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Humidex Plot
The humidex (short for humidity index) is an index number used by Canada, Canadian meteorologists to describe how hot the weather feels to the average person, by combining the effect of heat and humidity. The term ''humidex'' was coined in 1965. The humidex is a nominally dimensionless quantity (though generally recognized by the public as equivalent to the Celsius scale, degree Celsius) based on the dew point. ''Range of humidex: Scale of comfort'': * 20 to 29: Little to no discomfort * 30 to 39: Some discomfort * 40 to 45: Great discomfort; avoid exertion * Above 45: Dangerous; heat stroke quite possible History The current formula for determining the humidex was developed by J. M. Masterton and F. A. Richardson of Canada's Atmospheric Environment Service in 1979. Humidex differs from the heat index used in the United States in being derived from the dew point rather than the relative humidity, though both dew point and relative humidity (when used in conjunction with air tem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Universal Gas Constant
The molar gas constant (also known as the gas constant, universal gas constant, or ideal gas constant) is denoted by the symbol or . It is the molar equivalent to the Boltzmann constant, expressed in units of energy per temperature, temperature increment per amount of substance, rather than energy per temperature increment per ''particle''. The constant is also a combination of the constants from Boyle's law, Charles's law, Avogadro's law, and Gay-Lussac's law. It is a physical constant that is featured in many fundamental equations in the physical sciences, such as the ideal gas law, the Arrhenius equation, and the Nernst equation. The gas constant is the constant of proportionality that relates the energy scale in physics to the temperature scale and the scale used for amount of substance. Thus, the value of the gas constant ultimately derives from historical decisions and accidents in the setting of units of energy, temperature and amount of substance. The Boltzmann constan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1979 Introductions
Events January * January 1 ** United Nations Secretary-General Kurt Waldheim heralds the start of the ''International Year of the Child''. Many musicians donate to the ''Music for UNICEF Concert'' fund, among them ABBA, who write the song ''Chiquitita'' to commemorate the event. ** In 1979, the United States officially severed diplomatic ties with the Republic of China (Taiwan). This decision marked a significant shift in U.S. foreign policy, turning to view the People's Republic of China as the sole legitimate representative of China. ** The United States and the People's Republic of China establish full Sino-American relations, diplomatic relations. ** Following a deal agreed during 1978, France, French carmaker Peugeot completes a takeover of American manufacturer Chrysler's Chrysler Europe, European operations, which are based in United Kingdom, Britain's former Rootes Group factories, as well as the former Simca factories in France. * January 6 – Geylang Bahru family ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Thermodynamics
Atmospheric thermodynamics is the study of heat-to-Work (physics), work transformations (and their reverse) that take place in the Earth's atmosphere and manifest as weather or climate. Atmospheric thermodynamics use the laws of classical thermodynamics, to describe and explain such phenomena as the properties of moist air, the formation of clouds, atmospheric convection, boundary layer meteorology, and vertical instabilities in the atmosphere. Atmospheric thermodynamic diagrams are used as tools in the forecasting of storm development. Atmospheric thermodynamics forms a basis for cloud microphysics and convection parametrization (climate), parameterizations used in numerical weather models and is used in many climate considerations, including convective-equilibrium climate models. Overview The atmosphere is an example of a non-equilibrium system. Atmospheric thermodynamics describes the effect of buoyant forces that cause the rise of less dense (warmer) air, the descent of more d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wind Chill
Wind chill (popularly wind chill factor) is the sensation of cold produced by the wind for a given ambient air temperature on exposed skin as the air motion accelerates the rate of heat transfer from the body to the surrounding atmosphere. Its values are always lower than the air temperature in the range where the formula is valid. When the apparent temperature is higher than the air temperature, the heat index is used instead. Explanation 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. As convection from a warm surface heats the air around it, an insulating boundary layer of warm air forms against the surface. Moving air disrupts this boundary layer, or epiclimate, carrying the warm air away, thereby allowing cooler air to replace the warm air against the surface and i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Comfort
Thermal comfort is the condition of mind that expresses subjective satisfaction with the thermal environment.ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupancy The human body can be viewed as a heat engine where food is the input energy. The human body will release excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to temperature difference. In cold environments, the body loses more heat to the environment and in hot environments the body does not release enough heat. Both the hot and cold scenarios lead to discomfort. Maintaining this standard of thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC ( heating, ventilation, and air conditioning) design engineers. Thermal neutrality is maintained when the heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equilibrium with the surroundings. The main factors that in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AccuWeather
