Vapor Storms threatening people & property

[Niall Dollard]

Jennifer Francis's excellent article on the role of the global iincrease in water vapor fuelling storms/heavy rains.

https://www.scientificamerican.com/article/vapor-storms-are-threatening-people-and-property/

[Juan C. García]

Jennifer Francis's excellent article on the role of the global iincrease in water vapor fuelling storms/heavy rains.

https://www.scientificamerican.com/article/vapor-storms-are-threatening-people-and-property/

The amount of vapor in the atmosphere has increased about 4 percent globally just since the mid-1990s. That may not sound like much, but it is a big deal to the climate system.
...
Unlike most other atmospheric gases, water vapor is not evenly distributed around the globe. Vapor is abundant in the steamy tropical regions straddling the equator. From there, long tendrils of moisture can extend toward the cooler, drier poles along storm tracks, bathing mid- and high-latitude regions in bouts of intense, prolonged precipitation. These rivers of heat and moisture help to balance Earth’s atmospheric energy distribution—and they are creating strong vapor storms along their path.
...
The most worrisome consequence of increasing atmospheric water vapor may be its role in the rapid intensification of tropical storms.
...
Increasing water vapor is not the only impact of climate change on tropical storms, however. Decreasing wind shear—the difference in speed or direction between winds closer to the ground and those high in the atmosphere—also favors storm development because the towers of rising air are less likely to be torn apart. Other variables now being studied include changes in the amount of dust and pollution particles in the air, as well as differences in atmospheric warming at lower and higher altitudes, which affect how fast those bubbles of warm air rise.
...
The threat from increased water vapor extends beyond storms. It is also making summer nights intolerably steamy—more often and in more places.
...
If intense storms and sweltering nights are not troubling enough, water vapor is also making global warming worse. Even though carbon dioxide gets most of the attention, water vapor is by far the most important greenhouse gas in the atmosphere.

[kassy]

It also has effects beyond the tropics as can be seen in the floods thread.

The base principle is simple:

Put simply, water evaporates from the land and sea, which eventually returns to Earth as rain and snow. Climate change intensifies this cycle because as air temperatures increase, more water evaporates into the air. Warmer air can hold more water vapor, which can lead to more intense rainstorms, causing major problems like extreme flooding in coastal communities around the world.

But it doesn’t end there. At the same time that some areas are experiencing stronger storms, others are experiencing more dry air and even drought. Like we mentioned above, as temperatures rise, evaporation increases and soils dry out. Then when rain does come, much of the water runs off the hard ground into rivers and streams, and the soil remains dry. The result? Still more evaporation from the soil and an increased risk of drought.

https://www.climaterealityproject.org/blog/climate-change-impacting-water-cycle

In a warming world we will not have less rainfall but it falls in different places and in different intensities. 24 hours of drizzle to moderate rainfall is ok if weather changes after a couple of days Getting your normal monthly regional rainfall in one day will damage things.

[kassy]

On the interaction between warm and wet:

People living in British Columbia will feel like they have had more than their fair share of climate disasters in 2021. After a record-breaking heatwave in June, the state in western Canada has been inundated by intense rain storms in November. It’s also likely the long-lasting effects of the heatwave made the results of the recent rainfall worse, causing more landslides – which have destroyed highways and railroads – than would otherwise have happened.

In June 2021, temperature records across western North America were shattered. The town of Lytton in British Columbia registered 49.6°C, breaking the previous Canadian national record by 5°C. The unprecedented weather was caused by a high pressure system, a so-called “heat dome”, which sat over the region for several days.

Heat intensified within the dome as the high pressure compressed the air. Dry ground conditions forced temperatures even higher, as there was less water evaporating to cool things down. Although unconfirmed, it’s estimated that the heatwave caused over 400 deaths in British Columbia alone.

The hot and dry weather also sparked wildfires. Just days after recording the hottest national temperature ever, the town of Lytton burned to the ground. The summer’s fires and drought left the ground charred and barren, incapable of absorbing water. These conditions make landslides more likely, as damaged tree roots can no longer hold soil in place. It also ensures water flows over the soil quicker, as it cannot soak into the baked ground.

The huge rain storm which lasted from Saturday November 13 to Monday 15 was caused by an atmospheric river – a long, narrow, band of moisture in the atmosphere stretching hundreds of miles. When this band travels over land it can generate extreme rainfall, and it did: in 48 hours, over 250mm of rain fell in the town of Hope, 100km east of Vancouver.

