Making a Splash with Satellite Hydrology

It has long been suspected that dams and reservoirs provide extra moisture to the atmosphere and increase rainfall in the area around the reservoir. In December 2009, Faisal Hossain, of Tennessee Technological University, demonstrated that certain dams could make such rainfall events more extreme and frequent. The research catapulted Faisal and his research group — Sustainability, Satellites, Water and Environment (SASWE) — into the media spotlight, including a February 2010 interview with The Naked Scientists that aired live on the BBC and a feature in National Geographic News.

Hossain and his SASWE group — largely funded by NASA grants — also work to improve the ability of developing nations to monitor water resources that cross national boundaries. In April 2010, the group will be recognized by the National Association of Environmental Professionals with an education excellence award. WhatOnEarth caught up with Hossain to learn more about the group’s work and outreach efforts.

WhatOnEarth: What is satellite hydrology?

Hossain: We study the availability and movement of water on (surface), under (ground) and above (rain) earth’s surface by looking down from satellites in space. Today there are many satellites with instruments that can ‘read’ how much water might be flowing in a river or in the air, and also how wet the ground might be. Because Earth is 75 percent ocean and because land regions are too vast and expensive to completely survey, satellites provide the cheapest convenient and global way of monitoring the flow of water.

WhatOnEarth: What are some of the water issues your group is looking to solve? How?

Hossain: Today, more than 50 percent of the global surface flow is shared by multiple nations. Also, the numerous artificial reservoirs — more than 100,000 — built mostly in the upstream nations not only have vital implications on water supply for nations downstream, but they can also act as catalysts for increased flooding through heavier precipitation.

Without adequate treaties for trans-border cooperation, and without adequate knowledge of how dams alter climate, future water scarcity due to climate change and aging water infrastructure is likely to make nations more vulnerable to water disasters. SASWE is probably the first to demonstrate clearly the value of planned space-borne water measuring missions, such as the Global Precipitation Measurement (GPM) mission, and how they may improve disaster preparedness and environmental management.

WhatOnEarth: Does your research impact people’s lives?

Hossain: Many developing countries in Asia, Africa, and South America, are flood prone and yet unable to forecast floods due to the lack of basin-wide rainfall and stream flow data. Our group is helping to validate and improve NASA’s Global Flood Detection System, which uses rainfall data from NASA’s Tropical Rainfall Measuring Mission, and will also use NASA’s planned GPM mission.

For instance, Bangladesh is situated downstream of the Ganges-Brahmaputra-Meghna basin but does not receive any upstream river flow and rainfall information in real time from India during the critical monsoon season. Bangladeshi authorities measure river flow at staging points where the three major rivers enter Bangladesh and at other points downstream. On the basis of these data, it is possible to forecast flood levels in the interior and south of Bangladesh with only two to three days lead time. Theoretically, future NASA satellite missions could increase this lead time to anywhere from 7 to 14 days depending on the time for stream-flow to drain out from the Himalayas to the Bay of Bengal.

A longer forecasting range would improve decision-support tools that ingest these warnings. For example, 7- to 10-day forecasts are much more useful than daily forecasts in monsoon-affected Asian countries for informing farmers of the potential benefits of delayed sowing or early reaping of crops. A 21-day forecast is considered most ideal. Extended forecasts also assist in economic decision-making through early disbursement of loans to rehabilitate regions that might be affected by floods.

WhatOnEarth: How are public outreach and education part of your team’s mission?

Hossain: We are working with developing nations for climate change adaptation under a joint program with the Institute of Water Modeling (Bangladesh), Tennessee Technological University, and Ohio State University. In this program, staff from Bangladesh receive training each year on environmental management, stewardship and state-of-the-art satellite technology for adapting to climate change. The staff returns home and explores ways to implement the knowledge in their environment and to serve as a model for other developing nations.

Image Details: Water within a generic watershed boundary (red) can cross many political boundaries (top image). Both images are courtesy of Faisal Hossain, Tennessee Technological University.

