Newsgroups: lter.ced Path: LTERnet!news From: Bruce Hayden Subject: CED 3.9 Sept. 1 1994 Message-ID: <1994Sep1.190609.2887@lternet.washington.edu> Sender: news@lternet.washington.edu Organization: Long Term Ecological Research Date: Thu, 1 Sep 1994 18:12:10 GMT ***************************************************************** ***************************************************************** *** *** *** *********** *********** ********** *** *** * * * * *** *** * * * * *** *** * * * * *** *** * ********* * * *** *** * * * * *** *** * * * * *** *** * * * * *** *** * * * * *** *** *********** *********** ********** *** *** *** ***************************************************************** ***************************************************************** Vol.3 No.9 ::::::: September Issue :::::::: September 1, 1994 ***************************************************************** ***************************************************************** CED METADATA ---- CED is the Climate/Ecosystem Dynamics bulletin board of the LTER network. In CED, you will find exchanges of ideas, information, data, bibliographies, literature discussions, and a place to find experts within the LTER community. We are interested in both climate controls on ecosystems and ecosystem controls on climate. As this is an inter-disciplinary activity, we hope to provide things that you might not come across in your work at your 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@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-issues 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. CED is now a part of the World Wide Web. Web users can link to the following URL: http://atlantic.evsc.virginia.edu/julia/CED.html 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. ***************************************************************** ***************************************************************** *** *** *** *** *** ICE MAKING AT BENARES *** *** *** *** *** ***************************************************************** ***************************************************************** December, January and February is the dry air season at Benares, India. It is the flow out of Asia time of the year. Thus it is the season of minimum greenhouse warming. Well, there is a better way to say that. It is the season of greatest terrestrial radiation loss to space! The Earthly greenhouse in question is not one that results in warming but rather a lessening of cooling. We really don't have any greenhouse warming here on earth but rather greenhouse gases put the breaks on radiation loss to space. It is more akin to insulating your house than stoking the fires in your furnace. Countries dominated by the Asian Monsoon have half a year with ample greenhouse gases, small to modest loss of earth light out to space, and warm nights. The other half of the year has not nearly as much greenhouse gas (H2O) in the air, earth light easily passes out to space, and cool nighttime temperatures are the rule. It is a wet air, dry air thing. Daytime temperatures don't come into this story much. High daytime temperatures are caused by the sun and moderated by evaporation, if water is available. Our story on ice making in Benares is all about the time when the sun is below the horizon: night. My report on Benares is extracted from the Transactions of the Royal Society MDCCXCIII:56-58 and MDCCXCIII: 129-131. by J. LL. Williams. The LL. stood for Lloyd in the late 18th century. The J for John. John was an Esquire at Benares, India. LL.'s paper was read to the Royal Society by William Marsden, Esq. F. R. S. on February 14, 1793 and May 2, 1793 respectively. ***************************************************************** ***************************************************************** *** *** *** *** *** LL. *** *** *** *** *** ***************************************************************** ***************************************************************** LL. notes that even with temperatures that run from 95 to 100 F in the shade the 18th century, locals at Seerore near Benares where LL. lived made lots of ice. Seerorens made their ice on a nearly level plot of some 4 acres. The plot was divided into squares about 5 feet on a side with raised borders. The sunken squares were filled with dry straw or sugar-cane haum. On each bed of hewn and dried standing biomass, broad, shallow pans of unglazed earth were set. The pans, 4 acres of them (~100,000 pans) were then filled with water. This was all hand work as pumps, pipes, valves, hoses and the like were not yet invented. A team of some 300 men, women and children did this work. The clay pans, being highly porous, wetted throughout and were ready for evaporation. To make it easy to get the ice out when it formed, the insides of the clay pans were rubbed with butter! The pans had to be rebuttered about every 4 hours during the night. Ice harvesting began around 5 in the morning. If the straw under the pans got wet, no ice would form. The 300 men, women and children had to be ready to replace the straw or reeds during the night if needed. LL. reports that air temperatures at night rarely fell below 40 F. LL. also notes that if there were but the slightest wind no ice would form. The wind part is easy. On clear, calm nights air temperatures near the surface increase with height above the ground. Add a little wind and you mix the warm air from aloft with the cold air at the surface and it doesn't get cold enough to permit the ice to form. Fans and helicopters are used