Monday, December 16, 2013

A Winter's Solstice

The extra cold that the West had last week, was surely felt in Yosemite. Snow fell well below the park boundary and still persists in the shady parts of El Portal. The Merced River has frozen over in much of the Valley and the southern cliffs are streaked with frozen waterfalls. We did not get enough snow to open the Badger Pass area to skiing, etc.

The Merced is running at less than 30% of normal volume, and the watershed still has a way to go to recover from two dry winters.

Yesterday's Christmas Bird Count featured a frosty cold morning then comfortable warmth in the afternoon (unless you were in the shadow of the south wall). Compiler Sarah Stock organized quite a large group of birders, and the birds responded. It's a good year for the colorful varied thrushes, a species that migrates here for the winter, though it doesn't come every year. Early efforts turned up quite a few owls, too: pygmy, screech and great-horned.

Solstice happens on Saturday, when the long, cold night dominates the Sierra. Have a closer look at Yosemite's winter on one of our snowshoe outings. Here's hoping for a snowy new year.

Monday, October 21, 2013

Shakin' It

The Clark Range, within the southeast corner of Yosemite National Park, has been seismically active in recent years. Many nearly imperceptible earthquakes occur here each year. There was a series of 4 shakers last night, some of which were noticed on the west side of Yosemite. The park community of El Portal sits astride the boundary of the granitic batholith and the older metamorphic belt. The way ores can concentrate near a contact like this, vibrations may, as well. Deep but slender barium mine excavations at the igneous/metamorphic boundary may serve as sound boxes where the resonances of the earth can surface.

When the Merced River is low, El Portal is a pretty quiet place, especially at night. Some of us heard at least some of the four 1.0-2.2 magnitude temblors as deep roars, lower pitched and shorter in duration than a passing jet. I noted the time of the clearest roar, at 2:54 a.m., and there it was on the USGS website, as a restless moment east of Gray Peak, and 15.9 km deep.

Aspen on the East Side and in small pockets within the park, are past their peak color, but still bright. In the Valley, the sugar maple has gone bare, but there's lots of color remaining.

Dogwoods are red,

The sky is blue.

The oaks are all golden,

And maples are, too.

Friday, September 13, 2013

Autumnal Equinox

We are about a week from when the length of day and night balance out. It's still warm in much of Yosemite, especially in our northwest corner, where smoke and burned ground are the rule. That part of the park will be interesting for many years, while it recovers from the Rim Fire. Egret seen in the Valley. Gaylor basin's pikas weren't shy while gathering winter stores of bilberry, etc. Grindella still adds floral color to the canyon in El Portal, while dogwoods, dogbane and other foliage is turning autumn colors in mid-elevations. The Conservancy's Fall Gathering event is coming up soon, and there's still space in our one-day field seminars with either author Suzanne Swedo or photographer Chris Loberg that first weekend of October.
I've had such a busy season in the office and out on the trail; Yosemite has too much good stuff to get it all in. Now I look foward to Orion overhead, chlorophyll breaking down, the frost line descending, and more square mileage per person in the park.

Friday, June 7, 2013


We've had 4 days in a row of afternoon thunderclouds and rain in the high country.  Locals are reminded of the August monsoons.  We expect Yosemite Valley temperatures in the low 90's, with continued thunderstorm possibilities.
After a second dry winter, the park's watercourses are low.  The Merced River is running about 1/3 of average.  Yosemite Falls looks good now, but it's bound to dry up entirely by late summer.  Buckeyes in the lower canyon are browning already.  Clarkia is mostly gone: farewell to farewell-to-spring. 
A pair of wood ducks has been at Mirror Lake, but not seen nesting.  Mallards have their ducklings now.  Our morning birdwalks are still filled with singing tanagers, orioles and grosbeaks.  Several bears have been hit by cars recently, with at least one killed; those speed limits are there for good reasons. 
The new 'Snowplants' Yosemite Nature Notes video is remarkable; watch this space for the new posting in the next few days.
Geologist Greg Stock is sharing his expertise in a one-day geology course on June 15 in the Valley, and the photography course to Waterwheel Fall also has space available. 

