This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Tuesday, October 30, 2012

Frankenstein Storm: Pressure in the eye is 943 millibars--so what?

Hurricane Sandy NOAA

11/03/2012: This now includes a correction about where the storm originated.

Well, to answer the question in the last post, I am indeed stuck in Washington D.C. My first hurricane experience! So far, it's the lull before the storm (but I only finished this post after the storm). A gentle drizzle when we woke up this morning (Monday), increasing rain throughout the morning, a lull between rainbands of the hurricane around noon, and increasing wind and rain again now, mid-afternoon. We journeyed out to see what is going on in the stores, and found that at Target, there were four items that racing (or, rather, had raced) off the shelves: water jugs (small bottles still seemed to be in ample supply), bread, batteries, and camping gear.
         I've been watching the pressure in the eye of the hurricane with interest because two days ago, a I reported that it was 972, and that one prediction was that it might go as low as 950 mb.  The last reading I saw was 943 mb, but the internet in the hotel where I'm staying has the speed of a phone line, so I haven't been able to update my stats. (I saw 941, but the official record appears to be 943 mb. It broke the record of 946 mb from the 1938 "Long Island Express" hurricane.)
        I'm going to try to explain what has gone on as my way of learning it, but first I refer you to a very authoritative source, that of meteorologist Cliff Mass. Excellent discussion! I am taking my discussion from a number of sources including Mass's blog, and the Seattle Times new service, which in turn, compiled its information from the Associated Press, The Washington Post, and Tribune Washington Bureau.
        Unlike most Atlantic hurricanes, Hurricane Sandy did not begin as a wave off the coast of west Africa, but rather started in the Caribbean. A low-pressure air trough was spun into a slow counterclockwise rotation by weak winds around October 19, and thunderstorms over the next few days sucked up energy from the warm Caribbean waters. On October 22, it became Tropical Depression 18, quickly developing into Hurricane Sandy which started moving north. The Gulf Stream is as much as 5 to 9 degrees warmer than normal for this time of year. It grew into a suze where tropical storm level winds (39-74 miles per hour) extended over a diameter of 940 miles. It is the largest Atlantic storm known to have made landfall, at least since the government began keeping records in 1988, and very likely well before that time.
        The puzzles to experts, and amateurs alike, were "why did it come so far inland so late in the year, and what's going to happen about it since most hurricanes like this head back out into the Atlantic where they peter out over the cold waters?"  They are usually chased out to sea by "onshore weather patterns," (a very unhelpful phrase in the Seattle Times article!). As I mentioned in my previous blog, there was a high-pressure system in the North Atlantic Oscillation west of Greenland, and a huge low pressure trough moving eastward across the U.S. The two combined to push/pull it westward. 
        Even though Cliff Mass's last post was on Sunday (Oct. 28), a day before the storm made landfall, his description/prediction of what would happen after landfall is intriguing (and you really need to see the color images on his blog to visualize this).  The storm transforms from a tropical storm with a warm core into an "extratropical storm" with a cold core.
        First point: tropical storms generally form in the tropics where there are not large gradients horizontally in temperature (tropical to subtropical at most). They derive their energy from the warmth and moisture of the oceans.
        Second point: midlatitude storms form in regions of large temperature gradients. If you travel through the mid-latitudes at this time of year, you go from the climate of New Orleans to that of, say, Juneau, Alaska! Midlatitude storms get their energy not from the warm oceans, but from the warmth on their south side and its contrast to the colder air on the north side. This temperature gradient fuels our mid-winter storms. These are cold-core storms.
        Cliff Mass predicted that Sandy would go an "amazing transition" from a warm-core to a cold-core storm (through what is called an "Extratropical Transition"). Many tropical storms weaken when they go through this transition, but Mass thinks not for Sandy. The two energy sources (ocean energy source and latitude-dependent energy source) work together for long  enough to result in an overall strengthening and expanding system.
        In his earlier October 26 blog, Mass compared/contrasted the predictions of two major models, considered to be the most important ones: The European Center model (ECM) and the US GFS model. Up until late last week, the US GFS model was predicting a low pressure of around 950 mbar that would swing up over Long Island on Tuesday morning, and then hang around inland, eventually moving northward on Wednesday. On the other hand, the ECM was forecasting a sub-940 mbar low pressure making landfall on central New Jersey, then circles around there before moving northward. To quote Mass "The European Center and GFS models tend to overdo the deepening in such situations, so I don't believe we will see anything below 950-960 mbar." Last I saw, the measured pressure in the low was 941 mbar. Good job ECM!
       Let's summarize: An eye pressure of 941 mbar, sustained winds at 90 mph, and a diameter of nearly 1000 miles. To the right, I post one version of the Saffir-Simpson Scale, though many others only have wind speed. Using wind-speed alone, this would be a category 1 scale. But, using pressure in the eye, it would have been a category 4. Am hoping some readers will pitch in and explain this one! Meanwhile, we mull over that 20 years ago, Halloween 1991, the "Perfect Storm" unfolded almost exactly like this one.