— Kathryn Hansen, NASA’s Earth Science News Team

A Closer Look at Dust

                    A wide plume of dust blowing off the Saharan Desert toward the Canary Islands.  Credit: NASA Earth Observatory

Each summer, sandstorms lift millions of tons of dust from the Sahara, carrying plumes of it off the West Coast of Africa and over the Atlantic Ocean. Eric Wilcox, a researcher at NASA’s Goddard Space Flight Center, has been using data from NASA satellites to examine the impact such storms can have on rainfall patterns. Wilcox has a new paper about his findings in Geophysical Research Letters; Nature Geoscience also highlighted it in a recent issue. As a result, we sat down with Wilcox to discuss his new findings and some little-known details about dust.

WhatOnEarth: How does dust affect the atmosphere?

Wilcox: Well, we know that dust isn’t just a passive particle floating around. We know it can either absorb or scatter sunlight. Dust outbreaks surely cool the planet by reducing the amount of sunlight that reaches the surface. Likewise, we know dust can warm the atmosphere, although the magnitude is still uncertain.

WhatOnEarth: What causes a particle to absorb rather than scatter light?

Wilcox: It has to do with the color of the particle and, to some degree, the shape. We call this property the single scattering albedo, which is the probability that a photon of light will scatter versus getting absorbed. If the scatter is very high—say 0.99—then we’re confident that 99 out of 100 photons will scatter. If it’s lower, say 0.85, that means there’s a 15 percent chance that the proton will be absorbed.

WhatOnEarth: Where does Saharan dust fit in?

Wilcox: Some Saharan dust is quite bright and some is much darker. It depends on where the sand is coming from and what its mineralogy is like.

WhatOnEarth: Why does it matter if dust is absorbing light?

Wilcox: We’ve found that dust outbreaks, along with other factors, seem to be shifting tropical precipitation (which typically occurs in a narrow band where winds from the northern and southern hemispheres come together) northward by about four or five degrees, which is about 240 to 280 miles at the equator.

WhatOnEarth: Really? What does dust have to do with precipitation?

Wilcox: The main pathway for dust off the Sahara is usually well north of the band of tropical Atlantic rain storms. However, dust storms coincide  with a strong warming of the lower atmosphere, so the atmospheric circulation over the ocean responds to that warming by shifting wind and rainfall patterns northward during the summer. The rainfall responds to the passage of a dust storm even if the dust does not mix with the rain. 

WhatOnEarth: Will the upcoming Glory mission help you study this phenomenon? I know it has an instrument that will measure aerosols such as  dust? 

Wilcox: Definitely. Over bright reflective surfaces such as deserts — where it has been nearly impossible to distinguish aerosols from the surface — we’re at the point that any new information will be helpful. 

WhatOnEarth: What’s the significance of a northward migration of rainfall during dusty periods?

Wilcox: Certainly people local to the area have an interest in understanding how dust affects their rainfall patterns. The finding also lends support to an idea from one of my colleagues—Bill Lau—who studies the elevated heat pump.The idea is that aerosols from dust storms and air pollution actually affect monsoons. Space Flight Center.

Image Details: The lead image was acquired by the MODIS Land Rapid Response Team at NASA’s Goddard Space Flight Center in 2004.

— Adam Voiland, NASA’s Earth Science News Team

Revisiting the Iris Effect

A surprising paper published last summer suggested that a cloud-related feedback called the Iris Effect might counteract much of the warming associated with man-made greenhouse gases. NASA Langley’s Takmeng Wong (below) was one of several climate scientists who responded to the paper with a methodical inspection of its methods. Credit: Photograph STS109-325-2/Johnson Space Flight Center

A study published last summer by MIT’s Richard Lindzen and Yong-Sang Choi showed a curious thing: 15 years of observations of the tropics revealed that the Earth responds to rising sea surface temperatures by dumping more radiation to space. According to the authors, this feedback — dubbed the “iris effect” — would prevent much of the expected warming due to man-made greenhouse gas emissions. Further, Lindzen and Choi suggested that 11 major climate models had gotten this effect wrong. The paper found the Earth’s climate not nearly as sensitive to global warming as commonly thought.

