Newsgroups: lter.ced Path: LTERnet!news From: bph@virginia.edu Subject: CED 3.1 Message-ID: <1994Jan3.135211.11917@lternet.washington.edu> Sender: news@lternet.washington.edu Organization: Long Term Ecological Research Date: Mon, 3 Jan 1994 13:15:51 GMT ***************************************************************** ***************************************************************** *** *** *** *********** *********** ********** *** *** * * * * *** *** * * * * *** *** * * * * *** *** * ********* * * *** *** * * * * *** *** * * * * *** *** * * * * *** *** * * * * *** *** *********** *********** ********** *** *** *** ***************************************************************** ***************************************************************** Vol.3 No.1 :::::: file name:CED 3.1 :::::: January 1, 1993 ***************************************************************** ***************************************************************** CED METADATA ---- CED is the Climate/Ecosystem Dynamics bulletin board ofthe LTER network. In CED, you will find exchanges of ideas, information, data, bibliographies, literature discussions, and a place to find experts withinthe LTER community. We are interested in both climate controls on ecosystems and ecosystem controls on climate. As this is an inter-disciplinaryactivity, we hope to provide things that you might not come across in your work atyour LTER site. CED is a product of the LTER climate committee and contributions to CED for general e-mail release may be sent to either David Greenland of Andrews LTER [Greenlan@oregon.uoregon.edu] or to Bruce Hayden of the Virginia Coast Reserve LTER [bph@envsci.evsc.virginia.edu]. We expect that the scope of CED will evolve and reflect the interests of the contributors and users of this service. CED will be issued as the preparation work gets done (usually monthly). Back-issus of CED may be requested from Daniel Pommert [daniel@lternet.washington.edu] by the file name given in the masthead. Daniel can also add people to the CED mailing list. Feedback on CED from LTER scientists is welcome (non-$$$$ contributions also welcome.) For example, please forward citations of climate & ecosystem publications on your site. We are keeping a LTER wide bibliography on Climate/Ecosystem Dynamics that we pass on via E-mail. ***************************************************************** ***************************************************************** *** *** *** *** *** CED TURNS THREE *** *** *** *** *** ***************************************************************** ***************************************************************** CED has earned its volume 3 credentials which I think only proves that the Frist Law of Demographics applies: everything gets one year older each year. It will probably remain a child-like three until we find a new crafter and editor. Things are busy around the VCR these days. Our LTER renewal proposal is due February 3rd! It is my good fortune now that way back in October I gathered an excess of CED material. I tucked away all this rough stuff for my January issue. So CED 3.1 is old, unseen stuff stuffed away for these stuffed-full proposal days. ***************************************************************** ***************************************************************** *** *** *** *** *** ICE FLOWERS *** *** *** *** *** ***************************************************************** ***************************************************************** Jeff Kennedy, regular CED reader, sent me a bunch of stuff on ice flowers that he pulled from a discussion on the ecology "electronic super-highway." Ice flowers look more like an inflorescence of flowers rather than a single blossom. I found that out when I went to my book shelf. Ice flowers were new to me. If you want to have a look-see, get the book Snow Crystals by W. A. Bentley and W. J. Humphreys (1931) now reprinted by Dover (1962) 0-496-20287-9. Bentley spent a lot of his life photographing ice and really got off on snowflakes. He includes a few pictures of wonderful ice flowers. You will marvel at the detail and inside you, near the place where cold shivers begin, a how-could-that happen sigh of marveling will well-up within you. Humphreys wrote the everyone-should-have-a-copy Physics of the Air (1920) Dover (1964). If you don't buy Dover reprinted books you should. I would hate to see Dover go out of business. So, here is what they look like. They have stems, often branched, with six sided, pancake shaped ice flowers on their ends. There needs to be two kinds of growth to form ice flowers: stem growth (crystal elongation) and flower growth (disk formation). ***************************************************************** ***************************************************************** *** *** *** *** *** ICE NEEDLES *** *** *** *** *** ***************************************************************** ***************************************************************** Ice needles? AKA stalk-ice, hair-frost, ice fibers, mush frost and in Sweden pipkrake! When the October-November leaf fall is complete in our Virginia deciduous forests, the season for ice needle hunting begins. With our warm summers and high decomposition rates our mineral soils are close to the surface. Fine red and yellow clays outcrop on our the forest floors. These clays can be high in water content -- good water for ice needle formation. When the leaves are gone, this surface is subject to a new seasonal regime of radiative heat loss. Without the protective umbrella of leaves, the radiation from the soil can pass easily to the sky and to space. If you know where there are nice patches of soldier lichen and button mosses -- a place where the winds tend to blow off the new litter -- it is a good place to look for needle ice. On mornings following nights of strong radiative cooling, go ice needle hunting before the day's sun ruins the night's work. Ice crystals grow upward out of the soil by harvesting non-frozen soil (clay) water. Four to six inch lances of ice are not unusual here in Charlottesville. The ice forms at the base of the crystal. The expansion upon freezing forces the crystal upward. Often there are large mats of these ice needles. Now consider a stump of plant long since killed by a frost. The old xylem elements are a conduit between the location for an individual ice needle and the soil supply of water to make the ice. It is a way to get a stem for a bunch of ice flowers. Temperatures for ice needle formation fall within the range - 5 C to - 8 C. Biological materials subjected to decomposition produces ice nuclei that cause freezing at these temperatures (see earlier CEDs). At colder temperatures (- 15 C to - 20 C), hexagonal columns will sometimes grow from a surface but do so by sublimation (vapor to ice without passing thkrough the liquid phase]. ***************************************************************** ***************************************************************** *** *** *** *** *** ICE FLOWERS AND THE VEGETABLE GARDEN *** *** *** *** *** ***************************************************************** ***************************************************************** One of the best places to hunt ice flowers is the vegetable garden. If you don't plow everything under in the Fall, if you don't roto-till it into a structure free morass, and if you just hack off the last of the crop and let it stand for the winter nights to come, you may find some nice ice sculpture. On the morning after a fine, clear, very cold night, trot out to your garden and look for the row that contains the decapitated cabbage plants. The stems may have some ice sculpture growing out of them. If it was very cold early in the night and then had some warmer, moister but still cold air move in, you might just get some ice flowers. Vegetative matter is often an epicenter for ice nucleation. Decomposed organic matter often has a quasi-crystaline structure that can serve as a ice nucleation point. Once ice begins to form, it is a contest between the ice growth from the substrate and the vapor accumulates in the air. Ice flowers, I think, get their water from two places from the cabbage, its roots in the non-frozen soil, and from the water in the air. The stems come from growth of ice needles built from soil water while the flowers are built from air water vapor. So, ice flowers can grow where there is no vegetable matter at all. ***************************************************************** ***************************************************************** *** *** *** *** *** ICE CAVE ICE FLOWERS *** *** *** *** *** ***************************************************************** ***************************************************************** Rustling through my sources, I came across an ice flower photograph taken in an ice tunnel in a glacier. Someone had put a wooden stake into the wall of the ice tunnel and on it was a small inflorescence of ice flowers. Ice flowers have 6 petals and so one might think of monocots. If you didn't count the petals and just admired the flowers themselves, they would suggest dicots, perhaps dianthus or flattened buttercups. Ice flowers are flat like snowflakes. They build on a single disk like plane. The reason why the stems form and then the flowers form on the stems is a bit strange. This will be come clear in the next item. ***************************************************************** ***************************************************************** *** *** *** *** *** HOW DOES YOUR ICE FLOWER GARDEN GROW *** *** *** *** *** ***************************************************************** ***************************************************************** Ice