Friday, October 26, 2012

Frankenstorm: Hurricane Sandy

Friday 2:00 p.m. EDT NOAA projection of the path
of Hurricane Sandy
I have a meeting in Washington D.C. until Monday morning and am wondering if I'll be able to fly out of here back to Illinois due to the fact that a monster storm, Hurricane Sandy, is creeping up the east coast of the U.S. If the NOAA projection to the left is correct, it looks like I'll make it, but if not... The head of the National Weather Service has been quoted as saying that he's estimating $1 billion U.S. damage (let's remember that last year there were fourteen billion dollar disasters in the U.S., most of them storm related (hurricanes, tornadoes, floods, droughts, heat waves, and wildfires).

This storm is getting a huge amount of press coverage, given that it's only a Category 1 hurricane at the moment.  It is getting close to full moon, which means high tides, which means greater than average storm surge as Sandy approaches. Surge and flood damage in the south east is already severe. It caused at least 21 deaths as it passed over Haiti, Jamaica and Cuba.

The mysterious thing about this storm is the strong hook to the northwest that you can see in the graphic above starting on Monday.  This is very unusual for an Atlantic Hurricane, and even more unusual, apparently, for an October hurricane. This is the tail end of the hurricane season, supposedly. So, what's going on with this storm? It turns out that it's not all that easy to dig out of the WWW and news stories.  (At the bottom of this post are some links that I found helpful.) However, a post by Will Komaromi, Ph.D. student at the Rosenthal School of Marine and Atmospheric Science, University of Miami, is excellent, and much of the material below is from that post.

Normally, as an Atlantic hurricane moves north, it encounters cooler water, drier air away from the tropics, and greater wind shear. In other posts, I've discussed the individual effects of these on hurricanes.  However, this year, the Gulf Stream along the Atlantic Coast is warmer than usual.

To address this, we need to look at what is happening out west.  There is a large cold weather system, currently bringing snow to Colorado, moving across the country, including a deep trough of low pressure (called a 'midlatitude trough'.) This storm is a large low-pressure system, so, very simplistically, it'll suck Hurricane Sandy in to the west. When the two systems interact, there will be a lot of action--thunder, lightning, rain by the bucketful, and snow. Very similar events occurred 21 years ago in the now famous "Perfect Storm" of October, 1991, that became the topic of a best-selling book and movie. There is an excellent graphic on Komaromi's WWW site above, comparing the two systems at the scale of the continental U.S.

Instead of weakening, the hurricane system merges with the mid-latitude trough (including strong jet stream winds that can provide extra energy to the hurricane). Sharp gradients in air temperature and density between the two systems works (creating sharp pressure gradients, known as the baroclinic instability) works opposit of the weaking effects described above.  Air moving out (diverging) from the hurricane system at upper levels combines with the baroclinic instability to create a low-pressure eye to the storm. The lower the pressure in the eye, the stronger the hurricane.  In the Perfect Storm, the pressure dropped to 972 mb in the eye; Komaromi says that it's possible that the pressure in the eye of Sandy could be as low as 950 mb.

A final factor in this is that the pressure system lying over the eastern North Atlantic, known as the North Atlantic Oscillation, is in a negative phase, meaning that there is high pressure to the north east of the hurricane that will prevent it from curving out over the Atlantic like most hurricanes do.  It's helping it to move westward (called retrograde by the meteorologists) right into the east coast of the U.S.  All-in-all, it looks like the northeast is in for a prolonged (days) period of severe wind and drenching rains, and that my childhood stomping grounds in western Pennsylvania are going to get a lot of snow from the cold part of this combined system.

