Sunday, October 18, 2009

High Knob Massif Dazzles In First Wintry Blast


Elevation 4223 feet
High Knob Peak In Dazzling White - October 18, 2009
Photograph by Roddy Addington - © All Rights Reserved.

The High Knob Landform

The first snow & rime event of the 2009-10 winter season coated the High Knob Massif in a dazzling array of whiteness during the weekend of October 17-18.

A little light snow and rime coated the highcountry into early on October 17 as temps at the highest elevations fell into the 20s, with wind chill factors in bitter feeling 10s!

That mini-prelude mostly melted away during the daylight hours of Saturday, amid low clouds and fog, with the main event taking shape into the early hours of October 18.

While snowfall totals were generally 1" or less during the episode, riming was significant and absolutely gorgeous as captured beautifully by talented photographer Roddy Addington.

[ New reports into October 19 indicated that local snow depths reached 2" or more along some windward facing slopes, but otherwise were 0.5" to 1" or less within the area.  Some intervals of large snowflakes were reported down into the Wise Plateau, with no accumulation.  A little mixed sleet and flakes also fell with light rain and drizzle down to around the elevation of Clintwood ].

October 18, 2009
RIME Coated Northern Slope of High Knob Massif
Photograph by Roddy Addington - © All Rights Reserved. 

RIME makes the sprawling highcountry expanse of High Knob a water capturing wonder during the cold season, as moist, bitter winds are lifted and forced to rise, cool, and condense out their loads of moisture across its many lofty ridges & basins.

Although I have observed and studied RIME for many years, it NEVER fails to STUN and simply AMAZE me in the forms it can take as desposition occurs on trees and vegetation across the great expanse of the High Knob Massif.

This is why TREES are so important to the numerous lakes and wetlands amid this remnant massif of highcountry.  Along with fog drip during much of the year, trees generate and enhance secondary moisture sources which simply would not exist without them.  This makes the sprawling High Knob Massif a true water capturing wonder!

The above processes being vital to ALL LIFE within and downstream of the High Knob Massif ( including YOU )
in the Upper Tennessee River Basin.

Exotic Northern Red Oak RIME ( Quercus rubra var. borealis )
Photograph by Roddy Addington -© All Rights Reserved.

Is that a WOW photograph by Roddy, or what?

Simply wondrous are the ways of often moody Mother Nature when sub-freezing air, moisture, and high mountains get all tangled up. 

AMAZING!

Golden Rod ( Solidago spp. ) Coated With RIME on High Knob
Photograph by Roddy Addington - © All Rights Reserved. 

Mere written words, as I write this now, can not even begin to truly describe how magnificent this aspect is to the High Knob Landform.

Remember...
The High Knob Landform ( HKL ) is:

A great continuous mountain landform consisting of

1 ). a remnant massif of highcountry
( the High Knob Massif ) 

2 ). a northwestern mountain flank
( Little Stone-Stone-Cumberland mountains ) 

3 ). a southeastern mountain flank
( Powell Mountain-Newman Ridge ) 

4 ). an eroded calcareous core that separates these mountain flanks and narrows by headward erosion, to the northeast, into the inverted V-shaped Powell Valley ( adjacent to High Knob peak ).

October 18, 2009
Delicate Rimed Umbel on High Knob Massif
Photograph by Roddy Addington - © All Rights Reserved. 

The main rime zone within the remnant massif of High Knob extends from Cliff Mountain and Bowling Knob, the highest peak in Lee County, northeast along the Powell Mountain block to Thunderstruck Knob and Little Mountain ( i.e., along either side of the rugged Wise-Scott border ).

It then extends across lofty Big Cherry Basin & the High-Eagle Crest Zone ( High Knob & Eagle Knob peaks, highest points in Wise County ) to Camp Rock Knob ( highest peak in Scott County ) and the lovely Bowman Mountain ( within upper Clear Creek Basin of Wise County ). 

RIME can occasionally form much lower in elevation and nearly reach the valley floors, along northern & eastern slopes of the sprawling massif, during ideal situations with abundant moisture and very cold air enhanced by orographics.

Southwest of the remnant highcountry of the High Knob Massif the main rime zone caps the rugged northwestern flank of it's great High Knob Landform ( HKL ) to emerge with vigor once more across the lofty backbone of Cumberland-Brush mountains in majestic Cumberland Gap National Historical Park. 