Sunday, May 12, 2013

Signs of Summer

Cool, wet weather a week ago brought the river level down from above average to below average.  Now the unusual heat has brought it back toward a more typical volume again, a bit below 2000 cfs at Pohono Bridge.  I could be wrong, but the peak flow of the Merced and tributaries may have passed already - 3 weeks earlier than average.  We expect a long and active fire season this year.
The Valley has been humid and green lately.  Oaks and maples are all but fully leafed out.  Dogwood blooms light the forest from within. A cloudburst the afternoon of the 9th caused local flooding and felt like an August monsoon storm.
Otherwise the waters are retreating.  Sentinel and Ribbon Falls are noticably smaller than a week or two ago. Staircase, Horsetail and Royal Arch are just dribbles.  Eagle Creek and Horsetail Creek haven't flowed on the surface of the Valley floor at all this year.  Wosky Pond is no more than 15m across at any point. 
Orioles, vireos, warblers, tanagers, grosbeaks, peewees, and robins sing with energy in the mixed oak/conifer canopies throughout the Valley.  White-throated and Vaux's Swifts have been seen and heard on the Monday/Thursday Conservany birdwalks lately.  A rare yellow-headed blackbird has been observed calmly feeding in Yosemite Village for several days recently. 
Tioga Road opened this weekend; snow cover is obviously light in the high country.  There was a fatal accident at Vernal Fall last week.  Weekends in the Valley are busy now, but weekdays will be relatively calm until more schools get out.
Some of the Conservancy's upcoming courses are full, but there's still space in a one-day, mid-June geology adventure with the wonderful Greg Stock, our Park Geologist.  Some of our Half Dome trips still have space available this summer, too.  Summer seems to be upon us now.

Friday, April 19, 2013

It's not 'frazil ice'

Technically, frazil ice is a slurry of ice particles that forms at the supercooled surface of turbulent liquid water.  Frazil forms in rivers and in wind-blown lakes/reservoirs in cold places.  What we have in Yosemite is a slurry of ice particles that forms as liquid water is aerosolized in a waterfall descending through sub-freezing air.  The end product of each process looks similar, but the way the very different talus and till can look similar or the unrelated heron and a crane look similar, to be proper, frazil and the distinct Yosemite waterfall feature should be distinguished with a different label. 
We might shorthand this frozen waterfall mist as 'wist ice' or a 'wist slurry.'  Because its origin is distinct from true frazil ice, our phenomenon deserves it's own name, though I wouldn't really expect our established common usage of 'frazil' to change.
One line of evidence that tells us that this isn't frazil ice is that when the creek below the waterfall is filling with the slushy mass, there is no ice above the falls.  This photo shows Yosemite Creek just above Upper Yosemite Falls at 7:30a.m. on 16 April, when it was 24 degrees F there.
There are no ice particles above the waterfall, but a dense slurry flow below.  No supercooled liquid is involved.
We've had wist slurries flow in Yosemite Creek and Ribbon Creek the past couple of mornings when temperatures dropped into the 20's.  Near-term forecasts don't look cold enough to produce much wist for the next few days.
Yosemite Conservancy's Monday and Thursday 8 a.m. birdwalks in the Valley have resumed for the next two months.  Orioles and grosbeaks have arrived in Yosemite Valley; we eagerly await our first tanagers.  The first warbling vireo of the year was heard yesterday.
The Hetch Hetchy Road has re-opened after repairs.  Merced River Plan public comments are due April 30.  Tioga Road is melting out faster than usual.  River and stream run-off has been higher than usual for the past two weeks, but it's expected to taper off early.  Seasonal waterfalls should be quite small by mid-summer.
There's still space in Dave Wyman's 'Spring Light Photography' course in mid-May.  Dave is a charismatic teacher with years of experience in Yosemite, and Yosemite always has something to teach us.

Thursday, March 14, 2013


Thaw: It's really warm in the park this week.  The Merced River has increased its flow to well above average, but our runoff won't last very long this year.  The latest snowpack surveys indicate 68% of average water content for the Merced watershed.
Freeze: Despite the clear signs of spring, we are not beyond snow season yet. Vernal equinox is next Wednesday, but we still have two months of snowfall potential.   Frazil ice maximum in Yosemite Valley is still a month away.   Skiers have three more weekends to enjoy skiing at Badger Pass.
Thaw: In the lower canyon flowers grace the terrain with orange poppies, white popcorn flower, baby blue-eyes, and even the redbud are emerging in their unique purple.  Kinglets, flickers and Bewick's wrens are singing this morning, and three species of swallows have returned to El Portal.  Buckeyes are greening up.  Armadas of white-throated swifts are already sweeping the skies up to 5000'.
Freeze: Despite the scant snow, Tioga Road won't open any earlier this year.  To cut costs during the current federal cutbacks, NPS will delay the start of plowing.  XC skiers are still gliding at Crane Flat.

