Peak leaf-peeping weeks

-Foliage in Yosemite Valley is at its peak color now. While weekdays are very quiet, recent weekends have brought in lots of leaf-peeping visitors. Black oaks, big-leaf maples, and black cottonwoods are all shining in their various yellows. Dogwoods own the red/pink. The sugar maple is bare.
-Michael Frye reported seeing azaleas blooming in El Capitan Meadow, and sure enough, I found them yesterday. On many of these yellowed shrubs are fresh, bright white flowers. The fragrance isn't strong, but a sniff puts one right into the warm days of June.

-In the canyon below Yosemite Valley, there are miles of grapevine - invisible all summer - now declaring its presence with yellow leaves. It's truly remarkable how abundant wild grape is, now that it's highlighted.

-The Merced River is still running quite low, at about 60% of average volume. The storm that's arrived today is not expected to add much precipitation, though we should see a bit of snow at low elevations. We'll probably lose some of our colorful leaves, but that just makes walking through the fallen foliage more fun.
-Our final field seminar of the year is on December 1: "The Day of the Woodpecker." You'd be astounded what there is to know about Yosemite's diverse group of woodpeckers.
-We start 2013 programs with snowshoe treks, and two special photography courses. All leaves remaining through the winter will be green; come see.

Click or Treat

It's a great time for photography in Yosemite. Though the sugar maple has gone bare, the big-leaf maples, dogwood and dogbane are really bright now, if you're in the right places. Oaks and cottonwoods are waiting their turn in the Valley. The Crane Flat and Hetch Hetchy areas are really colorful now.
-Photographers Keith Walklet and Mike Osborne still have a few spaces in their November 1-4 field program with Yosemite Conservancy. They are a remarkable team with a lot of Yosemite accomplishments to their credit.

-Two dark bears were seen for several days eating acorns high in a valley oak by the railroad engine in El Portal. In Yosemite Valley, they've also been harvesting directly from the canopy. With bathing suit season over, the bears are trying to take in 20-30,000 calories/day so they'll have a comfortable winter's sleep.
-Winter birds have arrived: juncoes, white-crowned and golden-crowned sparrows have descended to find seeds in snow-free El Portal for the winter. Varied thrushes have been seen in the Valley and near Merced Grove already. Naturalist Dan W. reports a meadowlark in Ahwahnee Meadow from earlier this week, when he was leading a "Yosemite Insider Experience" group for the Conservancy.
-We had another mild storm come through Monday, closing Glacier Point and Tioga Road with a few inches of snow. They're both likely to re-open shortly. The precipitation finally initiated the river's seasonal rise, from the year's low of 18 up to 26 cfs. Normal would be in the low 30's.
-I had a chance to examine one of the hand-hewn wooden stakes that John Muir used 1872 for the first quantitative glacier study in the U.S. It was found by NPS personnel on the 1936 glacier survey and brought to the park's museum archive. It was pretty interesting to handle something that Muir himself made when he was up at our glaciers with Galen Clark and Joseph LeConte. Regretably, Muir didn't bring his digital camera on those two trips...

Insatiable albedo

It's autumn and in Yosemite Valley:
-days are shorter
-the cliffs and trees cast longer shadows
-the sun is at a lower angle so it lights less ground
But we also find that:
-the lower sun lights the north wall more directly
-the pale, dry grass gives off a brightness not seen in summer's dark green
-the yellow of maples, milkweed, dogbane, raspberry and some oaks and cottonwoods add increased reflectivity to the substrate, from leaves both on plants and that have fallen on the dark ground.

This 'yellow day of October' bears out Muir's notion that the Sierra may actually be composed of light. It's nice to contemplate the conflation of matter and the electromagnetic spectrum while beholding the reflected glow with your own eyes here in Yosemite.

-In the Valley last week Conservancy naturalist MRoss observed both a gray catbird and the Asiatic form of an American Pipit.
-The one sugar maple in Old Yosemite Village is bright red-orange now.
-We are getting our first dusting of snow in the high country, with Tioga Pass being closed briefly.
-The Merced River flow at Pohono Bridge has flatlined at a thin 19 cfs. The historical average river volume for today is 30 cfs and rising.
-Geologist GStock's latest glacier observations indicate a rate of motion for the Maclure Glacier that is identical to what Muir measured 140 years ago. Sadly, though it's bigger than the Maclure, the Lyell Glacier appears to be in a terminal phase.
-That's Venus you see, really bright in the eastern sky in the morning. The nearby star is Regulus, the brightest star of Leo. What can we interpret from the apparent proximity of the goddess of love and the king of the beasts? Only our own spatial provincialism; Regulus is not close but is 77 light-years away from Venus. Regardless, the light of both bodies adds to the shine of not just Yosemite, but our whole bright world.

Equinox Arrives

Yosemite's weather is still quite warm, but is hinting at autumn. Though mild this week, there has been more frost in high elevation meadows and the bilberry is reddening.
-At the foothill edge of the park, redbud leaves are yellowing and poison oak is going bare. Higher up, dogbane and the green Ceanothus are both going yellow. No color yet in maples, cottonwoods or oaks in Yosemite Valley.
-An osprey has been seen regularly in the El Portal stretch of the Merced for about the past month. The river is running only 23 CFS at Pohono Bridge meaning fish have fewer places to hide. Naturalist Michael R. saw pintails in Tuolumne Meadows last week.