flowers and winter ET. If we forget for a moment the stomate end of the ET process and define it as the removal of soil water through xylem elements to the air, you cut the leaf off and ET still happens. Not very fast but it still happens. The cases of it happening fast in the winter is very real if the temperatures are low enough. Ice flowers may arise from such a mechanism. In ET there is a phase chane (liquid to gas). When it is very cold, the phase change is liquid to solid -- still it is an extraction of liquid water from the vascular tissue driven by a phase change. Now a bit on frost. Frost is the harvest of vapor from the air directly to the solid state -- the opposite of sublimation. I you have a liquid dew drop and a frost crystal side by side at the same temperature in an atmosphere with some moisture, the ice crystal will harvest water vapor molecules more rapidly than the dew drop. The reason for this is that the vapor pressure difference over ice is greater than over liquid water. Take supercooled dew at -10 C. It would be in equilibrium with air holding water that had a partial pressure of 2.86 mb. If the air had 2.86 mb worth of water in it just as many molecules of water vapor would evaporate to the air as would condense on the dew drop. That is what equilibrium means. Now the equilibrium vapor pressure over ice at -10 C is 2.60 mb. The 2.86 mb air is supersaturated with respect to the ice and many more water vapor molecules condense on the ice crystal than are evaporated form the ice crystal. The ice crystal grows like mad while the dew drop sits there and stays the same size unless its temperature falls and a slight degree of supersaturation occurs. Temperatures fall at night and so dew drops grow as the cooling continues. An ice crystal in the same conditions is not so restricted. So ice can grow rapidly by harvesting water vapor from the air. What if the ice you were building had a more concentrated source of water (liquid water from the soil!)? Then you could do wonderful things, ice sculpture-wise. Next, take a xylem element in an old herbaceous plant nipped-off above ground level by a murderous Jack Frost. The tissues below ground could have been spared the intercellular freezing that Jack brings on above ground, tender leaves and stems. Anyway, the vapor pressure deficit at the ends of these xylem elements tipped by a ice crystal would rival the vapor pressure deficit that drives evapotranspiration on a summer afternoon. The crystal has private supply of concentrated water. The crystal can grow from the bottom producing wonderful forms. It is columnar when deposited rapidly at temperatures not far below the freezing point and tabular when deposited very slowly in very low temperatures. These can look like of inflorescence of dianthus like flowers. Spectacular is the word for it. Winter is coming, watch for those heavy frost days and walk the woods, meadows and stream-sides before the sun has a chance to blunt Jack's work. If there are any photographers in the CED crowd -- have a go at it. ***************************************************************** ***************************************************************** *** *** *** *** *** THE GROWTH OF ICE IN THE OPEN AIR *** *** *** *** *** ***************************************************************** ***************************************************************** Back to the capture of water from the air by ice. -- When ice is actively forming by snatching water vapor from the air, the air over the ice usually has a relative humidity of 100%. That is a bit mis-leading. It is 100% relative to liquid water. That is the rate of molecules leaving liquid water to the air equals the rate of molecules condensing from the vapor of the air to the liquid. When you are water vapor over ice, the air becomes supersaturated relative to ice. So while the relative humidity might calculate out to be 100%, if the ice is growing then the relative humidity is probably 110% or so. It does not sound like much but it means that there is a vapor pressure difference and the net direction of vapor is from the atmosphere to the ice. The calculation is pretty easy. Say the air temperature is -10 C. The air would be saturated with water vapor relative (100%) to a liquid water evaporator and would hold 2.358 g of water vapor per cubic meter of air. However, if you do your calculation based on ice as the evaporator (sublimation) then the air would be in equilibrium at 2.139 g of water vapor per cubic meter of air. So if the air actually had 2.358 g/m^3, the relative humidity relative to the ice would be 110.23%, e.g. (2.358/2.139)*100. Under this condition an unfrozen dewdrop (a distilled water dew drop on a non-nucleating surface) would neither grow nor shrink. The ice crystal will grow like mad! A strong net flux of