NASA image
(Reminder that this blog is now part of the AGU Blogosphere at http://blogs.agu.org/wildwildscience/ Check them out!)
I’ve often wondered about something. Suppose a 1000 meter wide space rock were to hit Nashville TN. Would I survive here in Huntsville in North Alabama?
It would depend on many factors of course. Nashville is about 165 km to my north. That’s a BIG factor. The size of the asteroid, and the angle of impact, are others.
Let’s say that it hit at a 60 degree angle and was a rather dense mix of rock with some ice. The ground in Nashville is made up of sedimentary rock, so that will also be a factor.
What’s the answer?
Do I survive? Probably not.
The scenario I am about to give you is based on IMPACT EARTH. It’s a program put together by scientists at Purdue University and Imperial College in London. They have recently updated the physics and you can check it out yourself online here.
So what would I experience at a distance of 165 kilometers?
The rock would begin to break up at about 70 km above the surface. I assumed an initial speed of 25 km /second. It would be slowed only very slightly by our atmosphere and hit the surface traveling 24.7 km/ second. The fragments of the asteroid would hit the ground over a relatively small area. An ellipse of around 1000 meters to 1500 meters.
The crater formed would be 16 km wide! That is over 10 miles for metrically challenged Americans.
At the time of impact everything down to 4 km would be vaporized. The vaporized earth and buildings would fill the crater back in and it would only be around 700 meters deep at the end. Downtown Nashville would be gone before anyone there knew it. They might have a couple of seconds warning at most.
The blast in Nashville would produce the same energy as nearly 6,000 15 megaton hydrogen bombs detonated at once.
Let’s assume I’m outside walking the dog in Big Spring Park in the middle of Huntsville. The flash in the sky as the rock hit the atmosphere would last only 2-4 seconds. It would be silent. No noise. The impact fireball would look 16 times larger than the sun.
If it’s sunny, walk outside and look up at the sun. Close your eyes and feel the warmth. The heat from the blast 165 km away would feel 27 times hotter than that. The heat would be instantaneous.
The Tunguska event in Siberia was from a much smaller space rock than we are talking about here. It leveled the forest for 200 miles around the impact.
I would suffer third degree burns and trees and grass around me will catch on fire. If I were inside when it hit, the burns would be less severe. Most of the city would still be alive.
It would still be quiet.
As I looked around in pain from the burns, I would see fires everywhere. People would be rushing outside to see what was happening.
33 seconds after the impact, Huntsville would feel an earthquake of magnitude 7.9. Most well built buildings would not collapse but many people will be injured by falling objects. It would probably knock me off my feet in Big Spring Park.
The fireball in the northern sky would be huge but about 2 minutes later a black cloud would soon be visible. This black cloud would be made of gravel sized rocks and very fine dust. The ejecta cloud arrives in Huntsville 3 minutes after the impact. It’s now very dark with fires burning as the ground shakes.
Hell would rain down for 5 more minutes. It’s not over though.
What winds over 300 km/hr (200 mph) will do to a home. This image is from the aftermath of an EF3 tornado in Oklahoma. Courtesy NOAA/NWS
Eight minutes after the impact an explosion so loud it will cause excruciating ear pain will be heard. Almost immediately, a blast of wind will hit the city. Winds will increase briefly to over 90 meters per second. That’s over 200 mph.
Even strong buildings will likely collapse. Anyone outside will literally be blown away. Frame houses that were on fire seconds before will be blown away.
How about those who are further south? The winds in Birmingham would only reach hurricane force. The thermal blast would not cause burns. Heavy damage from the 7.9 magnitude quake would be likely.
Astronomers think that objects like I described hit Earth twice every million years. Objects big enough to destroy a large city hit Earth every 3 centuries on average. The Tunguska event in Siberia in 1908 was one of these.
The rock that wiped out the dinosaurs was 10 km wide. Those type events are thought to happen only once every 300 million years or so.
Just something to think about…
Dan
sources:
Impact Earth Calculator- http://www.purdue.edu/impactearth
http://impact.ese.ic.ac.uk/ImpactEffects/effects.pdf
http://www.gps.caltech.edu/~sue/TJA_LindhurstLabWebsite/ListPublications/Papers_pdf/Seismo_1747.pdf
Science 300 (5627), 1882. [DOI: 10.1126/science.1077708]
Author: | Posted on: 3. November 2010 at 21:25 pm | Filed under: Astronomy, Atmospheric Science, Science, Space | 0 Comments
Note: Please bookmark the new site on AGU Blogs for the Wild Wild Science Journal- http://blogs.agu.org/wildwildscience/
I will continue to double post here and there for sometime..
People often ask if a flood, a snowstorm, or a hot summer was caused by climate change. The correct answer is to say that no one weather event can be blamed on climate change, but certain weather events become more likely to occur.
Here in the Southeast U.S. we had a very hot summer. Downright brutal actually. The hottest on record in many cities. Atlanta had one of it’s worst droughts ever recorded a couple of summers ago. There have also been some massive floods. Nashville was hit by what can only be described as a flood that might come once every 500 years.
