Newsgroups: lter.ced Path: LTERnet!news From: "Bruce P. Hayden" Subject: CED 2.1 Message-ID: <1993Jan29.184948.6503@lternet.washington.edu> Sender: news@lternet.washington.edu Organization: Long Term Ecological Research Date: Fri, 29 Jan 1993 18:23:38 GMT ***************************************************************** ***************************************************************** *** *** *** *********** *********** ********** *** *** * * * * *** *** * * * * *** *** * * * * *** *** * ********* * * *** *** * * * * *** *** * * * * *** *** * * * * *** *** * * * * *** *** *********** *********** ********** *** *** *** ***************************************************************** ***************************************************************** Vol.2 No.1 :::::: file name:CED2.1 :::::: February 1, 1993 ***************************************************************** ***************************************************************** 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 get to 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@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 (monthly?). Back-releases 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 will keep a LTER wide bibliography on Climate/Ecosystem Dynamics that we pass on via E-mail. ***************************************************************** ***************************************************************** *** *** *** *** *** CED ON HOLIDAY *** *** *** *** *** ***************************************************************** ***************************************************************** Keen watchers of their E-mail in-basket should have noticed a lack of a January 1 CED issue. CED went on holiday. A draft of half of a January 1 issue was finished around the 18th of December. Then the press of sugar plum dancing got the best of me. My family got a higher priority than did CED. To complicate matters, our annual research symposium for the Virginia Coast Reserve LTER was in early January. As you know, having 40 or so researchers in one place requires a lot of pastoral skills. Arrangements for bedding and feeding, slides, projectors and reprint are taxes on time. Mine ran out. So with this issue we begin our second year of "lite" enlightenment on the interactions between climate and ecosystems. I have started my spring seminar class on the same subject and I will pass on to you great discoveries from the class. ***************************************************************** ***************************************************************** *** *** *** *** *** CLOUDS *** *** *** *** *** ***************************************************************** ***************************************************************** Issues ago, I promised a cloud climatology piece for the ecologist. How we like to ignore clouds. They come and go; they look like dragons and hair-balls. They shadow their bottoms and so give the cloud its much-loved silver lining. When I was at the University of Chicago working on my PhD in physiological ecology, I would drive out to northern Indiana (There was no travel reimbursement for graduate students in those days!) to work on my wired trees. I was monitoring water potentials in the trunks. When clouds would pass overhead I would get as much as a 1.5 bars change in water potential. The jagged trace of water potential marked each cloud and its duration. I had a cloud-o-meter and didn't know it. Yes, I was young. Well, my dissertation was on wind and radiation effects on water potentials in beech and so I didn't mention the cloud-thing in my dissertation. Now I can talk as G. Bush and my intellectual colleagues won't tisk-tisk me. Everyone thought it was noise. Everyone has noise in his/her gender-free data. My noise was silent clouds. You might say the trees "felt" every cloud that wisked along with breezes in the sky. If the pigments are not light saturated, well, I guess they are a little less productive even when a most humble cumulus humulus passed by. ***************************************************************** ***************************************************************** *** *** *** *** *** CLOUDS AND APHIDS *** *** *** *** *** ***************************************************************** ***************************************************************** Think of the poor aphid on one of my trees. He is there sucking away. Overhead a cloud casts its shadow on the tree and water tension falls a bar or so. Does his just-sucked-juice get sucked back into the tree. Do clouds facilitate virus exchanges between aphids and trees? Perhaps the aphid is blessed with the capacity to quickly regulate its suction potential when clouds cast a shadow on its work. I didn't plan this little aside. It is interesting to ask these little questions. Any answers? ***************************************************************** ***************************************************************** *** *** *** *** *** CLOUDINESS *** *** *** *** *** ***************************************************************** ***************************************************************** How do we know how much cloud cover we have. Well, before satellites, you had to get station data