Environmental Engineering Reference
In-Depth Information
clouds associated with hurricanes can be clearly seen,
together with the eye of the storm.
Photo: courtesy of Ross Reynolds.
to rise, it cools, and on reaching saturation, large quantities of latent heat are released, as
indicated by the temperature anomalies in Figure 7.14c. It is this process which is
believed to be responsible for giving the storm so much energy. Once the storm moves
over land the main source of energy is lost and so it decays.
By understanding the type of atmospheric and surface environment which is most
favourable to tropical cyclone development, efforts have been made to predict their
occurrence on a seasonal basis. The factors which favour a large number of hurricanes in
the Atlantic are: warm sea water off Africa, weaker than normal trade winds, more
easterly waves off West Africa, a wet Sahel area of West Africa, and no El Niño in the
Pacific. As a result, the number of Atlantic hurricanes and tropical storms is quite
variable (Figure 7.16). Researchers in the United States have had considerable success in
predicting the number of hurricane-strength storms in the Atlantic, including the near-
record year of 1995 with twelve, suggesting that the right factors are being included in
the model.
WEATHER PREDICTION
We all know from experience how much daily and seasonal variations in weather
influence our lives. Clearly it is useful to have an idea of the weather which is in store for
us. But how is it possible to foretell the weather? In the past we relied heavily on
folklore. 'Red sky at night, shepherd's delight; red sky in the morning, shepherd's
warning', says one country adage. 'When there's sheep-backs [cumulus
