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Entries in weather (6)

Tuesday
Jan182011

Grasping the scale of the Queensland floods

Sam at Oceanographers Choice has an excellent post up that seeks to address a journalist’s statement that Queensland (Australia) “should have seen the flood coming”, using a quick climatology exercise relating rainfall and the climate pattern called El Nino Southern Oscillation (currently in a strong La Nina phase) in that part of the world.  In short, the answer is probably not, no; ENSO is an OK predictor at annual scales, but probably not usefully predictive at the monthly scale that would be needed to prepare a response to an anticipated flood event.

Seasonal rain cycles in Queensland, Australia

My friends in Brisbane (where I lived for 8 years during college) have all been affected directly by the flood or know someone who is.  One friend rescued neighbours in a boat and another is still missing a friend in Toowoomba, west of Brisbane.  The floods are getting a bit of press in the US, but perhaps not as much as they should because the body count is low (~25 compared to >600 in the concurrent Brazilian floods).  That’s mostly a function of Queensland’s low population, so don’t be fooled; we’re still talking about a once-a-century or worse flood event.  75% of the state is affected, which might not sound like much until you realise that Queensland is three times the size of Texas at over 715,000 sq. miles!  It is a truly gargantuan issue, especially now that there is also some flooding in Victoria and other southeasterm states.  This is the equivalent of a flood that extends from Cape Hatteras to Miami and Savannah to Houston!  Total cost is expected to be on the order of $10 billion, which in a state of 4.5 million is over $2,000 per person.  Its staggering.

Australia truly is a land of droughts and flooding rains.

 

Tuesday
Sep142010

Amazing satellite video of Hurricane Igor

Hurricane Igor is a big beast allright.  If you don’t believe me, check out this spectacular QuickTime movie from the Space Science and Engineering team at the University of Wisconsin, and after you pick your jaw up off the floor, go over to their blog and check out the rest of their great data.  Just look at that eye; I love the way the shadow casts across it as the sun goes down.  You can also see convection cells to the left and the lower right of the storm, where air is moving rapidly upwards. (if the video stops, double click it to restart).  Thats just made of awesome.

 

Why is this on a marine science blog?  Well, its over the ocean, so that counts, right?  Seriously, hurricanes are really marine phenomena.  They’re driven by the tremendous amount of heat that builds up in the tropical oceans during the summer months.  That heat warms and moistens the overlying atmosphere, as the energy stored in the ocean fluxes back into the air.  Warmer air is less dense and so you end up with a focused area of low pressure, and the moist air rising up to colder higher parts of the atmosphere, causing rain.  Add in some favourable winds and and dash of the coriolis effect and the whole thing starts to spin, forming into a tropical cyclone.

Via my colleague Brian Colle at Stony Brook U.

Sunday
Aug082010

Hola de nuevo, México!

Headed back to Quintana Roo in light of a good weather forecast and a chance to finish some chemical ecology sampling we aimed to do last time but were denied due to weather and other concerns.  What’s chemical ecology?  Its the study of how animals interact with the chemicals in their environment and shape their behaviour accordingly.  In this case, we’re especially interested in what whale sharks can smell, what sort of “odor landscape” they live in, and how they exploit this to find food.

Unlike a lot of “big” marine scienctists that work off ships in the UNOLS fleet, we actually work from small boats close to the coast, so weather is a key factor.  Do me a favour and pray to whatever deity or natural force works for you, in order that we get some favourable conditions to finish this work so we can move on to other things, OK?  Me?  I’ll be praying to Chaac, the mayan rain god, not for rain, but for no rain.  More importantly, I’ll pray to the head honcho of all Mayan gods, who also happens to be the wind god - Kukulcan - for no wind.  I may as well pray to Joe Pesci, but it can’t hurt.

