The Earth Story

Hurricane Harvey fed off record warm Gulf of Mexico waters

This satellite shot captures Hurricane Harvey at the time it was a category 4 storm, just before it made landfall in Texas. The storm started off as a disturbance crossing the Yucatan Peninsula, but when it made it into the warm waters of the Gulf of Mexico it rapidly strengthened. Harvey became the second costliest disaster ever to hit the United States after it doused the city of Houston with record rainfall totals. A new analysis points squarely at the Gulf of Mexico as the main driving force behind the power of this storm.

Hurricanes feed off of warm temperatures in ocean waters. In the process, they remove heat from the ocean and leave the water behind it cooled off. However, other things can happen that affect ocean temperatures; for example, the winds blowing over the water could mix the shallow layer with deeper water, cooling the surface water by pushing the warm water deeper. As a consequence, it’s not easy for scientists to match up the energy of the storm with the energy of the ocean.

Harvey though represented a unique case. For much of the surrounding month it was the only major weather event in the Gulf of Mexico, and it traveled over areas that are well instrumented so that scientists could see how much heat it removed from the water. On top of that, scientists also have available the Global Precipitation Measurement Satellite system, which enabled estimates of Harvey’s rainfall over wide areas.

A team led by a scientist at the National Center for Atmospheric Research took these two measurements and converted them into total energy. The ocean cooled by a certain amount over a certain volume – that’s an energy measurement. Harvey produced a certain amount of rainfall over a certain area – that’s also an energy measurement. When they compared the number of joules pulled out of the Gulf to the energy released over land by Harvey – they were virtually identical, within 1% of each other. The energy that drove Harvey was the energy in the Gulf; basically every Joule of energy it pulled out of the Gulf, it dumped on Texas.

Harvey became such a disaster because it had an ample supply of energy in the shallow waters of the Gulf of Mexico. Prior to the storm, the waters of the Gulf were at their hottest temperature ever recorded, more than 1.5°C above the long term average. Those temperatures extended downwards, making the Gulf heat content also a record. When Harvey passed over these waters, it cooled them by 2°C. That extra 1.5°C in the Gulf of Mexico in 2017 was enough to almost entirely fuel the storm; had the Gulf not been at record temperatures, Harvey would not have had the energy to produce that rainfall.

Global ocean heat content has been rising steadily since the 1980s as the ocean takes up much of the extra heat kept in the atmosphere by greenhouse gases. The close match between energy taken out of the ocean and energy dumped by the storm verifies that the extra energy trapped in the atmosphere is feeding storms like Harvey. The extra heat in the Gulf of Mexico directly triggered flooding in Houston, and as ocean temperatures continue to increase, it will be able to continue powering devastating storms.

-JBB

Image credit: https://commons.wikimedia.org/wiki/File:Harvey_2017-08-26_0055Z.jpg

Original paper: https://doi.org/10.1029/2018EF000825

How many Harveys?

Houston, Texas is a flood-prone city. The city sits on a flat coastal plain where one river, known as the Buffalo Bayou, spreads out into an estuary to reach Galveston Bay. The city has grown into the 4th largest in the United States, and now encompasses several other large streams. The combination of a coastal plain, with little slope to drive water downhill, and exposure to the Gulf of Mexico, makes it a natural place for flooding. The city has seen 3 major floods in the past 3 years alone, but Hurricane Harvey topped them all.

Harvey started its voyage over unusually warm waters in the Gulf of Mexico. In fact, because of the heat in the Gulf this year Houston and Galveston are both expected to have their hottest years ever recorded. The storm sucked up this energy and moisture from the Gulf, but then it ran into a weather system that locked it in place for several days. It dumped the largest rainfall totals ever recorded in the United States on some portions of the Houston area.

The “largest rainfall totals ever recorded” seems like a true extreme. Local officials called the storm a “Biblical” rainfall; that would mean that Harvey was something we couldn’t have prepared for and might never have to prepare for again. However, new research just published by scientists from MIT suggests that Harvey is just the beginning.

