Clouds climate

Solar Evaporation. Recovery of salts by solar evaporation (1 3) is favored in hot dry climates. Solar evaporation is also used in temperate 2ones where evaporation exceeds rainfall and in areas where seasons of hot and dry weather occur. Other factors (4,5) affecting solar pond selection are wind, humidity, cloud cover, and land terrain. 

DMS has been observed in the marine atmosphere since the early 1970s, but it was not until the mid-1980s that there was interest in this gas as being a natural source for sulfate CCN. Sulfate aerosols are, in number terms, the dominant source of CCN. The major role clouds play in the climate system leads to possible climatic implications if changes to DMS production occurred. Furthermore, the dependence of this production on environment conditions means that scope for a feedback process arises this feedback is called the Charlson hypothesis. ... 

Numerous analyses of data routinely collected in the United States have been performed by the U.S. National Climatic Center, results of these analyses are available at reasonable cost. The joint frequency of Pasquill stability class, wind direction class (primarily to 16 compass points), and wind speed class (in six classes) has been determined for various periods of record for over 200 observation stations in the United States from either hourly or 3-hourly data. A computer program called STAR (STability ARray) estimates the Pasquill class from the elevation of the sun (approximated from the hour and time of year), wind speed, cloud cover, and ceiling height. STAR output for seasons and the entire period of record can be obtained from the Center. Table 21-2 is similar in format to the standard output. This table gives the frequencies for D stability, based on a total of 100 for all stabilities. 

Clouds cover roughly two-thirds of our earth s surface and play an important role in influencing global climate by affecting the radiation budget. Cirrus clouds are one example of a cloud type whose optical properties are not accurately known. Cirrus clouds form in the upper troposphere and are composed almost exclusively of non-spherical ice crystal particles. The impact of cloud coverage on dispersion of pollution in the atmosphere is an area of great concern and intensive study. 

Water vapor can be a climate warming force when it traps heat, or can cause either climate warming or cooling when it takes the form of clouds, which reflect incoming solar energy away from Earth. 

One such feedback is the influence of clouds and water vapor. As the climate warms, more water vapor enters the atmosphere. But how much And which parts of the atmosphere, high or low And how does the increased humidity affect cloud formation While the relationships among clouds, water vapor, and global climate are complicated in and of themselves, the situation is further complicated by the fact that aerosols exert a poorly understood influence on clouds. 

The last published report of the IPCC acknowledges that the single largest uncertainty in determining the climate sensitivity to either natural or anthropogenic changes are clouds and their effects on radiation and their role in the hydrological cycle. .. At the present time, weaknesses in the parameterization of cloud formation and dissipation are probably the main impediment to improvements in the simulation of cloud effects on climate (IPCC, 1995, p. 346). 

Climatic conditions such as cloud cover, wind speed,... 

How well do GCMs simulate the spatial variability of climatic change Today s GCMs utilize data grids that partition the atmosphere into cells, each covering an area about the size of Colorado. A mean state of the atmosphere (temperature, humidity, cloud cover, for example) is computed for each cell. Consequently, any ou ut statistics (the prediction) has a lower spatial resolution (more genei ized, less detailed) than the real atmosphere is likely to manifest. 

Climate is often viewed as the aggregate of all of the elements of weather, with quantitative definitions being purely physical. However, because of couplings of carbon dioxide and many other atmospheric species to both physical climate and to the biosphere, the stability of the climate system depends in principle on the nature of feedbacks involving the biosphere. For example, the notion that sulfate particles originating from the oxidation of dimethylsulfide emitted by marine phytoplankton can affect the albedo (reflectivity) of clouds (Charlson et ai, 1987). At this point these feedbacks are mostly unidentified, and poorly quantified. 

Although it is one of the smallest reservoirs in terms of water storage, the atmosphere is probably the second most important reservoir in the hydrosphere (after the oceans). The atmosphere has direct connections with all other reservoirs and the largest overall volume of fluxes. Water is present in the atmosphere in solid, liquid, and vapor forms, all of which are important components of the Earth s natural greenhouse effect. Cycling of water within the atmosphere, both physically (e.g. cloud formation) and chemically, is also integral to other biogeochemical cycles and climate. Consult Chapter 17 for more details. 

In addition to biogeochemical cycles (discussed in Section 6.5), the hydrosphere is a major component of many physical cycles, with climate among the most prominent. Water affects the solar radiation budget through albedo (primarily clouds and ice/snow), the terrestrial radiation budget as a strong absorber of terrestrial emissions, and global temperature distribution as the primary transporter of heat in the ocean and atmosphere. 

Five components of the hydrosphere play major roles in climate feedbacks - atmospheric moisture, clouds, snow and ice, land surface, and oceans. Changes to the hydrologic cycle, among other things, as a result of altered climate conditions are then referred to as responses. Interactions with climate can best be explored by examirung potential response to a climate perturbation, in this case, predicted global warming. 

Clouds. Cloud feedback mechanisms are among the most complex in the climate system, due to the many disparate roles played by clouds, which control a large portion of the planetary albedo but also trap terrestrial radiation, reducing the energy escaping to space. To complicate matters further, different t5 es of clouds behave differently in the same environment. In the present climate mode, clouds have... 

On the average, the air over roughly half of the Earth s surface has an upward velocity and half has a downward velocity. This frontal activity (Section 7.5.3) and the interactions of marine air with the cold ocean surface result in about half of the Earth being covered by clouds and half being clear. As will be discussed in Chapter 17, this large fractional cloud cover is extremely important to the Earth s climate because it controls the planetary albedo (reflectivity). 

The condensed phases also are important to the physical processes of the atmosphere however, their role in climate poses an almost entirely open set of scientific questions. The highest sensitivity of physical processes to atmospheric composition lies within the process of cloud nucleation. In turn, the albedo (or reflectivity for solar light) of clouds is sensitive to the number population and properties of CCN (Twomey, 1977). At this time, it appears impossible to predict how much the temperature of the Earth might be expected to increase (or decrease in some places) due to known changes in the concentrations of gases because aerosol and cloud effects cannot yet be predicted. In addition, since secular trends in the appropriate aerosol properties are not monitored very extensively there is no way to know... 

Kiehl, J. T. (1994). Sensitivity of a GCM climate simulation to differences in continental versus maritime cloud drop size, /. Geophys. Res. 99, 23107-23115. 

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