Drizzle is a light precipitation which consists of liquid water drops that are smaller than those of rain – generally smaller than 0.5 mm (0.02 in) in diameter. 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 .
10-449: 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. These drops immediately freeze upon impact, leading to the buildup of sheet ice (sometimes called black ice ) on the surface of roads. Drizzle tends to be the most frequent form of precipitation over large areas of
20-416: A group of atmospheric scientists at Texas A&M University 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
30-451: 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 current (as of 2005) climate models
40-470: A subfreezing environment, the liquid water will not freeze if the environmental temperature is above 18 °F (−8 °C), via supercooling . If ice crystals are already present in this environment, the liquid droplets will freeze onto these crystals and be effectively removed before they can grow large enough to fall out of the cloud. As a result, freezing drizzle develops in shallow low-level stratus-type clouds where air saturation occurs entirely below
50-482: Is extremely dangerous to aircraft in icing conditions , as the supercooled water droplets will freeze onto the airframe, degrading aircraft performance considerably. The loss and accident of American Eagle Flight 4184 on October 31, 1994, has been attributed to ice buildup due to freezing drizzle aloft. This meteorology –related article is a stub . You can help Misplaced Pages by expanding it . Icing conditions Too Many Requests If you report this error to
60-416: Is sufficient to fully understand the global impacts of changes in particulates. Freezing drizzle Freezing drizzle is drizzle that freezes on contact with the ground or an object at or near the surface. Its METAR code is FZDZ . Although freezing drizzle and freezing rain are similar in that they both involve liquid precipitation above the surface in subfreezing temperatures and freeze on
70-471: The layer in which ice crystals can develop and grow. When freezing drizzle accumulates on land, it creates an icy layer of glaze . Freezing drizzle alone does not generally result in significant ice accumulations due to its light, low-intensity nature unlike its rain counterpart. However, even thin layers of slick ice deposited on roads as black ice can be very slippery and cause extremely hazardous conditions resulting in vehicle crashes. Freezing drizzle
80-447: 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 . It has been hypothesized by
90-403: The surface, the mechanisms leading to their development are entirely different. Where freezing rain forms when frozen precipitation falls through a melting layer and turns liquid, freezing drizzle forms via the supercooled warm-rain process , in which cloud droplets coalesce until they become heavy enough to fall out of the cloud, but in subfreezing conditions. Despite this process taking place in
100-594: 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 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 which can detect drizzle. These studies have shown that
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