La Nina, the periodic cooling in the surface waters of the Central and Eastern Pacific that enhances hurricane formation in the Atlantic and can affect weather across the United States, appears to be fading away.

Climatologists at the NOAA Climate Prediction Center say sea surface temperatures are rising out there, and approaching what they regard as "neutral" conditions in the La Nina/El Nino cycle, known as the "El Nino Southern Oscillation," or ENSO.

Here's more. And, you can watch the cool (blue) waters in the central Pacific warming up (yellow and tan) in the animation above, which is based on satellite observations of the Pacific during the past few months.

This departing La Nina has been credited (or blamed) for the drought that has plagued the West and the Southeast (including southeastern Maryland) since last summer, and for the mild winter, which brought just 8.5 inches of snow to Baltimore. It also played a role in the heavy snows in the upper Midwest and New England.

La Nina is also believed to facilitate Atlantic hurricane formation, but last year's hurricane season was only slightly more active than the long-term averages. Forecasters will be watching this La Nina's final months for any possible lingering influence it might have over this year's hurricane formation.

Although La Ninas can often be followed by El Nino conditions, it is also possible for "ENSO neutral" conditions - more or less average sea-surface temperatures - to persist for a time. Here is a link to NOAA's FAQ page on El Nino and La Nina.  

Posted by Frank Roylance at 10:32 AM | Permalink | Comments (0)
                    

A NASA study on rainfall has used satellite data to discover that, in the Southeast at least, air pollution gives summertime storms an extra "kick," producing a tendency for more rain during the work week than on weekends.

The key seems to be the particulate matter in air pollution from cars, factories and other workday sources. Water vapor condenses around these "seeds," and fuels more intense storms, which drop more rain.

You can read more about it here.

Posted by Frank Roylance at 9:51 AM | Permalink | Comments (0)
                    

As the mercury at The Sun this morning creeps toward 50 degrees, it seems safe to talk a bit about snow. Someone has asked whether lake-effect snow - the sort that has swept off Lake Ontario this winter and buried parts of western New York State - could occur on a body of water the size of the Chesapeake Bay.

The short answer is yes. It's been studied and deemed possible. But it is, apparently very rare. Here's a clip from the Virginia Pilot on an event in 1996. Researcher Crosby Savage, at North Carolina State University, has even found a radar image of such an event in 1999. The target that day was Norfolk.

Lake-effect (or "bay-effect") snow occurs when cold winds sweep across large bodies of relatively warm, open water. Along the Great Lakes, blasts of arctic air blow across the open lakes, pick up moisture, which is then lifted higher by the higher terrain on the lee of the lakes - Ohio, Pennsylvania and New York mostly. As it rises, the air cools, and the moisture condenses, freezes and falls as snow.

The Chesapeake is smaller than the Great Lakes, of course. And the surrounding terrain - especially on the lee side in a north wind - is generally flat. But scientists have concluded the conditions are sufficient to sustain a bay-effect snow.

To read more than anyone could possibly want to read on the topic, click here.  And here.

Thanks to AccuWeather for the links.

Posted by Frank Roylance at 10:03 AM | Permalink | Comments (0)
                    

The southern winter is drawing to a close, and that means the annual destruction of the ozone layer in the upper atmosphere over the South Pole is peaking. NASA has posted a new image showing the ozone hole as satellite sensors found it late last week.

Scientists discovered 20 years ago that the release of man-made chlorofluorocarbons (CFCs) into the atmosphere was catalyzing the destruction of ozone molecules. And the losses were greatest at the South Pole, where they amounted to a "hole."

High-altitude ozone is critical to life on the surface of the planet because it absorbs ultraviolet radiation from the sun, protecting exposed tissues from possible genetic damage - damage that can cause cancers and other harm to life forms from ocean plankton to people.

Continued ozone damage was affecting the polar regions first, but would eventually erode the ozone layer everywhere, enough to pose increasing health threats in the temperate zones where most people - most life forms - live.

International treaties in 1987 led to the phase-out of CFCs in refrigerants and aerosol propellants, and their replacement by more environmentally friendly materials.

Scientists in the nearly 20 years since have been on the lookout for signs the global actions have had some beneficial effect. Happily, they now say the long-term decline in the ozone layer globally has at least halted, and the damage may be healed (or at least back to 1980 levels) in the coming decades - well within the lives of our children and grandchildren. Here's a NASA release on the subject, noting that the best explanation for the gains is the ban on CFCs.

It's great to hear that human societies can learn about and understand a global environmental threat, and take concerted action - even when the payoff may be years or decades away.

Posted by Frank Roylance at 9:30 AM | Permalink | Comments (0)
                    

Here's the latest on global warming research from the National Center for Atmospheric Research (NCAR). Read it, read the news stories about a week of heavy rain just north of here, and weep.

BOULDER — Storms will dump heavier rain and snow around the world as Earth's climate warms over the coming century, according to several leading computer models. Now a study by scientists at the National Center for Atmospheric Research (NCAR) explains how and where warmer oceans and atmosphere will produce more intense precipitation. The findings recently appeared in Geophysical Research Letters, a publication of the American Geophysical Union.

The greatest increases will occur over land in the tropics, according to the study. Heavier rain or snow will also fall in northwestern and northeastern North America, northern Europe, northern Asia, the east coast of Asia, southwestern Australia, and parts of south-central South America during the 21st century.

"The models show most areas around the world will experience more intense precipitation for a given storm during this century," says lead author Gerald Meehl. "Information on which areas will be most affected could help communities to better manage water resources and anticipate possible flooding."

NCAR authors Meehl, Julie Arblaster, and Claudia Tebaldi analyzed the results of nine atmosphere-ocean global climate models to explain the physical mechanisms involved as intensity increased. Precipitation intensity refers to the amount of rain or snow that falls on a single stormy day.

Both the oceans and the atmosphere are warming as greenhouse gases build in the atmosphere. Warmer sea surfaces boost evaporation, while warmer air holds more moisture. As this soggy air moves from the oceans to the land, it dumps extra rain per storm.

Though water vapor increases the most in the tropics, it also plays a role in the midlatitudes, according to the study. Combined with changes in sea-level pressure and winds, the extra moisture produces heavier rain or snow in areas where moist air converges.

In the Mediterranean and the U.S. Southwest, even though intensity increases, average precipitation decreases. The authors attribute the decrease to longer periods of dry days between wet ones. The heavier rain and snow will most likely fall in late autumn, winter, and early spring, while warmer months may still bring a greater risk of drought.

The Department of Energy and the National Science Foundation funded the research. NCAR’S primary sponsor is the National Science Foundation. Opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of the National Science Foundation.

Posted by Frank Roylance at 1:20 PM | Permalink | Comments (0)
                    

Ophelia's storm clouds will likely spoil the view for most Marylanders, but if you're far enough north or west and out from under the hurricane's cloud deck, you may get a chance to see the Northern Lights tonight. Here's a look at the clouds, from space.

More blasts yesterday from active sunspots crossing the sun's disk have sent clouds of solar particles and magnetic energy speeding toward the Earth. They are expected to begin interacting with the planet's atmosphere as soon as tonight, producing displays of Northern Lights. You'll need clear, dark skies and a view of the northern sky. You can read more about it by clicking here.

It's been an active week on the sun. Lots of folks around the world have been snapping photos of the Northern Lights for days. Here's a gallery of their work.

Posted by Frank Roylance at 12:53 PM | Permalink | Comments (0)