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51.
MODELING THE EFFECTS OF ANTHROPOGENIC SULFATE IN CLIMATE CHANGE BY USING A REGIONAL CLIMATE MODEL 总被引:3,自引:2,他引:3
1 INTRODUCTION Being an important composition of the atmosphere, aerosol attracts increasing attention from the scientific community in recent years, together with the radiative forcing it causes and effects it imposes on the climate system. The anthropogenic aerosol affects the climate both directly and indirectly. The climate is directly affected when solar shortwave radiation is scattered and absorbed in what is known as the 搖mbrella effect? which can be dated back to as early as mor… 相似文献
52.
The climatic impacts of land surface change and carbon management, and the implications for climate-change mitigation policy 总被引:4,自引:0,他引:4
Strategies to mitigate anthropogenic climate change recognize that carbon sequestration in the terrestrial biosphere can reduce the build-up of carbon dioxide in the Earth’s atmosphere. However, climate mitigation policies do not generally incorporate the effects of these changes in the land surface on the surface albedo, the fluxes of sensible and latent heat to the atmosphere, and the distribution of energy within the climate system. Changes in these components of the surface energy budget can affect the local, regional, and global climate. Given the goal of mitigating climate change, it is important to consider all of the effects of changes in terrestrial vegetation and to work toward a better understanding of the full climate system. Acknowledging the importance of land surface change as a component of climate change makes it more challenging to create a system of credits and debits wherein emission or sequestration of carbon in the biosphere is equated with emission of carbon from fossil fuels. Recognition of the complexity of human-caused changes in climate does not, however, weaken the importance of actions that would seek to minimize our disturbance of the Earth’s environmental system and that would reduce societal and ecological vulnerability to environmental change and variability. 相似文献
53.
Susan Subak 《Climate Policy》2003,3(2):107-122
Concern over the “non-permanence” or reversibility of carbon sequestration projects has been prominent in discussions over how to develop guidelines for forest project investments under the Clean Development Mechanism (CDM) of the UNFCCC Kyoto Protocol. Accordingly, a number of approaches have been proposed that aim to help ensure that parties do not receive credit for carbon that is lost before project obligations are fulfilled. These approaches include forest carbon insurance, land reserves, and issuance of expiring credits. The potential costs of each of these different approaches are evaluated using a range of assumptions about project length, risk and discount rate, and a comparison of costs is ventured based on the estimated reduction in value of these credits compared with uninsured, and permanent credits. Obstacles to participation in the different approaches are discussed related to problems of long-term commitments, project scale, rising replacement costs, and low credit value. It is concluded that a system of expiring credits, which could be coupled with insurance or reserves, could guarantee obligations that span time-scales longer than that of conventional insurance policies while maintaining incentives for long-term sequestration. 相似文献
54.
大气气溶胶光学厚度的宽带消光遥感方法及其应用 总被引:6,自引:1,他引:6
该文发展了遥感气溶胶光学厚度的一个宽带消光遥感方法 ,它应用地面上太阳直射表探测的宽波段太阳直射信息反演 0 75 μm大气柱光学厚度。这方法的主要误差因子是气溶胶谱的不确定性。数值试验表明 ,气溶胶谱分布的误差所引起光学厚度解的误差一般小于 5 %。 1995年 1— 10月进行的 12 6 7组对比实验表明 ,由本方法探测的气溶胶光学厚度与光度计探测的气溶胶光学厚度的标准差为 10 5 % ,两者平均结果的偏差只有 0 7%。该文还应用这个方法 ,从气象台站辐射观测资料反演得到北京、沈阳等 10个地方 1980— 1994年间晴天气溶胶光学厚度资料 ,并分析其变化规律 相似文献
55.
黑色岩系中铂族元素地质地球化学特征 总被引:6,自引:0,他引:6
含PGE黑色岩系可根据黑色岩系中有无火成岩,将其分为:(1)与火山作用或岩浆活动无关的黑色岩系;(2)与火山作用或岩浆活动有关的黑色岩系不同地质背景下,富金属黑色岩系的特征及其PGE的分布特征既有相似之处,又各具特点,反映出两者PGE的地球化学演化过程有所差别。有关PGE比值不仅可以反映出元素的地球化学行为,亦可区分或指示不同环境下PGE地球化学演化的规律性。 相似文献
56.
The time evolution of stratospheric aerosol layer formed after a volcanic eruption is studied taking into account the aerosol
microphysical processes of growth, coagulation and sedimentation. Using a simple model we could explain the observed evolution
of the Pinatubo volcanic layer which decayed in about 3 years. The experimental data obtained by Nd:YAG backscatter lidar
over Ahmedabad further supports this finding. The data obtained after the El Chichon volcanic eruption also showed that the
El Chichon aerosol layer decayed in about 3 years time. Thus, though the amount of SO2 injected has been higher, in the case of Pinatubo, about two to three times more than El Chichon, it has resulted in the
production of larger aerosol particles due to faster growth and coagulation processes, and subsequently a faster removal rate,
to give more or less a similar background aerosol amount at the stratosphere in about 3 years time. 相似文献
57.