where cloud cover (in tenths or eights) was estimated and in some cases recorded. Somehow you had to add it all up. In the old days when people were trying to calculate the planetary albedo they had to estimate cloud cover for the earth. If you look at planetary albedo measurements from the first estimate to the recent satellite measurements it gets interestingier and interestingier. In the first method for albedo estimation, measured the sunlight that bounced off earth and hit the moon (You can see the moon even when the earth's shadow is on it!) and then bounced back to earth. Then they estimated the albedo of the moon which was difficult given the blue cheese theory of lunar composition. Pencil-work at this point gave the intrepid calculators about 50% for the albedo of earth. With each new estimating technique, the magnitude of our albedo got smaller and smaller until Stephen Schneider (used to be NCARite now Stanfordite) put the value of 28% in his book on global COOLING and the coming ice age. The regression of albedo against year is fantastically high. Due to cloud-climate change? No. It is just due to more and more sophistication at getting at this global number. Well, global cloudiness is around 50%. If you random walked the globe for a millennium and looked up every time your random watch beeper sounded off, you would see clouds directly above about half the time. ***************************************************************** ***************************************************************** *** *** *** *** *** CLOUD-CLIMATE CHANGE *** *** OVER LAND *** *** *** ***************************************************************** ***************************************************************** What really worries me is cloud-climate change. The GCMs tell us clouds will change with 2XCO2. There is no doubt about it in my mind. Cloud type, height and amount will change. As you know I am a general skeptic when it comes to the specific model output statistics of the GCMs. So I think cloudiness will change in some way! Is cloudiness already changing? Even without the be-all and end-all of global warming? You bet. Most climate variables have had systematic changes during the last 100 years or so. Why not clouds! One of the problems we have had in knowing much about cloud climate is that most of the cloud observations are penciled in on paper data sheets or in paper books. The minions who key-punched themselves to tunnel-carpel syndrome in the 1960s and 1970s did do clouds like cleaning persons don't do windows. In steps, Anne Henderson-Sellers, a go-getter of the first order, went to the dusty old ledger sheets to harvest the numbers: decade upon decade; continent upon continent. What a fantastic job! She could have kept it all to herself but she fessed-up and published her findings promptly. Her time series of cloudiness for North America are for the period 1900 to 1984. Sounds like the stuff long-term ecologists would salivate over. She did it for just about everywhere in North America that is anywhere! Perhaps even a station near you. In addition, she did the same for Europe, Asia and Australia. Herculean stuff. If you feel the need to walk up to her and shake her hand and say well done, you best go to Macquarie University in the subburbs of Sydney, Australia. Henderson-Sellers Data for Stations nearest lower 48 LTER sites _______________________________________________________________ Change in the percentage of the sky covered by clouds 20 year smoothing of annual values (1900-1984) These are differences in percentage (last-first) Andrews Portland +11.3% Roseburg +12.0% Cedar Dubuque +23.6% Des Moines +11.8% Coweeta Charlotte + 9.3% CPR Cheyenne +14.6% Harvard Nantucket +16.3% Hubbard New Haven +19.8% Burlington +13.4% Kellogg Detroit +17.6% Konza Dodge City +14.1% Jornada Roswell +12.9% Niwot Pueblo??? + 6.3% North Inlet Charleston + 8.5% NTL Milwaukee +11.3% Sevilleta Roswell +12.9% VCR Norfolk +23.7% _______________________________________________________________ Tulik Dawson +13.0% Bonanza Dawson +13.0% _______________________________________________________________ Luquillo Key West +12.8% _______________________________________________________________ Data from Henderson-Sellers 1989 P.P.P. 75:175-194. It was chance, just chance that the VCR had the biggest change in cloudiness. In 1900, about 22% of the sky was cloud covered. By 1984 it had increased to 45.6%. In the case of the Norfolk record, much of the change happened before jets and jet contrails. Lots of people have suggested that the jets are doing it. Jet contrails were studied in the 1960 over IOWA. Lots of jets crossed over the central Iowa navigation beacon. Calories of solar energy on a surface were measured for contrail days and non contrail days. There was about an 8% reduction in solar radiation reaching the ground. Most places don't get that much contrail cloud in the sky. While contrails cannot be weeded out of Henderson-Sellers records, these big increases in cloudiness must be important plant-wise! References: Henderson-Sellers, A.(1989). Increasing cloud in a warmer world. Climate Change. 9:267-309. Henderson-Sellers, A.