Newsgroups: lter.ced Path: LTERnet!news From: envsci.evsc.virginia.edu@ux1.cso.uiuc.edu Subject: CED 1.3 Message-ID: <1992Apr27.143716.1640@lternet.washington.edu> Sender: news@lternet.washington.edu Organization: Long Term Ecological Research Date: Mon, 27 Apr 1992 14:34:16 GMT ***************************************************************** ***************************************************************** *** *** *** *********** *********** ********** *** *** * * * * *** *** * * * * *** *** * * * * *** *** * ********* * * *** *** * * * * *** *** * * * * *** *** * * * * *** *** * * * * *** *** *********** *********** ********** *** *** *** ***************************************************************** ***************************************************************** Vol.1 No.3 :::::: file name:CED1.3 :::::: May 1, 1992 ***************************************************************** ***************************************************************** 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 Hayden by the file name given in the masthead. 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. ***************************************************************** ***************************************************************** *** *** *** *** *** GRASSLAND LTERS IMPLICATED IN *** *** FLORIDA CITRUS FREEZES *** *** *** ***************************************************************** ***************************************************************** We tend to think of climate change in terms of rainfall and temperature changes rather than changes in the systems that make possible the rain or temperatures we experience. Most climate changes arise from changes in the frequency, magnitude and geography of synoptic weather systems. Recently Rogers and Rohli (1991) went to the bother of counting from daily weather maps the number of high pressure cells over the North American Prairies. It was a winter season study and the object was to understand freezes to the citrus crop in Florida, but our grassland LTER can benefit anyway as the cold air that reaches Florida and makes frozen orange juice usually crosses the prairies rather than the forest biomes of eastern North America. The high pressure cells Rogers and Rohli were interested in were the of the "mother of all high pressure cells" type. In the early decades of this century 15 to 20 such mothers occurred each decade. In the middle part of this century 5 to 10 occurred each decade. Now that is an interesting climate change. Are we returning to the climate state where these "Siberian express" class high pressure cells with very dry air and very cold temperatures are common? Since the 1950s the trend has been to more of them and colder winters in the East and Southeast. However, climatologists usually refrain from extrapolating from "eye-ball fitted" polynomials of such data unless they are in search of new research money to support a new brood of graduate students or a trip to ESA in Hawaii. Y AXIS = NUMBER OF 1045 mb HIGH PRESSURE CELLS CED BAR Graph +----|--------|--------|--------|-------|---------|----| | | 25 | | | | | *** | | *** | 20 | *** | | *** *** | | *** ****** | | *** ********* | 15 | *************** | | ****************** | | ****************** ***| |********************* ******| 10 |********************* *** *********| |************************ ****** ****** *********| |************************ ****** ****** *********| |************************ *************** *********| 5 |******************************************************| |******************************************************| +----|--------|--------|--------|--------|--------|----| 00 15 30 45 60 75 09 24 39 54 69 84 The frequency of occurrence by decades, overlapping at 5-year intervals, of the number of 1200 UTC anticyclones during November-March in the Great Plains with central pressures exceeding 1045 mb, 1899-1989. [For higher resolution illustration see Rogers and Rohli, 1991. J. of Climate 4:1103-1113]. While Rogers and Rohli don't make much of it, inquiring minds want to know why the orange orbs are at risk to Canadian air masses that cross the prairies on the way to Florida rather than crossing the forests of eastern North America. Do the forests of the east protect the warm-air-loving plants of Florida? Their means to do this is by evapotranspiration. By making the air richer in water vapor the dew point temperature and the daily minimum temperature are elevated. Canadian air which crosses the non-transpiring grasslands wets the air less than the even-in-winter partly active forests of the east. Establishment of this hypothesis awaits a bright young mind. In April Canadian air moving across Virginia from the Blue