This much rainfall on its own would probably cause extensive flooding. But combined with the parched soil, the results have been catastrophic. Landslides have destroyed many of the region’s transport links, leaving Vancouver cut off by rail and road. But the bad news doesn’t end there; sediment washed away by these floods could make future floods this winter even worse.

... more

https://theconversation.com/canadas-flood-havoc-after-summer-heatwave-shows-how-climate-disasters-combine-to-do-extra-damage-172187

[morganism]

between 2-3 atmospheric rivers again headed for BC Canada. Level 3 for the first two predicted. Snow first, then rain.

https://cw3e.ucsd.edu/cw3e-ar-update-24-november-2021-outlook/

[vox_mundi]

Measuring Climate Change: It's Not Just Heat, It's Humidity
https://phys.org/news/2022-01-climate-humidity.html

Researchers say temperature by itself isn't the best way to measure climate change's weird weather and downplays impacts in the tropics. But factoring in air moisture along with heat shows that climate change since 1980 is nearly twice as bad as previously calculated, according to their study in Monday's Proceedings of the National Academy of Sciences.

The energy generated in extreme weather, such as storms, floods and rainfall is related to the amount of water in the air. So a team of scientists in the U.S. and China decided to use an obscure weather measurement called equivalent potential temperature—or theta-e —that reflects "the moisture energy of the atmosphere," said study co-author V. "Ram" Ramanathan, a climate scientist at the University of California San Diego's Scripps Institution of Oceanography and Cornell University. It's expressed in degrees, like temperature.

"There are two drivers of climate change: temperature and humidity," Ramanathan said. "And so far we measured global warming just in terms of temperature."

But by adding the energy from humidity, "the extremes—heat waves, rainfall and other measures of extremes—correlate much better," he said.

From 1980 to 2019, the world warmed about 1.42 degrees (0.79 degrees Celsius). But taking energy from humidity into account, the world has warmed and moistened 2.66 degrees (1.48 degrees Celsius), the study said. And in the tropics, the warming was as much as 7.2 degrees (4 degrees Celsius).



When judging by temperature alone, it looks like warming is most pronounced in North America, mid-latitudes and especially the poles—and less so in the tropics, Ramanathan said.

But that's not the case, he said, because the high humidity in the tropics juices up storm activity, from regular storms to tropical cyclones and monsoons.

... By the end of the century, with unchecked global warming, the intensity of model projected extreme precipitation can increase by 40 to 60% relative to current extreme precipitation.

With increased Thetae_sfc, the atmosphere is more convectively unstable, as measured by CAPE, and the maximum altitude a convective parcel from the surface can reach, a proxy for cloud top altitudes of convective clouds, is higher.

The increase of CAPE in both observations and projected future climate can partly explain the increased rainfall extremes and severe thunderstorms

... As the global mean Thetae_sfc increases (Fig. 3A), future heat extremes become more severe. The extreme summer daily mean WBGT in different parts of the world (India, northern China, North America, and Europe) can increase by as much as 6 °C by the end of the 21st century compared with the heat extremes in the current climate.

The occurrence frequency of WBGT extremes exceeding 35 °C increases by 14-fold over India and southern China, 30-fold over northern China, 22-fold over North America, and 23-fold over Europe by 2100



Fengfei Song et al, Trends in surface equivalent potential temperature: A more comprehensive metric for global warming and weather extremes, Proceedings of the National Academy of Sciences (2022).
https://www.pnas.org/content/119/6/e2117832119

[kassy]

Global warming is amplifying our water cycle – and it’s happening much faster than we expected...

The global water cycle – that is, the constant movement of freshwater between the clouds, land and the ocean – plays an important role in our daily lives. This delicate system transports water from the ocean to the land, helping to make our environment habitable and soil fertile.

But rising global temperatures have been making this system more extreme: water is moving away from dry regions towards wet regions, causing droughts to worsen in parts of the globe, while intensifying rainfall events and flooding in others. In other words, wet areas are getting wetter, and dry areas are getting drier.

Up until now, changes to the cycle have been difficult to directly observe, with around 80 per cent of global rainfall and evaporation happening over the ocean.

But a new UNSW-led study, published today in Nature, has used changing patterns of salt in the ocean to estimate how much ocean freshwater has moved from the equator to the poles since 1970. The findings show that between two and four times more freshwater has moved than climate models anticipated – giving us insights about how the global water cycle is amplifying as a whole.

