In meteorology, a cloud is a visible mass of liquid droplets or frozen crystals made of water or various chemicals suspended in the atmosphere above the surface of a planetary body. These suspended particles are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology. Two processes, possibly acting together, can lead to air becoming saturated; cooling the air or adding water vapor to the air. In general, precipitation will fall to the surface; an exception is virga, which evaporates before reaching the surface.
The international cloud classification system is based on the fact clouds can show free-convective upward growth like cumulus, appear in non-convective layered sheets such as stratus, or take the form of thin fibrous wisps, as in the case of cirrus. Prefixes are used in connection with clouds: strato- for low clouds with limited convection that form mostly in layers, nimbo- for thick layered clouds that can produce moderate to heavy precipitation, alto- for middle clouds, and cirro- for high clouds. Whether or not a cloud is low, middle, or high level depends on how far above the ground its base forms. Cloud types with significant vertical extent can form in the low or middle altitude ranges depending on the moisture content of the air. Clouds in the troposphere have Latin names due to the popular adaptation of Luke Howard's cloud categorization system, which began to spread in popularity during December 1802. Synoptic surface weather observations use code numbers to record and report the types of tropospheric cloud visible at each scheduled observation time based on the height and physical appearance of the clouds.
The Pampas (from Quechua pampa, meaning "plain") are fertile South American lowlands, covering more than 750,000 km2 (289,577 sq mi), that include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos and Córdoba, Chubut, most of Uruguay, and the southernmost Brazilian State, Rio Grande do Sul. These vast plains are a natural region only interrupted by the low Ventana and Tandil hills near Bahía Blanca and Tandil (Argentina), with a height of 1,300 m (4,265 ft) and 500 m (1,640 ft) respectively.
The climate is mild, with precipitation of 600 mm (23.6 in) to 1,200 mm (47.2 in), more or less evenly distributed through the year, making the soils appropriate for agriculture. This area is also one of the distinct physiography provinces of the larger Paraná-Paraguay Plain division. These plains contain unique wildlife because of the different terrains around it. Some of this wildlife includes the rhea, the pampas deer, several species of armadillos, the pampas fox, the White-eared opossum, the Elegant Crested Tinamou, and several other species.