Extreme weather events happen. You can count on it. It makes my job forecasting the weather extremely fascinating.
The question a group of atmospheric scientists asked recently is this. “Are extreme summer weather events becoming more frequent in the Southeast.”
The answer was a definite yes. The question then becomes-
WHY?
This is where an incredibly useful data set comes in. It will take a second to explain but believe me it’s worth it.
Several times each day, high speed computers use weather balloon data and surface observations to build a 3 dimensional model of the atmosphere. Ship reports and data from weather satellites are also used.
This analysis is used to give numerical weather prediction models a starting point. You cannot predict weather in the future unless you know mathematically what the weather is doing now. If you want to forecast for the globe, you need to know a starting point for the entire planet!
A few years back scientists had an idea. Why not use modern methods of making a global analysis and go back in time. Ship reports and weather balloons have been around a lot longer than high speed computers. The very sophisticated methods of coming up with an analysis of the atmosphere could be used to build a data set of the atmosphere for the past 60+ years!
They did just that.
In Europe the European Center for Medium Range Forecasting did it as well. They use a slightly different way of making the first guess for the numerical weather models, so we have two close but not identical data sets.
A new paper being published in the Journal of Climate contends that the increasing extreme summer weather over the Southeast U.S. is due to semi permanent high pressure cell over the Atlantic. The official name of this system is the NASH. That stands for North Atlantic Subtropical High. Most meteorologists call it the Bermuda High.
The Bermuda High pumps warm moist air into the Gulf Coast States all summer and brings plenty of rain to the region. Summer thunderstorms are a common occurrence. Tropical cyclones are also steered by the big high pressure system. Sometimes right into the Gulf of Mexico and sometimes around it and out to sea.
Every now and then, the high pressure center will move westward, closer to the mainland and drift north a bit. This brings very hot and dry weather to the region. When the high moves close and drops southward, it gets very wet and stormy.
Dr. Wenhong Li and colleagues found that the Bermuda High is behaving strangely now. It’s getting stronger and moving westward. It’s also drifting North and South more than in the past. They show in their paper that the drought and flood weather over the Southeast is directly related to this.
So, why is this happening?
It could be long term oscillations in the ocean/atmosphere system. These are well known. The Pacific Decadal Oscillation (PDO) could be involved. So could the Atlantic Multidecadal Oscillation (AMO). The PDO and the AMO are long duration changes in ocean temperatures which affect weather patterns. These patterns have been occurring naturally for at least a millennium. Very likely for much, much longer.
It’s not the AMO or the PDO.
Li and his colleagues checked it out and the correlation between them and the Bermuda High movements is very poor. In other words, the behavior of the Bermuda High does not seem to be related to the AMO/PDO.
Could it be climate change?
They compared the behavior of the Bermuda High in the past using the reanalysis data sets and also looked at a series of climate models. They first used 23 models to look at how the NASH behaved when greenhouse gases were set to pre-industrial levels. They saw behavior consistent with the reanalysis prior to 1980.
They then looked at a set of climate models with more realistic modern day levels of carbon dioxide and other greenhouse gases. They found increased correlation. In other words, the Bermuda High starts behaving more like what has been seen since 1980.
They then looked at a set of 23 different models with rising greenhouse gases until the CO2 levels double in the year 2100. It’s very likely this will happen if we continue as we are now.
They found even more correlation with the behavior of the Bermuda High seen in the last 30 years. The average of these future climate models show extreme droughts and rain events over the Southeast as the Bermuda High gets stronger and moves westward.
Here is a quote directly from the paper:
“Our attribution analysis suggests that global warming seems to be contributing to the changes of the NASH.”
It will be interesting to see the reaction to this paper. I already know it will get plenty of press, but I’m interested in what other climate researchers think. Did they overlook anything, make a mistake in the statistical analysis, etc.
If not, then we can say with some confidence that the brutally hot summer of 2010 was indeed at least partially due to climate change. So was that flood in Nashville. So was that drought that almost shut off Atlanta’s water supply in 2007.
The real science is a bit scarier than what you see on cable news isn’t it.
Sources:
NOAA http://www.aoml.noaa.gov/phod/amo_faq.php
Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States
Wenhong Li, Laifang Li, Rong Fu, Yi Deng and Hui Wang
doi: 10.1175/2010JCLI3829.1 (http://journals.ametsoc.org/doi/abs/10.1175/2010JCLI3829.1?journalCode=clim)
Author: | Posted on: 2. November 2010 at 19:13 pm | Filed under: Climate, Climate Change, Global Warming, Science, Weather News | 0 Comments
The Wild Wild Science Journal is now part of the new AGU Blogosphere!
I have some very smart and fascinating company- please check it out!
Devin Bowling took this shot (in Albertville, Al.) of a wall cloud (upper left). A tail cloud is the center, pointing toward the rain. Tail clouds are often mistaken for tornadoes.
