The shape or texture of clouds are stratus (sheets or layers) and cumulus (heap). Cirrostratus are transparent, whitish clouds with a hair-like appearance covering nearly the entire sky like the veil. Cloud Formation Cards. Cirrus may also appear at and around thunderstorms as upper level winds blow ice crystals off the top of these towering cumulonimbus clouds. This is because while cirrus and cirrostratus clouds usually contain small, hexagonal ‘prism’ crystals such as thick plates, short solid columns – simple crystals that refract the sun’s light as it passes through them, deeper altostratus clouds generally have larger more complicated crystals and snowflakes that do not permit simple refraction even when the sun’s position is plainly evident. Nimbostratus clouds (Figure 6) are virtually identical to altostratus clouds in their composition except that their ‘bases’ are usually perceived from the ground as lower than in altostratus, from which it has usually derived by a downward thickening. Middle clouds, 7 to 2 km (23,000 to 6,500 feet), are altocumulus and altostratus. During the daytime clouds can be detected in both wavelength regions, but at night only in the thermal infrared. Photo by Carolyn Green in Ohio, 2000. Cirrus (Figures 1 and 2) and cirrostratus (Figure 3) clouds are composed of ice crystals with, perhaps, a few momentary exceptions at formation when the temperature is higher than −40 °C. How do altostratus clouds form? Cirrus clouds do not usually produce full haloes due to their patchy nature. On an annual average, clouds cover between 55% and 60% of the earth (Matveev, 1984), and much of this cloud cover consists of vast sheets of middle (altostratus and altocumulus) and high (cirrus, cirrostratus, and cirrocumulus) clouds. A broken-to-overcast layer of shallow stratus or stratocumulus clouds often resides at the bottom of nimbostratus clouds. An interesting and very graphic formation of cirrostratus clouds in a very blue sky. The largest of the visible cloud elements in cirrocumulus can be no larger than the width of a finger held skyward when observed from the ground; if larger, the cloud is classified as an altocumulus. Pilots use the cirrus clouds developed by jet streaks as warning signs of turbulence. Clouds with bases 2–6 km above the surface are termed ‘middle’ clouds, and are classified as altostratus (As) or altocumulus (Ac) by their resemblance to St or Cu. Optical phenomena associated with altostratus clouds are limited to parhelia (‘sun dogs’). See more ideas about cirrostratus clouds, clouds, optical phenomena. Clouds with bases between 6 km and the tropopause are the ‘high’ clouds: cirrus (Ci), cirrostratus (Cs), and cirrocumulus (Cc). Cirrostratus clouds belong to the High Cloud (5000-13000m) group. National Weather Service: Ten Basic Clouds, National Center for Atmospheric Research: Clouds and How They Form, The Weather Prediction: A Ring Around the Sun or Moon, National Weather Service: The Science Corner-Cloud Classifications and Characteristics, National Weather Service: The 300/200 mb Chart. Cirrostratus Clouds (“Delicate cloud streaks”) Fast Facts: Typical Altitude: 20,000-42,000 ft. What kind of weather they are associated with: A change in weather can be expected soon. The Sun often cannot cast shadows when shining through altostratus clouds. Apr 2, 2019 - A collection of cirrostratus clouds -- described as thin, transparent, high-altitude cloud layer capable of producing a 22° halo. The latest studies on cold fog (Velde et al., 2010; Gultepe et al., 2007a, 2007b) stated that accurate fog prediction critically depends on model horizontal and vertical resolutions, initial conditions, microphysical parameterizations, PBL turbulence, radiation, land–surface interactions, and air quality (Bergot et al., 2007; Bergot and Guedalia, 1994). As the warmer air rises, however, the air cools and the water vapor begins to condense, forming cloud masses including cumulus, or puffy cottonball-type clouds, and stratus, or sheet-like clouds. The light refracts off the ice crystals in the cirrostratus cloud, creating the effect of a ring. Cultura RM/Janeycakes Photos/Getty Images. Although IN composition and concentration play an important role for ice initiation (Zelenyuk et al., 2005), the IN concentration cannot be predicted or measured accurately (Gultepe and Isaac, 2002; Gultepe et al., 2014). Cb are associated with thunder, lightning, and showery rain or snow. Altocumulus clouds with virga are predominantly those clouds whose temperatures are lower than −10°C. The higher the warm air flows, the more likely that cirrus clouds will form. Cumulonimbus clouds (see below) may also be embedded in nimbostratus clouds. Cloud optical thickness (opacity) is inferred from reflectance in the visible channel. Cirrostratus (Cs) Cirrostratus are transparent, whitish clouds with a hair-like appearance covering nearly the entire sky like the veil. Altostratus clouds are rarely less than 2 km thick and often have tops at the same heights as cirrus and cirrostratus clouds. Sunset Sunrise Clouds. Low-pressure systems are commonly preceded by high, thin clouds such as cirrostratus. Instability of this sort has been viewed as a marker for releases of deeper convection in the hours ahead. The halo is formed by the refraction of the light on the ice crystals in the clouds, similarly to how sundogs form but in an entire circle rather than just on either side of … Low clouds, with bases in the atmospheric boundary layer less than 2 km above the surface, are influenced by their proximity to the surface. Many airborne sensors cannot measure accurately the ice particles with sizes less than 200 μm because of issues of shattering on the sensor tips and sensor optical sensitivity in the high speed environments (Gultepe et al., 2001; Lawson, 2011; Lawson et al., 2006a, 2006b; Field et al., 2006). Cirrus clouds form the so-called mares' tails clouds high in the atmosphere. The coldest cirriform cloud tops (i.e., cirrus and cirrostratus) can be −80 °C or lower in deep storms with high cloud tops such as in anvils associated with exceptional thunderstorms. Gotaas and Benson (1965) studied two extreme ice fog events and suggested that cooling near the surface is not completely attributed to cold air advection or heat losses from the air and snow surface.
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