The Reign of Violent Rain

by Daniel Brouse and Sidd Mukherjee

My interest in sea-level rise and ice sheets collapsing began in the 1990's after I asked Sidd his greatest concerns about human induced climate change. Much of climate change can be reversed or at least stopped from worsening. The collapse of ice sheets is irreversible. Sidd said, "A terrible future awaited." Coastal areas were forecast to be at greatest risk.

By 2020, I had become just as concerned about the rise in sea levels being transported inland. Both the sea and air temperatures are rising. Warm air can hold more moisture than cool air. Warmer sea temperatures result in more evaporation. The increased moisture in the air moves over land causing inland deluges.

In October of 2023 Sidd said, "Now I am thinking the violent rain will be a bigger problem before we die... still thinking it through. In the long run, ya, sea level rise will hit big. If you look at the history, it is episodic, and in the fast bits it can go up 3 feet every twenty years for five hundred years. But, the rain intensity is increasing faster today, and drainage cannot cope, whether in the city or out, culverts and such put in over the last hundred years cannot handle. So, I am paying a lot of attention to terrain and drainage far inland from the seacoast (like Ohio.) By drainage I don't mean just human built. I mean that the natural streams and gullies and ravines have not evolved to a state that can handle the water volumes we see and the worse, larger volumes we will see. So expect huger erosion, steeper slopes to waterways, land collapses and such. Build out your drainage."

Violent Rain
Multiple factors figure into the physics of violent rain. The starting point is the moisture content of air. The Earth is warming. Warm air can physically hold more water than cool air. The warmer the air the more water vapor the air can hold (i.e. relative humidity). The capacity doubles for every ten degree Celsius warming.

One physical result is more massive raindrops. The Momentum of Rain is p = mv (p = momentum, m = mass, v = velocity.) Part of the increasing momentum is transferred to the sides and upward increasing wind turbulence, as well as updrafts. Most of the momentum is transferred upon impact. You may notice the rain bouncing higher off the streets and sidewalks. Flowing rainwater will have both increased mass and velocity.

On the ground, concrete, asphalt, solar panels, roofs, plants, animals, houses, and infrastructure will be hit with greater momentum. In the air, the increasing mass of the rain will intensify wind turbulence. Professor Paul D. Williams of the University of Reading, UK, said, "Turbulence is chaotic (chaos theory). Turbulence is known famously as the hardest problem in physics." In their study Evidence for Large Increases in Clear-Air Turbulence Over the Past Four Decades, Prof. Williams and his team found "Climate change has caused turbulence to double in the last 40 years" and is expected to double or triple again in the next decades.

Mass and velocity are parts of a larger equation that also includes density.The combination of these variables results in an increased intensity of the flow forces (i.e. flow dynamics). Wind and water flow forces scale as the square of velocity, so as flow speeds increase (say due to more intense heating or heavier rain) the damage scales as the square of the velocity. Look at drag physics and you will see that force is proportional to density times square of velocity (v^2).

So a twenty mile an hour wind exerts four times as much force as a ten mile an hour wind. And a forty mile an hour wind exerts sixteen times as much force as a ten mile an hour wind. A wind of fifty miles an hour exerts twenty five times and a wind of sixty miles an hour exerts thirty six times as much force as one of ten miles an hour. Then you have the density term. Water is about eight hundred times denser than air, so the force exerted by a ten mile an hour flow of water is eight hundred times that of a ten mile an hour wind. As flow velocities go up due to climate change, force and damage scale as square of the velocities. What is not clear is how much these velocities increase with climate change. But in a sense we are seeing this already as, for example, flood and sewage systems succumb and hillsides fall down, and so on.

