Cloud water cycle

The Water Cycle. The evaporation of water from land and water surfaces, the transpiration from plants, and the condensation and subsequent precipitation of rain cause a cycle of transportation and redistribution of water, a continuous circulation process known as the hydrologic cycle or water cycle (see Fig. 86). The sun evaporates fresh water from the seas and oceans, leaving impurities and dissolved solids behind when the water vapor cools down, it condenses to form clouds of small droplets that are carried across the surface of the earth as the clouds are moved inland by the wind and are further cooled, larger droplets are formed, and eventually the droplets fall as rain or snow. Some of the rainwater runs into natural underground water reservoirs, but most flows, in streams and rivers, back to the seas and oceans, evaporating as it travels. 

Dry air rising in the atmosphere has to expand as the pressure in the atmosphere decreases. This pV work decreases the temperature in a regular way, known as the adiabatic lapse rate, Td, which for the Earth is of order 9.8 Kkm-1. As the temperature decreases, condensable vapours begin to form and the work required for the expansion is used up in the latent heat of condensation of the vapour. In this case, the lapse rate for a condensable vapour, the saturated adiabatic lapse rate, is different. At a specific altitude the environmental lapse rate for a given parcel of air with a given humidity reaches a temperature that is the same as the saturated adiabatic lapse rate, when water condenses and clouds form Clouds in turn affect the albedo and the effective temperature of the planet. Convection of hot, wet (containing condensable vapour) air produces weather and precipitation. This initiates the water cycle in the atmosphere. Similar calculations may be performed for all gases, and cloud layers may be predicted in all atmospheres. 

Mitchell, North Carolina, Air Waste, 43, 1074-1083 (1993). Arakaki, T., C. Anastasio, P. G. Shu, and B. C. Faust, Aqueous-Phase Photoproduction of Hydrogen Peroxide in Authentic Cloud Waters Wavelength Dependence, and the Effects of Filtration and Freeze-Thaw Cycles, Atmos. Environ., 29, 1697-1703 (1995). Arakaki, T., and B. C. Faust, Sources, Sinks, and Mechanisms of Hydroxyl Radical ( OH) Photoproduction and Consumption in Authentic Acidic Continental Cloud Waters from Whiteface Mountain, New York The Role of the Fe(r) (r = II, III) Photochemical Cycle, . /. Geophys. Res., 103, 3487-3504 (1998). Atkinson, R., D. L. Baulch, R. A. Cox, R. F. Hampson, Jr., J. A. Kerr, M. J. Rossi, and J. Troe, Evaluated Kinetic and Photochemical... 

Microscopic dust or fine particles of chemical salts attract water vapour particles i.e. they are hygroscopic. Water vapour in the air needs hygroscopic nuclei to condense and form clouds when the air temperature falls below dew point. If there were no microscopic dust particles in the atmosphere, there would be no clouds, no precipitation and no water cycle. 

All forms of condensation do not play a role in the water cycle. It is the many splendoured cloud that is vital. How are clouds formed ... 

Global water cycle. Impact of cloud feedbacks. 

Figure 7.4 Effect of pH cycling on the dissolution of manganese from crustal aerosols under conditions likely both in the atmosphere and on mixing into seawater (Spokes and Jickells, 1996). Manganese shows high solubility at a typical cloud water pH of 2. Solubility decreases slightly at rainwater pH of 5.5 and rapidly at pH 8. Extensive solution phase removal is not seen at pH 8 under conditions designed to mimic seawater, perhaps due to the formation of soluble MnCI+ and MnSOl-. Low pH cycling and inorganic complexation under seawater conditions increase manganese solubility six times over that seen at pH 8 alone.

Answer 1.3 Two segments of the water cycle were concealed the evaporation of water from the ocean, forming clouds that transport water into the continents, and the flow of water underground. 

Because of the existence of these tropospheric sinks, phosgene is unlikely to have a detrimental effect on the stratosphere [1889], such as the depletion of the ozone layer (but see Section 3.7.2). However, the precise fate of phosgene in the troposphere is closely linked to the water cycle, particularly the presence of clouds and their type of behaviour. 

The problems related to the water cycle will also not be considered in spite of the fact that, taking into account its quantity and atmospheric effects, water is one of the most important trace materials. This omission is explained by a historical precedent. The study of the atmospheric cycle of the water as well as the measurement of its concentration were included in the past in the program of other branches of atmospheric science. Thus, the formation of clouds and precipitation, the subject of the cloud physics (e.g. Mason, 1957, Fletcher, 1962), will only be discussed in relation with the wet removal of aerosol particles and water-soluble gases. 

The condensation of water vapor and its precipitation from the atmosphere in the form of rain, snow, sleet, or hail are important not only for the water cycle, but also because they bring to the earth surface other atmospheric constituents, primarily those substances that have a pronounced affinity toward water in the condensed state. Cloud and precipitation elements may incorporate both aerosol particles and gases. The uptake mechanisms are discussed in this chapter, together with the inorganic composition of cloud and rain water that they determine. These processes are, in principle, well understood. Another subject requiring discussion is the occurrence of chemical reactions in the liquid phase of clouds. The oxidation of S02 dissolved in cloud water is considered especially important. As a result of laboratory studies, the conversion of S02 to sulfate is now known to proceed by several reaction pathways in aqueous solution. 

Most of the Earth s water is found in the oceans and lakes. Through the water cycle, water evaporates into the atmosphere and condenses into clouds. Water then falls to the Earth in the form of precipitation, returning to the oceans and lakes on falling on land. Water on the land may return to the oceans and lakes as runoff or seep from the soil as groundwater. 

Arakaki T. and Faust B. C. (1998) Sources, sinks, and mechanisms of hydroxyl radical ( OH) photoproduction and consumption in authentic acidic continental cloud waters from Whiteface Mountain, New York the role of the Fe(r) (r = II, III) photochemical cycle. J. Geophys. Res. 103, 3487-3504. 

There are cycles for all elements and many compounds. The water cycle is very important to us. We use water to drink, and it is either added to the air by evaporation or it is added to the soil after excretion. From there, it could be used countless times by other organisms, many of which are microscopic in size. Perhaps that water is eventually taken up through plant roots and moves up the stem to the leaves, where it evaporates into the atmosphere. Those same water molecules condense in clouds, and rain upon the land. The water collects in streams and then in rivers. It may be there that the water is pumped into our water systems to be drunk again. 

The water cycle is driven by processes that force the movement of water from one reservoir to another. Evaporation from the oceans and land is the primary source of atmospheric water vapor (Fig. 2.36). Water vapor is transported, often over long distances (which characterize the type of air masses), and eventually condenses into cloud droplets, which in turn develop into precipitation. Globally, there is as much water precipitated as is evaporated, but over land precipitation exceeds evaporation and over oceans evaporation exceeds precipitation (Fig. 2.35). The excess precipitation over land equals the flow of surface and groundwater from continents to the oceans. Flowing water also erodes, transports and deposits sediments in rivers, lakes and oceans, affecting the quality of water. 

---