Posts Tagged storm surge

Crossing the Red Sea? Not at Aqaba, Nuweiba, or Tiran

My latest scientific paper is an ocean modeling study that examines the influence of wind direction on storm surge. This particular question grew out of an embarrassing mistake I made during my first semester of graduate school at the University of Colorado. The full citation is:

Drews, Carl (2015) Directional Storm Surge in Enclosed Seas: The Red Sea, the Adriatic, and Venice. Journal of Marine Science and Engineering 3(2), 356-367. doi:10.3390/jmse3020356

The Adriatic case study looked at winds blowing toward the city of Venice, Italy. I calculated a maximum surge of 2.02 meters when winds are blowing from 320° Cartesian; this result agrees with the historical maximum surge of 1.94 meters recorded on November 4, 1966.

Why not the Gulf of Aqaba?

The Red Sea case study examined the wind-driven storm surge and wind setdown in the northern reaches of the Red Sea. The COAWST/ROMS ocean model shows that although sea levels at Suez can drop to 1.72 meters below sea level (without tides), the Gulf of Aqaba is too deep to generate significant storm surge or wind setdown. The sea level at Aqaba changes by only ±5 centimeters, with even smaller variation at Nuweiba and the Straits of Tiran (JMSE Figure 8).

5 centimeters is not enough provide a dry passage for Moses and the Israelites through the Red Sea, nor is it enough water to drown Pharaoh’s chariot army when the wind ceases and the waters return. For more detailed information on why the Aqaba crossings won’t work, please see my longer article at Crossing the Red Sea at Aqaba? No.

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Saving Lives With Ocean Models

The orphans were tied together for their safety. Their teacher had attached all the children with lengths of rope, tied securely around their waists, as the storm approached Galveston and the waters began to rise. And that is how the rescuers uncovered their lifeless bodies, by following the rope from one drowned child to another.

Erik Larson relates the tragedy of the Galveston orphans in his 2000 book Isaac’s Storm. A total of ~9,000 souls perished in that 1900 disaster. In 2005 a similar tragedy befell New Orleans, as Hurricane Katrina swept into the Louisiana delta and drove Lake Pontchartrain over the levees into downtown New Orleans. 1,833 people lost their lives, and at $108 billion Hurricane Katrina represented the largest monetary loss in U.S. history due to natural causes.

These human tragedies don’t have to be repeated.

I’m an ocean modeler at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. This is my personal blog at with my own views. I use computer simulation to study hurricane-driven storm surge. I can send a Category 5 hurricane into New York, or Miami, or even Buffalo, New York. I can watch an advancing wall of water obliterate downtown Tokyo from the comfort of my office, all without anyone else getting wet. To do this, I construct a digital model of the coast and I blast it with 150-km/hr winds. A supercomputer calculates the hourly rise in sea level as the storm waters inundate populated areas. I can verify my calculations with past events, and evaluate the risk posed by future hurricanes.

Figure 11. Directional analysis at New York Harbor (experiment NY7).

Figure 11 of Drews C, Galarneau TJ Jr (2015) Directional Analysis of the Storm Surge from Hurricane Sandy 2012, with Applications to Charleston, New Orleans, and the Philippines. PLoS ONE 10(3): e0122113. doi: 10.1371/journal.pone.0122113

Grid cells in the ocean model are wet or dry. Grid cells containing water are colored blue for the sea; grid cells on land are colored green for vegetation. When the ocean rises and floods formerly dry cells (storm surge), I color them red. I use yellow when a normally wet cell becomes dry (wind setdown).

Just four colors: blue, green, red, and yellow. The ocean model runs and the grid cells change color. That’s all. It’s just a numerical model. But I also realize: People live in those grid cells. Every cell is home to businesswomen, teenagers, hourly laborers, little babies, and retired couples. The grids on my computer screen are filled with living, breathing, working, laughing people. Every grid cell matters. When I see a set of green cells along the coast turn red, I know the human cost. I have joined flood cleanup efforts and seen the destruction. I think about how to prevent the next disaster, how to warn these communities, and how to get them out of harm’s way.