(1989). North American Total Cloud Amount Variation this Century. Paleogeography, Paleoclimatology, Paleoecology (Global and Planetary Change Section), 75:175-194. Henderson-Sellers, A. (1987). Climate is a cloudy issue. New Scientist 23 July. Henderson-Sellers, A. and K. McGuffie. (1989).Sulphate aerosols and climate. Nature 340:436-438. Angell, J.K. 1990. Variations in United States cloudiness and Sunshine Duration between 1950 and the Drought Year of 1988. J. of Climate 3:296-308. Many of you know that cloudiness IS going to decrease WHEN a CO2 warmed world is here -- for sure. The GCMs tell us so. A group at the University of Liverpool studied historical cloudiness records and concluded that when it warmed in the past it got cloudier not less cloudy. (New Scientist, 17 April 1986 p. 24 and 15 January 1987, p. 28.) Now the NASA's ERBE (Earth Radiation Budget Experiment) uses our eyes-in-the- skies (or at least our birds-in-space) to study the impact of cloudiness on the radiation budget. They find that more clouds in a warmer world lessen the overall increase in temperature. So, when it gets warmer you get more clouds. You get more clouds and the clouds lessen the temperature increase. A negative feedback if I have ever seen one. GCMs say fewer clouds yields more warming yields fewer clouds yields more warming. Positive feedback if I have ever seen one. It will be interesting to see who is right: nature based on her (I think it is still a she) history OR our forward looking GCM. For Europe, the U.S and the Indian Sub-continent, Henderson-Sellers found that the historical warming from the 1901-1920 period to the 1934-1953 of 0.3 C was accompanied by an increase in cloudiness of between 3% and 10%. 195 stations were used in these tabulations. Cloudiness increased almost everywhere in the U.S. over that period. Jim Angell has also looked at the changes in cloudiness in the US in recent years. He compared the 28 years 1950-1968 with 1970-1988 and found a 3.5% increase in cloudiness (58% cloud cover to 60% and 2/58 * 100 = 3.5%) and a 1.%2 decrease in sunshine duration. The changes were largest in fall and least in spring. He also found that El Nino years were cloudier and had a lower sunshine duration than non-El Nino years. Jim Angell is at the Air Resources Lab. ERL, NOAA, Silver Spring, Md. The stations he used that are close to LTER sites are: Hartford, CN; Norfolk,VA; Willmington, NC; Grand Rapids, MI; Wichita, KN; Minneapolis, MN; Denver, CO; Albuquerque, NM; El Paso, NM; Portland, OR; Green Bay, WS. Jim is a nice guy and might well pass on his data for stations close to your site. His was a lower 48 study! Sorry Alaska and points at sea. Henderson-Sellers data goes from 1900 to 1984. ***************************************************************** ***************************************************************** *** *** *** *** *** CLOUD-CLIMATE CHANGE *** *** AT SEA *** *** *** ***************************************************************** ***************************************************************** DOE got into the climate business some years ago. One of the fruits of their work was an atlas publication titled "Global Distribution of Total Cloud Cover and Cloud Type Amounts over the Ocean" by Warren, Hahn, London, Chervin and Jenne. It is basically about clouds at sea. The neat thing about the document was the collection of microfiche in the back of the atlas. It had graphs of the historical variation in cloud type and amount. Now that your tongues are watering I can tell you that I think the atlas is still free. Ask for DOE/ER-0406, Office of Energy Research, Office of Basic Energy Sciences, Carbon Dioxide Research Division, Washington, D.C. 80307. You might be able to get it from NCAR as well. In any case, the atlas part is a little on the dull side but the time series are not dull at all. They tell the story that cloudiness at sea has changed over this century! Yikes, Batman is Global Warming here? Stratus clouds off the east coast of North America have increased. It has also increased off the east coast of Asia as well. It is most likely the cloudiness resulting from the plume of sulfate riding downwind from the fuel-using-to-keep-warm, mid-latituders. We don't know if the continental cloudiness increases reported by Angell and Henderson-Sellers is sulfate related or due to some natural process (read: not due to people-kind). ***************************************************************** ***************************************************************** *** *** *** *** *** CLOUDINESS & ECOSYSTEMS *** *** *** *** *** ***************************************************************** ***************************************************************** Well, lets consider that we may well have had a 15% increase in cloudiness and a perhaps an 8% decrease in duration of sunshine over the last 100 years. So what! Cloudiness would mean higher (warmer) night-time minimum temperatures. Nights have warmed in this land of ours. It would mean cooler day-time temperatures. Yes, we see some of that in the record but not as strongly as the warmer nights. Daily temperature range is getting smaller. Sounds like Seattle! Fewer heating degree days and fewer logs for your tepee. A northward shift in the hardiness zones. (We have seen a southward