water vapor drives toward the ice crystal surface. RH relative to liquid RH relative to ice at 0 C 100% 100.00% at -5 C 100% 104.96% at -10 C 100% 110.23% at -15 C 100% 115.72% at -20 C 100% 121.56% at -25 C 100% 127.64% at -30 C 100% 133.94% at -35 C 100% 140.55% at -40 C 100% 147.40% at -45 C 100% 154.33% at -50 C 100% 159.58% Well, how does a cloud drop grow if it is in 100% RH air? Well, as the cloud drops are lifted in the air by upward air currents, the air around the drop gets a bit colder and then the air, relative to the drop, is supersaturated, oh, say 100.3%. It usually doesn't get much more supersaturated than that for cloud drops and so they grow in this slightly supersaturated air. They grow slowly. If you want them to grow fast then freeze them. Then you get big supersaturations! For all you oldsters, remember back to when you had to unplug your refrigerator and defrost (a euphemism for thaw) your freezer. Why did you get all that ice. Well you sucked warm humid kitchen air into the freezer compartment. There it became supersaturated relative to the ice crystals on the freezer walls and the crystals grew faster. Luquillo refrigerators probably had to be defrosted much more often than Toolik lake refrigerators. You had to defrost more often in the summer than in the winter. So how do you get an ice box frost free? It is easy, just have a net flow of dry (unsaturated) air into the box. Stick a dehumidifier (euphemism for air-drier) on you ice box. ***************************************************************** ***************************************************************** *** *** *** *** *** TYNDALL FLOWERS & ICE FEATHERS *** *** *** *** *** ***************************************************************** ***************************************************************** CED readers will recognize the name Tyndall. Tyndall was the natural history physist of the latter half of the last century of biogenic-hydrocarbon, blue-haze fame. Tyndall flowers are found on ice masses upon which light is falling. Tyndall flowers are six-sided crystals that form in small water-filled cavities in ice. They form at a point of effect or an inclusion in the ice lattice. Melting produces a cavity. Re-freezing forms the flower. Ice feathers, like the well-known horse feathers, are a different matter. Ice feathers are also called frost feathers. These single, columnar, ice crystals sometimes grow from other objects. They form on the windward side of terrestrial objects. The also can form on aircraft flying from cold to warmer (more vaporous) air layers. Not good for the flying public. ***************************************************************** ***************************************************************** *** *** *** *** *** FOOLING AROUND *** *** *** *** *** ***************************************************************** ***************************************************************** Window pane ice observers are a common lot. Jack Frost can produces fantastic ice sculptures. We all know that Jack is at his best when it is very cold outside. Close inspection will show that window ice forms first in the tiny scratches on the glass and grow from there. So, you can personalize your windows by getting a diamond pen or a ice cutting tool. (see page 212 of the Bentley and Humphreys book on snow crystals) Scratch you name on your kitchen window and wait for Jack to design a special sculpture just for you. One warning. Check with your spouse or your mother to see if this is OK. Another warning. Be sure to scratch your name, initials or profile on the inside of the window. That is where Jack does his work. On your car jack works on the outside! It is not recommended that you monogram your car! For the serious looker of window pane art, please note that the dominant branching angles are 60 and 90 degrees. For the more serious looker, spirals are common. Free standing spirals -- of the photographs I studied -- are left inward spirals. I don't know why. However, the velocity of ice growth is so slow that the rotation of the earth should be ignored by deep thinkers as the probable cause! Branched window pane plumes that spiral seem to be bilateral with right and left inward spirals on either side of the main axis of the ice form. ***************************************************************** ***************************************************************** *** *** *** *** *** BENTLEY & HUMPHREYS *** *** AT THE FUNNY FARM *** *** *** ***************************************************************** ***************************************************************** On page 18 of their tome (2453 photos of flakes and crystals) Bentley and Humphreys discuss "Picture Crystals." You will quickly get the idea of what a picture crystal is when you learn that it is the equivalent of cloud pictures! Oh my, that