- 行业: Weather
- Number of terms: 60695
- Number of blossaries: 0
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The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
An instrument for collecting liquid water from the atmosphere. The collecting head is fabricated of a porous material having a pore size of the order of 30 μm. The pressure difference across the water–air interface prevents air from entering the capillary system while allowing free flow of water.
Industry:Weather
An index calculated from air temperature to estimate fulfillment of plant dormancy requirements and the ability to start springtime growth, especially tree fruits. Chill units are calculated in hourly time steps and summed over a time period. Cold temperatures add to chill units as the index ranges from 0 at temperatures less than 1°C, to 1 near 7°C, and 0 at 14°C. Temperatures above 14°C reduce chill unit accumulation as the index falls to -1 at 21°C. A minimum total number of chill units dependent upon species and variety must be exceeded before normal springtime growth can begin. Chill hour calculations frequently require hourly data from late evening to early morning.
Industry:Weather
An index developed by Palmer (1968) to assess short-term crop water conditions and needs across major crop-producing regions. It is based on the concept of abnormal evapotranspiration deficit, calculated as the difference between computed actual evapotranspiration (ET) and computed potential evapotranspiration (i.e., expected or appropriate ET). Actual evapotranspiration is based on the temperature and precipitation that occurs during the week and computed soil moisture in both the topsoil and subsoil layers.
Industry:Weather
An idealized reversible work cycle defined for any system, but usually limited, in meteorology, to a so-called perfect gas. The Carnot cycle consists of four states: 1) an isothermal expansion of the gas at a temperature T1; 2) an adiabatic expansion to temperature T2; 3) an isothermal compression at temperature T2; and 4) an adiabatic compression to the original state of the gas to complete the cycle. In a Carnot cycle, the net work done is the difference between the heat input Q1 at higher temperature T1 and the heat extracted Q2 at the lower temperature T2. The atmospheric general circulation and some storms, notably hurricanes, incorporate a process similar to a Carnot cycle. See Carnot engine, thermodynamic efficiency.
Industry:Weather
An idealized reversible heat engine working in a Carnot cycle. It is the most efficient engine that can operate between two specified temperatures; its efficiency is equivalent to the thermodynamic efficiency. The Carnot engine is capable of being run either as a conventional engine or as a refrigerator. See reversible process.
Industry:Weather
An ice crystal in the form of a hollow hexagonal cup. Usually one side is not developed and appears to be rolled up. Cup crystals are the most common form of depth hoar, but are rarely observed in snow.
Industry:Weather
An empirical expression for aerodynamic roughness length z0 = αcu*2/g over the ocean, where u* is the friction velocity, g is gravitational acceleration, and αc ≈ 0. 015 is the Charnock parameter. It accounts for increased roughness as wave heights grow due to increasing surface stress.
Industry:Weather
An electrometer for measuring small electric potential difference based upon change of surface tension between mercury and an electrolytic solution in a capillary tube with change of potential difference between the liquids.
Industry:Weather
An east or southeast desert wind in Morocco (North Africa), especially in the north. It is persistent, very dry and dusty, hot in summer, cold in winter. It blows with high pressure in the Mediterranean and isobars run nearly parallel with the coast. It is said to be most frequent in the 40 days following 11 or 12 July, a period known as the Smaïm. Compare simoom.
Industry:Weather
An electrical hygrometer element constructed of a plastic or glass strip coated with a film of carbon black dispersed in a hygroscopic binder. Changes in the ambient relative humidity lead to dimensional changes in the hygroscopic film such that the resistance increases proportionally with humidity. The successful implementation of this sensor type requires a well-controlled manufacturing process and very careful handling. The sensor is used in some radiosondes and named carbon hygristor.
Industry:Weather