As forecasters expected, violent storms tracked across Alabama and Tennessee on Tuesday. Tornadoes then hit South Carolina in the early morning hours of Wednesday. I was on air for nearly 8 hours straight. My voice is yet to recover.
Wall clouds are the parent clouds of a tornado. Not every wall cloud will produce a twister but if you see one, go the other way. Fast. Better yet, get under something sturdy. DO NOT head for a nearby overpass. Winds are accelerated under them and taking shelter under one can be a deadly mistake.
On the Great Lakes, it was the second strongest storm on record. Winds gusted to 80 mph. The waves on Lake Superior reached 9 meters!! (For the metrically challenged that’s over 26 feet!!)
The pressure at the center of the storm dropped to 955.2 millibars. That’s the lowest pressure ever recorded in Minnesota. Only the storm of January 1978 was stronger.
The 1978 storm is referred to as the great Ohio Blizzard. The pressure dropped to an incredible 950 millibars in that storm. Almost everyone older than 35 in Ohio can tell you stories of that event.
The Great Lakes Storm on Tuesday. It passed over Duluth and now holds the record for the lowest pressure ever recorded in Minnesota. Image courtesy NWS Duluth.
The storm in 5th place is rather famous. On November 10, 1975, (thirty-five years ago next month) a surprise storm produced a low pressure of 980 millibars. That storm hit Lake Superior hard and resulted in the sinking of an iron ore carrier called the Edmund Fitzgerald.
Canadian Gordon Lightfoot made the gale famous by his song about the doomed freighter. One line in particular has stayed with me.
“Does anyone know where the love of God goes, when the waves turn the minutes to hours.”
Update Oct. 29,2010: It now appears that the Minnesota storm missed the the non tropical storm record for the mainland U.S. by 0.01 inches of mercury!
Author: | Posted on: 27. October 2010 at 20:16 pm | Filed under: History, Science, Severe Weather, Weather, Weather News | 1 Comment
Numerical weather prediction model forecast valid at 8 PM U.S. East Coast time Tuesday. This storm will spread tornadoes across the U.S. Midwest and near hurricane force winds on the Great Lakes.
When most folks think of tornadoes they imagine a warm spring afternoon suddenly turning stormy. More often than not this is true but there are glaring exceptions. Last night was one and Tuesday will be another.
A powerful storm system has been winding up in the Plains. Last night a band of storms from Texas to Alabama brought tornadoes and large hail. Here in North Alabama, I was up for much of the night watching radar.
Winds going toward the radar right next to winds going away from the radar. This is what a tornado looks like on a Doppler radar. Image from Penn. State NEXRAD Archive. Click for larger version.
Large super-cell tornadoes are the easiest to spot and we had only one of those up in Tennessee. The ones you have to really watch for are the smaller more short lived twisters that are embedded in a squall line.
Around 4 AM CDT Monday morning, the Doppler radars indicated a strong circulation in the line over NE Alabama. The little town of Ider, near Fort Payne, was struck with a twister around 4:15.
The tornado looks to be an EF-1 or perhaps briefly an EF-2. An EF-1 tornado has winds of 32-50 meters per second (73-113 mph). That’s the equivalent of up to a category two hurricane on the Saffir-Simpson scale.
The Storm Prediction Center (SPC) in Norman Oklahoma issues the tornado watches for all of the U.S. They’ve notified Meteorologists like myself and at the local NWS forecast offices that they believe there is a rare “high risk” of tornadoes over Indiana and Ohio on Tuesday. A high risk is rare anytime.
It’s exceedingly rare in autumn.
SPC does only one thing. Forecast severe weather. Meteorologists like myself give high credibility to their forecasts.
The Enhanced Fujita Scale- courtesy of the Storm Prediction Center (NOAA)
There’s been an amazing technological revolution in forecasting over the last 30 years. In the 1970′s most tornado watches had no reports of tornadoes. Now it is rare for a watch not to verify.
When I was an undergrad meteorology student, I worked on a project at Okla. University in 1980 called SESAME. That stands for Severe Environmental Storms and Mesoscale Experiment. It was a fancy name for trying to correlate what severe storms were doing with what the new Doppler radars were indicating.
I remember being laughed at by people who called it a waste of money. It was anything but.
Doppler radars cover most of the nation now and make it possible for forecasters to give incredibly accurate warnings. An accuaracy I could not have imagined back in 1980.
At 4:15am Monday, the Doppler radar here in North Alabama showed a srong rotation and a tornado warning was issued. We had it on the air in less than 15 seconds from the time the NWS pushed the button. Unfortunately, most people in the little town of Ider were asleep.
The ones who has NOAA weather radios were awake because a loud alarm had gone off. If you live in area where severe weather is likely, you should have one. They only cost about 30$.
It might save your life one night.
You cannot imagine how frustrating it is to break into programming and give a warning while knowing that most people are asleep and will never hear it.
Until it’s too late that is.
Be safe,
Dan
Author: | Posted on: 26. October 2010 at 00:59 am | Filed under: Forecasting, Radar, Science, Severe Weather, Weather, Weather News | 1 Comment
