Group items tagged

In the western Pacific they are called typhoons, and in the southern hemisphere they are called cyclones.  But, no matter where they occur they represent the same process.

Tropical cyclones are dangerous because of their high winds, the storm surge produced as they approach a coast, and the severe thunderstorms associated with them. Although death due to hurricanes has decreased in recent years due to better methods of forecasting and establishment of early warning systems, the economic damage from hurricanes has increased as more and more development takes place along coastlines.

Warm ocean waters (of at least 26.5°C [80°F]) throughout about the upper 50 m of the tropical ocean must be present.  The heat in these warm waters is necessary to fuel the tropical cyclone. The atmosphere must cool fast enough with height, such that it is potentially unstable to moist convection. It is the thunderstorm activity which allows the heat stored in the ocean waters to be liberated and used for tropical cyclone development. The mid-troposphere (5 km [3 mi] altitude), must contain enough moisture to sustain the thunderstorms. Dry mid levels are not conducive to the continuing development of widespread thunderstorm activity. The disturbance must occur at a minimum distance of at least 500 km [300 mi] from the equator. For tropical cyclonic storms to occur, there is a requirement that the Coriolis force must be present.  Remember that the Coriolis effect is zero near the equator and increases to the north and south of the equator.  Without the Coriolis force, the low pressure of the disturbance cannot be maintained.

"El Niño reduced the amount of food available so the birds probably switched to feeding on discards behind fishing vessels, increasing the number being hooked on longlines."

Not all climate effects are negative. The recent increasing trend towards stronger poleward winds actually benefits the wandering albatrosses. "Such winds make their flight more efficient," Dr Phillips told BBC News. "They can fly faster. Essentially, these winds make the cost of travel cheaper for them."

Scientists say the losses are the result of careless fishing practices and climate pressures.

Climate scientists believe they have found evidence to suggest that the loss of floating Arctic sea ice in the Barents and Kara seas north of Scandinavia can affect the global circulation of air currents and lead to bitterly cold winds blowing for extended periods in winter over Central Asia and Europe, including the UK.

the cooling effect is unlikely to last beyond this century

Rising global temperatures will eventually cancel out any localised cooling caused by loss of Arctic sea ice, although they said it is not possible to predict when this will happen.

At times ocean surface temperatures in the equatorial Pacific are colder than normal. These cold episodes, sometimes referred to as La Niña episodes, are characterized by lower than normal pressure over Indonesia and northern Australia and higher than normal pressure over the eastern tropical Pacific. This pressure pattern is associated with enhanced near-surface equatorial easterly winds over the central and eastern equatorial Pacific.

bnormally cold waters in the equatorial central give rise to suppressed cloudiness and rainfall in that region, especially during the Northern Hemispherel winter and spring seasons. At the same time, rainfall is enhanced over Indonesia, Malaysia and northern Australia. Thus, the normal Walker Circulation during winter and spring, which features rising air, cloudiness and rainfall over the region of Indonesia and the western Pacific, and sinking air over the equatorial eastern Pacific, becomes stronger than normal.

Significant departures from normal are shown in the accompanying figures for the Northern Hemisphere winter and summer seasons.