Getting the Wind Up

A plant disease called “myrtle rust” has appeared in New Zealand, apparently after the spores have been blown across the Tasman sea from Australia. That’s over four thousand miles. The prevailing winds are from Australia to New Zealand and the cyclones and storms that hit New Zealand are formed in or off the coast of Australia, or further north in the Tropics, or further south in the Southern ocean.

In these areas low pressure areas form and consequently winds blow from the surrounding areas of slightly higher pressure into the lower pressure area and start to swirl clockwise. The clockwise movement is the result of the Coriolis effect, which is difficult to explain, but relates to the fact that when an object moves north or south on the rotating Earth, it moves closer to or further from the Earth’s axis of rotation.

Combination of Image:Hurricane isabel2 2003.jp...
Combination of Image:Hurricane isabel2 2003.jpg and Image:Coriolis effect10.png to illustrate the Coriolis force better. (Photo credit: Wikipedia)

A low pressure area sucks in air and it is forced up in the centre where it cools and forms clouds and rain. As this process continues, the pressure at the centre of the low drops and the spiral of winds gets tighter and, if the low is very deep, more destructive. I’m not sure why a low deepens, when one would think that all the in-rushing air would fill the low, and the few explanations that I have read have not convinced me.

On a larger scale, bands of winds circle the Earth, with winds coming from the west in the south and the north of the two hemispheres, with prevailing easterly winds nearer the Equator in both hemispheres. The sometimes destructive cyclones and anticyclones are mere ripples in this larger flow.

English: Map of the North Pacific Subtropical ...
English: Map of the North Pacific Subtropical Convergence Zone (STCZ) within the North Pacific Gyre. Also the location of the Great Pacific Garbage Patch. (Photo credit: Wikipedia)

Even in quiet wind conditions there is usually a breeze, often stimulated by local conditions, such a large lake or sea. All that is required for a breeze is a small differential in temperature, with local heating expanding the air or local cooling causing it to contract.

The sea will absorb heat from the sun more slowly than the land, and the air over the land is therefore warmer and becomes less dense. Consequently a breeze develops flowing from the sea to the land. The reverse occurs at night, when the land cools more quickly than the sea. Such conditions are however very local and are often unnoticeable and overridden by cyclonic and anticyclonic wind conditions.

The formation of breezes. Diagram A) Sea breez...
The formation of breezes. Diagram A) Sea breeze B) Land breeze Français : Formation des brises. Diagramme A) Brise de mer B) Brise de terre (Photo credit: Wikipedia)

Within a large weather system, such as a cyclonic system, local conditions may affect the wind directions and strength. Often the wind direction and strength varies widely locally, giving rise to conditions that are described as “blustery”. While such conditions may be good for drying laundry, they making sailing a difficult pastime. Sailing races can be won or lost depending on whether or not the sailors catch the good air or fall into a pocket of stale air.

The strength of the wind obviously varies tremendously. At the one end of the scale a breeze may cause a flag to limply stir, while at the other end of the scale, a really large storm may uproot trees and destroy houses. In some parts of the world tornadoes may form when weather conditions are right and may sweep destructively over the land, ripping apart anything that stands in their way.

Large, violent tornadoes can cause catastrophi...
Large, violent tornadoes can cause catastrophic damage when striking populated areas. (Photo credit: Wikipedia)

There is energy in the wind, and efforts are being made to economically harvest this energy to reduce our reliance on fossil fuels. Such fuels are not infinite, and we will sometime or other run out of them. It may be that we have enough fossil fuels to last centuries, but getting at them involves the disruption of mining, and as they are used up, mining will become even more disruptive than it is now. Mining even small amounts will become very expensive.

It makes sense to develop machines to harvest wind power, and the signs are that this is becoming economically more competitive. At one time, before petrol engines became common, the only ways to power transport were wind and steam, and it may be that petrol and other fossil fuelled engines may only have a relatively short time span of usefulness, maybe only a century or so.

Miners digging coal
Miners digging coal (Photo credit: Wikipedia)

We also use fossil fuels for our plastics. Almost everything in our modern world has a large proportion of plastics in it, sourced almost entirely from oil. It remains to be seen if we could replace our need for fossil resources from renewable resources.