Ridge to the VCR gets a dew point temperature rise of about 4 C. Our coast is mild in part because of the sea of water to the east and in part due to the sea of trees to the west. The Virginia count of cold air outbreaks (<0 C) with no snow on the ground indicates that, other than 1934-1936 when there were a bunch of cold snaps, only 4 outbreaks happened between 1919 and 1958. We have had many since 1958 and there were many before 1918. That's climate change for you. (Michaels, P. J. 1990. Southeastern Climate Review 1(4):3-12.) ***************************************************************** ***************************************************************** *** *** *** *** *** FRESH LEAVES CONTROL CLIMATE *** *** *** *** *** ***************************************************************** ***************************************************************** As the days grow longer in the spring [they grow longer fastest at the time of the spring equinox] average daily maximum temperatures increase a little each day. Prior to the arboreal unfurling of blades temperatures rise about 0.33 C each day. After the leaves are out and pumping water out the excess radiation is vented by evaporation as latent heat rather than sensible heat. The rise in daily maximum temperatures slows to around 0.07 C per day. Well all that should result wetter air. Is it so? Below we look at water vapor pressure in the air before and after leafing out. Y VAPOR PRESSURE IN mb CED Graph | | # 13 | | # # | | # | | # # | | # # | | # 11 | | ## # | | # # | | # # # | | # | | # # 9 | | # | | # # | | | | # # | |# 7 | | | ## | # | | # ## | | ### | 5 | # # # ### | | # # # ## # | | # # ### | |# | | | 3 +|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| -49 -42 -35 -28 -21 -14 -7 0 7 14 21 28 35 42 49 56 DAYS BEFORE AND AFTER FIRST LEAF (This was a bit of a hard graph so better see article.) Before leafing out the rate of increase of water vapor i the air was 0.03 mb per day and after leafing out the rate increased to 0.14 mb per day. I know that those small number of millibars per day cause a loud SO WHAT! Well here is the so what. .03 mb/d = 0.04 C/d increase in minimum temperatures while the .14 mb/d would mean a 0.20 C/d. When the evapotranspiration starts in the spring and the air gets wetter at a fast rate the days till the end of the frost season are numbered. Leafing out brings on a longer growing season! How is that for vegetation control of climate. My estimates for Virginia indicate that the growing season at screen height (that's the height of thermometers) is some 30 days earlier than it would otherwise be because the trees leaf out early because the frost free season [given nocturnal temperature inversions on cold nights] at canopy elevation ends much earlier than at the ground. Now, if you have a place like a prairie, a place without trees to moisten up the air early in the spring, the air stays dry, dewpoint temperatures low and so minimum temperatures are low and so the beginning of the frost free season comes late! Doubting Thomases will need to go to a document like the U.S. Climatic Atlas to see those isolines of date of the start of the frost free season dip deeply southward over the prairies. ***************************************************************** ***************************************************************** *** *** *** *** *** Arboreal Oases *** *** *** *** *** ***************************************************************** ***************************************************************** In his famous Notes on the State of Virginia, Thomas Jefferson, Mr. Jefferson for those of us who live in the Commonwealth, worried about the climate change that will come when the trees are cut down! He said we had better start a network of weather stations, one in each county, and begin to keep long term records to track the climate changes with deforestation! Wily readers of CED will find pleasure in Taha, Akbari and Rosenfield 1991. Heat Island and Oasis effects of Vegetative Canopies: Micro-meteorological Field Measurements. Theor. Appl. Climatol. 