Atmospheric pressure and Atmospheric Temperature

1. Atmospheric Pressure and Atmospheric Temperature Andino Maseleno Alif bin Haji Alias

2. Atmospheric Pressure Atmospheric pressure  is the force per unit area exerted on a surface by the weight of air above that surface in the atmosphere of earth (or that another planet). In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure  caused by the weight   of air above the measurement point. On a given plane, low-pressure areas have less atmospheric mass above their location, whereas high-pressure areas have more atmospheric mass above their location. Likewise, as elevation increases , there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation.

3. The standard atmosphere (symbol: atm) is a unit of pressure equal to 101325 Pa or 1013.25 milibars or hectopascals .

4. The pressure of an atmospheric gas decreases with altitude due to the diminishing mass of gas above each location. The height at which the pressure from an atmosphere declines by a factor of e (an irrational number  with a value of 2.71828..) is called the  scale height  and is denoted by  H . For an atmosphere with a uniform temperature, the scale height is proportional to the temperature and inversely proportional to the mean molecular mass  of dry air times the planet's gravitational force per unit area of on the surface of the earth. For such a model atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so the exact determination of the atmospheric pressure at any particular altitude is more complex.

5. The mean sea level pressure (MSLP) is the atmospheric pressure at sea level  or (when measured at a given elevation on land) the station pressure reduced to sea level assuming that the temperature falls at a  lapse rate  of 6.5 K per km in the fictive layer of air between the station and sea level . This is the atmospheric pressure normally given in weather reports on radio, television, and newspapers or on the Internet . When barometers in the home are set to match the local weather reports, they measure pressure reduced to sea level, not the actual local atmospheric pressure. The reduction to sea level means that the  normal range of fluctuations  in atmospheric pressure is the same for everyone. The pressures that are considered  high pressure  or  low pressure  do not depend on geographical location. This makes  isobars  on a weather map meaningful and useful tools.

6. Atmospheric Temperature Atmospheric temperature  is a measure of temperature  at different levels of the Earth’s atmosphere . It is governed by many factors, including incoming solar radiation, humidity and altitude.

7. In the Earth's atmosphere, temperature varies greatly at different heights relative to the Earth’s surface . The coldest temperatures lie near the  mesopause , an area approximately 85 km to 100 km above the surface. In contrast, some of the warmest temperatures can be found in the thermosphere , which receives strong ionizing radiation.

8. References http://en.wikipedia.org/wiki/Atmospheric_pressure http://en.wikipedia.org/wiki/Atmospheric_temperature