I'll join with other meteorologists and bloggers to say stay safe, be prepared to be self sufficient, and to help your neighbors. Especially, check on elderly relatives and friends who may be vulnerable to early winter cold if the power goes out!  And, get out and vote early if you live in these regions; in most, early balloting is already underway. Election Day isn't until November 6, but some meteorologists are concerned that this storm could take down powerlines that are going to take a long time to repair, days to even weeks.

Other references:



Tuesday, October 23, 2012

L'Aquila trial, rogue climate experiment, and realignment of science-society relations

L'Aquila, Italy government office destroyed by
the 2009 earthquake. Image from
Scientists have been watching events taking place in a small medieval town, L'Aquila, Italy, unfold for about three years, and the world took notice yesterday when six scientists and one civil servant were convicted of manslaughter and sentenced to six years each in jail, and a total of over three million dollars in fines, amongst other penalties. This verdict came only a week after it was discovered by the Canadian environment ministry discovered that a California businessman more-or-less secretly spread 100 tons of iron dust into the ocean off western Canada to increase the growth of plankton to increase the salmon fishery. Something is changing in the relation between science, scientists, and members of the general public.
       One thing that these two events have in common is that a person outside the "scientific establishment" and associated government agencies was involved both in gathering data and interfacing with the public.  Here's a short summary of background as best I can infer from press reports (which, in the case of L'Aquila, are often misleading). see footnote**
     In 2008-2009, swarms of earthquakes shook L'Aquila, a town that sits in one of the most seismically active regions of Italy. Residents were unnerved by the constant seismic activity, but had a long history of living with it.  The older residents were used to leaving their houses and remaining outside, sometimes in their cars or encampments, until the activity subsided. Compounding the tension in 2009, a local resident who worked as a laboratory technician, was gathering radon data, and made unofficial predictions that alarmed the residents. He was cited for "procurato allarme"--essentially instigating public alarm, and was forbidden to make any public pronouncements. (There is no evidence in the peer-reviewed literature that radon measurements can reliably predict earthquakes and there is substantial evidence that radon emissions vary considerably due to many factors.)
       Because of the escalating tension, six scientists and one government official, members of the Serious Risks Commission,  were hastily, were called to a one-hour meeting in L'Aquila with the goal of furnishing the residents "with all the information available to the scientific community about the seismic activity of recent weeks". From here on, events are complicated, and the reader should see the account referenced below for details.  Briefly, the government official reported to the public after the meeting that the scientists had said the seismic situation posed "no danger", a point of contention throughout the trial. The scientists appear, in fact, to have said that the probability of a large earthquake was small, but that it was possible.
      Whatever the details, the residents of L'Aquila said that they felt reassured by the message conveyed and therefore, according to their account, did not follow the age-old tradition when the tremors continued, but remained in their houses. On April 6, an earthquake struck, tragically killing 309 people. 
     A year later, the six scientists and government official were charge with involuntary manslaughter for being negligent in giving advise on the risk to public safety. Note: they were not accused of failing to predict the earthquake as many news reports continue to assert.
     Yesterday, the judge handling the case convicted the seven on the charges and handed down a jail sentence that was 50% longer than requested by the prosecution. It may be three months before the logic behind this sentence is revealed. According to Italian law, the sentence can be appealed, and the seven will not be jailed unless the appeals fail. 
     The scientific community is in shock, especially the geologic community and those who work with hazards, risk management, and public safety, but there are obvious parallels running through other communities, such as the medical community. Scientists are already becoming wary of existing communication protocols, even in countries like the U.S. where much thought and experience, both in earthquake and volcanic hazards, has gone into defining how the interface between science and the public is addressed. As I wrote this, an announcement appeared on the WWW that the head of the Major Risks Committee in Italy and several of its top scientists have resigned saying that there are no longer good working conditions. There is a real danger that public safety will be compromised as scientists become afraid that any comment they make can put them in jeopardy of prosecution. I join with my many colleagues around the world in condemning the verdict--it helps neither the victims, nor potential victims of future events, nor those who try to ameliorate the effects of natural hazards and keep them from turning into disasters.
