When it rains, it pours

Study estimates rate of intensification of extreme tropical rainfall with global warming.

A warm rain will fall

Global warming’s effect on rainfall in general is relatively well-understood: As carbon dioxide and other greenhouse gases enter the atmosphere, they increase the temperature, which in turn leads to increases in the amount of water vapor in the atmosphere. When storm systems develop, the increased humidity prompts heavier rain events that become more extreme as the climate warms. 

Scientists have been developing models and simulations of Earth’s climate that can be used to help understand the impact of global warming on extreme rainfall around the world. For the most part, O’Gorman says, existing models do a decent job of simulating rainfall outside the tropics — for instance, in mid-latitude regions such as the United States and Europe. In those regions, the models agree on the rate at which heavy rains intensify with global warming.

However, when it comes to precipitation in the tropics, these models, O’Gorman says, are not in agreement with one another. The reason may come down to resolution: Climate models simulate weather systems by dividing the globe into a grid, with each square on the grid representing a wide swath of ocean or land. Large weather systems that span multiple squares, such as those that occur in the United States and Europe in winter, are relatively easy to simulate. In contrast, smaller, more isolated storms that occur in the tropics may be trickier to track. 

First Planets Found Around Sun-Like Stars in a Cluster

PASADENA, Calif. -- NASA-funded astronomers have, for the first time, spotted planets orbiting sun-like stars in a crowded cluster of stars. The findings offer the best evidence yet that planets can sprout up in dense stellar environments. Although the newfound planets are not habitable, their skies would be starrier than what we see from Earth.

The starry-skied planets are two so-called hot Jupiters, which are massive, gaseous orbs that are boiling hot because they orbit tightly around their parent stars. Each hot Jupiter circles a different sun-like star in the Beehive Cluster, also called the Praesepe, a collection of roughly 1,000 stars that appear to be swarming around a common center. 

The Beehive is an open cluster, or a grouping of stars born at about the same time and out of the same giant cloud of material. The stars therefore share a similar chemical composition. Unlike the majority of stars, which spread out shortly after birth, these young stars remain loosely bound together by mutual gravitational attraction. 

"We are detecting more and more planets that can thrive in diverse and extreme environments like these nearby clusters," said Mario R. Perez, the NASA astrophysics program scientist in the Origins of Solar Systems Program. "Our galaxy contains more than 1,000 of these open clusters, which potentially can present the physical conditions for harboring many more of these giant planets." 

The two new Beehive planets are called Pr0201b and Pr0211b. The star's name followed by a "b" is the standard naming convention for planets. 

"These are the first 'b's' in the Beehive," said Sam Quinn, a graduate student in astronomy at Georgia State University in Atlanta and the lead author of the paper describing the results, which was published in the Astrophysical Journal Letters. 

Volcano and Waterspout, Hawaii

Photograph by Steve and Donna O’Meara, National Geographic

The eruption of Hawaii’s Kilauea volcano inspires the formation of a waterspout in this undated photo.

Waterspouts can emerge the way traditional tornadoes do, but not always. Many are created

when near-surface winds suddenly change direction under a cloud that is producing a growing updraft. Unlike a tornado, a waterspout vortex and funnel cloud are created from the ground, or water, up.

Volcano Lightning, Iceland

Photograph by Sigurdur H. Stefnisson, National Geographic

Lightning cracks during an eruption of Iceland’s Eyjafjallajökull volcano in 2010.

The eruption’s ash clouds delayed European air travel for nearly a week.

Storms over volcanoes contain the same ingredients as storms over your hometown—water droplets, ice, and occasionally hail. The interaction of all of these elements creates an electrical charge that sparks lightning. Active craters add ash to the mix.

(Related: “Iceland Volcano Pictures: Lightning Adds Flash to Ash” and “Pictures: Volcano Lightning, Illuminated.”)

For an in-depth exploration of extreme weather events around the world, read National Geographic magazine's September feature "Weather Gone Wild."

Flooding and Drought in Etosha Pan

Outside of the Sahara, the driest country in Africa is Namibia. Although flooding is familiar in the country’s far eastern Caprivi Strip, most of Namibia is vulnerable to prolonged drought. On average, the country receives just 258 millimeters (10 inches) of rain per year, though annual rainfall amounts can vary considerably.
One place that gives an indication of Namibia’s precipitation is Etosha Pan. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured these images on July 30, 2009; July 31, 2010; July 31, 2011; and July 31, 2012. All of the images use a combination of infrared and visible light to increase the contrast between water and land. Water varies in color from electric blue to navy, with darker shades indicating deeper water. Vegetation, even sparse vegetation, appears green. Burnt orange indicates burn scars from fires.
Today, Etosha is a saltpan, but between 2 and 10 million years ago, it was a lake fed by the Kunene (Cunene) River. Changes in land surface features re-routed the Kunene, causing it to flow directly into the Atlantic Ocean. The water gradually evaporated, and the lake hasn’t reached anything like its old capacity since. Still, generous rains can sometimes leave Etosha Pan partially filled.
Etosha Pan has two basic seasons: wet and dry. The rainy season may begin as early as November and last as late as May. In the months that follow, the lake gradually dries up. Spring begins in September. Temperatures rise and water holes shrink.
The year-to-year contrast between these images is striking. Water sprawls over most of the pan in 2009 and 2011, but only minimal amounts appear in 2010 and 2012. Water levels generally drop through July, but how much water is left in and around the pan depends on how generous rains were in the preceding wet season. The years 2009 through 2012 showed a mix of unusually wet and unusually dry conditions, including flooding in 2011.
Even by Namibia’s normally arid standards, the Etosha region was parched in July 2012, and the Namibian government pledged aid to drought-stricken regions. According to the U.S. Foreign Agricultural Service, below-normal precipitation plagued this region from early April to late June. By mid-July 2012, most of the country had not seen rain for more than 25 days.