Perhaps, that is one way famous 
"White Rocks" got their name?  

Northwestern Flank of The High Knob Landform
White Rocks of Cumberland Gap National Historical Park
Photograph by Harold Jerrell - © All Rights Reserved. 

The above described rime zones form during more typical NW-N air flow events, such as that which is currently being documented here for you to see with your eyes ( i.e., from October 17-18, 2009 ).

Reference the following section for more stunning examples


The High Knob Landform is, however, anything but typical, as orographically forced upslope flow on moist, southwesterly winds, or south to southeasterly winds, can bring the rime formation zone down into the windward facing slopes of these prevailing winds.

I explained the nature of rime
in a former newspaper article:

"On dark, cold winter days when cloud bases hang low across the great High Knob mass there is magic in the air.

Literally!

For when the clouds part, and sunshine returns, it is as if the Lord himself had taken a great brush and spread a blazing white blanket of sparkling crystals across the highcountry.

Visitors are simply amazed.

The substance which paints these gorgeous scenes is called rime, and while it may take different forms it is essentially frozen clouds of water!

While rime may cap any of the taller mountains of the southern Appalachians, it is special on High Knob.  For you see, High Knob is no ordinary mountain!

Unlike most southern Appalachian mountains which rise to a peak, then drop off the other side, the crest of High Knob spreads outward for mile, after mile, after mile.

Residents of Wise, Scott, and Lee counties have looked upwards all their lives at the beautiful white trees which stand like polished jewels against the dark blue of a winter sky."

For a perfect visual example of this please reference:


High Knob Massif - October 18, 2009
Trees Bow On Highcountry Route 619
Photograph by Roddy Addington - © All Rights Reserved.

One aspect that made this event extra special was some lingering leaves on the trees.

Although most leaves had fallen across the highest elevations ( thankfully, to reduce damage ), enough remained to create many glorious scenes!

October 18, 2009
High Knob Massif
Sugar Maple ( Acer saccharum var. saccharum )
 Photograph by Roddy Addington - © All Rights Reserved.

One of many incredible things about rime is that it GROWS INTO the moisture bearing winds.

In other words, RIME forms toward the north, headward, into a north to south blowing wind such as that which occurred into the morning hours of October 18 ( in 2009 ).

High Knob Massif
RIME on WINDWARD side of Branches
 Photograph by Roddy Addington - © All Rights Reserved.

This is beautifully illustrated by Roddy's photograph above, as ALL the rime has formed on the windward side of the tree limbs.  Essentially no rime has formed on the lee side, or downwind side, of the branches.

Is that not just the most AMAZING thing!

Even more impressive is that rime growth actually accelerates, or increases, as the wind speed increases.

Jefferson National Forest
Wind Swept High Knob Meadow - 4223 Feet
Photograph by Roddy Addington - © All Rights Reserved.

Strong winds can sweep the ground clean of snow, but rime deposition and growth can actually continue and increase with ROARING winds 
( as noted above ).

That is the single aspect, if nothing else, which clearly separates RIME from SNOW on trees, as a good wind gust will typically ( and often easily ) blow snow OFF tree limbs.

Exotic RIME Figure on High Knob - October 18, 2009
Photograph by Roddy Addington - © All Rights Reserved.

Let's look at that figurine a little closer!

Exotic Figurine Formed In Rime
Photograph by Roddy Addington - © All Rights Reserved.

You can find the most incredible, often unbelievable, features during rime events.  This is an AWESOME part of our mountain landscape, as exemplified by Roddy's next photograph.

WOW!

Stunning Northern Red Oak ( Quercus rubra var. borealis )
Photograph by Roddy Addington - © All Rights Reserved.

What excites me perhaps most of all about RIME is the amount of water it can add to the budget of an already wet location like that of the sprawling High Knob Massif.

RIME is a MAJOR secondary moisture addition, along with FOG drip in non-freezing air, to the annual water budget of the High Knob Landform.

However, it ONLY captures this moisture, and extracts it from the AIR, on upright objects such as TREES and vegetation.