The Drag Equation

UAE Stormwater Flooding

Rainfall-surge Hazard
The Journal Nature published the study Tropical cyclone climatology change greatly exacerbates US extreme rainfall-surge hazard examining how current models underestimate the risk of Rainfall-surge Hazard. "Tropical cyclones (TCs) are drivers of extreme rainfall and surge, but the current and future TC rainfall-surge joint hazard has not been well quantified. Using a physics-based approach to simulate TC rainfall and storm tides, we show drastic increases in the joint hazard from historical to projected future (SSP5-8.5) conditions. The frequency of joint extreme events (exceeding both hazards' historical 100-year levels) may increase by 7-36-fold in the southern US and 30-195-fold in the Northeast by 2100. This increase in joint hazard is induced by sea-level rise and TC climatology change; the relative contribution of TC climatology change is higher than that of sea-level rise for 96% of the coast, largely due to rainfall increases. Increasing storm intensity and decreasing translation speed are the main TC change factors that cause higher rainfall and storm tides and up to 25% increase in their dependence."

Expect to see increasing intensity and/or frequency in a wide variety of violent rain events including: downpours, flooding, hurricanes, cyclones, monsoons, coastal flooding, storm surges, lightning and wildfires, hail, extreme wind, and concurrent extremes. The reign of violent rain has already begun. More hillsides and shorelines are collapsing. Atmospheric rivers are dramatically increasing flash flooding in the Northeastern USA (pictured beach erosion in Ocean City, NJ / December 2023). Worldwide, stormwater systems are becoming overwhelmed. Ironically, the streets of Abu Dhabi and Dubai, UAE, flooded days before the COP28 Climate Conference (pictured / November 2023). Nowhere is safe from violent rain, not even in the desert preparing for a UN meeting on the climate crisis. As a result of increasing violent rain, new drainage culverts are forming. Eventually, the culverts will transform into recurring streams, carving new canyons, creating new landscapes and islands. In addition, extreme weather events are increasing the frequency of lightning storms and wildfires. After wildfires, rain deluges cause massive landslides transforming the topography. At the same time as the violent rain makes its way to the sea, the sea is rising to meet the violent rain.

Ocean City Beach Erosion

You can kind-of imagine Eastern and Western North America as giant beaches with ever increasing atmospheric waves splashing down on us. The Gulf Coast will be hit from both sides.

Eastern North America
The Eastern US is already seeing violent rain events as far inland as Kentucky with historic flooding in both 2022 and 2023. Eastern Canada has experienced its worst hurricanes on record. Florida, South Carolina, and North Carolina have suffered billions of dollars in storm damage. Homeowners insurance is becoming increasing difficult to obtain in Florida.

The Philadelphia Experiment
Philadelphia is 78 miles from the nearest coast; however, since 2021 Philadelphia has seen a multitude of violent rainstorms resulting in more precipitation than normally falls in an entire month falling in each episode. Besides being hit with Nor'easters and Southeastern tropical storms, Philadelphia is increasing getting deluges from the Gulf of Mexico.

Vine Street Expressway Flooded

Hurricane Ida in the summer of 2021 is a good example. Because of the 85 degrees Fahrenheit Gulf of Mexico ocean temperature, Ida rapidly gained strength right before it made landfall jumping from a Category 1 to a Category 4 storm. The warm air allowed more moisture to be carried as rain. The storm was so large that it was able to pick up more moisture from the Atlantic Ocean. After destroying parts of Florida, the ocean moisture was carried inland and dumped over places like Pennsylvania and New York. Ida caused record flood damage in parts of Pennsylvania. The Philadelphia Inquirer reported, "The remnants of Hurricane Ida destroyed or damaged hundreds of homes in Southeastern Pennsylvania and caused more than $100 million in public infrastructure damage across the state." There were more deaths in the Northeastern USA than where the storm made landfall in Louisiana. The New York Times reported, "The remnants of Hurricane Ida caused flash flooding and a number of deaths and disrupted transit across parts of New York and New Jersey. The storm killed at least 43 people in New York, New Jersey, Pennsylvania and Connecticut and left more than 150,000 homes without power." Ida's Philadelphia area destruction included 5 deaths, 7 tornadoes, record flooding, hundreds of water rescues, and "one incredibly soggy mess." The violent rain in Philadelphia was so extreme that the main road across the city from the Delaware River to the Schuylkill River, the Vine Street Expressway, was turned into a canal. "You could've swam from 22nd Street to about 15th Street," said Justin Galbreath, a district maintenance manager at the Pennsylvania Department of Transportation. As climate change intensifies, the frequency of Vine Street becoming a river will likely increase until such time as it becomes permanent.

