Search results
Results from the WOW.Com Content Network
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa ), which is equivalent to 1,013.25 millibars , [ 1 ] 760 mm Hg , 29.9212 inches Hg , or 14.696 psi . [ 2 ]
For example, if a barometer located at sea level and under fair weather conditions is moved to an altitude of 1,000 feet (305 m), about 1 inch of mercury (~35 hPa) must be added on to the reading. The barometer readings at the two locations should be the same if there are negligible changes in time, horizontal distance, and temperature.
Calls for the creation of a government weather bureau began as early as 1844, when the electrical telegraph was introduced. In 1869, Cleveland Abbe, then director of the Cincinnati Observatory, began developing and issuing public weather forecasts (which he called "probabilities") using daily weather observations collected simultaneously and sent via telegraph by a network of observers.
(A reading of 922.5 mbar (corrected to MSL) was reported from Omagh in Co. Tyrone (Harding 1887) the graduation and calibration of the barometer were not considered satisfactory enough “to quote the reading as trustworthy”, the storm minimum over the Northern Ireland was thought to be close to 924 mbar.)
Christopher C. Burt, a weather historian writing for Weather Underground, believes that the 1913 Death Valley reading is "a myth", and is at least 2.2 or 2.8 °C (4 or 5 °F) too high. [13] Burt proposes that the highest reliably recorded temperature on Earth could still be at Death Valley, but is instead 54.0 °C (129.2 °F) recorded on 30 ...
In February 1755 he began to contribute to the Gentleman's Magazine a daily register of the weather, month by month. It included barometric reading of pressure, and two temperature readings, in the early afternoon, and late in the evening. There was also a brief comment on the day's weather.
The new iPhone 6 and 6 Plus each have a sensor that gives readings for barometric pressure. Barograph (free), displays real-time pressure data from that sensor. Weather watchers will know dropping ...
Measurements of barometric pressure and the pressure tendency (the change of pressure over time) have been used in forecasting since the late 19th century. [66] The larger the change in pressure, especially if more than 3.5 hPa (2.6 mmHg), the larger the change in weather can be expected.