If you live in a coastal area, you should know that supercomputers are even now running and calculating to protect your life and property. Researchers are developing coastal models to evaluate your risk and your evacuation plans. At NCAR, NOAA, and the National Hurricane Center, projects are underway to forecast hurricane-driven storm surge. Today you can view your city’s risk at Hopefully someday you will be able to click on a Google Earth plot of your own house and show the hourly surge forecast as the storm approaches.

Other hurricanes will surely come. Typhoons will pound the coasts of the Philippines, Taiwan, and Japan. We are determined that there will never be another Galveston 1900, that the human tragedy of New Orleans 2005 will never happen again. With accurate and timely forecasts, we are working to ensure that next time people won’t be in the way when the big waves come ashore.

Carl Drews, author of Between Migdol and the Sea: Crossing the Red Sea with Faith and Science.

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Lake Erie Is My Laboratory

I recently published another scientific paper in the peer-reviewed journal PLoS ONE. Since PLoS ONE is Open Access, anyone can read the paper without a journal subscription:

Using Wind Setdown and Storm Surge on Lake Erie to Calibrate the Air-Sea Drag Coefficient

The publication date was August 19, 2013. Here is the full citation:
Drews C (2013) Using Wind Setdown and Storm Surge on Lake Erie to Calibrate the Air-Sea Drag Coefficient. PLoS ONE 8(8): e72510. doi:10.1371/journal.pone.0072510

The purpose of the research was to validate the results of the COAWST ocean model (Coupled-Ocean-Atmosphere-Wave- Sediment Transport Modeling System) with actual observations of storm surge. The paper has a lot of figures that we call “spaghetti plots;” these are charts that show multiple time series on a single plot. We call them spaghetti plots because they look like a bunch of noodles stretched from left to right across the page:

Figure 11. December 2006: Wind setdown and storm surge, with experiments E4, E18, E21, and E23. From Drews (2013).

Figure 11. December 2006: Wind setdown and storm surge, with experiments E4, E18, E21, and E23. From Drews (2013).

In Figure 11, the black line represents the observations of water level taken at the Fermi power plant at the western end of the lake, and at Buffalo at the eastern end of the lake. The colored lines represent various model runs. The goal here is to get the colored lines to match the black line as closely as possible. This is done by adjusting the COAWST model parameters in a sensible manner. Adjustments include: the numerical formula for the air-sea drag coefficient, the bottom drag coefficient, the influence of waves, and the algorithm used to simulate wave action, and the presence of ice on the lake.

Why Lake ErieLake Erie happens to be a near-perfect natural laboratory for conducting this kind of experiment. The lake is long, shallow, and subject to strong winds from the west that cause the lake water to slosh back and forth like a big bathtub. Since the lake is surrounded by populated areas in the United States and Canada, there are many weather stations along the coastline that provide archived meteorological data. Lake Erie is also an important seaway for international commerce, and NOAA provides accurate measurements of tides and currents at major ports on the lake. I can run simulation experiments with confidence in the observations that I am trying to match.

The paper describes two windstorms on Lake Erie: December 1–2, 2006 and January 30–31, 2008. Lake Erie is 400 km long and 90 km wide. Since I don’t have a gigantic fan big enough to blow the lake water around and measure what happens, I have to wait for nature to do the blowing instead. Fortunately for me, these windstorms occur often enough to provide several usable data sets. Better yet, there were no human fatalities in either of these storms.

The potential result of the research is a more accurate model for storm surge. When building coastal defenses such as floodwalls, it is crucial to know how high the ocean will rise when the next hurricane comes ashore. The difference between building a seawall one foot higher than the maximum surge, and one foot lower than the maximum surge, can be disastrous.

