- Industry: Weather
- Number of terms: 60695
- Number of blossaries: 0
- Company Profile:
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, ...
A method for monitoring the soil water budget for relatively large areas based on the pioneering work of C. W. Thornthwaite (1948) using the concept of potential evapotranspiration. The Palmer Drought Severity Index and the companion “crop moisture index,” developed by W. C. Palmer, are modifications of the earlier Thornthwaite work.
Industry:Weather
A method of assigning areal significance to point rainfall values. Perpendicular bisectors are constructed to the lines joining each measuring station with those immediately surrounding it. These bisectors form a series of polygons, each polygon containing one station. The value of precipitation measured at a station is assigned to the whole area covered by the enclosing polygon.
Industry:Weather
A measure of turbidity, related to aerosol optical depth, as in the Ängström turbidity coefficient, Linke turbidity factor, or Volz turbidity factor.
Industry:Weather
A mechanism for electric charge separation during freezing of slightly impure water, discovered by Workman and Reynolds (1950). When a very dilute solution of certain salts freezes rapidly, a strong potential difference is established between the solid and liquid phases. For some salts, the ice attains negative charge, for others, positive. This mechanism was thought to play a role in the charging of thunderstorms. It is now known that it cannot account for the electrification of riming graupel by the shedding of charged surface water because the droplets freeze faster than the time taken for a substantial ice– water freezing potential to occur. This mechanism has been suggested as one possible mode of thunderstorm charge separation in those portions of a thunderstorm downdraft where snow pellets or hail particles sweep out supercooled water drops. Partial freezing and partial blow-off of a liquid film could lead to charge separation. The acknowledged predominance of dry growth of graupel in New Mexico thunderclouds led Reynolds (1953) to question the viability of this mechanism in the atmosphere. This should not be confused with the Reynolds effect.
Industry:Weather
A member of a family of functions generated by taking translations (e.g., ''w''(''t'') → ''w''(''t'' + 1)) and scalings (e.g., ''w''(''t'') →'' w''(2''t'')) of a function ''w''(''t''), called the “mother” wavelet. The choice of ''w''(''t'') is limited by the condition that the square of ''w''(''t'') be integrable over all ''t''. Linear combinations of wavelets are used to represent wavelike signals. The wavelet decomposition of a signal offers an advantage over the Fourier decomposition in that local or short-term contributions to the signal can be better represented.
Industry:Weather
A measure of the time the wind has been acting on a wave group, either because the wind has been blowing for a finite length of time or because the fetch is limited; usually expressed as a dimensionless number, the phase speed of the peak of the wave spectrum divided by the wind speed or by the friction velocity.
Industry:Weather
A measure of the turbidity of the atmosphere. The Volz turbidity factor is equal to the aerosol optical depth at a wavelength of 0. 5 μm.
Industry:Weather
A measure of the strength of the westerly surface wind between 35° and 55°N. The index is computed from the average sea level pressure difference between these latitudes and is expressed as the west to east component of geostrophic wind to a tenth of a meter per second. Compare zonal index, polar-easterlies index, subtropical-easterlies index.
Industry:Weather
A measure of the scattering coefficient, with units of inverse length.
Industry:Weather
A measure of the depletion of monochromatic radiance passing through some medium in a constant direction. The volume extinction coefficient equals the fractional depletion due to absorption and scattering when monochromatic radiance passes unit distance through a medium in a constant direction. Units are inverse length or km<sup>−1</sup>. Values depend critically on the medium being traversed, as well as the wavelength. For example, in a Rayleigh atmosphere the volume extinction coefficient at a wavelength of 0. 5 μm is less than 0. 02 km<sup>−1</sup>, whereas in a wet cloud it may exceed 100 km<sup>−1</sup> at the same wavelength.
Industry:Weather
