Mod 6.2 - Impact of Natural Disasters on the Biosphere (Climate Phenomena) Flashcards
Causes of hailstorms
Hail forms when a thunderstorm updraft lifts a water droplet above the freezing level in the atmosphere. The frozen water droplet then accretes water vapour, which freezes once it comes in contact with the frozen droplet. This process causes a hailstone to grow. Once the hailstones have become heavy enough to sink faster than the upward air motion that had previously suspended them, they begin to fall in a hailstorm.
Causes of East Coast Lows
An ECL is an intense low pressure system off the coast of eastern Australia. ECLs develop when a LPS sits over one of the warm water eddies of the East Australian Current, and is bounded by a HPS over NZ and another one approaching from the west of Australia. The LPS gains heat and intensifies due to the warm water, resulting in increased evaporation and thus heavy rain. The HPSs help to raise the wind speeds around the LPS, resulting in high velocity winds.
Causes of floods
When water inundates land that is normally dry, this is called a flood. Floods are caused by high volumes of rainfall in short bursts of time that the capacity of water-holding bodies is overwhelmed.
Causes of bushfires
The prevalence of bushfires is governed by high fuel loads accompanied by a period of below average rainfall, high wind speeds and low humidity. Natural bushfires are usually started by lightning. Australia is prone to bushfires because we have tall trees and eucalyptus trees, whose leaves have oil which is flammable. However, bushfires can also start by human action, for example arson, campfires and sparks from equipment such as chainsaws.
Impacts of hailstorms
A hailstorm is a weather phenomenon in which solid balls of ice, called hail, fall from the sky. For native forests, severe hail and wind will result in the shredding and perhaps removal of leaves and even bark from trees. This reduces the shading effect on the ground below - affecting both plants and animals that live in the understory. It also increases the fuel load on the ground for future bushfires. The combined effect of less shading, possibly followed by severe fires, could have a significant impact on ground dwelling animals. Hail can also cause serious damage to vehicles, skylights, glass-roofed structures, livestock and most commonly crops.
Impacts of ECLs
High wind speeds lead to extreme sea conditions with accompanying erosion of beaches and important coastal habitats. Heavy widespread rainfall can inundate the coast, resulting in flash and/or major river flooding.
Falling trees and flash flooding have caused injury and fatalities on the land to both wildlife and humans.
Impacts of floods
They can cause loss of life, damage to property, destruction of crops, loss of livestock, and deterioration of health condition owing to waterborne diseases. In natural ecosystems, floods can remove fertile topsoil, drown animals and small plants, and cause eutrophication (because nutrients, fertiliser, faeces etc. ending up in waterways) in downstream water ways.
However, there are some positive effects of flooding. Many wetland ecosystems rely on regular flooding as part of their rejuvenation. Some floods bring large numbers of fish down river streams for fishing communities. .
Impacts of bushfires
Bushfires can have major effects on ecosystems. They can burn forests which could take hundreds of years to recover. This can lead to destruction of habitats. Bushfires can also kill or injure animals, reducing numbers of already vulnerable native species. They can also destroy crops and properties, cause loss of human life, and also cause pollution in the atmosphere and surrounding land as well as in waterways.
However, there are also some positive impacts of bushfires. These include increased seed dispersal and germination for species such as Banksia, increased soil fertility due to the recycling of matter, and the removal of introduced species and the competition that they bring, since unlike native species, they are not generally fire-adapted.