“We already knew from previous work that the global water cycle was intensifying,” says lead author of the study Dr Taimoor Sohail, a mathematician and postdoctoral research associate at UNSW Science.  “We just didn't know by how much.

“The movement of freshwater from warm to cold areas forms the lion’s share of water transport. Our findings paint a picture of the larger changes happening in the global water cycle.”

The team reached their findings by analysing observations from three historical data sets covering the period 1970-2014.

But instead of focusing on direct rainfall observations – which can be hard to measure across the ocean – they focused on a more unusual aspect: how salty the water was in each ocean area.

"In warmer regions, evaporation removes fresh water from the ocean leaving salt behind, making the ocean saltier,” says co-author Jan Zika, an associate professor in the UNSW School of Mathematics and Statistics.

“The water cycle takes that fresh water to colder regions where it falls as rain, diluting the ocean and making it less salty.”

In other words, the water cycle leaves a signature on the ocean salt pattern – and by measuring these patterns, researchers can trace how the cycle changes over time.

The team estimate that between 1970 and 2014, an extra 46,000-77,000 cubic kilometres of freshwater was transported from the equator to the poles than expected – that’s around 18-30 centimetres of freshwater from tropical and sub-tropical regions, or roughly 123 times the water in Sydney Harbour.

“Changes to the water cycle can have a critical impact on infrastructure, agriculture, and biodiversity,” says Dr Sohail. “It’s therefore important to understand the way the climate change is impacting the water cycle now and into the future.

“This finding gives us an idea of how much this limb of the water cycle is changing, and can help us improve future climate change models.”
 
...

https://www.eurekalert.org/news-releases/944176

[kassy]

A reconstruction of last years rain disaster in Limburg (and Germany and Belgium).

July 12th 2021 no rain in NL but a weird system over Limburg
July 13th 20 degrees and 0,5 mm over most of the country in 24 hours.
Maastricht got 24,4 mm
July 14th 1 mm national at 21 C in Maastricht 40,5 mm of rain fell. They got 70mm total so it abated there the next day. A little further to the east the amount was double to triple of that.

In Jalhey they got 271,5 millimeter and in the adjacent german regions they also got a month of summer rain in two days.

The river Maas set a new flow record which was also notable because it was set in summer instead of winter.

There is a threefold link with climate change here:
1 The basic 1C of warming makes the air hold 7% more moisture.

2 Climate change also makes rising air in cloud complexes stronger which increases down poor intensity.

3 This system was also a good example of stuck weather or as they call it persistent weather. West winds slow down due to global warming so we get longer periods of the same weather (this is a climate model for the Netherlands so claims are local).

KNMI and DWD (dutch and german meteorogical societies) ran models and concluded the area´s chance of increased rainfall got 8 times bigger.

https://www.nu.nl/nu-klimaat/6211837/reconstructie-watersnood-in-limburg-een-klimaatramp-kan-overal-toeslaan.html


A bit more on local effects:

Dat percentage mag je in Nederland verdubbelen, want onze zomers zijn nu al ongeveer 2 graden warmer dan een eeuw geleden. "Dus als die lucht uitregent, heb je ook ongeveer 14 procent meer neerslag", aldus Siegmund.

Local increase is 2C so 14%.

And this effect:

Clouds form in rising air, where water vapor condenses and also gives off a little bit of heat. Due to climate change, there is more water vapor in a cloud, so that extra heat is 'produced' within that cloud.

"This makes the shower extra warm compared to its surroundings. As a result, a more powerful ascending airflow is created within the cloud, causing it to drain faster and more powerfully," explains Siegmund.

Due to the faster cloud formation, a larger amount of rain can fall from the sky in a short time. As a result, downpours increase more strongly than average rainfall.

Due to the mutual interaction between climate effects, it is difficult to predict how strong downpours will increase as the Dutch climate warms further.

However, the observations show an upward trend. Days with more than 25 millimeters of precipitation have roughly doubled in a century. That also applies to days with more than 35 millimeters. The amounts that now fall in Limburg, up to 75 millimeters per day, are so rare that it is impossible to make a good graph of them, says Siegmund.

https://www.nu.nl/klimaat/6145554/stortbuien-limburg-passen-in-patroon-zomerneerslag-vaker-in-een-klap.html

[kassy]

Climate change is intensifying the water cycle, bringing more powerful storms and flooding – here’s what the science shows

...

