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Topic: Cloud forcing

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  The influence of cosmic rays on terrestrial clouds and global warming
Also, because cloud formation processes probably differ in different meteorological regimes, such as pertain for instance over the tropics and the poles, and the cosmic ray flux is known to be dependent on magnetic latitude, we have examined the correlation between cloud factor and cosmic ray flux in different latitude zones, separately.
The correlation of low cloud factor and cosmic ray flux is unexpected as the maximum degree of ionization by cosmic rays occurs in the altitude range 12-15km, i.e.
By analysing different low cloud types separately we found that clouds in a liquid phase account for almost all the variability during the observed period, leaving the ice clouds constant in time, except at the poles where a slight increasing trend for some of the ice cloud types is found.
www.solarstorms.org /CloudCover.html   (3870 words)

In response to changes in precipitation and cloud cover, the shortwave cloud forcing reacts to display a heating effect in the south and a cooling effect in the north, while the response of longwave cloud forcing has an opposite pattern with a cooling effect in the south and a heating effect in the north.
As the response of the greenhouse effect of clouds has a relatively weak magnitude, the pattern of the response of net cloud forcing is very similar to that of shortwave cloud forcing.
As the high cloud cover may be the major contributor to the greenhouse effect of clouds, a further study of the response of high cloud cover is thus highlighted.
atoc.colorado.edu /~sul/Conclusion.html   (411 words)

 NOAA OGP Programs   (Site not responding. Last check: 2007-10-11)
From Figure 2a, the shortwave surface cloud forcing is negative everywhere, indicating that the effect of clouds in the shortwave is to cool the surface.
The distribution of the longwave surface cloud forcing in the NASA SRB data is influenced by cloud amount, cloud-base height, water vapor burden in the atmosphere, and to a lesser extent surface temperature.
The shortwave forcing is everywhere negative, indicating that clouds tend to cool the surface in the shortwave in the NCEP/NCAR reanalysis.
www.ogp.noaa.gov /mpe/gapp/abstr/2001/iskenderian_2003.html   (2172 words)

 Cloud forcing - Wikipedia, the free encyclopedia
Cloud forcing (sometimes described as 'cloud radiative forcing') is the difference between the radiation budget components for average cloud conditions and cloud-free conditions.
These numbers should not be confused with the usual radiative forcing concept, which is for the change in forcing related to climate change: clouds remain one of the largest uncertainties in future projections of climate change by global climate models.
Trapping of the long-wave radiation due to the presence of clouds reduces the radiative forcing of the greenhouse gases compared to the clear-sky forcing.
en.wikipedia.org /wiki/Cloud_forcing   (352 words)

Because the long-wave cloud forcing heats the troposphere in the tropics, the cirrus-induced diabatic heating of the troposphere acts in cooperation with latent heating to drive the large-scale Hadley and Walker circulations (Figure 7).
Thus, Cl(Z=0) is the effect of clouds on the surface long-wave radiation heating; Cl is the effect of clouds on the surface-troposphere long-wave radiation heating; and the difference, Cl - Cl(Z=0), is the effect of clouds on the long-wave heating of the troposphere.
Consider a 50% cloud fraction, and the clear-sky downward flux at the surface is Fa-(Z=0) = 400 Wm-2; underneath the cloud deck, the downward flux is Fc- = 440 Wm-2.
www-c4.ucsd.edu /cepex/Chapter2.html   (3843 words)

 Low-Level Clouds   (Site not responding. Last check: 2007-10-11)
Low clouds over the ocean are extremely important for the energy balance of Earth because their albedos are much higher than that of clear sky over ocean and they have only a small effect on escaping longwave radiation.
Low clouds are abundant over the oceans and are especially common in high latitudes and over the eastern margins of the oceans where low sea surface temperatures and atmospheric subsidence encourage their presence.
The amount and optical properties of low stratiform clouds are sensitive to both atmospheric and oceanic large-scale properties and to the abundance of cloud condensation nuclei, which may be affected by human activities such as the burning of fossil carbon.
eos.atmos.washington.edu /lowclouds.html   (581 words)