Dr. Kerry Emanuel has previously developed a model that simulates the effects of hurricanes. Hurricanes are complicated, turbulent beasts and simulating processes in them requires a huge amount of computer time, but his model instead focuses on the results. Using input parameters such as water temperature, wind conditions, and atmospheric parameters, the simulation produces low-pressure systems that sometimes intensify into hurricanes. This simulation setup allows them to produce a large number of storms and then compare their actual statistical distribution to the ones observed in the real world.

Their hurricane model is able to accurately match the observed rate of occurrence hurricanes that struck Texas in the period 1900-2000. Given those historical statistics, over the period 1980-2000a rainfall event the size of Harvey has a 1 in 100 chance of occurring somewhere in the state of Texas. Taking into account the odds of it hitting a specific location such as Houston, the city of Houston could expect to see a comparable storm once every 2000 years.

However, the weather is no longer what it once was and the statistics for 1900 aren’t even valid today. The Gulf of Mexico is warmer than it was 100 years ago; that is showing up in Houston’s daily temperatures and it showed up in Harvey’s rainfall totals. The scientists took estimates for CO2 contents in the atmosphere for the period 2080-2100 from one of the scenarios in the IPCC report where there is little to no limitation of CO2 release and asked what that would do to storms like Harvey.

Under those conditions, the planet is warmer, the Gulf is warmer, and there is more water to feed strong storms. Under those conditions, a storm dumping as much rain as Harvey dumped on Houston will hit Texas once every 5.5 years, and will hit Houston directly once every 16 years. Not only will Harvey-level storms become more likely, but also storms several times larger than Harvey, storms that are basically impossible today, will be the new “100 year storms” by the turn of the 22nd century.

Right now, humans already don’t have the climate of the year 1980. We’ve added a lot more heat to this planet. The scientists also gave a general estimate of where we are right now and said that a Harvey level of storm has probably gone from about a 1 in 100 year event in the state of Texas as a whole to a 1 in 20 year event due to CO2 increases since 1980.

In other words, as of right now, Harvey level storms are possible in Texas in the next decade. In the latter half of the 20th century, unless we change our current emissions path, Harvey level storms will be happening every decade in the state of Texas. Hurricane Harvey did an estimated $200 billion or so worth of damage to the Houston area. Under those conditions, downtown Houston basically becomes uninhabitable – by the time recovery is finished from one storm, the next storm is a year or two away.

-JBB

Image source: CNN http://cnn.it/2wG4HaD

Original paper: http://bit.ly/2hrtgPe

Press release: http://bit.ly/2zJqzBd_ _

Waugh Bridge Bats

After Hurricane Harvey dumped record-breaking amounts of rain on the city of Houston, Texas, there was a huge amount of standing water in the city and surrounding area. A handful of residents have come down with diseases due to exposure to the water, including one known death due to a flesh-eating bacterial infection.

However, despite standing water throughout the city, there weren’t widespread reports of people coming down with diseases due to mosquito bites – at least not a huge surge compared to normal years. For that, you can possibly thank these critters – the Waugh Bridge Bats.

Bats inhabit several large caves in Texas, and since humans began constructing sheltered sites in cities bat colonies have moved into housing beneath bridges in several major cities including Houston and Austin. This photo from the Houston Chronicle captures the bat colony leaving the Waugh Bridge for the night. Bats can reportedly consume up to 2/3 their body weight in insects, including mosquitoes, during an evening out, and therefore they definitely help as mosquito control when there is a major flooding like that hurricane. In fact, this bridge even flooded during the storm, sending the bat colony out for safety – it’s back now.

Unfortunately, the bats of Texas have one new worry – White Nose Syndrome. White Nose Syndrome is a disease that starts showing up with a white fungus growing on the nose of bats. It has killed millions of bats in the United States since it was first discovered in 2007. It has reached 30 states, and in some cases the mortality rate has been more than 90%. Texas is home to some of the largest bat colonies in the United States, and the disease was just detected in that state for the first time.

