Aerosol precipitation interaction

Andreae M, Rosenfeld D (2008) Aerosol-cloud-precipitation interactions. Part 1. The nature and sources of cloud-active aerosols. Earth Sci Rev 89 13-41... 

For the realisation of all aerosol forcing mechanisms in integrated systems it is necessary to improve not only ACTMs, but also NWP HIRLAM. The boundary layer structure and processes, including radiation transfer (Savijarvi 1990), cloud development and precipitation must be improved. Convection and condensation schemes need to be adjusted to take the aerosol-microphysical interactions into account, and the radiation scheme needs to be modified to include the aerosol effects. Incorporation of the aerosol direct effects (radiation forcing) is very problematic within the Savijarvi (1990) radiation scheme. 

Only tentative conclusions may be drawn from rain data concerning aerosols. The interactive processes between rain and aerosols such as wash out, rain out, and precipitation scavenging are not well understood. It has been pointed out by Wilkniss and Bressan (40), for example, that elemental ratios in low Na content rain may be the result of the rainforming process rather than being representative of the aerosols present in the air parcel. Indeed, better aerosol data will assist the description of the rain-forming processes rather than vice-versa. 

The results obtained by Menon et al. (2003) revealed substantial differences in the use of physically substantiated prognostic schemes of how aerosol acts taking into account vertical velocity and empirical schemes based on diagnostic data on the vertical velocity at cloud bottom level. Prognostic schemes are characterized by the stronger variability of results compared with diagnostic ones because of differences in scheme of the interaction between the processes of aerosol activation and precipitation of drizzle when calculating N. 

Charged aerosols and aerosol charging Microcontamination electrostatic precipitation atmospheric electricity aerosol sampling and measurement ion-particle interactions. 

The first application is the simulation of a mineral dust event over West Africa in March 2004. During this event there were high wind speeds and low temperature observed in the Sahara and heavy precipitations over Libya (Knipperts and Fink 2006). Figure 6.2 shows the simulated dust loading for 4th March 2004 at 12 UTC. To investigate the impact of the dust aerosols on radiation two simulations were performed one with no interaction between the actual aerosol concentration and radiation, and another that takes into account the interaction. 

The acidity of precipitation is mainly governed by its content of sulphate, nitrate and ammonium ions. It is closely related to the chmical composition of the aerosols, and may to a large extent depend on the pathway of the polluted air masses. The effects of the acid precipitation are not simply related to the acidity of the precipitation, but are the result of complex interactions in which all the major ions in precipitation are of significance. 

Reality is often quite different. When a supercritical fluid mixture expands into pressures as high as ambient conditions, the resultant expansion plume can be a complex mixture it is a high velocity gas stream that entrains precipitated particles of extracted materials and often frozen carbon dioxide. Much adjustment needs to take place in the collection zone in order to achieve something close to 100 % recoveries of solutes with concentration ranges from parts per billion (PCBs) up to 50 % (total fat in a chocolate candy). Besides the flow dynamics of the expansion, several physicochemical parameters cause the deviation from the initial simple model. They include, but are not limited to, volatility of the solute, degree of co-precipitation of solid carbon dioxide (followed almost immediately with uncontrolled subhmation of the solid), aerosol formation, surface tension, occlusion in solid carbon dioxide, rebound from impinging surface, and many other interacting phenomena. 

Interactions among aerosols, clouds and precipitation are critical to shaping the climate system. Aerosols, cloud and precipitation are intrinsically linked (Figs. 4.8... 

Cloud formation and dynamics is a subject which requires considerable information from almost all the areas of aerosol microphysics [1.37,18]. Thermodynamics determines aerosol growth to cloud droplet size, and electrical processes in clouds may play a role in the onset of precipitation. Clouds may scavenge the atmosphere of aerosols through capture of particles by cloud droplets, with the rates and mechanisms described by subtleties of their interaction forces and aspects of kinetic theory. 

Finally, mention must be made of the effects of other materials released into water in the containment over the course of an accident. Some of these materials are released to the containment during core degradation. The effects of these materials on water pH are not well understood. Hot water will leach calcium hydroxide from concrete and this can cause an increase in pH. Core debris interactions with concrete release copious quantities of aerosol that are rich in species like CaO, Na20 and K2O that will dissolve in water to form hydroxide ions and raise the pH. On the other hand, CaO can precipitate buffers intended to control the water pH. 

Atmospheric sciences includes the fields of physics and chemistry and the study of the composition and dynamics of the layers of air that constitute the atmosphere. Related topics include climatic processes, circulation patterns, chemical and particulate deposition, greenhouse gases, oceanic temperatures, interaction between the atmosphere and the ocean, the ozone layer, precipitation patterns and amounts, climate change, air pollution, aerosol composition, atmospheric chemistry, modeling of pollutants both indoors and outdoors, and anthropogenic alteration of land surfaces that in turn affect conditions within the ever-changing atmosphere. 

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