shift!) Cloudiness may not tell us about extreme low temperatures since they always happen on clear nights with clean Canadian air. Well, is that good or bad for our chlorophyll plastid-friends? Less evaporative demand perhaps is also expected. That would mean better water use efficiency. Fewer hours of sunshine could mean less primary production or, just a shift in the fortunes of war between the shade-loving and sun-loving troops is the consequence. Looks like the stuff that FORET modeler types might get all computationally excited about. Well, for you and me it means climate change is here. It has been here for some time and it may go on some more. It may or may not be related to greenhouse warming. The GCMs say cloudiness should be getting lower and lower! It is always fun to beat up on the modelers. They do computer experiments, they pretend the products are predictions and then, eventually, they must live in the bright light of observational data as it comes in. Then they say the observational data must be wrong! Talk about playing the game from behind the 8-ball! ***************************************************************** ***************************************************************** *** *** *** *** *** CLOUDINESS & SUNSHINE DATA *** *** *** *** *** ***************************************************************** ***************************************************************** Data on cloudiness and sunshine histories for U. S. Stations has crossed my desk during the holiday season. I will select from it the data closest to your LTER sites and find a way to get it to you. This is spare time work so you won't get it in the next few days but it will come. ***************************************************************** ***************************************************************** *** *** *** *** *** TUNDRA VS FOREST *** *** DISCUSSION *** *** *** ***************************************************************** ***************************************************************** ITEM FOR DISCUSSION Lafleur, Rouse and Carlson, 1992. (Internat. J. of Clim. 12:193-203) write on "Energy Balance Differences and Hydrologic Impacts Across the Northern Treeline." They find no differences in net radiation on either side of the treeline or in energy flux from ground storage. However, the partitionings of available net radiation into latent and sensible heats are different. The tundra adds more latent heat to the air and the forest more sensible heat. These differences occur when water for evapotranspiration is not limiting. During dry periods the partitioning of energy is little different across the treeline. Under normal moisture conditions the forest has a higher Bowen Ratio than the tundra. The lower part of troposphere warms more over the boreal forest than over the tundra. Sensible heat generated by condensation (latent heat release) from tundra evaporated water would result in mid-troposphere heating. The air has to rise before this can happen. Lafleur and co-workers suggest that movement of the treeline should result in changes in Arctic hydrology as evaporation from the tundra is .2 mm/day greater than the forest. "The treeline represents an important climatological and hydrological discontinuity." It fits the paradigm: vegetation controls climate. In sum, we have a bi-directional climate/ecosystem arrow diagram for the tundra/forest ecotone. DISCUSSION FROM: Tim Seastedt I suppose I should go read the actual literature but, hey, it's cold out there and the library is full of students who realize they have 2.3 days to write 4 term papers. Anyway. The Lafleur et al. 1992 paper. "The tundra adds more latent heat...the forest more sensible heat...when water not limiting. Whoa!...a two-dimensional surface, low LAI evaporates more water than the high LAI forest? This doesn't match stories told elsewhere... Could these be reversed? cheers, trs [aka Tim Seastedt, who knows what the r stands for!] LITERATURE CHECK I Went back to the International Journal of Climatology to see if I got the conclusions of Lafleur all messed up. It was read with skill on my part the first time. Now we must explain conflict trs finds. The Forest does put out more sensible heat than the tundra if water is not limiting. First, the Lafleur study was an observational program. The numbers were measured-fact not model-fact. While the flux of heat from the ground was a bit higher in the tundra than in the forest, the difference was small (1.25 MJ/day vs 0.91 MJ/day), the sensible heat flux from the forest was canopy was higher than from the tundra (4.50 MJ/day vs 3.31 MJ/day). As for evaporation, Lafleur puts it for the forest at 2.24 mm/day for 5.92 MJ/day and the tundra at 2.45 mm/day for 6.84 MJ/day. trs notes this does not match up with stories told elsewhere. Lafleur also notes his observation is a departure from the lower latitude literature on differences between field and forest. For example, see McNaughton and Jarvis (1983) in Kozlowski, T. T. (ed.) Water Deficits and Plant Growth. Academic Press, NY pp. 2-47. The low latitude notion is that the forest is well coupled to the atmosphere where the crop or grassland is poorly coupled. Hold the fort. What is this coupled stuff? Is this yet