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1.
Clouds have a large impact on the Earth's radiation budget and hence have the potential to exert strong feedbacks on climate variability and climate change. These feedbacks are not well-understood, so it is essential to investigate observed relationships between cloud properties and other parameters of the climate system. Suitable cloud datasets based on surface observations and satellite observations are described and various advantages and disadvantages of each are discussed. In particular it is noted that significant inhomogeneities likely exist in the datasets which have important implications for studies of climate variability. Recommendations are made for the use of cloud data in future investigations. 相似文献
2.
M. Lockwood 《Space Science Reviews》2006,125(1-4):95-109
In paleoclimate studies, cosmogenic isotopes are frequently used as proxy indicators of past variations in solar irradiance on centennial and millennial timescales. These isotopes are spallation products of galactic cosmic rays (GCRs) impacting Earth's atmosphere, which are deposited and stored in terrestrial reservoirs such as ice sheets, ocean sediments and tree trunks. On timescales shorter than the variations in the geomagnetic field, they are modulated by the heliosphere and thus they are, strictly speaking, an index of heliospheric variability rather than one of solar variability. Strong evidence of climate variations associated with the production (as opposed to the deposition) of these isotopes is emerging. This raises a vital question: do cosmic rays have a direct influence on climate or are they a good proxy indicator for another factor that does (such as the total or spectral solar irradiance)? The former possibility raises further questions about the possible growth of air ions generated by cosmic rays into cloud condensation nuclei and/or the modulation of the global thunderstorm electric circuit. The latter possibility requires new understanding about the required relationship between the heliospheric magnetic fields that scatter cosmic rays and the photospheric magnetic fields which modulate solar irradiance. 相似文献
3.
Cosmic Rays,Clouds, and Climate 总被引:5,自引:0,他引:5
A correlation between a global average of low cloud cover and the flux of cosmic rays incident in the atmosphere has been observed during the last solar cycle. The ionising potential of Earth bound cosmic rays are modulated by the state of the heliosphere, while clouds play an important role in the Earth's radiation budget through trapping outgoing radiation and reflecting incoming radiation. If a physical link between these two features can be established, it would provide a mechanism linking solar activity and Earth's climate. Recent satellite observations have further revealed a correlation between cosmic ray flux and low cloud top temperature. The temperature of a cloud depends on the radiation properties determined by its droplet distribution. Low clouds are warm (>273K) and therefore consist of liquid water droplets. At typical atmospheric supersaturations (1%) a liquid cloud drop will only form in the presence of an aerosol, which acts as a condensation site. The droplet distribution of a cloud will then depend on the number of aerosols activated as cloud condensation nuclei (CCN) and the level of super saturation. Based on observational evidence it is argued that a mechanism to explain the cosmic ray-cloud link might be found through the role of atmospheric ionisation in aerosol production and/or growth. Observations of local aerosol increases in low cloud due to ship exhaust indicate that a small perturbation in atmospheric aerosol can have a major impact on low cloud radiative properties. Thus, a moderate influence on atmospheric aerosol distributions from cosmic ray ionisation would have a strong influence on the Earth's radiation budget. Historical evidence over the past 1000 years indicates that changes in climate have occurred in accord with variability in cosmic ray intensities. Such changes are in agreement with the sign of cloud radiative forcing associated with cosmic ray variability as estimated from satellite observations. 相似文献
4.
Satellite observations have recently revealed a surprising imprint of the 11-year solar cycle on global low cloud cover. The cloud data suggest a correlation with the intensity of galactic cosmic rays. If this apparent connection between cosmic rays and clouds is real, variations of the cosmic ray flux caused by long-term changes in the solar wind could have a significant influence on the global energy radiation budget and the climate. However a direct link between cosmic rays and clouds has not been unambiguously established and, moreover, the microphysical mechanism is poorly understood. New experiments are being planned to find out whether cosmic rays can affect cloud formation, and if so how. 相似文献
5.
An increasing number of studies indicate that variations in solar activity have had a significant influence on Earth's climate.
