Hurricanes: Their Nature and Impacts on Society - Climate Science ...

TROPICAL CYCLONES ON PLANET EARTH
Figure 3.10 Horizontal cross-section through a simulated hurricane at a height of ,3
miles (5 km). The contours clearly outline the eye wall with the most intense ascending
air on its south side, as well as in the spiral b<strong>and</strong>s feeding into the storm. Figure
provided by Dr Mel Nicholls, Colorado State University; this work is also reported in
Nicholls <strong>and</strong> Pielke (1995)
3.1.3 Decay
A mature hurricane can cover thous<strong>and</strong>s of square miles <strong>and</strong> is a striking
atmospheric feature as viewed from space. On the Earth's surface, the mature
hurricane can lead to great property damage <strong>and</strong> loss of life. Fortunately,
mature hurricanes last for only a limited time as decay is inevitable. Decay
can occur either over the ocean or over the l<strong>and</strong>.
Over warm ocean waters, an increase in the vertical wind shear because of the
movement of the storm into a high shear environment can disrupt the hurricane
by reducing the effectiveness of the linkage performed by thunderstorms
between the lower <strong>and</strong> upper troposphere (see Figure 3.12). In some cases,
strong wind shear can even rip a hurricane apart. This is a primary reason for
hurricane decay over a warm ocean. Three other factors can contribute to
decay. The first is the movement of dry air into the center of the storm,
therefore inhibiting thunderstorm development. This could occur due to the
movement of a dry air mass off a continent into the spiral inflow of the
hurricane. A second reason is the passage of the hurricane over a mountainous
isl<strong>and</strong> such as Cuba or Hispafiola, which can disrupt the inflow into the center
79