Studies by scientists around the world show that the water cycle has been intensifying and will continue to intensify as the planet warms. An international climate assessment I coauthored in 2021 for the Intergovernmental Panel on Climate Change lays out the details.

It documented an increase in both wet extremes, including more intense rainfall over most regions, and dry extremes, including drying in the Mediterranean, southwestern Australia, southwestern South America, South Africa and western North America. It also shows that both wet and dry extremes will continue to increase with future warming.

Why is the water cycle intensifying?
Water cycles through the environment, moving between the atmosphere, ocean, land and reservoirs of frozen water. It might fall as rain or snow, seep into the ground, run into a waterway, join the ocean, freeze or evaporate back into the atmosphere. Plants also take up water from the ground and release it through transpiration from their leaves. In recent decades, there has been an overall increase in the rates of precipitation and evaporation.

A number of factors are intensifying the water cycle, but one of the most important is that warming temperatures raise the upper limit on the amount of moisture in the air. That increases the potential for more rain.

This aspect of climate change is confirmed across all of our lines of evidence discussed in the IPCC report. It is expected from basic physics, projected by computer models, and it already shows up in the observational data as a general increase of rainfall intensity with warming temperatures.

Understanding this and other changes in the water cycle is important for more than preparing for disasters. Water is an essential resource for all ecosystems and human societies, and particularly agriculture.

What does this mean for the future?
An intensifying water cycle means that both wet and dry extremes and the general variability of the water cycle will increase, although not uniformly around the globe.

Rainfall intensity is expected to increase for most land areas, but the largest increases in dryness are expected in the Mediterranean, southwestern South America and western North America.

Globally, daily extreme precipitation events will likely intensify by about 7% for every 1 degree Celsius (1.8 degrees Fahrenheit) that global temperatures rise.

Many other important aspects of the water cycle will also change in addition to extremes as global temperatures increase, the report shows, including reductions in mountain glaciers, decreasing duration of seasonal snow cover, earlier snowmelt and contrasting changes in monsoon rains across different regions, which will impact the water resources of billions of people.

...

https://theconversation.com/climate-change-is-intensifying-the-water-cycle-bringing-more-powerful-storms-and-flooding-heres-what-the-science-shows-187951

[morganism]

Just posted a twit from a guy saying a major event may be setting up for Vancouver again.

Put it in the RRR thread

https://forum.arctic-sea-ice.net/index.php?topic=2185

[kassy]

Short Extreme Rainfall Events Are More Common - Climate Change Implicated

If you have ever visited or Florida or any place with rainfall extremes at sub-hourly timescales - short storms - residents joke that if you don't like their weather, wait five minutes and it will change.

A new analysis says those changes may be happening quickly, and are intensifying much faster than those on longer hourly or daily timescales. Which means greater chance for damaging environmental hazards like flash flooding. If these intense short-duration precipitation events are being affected by our changing climate. understanding them is crucial for effective climate adaptation and mitigation.

Climate change is expected to alter the intensity and frequency of heavy rainfall worldwide. However, despite advances in understanding the effects of a warming climate on rainfall extremes at daily or longer timescales, less is known about its effect on short-duration or sub-daily rain fall totals. Heavy precipitation at these scales is often responsible for destructive natural hazards, including flash floods, landslides, and debris flows in urban and rural regions. Because sub-daily rainfall extremes often occur over small areas, they can be missed by rain gauge networks, overlooked by satellite measurements, and are poorly predicted by regional climate models.

To better understand how climate change impacts sub-hourly rainfall totals, Hooman Ayat and colleagues used satellite-calibrated observations from three ground-based weather radars surrounding greater Sydney, Australia to evaluate trends in extreme rainfall down to the 10-minute scale over the last 20 years.

Ayat et al. discovered that these short-duration rainfall extremes are becoming more intense – rainfall totals during these sub-hourly events are increasing – much faster than those over longer periods.

According to the findings, despite no evidence of positive trends on the hourly or daily scales, sub-hourly extreme rainfall extremes in the Sydney area has been rising by at least 20% per decade.

https://www.science20.com/news_staff/short_extreme_rainfall_events_are_more_common_climate_change_implicated-256302

[kassy]

How India is battling deadly rain storms as climate change bites

...