However, the mechanisms responsible for a solar influence are still not known. One possibility is that atmospheric transparency
is influenced by changing cloud properties via cosmic ray ionisation (the latter being modulated by solar activity). Support
for this idea is found from satellite observations of cloud cover. Such data have revealed a striking correlation between
the intensity of galactic cosmic rays (GCR) and low liquid clouds (<3.2 km). GCR are responsible for nearly all ionisation
in the atmosphere below 35 km. One mechanism could involve ion-induced formation of aerosol particles (diameter range, 0.001–1.0
μm) that can act as cloud condensation nuclei (CCN). A systematic variation in the properties of CCN will affect the cloud
droplet distribution and thereby influence the radiative properties of clouds. If the GCR-Cloud link is confirmed variations
in galactic cosmic ray flux, caused by changes in solar activity and the space environment, could influence Earth's radiation
budget.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
F. Arnold 《Space Science Reviews》2006,125(1-4):169-186
A physical mechanism which may have a potential to connect climate with cosmic rays (CR) involves aerosol particle formation
by CR generated atmospheric ions followed by new particle growth. Only grown particles can scatter sunlight efficiently and
can eventually act as cloud condensation nuclei (CCN) and thereby may influence climate. Moreover grown particles live longer
as they are less rapidly scavenged by pre-existing larger particles. The present paper discusses aerosol particle formation
and growth in the light of new measurements recently made by our MPIK Heidelberg group. Emphasis is placed upon the upper
troposphere where very low temperatures tend to facilitate new particle formation by nucleation. The new measurements include:
laboratory measurements of cluster ions, aircraft measurements of ambient atmospheric ions, and atmospheric measurements of
the powerful nucleating gas H2SO4 and its precursor SO2. The discussion also addresses model simulations of aerosol formation and growth. It is concluded that in the upper troposphere
new aerosol formation by CR generated ions is a frequent process with relatively large rates. However new particle formation
by homogeneous nucleation (HONU) which is not related to CR also seems to be efficient. The bottleneck in the formation of
upper troposphere aerosol particles with sizes sufficiently large to be climate relevant is not nucleation but growth of small
particles. Our recent upper troposphere SO2 measurements suggest that particle growth by gaseous sulphuric acid condensation is at least occasionally efficient. If so
CR mediated formation of CCN sized particles should at least occasionally be operative in the upper troposphere. 相似文献
7.
Y. J. Kaufman 《Space Science Reviews》2006,125(1-4):139-147
Anthropogenic aerosols affect the climate system and the hydrological cycle. The net effect of aerosols is to cool the climate
system, directly by reflecting sunlight to space, and indirectly by increasing the brightness and cover of clouds that in
turn also reflect more sunlight to space. The uncertainty in the aerosol effect on climate is 5 times greater than that of
the greenhouse gases. The reason for this is the short aerosol lifetime and chemical complexity, that makes it difficult to
represent the global aerosol budget from surface or aircraft measurements. Satellites provide daily global information about
the aerosol content, generating large statistics with excellent regional and global representation of the aerosol column concentration,
and differentiating fine from coarse aerosol. Here we use observations performed with the MODIS instrument onboard the Terra
and Aqua satellites to differentiate natural from anthropogenic aerosols, and to measure the aerosol effect on cloud properties
and on the reflectivity of sunlight. 相似文献
8.
Cosmic Rays and Earth's Climate 总被引:1,自引:0,他引:1
During the last solar cycle the Earth's cloud cover underwent a modulation in phase with the cosmic ray flux. Assuming that
there is a causal relationship between the two, it is expected and found that the Earth's temperature follows more closely
decade variations in cosmic ray flux than other solar activity parameters. If the relationship is real the state of the Heliosphere
affects the Earth's climate.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
积冰对飞行的影响及处置 总被引:1,自引:0,他引:1
张序 《西安航空技术高等专科学校学报》2011,29(3):19-23
研究积冰的气象因素对飞行的影响以及积冰的处置。从云的物理学原理方面进行推导和讨论,分析积冰形成的机制,重点论述翼面积冰对飞行的影响,并从机翼积冰和尾翼积冰两个方面进行详细分析。通过对一些典型事例进行分析,阐述飞行中积冰的预防和积冰后的处理方法。 相似文献
10.