Hay fever suffers may curse the wind as it blows pollen up their noses and into their respiratory systems, but many plants rely on the wind to propagate themselves. A case in point is the myrtle rust I mentioned at the start of this post. Plant pollen can travel thousands of kilometres and fall all I know can circle the Earth. It’s an efficient way of spreading the reproductive material, but its a really inefficient way of getting the reproductive material to a member of the species of the opposite gender.

Pollen from a variety of common plants: sunflo...
Pollen from a variety of common plants: sunflower (Helianthus annuus), morning glory Ipomoea purpurea, hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa) and castor bean (Ricinus communis). The image is magnified some x500, so the bean shaped grain in the bottom left corner is about 50 μm long. (Photo credit: Wikipedia)

Obviously it works best where the plants are grouped together, and it works even better if the plants are hermaphrodites, but it does work (occasionally) when the plants are far apart. This mechanism for reproduction probably arose a long time ago before plants invaded the land. plants growing in the sea, and many animals too, just broadcast their gametes into the sea and trust in at least some of them finding other gametes so that they can grow into mature individuals. (Caution: It’s complicated!)

We often hear the sound of wind. It can be caused by wind blowing through trees or other plants. It can be caused by wind blowing through gaps in our houses, mainly doors and windows. We build our houses to protect us from the wind and other aspects of the weather, as a sort of synthetic cave, I guess.

Wind chimes. {| align="center" style...
Wind chimes. {| align=”center” style=”width:80%; background-color:#f7f8ff; border:2px solid #8888aa; padding:5px;” |- | Camera and Exposure Details: Camera: Canon PowerShot S3 IS Lens: Canon 1:2.7-3.5 USM 12x Zoom Lens Exposure: mm (mm in 35mm equivalent) f/4 @ 1/125 s. |}Category:Taken with Canon PowerShot S3 IS (Photo credit: Wikipedia)

We can even make music (well, musical sounds) using the wind. Many people have “wind chimes” which are metallic objects strung on wires arranged so that the wind can bash them together, making a chiming noise. Some people like them, and others dislike them (I fall into the second camp).

Strings can be placed on a sounding board and used to produce musical sounds, and such “Aeolian Harps” were once as common as wind chimes. An accidental Aeolian harp can be heard in the sound that power and telephone lines make when a strong wind blows.

English: Aeolian harp at Tre-Ysgawen Hall This...
English: Aeolian harp at Tre-Ysgawen Hall This aeolian harp is in the grounds of Tre-Ysgawen Hall. When the wind comes from a particular direction it ‘plays’ the harp and ethereal musical sounds are produced. (Photo credit: Wikipedia)

Time for this post about wind to wind down now, if you will excuse the pun.

This picture from a NASA study on wingtip vort...
This picture from a NASA study on wingtip vortices qualitatively illustrates the wake turbulence. (Photo credit: Wikipedia)

Weather, seasons and Christmas

English: Spring is on its way Snowdrops in Hat...
English: Spring is on its way Snowdrops in Hatfield churchyard are harbingers of spring although at the time there was still plenty of wintry weather around. (Photo credit: Wikipedia)

At this time of the year, we are looking forward to spring, even though spring is officially about a month and a half away, which puts us slap in the middle of winter. There are signs, though, that spring is around the corner. Plants which bloom early in the year are starting to show signs of life, and the buds on some trees are showing some green as they prepare to burst into green bunches of leaves.

Every burst of clear weather seems to produce both warmth during the days and frostiness during the night. It seems that each cycle is slightly warmer than the last but that might just be me wishing an end to winter! The wetter times don’t seem to be bringing the freezing cold wintry blasts, though there is the occasional shower of hail or sleet mixed in.

English: Snow pellet/Graupel Français : Grain ...
English: Snow pellet/Graupel Français : Grain de neige roulée (Photo credit: Wikipedia)

The main reason for the hope that winter is drawing to a close is the now noticeable lengthening of the days. The day length is up from 9 hours and 12 minutes or so at the solstice to 10 hours and 12 minutes or so today. The day is lengthening at a rate of more than 2 minutes per day at the moment.

I don’t mind the cold as such. It’s the constant shrugging on and off of clothes as one transitions between indoors and outdoors that bugs me, and the necessity of keeping the house warm, which in itself means going outdoors to fetch fuel, which of course involves donning extra clothing and all the annoyances which go with that.