Moses Crossing the Red Sea

In 2010 I published another paper on wind setdown and storm surge:
Dynamics of Wind Setdown at Suez and the Eastern Nile Delta

That earlier paper reported the emergence of a land bridge in the eastern Nile delta under certain conditions of wind speed and direction. For readers of funmurphys who are interested in Moses crossing the Red Sea, the ocean model indicated that Moses would have 4 hours to lead the Israelites across the yam suf.

At the time, I suspected that the estimate of 4.0 hours was somewhat conservative; that is, the dry passage probably would have stayed open for a longer period of time. There were several factors that we did not include in the 2010 research, such as waves and a drag coefficient more suited to coastal conditions. I had a hunch that these additional factors would increase the duration of the passage. However, the rigorous nature of scientific publishing requires that scientists cannot publish more than a few paragraphs of speculation; peer-reviewed journals require concrete results supported by evidence from observations and computer models.

The Lake Erie research provided a chance for me to test my earlier hunch. I was pleased to find that my hunch was correct; but better yet, that I could provide a revised number for the crossing time. Here it is: Moses had over 8 hours to evacuate all the Israelites from Pi-Hahiroth to safety at Tell Kedua on the other side of the yam suf. Or, for scholars who are more interested in the wind speed, an east wind blowing at 24 meters per second is sufficient to hold open the dry passage for 4 hours (the 2010 paper reported 28 m/s).

Figure 13. Corrections applied to the Lake of Tanis and the Kedua Gap. From Drews (2013).

Figure 13. Corrections applied to the Lake of Tanis and the Kedua Gap. From Drews (2013).

I like this result, because it shows that there is some engineering tolerance to the solution. Although God can of course do anything He wants to do, as an engineer I am happier with a answer in which the parameters can vary a bit and still work. The 2013 paper demonstrates that the Kedua Gap is a more robust reconstruction of Exodus 14 than originally thought.

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Crossing the Red Sea with Moses and Open Access

Yesterday the scientific journal PLoS ONE published my article “Dynamics of Wind Setdown at Suez and the Eastern Nile Delta”. This publication represents a portion of my Master’s thesis, which was announced here last year. We now present this research in a peer-reviewed journal. Here is the paper’s Abstract:

Wind setdown is the drop in water level caused by wind stress acting on the surface of a body of water for an extended period of time. As the wind blows, water recedes from the upwind shore and exposes terrain that was formerly underwater. Previous researchers have suggested wind setdown as a possible hydrodynamic explanation for Moses crossing the Red Sea, as described in Exodus 14.

Since the paper is about dynamics instead of biblical history, the contents focus on fluid mechanics instead of on Moses and the Hebrew refugees. But for those readers who are interested in the Exodus, Point B in Figure 8 is Pi-hahiroth. The famous crossing is from Point B across to Tell Kedua. My Tanis hypothesis suggests where and how Moses crossed the yam suf. When remains a thorny issue. As with any new hypothesis, scholars from many disciplines will have to consider the proposal from all angles (history, linguistics, military science, archaeology, meteorology, refugee movement, sociology, oceanography, etc.).

What Open Access means for me

PLoS ONE is an Open Access journal, meaning in a general sense that access to the publications is not restricted. You don’t have to pay a download fee or a subscription fee to download and read the articles. It’s free Free FREE! For what Open Access means for the world of science at large, Google for the term and do some reading. Go ahead and peruse some of the debates. I’ll describe here what it means for me.

It means that my co-author and I paid a publication fee to cover the cost of reviewing and preparing the document for on-line publication. Some journals (Open Access or not) are free to publish in, and others require certain page charges. PLoS ONE follows the “author pays” model.

The “Dynamics of Wind Setdown” article is of general interest. I want oceanographers to read it, I want journalists to read it, I want high school students to read it. I want teachers, gardeners, Norwegians, mechanics, historians, kids, pastors, marketing directors, software engineers, physicists, Australians, poor people, airline pilots, retired people, shepherds, and checkout clerks to read it. I want you to read about the parting of the Red Sea. Skip right to Figure 8 if you want! I don’t want any barriers to readership. I want the paper’s exposure to be as wide as possible. And I can achieve that goal by opening up access.

