Rivers in the sky is the description of a phenomenon written up in Scientific American, in January, 2013 in The Coming Megafloods (pdf file.) Most people have never heard of them - I hadn't, but I'm paying attention now.
Atmospheric rivers are long streams of water vapor that form at about one mile up in the atmosphere. They are only 250 miles across but extend for thousands of miles—sometimes across an entire ocean basin such as the Pacific. These conveyor belts of vapor carry as much water as 10 to 15 Mississippi Rivers from the tropics and across the middle latitudes. When one reaches the U.S. West Coast and hits inland mountain ranges, such as the Sierra Nevada, it is forced up, cools off and condenses into vast quantities of precipitation.In 1861, one of these rivers dumped enough rain on California to flood hundreds of square miles, wash away towns, drown thousands of people, and bankrupt the state. And it may be on the verge of happening again, sooner than the roughly 200 year average predicted by geologic evidence. It's going to be real hard to deny climate change when the water starts to rise...
More below the Orange Omnilepticon.
What we see around us, the shape of the land, the vegetation that grows on it (including our crops), the wildlife we share it with is shaped in a large part by the water that falls on it, in whatever form. How steep hills are, how watercourses are shaped as water moves downhill reflect the amounts of precipitation within a normal range for a given region. Let weather shift outside those norms, and things can change rapidly. From the Scientific American article linked above, here's what happened in California in 1861.
The intense rainstorms sweeping in from the Pacific Ocean began to pound central California on Christmas Eve in 1861 and continued virtually unabated for 43 days. The deluges quickly transformed rivers running down from the Sierra Nevada mountains along the state’s eastern border into raging torrents that swept away entire communities and mining settlements. The rivers and rains poured into the state’s vast Central Valley, turning it into an inland sea 300 miles long and 20 miles wide. Thousands of people died, and one quarter of the state’s estimated 800,000 cattle drowned. Downtown Sacramento was submerged under 10 feet of brown water filled with debris from countless mudslides on the region’s steep slopes. California’s legislature, unable to function, moved to San Francisco until Sacramento dried out—six months later. By then, the state was bankrupt.emphasis added
The article by Michael D. Dettinger and B. Lynn Ingram explains that the discovery of these Atmospheric Rivers was fairly recent, around 1998 when researchers in three different programs came up with data revealing what was happening - a combination of high-altitude observations by a NOAA jet aircraft, computer climate modeling at M.I.T. and new sensor data from satellites measuring the distribution of water vapor in the atmosphere. Now that they know what to look for, meteorologists are designing instruments to track these rivers and are incorporating them into their computer models. This is one reason why forecasters are now able to make earlier predictions of heavy rains, allowing more time to prepare.
This is probably what weather dude is referring to when he writes about:
A ribbon of deep tropical moisture is forecast to sweep across the east coast for the next week, leading to the potential for major rainfall totals and the potential for flash flooding for much of the east coast.emphasis added
The illustration on page 71 of Dettinger and Ingram's article shows one such atmospheric river coming out of the Gulf of Mexico and aiming right up the Eastern Seaboard roughly along the Appalachians.
An additional factor in predicting floods is understanding just how much water is already in the ground and how much more can be soaked up. When standing water is still visible a day or two after a storm, that's an indication that the ground may be saturated; further rainfall will simply run down hill rather than being absorbed. Vegetation is one of the factors in modeling this; forests and wetlands can act like sponges. Conversely, acres of asphalt act like giant funnels collecting rain water and channeling it to whatever the local drainage is. Too much rain and the effect can be overwhelming. England has been experiencing greater than normal rainfall, and they're taking a look at this kind of thing to improve flood forecasting (David Shukman, BBC News).
One project being planned for release later this year is the first of a series of 'hydrological outlooks' for the UK - forecasts of water conditions for the month ahead.The video linked in the block quote above is well worth watching for a demonstration of what shifting weather patterns can mean. England went from drought to saturation in the course of a year; and among possible factors cited were shifting jet streams, melting of the polar ice cap, and global warming putting more moisture in the air.
This is being prepared with data from every rainfall station across the country, together with readings from the UK's 1300 river gauges, plus information about soil moisture.
It involves the Met Office, the Environment Agency and the Centre for Ecology and Hydrology (CEH).
On Thursday I reported from the CEH on the latest findings about how much water has soaked into the ground - and saw a bore-hole used for measuring water levels actually spouting out water because the ground was so saturated.
If nothing else, this means increasing variability in weather patterns. Dettinger and Ingram note that modeling of climate change effects suggest for California and elsewhere, where atmospheric rivers are a factor, they will become more frequent and larger as climate change progresses.
When project leaders ran the events of ARkStorm [the name given to a weather modeling exercise - Atmospheric River 1000 Storm] through a variety of weather, runoff, engineering and economic models, the results suggested that sustained flooding could occur over most lowland areas of northern and southern California. Such flooding could lead to the evacuation of 1.5 million people. Damages and disruptions from high water, hundreds of land- slides and hurricane-force winds in certain spots could cause $400 billion in property damages and agricultural losses. Longterm business and employment interruptions could bring the eventual total costs to more than $700 billion. Based on disasters elsewhere in recent years, we believe a calamity this extensive could kill thousands of people (the ARkStorm simulation did not predict deaths).emphasis added
The illustrations in the Dettinger and Ingram article are fascinating, with a kind of grim beauty when one considers their import. The projections from their work and others indicate that Climate Change has the potential to wreak massive amounts of damage just from flooding alone - and it should be noted this isn't something like a hurricane. This is a sustained drenching that doesn't stop. I wrote up the other day what happened when one day of sustained rainfall hit a region that had already been having a wet year. The damage was considerable. Weatherdude is warning of more to come. (And let's not forget another ongoing weather event right now. Stuff is happening)
Climate change is not a joke. The Republican war on government and science means that we not only are stuck with crumbling infrastructure, the infrastructure we have is not built to deal with the increasing shift and variability in weather patterns we are starting to experience. Even as conservatives try to get government down to a size where it can be "drowned in a bathtub" we're going to be facing potential disaster on a scale that can only be addressed at the federal level. Investments in water supplies, water and sewer projects, drainage, agriculture, energy, development policies - all of that needs to done with an eye to the New Normal we're headed for.
To paraphrase the bumper sticker, climate change is a global phenomenon - but we're all going to be feeling it locally.
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