The World Meteorological Organization (WMO) is a specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics.
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature 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.
A weather balloon, also known as a sounding balloon, is a balloon that carries instruments to the stratosphere to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde. To obtain wind data, they can be tracked by radar, radio direction finding, or navigation systems. Balloons meant to stay at a constant altitude for long periods of time are known as transosondes. Weather balloons that do not carry an instrument pack are used to determine upper-level winds and the height of cloud layers. For such balloons, a theodolite or total station is used to track the balloon's azimuth and elevation, which are then converted to estimated wind speed and direction and/or cloud height, as applicable.
Cirrostratus is a high-altitude, very thin, generally uniform stratiform genus-type of cloud. It is made out of ice-crystals, which are pieces of frozen water. It is difficult to detect and it can make halos. These are made when the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no halos if it is thicker cirrostratus fibratus. On the approach of a frontal system, the cirrostratus often begins as nebulous and turns to fibratus. If the cirrostratus begins as fragmented of clouds in the sky it often means the front is weak. Cirrostratus is usually located above 5.5 km (18,000 ft). Its presence indicates a large amount of moisture in the upper troposphere. Clouds resembling cirrostratus occasionally form in polar regions of the lower stratosphere. Polar stratospheric clouds can take on this appearance when composed of tiny supercooled droplets of water or nitric acid.
Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds formed by rising thermals. The term stratus describes 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. Some call these clouds "high fog" for their fog-like form.
The timeline of meteorology contains events of scientific and technological advancements in the area of atmospheric sciences. The most notable advancements in observational meteorology, weather forecasting, climatology, atmospheric chemistry, and atmospheric physics are listed chronologically. Some historical weather events are included that mark time periods where advancements were made, or even that sparked policy change.
Mammatus is a cellular pattern of pouches hanging underneath the base of a cloud, typically a cumulonimbus raincloud, although they may be attached to other classes of parent clouds. The name mammatus is derived from the Latin mamma.
The International Meteorological Organization was the first organization formed with the purpose of exchanging weather information among the countries of the world. It came into existence from the realization that weather systems move across country boundaries; and that knowledge of pressure, temperature, precipitations, etc., upstream and downstream are needed for weather forecasting. It was superseded by the World Meteorological Organization.
Léon Philippe Teisserenc de Bort was a French meteorologist and a pioneer in the field of aerology. Together with Richard Assmann (1845-1918), he is credited as co-discoverer of the stratosphere, as both men announced their discovery during the same time period in 1902. Teisserenc de Bort pioneered the use of unmanned instrumented balloons and was the first to identify the region in the atmosphere around 8-17 kilometers of height where the lapse rate reaches zero, known today as the tropopause.
Wladimir Petrovich Köppen was a Russian–German geographer, meteorologist, climatologist and botanist. After studies in St. Petersburg, he spent the bulk of his life and professional career in Germany and Austria. His most notable contribution to science was the development of the Köppen climate classification system, which, with some modifications, is still commonly used. Köppen made significant contributions to several branches of science, and coined the name aerology for the science of measuring the upper air/atmosphere.
A flammagenitus cloud, also known as a flammagenitus, pyrocumulus cloud, or fire cloud, is a dense cumuliform cloud associated with fire or volcanic eruptions. A flammagenitus is similar dynamically in some ways to a firestorm, and the two phenomena may occur in conjunction with each other. However, either may occur without the other.
Luke Howard, was a British manufacturing chemist and an amateur meteorologist with broad interests in science. His lasting contribution to science is a nomenclature system for clouds, which he proposed in an 1802 presentation to the Askesian Society. Because of this, Howard is referred to as "The Godfather of Clouds", the "namer of the clouds", and the "father of meteorology".
Ferdinand Jules Quénisset (1872–1951) was a French astronomer who specialized in astrophotography.
The climate in Greece is predominantly Mediterranean. However, due to the country's geography, Greece has a wide range of micro-climates and local variations. The Greek mainland is extremely mountainous, making Greece one of the most mountainous countries in Europe. To the west of the Pindus mountain range, the climate is generally wetter and has some maritime features. The east of the Pindus mountain range is generally drier and windier in summer. The highest peak is Mount Olympus, 2,918 metres (9,573 ft). The northern areas of Greece have a transitional climate between the continental, the Mediterranean and the humid subtropical climate. There are mountainous areas that have an alpine climate. Also, various areas of Greece have semi-arid climates.
Asperitas is a cloud formation first popularized and proposed as a type of cloud in 2009 by Gavin Pretor-Pinney of the Cloud Appreciation Society. Added to the International Cloud Atlas as a supplementary feature in March 2017, it is the first cloud formation added since cirrus intortus in 1951. The name translates approximately as "roughness".
A cloud atlas is a pictorial key to the nomenclature of clouds. Early cloud atlases were an important element in the training of meteorologists and in weather forecasting, and the author of a 1923 atlas stated that "increasing use of the air as a means of transportation will require and lead to a detailed knowledge of all the secrets of cloud building."
Albert Riggenbach, also known as Albert Riggenbach-Burckhardt, was a Swiss meteorologist and co-author, with Hugo Hildebrandsson and Léon Teisserenc de Bort, of one of the first cloud atlases, the International Cloud Atlas in 1896. His doctoral dissertation (Habilitationsschrift) concerned observations of the first described Bishop's Ring.
Hugo Hildebrand Hildebrandsson was a Swedish meteorologist and professor at Uppsala university between 1878 and 1907.
A homogenitus, anthropogenic or artificial cloud is a cloud induced by human activity. Although most clouds covering the sky have a purely natural origin, since the beginning of the Industrial Revolution, the use of fossil fuels and water vapor and other gases emitted by nuclear, thermal and geothermal power plants yield significant alterations of the local weather conditions. These new atmospheric conditions can thus enhance cloud formation.
