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Drizzle in Norfolk, England. Row of poplars in the drizzle - geograph.org.uk - 591822.jpg
Drizzle in Norfolk, England.

Drizzle is a light liquid precipitation consisting of liquid water drops smaller than those of rain – generally smaller than 0.5 mm (0.02 in) in diameter. [1] Drizzle is normally produced by low stratiform clouds and stratocumulus clouds. Precipitation rates from drizzle are on the order of a millimetre (0.04 in) per day or less at the ground. Owing to the small size of drizzle drops, under many circumstances drizzle largely evaporates before reaching the surface and so may be undetected by observers on the ground. The METAR code for drizzle is DZ and for freezing drizzle is FZDZ. [2]



While most drizzle has only a minor immediate impact upon humans, freezing drizzle can lead to treacherous conditions. Freezing drizzle occurs when supercooled drizzle drops land on a surface whose temperature is below freezing. [3] These drops immediately freeze upon impact, leading to the buildup of sheet ice (sometimes called black ice) on the surface of roads.


Drizzle in Bournemouth, England. Drizzle in Bascott Road - geograph.org.uk - 1767325.jpg
Drizzle in Bournemouth, England.

Drizzle tends to be the most frequent form of precipitation over large areas of the world's oceans, particularly in the colder regions of the subtropics. These regions are dominated by shallow marine stratocumulus and trade wind cumulus clouds, which exist entirely within the marine boundary layer. Despite the low rates of surface accumulation, it has become apparent[ to whom? ] that drizzle exerts a major influence over the structure, coverage, and radiative properties of clouds in these regions.

This has motivated scientists to design more sophisticated and sensitive instruments such as high-frequency radars that can detect drizzle. These studies have shown that the quantity of drizzle is strongly linked to cloud morphology and tends to be associated with updrafts within the marine boundary layer. Increased amounts of drizzle tend to be found in marine clouds that form in clean air masses that have low concentrations of cloud droplets. This interconnection between clouds and drizzle can be explored using high-resolution numerical modelling such as large eddy simulation.

Influence of aerosols

It has been hypothesized by a group of atmospheric scientists at Texas A&M University [4] that particulates in the atmosphere caused by human activities may suppress drizzle. According to this hypothesis, because drizzle can be an effective means of removing moisture from a cloud, its suppression could help to increase the thickness, coverage, and longevity of marine stratocumulus clouds. This would lead to increased cloud albedo on a regional to global scale, and a cooling effect on the atmosphere. Estimates using complex global climate models suggest that this effect may be partially masking the effects of greenhouse gas increases on global surface temperature. However, it is not clear that the representation of the chemical and physical processes needed to accurately simulate the interaction between aerosols, clouds, and drizzle in our current climate models is sufficient to fully understand the global impacts of changes in particulates. [5]

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Cloud Visible mass of liquid droplets or frozen crystals suspended in the atmosphere

In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture from an adjacent source to raise the dew point to the ambient temperature. They are seen in the Earth's homosphere, which includes the troposphere, stratosphere, and mesosphere. Nephology is the science of clouds, which is undertaken in the cloud physics branch of meteorology. There are two methods of naming clouds in their respective layers of the homosphere, Latin and common.

Cumulus cloud Genus of clouds, low-level cloud

Cumulus clouds are clouds which have flat bases and are often described as "puffy", "cotton-like" or "fluffy" in appearance. Their name derives from the Latin cumulo-, meaning heap or pile. Cumulus clouds are low-level clouds, generally less than 2,000 m (6,600 ft) in altitude unless they are the more vertical cumulus congestus form. Cumulus clouds may appear by themselves, in lines, or in clusters.

Fog Atmospheric phenomenon

Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Fog can be considered a type of low-lying cloud usually resembling stratus, and is heavily influenced by nearby bodies of water, topography, and wind conditions. In turn, fog affects many human activities, such as shipping, travel, and warfare.

Stratus cloud

Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds that are formed by rising thermals. More specifically, the term stratus is used to describe flat, hazy, featureless clouds at low altitudes varying in color from dark gray to nearly white. The word stratus comes from the Latin prefix strato-, meaning "layer". Stratus clouds may produce a light drizzle or a small amount of snow. These clouds are essentially above-ground fog formed either through the lifting of morning fog or through cold air moving at low altitudes over a region. Some call these clouds "high fog" for their fog-like form. While light rain may fall, this cloud does not indicate much meteorological precipitation.

Freezing rain Rain maintained at temperatures below freezing

Freezing rain is rain maintained at temperatures below freezing by the ambient air mass that causes freezing on contact with surfaces. Unlike a mixture of rain and snow or ice pellets, freezing rain is made entirely of liquid droplets. The raindrops become supercooled while passing through a sub-freezing layer of air hundreds of meters above the ground, and then freeze upon impact with any surface they encounter, including the ground, trees, electrical wires, aircraft, and automobiles. The resulting ice, called glaze ice, can accumulate to a thickness of several centimeters and cover all exposed surfaces. The METAR code for freezing rain is FZRA.

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  1. National Weather Service Observing Handbook No. 8, Aviation Weather Observations for Supplementary Aviation Weather Reporting Stations (SAWRS), Manual Observations, October 1996
  2. Spence, Charles F. (2006). Aim/Far. McGraw Hill Professional. p. 294. ISBN   978-0-07-147924-0.
  3. Henson, Robert; Guides, Rough (2007). The Rough Guide to Weather. Penguin. p. 63. ISBN   978-1-4053-8461-2.
  4. "Can Aerosols Influence Weather Patterns?". Texas A&M Today. 2018-01-22. Retrieved 2019-05-24.
  5. "Are aerosols reducing coastal drizzle and increasing cloud cover?". Eurekalert.org. 2005-06-30. Retrieved 2013-08-25.