1.      References

2. Game-Reserve.com. Etosha National Park, Namibia.
3. Kunene correspondent. (2012, July 31) Kunene welcomes govt drought relief. AllAfrica.com.
4. United Nations Environment Programme. (2008). Africa: Atlas of Our Changing Environment. Division of Early Warning and Assessment, United Nations Environment Programme, Nairobi, Kenya.
5. Warren, A. Etosha: From Sand to Sea. PBS: The Living Edens.

NASA images courtesy LANCE MODIS Rapid Response Team at NASA GSFC. Caption by Michon Scott.

Instrument: 

Aqua - MOD

Probing the Electric Space Around Earth

They were the subject of perhaps the first scientific discovery of the Space Age, and yet we still don't know much about them. The radiation belts that surround Earth are home to killer electrons, plasma waves, and intense electrical currents that can disrupt and destroy the electronics on satellites. But the behavior of the Van Allen Belts—named for James Van Allen, who led the team that discovered them in 1958—is wildly unpredictable.
This artist's conception shows the radiation belts (green), which are two doughnut-shaped (torus) regions full of high-energy particles that fill the near-space around Earth. The blue and red lines between and around the belts depict the north and south polarity of the planet’s magnetic field. The inner belt, a blend of protons and electrons, can reach down as low as 1,000 kilometers (600 miles) in altitude. The outer belt, comprised mainly of energetic electrons, can swell to as much as 60,000 kilometers (37,000 miles) above Earth’s surface. Both rings extend to roughly 65 degrees north and south latitude.
The radiation belts were discovered during the flight of the very first American satellite. Van Allen and colleagues had installed a Geiger-Müller tube on Explorer 1 to detect cosmic rays, and as the satellite made its eccentric orbit around the Earth, the readings periodically went off the top of the counter’s scale. It happened again during the flight of Explorer 3 several months later. Several followup missions proved that the space around Earth was not empty, but instead enriched with electrons, protons, and energy created by interactions between Earth's magnetic field (or magnetosphere), the solar wind, and (occasionally) cosmic rays arriving from beyond the solar system.
Fifty-four years later, NASA has embarked on a missions designed specifically to understand the space weather in the dynamic and erratic Van Allen Belts. At 4:05 a.m. Eastern Daylight Time on August 30, 2012, the Radiation Belt Storm Probes (RBSP) were launched into orbit on a United Launch Alliance Atlas V rocket that lifted off from Cape Canaveral Air Force Station in Florida. (Watch video of the launch here.) The Johns Hopkins University Applied Physics Laboratory (APL) built and will operate the twin RBSP spacecraft for NASA’s Living With a Star program.
The identical twin spacecraft will fly in separate orbits across the inner and outer Van Allen radiation belts. The mission is starting near the height of the Sun’s 11-year cycle, or solar maximum. Activity on the sun influences the behavior of the radiation belts, though scientists are puzzled by that behavior. Sometimes a solar storm can swell the belts with particles and energy, creating havoc for Earth-orbiting satellites by accelerating electrons (aka, “killer electrons”) and creating electrical currents. Other times, the radiation belts grow very calm and depleted during Sun storms. Occasionally, no change is detected at all.
The RBSP satellites are designed to observe how and when killer electrons are energized, to sample the electrical and magnetic fields in Earth’s space, to count particles, and detect plasma waves of different frequencies. The ultimate goal is to improve the prediction of space weather; that is, how solar activity can cause geomagnetic storms that upset telecommunications and electronics.

1.      Further Reading

2. Carlowicz, M., and Lopez, R. (2002) Storms from the Sun: The Emerging Science of Space Weather. The Joseph Henry Press. Accessed August 30, 2012.
3. Johns Hopkins Applied Physics Laboratory (n.d.) Radiation Belt Storm Probes Accessed August 30, 2012.
4. NASA (2012, July 18) The Electric Atmosphere: Plasma Is Next NASA Science Target. Accessed August 30, 2012.
5. NASA (n.d.) RBSP News. Accessed August 30, 2012.
6. Science@NASA (2012) ScienceCasts: The Radiation Belt Storm Probes. Accessed August 30, 2012.

Image by T. Benesch and J. Carns for the NASA Science Mission Directorate. Caption by Mike Carlowicz.

Instrument: 

Model