Researchers don’t yet fully understand how changes in the ocean and the winds affect the monsoon and, by extension, local weather. But they have seen that the rains are not the same as they were 70 years ago. By 2015, the amount of rain falling over India had declined by about 6% from 1951 levels3. Droughts are now more frequent and widespread. There are prolonged dry spells and more intense wet spells4. And extreme rainfall events, which dump more than 150 millimetres in a single day, became nearly twice as frequent between 1951 and 2022 (see ‘Severe storms’). Widespread extreme downpours have tripled in frequency since 1950 over central India, where about 500 million people live5.

Last year, 95% of India’s extreme weather deaths resulted from thunderstorms, lightning and heavy rainfall, according to government data (see go.nature.com/3jmkrt3). The rains are no longer predictable. In the worst cases, clouds can grow rapidly and deposit more than 100 millimetres of rainfall in an hour over a single neighbourhood.

Tropical rain and thunderstorms, and their impacts, are difficult to forecast sufficiently in advance, particularly at the scale of neighbourhoods or towns. And communicating forecasts is challenging, because many of the two billion people in South Asia live in remote villages and do not receive news alerts.

...

Farther north, close to the Himalayas, individual thunderstorms called cloudbursts can drop more than 100 millimetres of rain in less than an hour, accompanied by strong winds and lightning, over areas of up to 30 square kilometres7. Very little is known about these cloudburst events. “Climate change is making [extreme rainfall] more erratic and the weather forecasting models are unable to account for that increase in chaos,” Koll says. “It is a challenge in the tropics.”

...

https://www.nature.com/articles/d41586-023-00341-5

Some quotes from a long article about India.

[Jim Hunt]

I couldn't find an existing topic that seemed to cover the title above. Moderator please redirect if appropriate.

Emerging from my Cornish alter ego's current campaign against sh1t in the sea comes this recent article from the once United Kingdom's Met Office:

https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2023/new-research-shows-increasing-frequency-of-extreme-rainfall-events

Extreme rainfall events could be four times as frequent by 2080 compared to 1980s.

For the first time, a high resolution model that captures the detail of convective, or extreme, rainfall events has provided 100 years of data, spanning the past, present and future continuously, to analyse the future risk of rainfall with the intensity that can cause flash flooding.

A version of the Met Office Unified Model, the same that is used for the operational UK weather forecast, has been run 12 times at a resolution of 2.2km (known as k-scale modelling) to give an ensemble of 100-year climate projections.

This is like starting 12 weather forecasts and running them for 100 years, except the researchers are not interested in the weather on a given day but rather how the occurrence of local weather extremes varies year-by-year. By starting the model runs in the past it is also possible to verify the output against observations to assess the model performance.

At this level of detail, it is possible to more accurately assess how convective downpours that can lead to flash flooding will change, for example when the intensity of the rain exceeds 20mm/hour. Thresholds of rainfall intensity like 20mm/hr are used for aspects of planning such as surface water drainage and flood risk.

The research, published in Nature Communications, found that under a high emissions scenario (RCP 8.5) rainfall events in the UK exceeding 20mm/hr could be four times as frequent by 2080 compared to the 1980s. Previous coarser model output (12km) predicted an increase of around two and a half times in the same period.

RCP 8.5 is a pathway where greenhouse gas emissions keep accelerating. This is not inevitable, but a plausible scenario if we do not curb our emissions.

RCP 8.5 is not inevitable, but even so the once Great British sewage treatment infrastructure is already struggling under the strain of seemingly ever more frequent bursts of heavy rain over here in the West Country:

https://twitter.com/DavidstowInfo/status/1634321040791728128

Perhaps South West Water can imagine our frustration when the conditions that create 5* surf also create sewage pollution "red flags" on the Surfers against Sewage water quality map?

Or perhaps not?

P.S. It looks as though I've been redirected. However my intention was a topic that wasn't "vapor" specific. My next comment was intended to be power outages due to wind.  Then flooded train lines. Then power outages due to wildfires. etc. etc.

[kassy]

I merged it into this one. It could have gone into some others but this one seemed fine.

[Jim Hunt]

I merged it into this one. It could have gone into some others but this one seemed fine.

This particular post seems to fit in here (despite the slightly strange title of the topic), but how about this sort of thing?

https://V2G.co.uk/2023/02/storm-otto-blacks-out-scotland/

[kassy]

Storm brings black outs on the grid. Seems a normal thing? Maybe less so for Scotland but i don´t know.