Conversely, the radiative forcing due to fl carbon aerosol is strongest when the aerosol is at higher altitudes due to the combined effects of the aerosol residing above more cloudy layers and the reduction of scattering and absorption in the overlying atmosphere.
The relationship between radiative forcing and the accompanying climate response was investigated in the case of a globally homogeneous greenhouse gas forcing and a variety of Northern Hemisphere-only forcings characteristic of anthropogenic sulfate aerosols.
In particular, the meridional gradient of the surface temperature response in the Northern Hemisphere is dependent on the spatial confinement of the forcing and its latitudinal and longitudinal extents.
www.gfdl.noaa.gov /reference/AR97/2RadiationandClouds.html   (4537 words)

 NASA: TERRA (EOS AM-1) - About Terra
Clouds are visible collections of small particles of water or ice, or both, suspended in the atmosphere.
Net cloud forcing is the result of two opposing effects: (1) greenhouse heating by clouds (or positive forcing) — clouds trap heat coming from Earth's surface that would otherwise be lost to space, and (2) cooling by clouds (or negative forcing) — clouds reflect incoming solar radiation back to space.
Because clouds change rapidly over short time and space intervals, they are difficult to simulate in computer models and, therefore, their contribution to climate change is difficult to quantify.
terra.nasa.gov /FactSheets/Clouds   (1371 words)

 ARL-SCRIPPS Publications - 2001
Cloud radiative forcing at the top of the atmosphere is derived from narrowband visible and infrared radiances from NOAA-12 and 14 Advanced Very High Resolution Radiometer (AVHRR) data taken over the Arctic Ocean during the First ISCCP Regional Experiment Arctic Cloud Experiment (FIRE ACE) during spring and summer of 1998.
Net cloud forcing varied from -15 Wm-2 in May to -31 Wm-2 during July, while longwave cloud forcing was nearly constant at ~8 Wm-2.
The cloud forcing results, while similar to some earlier estimates are the most accurate values hitherto obtained for regions in the Arctic.
cloud.ucsd.edu /publications/pub2001.html   (407 words)

 Cloud "Forcing"
At night, clouds are like a blanket keeping the surface warm, but in the daytime clouds reflect much solar radiation, so it is not clear whether their net effect is to heat or cool.
However, even if clouds are now causing global average cooling, it is not the same everywhere, and furthermore that cooling may decrease when the climate warms up, so that clouds would intensify future Greenhouse warming.
That imbalance is called "Cloud Forcing", and it has been estimated from Earth radiation data by attempting to remove all the data affected by clouds, giving a picture of an imaginary "Non-cloud" Earth.
climate.gsfc.nasa.gov /~cahalan/Radiation/NoCloud.html   (550 words)

 Wikinfo | Cloud
Clouds reflect all light and are white, but they can appear grey or even fl if they are so thick or dense that sunlight cannot pass through.
Clouds on other planets often consist of material other than water, depending on local atmospheric conditions (what gases are present, and the temperature).
The clouds tend to be wispy, and are often transparent.
www.wikinfo.org /wiki.php?title=cloud   (527 words)

 NOAA OGP Programs   (Site not responding. Last check: 2007-10-11)
Mean shortwave surface cloud forcing for the 8-year period of July 1983 to June 1991 from the NASA SRB data set.
Mean cloud optical thickness (dimensionless) for the 8-year period of July 1983 to June 1991 from the NASA SRB data set.
Mean total surface cloud forcing for the 8-year period of July 1983 to June 1991 from the NASA SRB data set.
www.ogp.noaa.gov /mpe/gapp/abstr/2001/iskenderian_2003_figs.html   (314 words)

 EO Observation Deck: Cloud Radiative Forcing Dataset View
Clouds are one of the greatest areas of scientific uncertainty with respect to how much they influence climate on a global scale.
The term "cloud radiative forcing" refers to the effects clouds have on both sunlight and heat in the atmosphere.
The image above is a false-color map showing the magnitudes of cloud radiative forcing (in Watts per square meter) for the given month(s).
earthobservatory.nasa.gov /Observatory/Datasets/cldforc.erbe.html   (211 words)