-JBB

Image credit: Houston Chronicle/Kathy Adams Clark (Used for non-profit/outreach) http://bit.ly/2z2XlN0

References: http://bit.ly/2iPCwk4 http://www.houstontx.gov/parks/bats.html

Hurricane Harvey

With winds reaching upwards of 130-140 mph (209-225 kph), Hurricane Harvey made landfall along the Texas coast between Port Aransas and Port O'Conner late on Friday night. The storm has stalled over the state, causing devastating flooding, especially in the southeastern areas, which fall on the "dirty side" of the storm's rotation. Residents who safely sheltered in place during the worst of the storm itself are now evacuating their homes as river levees threaten to give way and water is released from dams to relieve pressure.

Houston, my former hometown, is experiencing never-before-seen devastation, with flood waters in some cases reaching the signs above the freeways. Austin and the Hill Country are under flash flood advisories.

Rain is supposed to continue the rest of the week. Current reports from NASA show the storm moving back into the Gulf of Mexico. Although it no longer has an organized center, the storm may well strengthen over the warm waters of the Gulf, with possible winds of 45 mph (72 kph).

As I wait to hear that my sister and her husband have safely reached a shelter away from the threat of the levee on the Brazos river being breached, I ask you to please keep Texas in your thoughts.

CW

Image:

http://bit.ly/2vtElol

Sources:

https://go.nasa.gov/2vyeJa0

http://bit.ly/2vtElol

This is a perfect illustration of the eclipse view we had in Texas yesterday - watch for the “Lens flare” or reflection about half way through this in the center of the frame, the sun crops out for just a second and you get the shape.

The Golden Dragon. A wonderful piece of native gold on quartz from California, it now graces the Houston Museum of Natural Science collection. Loz Image credit: Houston Museum of Natural Science

This happened to a person at my University and I’m not ok with this so I’m publicizing it. Visiting Scholar at Texas A&M "Mistakenly detained" at IAH, after 12 hours was on the verge of being deported before the University's Law School was able to step in to rescue him. States that the officer that arrested him was "inexperienced". Regularly visits A&M, is a Visting Scholar here, works on memory and traumatic events, has repeatedly given talks about the Vichy government in France and their role in the Holocaust. French citizen, Senior Researcher at the French National Center for Scientific Research, targeted because he was born in Egypt.

NRG from above

In a few hours, the eyes of much of the United States, and a nontrivial part of the world, will focus on the stadium that appears open at the top in this view. What is today NRG stadium sits next to the classic Astrodome, both sitting in the center of Houston, Texas.

It is disturbingly difficult to find details of the ground that sits beneath the buildings of Houston. The land itself is, honestly, somewhat bland. It is perhaps the flattest land you’ll ever see; the city’s skyscrapers are viewable from tens of kilometers around due to the gentle slope of the land. But, if you were to search for “Geology” and “Houston”, you’ll find nothing but a list of available jobs in the oil and gas industries. Home to the headquarters of such behemoths as Shell, Schlumberger, Exxon, Houston Texas is the center of employment for the oil and gas industries in the United States, and scientists based in Houston travel around the entire world to survey the geology of more interesting or profitable sites.

Houston sits on the Texas Coastal Plain, what would, if geoscientists really looked at it, be a complicated set of river deltas and coastal plain sediments deposited over millions of years. About a dozen major river systems cross this land today, migrating from side to side as rivers regularly do. These systems carry sediments eroded upstream, including from the highlands of Central and Western Texas.

During the Triassic and Jurassic, the Gulf of Mexico began forming as Pangaea rifted apart. Much of the Gulf coast is underlain by a thick deposit of salt called the Louann salt (https://tmblr.co/Zyv2Js2AOWwNO) deposited in shallow seas as the supercontinent broke apart. From there, river systems deposited sediments that have built gradually outwards, depositing one layer after another and building the continent outward into the ocean basin. Several fault systems and aquifers sit buried beneath the coastal plain, creating complexity at depth.