A number of scientists, at NASA and elsewhere, immediately wondered how they could have missed such a major discrepancy between models and real-world observations. Their response to the paper provides an example of the back-and-forth, checking and re-checking that makes up the scientific process.

NASA Langley’s Takmeng Wong was one of the scientists surprised by the Lindzen and Choi paper. Wong works with data from the Clouds and the Earth’s Radiant Energy System (CERES) on NASA’s Terra satellite and from the Earth Radiation Budget Experiment (ERBE) satellite. Lindzen and Choi used ERBE data for their analysis, so Wong was naturally interested.

“When you see a surprising result, the first thing you do is go to the paper and see what they have,” Wong said. “We tried to do that and to reproduce their results. It’s part of the scientific process.” Being able to reproduce a specific result is an important building block of scientific knowledge.

Wong and Colorado State University’s Chris O’Dell eventually teamed up with Kevin Trenberth and John Fasullo, climate scientists at the National Center for Atmospheric Research, to publish a response. Their examination uncovered a number of deficiencies in Lindzen and Choi’s method, and found their result to be unstable and fragile. That analysis appeared this month in Geophysical Research Letters.

“We went to the same model data, to see if the observations are going one way and the models are going the other way,” Wong said. “When the analysis is done properly using robust scientific technique, what you find is that the observations and the models are consistent to within the uncertainty of the data.”

Wong summarized a few basic problems that led to the surprising finding: 

1. Lindzen and Choi focused on a number of selective time periods. But if the beginning and end points of those time periods are adjusted only slightly, their result falls apart.

2. The paper also treated the tropics as a closed system. In other words, it did not take into account any outside influences on what was happening in the tropics, such as the large amount of energy transport moving in and out of the tropics on ocean currents and atmospheric waves during events such as El Nino and La Nina.“The tropics is not a closed system,” Wong said. “But they treated it as such in the study.”

3. Lindzen and Choi took their result from the tropics and applied it globally, instead of using global data to study the link between global temperature increases and global outgoing radiation to space.

When questions arise that run counter to prevailing thought, Wong said, the only thing to do is take a closer look.

“You cannot make a scientific judgment,” Wong said, “until you’ve done the complete analysis.

Read more about the Iris Effect at the
NASA Earth Observatory

–Patrick Lynch, NASA’s Earth Science News Team

NASA Readies for Spring 2010 Ice Bridge Campaign

The following is a cross-post from our sister blog at NASA’s Operation Ice Bridge. For more frequent updates on the Ice Bridge mission, visit

Credit: John Sonntag/Wallops Flight Facility

In August 2008, NASA scientist John Sonntag, of NASA’s Wallops Flight Facility in Wallops Island, Va., captured this view of a small iceberg as it moved down the Narsarsuaq fjord in southern Greenland. “I spent about half an hour watching that little berg, which was in the process of disintegrating during the time I was watching,” Sonntag said. “It went from a complete, small berg to a collection of floating ice rubble within that small span of time. The place was so quiet that the noise of the berg softly coming apart was the only sound present.”

Sonntag’s observation took place during the 2008 NASA and Center for Remote Sensing of Ice Sheets (CReSIS) airborne deployment in Greenland. This spring, Sonntag and other scientists return to the Arctic for big picture and little picture views of the ice as part of NASA’s six-year Operation Ice Bridge mission — the largest airborne survey of Earth’s polar ice ever flown — now entering its second year. The project team is finalizing flight paths over Greenland’s ice sheet and surrounding sea ice, where scientists will collect measurements, maps and images from a suite of airborne instruments. Such information will help scientists extend the record of changes to the ice previously observed by NASA’s Ice, Cloud, and land Elevation Satellite (ICESat), while uncovering new details about land-water-ice dynamics.

NASA aircraft have made numerous science flights over Greenland, most recently during the spring 2009 Ice Bridge campaign and also in 2008 as part of the NASA/CReSIS deployment. Smaller-scale airborne surveys have been made by William Krabill, of NASA Wallops, and colleagues nearly every spring since 1991.

Visit the Operation Ice Bridge Web page throughout the spring 2010 campaign for news, images, and updates from the field. Flights from Greenland are scheduled to begin no sooner than March 22.

— Kathryn Hansen, NASA’s Earth Science News Team

Deep Thoughts on the Ocean and a Scientist's Responsibility

Oceanographer Josh Willis of NASA’s Jet Propulsion Laboratory was recently honored by the White House as a recipient of the Presidential Early Career Award for Scientists and Engineers (PECASE). Willis studies the ocean — particularly the height of the sea surface — with satellite data, though he also works with colleagues who put instruments below the surface of the water. By blending such measurements, he has already made a scientific mark in the study of sea level rise. We caught up with Josh — shown below with White House science advisor John Holdren and NASA deputy administrator Lori Garver — to discuss his inspiration, the importance of the ocean, and the necessity of communicating science.

WhatOnEarth: When you were a child, what did you want to be when you grew up? When did you decide you wanted to be an ocean scientist?

Josh Willis: When I was 9 or 10, I found a book about Einstein’s Theory of Relativity that my parents had lying around the house. I remember reading it and then peppering my parents with questions they couldn’t answer. (This was long before Google, mind you.) So for a long time, I wanted to be a physicist. A couple years of graduate school in physics convinced me otherwise, and I started studying oceanography at the Scripps Institution of Oceanography. Studying the ocean and climate appealed to me because I got to use all the physics and math I learned, but it was also closer to home and of practical importance to a lot of people. Plus, it’s just fun to say “oceanographer” whenever people ask me what I do.

WhatOnEarth: What is the best scientific paper you have written?

Willis: It’s tough to say. Sometimes the papers I think are important are different from the ones that other scientists remember best. But my papers on the causes of sea level rise — based on comparisons between satellite altimeter data, observations of ocean temperature changes, and changes in ocean mass measured by the GRACE satellite — were interesting and fun to write.

WhatOnEarth: What is the most important thing that few people know about the ocean?

Willis: The ocean is the silent martyr of global warming. We always think of global climate change in terms of the warming atmosphere, but it is actually the ocean that absorbs almost all of the extra heat and a whole lot of CO2. The warming contributes to sea level rise and changes ocean ecosystems, while the extra CO2 makes the ocean more acidic, threatening plankton and other tiny critters that make up the foundation of the oceanic food chain.

WhatOnEarth: Why do you feel compelled to talk to the public about your science?

Willis: Communicating our work is a really important part of doing science that most scientists sort of neglect. Figuring out new things about the world around us is only helpful if we communicate them to everyday people. Plus it’s fun and exciting to talk to non-scientists because the questions are often fun and interesting, and I come away feeling inspired and invigorated.

WhatOnEarth: What is the funniest or strangest question you’ve ever gotten?

Willis: I often get a chuckle out of the people who say that global warming is a vast conspiracy among scientists. Scientists love to prove each other wrong, and most of the time we can barely agree on simple questions like “why is the sky blue,” much less orchestrate a conspiracy.

WhatOnEarth: Is the PECASE award an affirmation or an inspiration for your career?

Willis: This is definitely a great honor and inspiration. When President Obama met with us, one of the first things he told us was how nice it was to honor a group of scientists still in the early stages of our careers. “All of you folks are younger than me!” he said. But he also made it clear that he expected a lot from us in the future. That’s a pretty big inspiration when the President tells you he’s expecting great things. And it’s a pretty big responsibility, too. I guess that means it’s probably time to get back to work now…

Mike Carlowicz, NASA’s Earth Science News Team

Up Close with Ice Bridge

NASA and partners are nearing the end of the 2009 Antarctic campaign of Operation Ice Bridge — a multi-year airborne survey to study Earth’s polar ice sheets, ice shelves and sea ice. Data collected from the DC-8 aircraft will help scientists monitor changes in West Antarctica and bridge the gap between the ICESat and ICESat-2 satellites. Also, the close-up look — not possible from satellites — will help scientists learn more about the region’s ice dynamics.

Ice Bridge scientist Seeyle Martin.  Credit: NASA

The detailed look with lasers and radar, sometimes from just 1,000 feet above the ice, is now returning a wealth of scientific information about the ice surface and what’s below. And to the human eye, the low-altitude view shows West Antarctica’s intricacies: the vast expanse of white giving way to deep crevasses and volcanoes, and sea ice resembling pancakes and oil slicks.

The 2009 Operation Ice Bridge campaign concludes no later than Nov. 21. Want to follow the remainder of the flights? Here’s how to connect:

  • Webisodes – Watch this series of YouTube videos for a behind-the-scenes look at Ice Bridge mission planning and flights in Antarctica.

  • Image gallery – Curious what pancake ice looks like or want to take a peek inside the DC-8? Check out the image gallery for photos added throughout the mission

  • Blog – Read about the campaign straight from the scientists and public affairs officers on site.

  • Twitter – Be among the first to know if a flight took off or if it was grounded due to weather, and discover the target of most flights — glacier, ice sheet or sea ice?

–Kathryn Hansen, NASA’s Earth Science News Team

Hydrology Takes the Cake at AGU

There’s a staggering amount of science presented every year at the American Geophysical Union meeting, Earth science’s equivalent of the post-season, prom, and a college reunion all rolled into one. This year, with more than 16,000 attendees and 15,815 abstracts on the docket, was no exception.

AGU groups all the abstracts into one of 27 categories. Hydrology garnered the most attention from scientists (12.2 percent of all abstracts) followed closely by Atmospheric Sciences (11.1 percent) and finally Volcanology, Geochemistry, and Petrology (8.0 percent). The full breakdown is below:

NASA, though best known for sending men to the moon and robots to Mars, had plenty of Earth science — including stories about black carbon, California’s carbon budget (and dwindling water supplies), greenhouse gases, and one of our Earth observing flagships — to add to the mix as well.

–Adam Voiland, NASA’s Earth Science News Team

Same Words But Different Meanings

Earth scientists milling around the lobby during coffee breaks at this year’s AGU had something unusual to mull over this year.  A phalanx of colorful posters, created by a visual communicator who describes herself as a note taker on steroids, adorned the lobby of the Moscone Center. Snippets from the illustrated notes offer a fascinating look into some of the brainstorming sessions that have taken place about communicating climate science. AGU intstalled the posters at a fitting time: it’s been a disorienting month for climate scientists who have watched seemingly specious charges of scientific malpractice become a major news item.

One of the posters — called Communicating with Congress (and Everybody Else) — brainstorms some of the pitfalls that make communicating climate science such a challenge. High on the list: jargon. Scientists use such a specialized language that it can be difficult for non-scientists — even for those of us who cover the topic regularly — to distill the meaning from certain scientific presentations or articles. Complicating matters more, there are some words that have distinctly different meanings to scientists and the public. The poster highlighted a handful of them. I’ve taken the liberty of elaborating upon and defining a few of them below. 

Did you know the difference?  Have any good examples to add to the list?

The Public: Spray cans that dispense a liquid mist, many of which damage Earth’s ozone layer.

Scientists: A suspension of any solid or liquid droplet in the atmosphere. Includes dust, soot, pollen, sea salt, sulfates and more. More details about aerosols. 