针对多传感器多目标航迹关联的特点,提出了将类云模型和c均值聚类联合应用于航迹关联的解决方法。将表征航迹特征的参量构成聚类中心和待分类的样本空间,利用类云模型和c均值聚类算法对来自不同传感器的航迹进行分类和收敛判断,构建了基于类云模型的c均值聚类航迹关联模型,有效地解决了目标密集环境下的航迹关联问题,通过仿真研究说明了该算法的有效性和鲁棒性。 相似文献
11.
Our current understanding of mechanisms that are, or may be, acting to cause climate change over the past century is briefly reviewed, with an emphasis on those due to human activity. The paper discusses the general level of confidence in these estimates and areas of remaining uncertainty. The effects of increases in the so-called well-mixed greenhouse gases, and in particular carbon dioxide, appear to be the dominant mechanism. However, there are considerable uncertainties in our estimates of many other forcing mechanisms; those associated with the so-called indirect aerosol forcing (whereby changes in aerosols can impact on cloud properties) may be the most serious, as its climatic effect may be of a similar size as, but opposite sign to, that due to carbon dioxide. The possible role of volcanic eruptions as a natural climate change mechanism is also highlighted. 相似文献
12.
To determine the orbital parameters of a satellite using star occultations, it is necessary to measure the intensity of stars as they occult. The accuracy of the intensity measurements is reduced by interfering sources of light and internal noise, and is expressed in terms of the magnitude of various sources of interference. Subsequently, a specific system is analyzed in detail. Moonlit cloud tops introduce the largest systematic error. Photon noise from the star radiation, airglow, and moonlit cloud tops are the largest sources of random errors. 相似文献
13.
K. Scherer H. Fichtner T. Borrmann J. Beer L. Desorgher E. Flükiger H.-J. Fahr S. E. S. Ferreira U. W. Langner M. S. Potgieter B. Heber J. Masarik N. Shaviv J. Veizer 《Space Science Reviews》2006,127(1-4):467-465
In recent years the variability of the cosmic ray flux has become one of the main issues interpreting cosmogenic elements
and especially their connection with climate. In this review, an interdisciplinary team of scientists brings together our
knowledge of the evolution and modulation of the cosmic ray flux from its origin in the Milky Way, during its propagation
through the heliosphere, up to its interaction with the Earth’s magnetosphere, resulting, finally, in the production of cosmogenic
isotopes in the Earth’ atmosphere. The interpretation of the cosmogenic isotopes and the cosmic ray – cloud connection are
also intensively discussed. Finally, we discuss some open questions. 相似文献
14.
The past dozen years have produced a new paradigm with regard to the source regions of comets in the early solar system. It
is now widely recognized that the likely source of the Jupiter-family short-period comets (those with Tisserand parameters,
T > 2 and periods, P, generally < 20 years) is the Kuiper belt in the ecliptic plane beyond Neptune. In contrast, the source
of the Halley-type and long-period comets (those with T < 2 and P > 20 years) appears to be the Oort cloud. However, the comets
in the Oort cloud almost certainly originated elsewhere, since accretion is very inefficient at such large heliocentric distances.
