The last two days it has been raining and cold with temperatures in the 30s. This is my least favorite weather, so we didn't get out to exercise. Today it is still chilly and there is a dusting of snow -- but the sun is out and temperatures are supposed to rise to the 40s. So we will definitely get out to enjoy the sunshine!
For today's blog posting I checked in with NASA's Home Observatory webpage at
http://earthobservatory.nasa.gov/.
NASA images by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Caption by Adam Voiland.
On April 5th Spring arrived in the United States, but that did not stop a
winter storm from dumping several inches of snow across much of the
Upper Midwest and the Northeast.
NASA Earth Observatory images by Jesse Allen with data from (LAADS). Caption by Mike Carlowicz.
One year after snow surveyors stood on a dusty mountainside in
California and reported that snow-water content was just 5 percent of
normal (bottom photo above), the situation in the Sierra Nevada range is much improved (top photo above). But
it is still not normal.
The California Department of Water Resources (DWR) reported on March
30, 2016, that snow cover in the mountains was 87 percent of the
long-term average. Snow that falls in the mountains is often powdery and
dry at first, but as the winter progresses and the snow compacts, the
water becomes concentrated. The rule of thumb is that 30 inches (76
centimeters) of snow in the Sierra Nevada range is equal to roughly 12
inches (30 centimeters) of fresh water once it melts.
As of March 30, the statewide average snow-water equivalent (SWE) was
24.4 inches. There were some regional differences, with 28.1 inches of
SWE (97 percent) in the northern Sierra Nevada; 25.2 inches (88 percent)
in the central region; and 19.3 inches (72 percent) in the southern
region.
NASA Earth Observatory image by Jesse Allen, using Landsat data from the USGS. Caption by Adam Voiland and Michael Carlowicz.
n March 2016, ash poured from a stratovolcano
in the Kuril Islands. After a year of inactivity, Chikurachki erupted
explosively on March 29, 2016, sending ash to heights of about 3 to 4
kilometers (2 miles). Noting that ash explosions up to 10 kilometers
could occur at any time, volcano monitoring agencies posted a code orange aviation alert.
Chikurachki rises 1,816 meters (5,956 feet) above the western Pacific
Ocean on Paramushir Island, just south of the Kamchatka peninsula. It
is made up of alternating layers of hardened lava, ash, and rock, and it
is one of the more restless volcanoes in the tectonically active area.
NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Caption by Kathryn Hansen.
On March 17, 2016, NASA’s Aqua satellite acquired this natural-color image of cloud streets over the Norwegian Sea.
Cloud streets are long, parallel bands of cumulus clouds that form
when cold air blows over warmer waters. On this day, an outbreak of cool
air moved southward across Arctic sea ice toward northern Scandinavia.
The difference in temperature between the sea surface and the air in
this area can be well over 10 degrees Celsius (18 degrees Fahrenheit).
To transport the heat away from the sea surface, columns of heated air called thermals naturally rise through the atmosphere. The air masses rise until they hit a warmer air layer (temperature inversion), which acts like a lid. The rising thermals then roll over and loop back on themselves, creating parallel cylinders of rotating air. On the upper edge of these cylinders of rising air, clouds form. Along the downward side (descending air), skies are clear.
“The cloud streets are just the manifestation of nature trying to get rid of energy imbalances,” said Erik Kolstad,
a weather and climate scientist at Uni Research and the Bjerknes Center
for Climate Research in Bergen, Norway. “This is also what happens in
tropical cyclones, which suck up heat from the warm ocean surface and
transport it far away.”
The cold air outbreak in mid-March spurred the formation of more than
just cloud streets; it also led to vortices southeast of Svalbard, over
the Barents Sea. Kolstad notes that these “comma clouds” occur when
warm, humid air starts to wrap counterclockwise around the cold air.
When these air masses are lifted, clouds are formed. Comma clouds are
the first sign that a small-scale low-pressure system (polar low)
is forming. Given the right conditions—cool air aloft and the absence
of a lid-like inversion—polar lows can grow into very fierce (though
small-scale) cyclones.
“Cloud streets and polar lows are very common over the Norwegian Sea
from October to April,“ Kolstad said. “March seems to be a month with a
high frequency of this phenomenon.”
That corresponds to the time of year when there is ample Arctic sea
ice to cool the air. The edge the sea ice pack in the Arctic Ocean is
visible near the top of this image. Sea ice grows each year
throughout the fall and winter and reaches its maximum extent sometime
between February and April. On March 24, 2016, a week after this image
was acquired, Arctic sea ice peaked at 14.52 million square kilometers
(5.607 million square miles).
Overall, the 2015-2016 winter saw unusually few polar lows, and sea
ice might have played a role. While there was more ice in March 2016
compared to other seasons throughout the year, the maximum extent was a
record-low since the start of the satellite record in 1979.
“When there is little sea ice, there will be fewer cold air
outbreaks,“ Kolstad said. “But this works both ways. Cold air outbreaks
(northerly winds) are instrumental in transporting sea ice southwards,
so a lack of cold air outbreaks also contributes to a lesser sea ice
extent.”
