Cyclone      A cyclone is a general term for a weather system in which winds rotate inwardly to an area of low atmospheric pressure. The rotation is usually counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth. Size      The largest low-pressure systems are cold core polar cyclones and extra tropical cyclones which lie on the synoptic scale (up to 5000km in diameter).       Warm-core cyclones such as tropical cyclones, mesocyclones, and polar lows lie within the smaller mesoscale (up to 500km in diameter). Subtropical cyclones are of intermediate size (upto 2000km in diameter). Terminologies      Hurricanes and typhoons are the same weather phenomenon: tropical cyclones.  A tropical cyclone is a generic term used by meteorologists to describe a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has closed, lo...

  General weather system of India Weather & Climate      Climate refer to the sum total of weather condition and variation over large area for a longer period of time. Weather refers to the state of the atmosphere over an area at any point of time. The elements of weather and climate are the same, i.e. temperature, atmospheric pressure, wind, humidity and precipitation. On the basis of the generalized monthly atmospheric conditions year is divided into seasons.      India situated in the northern hemisphere; the tropic of cancer passes through the middle part of the country. As a result the southern half of the country has a tropical climate.  During the winter season in the Northern hemisphere, Northern half of the country is warmer than the areas of similar Latitude about 3° to 8 °  Celsius. This is due the fact that the Himalayas check the cold polar air mass entering into India. In other countries like USA the polar air mass inva...

 Cloud formation & Precipitation Cloud formation     Condensation of water above the Earth surface creates clouds. In general cloud develop in any air mass that becomes saturated (relative humidity become 100%).      Saturation can occur by way of atmospheric mechanism that causes the temperature of an air to be cooled to its dew point.  The following processes can be responsible for the formation of the clouds.      W hen air is forced to rise because of the physical presence of elevated land. As the parcel of air rises, it cools due to adiabatic expansion at a rate of approximately 10° C / km.       The development of clouds and resulting heavy quantities of precipitation along SW coast of India, during the SW Monsoon, is due to these processes.      A rain shadow is a patch of land that has been forced to become a desert because mountain ranges blocked all plant-growing, rainy weather. On o...

 G reenhouse gases & Global warming 30% of the portion of energy is reflected or scattered back to the space  Stratosphere absorbs about 19% of the available energy (like UV) is absorbed by the clouds, gases (like ozone), and dust. About the 51% of the sun’s radiation reaches the surface of the earth, and this can heat the surface to an average temperature of -20°C. If this is the case, water will remain as ICE all over the earth. There will be no water in liquid or in gaseous form, as a result Earth will appear as white Ball. Greenhouse Effect     Solar radiation is absorbed by the surface and re-emitted back to the atmosphere as longer wavelength. Absorption of longer wave radiation causes additional heat energy to the atmosphere. Over 90% of energy is directed back to the earth surface, and again this process is repeated, until no longer wave is available for absorption.    And this process contributes the heating up of earth to an average te...

 The Radiation Laws      The Earth atmosphere system is sustained by the supply of energy from the sun. solar radiation is the ultimate source of energy that results in the varied atmospheric condition experienced on Earth. To comprehend fully the role of solar energy in the function of atmosphere requires, actual understanding of the radiation laws . The following are the laws that governs the way in which the incoming solar radiation will react with the atmosphere as well as the surface of the Earth. The first law governs the relation between frequency, wave length and velocity. According to which the product of wave length and the frequency of the wave is a constant, which will be equal to speed of light. c = λ f    Where λ is the wave length, f is the frequency, and c is the speed of light (3 X 1010 cm / S). This law indicates wave length (λ) increases  frequency (f) decreases. That is short waver are characterized by high frequency and long...

Ocean Circulation     The ocean is constantly in motion, distributing water and heat to all corners of the globe. In effect, the ocean acts as a circulating machine that makes Earth’s climate equitable. Ocean currents follow well-defined courses.  Why? Difference in heating leads to the different in surface temperature. This difference causes the movement of water boy (Ocean) that form the current. This method of heat transfer is called as Convection; hence it is sometimes mentioned as convectional currents.  Just like that happens our kitchen while boiling water.     How important it is?   The ocean transports tremendous quantities of seawater, serving as a global conveyor belt over the planet. Abyssal storms stir the deep-ocean floor, shifting sediments on the seabed. El Niño currents generate unusual weather patterns throughout the world. Waves and tides are constantly changing and rearranging the shoreline.       ...

  Chemical properties of sea water & Residence time Chemical properties of sea water: The oceans  cover an area of 361 x 106 km2, or 70.8% of the earth's surface. From the mean depth of 3800 m. the volume of the ocean waters can be calculated to be 1370 x 106 km3. At the surface the density of sea water of normal salinity at 0o C is 1.028, and it increases with depth because of the slight compressibility of water under increased pressure. Seawater thus comprises about 91% of the weight of the hydrosphere and its composition can therefore be taken without serious error as giving an average composition of the hydrosphere. The circulation of the waters in the hydrosphere provides a mechanism for geochemical changes through weathering and transport of dissolved and solid materials.  About 68% of the land area is drained to the Atlantic Ocean but the constancy of ocean composition indicates that seawater mixing erases all (except local) variation in its chemical comp...

  Physical properties of sea water Water makes up more than 96% of the total mass of seawater, so it is appropriate to begin with a short discussion of the properties of water itself. The weather and climate on Earth are in several ways controlled by the physical properties of water. Some of the important properties are,   a. its expansion when freezing,  b. its infrared absorption causes water vapor to be the most important greenhouse gas,  c. its radiative properties cause water to be important in the radiation of heat away from Earth, d. Variations from place to place in its isotopic composition provide insights into several aspects of Earth science, e. The chemical property of water that is perhaps most important to the marine chemist is its high solvent power for polar substances and substances that form charged ions in solution etc.,    Physical properties of water:      The boiling point of water is unusually high. This very hig...

Hypsography of the continents and ocean floor       Hypsometry is the measurement of land elevation (relative to mean sea level). Bathymetry is the underwater equivalent. A hypsometric curve is a histogram or cumulative distribution function of elevations in a geographical area.         Continental margin Continental margin, the submarine edge of the continental crust distinguished by relatively light and isostatically high-floating material in comparison with the adjacent oceanic crust. It is the name for the collective area that encompasses the continental shelf, continental slope, and continental rise. Continental margins are about 28% of the oceanic area. A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water known as a shelf sea. Much of these shelves has been exposed during glacial periods.           The continental shelf (approx 0.1°), steep continental s...