1/6/2024 0 Comments Precipitate delivery positionAs heated surface air becomes buoyant, it is forced aloft and cools. Local heating will result in thermal lifting. This may occur by evaporation as cold, dry air passes over warm water, or as warm rain from above a front foils through cold air beneath the front. Contrails made by high-flying aircraft are a type of cloud formed by the addition of moisture from the plane’s exhaust.Īir can become saturated by the addition of moisture. Rain falling from the warm clouds above the front evaporates in the cold air beneath and forms scud clouds. Saturation may also be reached when warm rain falls through cold air for example, beneath a warm front. Cold continental polar air crossing the warmer Great Lakes in the fall and early winter gathers large amounts of moisture and produces cloudiness and frequently causes rain or snow to the lee of the lakes. These are through the addition of moisture to the air, or, more importantly, through the lowering of air temperature.Īs cold air passes over warm water, rapid evaporation takes place, and saturation is quickly reached. There are two principal ways in which the atmospheric vapor pressure and saturation vapor pressure attain the same value to produce 100 percent relative humidity, or saturation. In chapter 3 we learned that at saturation the atmospheric vapor pressure is equal to the saturation vapor pressure at the existing temperature and pressure. In order for clouds to form and precipitation to develop, the atmosphere must be saturated with moisture. It becomes obvious that tremendous quantities of water and energy are involved in the formation of clouds and precipitation. For each ton of water that condenses, almost 2 million B.t.u.’s of latent heat is released to the atmosphere. All of this water comes from condensation of vapor in the atmosphere. Over an area the size of Oregon, 1 inch of rain is equivalent to nearly 8 billion tons of water. One inch of rainfall over an acre weighs about 113 tons. It has been estimated that the amount carried across the land by air currents is more than six times the amount of water carried by all our rivers. The total amount of water vapor in the atmosphere is very large. We will see how clouds are classified and named, and what kinds of precipitation certain types of clouds produce. We must look into the processes by which clouds are formed and precipitation is produced in order to understand the meaning and portent of clouds as they relate to fire weather. Some produce precipitation and become an ally to the firefighter. Those that indicate instability may serve as a warning to the fire-control man. Clouds are visible evidence of atmospheric moisture and atmospheric motion. But we need to look beyond these aesthetic qualities. Some clouds are pretty, others are dull, and some are foreboding. The total amount of water vapor that flows across the land on air currents originating over water is estimated to be more than six times the water carried by all our rivers.Ĭlouds consist of minute water droplets, ice crystals, or a mixture of the two in sufficient quantities to make the mass discernible.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |