Study finds severe climate jeopardizing Amazon forest

Terra Daily: An area of the Amazon rainforest twice the size of California continues to suffer from the effects of a megadrought that began in 2005, finds a new NASA-led study. These results, together with observed recurrences of droughts every few years and associated damage to the forests in southern and western Amazonia in the past decade, suggest these rainforests may be showing the first signs of potential large-scale degradation due to climate change.

An international research team led by Sassan Saatchi of NASA's Jet Propulsion Laboratory, Pasadena, Calif., analyzed more than a decade of satellite microwave radar data collected between 2000 and 2009 over Amazonia. The observations included measurements of rainfall from NASA's Tropical Rainfall Measuring Mission and measurements of the moisture content and structure of the forest canopy (top layer) from the Seawinds scatterometer on NASA's QuikScat spacecraft.

The scientists found that during the summer of 2005, more than 270,000 square miles (700,000 square kilometers, or 70 million hectares) of pristine, old-growth forest in southwestern Amazonia experienced an extensive, severe drought. This megadrought caused widespread changes to the forest canopy that were detectable by satellite. The changes suggest dieback of branches and tree falls, especially among the older, larger, more vulnerable canopy trees that blanket the forest....

Bamboo and ferns in the Amazon, shot by Tadd and Debbie Ottman, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

NASA chases climate change clues into the stratosphere

Science Daily: Starting this month, NASA will send a remotely piloted research aircraft as high as 65,000 feet over the tropical Pacific Ocean to probe unexplored regions of the upper atmosphere for answers to how a warming climate is changing Earth.

The first flights of the Airborne Tropical Tropopause Experiment (ATTREX), a multi-year airborne science campaign with a heavily instrumented Global Hawk aircraft, will take off from and be operated by NASA's Dryden Flight Research Center at Edwards Air Force Base in California. The Global Hawk is able to make 30-hour flights.

Water vapor and ozone in the stratosphere can have a large impact on Earth's climate. The processes that drive the rise and fall of these compounds, especially water vapor, are not well understood. This limits scientists' ability to predict how these changes will influence global climate in the future. ATTREX will study moisture and chemical composition in the upper regions of the troposphere, the lowest layer of Earth's atmosphere. The tropopause layer between the troposphere and stratosphere, 8 miles to 11 miles above Earth's surface, is the point where water vapor, ozone and other gases enter the stratosphere.

Studies have shown even small changes in stratospheric humidity may have significant climate impacts. Predictions of stratospheric humidity changes are uncertain because of gaps in the understanding of the physical processes occurring in the tropical tropopause layer. ATTREX will use the Global Hawk to carry instruments to sample this layer near the equator off the coast of Central America.

"The ATTREX payload will provide unprecedented measurements of the tropical tropopause," said Eric Jensen, ATTREX principal investigator at NASA's Ames Research Center in Moffett Field, Calif. "This is our first opportunity to sample the tropopause region during winter in the northern hemisphere when it is coldest and extremely dry air enters the stratosphere."...

NASA In its new white-and-blue NASA livery, an early development model of the Global Hawk unmanned aircraft rests on the ramp at the Dryden Flight Research Center, Edwards AFB, Calif. Photo Credit: NASA

NASA's Operation IceBridge data brings new twist to sea ice forecasting

NASA: Shrinking Arctic sea ice grabbed the world's attention again earlier this year with a new record low minimum. Growing economic activity in the Arctic, such as fishing, mineral exploration and shipping, is emphasizing the need for accurate predictions of how much of the Arctic will be covered by sea ice. Every June, an international research group known as the Study of Environmental Arctic Change (SEARCH) publishes a summary of the expected September Arctic sea ice minimum known as the Sea Ice Outlook. The initial reports and monthly updates aim to give the scientific community and public the best available information on sea ice.

Researchers rely on models that use estimated ice thickness data and simulated atmospheric conditions to forecast how sea ice will change during the summer. For the first time, near real-time ice thickness data obtained by NASA's Operation IceBridge has been used to correct a forecast model's initial measurements, which could lead to improved seasonal predictions.

In a paper published last month in the journal Geophysical Research Letters, Ron Lindsay, IceBridge science team member and Arctic climatologist with the Polar Science Center at the University of Washington in Seattle, outlined efforts to use IceBridge data to improve the accuracy of seasonal sea ice forecasts. Lindsay and colleagues used a new quick look sea ice data product that IceBridge scientists released before the end of the Arctic campaign earlier this year. The quick look data, intended for use in time-sensitive applications like seasonal forecasts, supplements the final sea ice data product typically released roughly six months after the campaign. By using new data processing techniques, IceBridge scientists were able to publish the quick look measurements in a matter of weeks. "The idea was to make the data available for anyone to use for the Sea Ice Outlook," said sea ice scientist Nathan Kurtz of NASA's Goddard Space Flight Center in Greenbelt, Md.

The work outlined in Lindsay's paper marks the first use of IceBridge quick look data in an ensemble sea ice forecast (computer) model. "An ensemble forecast is where you run a single forecast model many different times," said Lindsay. In this case, they ran the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) model seven times using conditions from previous summers. PIOMAS uses sea ice extent, the area of sea containing sea ice, and atmospheric data to simulate ice and ocean conditions....

A Digital Mapping System (DMS) mosaic of Arctic sea ice. The dark areas are leads, or open areas of water. Identifying leads is one of the necessary steps in preparing IceBridge’s quick look sea ice thickness data product. Credit: NASA / DMS team

Plant stress paints early picture of drought

Kathryn Hansen in Seed Daily via NASA: In July 2012, farmers in the U.S. Midwest and Plains regions watched crops wilt and die after a stretch of unusually low precipitation and high temperatures. Before a lack of rain and record-breaking heat signaled a problem, however, scientists observed another indication of drought in data from NASA and NOAA satellites: plant stress.

Healthy vegetation requires a certain amount of water from the soil every day to stay alive, and when soil moisture falls below adequate levels, plants become stressed. Scientists with the U.S. Department of Agriculture's Agricultural Research Service (USDA-ARS) have developed a way to use satellite data to map that plant stress. The maps could soon aid in drought forecasts, and prove useful for applications such as crop yield estimates or decisions about crop loss compensation.

"Crop drought monitoring is of high practical value, and any advance notice of drought conditions helps the farmer make practical decisions sooner," says Steve Running, an ecologist at University of Montana in Missoula.

A new animation of plant stress (top) shows how drought evolved across the United States from January 2010 through September 2012. In spring 2010, satellites measured cool leaf temperatures, indicating healthy plants and wetter-than-average conditions (green), over many areas across the country.

By summer 2011, satellites saw the warming of stressed vegetation, indicating significantly lower-than-usual water availability (red) in many areas, most notably in Texas. Crops were either dead or would soon be dead….

Plant stress on on August 28, 2012, indicated significant drought in the U.S. Midwest. Credit: NASA/Goddard Scientific Visualization Studio/USDA-ARS

Climate models project increase in US wildfire risk

NASA: Scientists using NASA satellite data and climate models have projected drier conditions likely will cause increased fire activity across the United States in coming decades. Other findings about U.S. wildfires, including their amount of carbon emissions and how the length and strength of fire seasons are expected to change under future climate conditions, were also presented Tuesday at the annual meeting of the American Geophysical Union in San Francisco.

Doug Morton of NASA's Goddard Space Flight Center in Greenbelt, Md., presented the new analysis of future U.S. fire activity. The analysis was based on current fire trends and predicted greenhouse gas emissions.  "Climate models project an increase in fire risk across the U.S. by 2050, based on a trend toward drier conditions that favor fire activity and an increase in the frequency of extreme events," Morton said.

The analysis by Morton and colleagues used climate projections, prepared for the Fifth Assessment Report of the United Nations Intergovernmental Panel on Climate Change, to examine how dryness, and therefore fire activity, is expected to change.

The researchers calculated results for low and high greenhouse gas emissions scenarios. In both cases, results suggest more fire seasons that are longer and stronger across all regions of the U.S. in the next 30-50 years. Specifically, high fire years like 2012 would likely occur two to four times per decade by mid-century, instead of once per decade under current climate conditions.

Through August of this year, the U.S. burned area topped 2.5 million hectares (6.17 million acres), according to a fire emissions database that incorporates burned area estimates produced from observations by the Moderate Resolution Imaging Spectroradiometer instruments on NASA's Aqua and Terra satellites. That is short of the record 3.2 million hectares (7.90 million acres) burned in 2011, but exceeds the area burned during 12 of the 15 years since record keeping began in 1997. This and other satellite records, along with more refined climate and emissions models, are allowing scientists to tease out new information about fire trends....