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Recent Visitors
23 - 27 June 2007: David Schwartzman, Howard Univ. Seminar on Monday, June 25th, 10:30am, in B0.004.
08 June 2007: Ning Zeng, Univ. Maryland. Seminar on Friday, June 8th, 10:30am, in lecture hall.
06 June 2007: Yareni Perroni Ventura, Institute of Ecology, Mexico. Seminar on Wednesday, June 6th, 10am, in B0.004.
07 - 12 May 2007: Visit by Marc Stieglitz, Georgia Tech. Seminar on Monday, May 7th, 2:00pm, in C2 seminar room.
26 - 30 March 2007: Visit by Matt Bandel, Univ. Utrecht.
13 - 14 November 2006: Visit by Basil Davis. Seminar on Monday, November 13th, 3:00pm, in B0.004.
11 October 2006: Visit by Stan Schymanski. Seminar at 11:00am, in B0.002.
02 - 05 October 2006: Visit by Roderick Dewar. Seminar on Wednesday, October 4th, 11:15am, in B0.002.
15 September 2006: Visit by Wolfgang Buermann. Seminar at 11:15am, in B0.002.
Recent Activities & Presentations
21 - 25 May 2007: AGU spring meeting.
10 - 11 May 2007: workshop on Maximum Entropy Production in the Earth system. MPI for Biogeochemistry, Jena. link.
15 - 20 April 2007: EGU Meeting, Vienna, Austria. link.
12 - 14 February 2007: retreat of institute, Oberhof.
11 - 12 January 2007: GINKGO workshop, Jena.
11 - 15 December 2006: AGU Fall Meeting, San Francisco, California. link.
November 2006: CLASSIC workshop, Gregynog, Wales.
14 November 2006: Oberseminar bioinformatics, Uni Jena, 4:00pm. (talk, link ).
09 November 2006: Colloquium talk, MPI-BGC, Jena, Germany, 2:00pm. (talk).
October 2006: Prediction in Ungauged Basins workshop, Corvallis, Oregon. (talk, link).
September 2006: Biohydrology 2006 conference in Prague, Czech Republic. (talk, link).
April 2006: Poster presentations at the EGU conference, Vienna. (link).
March 2006: Talk on Maximum Entropy Production and the Earth's Biosphere at the ocean and climate lunch seminar series (link) at MIT. (pdf Δ).
January 2006: Presentation at American Meteorological Society meeting. (pdf Δ) An audio recording of the presentation can be found here.
January 2006: Presentations at 1st iLEAPS Science Conference: Does land cover change improve or deteriorate the climatic conditions for vegetation productivity? (pdf Δ) ; Validating Optimized Vegetation Parameters with Climate Reanalyses. (pdf Δ)
January 2006: Graduate student poster (Ryan Pavlick) given at Dynamics Days 2006, Bethesda, MD. Title: Maximum Entropy Production and Optimally Adapted Vegetation. (pdf Δ)
December 2005: Presented at the AGU Fall Meeting: Maximum Entropy Production and Climate-Vegetation Interactions. (pdf Δ)
October 2005: Maximum Entropy Production in the climate system, seminar at the Joint Global Change Research Institute, University of Maryland.
September 2005: Gaia and Beyond: What is the role of life in the Earth system?, seminar at the Department of Geography, University of Maryland.
Recent Papers
The climate sensitivity to human appropriation of vegetation productivity and its thermodynamic characterization by Axel Kleidon, in press in Global and Planetary Change, 2006.
