Stories tagged The Water Cycle, Weather and Climate


An opinion piece in the Sunday, August 12, 2012 New York Times by three scientists (listed at the end) deserves repeating. Here are some excerpts:

Until recently, many scientists spoke of climate change mainly as a “threat,” sometime in the future. But it is increasingly clear that we already live in the era of human-induced climate change, with a growing frequency of weather and climate extremes like heat waves, droughts, floods and fires.

In terms of severity and geographic extent, the 2000-4 drought in the West exceeded such legendary events as the Dust Bowl of the 1930s. More seriously still, long-term climate records from tree-ring chronologies show that this drought was the most severe event of its kind in the western United States in the past 800 years.

Most frightening is that this extreme event could become the new normal: climate models point to a warmer planet, largely because of greenhouse gas emissions. Planetary warming, in turn, is expected to create drier conditions across western North America, because of the way global-wind and atmospheric-pressure patterns shift in response.

The current drought plaguing the country is worryingly consistent with these expectations. Although we do not attribute any single event to global warming, the severity of both the turn-of-the-century drought and the current one is consistent with simulations accounting for warming from increased greenhouse gases.

And yet that may be only the beginning, a fact that should force us to confront the likelihood of new and painful challenges. A megadrought would present a major risk to water resources in the American West, which are distributed through a complex series of local, state and regional water-sharing agreements and laws. Virtually every drop of water flowing in the American West is legally claimed, sometimes by several users, and the demand is expected to increase as the population grows.

There is still time to prevent the worst; the risk of a multidecade megadrought in the American West can be reduced if we reduce fossil-fuel emissions. But there can be little doubt that what was once thought to be a future threat is suddenly, catastrophically upon us.

(Christopher R. Schwalm is a research assistant professor of earth sciences at Northern Arizona University. Christopher A. Williams is an assistant professor of geography at Clark University. Kevin Schaefer is a research scientist at the National Snow and Ice Data Center)US Drought as of August 7, 2012
US Drought as of August 7, 2012Courtesy Mark Svoboda, National Drought Mitigation Center


43 percent melt: This NASA satellite image from July 8 shows 43 percent of the Greenland ice sheet was melting.
43 percent melt: This NASA satellite image from July 8 shows 43 percent of the Greenland ice sheet was melting.Courtesy NASA
Johnny Carson used to have a standard round of jokes for the summertime on his Tonight Show.

"How hot is it outside today? It's so hot (insert punchline)," was the standard humorous convention he would use.

NASA researchers have a new take on how hot it is this summer, and it's not that funny. Satellite photos taken this month over Greenland show that the massive ice sheet that covers almost all of the Arctic region island was now melting at some degree earlier this month. Like the tried-and-true diet ads in the back of magazines, NASA has before and after satellite images that show the extent of melting that happened.

The top image, complied from three satellite photos taken on July 8, show about 40 percent of the ice sheet's surface was melting. Areas that are pink show where melting is occurring. Areas that are white show non-melting ice and areas that are grey have no ice cover.

97 percent melt: This satellite image from July 12 shows the melt rate surging up to 97 percent.
97 percent melt: This satellite image from July 12 shows the melt rate surging up to 97 percent.Courtesy NASA
The bottom image, taken on July 12, shows a rapid acceleration of melting on the island, with 97 percent of the ice sheet melting. It's a surge in melting rates that scientists figure happens about once every 150 years. This month's data is the highest melting rate that NASA has seen in Greenland since satellite data has been collected for about 30 years.

A rare warm front stalling over Greenland is the cause of the high amount of melting and by the middle of the month, that front had moved on and things were getting back to normal. You can read the NASA press release about this weather event here.

While the brief massive melting is unusual, it's not a huge immediate threat to Greenland's ice sheet, which is some spots is more than two miles thick.

In other recent Greenland ice sheet news, a huge chunk of coastal ice broke off and is now adrift in the Atlantic Ocean earlier this month. Measuring 59 square miles, the ice sheet is twice the size of Manhattan. You can read more about that story here. Two years ago, an iceberg twice as big as this year's broke off from the same location. Experts say it's extremely rare to have two huge icebergs break loose in such a short amount of time.


Bone dry: Significant sections of the country are facing drought just weeks after the major weather stories were about heavy rains and flooding. What's going on?
Bone dry: Significant sections of the country are facing drought just weeks after the major weather stories were about heavy rains and flooding. What's going on?Courtesy Tomas Castelazo
It was just a few weeks ago we posted incredible pictures and video of devastating floods ripping through Duluth. Now, on a national scale, the weather story is drought. But how bad is it really?

Depends on where you live, but much of the Midwest is falling into drought conditions. It's bad, but not as wide spread as the peak of U.S. drought conditions from 1934. USA Today has an interesting toggle map that allows you compare today's conditions with that record drought.

Even earlier this summer, heavy rains in the Twin Cities had lockmasters along the Mississippi River shutting their gates to control fast-flowing river water. Now downstream, the Mississippi is approaching record-level lows. In some areas around Memphis, the river level has fallen 55 feet from highs set last summer. This CNN website report has interesting satellite images of the newly slimmed Mississippi compared to last year's look.