44:123-138. To put their results in one pithy sound-bite we end up with "a forest patch in a dry grassland sea is a nightime heat island and a daytime oasis." Now that is the best of all worlds! But then the study was done in California. In their forest patch the days were 6 C cooler and nights 2 warmer. Evaporation reduces sensible heating in the day and the water vapor in the forest air retards radiative cooling at night. Water vapor is our very best greenhouse gas. One estimate of water vapor in a desert oasis recorded the oasis air as having a vapor pressure 5 mb higher than the surrounding desert air. 5 mb worth of water vapor would raise dewpoint temperatures about 7 C. Now in the Sahara desert where this oasis in question was located dewpoint temperatures are dangerously close to 0 C (that's 32 F) and a 7 C elevation of dewpoints could well prevent freezing temperatures. A nice radiatively warmed heat island is the desert oasis. Come to my tent or you will get cold! Well, just what were the average temperatures in the US before we whacked down all the trees. Were daytime temperatures cooler and night temperatures warmer? Did the beginning of the frost free season come earlier in the spring and end later in the fall? So, do we have an answer for Thomas Jefferson. Well, not yet. But we are coming around to the point were we now think the thoughts that vegetation may have more of a control on climate than our mentors told us they had. Perhaps there is relief in Charleston, S.C. Prior to the unfortunate war most of the coastal plain was de-treed in favor of cotton especially. In the post WWII (that is our fortunate war) more than 50% was put into pine plantations. Anyway there was a shift to forest from vegetation of less stature. AUGUST THEN AND NOW 1824-1854 1950-1980 Change _________________________________________________________ | Tmin 70.2 F 71.2 F +1.0 F | | Tmax 89.5 F 88.8 F -0.7 F | | Tave 79.9 F 80.0 F +0.1 F | | | | T Range 19.3 F 17.6 F -1.7 F | _________________________________________________________ The 1.0 F (0.6 C) change in minimum temperature would mean an increase in vapor pressure from 20.630 to 21.288 or a specific humidity increase from 15.37 g/m3 to 15.83 g/m3. A change of 0.46 g/m3. The latent energy needed to wet the air that much by evapotranspiration would be 15 W/m3. Model studies of deforestation predict a specific humidity decrease of 1.5 g/m3 and cooler mornings by about 3 F (1.8 C). It would be nice to know if South Carolina was now an "oasis" compared to the way it once was. It would be nice to have good land use data for the deforested and forested times in the US. There is some old climate data around. ***************************************************************** ***************************************************************** *** *** *** *** *** GLOBAL CONSENSUS? *** *** *** *** *** ***************************************************************** ***************************************************************** Mr. Albert Gore Jr. of Tennessee recently commented to an Atlanta Constitution reporter about a "few odd scientists who challenge the global consensus" on "global warming." Mr. Gore says, "But the fact is that there is warming, and linkage between warming and CO2 emission is really a very settled question. There is not much disagreement on this at all. There is a very broad scientific basis of opinion on this. Some people mistakenly believe there is a 50-50 split on this whole issue. Actually, it's more like 99 to 1 ratio of those who believe it versus those who don't." We are blessed with some real survey data on the subject of Mr. Gore's musings. The Gallup Organization last October 1, 1991 polled 400 members of the American Meteorological Society and the American Geophysical Union. On the question is there global warming and is it due to carbon dioxide, 35% said yes and 65% concluded otherwise. [3% polling error] Mr. Gore's 99% [polling error not made public] may well include a bryologist or two, at least a pseudopod marine protozologists and a procto.... that the Gallup Organization missed in their search of scientists who should be in the know. In case you wondered why you and a bunch of your friends didn't hear of Mr. Gallup's poll of talk-about-old-stick-in-the-mud, atmospheric scientists, well, you would have if you paid for the Boston Globe (home of the aforementioned AMS) but it appears that most newspapers considered it non-news. Even the New York Times did not deem Mr. Gallup's poll as fit to print. At the University of Virginia we call people Mr. as in Mr. Jefferson. Only people in the medical and education schools call each other Dr. This and Dr. That. Well, Mr. Gore is soon off Rio Earth Summit and Mr. I am off to my curmudgeon refresher course. ***************************************************************** ***************************************************************** *** *** *** *** *** NIGHT TIME WARMING *** *** & LENGTH OF GROWING SEASON *** *** *** ***************************************************************** ***************************************************************** CED readers by know know that global warming may first show up as night time warming, little change in daytime maximum temperatures, wetter air, more clouds, and the consequences of these kinds of change. One