Drought in New Zealand.
Drought is the big killer when it comes to farming and the land. Floods make more dramatic television but drought is a long drawn out event that destroys crops and trees and has a lasting effect long after the rains have returned.
New Zealand does not have any deserts as such but it does have many arid areas caused by
‘rain shadow’ The section on precipitation deals with much of this subject but New Zealand, which is a temperate country with a range of mountains down the middle, is likely to suffer badly from drought.
These two maps one for temperature and the other for rainfall illustrate the problem, for the end of the century, The outlook, unfortunately, is a lot worse than illustrated. The scenario selected by the government is for a mid range of CO2 production but currently the World is burning more fossil fuels than projected.
There is research to show that the change has already started, and it may be in your lifetime.
New Zealand does not have any deserts as such but it does have many arid areas caused by
‘rain shadow’ The section on precipitation deals with much of this subject but New Zealand, which is a temperate country with a range of mountains down the middle, is likely to suffer badly from drought.
These two maps one for temperature and the other for rainfall illustrate the problem, for the end of the century, The outlook, unfortunately, is a lot worse than illustrated. The scenario selected by the government is for a mid range of CO2 production but currently the World is burning more fossil fuels than projected.
There is research to show that the change has already started, and it may be in your lifetime.
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Temperature 2080-2090
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Precipitation 2080-2090
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The left hand map shows a 2.2c increase in temperature and the right hand map shows a 10% decline in rainfall for the East coast which are the flat populated and farming coastal areas.
Taken together they represent big challenges for farmers.
Broadly speaking moisture laden air from the west rises when it hits the mountains and as it rises it cools and sheds its moisture as rain. The air then passes over the mountain and as it loses altitude it warms and can now hold more moisture.
Taken together they represent big challenges for farmers.
Broadly speaking moisture laden air from the west rises when it hits the mountains and as it rises it cools and sheds its moisture as rain. The air then passes over the mountain and as it loses altitude it warms and can now hold more moisture.
The dry air comes down the mountain and as it warms it is thirsty for moisture and sucks what moisture it can from the soil.
Remembering the principle that for every 1c rise in temperature the atmosphere can hold 8% more moisture then the air is capable of sucking a considerable amount of moisture from the soil.
As a summary the increased Westerly winds will give the East coast a much higher proportion of dry weather with a combination of higher temperatures and less rain.
We are not likely to be short of water overall but we are likely to have much more rain on the West coast and much less on the East coast which will bring some challenges.
Remembering the principle that for every 1c rise in temperature the atmosphere can hold 8% more moisture then the air is capable of sucking a considerable amount of moisture from the soil.
As a summary the increased Westerly winds will give the East coast a much higher proportion of dry weather with a combination of higher temperatures and less rain.
We are not likely to be short of water overall but we are likely to have much more rain on the West coast and much less on the East coast which will bring some challenges.
Could a change in the Southern jet stream change New Zealand weather?
With the terrible disruption to the weather in the Northern hemisphere, caused by the loss of Arctic ice and the stalled jet streams, could a change in our Southern jet reams cause a New Zealand drought?
A quick look at a typical weather map shows a series of high pressure systems proceeding from the West but interspersed with wet low pressure systems between them. This gives New Zealand its sunny climate with rainfall every week or so. If we are lucky.
A quick look at a typical weather map shows a series of high pressure systems proceeding from the West but interspersed with wet low pressure systems between them. This gives New Zealand its sunny climate with rainfall every week or so. If we are lucky.
A quick view of the Southern jet streams.
This simple illustration shows the Southern hemisphere jet streams and how the wave in the system separates the high and low pressure systems. Dry high pressure systems separated by the wet low. As the wave progresses around the World it keeps the weather moving and changing.
Has climate change altered the jet streams?
The South Pole is completely different to the North Pole as the South sits on land and has three to four kilometres of ice sitting on it. Its not going to melt away in a hurry
However the loss of ozone in the atmosphere caused the Antarctic temperature to fall and the jet streams to move South and the increasing CO2 raised the temperature causing the jet stream to move North. Cancelling one another out but increasing the speed of the Westerly wind.
However the loss of ozone in the atmosphere caused the Antarctic temperature to fall and the jet streams to move South and the increasing CO2 raised the temperature causing the jet stream to move North. Cancelling one another out but increasing the speed of the Westerly wind.
Atmospheric circulation.
The illustration shows how the circulation of air delivers a high pressure system at around the 30s lattitude which in our case is roughly in the Great Australian Bight during the summer (and higher in the Winter).
At the temperature rises it increases the speed of circulation and spreads the range of the circulation South.
At the temperature rises it increases the speed of circulation and spreads the range of the circulation South.
Conflicting forces of Ozone and CO2.
The text taken from the 'Nature Blog' Judith Perlwitz. Ozone v CO2. gives the answer.
This raises the question of whether wind and precipitation patterns will revert to their pre-ozone-hole conditions as the ozone layer recovers. Two new studies — one by Polvani and colleagues1 in Geophysical Research Letters and the other by McLandress and colleagues2 in Journal of Climate — show that as the ozone hole closes, increasing greenhouse-gas concentrations will counter the effects of ozone recovery, preventing atmospheric circulation from returning to 'normal'.........................While greenhouse-gas concentrations are anticipated to continue rising over coming decades, the Antarctic ozone hole is expected to close, so these two factors will begin to exert competing influences on the location of the westerly jet and dry zones (Fig. 1). The 'winner' of this competition has not yet been determined.
This raises the question of whether wind and precipitation patterns will revert to their pre-ozone-hole conditions as the ozone layer recovers. Two new studies — one by Polvani and colleagues1 in Geophysical Research Letters and the other by McLandress and colleagues2 in Journal of Climate — show that as the ozone hole closes, increasing greenhouse-gas concentrations will counter the effects of ozone recovery, preventing atmospheric circulation from returning to 'normal'.........................While greenhouse-gas concentrations are anticipated to continue rising over coming decades, the Antarctic ozone hole is expected to close, so these two factors will begin to exert competing influences on the location of the westerly jet and dry zones (Fig. 1). The 'winner' of this competition has not yet been determined.
Summary
There has been a steady increase in Westerly wind that has brought more rain to the West coast and drier periods to the East. This trend is likely to increase leading to an increase drought to the East coast.
We will not be short of rain but it will be in a different area.
There has been a steady increase in Westerly wind that has brought more rain to the West coast and drier periods to the East. This trend is likely to increase leading to an increase drought to the East coast.
We will not be short of rain but it will be in a different area.