The Public: Harmful material that leaks from nuclear material and is used to battle cancer.
Scientists: Energy that comes from a source and travels through some material or space. Includes electromagnetic radiation such as radio waves, infrared light, visible light, ultraviolet light, and X-rays.  More details about
electromagnetic radiation.

The Public: Something over Antarctica that protects against cancer-causing light waves. 
Scientists: A molecule containing three oxygen atoms that functions as a harmful air pollutant near the surface, a greenhouse gas in the upper troposphere, and a buffer against ultraviolet radiation in the stratosphere. 
More details about ozone.

The Public: Willful manipulation of facts to suit political ideology.
Scientists: A term used to describe a statistical sample in which members of the sample are not equally likely to be chosen. Also a term used to describe the difference between an
estimator’s expectation and the true value of the parameter being estimated. For some scientific analyses, a certain degree of bias can actually be beneficial.

–Adam Voiland, NASA’s Earth Science News Team

Communicating Climate Change

Rigor. Not rigor mortis.

Those are two basic tenets of talking to the public about global warming, offered by Mark Serreze, director of the National Snow and Ice Data Center. He spoke at a Thursday morning session on “communicating climate” at the American Geophysical Union’s fall meeting in San Francisco.

The climate debate as carried out on cable news, over dinner tables and at the office these days is anything but dead. Serreze and a handful of other presenters at the session encouraged scientists to inject their scientific knowledge into this debate, especially at this critical moment for policy development to address climate change impacts. But, Serreze gently prodded, be sure to bring the scientific rigor, while leaving the calcified sciencese in the lab.

In past years a session like this might not have even appeared on the AGU schedule. No data-dense graphs were shown, no recent breakthroughs discussed. But its presence on the agenda – and a strong attendance – say something about the pitch and significance of the public climate debate right now.

Michael Mann, a Penn State climate scientist respected worldwide who, with colleagues, produced the now-famous “hockey stick” graph depicting recent drastic temperature changes, led off the session. Mann (pictured) has become a target of climate change deniers. Some of his personal emails were among those aired after hackers stole them off a computer server at the University of East Anglia Climatic Research Unit in England recently.

Mann said scientists for too long have been content to focus on their science and let any public debate of it play out on its own. He contends this strategy isn’t enough anymore, as a “well-funded disinformation effort” is still hard at work to discredit climate science and confuse the public.

“We’ve got to be out there, making the case,” Mann said. “These allegations are a distraction and are specious. We have to say that and at the same time use the opportunity to make the positive case.”

“The media alone cannot be expected to adequately defend the science and the scientists. It’s not their job. Our job is to make sure scientific truth is represented,” Mann said.

— Patrick Lynch, NASA’s Earth Science News Team
   Image Credit: Penn State University

The Uphill Road to Measuring Snow

One-sixth of the world’s population relies on melted snow for their freshwater, which means good estimates of snow are critical for making realistic predictions of a region’s water supply.

But measuring snow, especially the amount of water locked within that snow, challenges researchers across the globe. Why? The two means of estimating snow totals—weather modeling and satellite remote sensing—can vary as much as 30 percent.

Scientists like hydrologist Edward Kim of NASA’s Goddard Space Flight Center continue to seek ways to reconcile the gap between measurement results. Kim and colleagues Michael Durand (Byrd Polar Research Center), Noah Molotch (Univ. of Colorado), and Steve Margulis (UCLA) are wrapping up a short field campaign to measure snow at the Storm Peak Laboratory, perched atop Colorado’s famed mountain at Steamboat Springs.

Their aim is to test and improve the accuracy of satellite-based snow measurements. In the midst of the expedition, they’ve also snapped some breathtaking photos, such as this sun pillar to the right. Sun pillars are typically caused by sunlight reflecting off the surfaces of falling ice crystals associated with certain cloud types.

This post was adapted from NASA’s Earth Observatory. For more updates on the expedition, please visit the Notes From the Field blog.

–Adam Voiland, NASA’s Earth Science News Team