What do you think of this crazy weather? Share your thoughts here with other Buzz readers.


I visited to Fort Collins to help celebrate the 50th anniversary of the CSU Department of Atmospheric Sciences. A great celebration and an opportunity to see colleagues I haven't seen in many years.

On Saturday I drove through a section of the Cache La Poudre River to see some of the burnt scares from the High Park fire. The fire started on June 9 by a lightning strike and burned across 87,284 acres by early July, taking 259 homes. One person has died in the fire. It is the second-largest fire in Colorado's history and has cost about $30 million to fightHigh Park Fire impact on the Cache La Poudre River: A view of the Cache La Poudre River on July 14, 2012
High Park Fire impact on the Cache La Poudre River: A view of the Cache La Poudre River on July 14, 2012Courtesy Steve Ackerman

A recent rain washed the ash into the river, which now runs gun-powder black, as you can see in the photo. This is black color is consistent with the name Cache La Poudre. I have to wonder how this sediment will impact the fish in the water. This is an excellent river for trout.

Notice the burnt trees along the ridge line in the photo. Also notice the dead pine trees in the photo; a result of the pine beetle. The mountain pine beetles inhabit ponderosa, lodgepole, Scotch and limber pine trees and play an important role in the life of a forest. The black beetle attacks old or weakened trees which helps development of a younger forest. However, unusual hot, dry summers and mild winters have led to an epidemic. It would seem logical that these beetle damaged trees would increase fire risks as dead trees are flammable and likely to catch fire. But this might not be the case, indeed the dead trees may inhibit the spread of fires. The Yellowstone wildfire of 1988 provided forest ecologists with a method. Large crown fires can swept quickly through the forest spreading from tree tops. In the 1988 fire there were many trees killed and their needles burned off, but the standing dead tree trunks remained. New wildfires tend to slow and sometimes burn out when they reach standing dead forest. An interesting research topic!


Radiometers at Science Museum of Minnesota
Radiometers at Science Museum of MinnesotaCourtesy Patrick Hamilton
The Minneapolis-St. Paul International Airport reported a low at 6:00 a.m. this morning of 73 degrees F degrees while nearby Lakeville was at 57 – a 16 degree difference in only 20 miles. Said Paul Huttner, an MPR meteorologist, “…one of the biggest urban heat island effects today I have ever seen in 40+ years of watching and forecasting weather in the Twin Cities.”

Urban heat islands are regions of strong warming localized around the heart of a city with progressively lower temperatures as one travels away from the center – hence the name “heat island”. Urban heat islands exist because of large differences in land use, building materials, and vegetation between cities and their rural surroundings. In much of the world, cities are warming at twice the rate of outlying rural areas and so the frequency of urban heat waves is projected to increase with climate change through the 21st century.

Drs. Peter Snyder and Tracy Twine are in the midst of a four-year research project funded by the University of Minnesota’s Institute on the Environment and the College of Food, Agriculture, and Natural Resource Sciences to monitor the urban heat island of the Twin Cities. The project aims to improve understanding of the mechanisms contributing to urban heat islands with a goal of finding ways to lessen their effects through landscape design.

Snyder, Twine and two graduate students installed two instrument towers at the Science Museum on Monday as part of their urban heat island research project. One is on the white roof outside of the windows of Elements Café and the other is on a nearby black roof. Both are visible if you stand at the southwest corner of the plaza outside of the Café and look back at the museum. The two towers with their arrays of temperature sensors and radiometers will collect data at the museum for about four weeks, permitting Snyder and Twine to better characterize the interactions between different roof types and solar radiation in their urban heat island modeling work.


The June 29, 2012 derecho swept across from US from west of Chicago to the East Coast, leaving as many as 5 million households without power. The storm traveled at speeds of over 60 mph, with wind gusts approaching 80 mph. At least 22 people were killed.

A derecho (pronounced deh-RAY-cho, a Spanish word meaning “straight ahead”) is an hours-long windstorm associated with a line of severe thunderstorms. It is a result of straight-line winds, not the rotary winds of a tornado—hence its name. Derechos in the United States are most common in the late spring and summer (May through August).
Derecho climatology: The number of derecho windstorms occurring from 1994 to 2003 across the United States.
Derecho climatology: The number of derecho windstorms occurring from 1994 to 2003 across the United States.Courtesy Ackerman & Knox: Meteorology: Understanding the Atmosphere

The extreme winds of a derecho—up to 150 mph in the strongest storms—come about in the following way. Derechos are often associated with a quasi-stationary front in mid-summer. If the atmosphere just north of the front is very unstable, the front may trigger rapidly developing thunderstorms. A line of thunderstorms that forms in the vicinity of the stationary front can, via its cold downdrafts, drag down high-speed air from above. This can cause the high winds of a derecho.

At the same time, the high winds push the line of thunderstorms outward, causing it to bend or “bow.” This results in a bow echo image on weather radar. Once they get going, derechos can cover lots of territory—up to 1000 miles—and leave significant property damage in their wake, even flattening entire forests. In some cases, derechos wreak as much havoc as a hurricane or tornado. About 40% of all thunderstorm-related injuries and deaths occur because of derechos.


