Mercury-in-glass thermometerThe mercury-in-glass or mercury thermometer was invented by physicist Daniel Gabriel Fahrenheit in Amsterdam (1714). It consists of a bulb containing mercury attached to a glass tube of narrow diameter; the volume of mercury in the tube is much less than the volume in the bulb. The volume of mercury changes slightly with temperature; the small change in volume drives the narrow mercury column a relatively long way up the tube. The space above the mercury may be filled with nitrogen gas or it may be at less than atmospheric pressure, a partial vacuum.
PyranometerA pyranometer () is a type of actinometer used for measuring solar irradiance on a planar surface and it is designed to measure the solar radiation flux density (W/m2) from the hemisphere above within a wavelength range 0.3 μm to 3 μm. A typical pyranometer does not require any power to operate. However, recent technical development includes use of electronics in pyranometers, which do require (low) external power (see heat flux sensor). The solar radiation spectrum that reaches earth's surface extends its wavelength approximately from 300 nm to 2800 nm.
22° haloA 22° halo is an atmospheric optical phenomenon that consists of a halo with an apparent radius of approximately 22° around the Sun or Moon. When visible around the Moon, it is also known as a moon ring, storm ring, or winter halo. It forms as sunlight or moonlight is refracted by millions of hexagonal ice crystals suspended in the atmosphere. Its radius is roughly the length of an outstretched hand at arm's length. Even though it is one of the most common types of halo, the exact shape and orientation of the ice crystals responsible for the 22° halo are the topic of debate.
Norwegian cyclone modelThe older of the models of extratropical cyclone development is known as the Norwegian cyclone model, developed during and shortly after World War I within the Bergen School of Meteorology. In this theory, cyclones develop as they move up and along a frontal boundary, eventually occluding and reaching a barotropically cold environment. It was developed completely from surface-based weather observations, including descriptions of clouds found near frontal boundaries.
Wind chillWind chill or windchill (popularly wind chill factor) is the lowering of body temperature due to the passing flow of lower-temperature air. Wind chill numbers are always lower than the air temperature for values where the formula is valid. When the apparent temperature is higher than the air temperature, the heat index is used instead. A surface loses heat through conduction, evaporation, convection, and radiation. The rate of convection depends on both the difference in temperature between the surface and the fluid surrounding it and the velocity of that fluid with respect to the surface.
TeleconnectionTeleconnection in atmospheric science refers to climate anomalies being related to each other at large distances (typically thousands of kilometers). The most emblematic teleconnection is that linking sea-level pressure at Tahiti and Darwin, Australia, which defines the Southern Oscillation. Another well-known teleconnection links the sea-level pressure over Iceland with the one over the Azores, traditionally defining the North Atlantic Oscillation (NAO).
Aerography (meteorology)Aerography is the production of weather charts. The information is supplied by radiosonde observations, principally. Constant-pressure charts are routinely constructed at standard air pressures. Standard air pressures are 850, 700, 500, 400, 300, 250, and 200 millibars (hectopascals) (hPa) (SI). Weather charts are sometimes drawn at lower air pressures that occur above 40,000 feet (12 km). The lines of equal air pressure are called isobars. Isotherms are the lines of equal air temperature.
Corona (optical phenomenon)In meteorology, a corona (plural coronae) is an optical phenomenon produced by the diffraction of sunlight or moonlight (or, occasionally, bright starlight or planetlight) by individual small water droplets and sometimes tiny ice crystals of a cloud or on a foggy glass surface. In its full form, a corona consists of several concentric, pastel-colored rings around the celestial object and a central bright area called aureole.
Stream functionThe stream function is defined for incompressible (divergence-free) flows in two dimensions – as well as in three dimensions with axisymmetry. The flow velocity components can be expressed as the derivatives of the scalar stream function. The stream function can be used to plot streamlines, which represent the trajectories of particles in a steady flow. The two-dimensional Lagrange stream function was introduced by Joseph Louis Lagrange in 1781. The Stokes stream function is for axisymmetrical three-dimensional flow, and is named after George Gabriel Stokes.
Snow gaugeA snow gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of solid precipitation (as opposed to liquid precipitation, which is measured by a rain gauge) over a set period of time. The first use of snow gauges were precipitation gauges that was widely used in 1247 during the Southern Song dynasty to gather meteorological data. The Song Chinese mathematician and inventor Qin Jiushao records the use of gathering rain and snowfall measurements in the Song mathematical treatise Mathematical Treatise in Nine Sections.