-We've all learned a lot about the epidemiology of the Sin Nombre Virus (Hanta) and about the reactions of people to unfamiliar threats in the past few weeks. It's a most regretable situation.
-The park geologist has measured surface velocities in the Maclure Glacier and the West Lobe of the Lyell Glacier. Though shrinking quickly, both are still living glaciers. The Lyell is moving so slowly that it may grind to a halt in just the next few years; while the surface is still sliding downslope it's possible that the base is already static on the bedrock.
-Though we had such a dry winter, we've only had one real fire this summer: the Cascade Fire, started by lightning in mid-June, just south of Tioga Road between Crane Flat and White Wolf. In 3 months of creeping along the ground it has burned only 1200 acres.
The park's Fire Ecologist Gus Smith will be leading an exploration of the Mariposa Grove on Friday 28 September. This program is open to the public and is sponsored by Yosemite Conservancy. As with all Yosemite Outdoor Adventures courses there is free park entry and free camping.
-Also burning are the stars of Orion in the east before dawn, creeping their way higher into the approaching night skies of winter.

Heat and monsoon

It's been really hot in Yosemite for the past week, with Yosemite Valley temperatures in the high 90's (but only the high 30's for European visitors...)
While it feels like El Portal could just burst into flame at any moment (it's been up to 110 degrees) the park has been having a surprisingly light fire season to date. The Cascade Fire, east of Crane Flat has been burning quietly for two months now and is still not quite 700 acres. There's a small lightning-caused fire at the top of Vernal Fall and another tiny blaze near Porcupine Flat.
Monsoon moisture that's come in with the heat has made for great cloud shows ("higher Sierras" in Muir's words) recently. You can partake via webcam without threat of hail or lightning. The Merced River has actually doubled in volume in Yosemite, right up to a normal/average flow, because of the upstream rains. A bit of rain fell in Yosemite Valley and west yesterday afternoon - what a pleasant change.
We look forward to the southward migration of birds of prey over the next several weeks. Michael Ross will lead a field seminar on September 8 for those who want to observe this annual phenomenon in the high country.

Raccoon Days

Dry 'raccoon days' of July have baked Yosemite. August's 'Dog Days' were named in ancient times when the Dog Star (Sirius, the brightest star in the constellation Canis Major -the big dog) became visible just before sunup. Though we can't see it yet in our deep canyon, this bright star is already rising earlier and earlier before the sun.
Before Canis Major and Sirius rise, the Little Dog, Canis Minor comes up from the east. The bright star in Canis Minor is called Procyon. This is also the genus name of the raccoon. The German taxonomist who gave our raccoon its Latin name in 1780 assigned this animal a ranking slightly preceeding dogs; Procyon means 'before the dog' and this also works with this star rising before Sirius. Therefore, perhaps we can stretch the astronomical story to say that Raccoon Days come before Dog Days. Learn more about the stars in our 10-11 August Tuolumne astronomy program.
As far as terrestrial wildlife, up until recently bears have been relatively well behaved this season; there have been fewer car break-ins than usual.
The Merced River continues to flow about 20% of normal volume. It could keep dropping for two more months but it's already less than half the flow of last year's lowest volume. The photo shows Bridalveil Fall in a wispy state this week.
We have one very modest fire burning in the park. It's near the headwaters of Cascade Creek, just south of Tioga Road and east of Tamarack Flat. Lightning started it in mid-June and it's grown to less than 150 acres over 7 weeks - seems almost as though fire just fits in here...

Interdependence Day

Sierra summer is at its finest now. Heat and blue skies make up our days, the waterfalls shrink, birds quiet down as they taper off feeding young that are fending for themselves, bears with cubs explore opportunities for their own kinds of Yosemite picnics. A little smoke in the air would complete the feel of the season.

The Merced River flows at just over 100 cfs in the Valley - normal for this date is over 600 cfs; a dry winter makes a dry summer and Yosemite Falls is a dwindling presence.
I was up at Summit Meadow along the Glacier Point Road this morning and had that pretty part of the park to myself for a while. Shooting stars, bistort and Bigelow's sneezeweed (yes, that's a fun name to say) are profuse now. Yellow-rumped warbler, Steller's jay, and a Townsend's solitaire added an aural dimension, but the voice of the hermit thrush coming from the dark fir forest is like nothing else in the Sierra. New fencing between the road and the meadow should help protect this sensitive spot.
From the far side of the world: Yosemite's Chinese sister national park, Juizhaigou, reports finding the first fresh panda scat in the park in over ten years. Giant pandas depend on bamboo which blooms, dies off and becomes unavailable for years at a time on a localized basis. Juizhaigou's bamboo has regrown to make it perfect panda habitat again. Perhaps the Conservancy may be taking another group of Yosemite-philes to hike in our two sister parks in China next fall.
Speaking of excitement, we are delighted that legendary Ranger Dick Ewart is leading two Yosemite Outdoor Adventures for people this summer: a 5-day trek from Tuolumne Meadows for experienced backpackers, and an off-trail dayhike to the top of Tenaya Peak. These are special opportunities to experience some of what makes Yosemite such a great place.