The train derailment in Plymouth Meeting (July 17, 2023), the eleven vehicles swept away, and the seven people drowned by flood waters in Washington Crossing (July 15, 2023) were caused by a deluge of rain and flash flooding. "In my 44 years, I've never seen anything like it," Upper Makefield Fire Chief Tim Brewer said. "When the water came up, it came up very swiftly. We do not think that anybody drove into it, that they were actively on that road when it happened." CBS news reported, "Over 6 inches of rain in an hour caused the flash flooding according to Brewer. The fire department was dispatched in that area for a lightning strike and just by happenstance they found 11 cars. Eight people were rescued from the cars and two from the creek." In July and December of 2023, extreme rainfall resulted in sinkholes being exposed in the carbonate rock under Route 202 in nearby King of Prussia, PA.

In September of 2023, the Philadelphia Inquirer reported, "The remnants of Tropical Storm Ophelia soaked the entire Philadelphia region with episodic downpours on Saturday, the first day of fall, conspiring to incite 60-mph wind gusts at the Shore and high-tide flooding that closed numerous roads in beach and back-bay towns." There were up to 8 inches of rain recorded throughout the Philadelphia region over the three day event.

The winter of 2023 saw near weekly atmospheric river flash flooding events. On January 9, the Greater Philadelphia Region incurred an historic winter tropical violent rain event. CBS news reported, "If it feels like it's been an abnormally rainy few weeks, you're right. Normal rainfall totals between Dec. 1 and Jan. 9 amount to about 4.78 inches. Between December 2023 and Tuesday, we'd already recorded more than 9 inches of rain, an amount normally recorded in December, January and February combined." The January 9 storm brought over 4 inches of rain to many areas. The Delaware River peaked at its highest level ever. There were hurricane strength winds with wind gusts over 70mph.

Western North America
As the Earth warms, the air will hold more moisture. More moisture-laden air moves over land and creates atmospheric rivers (Pineapple Express). The Journal EOS in the article Atmospheric Rivers Spur High-Tide Floods on U.S. West Coast said, "Atmospheric rivers are narrow bands of moisture that travel across the lower troposphere, generally at the leading edges of massive low-pressure systems. At their peak, they can carry as much water through the sky as the Amazon River does on land. They unleash intense winds and heavy rain as they surge across the Pacific Ocean, eventually making landfall on the U.S. West Coast, contributing to many high-tide flooding events."

The atmospheric rivers also bring heavy rainfall inland causing extreme flooding. In October of 2021 NOAA said, "a convergence of storms brought more than half a foot of rain to parts of the Bay area in addition to strong winds, flash floods, and mud/landslides. They also bring the potential for heavy snow to higher elevations in the Sierra Nevada mountain range." (Atmospheric River Hits the West Coast)

In December 2022 and January 2023, California experienced nine back-to-back atmospheric rivers; the longest stretch of continuous atmospheric river conditions on record. NOAA went on to report, "Several atmospheric rivers struck in March 2023, bringing heavy rain and snowfall to much of the West. According to the California Department of Water Resources, the statewide snowpack was among the deepest ever recorded for the end of March -- 237% of normal."

In October of 2023, a tropical storm turned into category 5 Hurricane Otis in a record 12-hour intensification. Hurricane expert Kerry Emanual said Otis was supercharged by global warming. Historically, hurricanes' intensification was driven by ocean surface temperatures. Otis was additionally supercharged by increasing temperatures deeper in the ocean. Hurricane Otis became the strongest on record to hit Mexico's Pacific coast. NOAA reported, "When Otis first hit, mudslides outside the city in mountainous terrain prevented crews from traveling to the city to provide aid, and according to the Associated Press, the 10,000 troops that were deployed to the area lacked the tools needed to clear mud and downed trees off roads."