Tuesday
Mar302010

Ocean Conveyor running AMOC

This post was chosen as an Editor's Selection for ResearchBlogging.orgResearchBlogging.org

If you’ve ever seen the disaster movie “The Day After Tomorrow”, then you’ve been introduced to the idea that one day the global ocean conveyor might stop.  Its a pity (or perhaps not) that the movie was such a sensational introduction to the concept, because its a pretty serious possibility.  By way of short explanation: one of the things that makes life possible on this rock is that the ocean redistributes heat that arrives on the earth’s surface between the tropics, sending it to the higher latitudes by way of warm surface currents.  There, the waters are cooled and made more dense (both colder and saltier) by the polar ice caps; they then sink and begin a slow meander back to the tropics, eventually returning to the surface to complete the cycle.  Without effective redistribution of this sort, the tropics would bake and the polar zones would sink into a deep hard freeze (in both cases much more so than “normal”).  The climate in the UK, for example, would be much more like Siberia were it not of the tempering effects of the Gulf Stream continually bringing heat from the Caribbean to the North Sea.  An important point about the conveyor is that it is driven from both ends: by the suns heat near the equator and by the cooling effect of all that ice at the poles.

 Why would the conveyor grind to a halt?  The equatorial heat doesn’t show any sign of stopping; if anything its getting hotter.  No, the biggest fear is for the other driver: if the polar ice caps melt too much, there will no longer be a big enough reservoir to chill and brine the surface waters and they will cease to sink.  Some data from recent years suggested that this was happening, and happening fast.  Well, it seems as though Armageddon isn’t here just yet.  A new paper by CalTech/NASA’s Josh Willis in the journal Geophysical Research Letters uses a more complete data set than ever before to conclude that the conveyor, or more specifically a major section of it called the Atlantic Meridional Overturning Circulation (AMOC - hence the corny title of my post) measured at 41°N (near where it says “Atlantic” on the figure above), is not slowing.  In fact, there is some evidence that it may have sped up marginally in recent years, perhaps in response to warming and expansion of Atlantic waters.  The data were consistent across both satellite sources and sensor arrays deployed in the oceans, so it would seem like a pretty robust study (though I am no physical oceanographer).

I am sure I speak for everyone on the bonnie British Isles when I heave a sigh of relief.

But wait?  What light through yonder ice-shelf breaks?  Tis Greenland, and its seeing more of the sun!  In the very same issue of Geophysical Research Letters, a different group of authors report that ice loss is increasing from the Greenland ice sheet.  This is one of the major impacts of recent climate warming and the greatest contributor to increases in sea level globally.  It would also freshen the north polar waters, further reducing the driving force behind the global ocean conveyor.


My response to this news is to marvel at - and grapple with - the complexity and dynamics of the earth and its climate system.  Scientific results with seemingly opposite implications can come out (in this case in the same journal issue), but without threatening the major underlying pattern; I doubt, for example, that Dr. Willis would disagree with the concept of man-made climate change.  Faced with this seeming contradiction, its perhaps no wonder that many folks grapple with the Big Ideas at the heart of global climate change, and even doubt that it exists at all.  I for one have no doubt  that things are changing, and changing fast.  It may just be that some of the really big features of the climate system (including ocean currents) are slower to respond than others.  Its a bit like turning an oil tanker, which may be an unfortunately apt analogy…

Willis, J. (2010). Can in situ floats and satellite altimeters detect long-term changes in Atlantic Ocean overturning? Geophysical Research Letters, 37 (6) DOI: 10.1029/2010GL042372

Khan, S., Wahr, J., Bevis, M., Velicogna, I., & Kendrick, E. (2010). Spread of ice mass loss into northwest Greenland observed by GRACE and GPS Geophysical Research Letters, 37 (6) DOI: 10.1029/2010GL042460

Friday
Mar192010

Ului inches closer

Looks like Ului will cross the coast right over the Whitsunday Islands.  Good luck to the folks in Proserpine and Bowen.

This picture from the Australian Bureau of Meteorology

Friday
Mar192010

Cyclone Ului approaching the Queensland coast

Cross your fingers for the people of Queensland, Australia, who are facing an impending cyclone, Ului.  It was just downgraded to a Category 2, but you never relax with these things right?  Tourists and researchers have been evacuated from Heron Island and several others, but it looks like it might cross a little further north.  Here's hoping it avoids major populated areas.