: Anton Parshin
: 30.27 MB
Clouds are one of the most important atmospheric phenomena, which are observed at hydrometeorological stations. Clouds are systems of cloud elements, suspended in the atmosphere (products of water vapor condensation), and when they condense, precipitation occurs (rain, snow or sometimes hail). The cloud cover affects air temperature and diurnal temperature range, and therefore other meteorological phenomena, by reducing influx of solar heat and light in the daytime, and dramatically attenuating ground radiation and cooling the Earth's surface at night.
Clouds (cloud amount), especially dense and thick, can greatly complicate aviation operations. When cloud cover is low it’s more difficult for a plane to takeoff or to land. In liquid-phase supercooled clouds an aircraft is being covered with wet growth ice, which is very dangerous. Also there are threads such as lightning and sudden change of ascending and descending air currents.
The formation of various forms of cloud characterizes many atmospheric processes, typical for the area. The results of observations of cloud amount, received at the meteorological stations, are essential for synoptic weather analysis and forecasting, as they are included in the synoptic telegrams sent to the Weather Bureau and HydroMetCenter of the Russian Federation, and are used to study climate. Therefore, observers should carefully define the following cloud data:
1) total number of clouds and low clouds,
2) shape of the clouds,
3) cloud base height of medium and low clouds
Determining the amount and form of the clouds is produced visually without instruments. The accuracy of observations, and consequently, their value, depends on the observer’s competence and systematic observations of the state of the sky and its changes over time.
Visual observations help to determine not only the number and form of the cloud, but also to make some conclusions about their microstructure (e.g., the presence of ice particles in them).
Pictures of clouds, taken from meteorological satellites, have confirmed previous findings that the clouds do form large-scale cloud systems (macrosystems) and medium systems (mesosystems), which determine the weather patterns in the area. In this regard, in Chapter 2 (2.2) a brief description of the macro- and meso-scale cloud system is given, and in addition to the description of the cloud fronts systems there is some information about the possible deviations in their formation.
Information about the cloud systems, especially mesosystems related with fronts, is reported for the first time. It will be useful in solving such problems as the alignment of surface and satellite observations, the method development of mesoscale synoptic processes’ analysis and etc, the problems, which have arisen with the advent of weather satellites.
It is important for the observer to understand the essence of the most important atmospheric processes leading to the formation of various clouds forms. This understanding identifies competence of the observer. It helps him to make correct observations in the more difficult cases, when the clouds are slightly different from the images in the Atlas, and refers to transitional forms. Origin of transitional forms is described in Chapter 2 (2.3).
Description of clouds as a local weather feature is made with consideration of the scale of the cloud systems, which include expected effects. This allows observers to understand better the difference between processes and cloud systems of different scales.
Chapter 3 includes a new concept of territorial characteristics of the clouds, which allows concluding that the specific forms of clouds are closely connected with some large areas, which are characterized not only by the latitudinal zones, but also by relatively homogeneous thermal and dynamic conditions.