another case of throwing bucket of cold water at the coupled pair? Actually, coupling has to to do with the maximizing of fluxes of mass and energy from the biosphere to the atmosphere. So, what is it about the biosphere that would inhibit, retard, preclude or minimize these fluxes? Anotomy, morphology, architecture, phenology, chemistry, physics and other things that's what. Mullein, mules ears and garden everlasting are all highly pubescent. Trichomes, tufted, branched, stellate, two-armed, vesiculate, multicellular shaggy, glandular, coiled, peltate, hooked and ordinary types abound. Fuzzy leaves rule the day. Transpired water is trapped within this forest of leaf-hairs. Water loss is minimized. The plant is partly decoupled with the air above. A canopy that is smooth or streamlined is decoupled from the atmosphere relative to a canopy littered with roughness elements. Well, waxed or suberized leaves or sunken stomates also contribute to decoupling. trs -- is krumholtz a decoupling "disease"? We will revisit coupling and decoupling in a later CED. The boreal-tundra coupling comparison is the opposite of that at the lower latitudes. Lafleur suggests, with data, that the tundra is more sensitive to vapor pressure deficits than is the forest. A given change in vapor pressure deficit gives rise to a bigger tundra evaporation loss than the loss from the forest with the same change in vapor pressure deficit. So, if you have some net radiation to get rid of and you have warmed up the leaves [tundra was warmer than forest], the vapor pressure deficit is just that much bigger and the evaporation from the tundra is greater than that of the forest. Are boreal forests less well coupled to the atmosphere than lower latitude forests? Are tundra canopies better coupled to the atmosphere than lower latitude grasslands and fields? Is either, each or neither statement true? I guess I would look to the forest for the answers. First, the forest in the comparison in this case is a tiaga type boreal forest. To use the term closed canopy might be stretching it a bit. The roughness elements would seem to maximize the coupling with the atmosphere. Lots of mixing due to regional wind flow is expected. Energy and mass fluxes from the surface might them be maxed-out. If, however, the winds are often very low to calm (We are in the higher latitudes with high coriolis and low winds as needed by passive fliers like blackflies and mosquitos to move about.) then dumping mass and energy to the atmosphere is more problematic. Wind data is a little hard to come by but I found the following. In the area of the Lafleur study and over the latitude band 60 to 70 N the percentage of days in June, July and August with winds 17 kts or greater is 1.0, 1.4, and 2.3 respectively. In the 50 to 60 band immediately south the average percentages are 3.7, 3.8 and 3.2. Down in places like west Texas one might expect up to 20% of the days in summer have winds in excess of 17 kts. If the number of calm days is important in the statistical outcomes, Lafleur's data or a similar set of data near Hudson's Bay where it is windier might provide the data. It does seem strange. The tundra gets warmer than the forest but the forest has a higher sensible heat production. There are three ways to transfer the heat available to the atmosphere [radiation, conduction and convection]. Radiation according to the paper is little different forest or tundra. Conduction only gets the heat from the leaves to molecules that come in contact with the leaves. Since air density and winds were the same it is hard to make the case for conduction. That leaves convection. A difference in windiness could explain the observations but we have no evidence of a difference in winds at these two fairly close together sites. That leaves convection helped out by the roughness elements of the surface -- heated spikes and spires do best. Sounds like a black spruce doesn't it. In my view, the architectural differences between forest and tundra is important to the mass and energy fluxes from these landscapes. The tundra and the forest had essentially the same albedo. The net radiations for the two sites were almost the same as well. The trees of the forest, although slightly cooler than the tundra, act as convective chimneys and thus may facilitate sensible heating of the atmosphere buy maximizing convection even when wind speeds are nil. David Greenland [Andrews and Niwot experienced] is also "scientifically" bothered by the conclusions of the LaFleur results. And on helping me on this issue of CED suggested another LaFleur and Rouse paper "The influence on surface cover and clmate on energy partitioning and evaporation in a subarctic wetland." in Boundary Layer Meteorology 44:327-347. Lets all have a look at that paper and revisit the subject. This issue of CED needs to go to the wire. Other comments from our network welcome. ----------------+--------------------------------+------------------------- Bruce P. Hayden | Dept. Environmental Sciences | bph@virginia.EDU (804) 924-0545 | Clark Hall, Univ. of Virginia | bph@virginia.BITNET (804) 924-7761 | Charlottesville, VA 22903 | (804) 982-2137(fax) ----------------+--------------------------------+-------------------------