 Climate Change 2001: The Scientific Basis
The conservation equations to determine the cloud water concentration are written at the scale explicitly resolved by the model, whereas a large part of the atmospheric dynamics generating clouds is sub-grid scale.
In warm clouds these microphysical processes include the collection of water molecules on a foreign substance (hetero-geneous nucleation on a cloud condensation nucleus), diffusion, collection of smaller drops when falling through a cloud (coalescence), break-up of drops when achieving a certain threshold size, and re-evaporation of drops when falling through a layer of unsaturated air.
Measurements of cloud drop size distribution indicate a significant difference in the total number of drops and drop effective radius in the continental and maritime atmosphere, and some studies indicate that inclusion of more realistic drop size distribution may have a significant impact on the simulation of the present climate (Hahmann and Dickinson, 1997).
www.grida.no /climate/ipcc_tar/wg1/271.htm   (829 words)

 An annual cycle of Arctic surface cloud forcing at SHEBA
We present an analysis of surface fluxes and cloud forcing from data obtained during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment, conducted in the Beaufort and Chuchki Seas and the Arctic Ocean from November 1997 to October 1998.
A yearlong data set of measurements, obtained on a multiyear ice floe at the SHEBA camp, was processed in 20-day blocks to produce the annual evolution of the surface cloud forcing components: upward, downward, and net longwave and shortwave radiative fluxes and turbulent (sensible and latent heat) fluxes.
We found that clouds act to warm the Arctic surface for most of the annual cycle with a brief period of cooling in the middle of summer.
www.agu.org /pubs/crossref/2002/2000JC000439.shtml   (387 words)

 Modeling Cloud Forcing in the Tropical West Pacific   (Site not responding. Last check: 2007-10-11)
By taking daily average cloud forcing and scatter plotting LWCF vs. SWCF, a relationship similar to the full model (CCM3) can be seen.This relationship is not in good agreement with ERBE satalite data and changes are made to the model to investigate what features improve this relationship.
Image 3 shows a time/height contour plots of cloud mixing ratio as seen by the radiation scheme for a highly convective 10 day period where the SCCM3 predicted temperature poorly (not shown).
It appears that the direct effect (latent heating) improves the simulation but the clouds are optically too deep or too persistent with prognostic microphysics.
www.arm.gov /science/research/show.php?id=R00004   (600 words)

The cloud population and its temporal evolution, with corresponding properties derived from satellite observations of the COARE region, was also compared.
Modified cloud optical properties that reproduce recent observations of short-wave absorption were tested in the CRM to examine the effects on cloud formation and lifetime.
The results of the intercomparison indicated that details of the cloud simulations (such as cloud patterns and organization) varied considerably among LES but the average energetics and turbulence statistics were rather insensitive to SGS physics and numerics.
box.mmm.ucar.edu /asr97/role_of_clouds.html   (3624 words)

 introduction   (Site not responding. Last check: 2007-10-11)
It is important to note that, the term ³radiative forcing² denotes not only the optical properties of aerosols (such as optical depth, single scattering albedo and phase function) but also the changes in radiative fluxes (in Wm-2) due to aerosols in clear and cloudy skies.
The goal is to link cloud droplet concentrations and chemical composition to the physical and chemical properties of the subcloud CCN, and in turn, to link the properties of the CCN to the aerosol plume.
The in situ cloud observations are also used to link the cloud optical depths and droplet sizes derived from satellite and aircraft radiometer data to those actually found in the clouds.
www-indoex.ucsd.edu /publications/implementation   (2843 words)

In the longwave, clouds generally reduce the radiation emission to space and thus result in a heating of the planet.
While in the solar (or shortwave), clouds reduce the absorbed solar radiation, due to a generally higher albedo than the underlying surface, and thus result in a cooling of the planet.
In the summer hemisphere, the negative shortwave cloud forcing dominates the positive longwave cloud forcing, and the clouds result in a cooling.
cimss.ssec.wisc.edu /wxwise/homerbe.html   (1911 words)

 MODIS Atmosphere: Cloud Product
Cloud-particle phase (ice vs. water, clouds vs. snow), effective cloud-particle radius, and cloud optical thickness are derived using the MODIS visible and near-infrared channel radiances.
First, clouds play a critical role in the radiative balance of the Earth and must be accurately described in order to assess climate and potential climate change accurately.
Key radiative properties of clouds such as phase, optical thickness, and temperature may be retrieved using MODIS instruments with unprecedented resolution.
modis-atmos.gsfc.nasa.gov /MOD06_L2/index.html   (538 words)

