The Intertropical Convergence Zone

It took me three goes and a nights sleep to get the name right

I was talking to someone yesterday about my negativity when it comes to other people's dogmas. She said I should leave it out.

But what am I supposed to do when confronted with this: …

Quote from the Little Shop of Physics under the heading of Theory (In science the word "theory" means "catch 'em young and teach 'em wrong and they'll be dumb their whole life long.)

It is very warm along and around the equator, a region we call the tropics, since the sun shines so directly there throughout the year.

[This in itself is quite correct half the time. Not like summer at the Poles where it is true all the time. Where is goes wrong is in the amount of albedo the tropics has.]

As you know, when air is heated, it expands becoming less dense and more buoyant, that is, it becomes very light and wants to float.

Since pressure in the atmosphere decreases as you go up, the rising warm bubble of air expands adiabatically, doing work to push away surrounding air and therefore cooling as it rises and leaving a void of low pressure behind.

As the rising air cools, the water vapour in it also cools and then condenses into cloud droplets, which eventually collide with one another, coalescing to form bigger and bigger droplets until the droplets get so big that they fall out of the cloud as rain.

Since it is always so warm in the tropics, this kind of rising motion that forms rain is going on all the time, supplying water to the rainforests."

This is where I stopped reading as it was tying me up in knots. How much more so the desperately simple minds of puddings whose only claim to fame is that they can fill out forms correctly?

First of all, the rain isn't warm when it deliquesces. The tropopause in the tropics is higher than anywhere else. And the water at the top of it is super-cool.

Furthermore it is this super-cool water that is reflecting sunlight back into space.

My point being that the premise about the ITCZ is based on fallacy.

Were we to teach future meteorologists facts not fancies, would they find themselves other jobs or go on to become visionaries instead of hacks?]

The converging air cannot go sideways or down through the ground, so it is forced to rise once more. The latitudinal band in which this occurs is called the ITCZ or Intertropical Convergence Zone, because it is where convergence happens in the the tropics. This convergence line is not always on the equator, though. It moves to the north and south as the seasons change, following the location of most intense sunshine.

[I highlighted the only fact in the essay in bold. The rest is absolute nonsense if you only take the time to think about it. Start off with a bad attitude and criticise it. I left one more gaping flaw for you to expose.]

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3 thoughts on “The Intertropical Convergence Zone