The issue:
About a month ago, a frack-sand mining operation near Grantsburg, WI, spilled some fine-grained sediment from a settling pond into a tributary of the St. Croix River. Local news media covered the story, and more details, for example, can be found in the Pioneer Press story by Dennis Lien.

So what’s the big deal?
Well, there are standards regarding water turbidity, which means that as a society we’ve decided that we don’t like cloudy water, at least in some settings and at some levels. For a naturally clear-water system like the St. Croix, increasing turbidity would alter the food chain at all levels. Algal primary producers rely on sunlight blocked by turbidity. Sight-based predation at the top of the food change would be altered. Benthic (bottom-dwelling) organisms that depend on coarse substrates could be smothered by siltation. Especially in the St. Croix, one of the last refugia for freshwater endangered mussel species, we must be on guard against too much fine sediment. And finally, where does the sediment end up? It’s filling up not only man-made reservoirs but also treasured natural lakes, iconically Lake St. Croix and Lake Pepin. These lakes are filling in with fine-grained sediment at about 3X and 10X their natural rates, respectively. (How do we know? See work done by the Museum’s St. Croix Watershed Research Station.)

Hey, it’s only a little bit...
Or was it? How much is a little? A little here, a little there, and a little more from over there -- it starts to add up. All water in a watershed runs downhill to the river, efficiently carrying both particles and dissolved materials. The river ultimately sees it all: all the disturbances, however seemingly minor, throughout the watershed. Rivers die a death of a thousand cuts. We have enough difficulty trying to control nonpoint sources of sediment and other pollutants. Stopping discharge of fine-grained materials from a mining operation is eminently fixable. It’s the right thing to do. Fortunately, all parties seem in agreement on this, including the mining company, which has repaired its leaky dike.


Tornadoes form in regions of the atmosphere that have abundant warm and moist air near the surface with drier air above, a change in wind speed and direction with height, and weather systems such as fronts that force air upward. The United States provides these three ingredients in abundance, so it is not surprising that the majority of the world’s reported tornadoes occur in the USA. Within the United States, tornadoes can occur in nearly every state and in every month of the year. Wisconsin has experienced tornadoes in every month except February. It is generally accepted that tornado season begins in the springtime— and that is now.

Tornado season is based on when the ingredients for severe weather come together in a particular place. Because a change in wind with height is closely related to the presence of a jet stream, tornado season moves north and south during the year with a jet stream. Tornado season peaks in March and April in the Southeast but not until July in the upper Midwest and Northeast. The deep South has a secondary peak in tornado occurrence in November.
Month of maximum tornado threat: The geographic distribution of the month of maximum tornado threat for the continental United States.
Month of maximum tornado threat: The geographic distribution of the month of maximum tornado threat for the continental United States.Courtesy Ackerman & Knox: Meteorology: Understanding the Atmosphere

Tornadoes can also happen at any time of day or night. However, they thrive on solar heating and in some cases the ability of warm, moist air at the surface to penetrate the capping inversion. Therefore, the most likely times for tornadoes are late afternoon or early evening. More than half of all U.S. tornadoes occur during the hours of 3:00 PM to 7:00 PM local time.


Atmospheric carbon dioxide concentration during the past 417,000 years
Atmospheric carbon dioxide concentration during the past 417,000 yearsCourtesy Wikipedia Commons
Skeptics of human-induced climate change have long pointed to a lag between an increase in temperature and a rise in atmospheric carbon dioxide at the end of the last Ice Age as suggesting that carbon dioxide is an effect of rising temperatures, not a cause. This lag, however, was based on evidence from only one place on Earth - ice core records from Antarctica.

A much more extensive study of paleo-temperature records from 80 sites around the world just published in Nature reveals that global temperature increases followed rises in the carbon dioxide concentration in the atmosphere. Carbon dioxide is a heat-trapping gas that can drive climate change. This study greatly substantiates climate scientists who point out that the enormous quantities of carbon dioxide that human activities are putting into the atmosphere will result in dramatic changes in global climate if they are not curtailed.


A composed satellite photograph of North America in orthographic projection.
A composed satellite photograph of North America in orthographic projection.Courtesy NASA
The March 30 issue Science summarized an article in a recent issue of Geophysical Research Letters with significant implications for human welfare.

Many climatologists have expected that extreme weather events will increase in frequency and intensity as human activities continue to increase the concentration of heat-trapping gases in the atmosphere. But how in particular could global warming exacerbate extreme weather?

A couple of processes have been identified that are impacting North America. First, the increasing melting of Arctic sea ice in summer means that a tremendous amount of solar energy that in the past was reflected back into space instead is absorbed by the ocean, which in turn warms the overlying atmosphere. Second, snow cover is melting earlier across much of North America and so more solar energy goes into drying out soils. These two processes – Arctic sea ice loss and the heating up and drying out of the interior of the continent – interact to slow the passage of weather systems from west to east across the continent, thereby strengthening their impacts.

Scientists are beginning to figure out how global warming can end up impacting our daily weather.