[morganism]

Epic snow from all those atmospheric rivers in the West is starting to melt, and the flood danger is rising


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To get a sense of the enormous amount of water atmospheric rivers dumped on the Western U.S. this year and the magnitude of the flood risk ahead, take a look at California’s Central Valley, where about a quarter of the nation’s food is grown.

This region was once home to the largest freshwater lake west of the Rockies. But the rivers that fed Tulare Lake were dammed and diverted long ago, leaving it nearly dry by 1920. Farmers have been growing food on the fertile lake bed for decades.

This year, however, Tulare Lake is remerging. Runoff and snowmelt from the Sierra Nevada have overwhelmed waterways and flooded farms and orchards. After similar storms in 1983, the lake covered more than 100 square miles, and scientists say this year’s precipitation is looking a lot like 1983. Communities there and across the West are preparing for flooding and mudslide disasters as record snow begins to melt.
Satellite images show farmland with only a few small lakes in early March, then a larger lake covering that farmland by early April.
Tulare Lake, long dry, begins to reemerge in March 2023 as flood water spreads across farm fields. NASA Earth Observatory

We asked Chad Hecht, a meteorologist with the Center for Western Weather and Water Extremes at the University of California San Diego’s Scripps Institution of Oceanography, how 2023’s storms compare to past extremes and what to expect in the future.
How extreme were this year’s atmospheric rivers?

California averages about 44 atmospheric rivers a year, but typically, only about six of them are strong storms that contribute most of the annual precipitation total and cause the kind of flooding we’ve seen this year.

This year, in a three-week window from about Dec. 27, 2022, to Jan. 17, 2023, we saw nine atmospheric rivers make landfall, five of them categorized as strong or greater magnitude. That’s how active it’s been, and that was only the beginning."

https://theconversation.com/epic-snow-from-all-those-atmospheric-rivers-in-the-west-is-starting-to-melt-and-the-flood-danger-is-rising-203874

https://www.scientificamerican.com/article/the-west-braces-for-the-most-epic-snowmelt-in-40-years/

[vox_mundi]

Study Shows Warming Planet Is Leading to an Increase In 'Atmospheric River'-Associated Flooding In India
https://phys.org/news/2023-05-planet-atmospheric-river-associated-india.html



A team of atmospheric scientists from the Indian Institute of Technology and the University of California, has found that the number of atmospheric rivers associated with flooding in India has been rising as the planet continues to grow warmer.

... In this new effort, the researchers team examined weather records from the European Reanalysis Version, the Dartmouth Flood Observatory and the India Meteorological Department for the years 1951 through 2020 looking for evidence of ARs that have had an impact on India, most particularly during monsoon seasons.

In so doing, they found AR events impacted the country 596 times, 95% of which occurred during a monsoon season. They also found that 54% of the biggest AR events occurred over the past three decades, suggesting they are not only forming more often but are getting bigger as the planet grows warmer.

The researchers note that warmer ocean surface temperatures over parts of the Indian Ocean have led to more evaporation, which in turn has led to more rain when ARs form. The increase in rain amounts has led to massive floods which have destroyed property and killed thousands of people.

Shanti Shwarup Mahto et al, Atmospheric rivers that make landfall in India are associated with flooding, Communications Earth & Environment (2023).
https://www.nature.com/articles/s43247-023-00775-9

[morganism]

Prof. Jason Box: Atmospheric River Rapids + Why Next Year Will Be Worse + What Can We Do

Content points
- What are atmospheric river rapids?- what do these teach us about extreme deluge events around the world that we are seeing now?- What is driving it?- Why next year will be worse- What do we have to do?

[kassy]

Good video. The first 10 minutes discusses the science the last 5 are mostly politics.

[kassy]

Unveiling global warming's impact on daily precipitation with deep learning

A collaborative international research team led by Professor Yoo-Geun Ham from Chonnam National University and Professor Seung-Ki Min from Pohang University of Science and Technology (POSTECH) has made a discovery on the impact of global warming on global daily precipitation. Using a deep learning approach, they have unveiled a significant change in the characteristics of global daily precipitation for the first time. Their research findings were published on August 30 in the online version of Nature.

The research team devised a deep learning model to quantify the relationship between the intensity of global warming and global daily precipitation patterns. They then applied this model to data obtained from satellite-based precipitation observations. The results revealed that on more than 50% of all days, there was a clear deviation from natural variability in the daily precipitation pattern since 2015, influenced by human-induced global warming.