Acidification of groundwater lags behind acid deposition due to the relatively long water residence time in conjunction with
various buffering processes in the soil zone and deeper aquifer (chemical weathering, cation exchange, sulfate sorption, and
N uptake by the biomass). Extensive field data from eight forested catchments in the Bunter Sandstone of the Black Forest,
including results from water budget studies and hydrochemical analysis of stream and spring waters, were used to simulate
the future evolution of ground-water acidification with the MAGIC model. The present acid deposition exceeds the “critical
load” (here meaning buffering due to chemical weathering and protonation of organic acids) in six of eight catchments. Two
catchments are well buffered because they contain carbonate-bearing layers in the Upper Bunter sandstone. Transient buffering
(i.e., cation exchange, N uptake, the sulfate sorption) thus far prevents worse acidification, but this effect will decline
in the future. For one of the poorly buffered catchments (Seebach), a two-layer simulation was carried out, based on extensive
data from 10 years of measurements. Validation of the long-term simulations by hydrochemical and soil data was hampered by
strong annual variations but generally supported by paleolimnological studies. In the future, reductions in the S deposition
by 20% and the N deposition by 10% up to the year 2030 are assumed as the most probable scenario. N uptake through soil and
vegetation will come to an end as suggested by decreasing C/N ratios of the organic matter. This process is arbitrarily included
in the simulations. In the periglacial soil layer, acidification will decrease until the year 2030 and then approach a steady-state
condition. In the fractured aquifer, acidification will also proceed at a decreasing rate; however, sulfate desorption up
to the year 2130, the end of simulated period, will prevent earlier remediation. Despite a significant reduction in S deposition
since the mid-1980s, further efforts are necessary to reduce the emission of acidifying substances. Liming in the recharge
area is partially effective to ameliorate “shallow” groundwater but largely fails to ameliorate “deeper” groundwater in the
sandstone aquifer.
Received: 30 July 1996/Accepted: 23 January 1997 相似文献
58.
Marina Manca Patrizia Comoli Teresa Spagnuolo 《Aquatic Sciences - Research Across Boundaries》1997,59(1):48-56
We compared three methods for calculating the standing stock biomass ofDaphnia hyalina galeata population in Lago Maggiore during a single year. We applied body length/carbon regression equations (LCR) obtained under
controlled laboratory conditions and directly from field data on carbon and body length to field data on length-specific abundance.
Laboratory-derived equations satisfactorily described our field estimates of length-specific carbon content in spring. As
the length-standardized carbon content decreased exponentially along the season, we included time of the year as an auxiliary
variable, and tested whether it affected slope, intercept or both. The decrease had no effect on slope but reduced the intercept
of the LCR. We also calculated biomass, using a single mean value from the literature. By comparing the results with those
obtained by simple conversion of individuals number into carbon we might discriminate between the effect of changes in the
size frequency distribution of the population and the decrease with time of the length-standardized carbon content. Although
we tested the different models for non-ovigerous females, the results did not change when we included also data on females
with eggs in the first three developmental stages, whereas they changed substantially when we included females with embryos.
We formulate two hypotheses to explain this result and discuss possible implications for the calculation of the standing stock
biomass ofDaphnia population. 相似文献
59.
The color of pumice: case study on a trachytic fall deposit, Meidob volcanic field, Sudan 总被引:1,自引:0,他引:1
This paper examines the cause of color variations of trachytic pumices which are essentially uniform in chemical composition
and proposes a geological model for their formation. A pyroclastic sequence of distinct subunits with brown, buff, and black
pumices was deposited during the 5000-B.P. eruption of a tuff ring in the central Meidob volcanic field (Sudan). Subunits
of buff pumices locally contain minor amounts of streaky pumice with pale-gray and dark-gray domains. The combined evidence
of petrographic studies, chemical analyses of whole pumices and groundmass separates, electron microprobe analyses, optical
spectroscopy, transmission electron microscopy, and magnetic susceptibility measurements show that color variations of the
pumice clasts are related to the size and distribution of Fe3+-rich oxide microcrysts. Buff pumice and light-gray domains of streaky pumice have a colorless, transparent groundmass with
very few microcrysts. Dark-gray domains of streaky pumice contain abundant hematite and/or magnetite microcrysts visible in
thin section within a transparent, colorless glass groundmass. The groundmass of the black pumice clasts is brown in thin
section which is most likely caused by submicroscopic magnetite microcrysts. Brown pumice clasts have a mixed groundmass consisting
of brown domains and domains with opaque microcrysts in transparent glass. Variations in the eruption dynamics have been inferred
from lithological observations. Subunits of black pumices are related to eruption pulses with low magma discharge and high
water/magma mass ratio, whereas subunits of buff pumice were deposited during eruption pulses with high magma discharge and
low water/magma mass ratio. Brown pumices represent the top part of the magma body, and the initial stage of the eruption
probably had a low magma discharge. Streaky pumices are interpreted as the product of syn-eruptive mixing of Fe3+-rich oxide microcryst-bearing magma and microcryst-free magma.
Received: 3 February 1997 / Accepted: 28 July 1997 相似文献
60.
1 INTRODUCTION Sitting in the central part of the Pearl River Delta, Guangzhou is one of the cities in China that are most polluted by acid rain. Broad attention has been brought to the problem. Since the early 1980s, a series of observation and studies h… 相似文献