    But, I would like to ruminate on something else (since this is a rare diversion of my posts from pure science). Although it may seem unrelated, a story just reported last week initially by the Guardian, and then by the New York Times, raises concerns that are not entirely unrelated. Just as the convening of the meeting of the Serious Risks Commission was precipitated by the activity of a member of the general public, in this case a California business man, Russ George, has precipitated environmental concern because of a geoengineering experiment.  Geoengineering is an activity in which human intervention (the engineering part of geoengineering) is used in a large-scale attempt to alter the natural balances of the planet (the geo- part). The pros and cons of geoengineering are an issue of active debate in the scientific community. There have been carefully designed, peer-reviewed, small-scale geoengineering experiments of the kind that George performed, but this one was apparently carried out in secrecy, without peer review of the procedures, nor, apparently, a statement to the community of environmental impact. The argument that the experiment took place outside the territorial waters of Canada is a red herring.
     George was reportedly paid $2.5 million by the Haida people of northern British Columbia, to scatter 100 tons of iron dust in the Pacific off the coast of northwestern B.C. The Haida have relied for centuries on the salmon runs, and have been suffering after the crash of salmon nurseries in the Pacific. Their waters are depleted in iron, and the addition of iron in this experiment spurred growth of the plankton. Since plankton absorbs carbon dioxide and then dies and falls to the bottom of the ocean, it is one proposed scheme for burying atmospheric carbon.
The Haida apparently hoped that in addition to increasing the salmon fishery, they could take advantage of carbon offset credits.
     The problem with this experiment, and with many geoengineering proposals in general, is that if the experiments go awry, the can endanger the planetary system at a very large and potentially catastrophic scale.  The so-called "precautionary principle," under which many European countries operate, states that if a given action has the potential for harm, even in the absence of scientific consensus that the action is harmful, the burden of proof that it is not harmful rests on those taking the action. That is, potentially harmful actions should be avoided.
     The absence of transparency, as well as the fact that the experiment appears to have violated two international agreements that Canada had signed, has made scientists and policy makers as well, angry. (The international experiments are the United Nations convention on biological diversity and the London convention, which found that large-scale experiments in ocean fertilization are unjustified.)
      These seemingly unrelated cases bring a few points to attention. Each one involves an area of science (earthquake prediction; ocean fertilization) getting a lot of attention from scientists and policy makers. Considerable thought has been put into protocols, transparency and accountability for work in the subject.  There are methods for testing hypotheses and for dissenting with the prevailing paradigm: data are gathered and tested according to principles long established by the scientific method. Such visible issues attract a variety of people, including some ill-trained in scientific methods. In these two cases, there was/is a person operating outside the bounds of these methods and outside the protocols that have been established for use of the information. Scientists holler that either data do not support the rogue claim (the situation with radon and earthquakes and with previous ocean fertilization experiments), or that the design of the experiment and its results are not subject to scrutiny (the case with the current rogue fertilization experiment). In either case, the public is often subjected to ambiguous and contradictory opinions and recommendations. Continuous communication of data to the public and education of the public about the issues are necessary. Only in this case will individuals have the skills and then the resources to make informed decisions, to elect informed officials, and to evaluate both data and advice provided. In L'Aquila, such procedures should have led to improvements in construction and reenforcement of buildings; that did not happen. In the case of ocean fertilization, this should lead to an informed public that can decide if massive geoengineering practices should be attempted. 
     Some established procedures are better than others. Clearly there were flaws in the way that events were handled at L'Aquila. But even in places like the U.S. earthquake and volcanology programs where considerable thought has been given to crisis procedures, there are likely to be flaws that will be revealed when the system is stressed. Those who acted in good faith to establish the procedures, and those who work within the system acting with integrity, should not be made scapegoats when these flaws are revealed. It is imperative that failures be used to improve the system so that it will be better when the next situation arises. The relations between scientists, policy makers, and the public are changing, some even saying that that the L'Aquila trial is a "watershed case." (Tom Jordan, director of the Southern California Earthquake Center). Geoengineering may be a L'Aquila of the future.

***An excellent detailed account of the events by Stephen S. Hall can be found here in Nature:

Here is another thoughtful discussion from one who has been involved with volcanic risk:http://www.nature.com/news/2011/110914/full/477251a.html

Monday, October 15, 2012

Felix Baumgartner: The physics of supersonic falling

Felix Baumgartner exiting his balloon to begin his descent
October 14, 2012


Twenty four miles (128,100 feet) above Earth, a man encapsulated in a suit much like the astronauts wore on the Moon stepped out of his capsule to begin a death-defying plunge. Whether you approve or not, it's difficult not to admire the courage, imagination, and training that leads up to such a feat!

