217-6414
Jun Zhou, Professor, Anhui Institute of Optics and Fine Mechanics, CAS, Anhui, 230031, China, email@example.com, Tel: +86-551-559-1007
Fen-lan Qian, Associate Professor, National Research Center for
Marine Environment Forecasts, Beijing, 100081, China, firstname.lastname@example.org,
Tel: +86-10-6217-3322 . Ext. 152
Ming-xing Wang, Professor and Director, Institute of Atmospheric Physics, CAS, Beijing, 100029, China, Tel: +86-10-6236-0445
Xiu-ji Zhou, Professor, Chinese Academy of Meteorological Science,
China Meteorological Administration, Beijing, 100081, China
Ming-yu Zhou, Professor, National Research Center for Marine Environment Forecasts, Beijing, 100081, China, email@example.com
Yu Qin , Professor, Department of Geophysics, Peking University, Beijing, 1000871, China, firstname.lastname@example.org, Tel: +86-10-6275-1131
Jie-tai Mao, Professor, Department of Geophysics, Peking University, Beijing, 100871, China, email@example.com, Tel: +86-10-6275-1131
Jin-huan Qiu, Professor, Institute of Atmospheric Physics, CAS, Beijing, 100029, China, Tel: +86-10-6204-9044
Huan-lin Hu, Professor and Director, Anhui Institute of Optics and Fine Mechanics, CAS, Anhui, 230031, China, Tel: +86-551-559-1012
Ze-wei Lu, Professor, National Natural Science Fundation of China, Beijing, 100029, China, Tel: +86-10-6201-6655, Ext.: 2122.
Zhi-Bao Shen Professor, Lanzhou Institute of Plateau Atmospheric Physics, CAS, Lanzhou, 730000, China, firstname.lastname@example.org.
Gushun Zhuang Professor, Beijing Normal University, Beijing, 100029, China, email@example.com, Tel:86-10-82904762
Ren-jian Zhang, Associate Professor, Institute of Atmospheric Physics, CAS, Beijing, 100029, China, firstname.lastname@example.org, Tel: +86-10-6235-9642, Fax: +86-10-6202-8604
Wei-biao Chen Ocean University of Qingdao, Qingdao, 266003, China, email@example.com
Xi-hong Wang, Assistant Professor, Ph.D, Institute of Atmospheric Physics, CAS, Beijing, 100029, China, firstname.lastname@example.org, Tel: +86-10-6204-3566, Fax: +86-10-6204-6358
Jun-hua Zhang, Ph.D. student, Department of Geophysics, Peking University, Beijing, 100871, China, email@example.com, Tel: +86-10-6275-1131
Xiang-dong Zheng, Ph.D. student, Chinese Academy of Meteorological
Science, China Meteorological Administration, Baishiqiao Rd. 46, Beijing,
100081, China, firstname.lastname@example.org, Tel: +86-10-6217-6414
Several other Scientists to be added.