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Atmospheric Processes

Atmospheric processes play important roles in shaping the Earth’s energy and water cycles. With the help of numerical models, observations and theories, GFDL scientists conduct cutting-edge research to advance the fundamental understanding of atmospheric processes in governing climate variability and change, with the goal of developing more accurate representations of them in climate models. This work makes it possible to quantify the key characteristics of natural and anthropogenic perturbations to the climate system (such as greenhouse gases, aerosols, land use, volcanoes and solar radiation), and to elucidate the mechanisms through which these perturbations influence global and regional climate.

Aerosols and Climate

Aerosols and Climate

Aerosols refer to fine solid or liquid particles suspended in the atmosphere, where they reside typically for days to weeks before falling to the ground or being washed out by rain or snow. They arise both from human activities involving burning of fossil fuels, biofuels and veg and from natural sources (such as desert dust, sea spray and volcanic eruptions). Aerosol particles are tiny, but numerous, and often comprise of a number of inorganic and organic substances. Visible forms of atmospheric aerosol plumes include smoke, smog, haze and dust.

Clouds and Convection

Clouds and Convection

Clouds play a central role in both the hydrological and energy cycles of our planet. Water evaporates directly at the surface or is transpired from the soil through vegetation. Once in the atmosphere, moisture is transported and redistributed by winds. Moisture condenses to form small cloud droplets or ice crystals when the temperature becomes cold enough. If clouds contain a sufficient amount of condensed water or ice, small particles undergo a transformation into larger particles that produce precipitation. Precipitation returns the water back to the surface in the form of rain or snow.

Mineral Dust Cycle

Mineral Dust Cycle

Mineral dust in the atmosphere is composed essentially of clay and silt particles, whose diameters vary between 0.1 to 20 micro-meters (~1/10 of hair). Larger particles, such as sand, are not included because they are too quickly removed from the atmosphere by gravitational settling. The main sources of silt and clay are in topographic depressions where alluvium has been accumulated. Dust is emitted when the surface winds are strong enough to break soil cohesion, which may only happen if there is no ground cover and the soil is dry. Human activities may be a source of dust or disturb soils and enhance wind erosion.

Radiative Forcings

Radiative Forcings

Atmospheric radiative transfer is the science of understanding how electromagnetic radiation emitted by both the Sun and Earth interacts with the gases, clouds and particles making up our atmosphere. The changes in energy due to these interactions are responsible for many variations in temperature and weather that we experience in everyday life. For example, cloudy nights are normally warmer than clear nights because of radiative transfer processes, with the nighttime clouds reducing the energy lost to space by the surface of the planet.