Hurricane Moderation

Hurricane Moderation

By Stephen Salter

The formation of a hurricane depends on many factors, including atmospheric water vapour, distance from the equator and the recent history of wind patterns. But an essential requirement is a high sea surface temperature. To get from a tropical storm to the lowest category of hurricane requires a temperature of 26.5°C. We can moderate hurricanes, or even prevent them, by reducing water temperature.

A useful start to any engineering project is the estimation of all the energy flows. One cubic metre of air at a temperature of 30°C can hold about 30 grams of water vapour. The energy to evaporate this is about the same as in 13 grams of TNT, enough for a nasty anti-personnel mine. A cubic kilometre of such air contains the same energy as the Hiroshima bomb. Hurricanes can be hundreds of kilometres in diameter and so contain tens of thousands of Hiroshimas. If you have read this far you will know about the billions of lost dollars and thousands of deaths from this amount of energy.

Most of the hurricanes that reach America (with the exception of Harvey), start on the African side of the Atlantic near Cape Verde and grow as they move west. We can use Google Earth to measure the hurricane breeding area. The US National Weather Service gives a warm water depth of 45 metres. To cool this volume by 2°C in 200 days needs more than 600 times the mean US electricity power generation. If you want to moderate a hurricane tomorrow, today is much too late. You should have started last November.

All this heat has come from the sun. Some could be reflected back out to space by clouds. The reflectivity of clouds was studied by Sean Twomey. He flew over many clouds, scooped samples and measured the solar energy reflected from their tops. He showed that reflectivity depends on the size distribution of drops. Lots of small drops reflect more than the same amount of liquid water in fewer, larger ones. In typical conditions, doubling the cloud drop number increases reflectivity by a bit over 0.05.

Making cloud drops needs a high humidity but also some kind of ‘seed’ called a condensation nucleus on which to start growth. There are thousands of condensation nuclei per cubic centimetre of air over land but fewer in air over mid ocean, often less than 50. John Latham suggested that the salt residues left from the evaporation of a spray of sub-micron drops of sea water would be excellent condensation nuclei. They would be moved from the sea surface by turbulence to produce a fairly even distribution upwards through the marine boundary layer to where clouds form.

The condensation nuclei could be produced by wind-driven sailing vessels cruising along the hurricane breeding areas getting energy from their motion through the water. We can make spray by pumping water through very small nozzles etched in the silicon wafers used for making microchips. The main technical problem is that sea water is full of plankton much larger than nozzles. This can be filtered using ultra-filtration technology with back-flushing, originally developed for removing polio viruses from drinking water. Each vessel would produce 0.8 micron diameter drops at 1017 a second.

[ part-image from larger Wikipedia map ]
Spray operations would depend on the pattern of sea surface temperatures as measured by satellites. We want the trajectory of temperature rises through the year from November to the following July to be those that an international panel of meteorologists think will give a desirable rainfall pattern from ‘gentle’ tropical storms.

Most ships are made in quite small numbers. An exception was the Flower class corvettes built for the Royal Navy during World War II. If we index-link the 1940 cost to today we can predict that in mass production each spray vessel would cost $4 million. With assumptions which have not yet been rejected by hurricane experts, we think that controlling the Atlantic hurricane breeding paths would need about 100 vessels. With typical ship lifetime the annual ownership and maintenance cost would be about $40 million. If these figures and recent estimates of the cost of hurricane damage are correct the benefit-to-cost ratio is quite attractive.

Because of official UK Government policy updated in May 2018 the project is privately funded.

Marine cloud brightening | Prof. Stephen Salter | TEDx Talks Published 15 Nov 2016

Rising temperatures are increasing the amount of water vapor in the atmosphere at a rate of 7% more water vapor for every 1°C warming. This is further speeding up warming, since water vapor is a potent greenhouse gas. Over the coming years, a huge amount of additional water vapor threatens to enter the atmosphere, due to the warming caused by albedo changes in the Arctic, methane releases from the seafloor, etc., as described at this page.

The situation is dire and calls for comprehensive and effective action, as described at the Climate Plan.

Added below is a box from an earlier post with hurricane damage mitigation proposals.

Hurricane Damage Mitigation

A 2014 study by scientists led by Mark Jacobson calculates that large turbine arrays (300+ GW installed capacity) could diminish peak near-surface hurricane wind speeds by 25–41 m/s−1 (56–92 mph) and storm surge by 6–79% AND provide year-round clean and renewable electricity.

How many electric cars will be ready to move into Miami to provide emergency support in the wake of Hurricane Irma?

Storms can cause power outages, electricity poles can get damaged. Electricity poles can also be a traffic hazard (i.e. collisions can occur even if the pole hasn't fallen down, especially when streetlights fail). When damaged, power lines hanging off poles constitute electrical shock hazards and they can cause fires to ignite and wildfires to start.

Storms can also cause damage to backup generators and to fuel storage tanks, making it hard for emergency services to give the necessary support. Electric cars can supply electricity where needed, e.g. to power necessary air conditioning, autoclave and emergency equipment, such as in hospitals. After a tsunami hit Japan in 2011, electric cars moved in to provide electricity from their batteries, as described in many articles such as this one.

Wind turbines and solar panels are pretty robust. Hurricane Harvey hit the Papalote Creek Wind Farm near Corpus Christi, Texas. The wind farm had little or no damage, there was just a short delay in restarting, mostly due to damage to power lines. The Tesla roof that doubles as solar panels is much stronger than standard roofs. Have a look at this video.

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Clean and renewable energy can provide more stable, robust and safe electricity in many ways. Centralized power plants are vulnerable, in that all eggs are in one basket, while there can be long supply and delivery lines. Many of the benefits of clean and renewable energy are mentioned on above image.

Furthermore, there are ways to lower sea surface temperatures. The image on the right shows the very high sea surface temperature anomalies on August 28, 2017.

Note the colder area (blue) in the Gulf of Mexico. Hurricane Harvey cooled the sea surface as water evaporated and warm moisture was added to the atmosphere. The cyclonic force also mixed colder water below the surface with warmer water at the surface, resulting in colder water at the surface. The combination image below shows the difference between August 20, 2017, and August 30, 2017.

[ click on images to enlarge ]

A number of geoengineering methods can be used to reduce sea surface temperatures and thus reduce the intensity of hurricanes. Methods include upwelling associated with ocean fertilization and with ocean tunnels, marine cloud brightening and increasing and brightening bubbles in the wake of vessels, as discussed at the geoengineering group at facebook.

Besides cooling the sea surface, there's also the upwelling of nutrients that can help combat ocean stratification. Warm water holds less oxygen than cold water. As the water warms, it also tends to form a layer at the surface that does not mix well with cooler, nutrient-rich water below, depriving phytoplankton of some of the nutrients needed in order for phytoplankton to grow (and take up carbon).

Some of these methods are also discussed at this 2011 page, which also mentions that more research is needed into the impact of such methods. Of course, possible application should go hand in hand with dramatic reductions in emissions including a rapid shift to 100% clean and renewable energy.

thesolutionsproject.org
Similarly, the necessary shift to clean and renewable energy in itself will not be enough to avoid catastrophic warming, and it should go hand in hand with further lines of action to remove pollution and to cool the Arctic Ocean, as described at the Climate Plan.