Fog and regulation of the global climate
Fog is a type of cloud that forms close to the ground when air temperature drops below its dew point, leading to condensation. It can form and dissolve rapidly, with different types of fog identified based on the processes that create them. For instance, radiation fog typically occurs in low-lying areas during clear, calm nights, while advection fog forms in coastal regions when warm air passes over cold surfaces. Other types include upslope fog, which develops as air rises over mountain slopes, and evaporation fog, which arises when cold, dry air moves over warm, moist surfaces.
Fog plays a significant role in regulating the climate by influencing air and surface temperature patterns. Its high moisture content provides thermal inertia, meaning it can stabilize temperatures by trapping outgoing heat at night and blocking incoming solar radiation during the day. While fog has a cooling effect overall, it can also contribute to warming near the surface. As climate change progresses, an increase in fog and low clouds is anticipated due to warmer air holding more water vapor. This increase could have implications for visibility and air quality, as fog can trap pollutants and contribute to smog formation. Moreover, while coastal fog levels have been observed to decline in recent years, experts emphasize the need for global actions, such as reducing greenhouse gas emissions, to mitigate these changes and support the continuity of fog as a climatic phenomenon.
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Fog and regulation of the global climate
Definition
Fog is a cloud near the ground. Fog forms as the temperature of air falls below its dew point and condensation occurs. Fog also forms and dissolves rapidly, depending on whether the temperature is higher or lower than the dew point. Fogs are named based on the specific process through which the humidity has reached its saturation point, causing the fog to form.
Radiation fog forms as air temperature falls below the by a rapid radiation cooling through a clear, calm night. The cool and heavy air containing this type of fog often settles in low-lying areas, such as mountain valleys. Most inland fogs are radiation fogs. Advection fog usually forms in coastal regions as warm air blows over a cold surface and loses heat to the underlying surface. Upslope fog forms as air blows over mountain slopes, becomes cool, and reaches saturation.
Evaporation fog occurs as a cold, dry air blows over warm, moist surfaces. Thermal and humidity gradients between the two entities facilitate rapid evaporation from the surface. As the warmer, moist air from the ground mixes with cold, dry air above, it reaches saturation and forms fog. Steam fog over lakes during late fall and early winter is a typical form of evaporation fog.
Significance for Climate Change
Fog, as a surface-level cloud, has roughly the same climatic effects as low-level clouds. Fog dictates air and surface temperature patterns by controlling the amount of radiation that enters and leaves the surface. High moisture content imparts fog with great thermal inertia. Thus, once a fog has formed, it will prevent air temperature from changing. In the morning, fog’s high allows less incoming solar radiation to reach the surface. Thus, morning fogs keep air temperatures low, allowing only gradual increases until the fog evaporates. As a result, fogs decrease daytime high temperatures.
In the night, fog traps outgoing longwave radiation and prevents air temperature from dropping as it would on a clear night. Fog also potentially warms the air near the surface, because is a warming process. Overall, however, fog has a greater cooling effect than warming effect on Earth. As global warming continues, greater incidences of fog and lower clouds are expected, because warmer air can contain more water vapor. This increased fog may affect humans by reducing visibility and by trapping air pollutants to form smog. Fog can also produce precipitation, in the form of rain drizzle and light snow. As global climate change advanced throughout the 2010s and 2020s, coastal fog levels declined. Experts called for worldwide action, including a reduction in greenhouse gas emissions, to preserve coastal fog levels.
Berwyn, Bob, et al. "With a Warming Climate, Coastal Fog Around the World Is Declining." Inside Climate News, 10 Oct. 2021, insideclimatenews.org/news/10102021/coastal-fog-global-warming/. Accessed 20 Dec. 2024.
"The Future of Fog." Public Policy Institute of California, www.ppic.org/blog/the-future-of-fog/. Accessed 20 Dec. 2024.