About Tropical Meteorology

El Nino

Greenhouse effect

Hurricane

Volcanic Activity and Climate

El Nino

       El Nino is the name given to a gentle warm breeze that sometimes wafts over the west coast of equatorial South America about Christmas time. It is one part of major global disturbance that occurs on average once every 5 or 6 years.

        Normally in December the South pacific is dominated by trade winds. The winds cause the ocean waters to pile up the West Pacific. During El Nino the pressure systems become disturbed as the low moves from Indonesia out over the Pacific. This is matched by the development of a high stretching from Australia northwards to Indonesia.

       Clearly there has been a dramatic change in the pressure in the South Pacific and the knock-on effects are both widespread and substantial. And the results of the South oscillation in the pressure systems stretch beyond the South Pacific and are truly world-wide. The warm waters displaced the normal cold ocean currents that well up from the ocean floor off South America and are vital to marine life because they bring with them the nutrient supply that is the basis of the complex coastal food web. With no nutrients rising to the surface, the plankton did not bloom and the fish no longer fed in their traditional grounds. 

Greenhouse Effect

       When we burn fossil fuels (principally coal and oil) we send extra quantities of carbon dioxide into our atmosphere. Many scientists think that within a century this gas could devastate our world.

       Carbon dioxide in our atmosphere, like the glass in a greenhouse, lets sunlight pass through, then catches and retains some of the sunlight's energy as heat. This greenhouse effect helps warm the earth's climate. If CO2 and other greenhouse gases such as methane, nitrous oxide and chlorofluorocarbons vanished tomorrow, the earth would become overnight a frozen, lifeless world like Mars. In fact, all these gases have been increasing since the start of Industrial Revolution.

Volcanic Activity and Climate

       Explosive eruptions emit huge quantities of gases and fine grained debris into the atmosphere. The greatest eruptions are sufficiently powerful to inject material high into the stratosphere, where it spreads around the globe and remains for many months or even years. This suspended volcanic material will filter out a portion of the incoming solar radiation, which, in turn, will lower air temperatures.

       The eruption of Mount St. Helens in1980 and the Mexican volcano El Chichon in1982 provided scientists with an opportunity to study the atmospheric effects of volcanic eruptions with the aid of more sophisticated technology than was available in the past.

       El Chichon emitted far great quantities of sulfur-rich gases. These gases combined with water vapor in the stratosphere to produce a dense cloud of tiny sulfuric acid droplets. such clouds take several years to settle out completely and are capable of decreasing the mean global temperature because the droplets both absorb solar radiation and scatter it back to space. It now appears that long-lived volcanic clouds are composed largely of sulfuric acid droplets and not of dust as was once thought. Thus explosiveness alone is poor criterion for predicting the global atmospheric effects of an eruption.

      Many scientists agree that the cooling produced could alter the general pattern of atmospheric circulation for a limited period. Such a change, in turn, could have an effect on the weather in some regions.

        

Hurricane

       Hurricanes are cyclones that develop over the warm tropical oceans, and have sustained winds in excess of 74 miles/hour. These storms are capable of producing dangerous winds, torrential rains and flooding.
       Hurricanes are formed from simple complexes of thunderstorms. However, these thunderstorms can only grow to hurricane strength with cooperation from both the ocean and the atmosphere.
        First of all, the ocean water itself must be warmer than 26.5C  (81F). The heat and moisture from this warm water is ultimately the source of energy for hurricanes. Hurricanes will weak rapidly when they travel over land or colder ocean waters -- locations with insufficient heat and/or moisture. 






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El Nino

Hurricane

Greenhouse Effect