The year 2016 featured a historic series of floods hitting the rivers that flow through and around Houston. Rainfall events are calibrated statistically – when rainfall volumes are recorded over years and decades, that allows projection of how often extremely large rain events happen (https://tmblr.co/Zyv2Js1vfiXni). In 2016, two different “100 year storms” hit in the space of a week, triggering huge flooding in April. This was only one in a series of major floods in recent years, weirdly following major drought that hit Texas a few years beforehand. These extremes – major droughts followed by major floods – are consistent with the patterns expected with climate change, where increasingly severe weather events are triggered by the extra energy in the atmosphere.

In 2008, Houston was ravaged by hurricane Ike. The city mostly evacuated beforehand, but the damage and flooding were severe. Houston sits at the tip of a major estuary, an open bay facing the ocean surrounded by Barrier Islands. One of these barrier islands is Galveston Island, which was devastated by a Hurricane in the year 1900. When hurricanes hit at the appropriate spot – basically hitting Galveston Island, the strongest storm surge will be focused into Galveston Bay, just north of that Barrier Island. Galveston Bay leads into other harbors near the city of Houston itself and it is heavily industrialized, with shipping ports for industrial products and major fossil fuel refineries.

Hurricane Ike only brushed this area. A direct impact of an intense Gulf Hurricane could seriously damage these industrial sites, triggering large releases of pollution and knocking billions of dollars of industry offline. On top of that, a series of stored barrels containing dioxin sit on the edge of Galveston bay, contained for now but potentially disturbable by major storms.

Since 2008, Houston has been considering building major flood control systems comparable to those found in Europe today, but no single plan has been agreed on. The most commonly cited plan, known as the “Ike Dike”, involves extending a seawall on Galveston Island to cover much of the bay, Different version of the plan continue to be developed, some of which would extend across much of the bay. Although these plans are available on the books, money has yet to be appropriated to even begin construction, so if Houston were to be hit by a storm more intense than Ike the city would be sitting there with developed plans and little to show for them.

Sunday’s forecast calls for a cloudy day with possibly light rain. The stadium in Houston, now named for NRG energy, has an opening roof, but it is thought that today it might have to stay closed as part of Lady Ga-ga’s performance. We’ll see.

-JBB

Image credit: NASA http://earthobservatory.nasa.gov/IOTD/view.php?id=46945

References: http://bit.ly/2jQ4DL8 http://bit.ly/2kFN2JZ https://pubs.usgs.gov/of/1994/0461/report.pdf http://www.nhnct.org/geology/geo2.html http://www.lib.utexas.edu/geo/balcones_escarpment/pages35-40.html http://bit.ly/2kulMvH http://slate.me/1Zks6D4 http://bit.ly/1GN06ld

Goodnight Texas

This image comes from one of the astronauts on the International Space Station and shows the state of Texas at night.

The major metropolitan areas stand out quite well. The large city in the foreground is Houston, sitting on the shores of the Gulf of Mexico which appears mostly dark. The Interstate-35 corridor is well defined, with San Antonio at the left hand side, followed by Austin, and to the north the Dallas-Fort Worth Metroplex.

The DFW area appears to be getting wet here. There are some clouds over it leaving it fuzzy; this might well be what “a city being rained on at night” looks like from the ISS.

Still further north the cities in Oklahoma can be made out as well.

And I can’t figure out which astronaut to credit for this image because for some reason NASA never specifies in their image releases.

-JBB

Image credit: http://www.nasa.gov/multimedia/imagegallery/image_feature_2540.html

A Bullet for Texas

A private company, Texas Central Partners (TCP), has announced plans to bring the first high-speed rail system to the U.S., with a bullet train connecting Dallas and Houston. Work has already begun on a high-speed rail system in California, linking San Francisco, Los Angeles, and Anaheim, but because it will cover a much greater distance (1288 km or 800 mi.) than the proposed Texas system, it’s original completion date in 2022 has been pushed back until 2025, 3 years after the expected operational date of the Texas train. Part of the delay in the California project is due to the need to drill through earthquake-prone mountains, whereas the Texas train will be across the central plains region of the state.

