Marine salt aerosol , originally from sea spray, is one of the most distributed natural aerosols. Sea salt aerosols are characterized as non-light-absorbing, highly hygroscopic, and have coarser particle sizes. Some marine predominant aerosols can have a single scattering albedo of ~ 0.97. Due to hygroscopic, marine salt particles can serve as highly efficient cloud condensation nuclei (CCN), altering the cloud's reflectivity, lifetime, and deposition process. According to the IPCC report, the total flux of sea salt from the ocean to the atmosphere is ~ 3300 Tg/year.
Video Sea salt aerosol
Formation
Many physical processes above sea level can produce marine salt aerosols. One common cause is the explosion of air bubbles, which are suppressed by wind pressure during the formation of whitecap. Another is tearing drops from wave crests. Wind speed is a key factor for determining production levels in both mechanisms. Concentrations of the number of marine salt particles can be up to 50Ã, »- -3 or more with strong winds (& gt; 10 ms -1 ), compared to ~ 10 × cm -3 or less under the moderate wind regime. Due to the dependence on wind speeds, it can be expected that the production of marine salt particles and their impact on climate can vary with climate change.
Maps Sea salt aerosol
Characteristics
Chemical compounds
Marine aerosol salts consist mainly of sodium chloride (NaCl), but other common chemical ions in seawater, such as K , Mg 2 , Ca 2 , SO 4 2 - and so on, can also be found. Recent studies reveal that marine salt aerosols contain large amounts of organic matter. For the most part, organic matter is internally blended due to the drying of air bubbles at the organic-rich ocean surface. The fraction of organic components increases with decreasing particle size. The organic material contained changes the optical properties of sea salt as well as hygroscopicity, especially when some soluble organic matter is induced.
Size
Marine salt aerosol size ranges from 0.05 to 10 Ã, μm in diameter, with most of the mass concentrated in the super-micron range (coarse mode), and the highest concentration of numbers in the sub-micron range. Correspondingly, marine salt aerosols have a wide range of atmospheric life. Since marine salt aerosols are hygroscopic, their particle size may vary from moisture to factor 2. Sea aerosol salts affect the formation of sulfate aerosols in different ways because of different sizes. Extremely small aerosol sea salts, which are below the critical diameter for droplet activation at low supersaturation, may serve as the core for sulfate particle growth, while larger ocean salt particles serve as a sink for hydrogen sulfate gas (H 2 SO 4 ) molecules, reducing the amount of sulfate available for formation of accumulated mode particles.
Impact
Changing the Earth's radiation budget
Marine salt aerosols can alter the radiation budget of the Earth through direct sunlight radiation (direct effects), and indirectly alter cloud albedo by serving as CCN (indirect effects). Different models provide different predictions of the radiative forcing mean that are induced by the direct effects of sea salt, but most previous studies give a rate of about 0.6 to 1.0 W m -2 . Radiation coercion induced by indirect effects indicates greater variation in model predictions due to the indirect parameterization of aerosol effects. However, model results provide a stronger indirect effect on the Southern Hemisphere.
Affects the precipitation process
Like all other soluble aerosols, normal sea salt enhancement suppresses deposition in warm clouds by increasing the droplet concentration of cloud droplets and reducing the size of cloud droplets. Also, they reinforce rainfall in mixed phase clouds because once a small drop of pressed cloud is lifted above the freezing level, more latent heat content will be released due to freezing cloud drops. Additionally, adding giant sea salt aerosols to contaminated clouds can speed up the deposition process because the CCN giants can convert to large particles that collect smaller clouds of droplets and grow into raindrops. Clouds of clouds formed in aerosol giant sea salt can grow much faster by condensation that cloud drops formed on small soluble aerosol particles, such as giant ocean salt droplets drops can keep concentrated drops for a long time after they are brought to the clouds. Such droplets may have condensate growth rates more than twice as fast as droplets formed on small aerosol particles, and unlike normal cloud droplets, the droplets formed in the largest giant sea salt aerosols can even grow by condensation in cloudy bottom streams.
References
Source of the article : Wikipedia
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