of the kinds of associated changes that we might expect is changes in the length of the growing season and perhaps increases in the growing degree days as a result of higher minimum temperatures. LTER will look more and more like Andrews! Global warming remains a concern in spite of our inability to detect it. From my desk I see it mostly as a night time problem. More CO2 and perhaps a wetter atmosphere makes for a stronger nocturnal greenhouse with elevated temperature minima. That may not send Time magazine style sand dunes to Chicago but it should increase the length of the growing season. In Virginia the the relationship between the length of the growing season, at the surface not up in the forest canopy, and night time warming is 6.1 days longer for each 1 F rise in minimum temperatures. The normaland global average called for warming due to 2xCO2 is 2.7 C (4.8 F) or 29.3 days longer growing season in my garden. In Pennsylvania is is 6.5 days per 1 F and 31.2 days for a doubling of CO2. In Maine it is 7.0 for 33.6 days longer growing season for 2XCO2. Georgia 7.4 days per degree for 35.5 days longer growing season. So a first order rule of thumb, perhaps a greener thumb, might be double CO2 and get a 1 month longer growing season. Does the increased production during a longer growing season off-set increased respiration by a 2.7 C warming mostly at night? How does CO2 fertilization add to the balance? ____________________________________________________________ ESTIMATES OF GROWING SEASON LENGTH INCREASE DUE TO 2XCO2 ____________________________________________________________ North Inlet ------- 5.8 d/degree 27.8 days VCR --------------- 6.8 d/degree 32.6 days Kellogg ----------- 9.5 d/degree 45.6 days Harvard Forest ---- 6.8 d/degree 32.6 days Coweeta ----------- 5.1 d/degree 24.6 days Hubbard Brook ----- 7.1 d/degree 34.1 days Barrow ------------ 5.3 d/degree 25.2 days Fairbanks --------- 5.4 d/degree 25.8 days Rhinelander ------- 6.3 d/degree 31.8 days North Inlet ------- 7.6 d/degree 36.6 days Andrews ----------- 12.5 d/degree 60.0 days Jornada ----------- 4.5 d/degree 21.6 days Cedar Creek ------- 4.8 d/degree 31.2 days CPER -------------- 5.1 d/degree 24.6 days ____________________________________________________________ In addition to increases in the growing seaons the number of growing degree days should also increase but I have not yet spread-sheet to that task. I will save that for a later CED. ***************************************************************** ***************************************************************** *** *** *** *** *** CED OZONE UPDATE *** *** *** *** *** ***************************************************************** ***************************************************************** In our last issue of CED we had some fun with NASA and Ozone under the guise that we are at risk at the Trout Lake meeting. It turned out that we were more at risk from the fungus than UVB in Wisconsin's winter. Well the Shuttle is back from its last earth watching mission. They worked hard on the ozone again. Said it would produce the "best data ever." The results seem to have fallen under the heading of non-news. Just a little peep here and a little peep there. They reported, the newspapers did not, that Pinatubo had destroyed some ozne. Well just what is in the Pinatubo plume that it threatend our Ozone layer? Halogens! Chlorine, Fluorine and Bromine it seems. It makes you wonder about old Mt. Erebus in Antacrtica (77.5 S latitude). It stands at 3794 m. It pops off often but is hidden in clouds most of the time. What do they do to the Ozone hole? May looks like a busy month but we will try to meet our desire to issue CED near the end of May. ***************************************************************** ***************************************************************** *** *** *** *** *** KANSAS LIGHTNING *** *** KONZA PRAIRIE ALERT *** *** *** ***************************************************************** ***************************************************************** Some years back in my climate-ecosystems dynamics class we looked into thunderstorms. Farmers told us thunderstoms were not random. They took tracks and any farmer worth his salt knew from which of several ways they would come and how many minutes they had to get the hay to the barn. Card-carrying meteorologists thought random at the landscape scale. It was just chance who got hit!. We looked at the records of class 3 radar return signals. We got 15 years of data did up the averages and did a PCA on the data. Bull'seye! There were thunderstorm bull'seyes. First we did it for Florida (see See Michaels et al., Monthly Weather Review 115(11):2781-2791) attributed