 JPL Air Sea Interaction & Climate Team - Science
The correlation between high cloud and SST are, to some extent, opposite to the correlation between low cloud and SST.
The correlation between total cloud and SST appears to be a sum of the effects of various type of clouds.
In this area, SST anomalies has a strong negative correlation with the high cloud and a strong positive correlation with low clouds; the result is a weak correlation with the total cloud forcing.
airsea-www.jpl.nasa.gov /science/cloud_forcing.html   (202 words)

 Recent SCM - IAMAS-Melbourne Jul 97
The model produced cloud forcing terms averaged over the 79 days of the three time periods are shown in Table 2 along with measured values from the same periods from ISCCP data.
The lack of clouds in the 900-400 mb region is due to the absence of cumulus detrainment in this region and may be an artifact of the particular cumulus convection routine that was used.
We can say fairly confidently is that the cloud optical properties and hence the cloud forcing terms are sensitive to both the inclusion of interactive cloud liquid water and to the cloud droplet radius parameterization.
meteora.ucsd.edu /~iacob/scm_recent/coare/iamas97.html   (1268 words)

 Climate forcings in the Industrial era -- Hansen et al. 95 (22): 12753 -- Proceedings of the National Academy of ...
The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change.
A climate forcing is an imposed perturbation of the Earth's energy balance with space (1).
Climate forcing by ozone is uncertain because ozone change as a function of altitude is not well measured.
www.pnas.org /cgi/content/full/95/22/12753   (3747 words)

 web_intro   (Site not responding. Last check: 2007-10-11)
A thorough understanding of cloud properties and their associated radiative feedbacks is key to the predictability of future climate.
Clouds are known to enhance both the warming and cooling of the planet via the absorption and re-radiation of outgoing longwave radiation and reflection of incoming shortwave radiation, respectively.
The net effect of clouds on the radiation budget is referred to as cloud radiative forcing, where positive forcing corresponds to net warming and negative forcing implies net cooling.
www.rci.rutgers.edu /~secora/web_intro.html   (902 words)

 Cloud-Radiative Forcing and Climate: Results from the Earth Radiation Budget Experiment -- RAMANATHAN et al. 243 ...
Palaeoenvironmental evidence for solar forcing of Holocene climate: linkages to solar science.
Radiative Climate Forcing by the Mount Pinatubo Eruption.
How to Fix the Clouds in Greenhouse Models: Climate models are moving toward the realistic simulation of clouds needed to calculate the size of the greenhouse warming.
www.sciencemag.org /cgi/content/short/243/4887/57   (598 words)

 3.2 The Cloud Sensitivity Study: Terrestrial Radiation
An accurate and also simple parameterization of cloud optical properties such as extinction coefficient, single scattering albedo and asymmetry factor is needed in radiative transfer calculations of the terrestrial radiation in climate models if the climate system is sensitive to the single scattering properties in the longwave radiation.
Figure 4 and 5 show that the longwave cloud radiative forcing is indeed sensitive to the changes in cloud equivalent radius if the cloud is not too thick.
Figure 6 shows that clouds with different equivalent radii may have significantly different longwave radiative forcing.
greenfield.fortunecity.com /healing/195/paper/sense/node5.html   (248 words)

 Cloud (disambiguation) - Wikipedia, the free encyclopedia
A cloud is a visible mass of condensed droplets or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body.
Cloud albedo, measure of the reflectivity of a cloud
Cloud forcing, the difference between the radiation budget components for average cloud conditions and cloud-free conditions
en.wikipedia.org /wiki/Cloud_(disambiguation)   (521 words)

 FIRE/SHEBA Workshop Abstract - Douglas Spangenberg   (Site not responding. Last check: 2007-10-11)
Clouds have similar visible brightnesses and infrared temperatures as the underlying snow making it difficult to detect them in satellite imagery.
Cloud forcing analysis will be presented from March through October 1998 over the arctic ocean to include both the SHEBA and Barrow, AK sites.
Cloud forcing estimates computed for the SHEBA domain encompass the area of 72°N to 80°N and 180°W to 150°W. The Barrow domain will be of similar size.
eosweb.larc.nasa.gov /ACEDOCS/workshop/abstracts/spangenberg_cloud.html   (329 words)

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