Saturday, February 9, 2013

The Great Meteor Procession of 1913

One hundred years ago today the Great Meteor Procession of 1913 occurred, a sky event described by some as "magnificent" and "entrancing" and which left people feeling "spellbound" and "privileged". Because one had to be in a right location, outside, and under clear skies, only about 1,000 people noted seeing the procession. Lucky sky gazers -- particularly those near Toronto, Canada -- had their eyes drawn to an amazing train of bright meteors streaming across the sky, in groups, over the course of a few minutes. A current leading progenitor hypothesis is that a single large meteor once grazed the Earth's atmosphere and broke up. When the resulting pieces next encountered the Earth, they came in over south-central Canada, traveled thousands of kilometers as they crossed over the northeastern USA, and eventually fell into the central Atlantic ocean. Pictured above is a digital scan of a halftone hand-tinted image by the artist Gustav Hahn who was fortunate enough to witness the event first hand. Although nothing quite like the Great Meteor Procession of 1913 has been reported since, numerous bright fireballs -- themselves pretty spectacular -- have since been recorded, some even on video.

Tuesday, February 5, 2013

Mariner 10's Portrait of Venus

On Feb. 5, 1974, Mariner 10 took this first close-up photo of Venus.

Made using an ultraviolet filter in its imaging system, the photo has been color-enhanced to bring out Venus's cloudy atmosphere as the human eye would see it. Venus is perpetually blanketed by a thick veil of clouds high in carbon dioxide and its surface temperature approaches 900 degrees Fahrenheit.

Launched on Nov. 3, 1973 atop an Atlas-Centaur rocket, Mariner 10 flew by Venus in 1974.

Image Credit NASA

Monday, February 4, 2013

The "Land Breeze"

Example of what radar can detect in fair weather--the "land breeze" boundary--that often pushes off the peninsula during the night. Boaters can use this information as winds near the coast will be light westerly, but once past the boundary, winds can be much more gusty.

Sunday, February 3, 2013

In the Center of the Trifid Nebula

Clouds of glowing gas mingle with dust lanes in the Trifid Nebula, a star forming region toward the constellation of the Archer (Sagittarius). In the center, the three prominent dust lanes that give the Trifid its name all come together. Mountains of opaque dust appear on the right, while other dark filaments of dust are visible threaded throughout the nebula. A single massive star visible near the center causes much of the Trifid's glow. The Trifid, also known as M20, is only about 300,000 years old, making it among the youngest emission nebulae known. The nebula lies about 9,000 light years away and the part pictured here spans about 10 light years. The above image is a composite with luminance taken from an image by the 8.2-m ground-based Subaru Telescope, detail provided by the 2.4-m orbiting Hubble Space Telescope, color data provided by Martin Pugh and image assembly and processing provided by Robert Gendler.

Tornadoes producing damage on the ground detectible by dual-polarization radar

This is kind of old, 2010, but it seemed to cool to pass up. From a NSSL article.

Recent analysis of data from NOAA NSSL’s prototype dual-polarization radar during a significant tornado outbreak in central Oklahoma this past spring showed debris from a damaging tornado.  This critical information can help a forecaster confirm the presence of a rain-wrapped tornado, or a tornado at night causing damage on the ground.
Dual-polarization technology can help detect debris from a damaging tornado
Current NOAA National Weather Service (NWS) radars send a horizontal electromagnetic wave field into the sky.  When the wave field bounces off an object in its path, it is reflected back to the radar and gives a measurement of the horizontal size of that object.  Dual-polarization radar sends both horizontal and vertical electromagnetic wave fields, giving a forecaster a measure of the size and shape of the object.  Combining and comparing these measurements can categorize rain, hail, snow, birds, insects, and tornado debris.  All NOAA National Weather Service radars will be upgraded with dual-polarization technology beginning in late 2010.
NSSL researchers studying the tornado outbreak confirmed four rotation signatures in the radar velocity data.  Tornado warnings had been issued based on this information.  However, these measurements cannot confirm tornadoes are causing damage on the ground because the radar beam is above ground level.
NSSL research showed dual-polarization radar data identifies debris signatures differently from radar echoes.   Leaves, shingles or insulation are randomly oriented, while precipitation echoes behave fairly predictably.
Tornado debris signatures were identified by researchers in the dual-polarized data from the May 10, 2010 outbreak indicating a rain-wrapped tornado was producing damage on the ground.  This tornado killed two people.
NSSL developed, tested and evaluated dual-polarization technology over the past 25 years, culminating in a demonstration project that convinced the NWS to upgrade all their radars with this technology.