it to Florida's sea breeze circulation. Then we went on the Virginia and we found bull'seyes there also. We we had better look at a billiard-table like state: What better than Kansas! Bull'seyes! It wasn't random. Nothing in the atmosphere would explain the landscape scale maxima and minima. Perhaps the landscape was somehow responsible for the geography of radar echoes. The work languished on my self for some time. How could we explain what we see. In the mean time the national lightening strike recording network was getting its act together. They publish their work. [Orville, R. E. 1991. Annual Summary: Lightning Ground Flash Density in the Contiguous United States -- 1989. Monthly Weather Review 119:573-577.] Well, lightning strike geography for Kansas looked like one of the PC of our PCA analysis of Kansas radar echo returns. I have sketched, in a CED map, the Kansas mother-of-all-bull'seyes of lightning flashes for you below. Go and see Orville's map for the real thing. Does a square kilometer of Konza Prairie get 7 to 8 strikes per year. CED MAP OF KANSAS ___________________________________4_______5______________5___________ |..............1....2......3......4......5........6666......5..........\ |..............1....2......3.....4.....5.......6.......6......5......__/ |..............1....2......3.....4....5......6...........6......5...| |.............1....2.......3.....4...5....6.....777.......6.......5..\ |.............1....2.......3.....4...5..6.....77...7.......6.......5.|____ |.............1....2......3.....4...5..6.....7......7.......6........5.5..\ |............1....2.......3.....4...5.6......7......7........6...........5.5 |............1....2.......3.....4...5.6......7......7........6.............| |............1....2.......3.....4...5.6.......7....7........6..............| |...........1.....2.......3.....4...5.6........7..7........6...............| |..........1.....2........3.....4...5..6........77........6................| |.........1.....2.........3......4...5..6..................6...........55555 |........1.....2..........3.......4...5...6.................6.....5555.....| |.......1.....2...........3........4...5....6................6...5.........| |.....11.....2............3.........4....5....6...............6..5.........| |....1......2............3............4....5....6..............6..5........| |...1......2...........3................4....5....6.............6..5.......| |..1......2..........3....................4....5....6...........6..5.......| |.1.......2........3........................4....5....6........6...5.......| 1........2.......3............................4....5....6......6...5.......| |.......2.......3..............................4....5.....6...6...5........| |_______2______3________________________________4____5______6_____5________| ANNUAL LIGHTENING FLASH DENSITY CONTOURS IN FLASHES/KM^2 My radar analyses were for 15 years of data and this is one year of lightning flashes. There are differences. I am dusting off my old students study of radar echo returns. With a bit of time and perhaps an interested student something could come of that class project. ***************************************************************** ***************************************************************** *** *** *** *** *** COMMING CED ATTRACTIONS *** *** *** *** *** ***************************************************************** ***************************************************************** I have started work on a little contribution of decomposition as a source of nucleating agents for cloud formation. I found a neat little article. Inquiring minds want to know things like "Is cloud formation linked to decomposition?" I know it sounds crazy. But crazy doesn't mean bad. Anyway I will work on it. Decomposition driven clouds sent me to the phytoplankton - DMS - Clouds over oceanic areas. Gee to the critters make clouds there also? I have a little story on that for next time and a bibliography on the subject. I will also turn my attention to the Alaska CC meeting and to some new work on the thermodynamics of boreal and tundra ecosystems relative to climate control. Snow melt on the tundra -- it has always interested me and I will pass along some thoughts on tundra snow melt and planetary climate seasonality control. In addition, I will find along the way the detritus of others work which when viewed though the rose colored glasses of climate-ecosystem interactions glow with interest. **************************************************************************** *** NOTICE: I any of the CED graphics get junked-up in transmission drop me a line. **************************************************************************** ***