English: A 1901 fashion plate of a Chesterfiel...
English: A 1901 fashion plate of a Chesterfield overcoat. (Photo credit: Wikipedia)

There is a sort of seasonal drag in the clothing department, incidentally. I’ve noticed that I tend to resist slinging on the extra clothing in autumn and early winter and I’m likewise reluctant to take it off as the weather and temperatures improve.

Of course, July and August are the warmer months in the Northern hemisphere and northerners will be experiencing shorter days and colder weather. As we track in to spring you Northerners will be heading towards autumn and eventually winter. We will be looking forward to spring and summer, which pretty much bracket Christmas for us.


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Of course, since I originate from the Northern hemisphere myself I have had to become accustomed to having Christmas in summer and I personally think it’s great. With Christmas at the start of summer we can enjoy it without the hassle of keeping warm. It does make the traditional northern Christian festival meal seem a bit heavy though and who want to roast a turkey for hours in warm weather?

It does conflate two events however – the Christmas holiday period and the traditional summer holidays which seem to merge seamlessly into one another. One effect of this is that people seem to be unavailable from Christmas Eve through to the beginning of February, which was something that I had trouble adjusting to when I moved here.

English: A rather damp Sligachan old bridge on...
English: A rather damp Sligachan old bridge on Skye. This ‘summer’ holiday photo shows some light rain on Skye with Glamaig just visible through the mist! (Photo credit: Wikipedia)

Tradesmen tend to be unavailable from the start of the Christmas period well into the New Year and some smaller shops also close for an extra week or two. Obviously this has its advantages for the shop keepers, but I still feel disappointed when my favourite barber is closed until mid-January!

We have a Public Holiday for the Queen’s Birthday in June (June 1 this year) and the next Public Holiday is on October 26, which means that there is almost 5 months of the year without a Public Holiday during the darkest part of the year. One advantage of having Christmas in mid-winter is that it gives one something to look forward to as the days close in.

English: The Royal Gibraltar Regiment at the p...
English: The Royal Gibraltar Regiment at the parade for the Queen’s Birthday, Grand Casemates Square, Gibraltar (Photo credit: Wikipedia)

Winter is cold, obviously, but that in itself is bearable (up to a point). But there’s a phenomenon called the “chill factor” which makes windy winter days seem much colder. My weather app on my phone tells me that the temperature outside is 6.9 degrees centigrade, but the it “feels like: 4 degrees centigrade. It recommends 3 – 4 layers of clothing and a windproof layer. Brrrrr! Fortunately it doesn’t seem too wet out so walking the dog should not be too arduous.

In this season of the year we tend to get low pressure system after low pressure system forming in the Tasman Sea which bring cold fronts across the country with associated fronts bringing storms and rains. Sometimes they come down from the tropics and hit us from the north, usually bringing warmer but wetter weather from the north. We tend to get better more settled weather when a high pressure system comes to us, spun off from  a high pressure system over Australia.

The Tasman Sea caused some violent and spectac...
The Tasman Sea caused some violent and spectacular bursts of water at the Pancake Rocks, Punakaiki. (Photo credit: Wikipedia)

(I took a break and walked the dog. While we out we were hit by what you could euphemistically call a “wintry shower”. In other words, wind, hail and rain!)

Many people from the Northern hemisphere tend to find Christmas in summer unsettling, but I quite like it. I’m not a barbecue person, but the occasional meal taken outside is very pleasant, and it is becoming more usual over here to have a barbecue on Christmas Day. Another advantage is that when one is Christmas shopping one doesn’t have to dodge the weather as one dashes between shops and fights one’s way through the crowds of late shoppers, all after that elusive and critical last gift.

Barbecue barbecook
Barbecue barbecook (Photo credit: Wikipedia)

However, although I think that mulled wine is an abomination, there is something pleasant about sipping your favourite alcoholic tipple in front of a roaring fire. Maybe while doing something traditional, like listening to a CD of carols carefully enunciated by Korean choirs who have no word of the English language and who have little to no idea about the traditions involved.

One thing about having winter at this time of the year, it means that I can tease relatives who live in the Northern hemisphere as we climb up towards warmer weather while they slide down to autumn and winter. However I have to acknowledge that they can get their revenge in six months later as the cycle of the seasons continues to repeat. I’ll be looking out the thermal undies when they start talking about snowdrops and crocuses.


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