Currently, the 50,000 Texans traveling more than once a week between the two cities have the choice of a 5 hour drive or a 1 hour flight (not counting the time taken in getting to the airport, through security checks, and to the proper gate). The Japanese train design chosen for the project has been in use between Tokyo and Osaka for more than 50 years, giving it high ranking for safety. In that time period, no crash or fatality has occurred and the company cites a time delay average of less than 1 minute per year. The train would travel at approximately 322 km per hour (200 miles per hour) and would carry 400 passengers at a time across the 385 km (239 mi) distance. The expected travel time would be 90 minutes, with a train leaving every 30 minutes during peak travel times.

Regardless of the convenience their rail system will bring, opponents of the California high speed rail system cite that although when completed, the electric train will produce less pollution than the current highway traffic, the construction itself will be done using diesel-powered heavy equipment and make a bad air quality situation (1 in 7 children have been diagnosed with asthma) much worse.

In Texas, Houston alone has 9 out of 10 people (solo drivers plus carpool participants) taking private vehicles to work every day and according to a 2015 report by the American Lung Association, the city ranks 6th out of the top 10 U.S. cities with the worst ozone pollution. (I can personally attest that we had to move out of the Houston area when I developed asthma resulting from air pollution.) So, given the continuing growth of both cities, pulling more cars off of the highways would be a big environmental plus.

In addition to the expectations of reducing air pollution, the proposed high-speed rail system will be elevated when entering urban areas and environmentally sensitive areas such as wetlands, in order to mitigate noise (which TCP says will already be less than current sound levels near highways). Environmental impact studies, led by the Federal Railroad Administration, are still ongoing.

Currently, officials in both Dallas and Houston have embraced the project, however, rural entities opposing construction of the Texas rail system seem more concerned about the probability of eminent domain being used to confiscate land (which is largely agricultural). CW

Image

http://bit.ly/1Uyxz9r

Sources

http://bit.ly/1Uyxz9r

http://www.hsr.ca.gov/

http://bit.ly/1RMNYnZ

http://www.railway-technology.com/projects/california/

http://time.com/3840001/most-polluted-cities-2015/

http://bit.ly/1tyYTuy

http://www.texascentralhighspeedrail.com/page4/index.html

http://bit.ly/1Uf5OEL

http://bit.ly/260V1U6

http://bit.ly/1ZUx0Hp

Houston Floods, again

These two photos show the Brazos River just west of Houston, Texas; the upper was taken in 2013 with the river at normal levels, while the lower image was taken on May 28 of this year. Much of Texas is again facing huge rainfall totals and associated flooding this spring, after having been in a major drought only two years ago.

The Brazos River crested (reached its greatest expected flood depth) on June 2nd, with a depth of 16.71 meters. At that time, the river was more than a meter higher than the previous record flood for this river.

From a geologic perspective, it’s particularly interesting to see how in the lower image the flood outlines classic river features such as abandoned meanders. In fact, if this area wasn’t held together as farmland, it’s entirely possible that a flood this big could cause permanent shifts in the river’s course. Floods often break through levees on meandering rivers and allow the rivers to straighten, but farm owners tend to not be thrilled when that happens because it can cut their fields off on a side of the river that is suddenly much harder to reach.

As the atmosphere warms, it is able to hold more moisture and once consequence is damaging, multi-day rain events like the one hitting this part of Texas. It can be difficult to come up with measurements covering entire states over the past century since not all severe rainfall events were recorded prior to the development of modern radars. However, cities have generally better records and Houston Texas is seeing roughly 167% the number of severe rainfall events it was seeing in the 1950s when atmospheric CO2 levels were lower. Not all cities will see clear increases; some cities will find their atmosphere to be even drier, while others will see their rainfall patterns shift north and south. For now, this part of Texas seems to be in the crosshairs for swinging rapidly between way too little rain and way too much.

-JBB

Image credit: USGS/NASA http://go.nasa.gov/1U338rY

Reference: http://bit.ly/1Sn8s5a

p.s. This isn't just hitting Texas today, France is also dealing with some severe flooding. If I get a good satellite picture of that, there will be another post on their floods.