New dynamical studies now suggest that the source of the Oort cloud comets is the entire giant planets region from Jupiter
to Neptune, rather than primarily the Uranus-Neptune region, as previously thought. Some fraction of the Oort cloud population
may even be asteroidal bodies formed inside the orbit of Jupiter. These comets and asteroids underwent a complex dynamical
random walk among the giant planets before they were ejected to distant orbits in the Oort cloud, with possible interesting
consequences for their thermal and collisional histories. Observational evidence for diversity in cometary compositions is
limited, at best.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
T. R. Kaiser 《Space Science Reviews》1963,1(3):554-575
Estimates of the spatial density of interplanetary dust are derived from meteor, accretion and zodiacial cloud observations. When the most recent data are considered it is found that there is no longer any serious discrepancy between the extrapolated meteor values and those from the other sources and a density distribution is obtained which extends from meteoroids capable of producing the brightest optical meteors to particles approaching the limiting size beyond which they are removed from the solar system by solar radiation pressure. Impacts on rocket and satellite vehicles lead to much higher estimates of spatial densities and it is concluded that they originate from particles in geocentric orbits belonging to a dust cloud encompassing the earth. The evidence tends to support the view that these particles are captured from the interplanetary dust cloud rather than being produced, as suggested by Whipple, through the impact of meteorites on the moon.Some suggestions are made for the direction of future rocket and satellite investigations.Contribution to the COPERS symposium on The Interplanetary medium, held in Paris on June 19, 1962. 相似文献
16.
《中国航空学报》2020,33(8):2146-2161
Aircraft icing has been proven to be one of the most serious threats to flight safety. During the analysis of flight risk under icing conditions, quantitative assessment and visualization of flight risk are quite essential as they provide safe manipulation strategies in intricate conditions. However, they are rarely studied. Since the icing flight accidents are the result of the coupling of multiple unfavorable factors, in present study, we have proposed a method to quantitatively assess flight risk induced by multi-factor coupling under icing conditions by Monte-Carlo simulation and multivariate extreme value theory. The results demonstrate that the flight risk probability increases with the rise of unfavorable factors. Besides, a flight risk visualization method named flight safety window has been presented to build the flight risk distribution cloud maps in different complex conditions. The cloud maps show that the icing would give rise to atrophy of the safety scope, and the consequence would be even more severe when coupled with other more unfavorable factors. The proposed methods in this study would be useful in flight risk analysis under icing conditions and can enhance the pilot's situational awareness in selecting correct strategies within the safety zone to avoid unsafe manipulation. 相似文献
17.
18.
Aerosol-Cloud Interactions Control of Earth Radiation and Latent Heat Release Budgets 总被引:2,自引:0,他引:2
D. Rosenfeld 《Space Science Reviews》2006,125(1-4):149-157
Aircraft observations and model simulations show that cloud development is strongly modulated by the impact of cloud-aerosol
interactions on precipitation forming processes. New insights into the mechanisms by which aerosols dominate the cloud cover
of marine shallow clouds suggest that feedbacks between the cloud microstructure and cloud dynamics through precipitation
processes play a major role in determining when a solid cloud cover will break up into a field of trade wind cumulus. Cloud-aerosol
interactions dominate not only the dynamics of marine shallow clouds, but also the lifetime and the vertical disposition of
latent heat of deep convective clouds over ocean and even more strongly over land. Recent coincident satellite measurements
of aerosols and cloud properties quantify the aerosol effects on cloud cover and radiative forcing on regional and global
scales. The shapes of the satellite retrieved relations between aerosols and cloud properties are consistent with the suggested
ways by which aerosols affect clouds via precipitation processes, particularly by affecting the intensity of the cloud vertical
air motions and its vertical development. 相似文献
19.
20.
单光子激光雷达获取的点云数据存在大量噪声,这给数据的处理带来了挑战。基于局部距离统计提出了改进的点云去噪算法,对单光子激光雷达点云原始数据进行去噪。然后基于统计分析方法改进了点云滤波算法,对去噪后的点云数据进行滤波处理。利用新提出的算法与传统算法去噪和滤波后得到的点云进行比较,并与传统激光雷达的数字地形模型(DTM)数据进行对比。计算得到MABEL地面点云相对于传统激光雷达高程的均方根误差RMSE为2.98m,相关系数R^2为0.9938。进一步对地面点云插值得到剖面数字高程模型(DEM)数据,其相对于传统激光雷达高程的均方根误差RMSE为2.85m,相关系数R^2为0.9931。实验结果显示,提出的单光子激光雷达点云去噪和滤波算法优于传统算法,与传统激光雷达DTM数据具有较好的相关性,能够精确的恢复地形信息。 相似文献