Strong Winds Wind Effects

Energy2green Wind And Solar Power System

Wind Energy DIY Guide

Get Instant Access

It is the steep barometric pressure gradient established between a tropical cyclone's outer edge and its central low that causes strong winds to blow inwards. Violent winds are one of the most dangerous and costly aspects of cyclones for people living on Pacific islands (Table 5.1). Strong winds have a number of effects. They generate large waves at sea and drive these onshore, damaging coral reefs and causing severe coastal erosion. They also contribute to storm surge, resulting in widespread sea flooding of low-lying shorelines. Fierce winds tear at vegetation, stripping foliage, uprooting trees and flattening crops. Large amounts of salty sea spray whipped up from the ocean are blown inland and poison coastal forests. Figures 5.3 and 5.4 illustrate the destructive effects of Tropical Cyclone Heta in January 2004 on the coastal forest of Niue island.

One of the reasons why high wind speeds are very damaging is that for a non-aerodynamic shape such as the flat side of a building, the pressure exerted on the surface facing the wind is roughly proportional to the square of the wind speed. So, for example, 100 km h-1 winds will exert four times as much pressure as 50 km h-1 winds, not twice as much (Krishna 1984). In addition, on the leeward side of flat obstacles, a partial vacuum is created. This causes an outward suction effect acting in the same direction as the wind pressure on the opposite side of the obstacle. Together these forces can wreak much destruction. Flying debris such as corrugated roofing materials also poses a significant hazard. Figure 5.5 shows a ruined coastal village in eastern Fiji, two days after Tropical Cyclone Ami struck in January 2003, where many people were left homeless.

Table 5.1. Maximum wind speeds and costs of resulting damage in the Kingdom of Tonga for tropical cyclones over the 20-year period 1982-2001.

Tropical cyclone

Year

Maximum winds (knotsa)

Cost of damage (million T$b)

Deaths

Isaac

1982

130

18.7

6

Ofa

1990

140

3.2

1

Sina

1990

100

-

0

Kina

1993

120

-

3

Hina

1997

90

-

0

Ron

1998

125

-

0

Cora

1998

75

19.6

0

Waka

2001

140

104

1

Source: Tonga Meteorological Service. a1 knot = 1.852 km h-1.

bT$1 (1 Tongan Pa'anga) is equivalent to 0.38 € and US$0.50 (January 2007 rates, not adjusted).

Source: Tonga Meteorological Service. a1 knot = 1.852 km h-1.

bT$1 (1 Tongan Pa'anga) is equivalent to 0.38 € and US$0.50 (January 2007 rates, not adjusted).

Tropical Cyclone Waka
Fig. 5.3. Vegetation on the western coastline of Niue island, stripped of foliage by high winds and waves during Tropical Cyclone Heta in January 2004. The surface of the emerged marine terrace, which was overtopped by waves, is approximately 23 m above sea level. Photo by Mosmi Bhim.
Effects Cyclones
Fig. 5.4. Dead forest on Niue island, poisoned by salty sea spray that was blown inland by Tropical Cyclone Heta in January 2004. Photo by Douglas Clark.
Cyclone Heta
Fig. 5.5. Demolition of a village in the Lau Islands of eastern Fiji by Tropical Cyclone Ami in January 2003. Source: Fiji Navy, supplied by the Fiji Ministry of Information.

Was this article helpful?

0 0
Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

Get My Free Ebook


Post a comment