In contrast to conventional studies, which primarily focus on long-term trends in monthly or annual precipitation, the researchers employed explainable artificial intelligence to demonstrate that changes in daily precipitation variations were gradually intensifying upon weather timescales. These fluctuations in rainfall at this weather time scale served as the most conspicuous indicators of global warming. The study further affirmed that the most evident changes in daily precipitation variability were observed over the sub-tropical East Pacific and mid-altitude storm track regions.

The researchers explained that traditional linear statistical methods used in previous climate change detection research had limitations in discerning non-linear reactions such as the intensified variability in daily precipitation. Deep learning, however, overcame these limitations by employing non-linear activation functions. Moreover, while previous research methods primarily investigated global precipitation change patterns due to global warming, convolutional deep learning offered a distinct advantage in effectively detecting regional change patterns resulting from global warming.

Professor Yoo-Geun Ham explained, "Intensification of day-to-day precipitation variability implies an increase in the frequency of extreme precipitation events as well as a higher occurrence of heatwaves during the summer due to extended dry spells." Professor Seung-Ki Min added, "Given the ongoing trajectory of global warming, it is imperative to develop countermeasures as the consecutive occurrence of extreme precipitation and heatwaves are likely to become more frequent in the future."

https://www.sciencedaily.com/releases/2023/08/230830131932.htm

[morganism]

The Demon River

(story of the BC flooding last year, good read....)
(...)
The makings of a very bad day on the Nicola River first took shape in the afternoon of November 12, 2021—three days before Constable Schmidt turned onto Highway 8.

Just north of Hawai‘i, a vast reservoir of moisture had pooled in the sky, fed by a humid tropical jet stream and evaporation from an unseasonably warm Pacific Ocean.

Like water spilling out of a lake into a canyon, the moisture began to flow northeast, squeezed between a low-pressure system and a high-pressure system. In less than a day, the plume traveled 2,000 kilometers to North America’s west coast. From space, it looked like a rushing river, and the comparison is more than fair: it probably carried more water than the Amazon, the world’s largest river by volume.

We never truly saw atmospheric rivers, as these flows in the sky are now known, until scientists produced the first images of them, based on satellite readings, in the early 1990s. In everyday life, they go by other names, such as Pineapple Express or Tropical Punch—storms that cruise up from the tropics, mainly in the late autumn and early winter, bringing stiff winds, warm air, and heavy rain.

Over time, we learned that dozens of atmospheric rivers flow up to the North American shore between California and Alaska each year—it is one of the most active atmospheric river zones on the planet.

Most of these precipitation events are valuable: a single storm can deliver one-fifth of an area’s annual rainfall, replenishing groundwater, rivers, and lakes. Sometimes, however, they’re trouble. More than three-quarters of BC’s disastrous floods have occurred when an atmospheric river fell out of the sky.

Atmospheric rivers have never yet been given names the way windstorms have, such as Hurricane Ian or Super Typhoon Noru. In the United States, however, a five-point scale to describe the intensity of atmospheric rivers—not unlike the ranking applied to hurricanes—was proposed in 2019. A “weak” Category 1 atmospheric river would be a beneficial rainstorm, giving comfort and succor to farmers and ducks. A Category 5 might do billions of dollars’ worth of damage. A lot depends on exactly where a storm’s rain falls, and for how long.

The one pouring toward the North American shore in mid-November of 2021 was 400 kilometers wide, about 4,000 kilometers long, and looked powerful. The question was where it would land.
(more)

https://hakai.org/the-demon-river/

[kassy]

Future floods: Global warming intensifies heavy rain -- even more than expected

The intensity and frequency of extreme rainfall increases exponentially with global warming, a new study finds. The analysis shows that state-of-the-art climate models significantly underestimate how much extreme rainfall increases under global warming -- meaning that extreme rainfall could increase quicker than climate models suggest.

...

While most land-areas exhibit increases in both the intensity and frequency of extremes, stronger increases are typically found across tropical regions, according to the study. Significant changes most often occur across the tropics and high-latitudes, like in Southeast Asia or Northern Canada. The fact that these changes follow the Clausius-Clapeyron relation underpins the fact that thermodynamics, i.e. temperature and not dynamics, i.e. winds, dominate the global change of extreme rainfall events. "The good news is that this makes it easier to predict the future of extreme rainfall. The bad news is: It will get worse, if we keep pushing up global temperatures by emitting greenhouse gases," Anders Levermann adds.

https://www.sciencedaily.com/releases/2023/11/231127132446.htm

[kassy]

Air pollution hides increases in rainfall


We know that greenhouse gas emissions like carbon dioxide should increase rainfall. The emissions heat the atmosphere, causing a one-two punch: warmer oceans make it easier for water to evaporate, and warmer air can hold more water vapor, meaning more moisture is available to fall as rain. But for much of the 20th century, that increase in precipitation didn't clearly show up in the data.