East Coast Atmospheric Rivers
Historically in the United States, atmospheric rivers (AR) have been associated with the West Coast. Now, AR activity is getting more attention on the East Coast. "Actually, their frequency is not really increasing. Meteorologists have used the term for decades. It has simply become popular by the media. Just like polar vortex," said Jeff Boyne, National Weather Service meteorologist and climatologist. Indeed, "atmospheric rivers are more frequent on the East Coast than they are on the West Coast," said Jason Cordeira, associate professor of meteorology at Plymouth State University. "They're just not as impactful and don't usually produce as much rainfall."

What is changing is the research into the types and increasing intensity of East Coast AR events. "Between 1958 and 2012, the Northeast saw more than a 70% increase in the amount of rainfall measured during heavy precipitation events, more than in any other region in the United States. Projections indicate continuing increases in precipitation, especially in winter and spring and in northern parts of the region," as reported in The US Fourth National Climate Assessment.

Most types of East Coast ARs are increasing in intensity likely due to climate change. The study Identifying Eastern US Atmospheric River Types and Evaluating Historical Trends reports, "The impact of increasing moisture transport could be significant across the northeast corridor from Washington D.C. to Coastal Maine, as it increases the risk of extreme precipitation from landfalling ARs. The results indicate most ARs in the study domain are forced by extratropical cyclones, with lee side low pressure systems and coastal lows along the Atlantic Coast (e.g. nor'easters) responsible for producing the strongest ARs."

Climate change is expected to have complex and potentially significant impacts on both the AMOC (Atlantic Meridional Overturning Circulation) and atmospheric rivers along the East Coast of the USA. The AMOC is interconnected with atmospheric circulation patterns, including the position of the jet stream. Changes in the AMOC can influence the jet stream's behavior, which, in turn, affects the development and trajectory of atmospheric rivers. The jet stream is a key player in steering weather systems and atmospheric rivers.

How Fast Are Atmospheric Rivers Gaining Intensity?
Some areas of the world are now warming so fast, it is becoming more difficult to measure the change from "normal" or average. Jeff Boyne of the NWS said, "There are climate normals that are updated every 10 to 15 years, because the planet is warming so fast. The ENSO (El Nino-Southern Oscillation) regions are warming so fast that those normals are being updated every 5 years." Overall, how fast is climate change accelerating? Rapidly. "It's so far outside anything we've seen, it's almost mind-blowing," says Walter Meier, who monitors sea-ice with the National Snow and Ice Data Center. "September was, in my professional opinion as a climate scientist, absolutely gobsmackingly bananas," said Zeke Hausfather, at the Berkeley Earth climate data project."

Humans are making the Earth hotter. The cool water from the melting ice at the poles is being drawn toward the center of the Earth and getting warmed to record high temperatures. The warm, moist air is circulating and moving over land. The average time moisture stays in the air is 9 days before it turns into precipitation. The warmer the air becomes, the more rain the atmosphere holds and dumps; therefore, violent rain events are increasing in frequency and intensity.

The greatest short term risk to the Earth is violent rain (liquified water vapor). The greatest short term risk to human health is deadly humid heat (hot water vapor).

* Our climate model employs chaos theory to comprehensively consider human impacts and projects a potential global average temperature increase of 9℃ above pre-industrial levels.

What Can I Do?
There are numerous actions you can take to contribute to saving the planet. Each person bears the responsibility to minimize pollution, discontinue the use of fossil fuels, reduce consumption, and foster a culture of love and care. Be a butterfly and affect the world. The Butterfly Effect illustrates that a small change in one area can lead to significant alterations in conditions anywhere on the globe. Hence, the frequently heard statement that a butterfly in China can cause a hurricane in the Atlantic.
Here is a list of additional actions you can take.

How is All Real Estate at Risk From Climate Change? / Brouse and Mukherjee (2024)
Flood Insurance / Brouse and Mukherjee (1995-present)

Climate Change: Atmospheric Rivers

Violent Rain and the Substrate

Climate Change, the Jet Stream, and East Coast Atmospheric Rivers

Climate Change: Rate of Acceleration

Climate Change: How Long Is "Ever"?

The Human Induced Climate Change Experiment

The Philadelphia Spirit Experiment Publishing Company
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