[ In areas devoid of trees much of the cloud vapor will blow across and never be extracted from the air. If trees did not cap the High Knob Massif a great amount of moisture would pass leeward of this highcountry and simply evaporate away with subsidence, or sinking, of the air flow and never be captured.  Incredible! ].

Trees make the High Knob Massif
a WATER CAPTURING WONDER!!!
( the above derserving to be stressed once more ). 

In this light, trees are vital to our water supplies, with BIG, mature trees ( due to their much larger surface area ) being amazing scavengers of moisture via rime deposition upon them during sub-freezing conditions and fog drip from them during above freezing weather.

[ The above statement having NO "environmental" agenda toward loggers or non-loggers, but simply being based upon the absolute and true scientific facts and reality of what is, as can be proven by ANYONE willing to test it as I will explain below ].

Rime deposition on trees adds to the annual water budget upon it's melting, of course, but more often than not the process is a bit more complicated than just melting.

The following photograph by Roddy illustrates the true and ultimate importance of RIME.

RIME on ROAD - October 18, 2009
Photograph by Roddy Addington - © All Rights Reserved.

No, the importance is not that RIME can cover up a road.

The importance is that it can cover up a ROAD that has NO TREES directly above it, to illustrate how MUCH MORE it can cover the ground within woodlands BENEATH dense trees and vegetation!

Typically, on High Knob, rime falls off onto a snowpack.

Over time, and often with many multiple rime events, this ADDS a great amount of moisture to the snowpack, which then eventually melts to add water to our below ground water table, creeks, and water supply lakes.

A most amazing and little understood process by those not involved in it's study.

[ Although rime is more dense than hoar frost, and lighter than a glaze from freezing rain, it can accumulate enough at times to cause damage on High Knob.  INCHES of rime can sometimes build up during major or prolonged events, and even develop into long projections.

Long spears of rime have formed before on chain-link fences surrounding Tower sites in the Eagle Knob Communications Area on High Knob.  The most destructive situations develop when an ice storm, with freezing rain, is followed by riming which coats the ice to add additional weight ].

As I have written before,
ANYONE can prove to themselves the importance of RIME.

Get a 4" diameter National Weather Service rain gage, with inner measuring tube, and find a small bush to make it easier to manage.

SCRAP off ALL the rime on that bush into the rain gage.  Melt it down.  It will take very little math to realize how SIGNIFICANT this rime process is, given bushes collect only a tiny fraction of the rime of large trees.

For example, if the bush is 5 feet tall you will have to multiply your rain gage melted amount by a factor of 15 to represent a 75 foot tall tree and by a factor of 20 to represent a 100 foot tall tree ( but note, since bushes are so thin and low to the ground they typically will not collect as much rime as big trees which stand tall in the swirling air.  Your estimate will be low, perhaps, MUCH too low! ).

After you do that, simply ( dare I say ) multiply the AMOUNT obtained by ALL trees, shrubs, and even tall weed stems within the RIME formation zone!!!

Needless to say, the only conclusion is that this process of RIME formation is of VAST importance to the great High Knob Massif, and to all mountains tall enough to stand amid the rime formation zone ( i.e., amid the clouds in sub-freezing air for extended periods of time ). 

However, due to the unique base-to-base WIDTH of the High Knob Massif, it is especially important to the High Knob Landform!

Finally, I want to leave you with an original masterpiece by Mother Nature and my friend Roddy Addington. 

In this photograph it is actually possible to see where the colorful pigments of the Northern Red Oak have leached
into the RIME itself.  Absolutely stunning, and incredible!

High Knob Massif - October 18, 2009
Rime Swirled Northern Red Oak ( Quercus rubra var. borealis )
Photograph by Roddy Addington - © All Rights Reserved.

Need anyone say more!

Well, maybe just a few more words....
This is for those interested in how the above formed.
Air literally swirled around the Oak leaf seen in the foreground, as indicated by the SWIRL in the rime pattern.  This was caused by a micro boundary layer effect, much like occurs on a larger-scale within the friction layer of earth ( the famous Ekman Spiral for those familiar with mathematics and terrestrial-oceanic boundary layers
of planet Earth ).

The slightly concave nature of the leaf surface likely caused this to develop, with air swirling downward toward it's lower central section.

In this case, the trace of the air flow left an amazing swirl of frozen cloud vapor called RIME.

No comments:

Post a Comment