  1. 7 to 13 November 2nd Quarter at: 00:36. Spells with a time of phase at 12 or 6 o'clock generally have cool low overcast in them for most of the week in Britain.However I presume there is a tropical storm building. I fact there looks to be a series generated according to the North Atlantic from T +48 at the time of writing. (Which thanks to British Management actually means Midnight Friday 9 November 2012.)I don't know what that crap over Northern Norway is playing at but the series of small fast flying Lows out of Newfoundland big-up at Iceland.Which is good weather for some of us.At T+72 it starts to break up between Iceland and Scotland -while at Newfoundland, another Low gets ready to take it on.There is a large set of fronts on that chart that look like they are zigzagging to Chile. When they do that it is usually as occluded fronts with lots of pink mice on them.Not today it isn't. We'll see.Note also the parallel fronts on that last pair of charts on today's page.> http://www.metoffice.gov.uk/weather/uk/surface_pressure.htmlThe Antarctic charts:Today's run shows a series of three major quake /storm conurbations.Let me take you through them:At T + 12 (mid day Wednesday the 7th, (I am using the UTC time-zone)) there is a large, well formed Low at 100 east. It is actually on the Antarctic shoreline -which is not what I am used to but it is summer there now so the sea ice is much less.The disc in it isn't that black. But again, I am not sure if that is due to the different temperatures and topography or just the fact there was a large earthquake in the system. Come back in March and I will tell you.By Thursday, the storm at 140 west is as large as the anticyclone below it. Its centre is less well defined, so it may two or three storms in the same basin or maybe one with two tracks (the sort of thing only discernible by satellite.)On Sunday, t 20 west, the third large system shows up and it remains at that latitude and longitude for the rest of the run.Several dark discs of precipitation show up in these things but I am no longer so sure they are directly related to earthquakes.Through all of this a series of Anticyclones have crossed Australia.To my delight they have all been as ridges hugging the coast but definitely on land. (The ones crossing oceans via America and Africa all stay in the sea.)This should confuse those on uk.sci.weather who insist that ridges and troughs run to their opposites and fill or decline.I have always seen the opposite is true and that likes attract while unlikes repel. Ridges track to anticyclones and do so from west to east.(At least in the Southern Hemisphere it does. I can't say I have ever paid it that much attention until I decided to write about elongations.)The anticyclones in the southern hemisphere suddenly became more motile. All the continents are showing a rapid discharge of their anticyclones from the eastern seaboard to the western ones.The result is that there are going to be less black discs of precipitation showing. What was I expecting in summer?It began last week or even the week before, with the whole system showing massive elongations. Little did I know so little I did know.I don't know how often there are large cyclones in the Atlantic Approaches without a tropical storm anywhere but this week's spell is one of them.These are the "official" seasons for the tropical ones -by ocean basin:Tropical cyclone seasons. Basin.Season start. Season end.North-west Pacific. April. January.North-east & Central Pacific. May. November.North Atlantic. June. November.North Indian. April. December.Australia & South-west Pacific. November. April.South Indian. November. April.http://tropicalcyclones.blogspot.co.uk/p/tropical-cyclone-seasons.htmlNovember features prominently but the reason for that has not been explained as far as I know.Here is my effort:In winter the continent called Antarctica doubles in size. In actual land mass it is about as big as Australia which (coincidentally?) is about as big as cyclones get in the southern hemisphere.Ice reaches out from the shoreline to quite a distance, usually symmetrically. If you include the permanent ice that holds the mainland pieces together, Antarctica is quite symmetrical.Storms that hit this sea ice add to it in the same manner that they add to the overburden on the land. They give up their water content.Once they give up their water, they become much less powerful storms and eventually rise over the landscape to become polar highs.I'm not sure how buffeting works but a perpetual rotation is not what then occurs. The so called Polar Cell is just pressurised air looking for a way out and it obeys the various complex gas laws while doing so.The result is that when an incoming storm loses definition the residue goes where it can. Coming back out of the system it creeps under the more powerful but lighter stuff incoming adding to its power. In fact it may be this "polar air" that is causing some of the rotation in the surrounding cyclones.These huge Antarctic cyclones have a knock on effect on the surrounding anticyclones pushing them farther north. In pushing them farther north, it both prohibits the anticyclones from crossing the land masses there (Australia, Africa and South America) and it pushes the ICTZ further north.In pushing all this weather further north it has a dramatic effect on the amount of precipitation that comes through the three continents to Antarctic waters.In November all this stuff south of Africa is taking place in perpetual sunlight.By April it is once more dark there more or less full time.The differences in the start dates for tropical cyclones is related to how far south the continents reach in their southern extremes. The one that reaches furthest south is on the eastern seaboard of the ocean that has the latest start. In fact there are no (or virtually no) tropical storms in the South Atlantic. The Hurricane season takes place in the North Atlantic from June on.The ICTZ is more or less stable over northern South America.The smaller of the three, Australia is the first one to allow anticyclones across it in the southern summer. This is where the ITCZ moves furthest annually.Africa with its huge bulk in the north and highest landmasses in the south only comes to 30 degrees south. Water crossing the Atlantic warm pool tends to go north into the northern Indian Ocean. It is made for building anticyclones. I wonder if there is a reason for the island of Madagascar being there, in much the same place as Ceylon off the Indian sub-continent. Come to think of it Tasmania is… no look at that region's submarine geography and you get an outline similar to north Africa….Hmmm. I wonder how long I would have to live to solve that one.

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