to prevent frost in orchards. Keep the air mixed and prevent frost at the surface. The ice makers of Seerore used well water to fill their pans. The pans had to be filled by dusk so that there would be a maximum of hours of cooling. The pans were filled in the afternoon. Under the hot mid-day sun the water in the pans would warm. Not so. Well water at Seerore used in the ice making season is about 74 F. So during the course of the night water temperatures in the pan fell 42 F! During the day, while the pans were being filled, evaporation prevented the water in the pans from warming in the 95 F heat. In fact the temperatures fell from well water temperatures of 74 F to around 68 F. When the clay pans get old their pores get filled with "gunk" and were not porous enough to permit maximum evaporation. The water in these old pans would warm to 88 F. Pan fillers could tell when the pots were getting too old and needed to be replaced by placing an experienced finger in to the water late in the afternoon. Seerorens were great advocates of evaporation and its "frigorific" effect. Seerorens used tatties to keep their homes cool. Tatties are mats of fresh green bushes or long roots. Tatties were hung in the windows and doorways. Their tatties were kept wet. Air passing through would evaporate the water and cool markedly as it made its way into the house. ***************************************************************** ***************************************************************** *** *** *** *** *** HOW GOOD ARE TATTIES? *** *** *** *** *** ***************************************************************** ***************************************************************** Seerore's tatties seemed to work well. Here is some data from 1792. [In the latter part of the 18th century you could buy thermometers. Jefferson bought his on July 4, 1776. Recreational temperature measurement was the rage!] May 16 and June 7, 1792. 2 PM local time Seerore. Hot days with westerly winds. May 16 June 7 Thermometer in the sun.. 118 F 113 F Thermometer in the shade. 110 F 104 F Thermometer in tattied house. 87 F 83 F So we might ask the question, How hot could a well tattied Seeroren house get? My guess is around 92 F (the Priestly Taylor Temperature) as at temperatures this high or higher effectively all the heat flux from the tatties would be due to latent heat and sensible heating would go to zero. Anyway good tatties will win you some 20 F of cooling. The price you pay for having good tatties is that you humidify the house as you cool it! If the tatties even came close to saturating the air in the house then it would be like living in a penal sugarcane field in Queensland, Australia if British or perhaps on Devils Island if French. ***************************************************************** ***************************************************************** *** *** *** *** *** WHITE MOUNTAIN TREES CONFESS *** *** *** *** *** ***************************************************************** ***************************************************************** The August 19 issue of Science brings us news of the 8,000 year record of annual temperatures extracted from 50-year chunks of tree rings White Mountains bristlecone pines. The ratio of duterium to hydrogen in a growing seasons wood increases with temperature of the growing season. This work was done by Xiahong Feng and Sam Epstein of Cal. Tech. Feng and Epstein report warming from 8,000 years ago to around 6,800 years ago and a cooling since. The magnitude of the cooling was 5 to 7 C. It made the Associated Press before you got your copy of the magazine. [Investors Business Daily had it out to its readers before Science subscribers got it. When we need to get a Science article quick or pronto we go to Investors Business Daily and get a XEROX FAXED to us] Hot stuff. The coldest 200 years in the last 8,000 year record were the 18th and 19th centuries and we are not much different today. The form of this thermal history of the Holocene is repeating news story number umpteen. We have known for many decades that the warmest times of the Holocene was some 6,000 years ago and that we have apparently been coming out of the Holocene ever since. Coming out means heading toward the next ice age. We have also known that the 1700s and 1800s were the coldest of the Holocene and have been dubbed the "Little Ice Age". So what is new is 1) this is a new and independent confirmation of our thermal history and 2) it begs the question "Where is all the global warming?" This tree ring record in basic form is just about the same as the Devon ice core record of past temperatures. Asked by the press about the latter, Epstein, cautions that their findings "do not necessarily counter evidence of the possible greenhouse effect." Possible evidence is pretty tepid stuff. He notes that the "bristlecone findings cannot be related to any models of future changes" because "the modern climate is much more unpredictable." I have not found anyone who can figure-out the basis for that quote. Epstein goes on to say that today there appears to be a "mechanism that is not well understood. When the climate gets a little warmer, the models go a little haywire." You can read Epstein's words in Global Warming Network Online Today in their August 24, 1994 issue. Epstein is reluctant to have findings that are against the models. The power of models in modern society is substantial! Chris Fallon told us (a group of climatologists meeting in Ashville, North Carolina's National