Meteorology, Atmospheric pressure, Wind velocity and Direction, Temperature

Meteorology

The word meteorology is derived from the latin Greek word 'meteor' and 'logos' which means the lofting of the particles. Lofting particles are those particles which go upward in the atmosphere and remain there for the long interval of time. However, meteorology is the study of the characteristics behaviour of the atmosphere and its interaction with the underline surface. Also, the meteorology is the study of the physical, dynamical and chemical state of the atmosphere. Different parameters of the atmosphere are as follows:

a: Atmospheric pressure

b: Wind velocity and Direction

c: Temperature

d: Humidity

e: Radiation

f: Precipitation

g: Wind

The detail description of the above-determined terms are as follows:

a: Atmospheric pressure:

The pressure that is exerted by the atmosphere is referred as the atmospheric pressure. This character is the very much important characteristics of the atmosphere. Atmospheric pressure depends profoundly on the height and it is inversely proportional to it. Generally, at the sea level, the atmospheric pressure is high so its standard value at the sea level is taken as 760mm of Hg. As the height increases, the pressure goes on decreasing. The units in which atmospheric pressure is measured are the minibar, mm Hg, atmosphere.

The instrument which measured the atmospheric pressure is called Frontiers barometer. This instrument is a U-shaped tube which is filled with mercury, which is kept on a crisis or an aneroid barometer. By the deflection of that, the pressure is determined. The instrument which records the variation of the atmospheric pressure continuously with time is called barograph. A curve that joins the place of the equal atmospheric pressure is known as the isobar. The synoptic chart helps us to locate the places having high and low atmospheric pressure.

b: Wind velocity and Directions

The air which is in the motion is called wind. The horizontal component of air movement parallel to the earth surface is generally called as the wind. While the vertical component of the wind is known as air current or air parcel. A meter which measures the wind velocity is called as an anemometer. Anemometer consists of the 3 or 4 hemispherical curves which are fixed in a horizontal plane to a sleeve, which can freely rotate about the vertical axis. Then, the rotation is transferred to the gauge mounted under the curves that counts the number of rotation or revolution. The counter is so designed that the increased in the reading of counter divided intervening time interval in hours gives the wind velocity directly in Km/hr. The wind direction is the direction from which it is blowing. It is measured by the wind vane.

The synoptic chart with the data of the wind velocity and the wind direction helps us in studying about the cyclone and anticyclone. This kind of data is also helpful in the study of evaporation. Wind speed varies with the height above the ground level. No standard level has been specified for the anemometer. For the purpose of meteorological data, the velocity of air is assumed to be according to the power of low profile. i.e;

V/V₀= (Z/Z₀)^0.1

Where V₀₌Observed velocity at height Z₀

V= Observed velocity at height Z

c: Temperature

Temperature is defined as the degree of hotness or coldness of a body or a place. In other words, the temperature is defined as the condition which determines the ability to transfer heat to other or receives heat from them. Usually, two scales are used in it, one is degree celsius and another is degree Fahrenheit. In degree celsius(⁰C) ice point is 0⁰C and the steam point is 100⁰C. Where in another scale (i.e Fahrenheit scale) ice point is 32⁰F and the steam point is 273⁰F.

Temperature is measured by the instrument called thermometer. The thermometer is placed in a standard instrument shelter which is called as steven screen whose purpose is to observe the unobstructed air circulation is there around the thermometer and at the same time thermometer is being protected from the direct sun rays of the sun and from the precipitation. The shelter consists of the all which is made of the wood on the all four sides which help to provide the good ventilation and a place wooden suffice at the top and bottom. The shelter is kept at about the 1.2 m above the ground level while the bottom of the surface is horizontal and the top of the surface is with some of the slopes, the front surface is provided with the door which can be opened at the time of observation. The temperature so measured is called the ambient air temperature or dry bulb temperature. A curve is plotted which joins some places of some temperature is called an isotherm.

Diurnal variation of temperature

The maximum temperature is measured at 2'O clock and the minimum temperature is measured in the morning. Comparing the sea and the continental there is a drastic change in the continental area. On the sea and the continental area, there is a diurnal variation of the temperature.

1: In the 24 hours of the each day, temperature changes are much more gradual over the sea than over the land.

2: In the diurnal variation, in the sea level, the temperature is less than 1⁰C where as the temperature varies over the continent is 15 to 20⁰C.

3: Near the coastal area or region, the diurnal variation of temperature depends on the wind speed. If the wind blows from the land to sea, its temperature is high and if the wind blows from the sea to land, its temperature is less.

4: The temperature of land is very low when the calm condition of the wind occurs. In the contrary, the temperature is less when wind speed is high.

5: The variation of the temperature is also affected by the cloud condition. If the day is cloudy, it has relatively less temperature and if the night is cloudy, it has a relatively high temperature.

Humidity

The water vapour content of air at any one place at any time is known as the humidity. The moisture in the atmosphere is provided by the hydrological cycle. The hydrological cycle circulates the water between the atoms [here: soil surface, storage, lakes and streams, plants and animals, glacial ice and the oceans]. The hydrological cycle includes the evaporation-condensation and precipitation.

However, the moisture is lost by the precipitation, it is made good by continuous evaporation from the water bodies. The entire process of maintaining the constant water vapour content of the atmosphere is called the hydrological cycle. This hydrological cycle is characterized by an ongoing cycle, without any beginning or end. There is a very close relationship between the atmospheric humidity and air temperature. The moisture holding capacity of atmosphere mainly depends on on the temperature.

References:

Miller, Jr. G.T. Living in the Environment. Wadsworth Publication, 2003.

S.C., Santee. Environmental Science. India, New Center: New Center Book Agency (P) Ltd, 2004.

T., Richard. Environmental Science Towards a Sustainable Future. India: PHI (P) Ltd., 2008.

Lal, D.S. Climatology, Sharda Pustak Bhawan, Allahabad.(2010)