Abstract. Humans appropriate terrestrial productivity to meet their food supply, their primary source of free energy. Removal of productivity from terrestrial vegetation has its direct impacts in that less energy is available for vegetation growth. Since vegetation strongly shapes the physical exchange of energy, water and momentum at the land surface, a lower ability for vegetation growth should affect this surface exchange, the overlying atmosphere, and therefore climate. Here I attempt to quantify the climate sensitivity to different intensities of human appropriation of vegetation productivity. I use sensitivity simulations with a coupled dynamic vegetation-climate system model of intermediate complexity in which I artificially remove different fractions of the simulated net primary productivity to implement human appropriation, thus reducing vegetation growth in the model. The simulations show noticeable differences in the surface energy- and water balance, with a consistent reduction in the amount of absorbed solar radiation and latent heat flux of up to 10 W m^-2 and 27 W m^-2 respectively and a reduction in continental precipitation by up to 30% in the global land mean when compared to the "Control" climate. However, the study also shows that mean land surface temperature is insensitive at the global scale despite pronounced regional patterns and is therefore not well suited to characterize the climatic sensitivity to land cover change at the global scale. I motivate the use of entropy production to characterize climate sensitivity. Entropy production is a thermodynamic measure of the strength of dissipative processes which perform physical work. With this measure, I show that the climate sensitivity is reflected as a clear trend towards less entropy production over land with increased intensity of human appropriation of NPP in general, and less entropy production by biotic activity in particular. I conclude that large-scale land cover changes are likely to lead to a noticeably different climate which is less favorable to biotic productivity and that this climate sensitivity is well captured by differences in entropy production as a meaningful, thermodynamic measure. (link).
Keywords: terrestrial vegetation, land cover change, human appropriation, climate sensitivity, thermodynamics, entropy production
Maximum Entropy Production and the Strength of Boundary Layer Exchange in an Atmospheric General Circulation Model by Axel Kleidon, Klaus Fraedrich, Edilbert Kirk, and Frank Lunkeit, published in Geophysical Research Letters 33, L06706.
Abstract. Boundary layer turbulence plays a central role in determining the strength of the overall atmospheric circulation by affecting the intensity of exchange of heat, mass, and momentum at the Earth's surface. It is often parameterized using the bulk formula, in which the von-Karman parameter plays a critical role. Here we conducted a range of sensitivity simulations with an atmospheric general circulation model in which we modified the strength of boundary layer turbulence by varying the von-Karman parameter. These simulations show that the maximum of entropy production associated with boundary layer dissipation is consistent with the observed value of the von-Karman parameter of 0.4 and maximizes the planetary rate of entropy production with the global radiative temperature being close to its minimum value. Additional sensitivity simulations were conducted with an increased concentration of atmospheric carbon dioxide, which affects the relative radiative forcing of tropical vs. polar regions. We find that the global climate sensitivity is more-or-less independent of the assumed strength of boundary layer turbulence in our idealized setup. The difference in climate sensitivities of tropical and polar regions is at a minimum at a climatic state of MEP. (link)
Quantifying the biologically possible range of steady-state soil and surface climates with climate model simulations by Axel Kleidon, published in Biologia, Bratislava, 61/Suppl. 19: S234-S239, 2006.
Abstract. The terrestrial biosphere shapes the exchange fluxes of energy and mass at the land surface. The wide variety and diversity of plant form and functioning can potentially result in a wide variety of possible climatic conditions at the land surface and in the soil, which in turn feed back to more or less suitable conditions for terrestrial productivity. Here, I use sensitivity simulations to vegetation form and functioning with a global climate model to quantify this possible range of steady-states ("PROSS") of the surface energy- and mass balances. The surface energy- and water balances over land are associated with substantial sensitivity to vegetation parameters, with precipitation varying by more than a factor of 2, and evapotranspiration by a factor of 5. This range in biologically possible climatic conditions is associated with drastically different levels of vegetation productivity. Optimum conditions for maximum productivity are close to the simulated climate of present-day conditions. These results suggest the conclusions that (a) climate does not determine vegetation form and function, but merely constrains it, and (b) the emergent climatic conditions at the land surface seem to be close to optimal for the functioning of the terrestrial biosphere. (link)
Keywords: vegetation, climate, atmosphere-biosphere interactions, feedbacks, Maximum Entropy Production.
Our book on entropy production is published by Springer-Verlag.
Attach:/Research/book.jpg Δ Citation: Kleidon A, Lorenz R D (eds) Non-Equilibrium Thermodynamics and the Production of Entropy: Life, Earth, and Beyond; Springer Verlag, Berlin, Heidelberg, 2004.
Springer Webpage (link)
Amazon.com (link)