Lyell West Lobe
Thaw: I hope by now most of you have heard the news that higher up in the park our measurements of the Lyell Glacier indicate that it has stopped moving.  Technically speaking, a glacier is ice that moves.  Lyell had been the largest glacier on the west slope of the Sierra, but now that distinction falls to the adjacent Maclure Glacier.  The former Lyell Glacier might be properly called a glacieret or a glacial vestige.
Thaw/freeze: Comet Pan-STARRS is visible very low in the west after sunset.  It's not easy to get a low enough horizon in Yosemite to see this comet in the twilight.  Binoculars are key to spotting this comet, which will fade over the next couple of weeks. 
I'm excited about a special program on April 13 that brings together Muir's great-great-grandson and a Muir actor for a day of roaming John Muir's haunts in Yosemite Valley.  This will be a fun way to experience history in person.

Friday, January 25, 2013

Best Little Hoarfrost

The recent weeks of steady cold allowed the growth of terrific hoarfrost formations in Yosemite Valley. Spikes and florets and feathers of ice condensed out of the atmosphere onto the ground, river ice, and tree branches wherever moisture and cold combined. A bit of this happens every winter, but this season's displays are exceptional.
Late this week, conditions have thawed. The first Amsinckia (fiddleneck) of the season has bloomed outside the Conservancy office in El Portal. There's a sunny bank where they often show early, and here's our first contestant in this year's mating game. Wilhelm Amsinck never came to California, but was a patron of the Hamburg Botanical Garden and his philanthropy is still rewarded today with us exclaiming his name each spring. (The picture shows fiddlenecks last spring.)

In shady spots further down canyon, Kumlienia (waterfall buttercup) is blooming profusely now. Thure Kumlien was a Swedish naturalist who relocated to Wisconsin a few years before the Muir family arrived there. As John Muir did, he spent as much time in the woods as he could and later taught school for a time. Now his legacy lives on in this genus, the first flower we find each season.

The road into Hetch Hetchy has been closed until an eroding section can be safely stablized.
Steve B. has crafted his best video yet, "One Day in Yosemite." After you watch it, plan yourself several days in Yosemite.
The Conservancy's 'Yosemite Outdoor Adventures' are all on line for the whole year now. Don't miss out on a chance to get out on the trail with us and learn from the best in the field.

Tuesday, January 8, 2013

No Ahwahneechee Apocalypse

For what we call 2013 the world continues on its way, no matter our contrivances. The Ahwahneechee did not predict a global apocalypse for this recent solstice, and they were right! Our physical cliffs endure and are not something that needs to be averted. In Yosemite, neither Half Dome nor Yosemite Falls noticed when we replaced old calendars with new ones. The one real change that occurred during our holiday scurryings was that the sun is starting to inch northward in where it rises and sets, and that each new day is a litle bit longer. To be more accurate, the sun isn't doing anything; it's our spot on the world that faces toward and away from the sun at a slightly different angle each day. Solstice is real to Yosemite, our calendars perhaps less so.
It's been quite cold in the park for a few weeks; there's snow and lots of ice in the Valley. Frozen waterfalls like Widow's Tears and Silver Strand (on the south wall, between Bridalveil and Tunnel View)are extra prominent and solid now. If you're thinking about a closer look, KC and JT tell me that Widow's Tears is the longest ice climb in the US.
Feathery worlds of surface hoar can be found in shady meadows early in the day. Small amounts of frazil ice have formed on some creeks. The snow cone at Upper Yosemite Falls is building steadily.
Badger Pass and Crane Flat both have healthy snowpacks for snowshoers and XC skiers. No one is ice skating on Tenaya Lake this winter.
Some of the Summer Triangle asterism is visible over eastern Valley walls before sunup. As Muir wrote it: 'each in its turn as the round earth rolls.'