Climate Data Center that the IPCC process was "model driven not data driven." He went on the say the observational data didn't matter. If unproved models say it might happen that is good enough. I guess that is what is meant by "possible evidence." In the past I have encouraged CEDers to read Hugh Ellsaesser's 1982 article in Atmospheric Environment titled "Should we trust models or observations? Atm. Env. 16(2):197-205. "Hugh takes the position that we use data to test theories (models) not the other way around. These days we often beat the heck out of the data with sophisticated mathematical and statistical tools until the data yells, "Enough, don't I look like the model output yet!" Anyway, if you read your way around the climate literature these days you will find lots of in-spite-of-my-results statements to placate the modelers and model believers. Well, anyway lets back up and look at one of the Epstein quotes. "When the climate gets a little warmer, the models go a little haywire." It is hard to know what Epistein means by this. It can't be that when the "real" climate gets a little warmer, the models go a little haywire because there is no "real" climate in the models. He may mean that when the model's climate output statistics show a little warming, that the models go haywire. I don't know the literature he is thinking of when making this statement but it implies that when the models indicate warming they also indicate model failure if you equate haywireness with failure. A third possibility is that his regressive model of duterium/hydrogen versus observed temperatures may not be stable at higher temperatures. I think Epstein meant that the Devon ice core and his tree-rings have the timing of the warming in Atlantic times a bit off and the press "twisted his tongue" into lashing out at models. Epstein also notes that "the modern climate is much more unpredictable" than the climate in the earlier Holocene. I don't understand how he comes to this statement on unpredictability. Climate models have yet to be shown to have useful prediction skill for the climates of the last 100 years much less for episodes of the Holocene where we have much less to no data on which to calculate such measures of prediction skill. In short, I don't think Epstein should sell his own observational data short. He may have data on which climate models somewhere or sometime could be tested for skill! He might have real potential evidence in his hands! All in all the Feng and Epstein is worth the read. They have crafted a fine record of climate in the White Mountains of California that track many other time series of Holocene climate. In summary, they chart a cooling between 6800 years ago to 2000 years ago of about 5 to 7 C. Then in the Little Ice Age (1700-1900) it got colder still. The tree-rings indicate that we are about 1/3 of the way out of the Little Ice Age but a long way toward the next ice age if the warmth of 6800 years ago is the starting benchmark. The history of climatological thought for the last 100 years has us swinging back and forth (pendulum like) between dreaming and fearing ice ages and global warmings. It is only newcomers to climatology that keep adding to the manic-depressive momentum of our pendulum, else it might well come to rest. ***************************************************************** ***************************************************************** *** *** *** *** *** LEAFING OUT AND RELATIVE HUMIDITY *** *** *** *** *** ***************************************************************** ***************************************************************** Dateline -- M. D. Schwartz. (1994) Int. J. Biometeorol. 38:18-22 . In the 56 days prior to leafing out in mid-West relative humidity falls at the rate 0.2% per day. Relative humidities in southern Arizona also fall at the rate of 0.2% per day during this time of the year. As these 56 days are marked by the zenith rise in the sun as winter ends, spring moves along and daily maximum temperatures rise some 0.33 C per day, it is not surprising that average relative humidities fall as the leafing out day approaches. Relative humidity is a function of temperature. For a given amount of water in the air, relative humidity falls as temperatures rise. If this process were to continue for the 56 days following leafing out putting us somewhere around mid-July relative humidities in the mid-West would fall to 43%. The average relative humidity at Tucson, Arizona in July compares well with a 43% RH! In the mid-West, relative humidity does not continue to decline but increases with the onset of leaf-out. Over the 56 days following leafing out relative humidity increases 0.09% per day and ends up at 59% by mid-July. Both Tucson and our mid-West air of the same origin in July (maritime tropical) so we are hard pressed to affix the blame on advected wetter air in one place over the other. The increase in relative humidity over the expected decline due to the progression of spring time heating is due to wetting the atmosphere with evapotranspired water. You can increase relative humidity by lowering air temperature or by raising the water content of the air or both. With leafing-out, you wet the air to such a degree that the expected falling relative humidity is overcome and reversed. This change from falling to rising relative humidity happens at the date of leafing-out. At this same time NDVI index increases abruptly as the "green wave" of spring passes. If you get a hold of Mark Schwartz's paper in the