According to the press, he reached a velocity of 833.9 miles per hour (roughly 371 meters per second) and a Mach number of 1.24. Using the definition of Mach number (M = v/c, where v is his velocity and c is the speed of sound), the speed of sound was 298 meters per second. 

The speed of sound in a perfect gas depends on the square root of the temperature (in degrees Kelvin). The sound speed in air at ambient sea level temperature is about 330 meters per second, and so he would have still been falling at supersonic velocities, though his Mach number would have been slightly less.

Now, here's a thought exercise: If he had jumped through a bottle of bubbly champagne, and attained the same velocity, his Mach number would have been as high as 15 or 30 because the speed of sound in bubbly mixtures is greatly reduced by the presence of bubbles. It could be as low as 10-20 meters per second. The physics behind this is that the sound speed depends on the compressibility and density. A bottle of champaign with tiny bubbles has the density of the liquid (~water) but the compressibility of the gas (CO2), and hence a significantly lower sound speed than pure water and also less than pure air at the same temperature.

Even more extreme (and this is not a suggested experiment!!), if he had attained this velocity in a pot of boiling water, his Mach number could have been of the order 300!! Boiling water has the compressibility of champagne, but an additional factor that reduces the sound speed to only a few meters per second--latent heat transfer as water changes phase (liquid-to-steam-and back to liquid) as the tiny pressure pulses of sound waves pass through it. Here's a reference to the calculations:

Kieffer, Susan Werner, Sound speed in liquid-gas mixtures: Water-air and water-steam, Journal of Geophysical Research, v. 82(20), page 2895-2904, 1977. 

(Yep, I did publish in 1977, and yep, I'm that old! But, it was one of my first papers! I was working on the dynamics of eruption of Old Faithful geyser and it's boiling water, as an analog for eruptions of volcanoes.) 

Here's the abstract from that paper:

The sound speed of a two-phase fluid, such as a magma-gas, water-air, or water-steam mixture, is dramatically different from the sound speed of either pure component. In numerous geologic situations the sound speed of such two-phase systems may be of interest: in the search for magma reservoirs, in seismic exploration of geothermal areas, in prediction of P wave velocity decreases prior to earthquakes, and in inversion of crustal and upper mantle seismic records. Probably most dramatically, fluid flow characteristics during eruptions of volcanoes and geysers are strongly dependent on the sound speed of erupting two-phase (or multiphase) fluids. In this paper the sound speeds of water, air, steam, water-air mixtures, and water-steam mixtures are calculated. It is demonstrated that sound speeds calculated from classical acoustic and fluid dynamics analyses agree with results obtained from finite amplitude ‘vaporization wave’ theory. To the extent that air and steam are represented as perfect gases with an adiabatic exponent γ, independent of temperature, their sound speeds vary in a simple manner directly with the square root of the absolute temperature. The sound speed of pure liquid water is a complex function of pressure and temperature and is given here to 8 kbar, 900°C. In pure water at all pressures the sound speed attains a maximum value near 100°C and decreases at higher temperatures; at high pressures the decrease is continuous, but at pressures below 1 kbar the sound speed reaches a minimum value in the vicinity of 500°–600°C, above which it again increases. The sound speed of a water-air mixture depends on the pressure, the void or mass fraction of air, the frequency of the sound wave, and, if surface tension effects are included, on bubble radius. The admixture of small volume fractions of air causes a dramatic lowering of the sound speed by nearly 3 orders of magnitude. The sound speeds of the pure liquid and gas end-members are nearly independent of pressure, but the sound speed of a mixture is highly dependent on pressure. Calculated values for water-air mixtures are in good agreement with measured values. The sound speed in a single-component two-phase system, such as a water-steam mixture, depends on whether or not equilibrium between the phases on the saturation curve is maintained. Heat and mass transfer which occur when equilibrium is maintained cause the sound speed to be much lower than under non-equilibrium conditions in which heat and mass transfer are absent. The sound speed in a water-steam mixture may be as low as 1 meter per second.