Peer-reviewed articles are read by scholars, who cite previous research when they publish a subsequent study. The citation count is a measure of the impact of a paper – the importance that a paper has on its field. Open Access papers are supposed to have higher citation counts, so this publishing model will presumably be better for my career.

What Open Access means for you

Open Access means that you can make use of the material that we published. The content at PLoS ONE is licensed under a Creative Commons Attribution License. This means that you can use the article in ways described by the license, so long as you properly cite the authors and the journal. The idea behind the CCA license is that scholars’ work should be used and extended, with due credit given to the original publication. You don’t have to get our written permission. Please refer to the Creative Commons web site for further information.

Open Access means that you don’t have to pay $30 or even $15 to download the paper and read it. Your institution or library doesn’t have to pay thousands of dollar$ in subscription fees to get the document. You just have to click. That’s right, you simply have to click on this link. What are you waiting for? Click! Download and read it now!

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Academic and Choral Achievement

Here is an update since Kevin updated the blogging software. In May 2009 I graduated from the University of Colorado at Boulder with a Master’s degree in Atmospheric and Oceanic Sciences. Wow, five years is a long time! There were quite a few speeches during the graduation ceremony, but I didn’t mind a bit! It took a lot of work to get to that ceremony, and I just sat there in the sunshine with my Master’s robe and mortarboard cap and drank it all in. John Roberts (a CNN correspondent) gave an inspiring address about making your dreams come true. When you come up against a wall, this is your opportunity to show the world how much you want something. If you want your goal bad enough, you will go over, under, around, or through the wall to reach your goal! I feel that I have so much potential, and opportunity, and rich possibilities ahead of me. I don’t ever want to lose that feeling. My sister and family came to see the graduation. Maybe someday when my kids get frustrated with school and homework and term papers and exams they will remember the bagpipes and the funny academic gowns and their Daddy graduating and they will understand that it’s all worthwhile.

Kevin, I don’t know if you wrote a thesis when you got your Master’s degree from Stanford University, or if the co-terminal program had some other option. I wrote a 110-page thesis describing my research and model results:

Title: Application of Storm Surge Modeling to Moses’ Crossing of the Red Sea; and to Manila Bay, the Philippines

Storm surge occurs in low-lying coastal areas when strong winds blow the sea surface up onto the land. The resulting inundation can pose a great danger to lives and property. This study uses an Ocean General Circulation Model and the results from a mesoscale atmospheric model to simulate storm surge and wind setdown. Two case studies are presented. A reconstruction of the crossing of the Red Sea by Moses and the Israelites, as described in Exodus 14, shows that the eastern Nile delta of Egypt matches the Biblical narrative and provides a hydrodynamic mechanism for water to remain on both sides of the dry passage. The vulnerability of Manila Bay and the surrounding areas to a Category 3 typhoon is evaluated and shows that the simulated surge heights depend heavily on the wind direction and the coastal topography.

The thesis document is published electronically by ProQuest, and anyone can download the PDF for a fee and read it. I classified the thesis under Biblical studies in addition to Physical oceanography and Atmospheric sciences. It would be cool to hear a little bell every time someone reads my thesis, but scientific publishing has not reached that stage yet.

I also made the national news for having sung in the Boulder Messiah Sing-Along for 17 consecutive years now. On November 3, 2009 the Associated Press published a news story on Messiah Sing-Along events, featuring the Boulder Messiah Chorale and Orchestra. Hallelujah for Handel’s ‘Messiah’ is by reporter Ann Levin. I am the Enthusiastic Choir Member in the story. If that link ever ceases to work, you can Google for: “Carl Drews” Messiah. Nobody has recognized me on the street yet (“Hey, you’re that Messiah choir dude!”), but it is nice to see that our sound is gone out into all lands, at least electronically.

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