International J. of Biometeorology, his other papers on changes in the atmosphere resulting from leafing-out and greening-up are cited. Or, you could page through back issues of CED and get most of them that way as well. ***************************************************************** ***************************************************************** *** *** *** *** *** FITNESS FOR PURPOSE? *** *** *** *** *** ***************************************************************** ***************************************************************** Fitness here is not the genotypic fitness of Wright or Fisher. Snow crystals don't have DNA unless the ice crystal formed around an ice nuclei that was an intact bacterium. B. J. Mason of Imperial College, UK titled his Q.J.R.M.S. (1994), 120:849-860. paper "The Shapes of Snow Crystals -- Fitness for a Purpose? He submitted his little paper on October 11 last and it was revised and accepted 1 February of this year. It made the July issue! It got to Charlottesville in August! Weather geeks don't mess around when it comes to getting their stuff out. This could be because 1) Mason is famous, 2) the journal is ROYAL [QJRMS = Quarterly Journal of the Royal Meteorological Society], or 3) they have been at it a long time and have it right [Volume 120 means the journal started in 1874.] Back to "Fitness for Purpose" among snowflakes. CED readers know of my interest in the biogenic role in snowflake making. So, Mason's little paper made my eyes bug-out! He starts his summary (first line in the contribution) with: "Snow crystals exhibit six quite sharp changes of habit between 0 and -25 C. He wants to know "why." He notes that such changes in morphology are unique in crystal physics. He asks do they, the changes, serve a useful purpose. For me the notion that the role ecosystems play in snow making might have yet another neat twist was great! Besides, Mason published his first paper of snow crystals in 1953 and he just won't give up. Background -- In earlier issues of CED we covered the basics of the role our ecosystems play in the snow business. 1) substances in the air that CAN serve as the nucleus around which an ice crystal can format temperatures warmer than -25 C are biological in origin! 2) these ice nuclei arise from the decomposition (probably bacterial) of litter, 3) litter from different species and litter from different ecosystems produce ice nuclei that work (start an ice crystal growing) at different temperatures, 4) ice in clouds is a tremendous advantage in getting it to rain in the first place and in getting big drops of rain, 5) an ice crystal collects water vapor from the air much faster than a raindrop does, and 6) make probable nice flashes of lightning and rolls of thunder. Back to Mason -- Mason concludes: "the transitions from plates to stellar dendrites (like paper cut-outs in first grade -- ed.) that grow only between -12 C and -16 C, and from plates to columns below -25 C, permit the more effective release of precipitation from the cloud layer. The interruption of the plate growth to columns and needles between -8 C and -3 C leads to larger precipitation elements (read raindrops) that better survive evaporation below cloud base than would plate crystals." Once a crystal forms, which depends on the quality of the ice nuclei which in turn depends on the litter and decomposition, and establishes its crystal form, it may fall through layers with different temperatures and humidities and when it does this it may grow with different kinds of crystals attached to the start up crystal. It can get complex. A six sided plate formed at -25 C and then falls through warmer air say around -12 C could change to a six sided dendrite. The dendrite has great surface area and collects vapor from the air at a rapid rate; and, if it falls through air warmer than 0 C and melts will form a large drop. The larger the drop the better the chance that it will reach the ground before it evaporates. An ice sphere (400 microns) that falls and melts would evaporate completely in 90% relative humidity air in a fall distance of 1500 m. In contrast, a slightly larger drop (670 microns) typical of a dendritic snowflake would shrink only to 600 micros after a 1 kilometer fall in the same air. Getting to be an even slightly bigger raindrop means a much higher probability of reaching the ground. Mason notes that raindrops larger than 0.5 mm are formed by dendritic snowflakes. So to get a heavy rain of big drops you have to make ice at warm temperatures. ***************************************************************** ***************************************************************** *** *** *** *** *** CLOUD ALBEDO AND SNOWFLAKES *** *** *** *** *** ***************************************************************** ***************************************************************** Cloud albedo and snowflakes. If you take a cirrus cloud (an ice crystal cloud) and measure its albedo you will find that the albedo depends on the kinds of ice crystal. A cirrus cloud with plate crystals has an albedo 3 times as large as one with columnar crystals. Mason notes that this has "a significant consequences for the radiation balance, especially of dense, extensive and long-lived anvil cirrus." Given that the kind of crystals formed in cirrus clouds depends on the kind of ice nuclei present and thus depends on the quality of litter and the type of ecosystem below that makes the ice nuclei, the ecosystem has yet another important role in planetary radiation budgets.