AccuWeather, Inc. is a private-sector American media company that provides commercial weather forecasting services. AccuWeather was founded in 1962 by Joel N. Myers. The company adopted the name 'AccuWeather' in 1971. AccuWeather is headquartered in Ferguson Township, just outside of State College, Pennsylvania, with offices at 80 Pine Street in Manhattan's Financial District in addition to Wichita, Kansas, and Oklahoma City, Oklahoma. Internationally, AccuWeather has offices in Tokyo, Beijing, Seoul, and Mumbai. The business model of the company is to take statistics and weather data compiled by federal agencies and federal government satellites and sell it to users in a more user-friendly, consumable format. AccuWeather has lobbied the US government to stop providing services for free to the public and to privatize the National Weather Service, thus enabling AccuWeather to provide those services at a charge instead. Company profile AccuWeather provides weather fore ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Index
The heat index (HI) is an index that combines air temperature and relative humidity, in shade (shadow), shaded areas, to posit a human-perceived equivalent temperature, as how hot it would feel if the humidity were some other value in the Shade (shadow), shade. For example, when the temperature is with 70% relative humidity, the heat index is (see table below). The heat index is meant to describe experienced temperatures in the shade, but it does not take into account heating from direct sunlight, physical activity or cooling from wind. The human body normally cools itself by evaporation of perspiration, sweat. High relative humidity reduces evaporation and cooling, increasing discomfort and potential Hyperthermia, heat stress. Different individuals perceive heat differently due to body shape, metabolism, level of hydration, pregnancy, or other physical conditions. Measurement of perceived temperature has been based on reports of how hot subjects feel under controlled conditions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metrication In Canada
Metrication in Canada began in 1970 and ceased in 1985. While Canada has converted to the metric system for many purposes, there is still significant use of non-metric units and standards in many sectors of the Canadian economy and everyday life. This is mainly due to historical ties with the United Kingdom, the traditional use of the imperial system of measurement in Canada, interdependent supply chains with the United States, and opposition to metrication during the transition period. Before conversion Until the 1970s, Canada traditionally used the imperial measurement system, labelled as "Canadian units of measurement" under Schedule II of the '' Weights and Measures Act'' (R.S., 1985, c. W-6). These units have the same names and the same values as United States customary units, with the exception of capacity measures such as the gallon. For example, before metrication in Canada, gasoline was sold by the (imperial) gallon (about 4.55 litres). In cross-border transactions with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fahrenheit Scale
The Fahrenheit scale () is a temperature scale based on one proposed in 1724 by the German-Polish physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. Several accounts of how he originally defined his scale exist, but the original paper suggests the lower defining point, 0 °F, was established as the freezing temperature of a solution of brine made from a mixture of water, ice, and ammonium chloride (a salt). The other limit established was his best estimate of the average human body temperature, originally set at 90 °F, then 96 °F (about 2.6 °F less than the modern value due to a later redefinition of the scale). For much of the 20th century, the Fahrenheit scale was defined by two fixed points with a 180 °F separation: the temperature at which pure water freezes was defined as 32 °F and the boiling point of water was defined to be 212 °F, both at sea level and under standard at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vapour Pressure Of Water
The vapor pressure of water is the pressure exerted by molecules of water vapor in gaseous form (whether pure or in a mixture with other gases such as air). The saturation vapor pressure is the pressure at which water vapor is in thermodynamic equilibrium with its condensed state. At pressures higher than saturation vapor pressure, water will condense, while at lower pressures it will evaporate or sublimate. The saturation vapor pressure of water increases with increasing temperature and can be determined with the Clausius–Clapeyron relation. The boiling point of water is the temperature at which the saturated vapor pressure equals the ambient pressure. Water supercooled below its normal freezing point has a higher vapor pressure than that of ice at the same temperature and is, thus, unstable. Calculations of the (saturation) vapor pressure of water are commonly used in meteorology. The temperature-vapor pressure relation inversely describes the relation between the boilin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enthalpy Of Vaporization
In thermodynamics, the enthalpy of vaporization (symbol ), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas. The enthalpy of vaporization is a function of the pressure and temperature at which the transformation (vaporization or evaporation) takes place. The enthalpy of vaporization is often quoted for the normal boiling temperature of the substance. Although tabulated values are usually corrected to 298 K, that correction is often smaller than the uncertainty in the measured value. The heat of vaporization is temperature-dependent, though a constant heat of vaporization can be assumed for small temperature ranges and for reduced temperature . The heat of vaporization diminishes with increasing temperature and it vanishes completely at a certain point called the critical temperature (). Above the critical temperature, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