one looks like a turtle. Over there, that one looks like Madona on page 33 of her coffee table book! The man on the Moon or the face on Mars are child's visual play compared to the things that Bentley and Humphreys have seen in their ice crystals. From Bentley and Humphreys: "plate 2 page 42, pilot's wheel and army helmets; plate 10, page 38, six hippopotamus heads; plate 8, page 47, birds in flight; 10, page 206, lunch being served, three milk bottles and a bowl apiece; plate 11, page 205, as you like it -- corner turned up, a Janus or two faced ogre, each face with eye, big nose and long beard; corner turned down, a goat, or deer, with ears, eyes and stubby horns, eating from a feed box." Snowflakes not to be out-done, Bentley and Humphreys see some nightmares on window pane ice as well: "on page 226, the beautiful pearls that adorn Arachne's fine spun web; the 'wooly bear' that got so wet; the fly with a bucket of water on his head; and the foolish grasshopper getting rheumatism in his joints!" One wonders if the grasshopper displayed its genitals in ice thereby giving away its gender or if Bentley and Humphreys' 1931 book predates the writing of the Feminine Mystique and formation of NOW and their use of "his" was as the gender-free pronoun of ages past. I got my copy of Bentley and Humphreys at Paul's used book store in Madison, Wisconsin during the ESA meeting. What a find. ***************************************************************** ***************************************************************** *** *** *** *** *** ICE NEEDLES *** *** UP-SIDE-DOWN DOWN-UNDER *** *** *** ***************************************************************** ***************************************************************** New Zealand is a wonderful place for Ice Needles. The sky is often crystal clear and the radiation losses great. Just the right conditions for ice needle formation. LTER's own David Greenland, not a New Zealander to the best of my knowledge, studied New Zeland ice needles and made them in his lab. He assures me that their hypothesis that Southern Hemisphere ice needles grow upside down was rejected both by field observationa and laboratory growth trials. The classy, glassy details are in Soons, J. M. and D. Greenland. 1970. Observations on the Growth of Needle Ice. Water Resources Research 6(2):579-593. ***************************************************************** ***************************************************************** *** *** *** *** *** DUSTY OLD MANUSCRIPTS *** *** *** *** *** ***************************************************************** ***************************************************************** CED readers may find a dusty, old, who-would-want-to-publish-this manuscript in their files and see it in a new light when they read the call for proposals that crossed my desk a while back. For the journal -- CLIMATE RESEARCH. Call for the submission of manuscripts to Climate Research: Interactions of climate with organisms, ecosystems, and human societies -- Climate Research is an international and mutlidisciplinary journal. The journal covers both basic and applied research. It presents critically selected high-quality research articles, reviews, and notes concerned with: 1. Interactions of climate elements with organisms, populations, ecosystems and human societies. 2. Short- and long-term changes in climatic elements: humidity and precipitation, temperature, radiation, carbon dioxide, trace gases, ozone, UV-radiation. 3. Impacts of the scale of analysis on resulting models, etc. 4. Biotic diversity. 5. Historical case studies (paleoecology, paleoclimatology). 6. Analyses of extreme climatic events, their physicochemical properties and their time-space dynamics. 7. Climatic hazards. 8. Land-surface climatology. Readership: Climatologists, meteorologists, atmospheric chemists, hydrologists, oceanographers, limnologists, physical geographers, biogeographers, environmental biologists, landscape ecologists, landscape planners, environmental managers, agronomists, agriculturists, foresters, fisheries biologists, aquaculturists, wildlife specialists, soil scientists, public policymakers. For more information contact Vern Meentemeyer Editor of CLIMATE RESEARCH: Interactions of Climate with Organisms, Ecosystems, and , Human Health. Dept. of Geography, Univ. of Georgia, Athens, GA 30602. [Tel; +1-706-542-4962; Fax; +1-706-542-2388; BITNET: VMEENTE@UGA;Inet: vmeente@uga.cc.uga.edu] ----------------------------------------------------- | Bruce P. Hayden | | VRIGINIA COAST RESERVE LTER | | 101 Clark Hall | | Department of Environmental Sciences | | University of Virginia | | Charlottesville, VA 22903 | | (804) 924-0545 | | bph@viginiia.edu | | bph@lternet.edu | | CED| ------------------------------------------------------ .....................................................