A new study led by researchers at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) finds that the expected increase in rain has been largely offset by the drying effect of aerosols -- emissions like sulfur dioxide that are produced by burning fossil fuels, and commonly thought of as air pollution or smog.

The research is published today in the journal Nature Communications.

"This is the first time that we can really understand what's causing extreme rainfall to change within the continental U.S.," said Mark Risser, a research scientist at Berkeley Lab and one of the lead authors for the study.

He noted that until the 1970s, the expected increases to extreme rainfall were offset by aerosols.

But the Clean Air Act caused a drastic reduction in air pollution in the United States.

"The aerosol masking was turned off quite suddenly. That means rainfall might ramp up much more quickly than we would have otherwise predicted."

Traditional climate models have struggled to confidently predict the human impact on rainfall at scales smaller than a continent -- and that regional level is precisely where most climate change adaptations and mitigations take place.

By using a new method and relying heavily on measurements from rain gauges from 1900 to 2020, researchers were able to more robustly determine how human activities have influenced rainfall in the United States.

"Prior to our study, the Intergovernmental Panel on Climate Change [IPCC] had concluded that the evidence was mixed and inconclusive for changes in U.S. precipitation due to global warming," said Bill Collins, associate laboratory director for the Earth and Environmental Sciences Area at Berkeley Lab and co-lead author on the study.

"We have now provided conclusive evidence for higher rainfall and also helped explain why past studies assessed by the IPCC reached conflicting conclusions."

Specifically, the study isolates how greenhouse gas and aerosol emissions affect both average and extreme rainfall.

Researchers confirmed that increased greenhouse gas emissions, which quickly disperse over the whole planet, cause an increase in rainfall.

The impact from aerosols is more nuanced. Over the long term, aerosols cool the planet, which causes a drying effect.

But they also have a faster, more local response. That fast impact depends on the season, with aerosols generally reducing rainfall in the winter and spring, and amplifying it in summer and fall over much of the United States.

"The seasonality piece is really important," Risser said. "For rainfall, the nature of climate change depends on what season you're talking about, since different kinds of weather systems create precipitation in different parts of the year."

...

https://www.sciencedaily.com/releases/2024/02/240222122358.htm

[morganism]

Ben Noll  @BenNollWeather Mar 8

February 2024 was the moistest February on record for Earth 💧

Over 68% of the planet experienced above normal atmospheric moisture.

This was associated with major precipitation events in several continents, including western North America/California.

El Niño was a contributing factor, but not the only one: a warmer world is a moister world and that's evidenced by a weather variable called "total column water" or "precipitable water", the total moisture amount in a column of air, from the ground all the way up to the top of the atmosphere.

Higher atmospheric moisture content loads the dice toward extreme rainfall events 🌧️

We track global monthly temperature rankings in near real-time, so why not atmospheric moisture too?

To help bridge this gap, I make available a global moisture anomaly map and ranking chart, updated once a month around the 7th on this page:

https://www.bennollweather.com/weather-graphics

You are welcome to download the high resolution imagery and/or embed the graphics on a webpage.

Happy moisture tracking!

https://nitter.poast.org/BenNollWeather/status/1765915744221700547#m

[trm1958]

And water vapor is a powerful greenhouse gas!

[kiwichick16]

is it still + 7 % increase in water vapour for each degree C increase inavarege global temperature?

[kassy]

Under typical atmospheric conditions, the denominator of the exponent depends weakly on
T (for which the unit is degree Celsius). Therefore, the August–Roche–Magnus equation implies that saturation water vapor pressure changes approximately exponentially with temperature under typical atmospheric conditions, and hence the water-holding capacity of the atmosphere increases by about 7% for every 1 °C rise in temperature.[17]

https://en.wikipedia.org/wiki/Clausius%E2%80%93Clapeyron_relation

Yes it´s a physical law.

This also means more evaporation with higher global temperatures so a lot of places will get drier.