Schmid, H.P.

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Schmid, H. P.

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Hans Peter SchmidForschungszentrum Karlsruhe, Garmisch-PartenkirchenTERENO Kick-Off MeetingBerlin, Sept. 22, 2008Atmosphere – Land Surface Interactions:Why do we Need Long-Term Observations ?Page 2What do we get out of long-term observations?Intellectual Motivations and Practical BenefitsIntellectual Motivations for Long-Term Observation Programs• Systems Dynamics: Temporal scales of ecosystem – atmosphere interactions• Diagnostic Science: Detection of trends and analysis of global change impacts• Environmental Science Methodology: Non-manipulative field experimentationPractical Benefits of Long-Term Observation Programs:• Enhance knowledge of complex exchange and transformation processes• Database for model development and testing• Benchmark for global coverage satellite observations• Training ground for young scientists and environmental engineers Page 3(source: IPCC 2001, WG1 Report, Summary)Time Scales of Processes in the Environmental SystemGlobal Mixing of Greenhouse GasesHalfTime of CO2 PulseHalf-Time for CH4 PulseTemperature response to CO2 RiseCO2 Transport to Deep OceanSea-Level Response to T-ChangeIce-Caps Response to T-ChangeAcclimation of Plants to High CO2Life of PlantsDecay of Plant MaterialTechnology ChangeEnergy-Supply Technology ChangeInfrastructure LifetimeSocial Norms and GovernanceSocio-economic process s (society’s memory) tick on a much shorter time scale than their consequences in the environment: We are not very good t thinking in terms of long time effects!Page 4(source: IPCC 2001, WG1 Report, Summary)Process Knowledge of Land-Surface-Atmosphere Interaction is RecentPage 5Short-Term vs. Long-Term ObservationsIn search of the "Ensemble": all possible states of a system(from Wallace and Hobbs, 2006, Fig. 7.26) individual short campaigns show development and transformation paths may be disjunct; generalities not evident: case studies long-term observations (may) make patterns, generalities evident provide a more complete view of the system improve model development and testing capabilitiesPage 6IndianaExample: Forest-Atmosphere Exchange of CO2 (FLUXNET)MMSF Site, Indiana (USA), 1998 – (continuing)Page 71998 1999 2000 2001 2002 2003 2004 2005 2006 2007-35-30-25-20-15-10-505YearCumulative NEE (ton C ha-1 )Cumulative Exchange of CO2 over 9 Years (MMSF)NEE: Net Ecosystem Exchange = Respiration - Assimilation30 tons C ha-1367[g(C)m-2]267[g(C)m-2]304[g(C)m-2]366[g(C)m-2]274[g(C)m-2]418[g(C)m-2]386[g(C)m-2] 360[g(C)m-2]236[g(C)m-2]Sum of ca. 79'000 hourly CO2 flux measurementsPage 80501001502002503003504004501999 2000 2001 2002 2003 2004 2005 2006YearNEP [g(C) m-2 a-1]Annual Net Ecosystem Production (NEP)1999-2003:µNEE : 316 g(C)m-2a-1σNEE:    44 g(C)m-2a-1+2.3 σ+1.6 σwarmest veg. seasondrought in veg. seasonDetection of unexplained variation: opportunity for new insights into ecosystem functionPage 9What can cause these Effects ?... 2004 was the Year of the Brood X Cicada17 year periodical cicada: next emergence in 2021entirely new and unexpected linkagesand mechanisms are being considered(work in progress...)Page 10Höglwald,Upper BavariaExample: Forest-Atmosphere Exchange of N2O (NitroEurope)Höglwald Site, Upper Bavaria, 1994 – (continuing)Page 11Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan0501001502003004005002007200620052004200320022001Cutting2000    spruce control  selective cutting  clearcutN 2O emission [µg N m-2 h-1]2006N2O Emissions at Höglwald Forest Long-Term Sitecontrol & selective cutting: "business as usual"later years:characterized by episodic bursts (thawing events)Page 12leads to detailed process studies, lab experiments and model developmentJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan010020030040050001232006   N 2O emission [µg N m-2 h-1]2006  spruce control  selective cutting  clearcutCumulative N 2Oflux [kg N ha-1]    N2O Emissions at Höglwald Forest Long-Term Site2006 short-term thaw eventsEpisodic events:contribute 50-80% of cumulative fluxImpact of episodic events detected only due to continuous, long-term observationPage 13Conducting Science in the Environment ?source: Science, 22 Aug. 2008, cover Long time series in place of experimental replica Conditional data selection (out of collected time series) in place of experimental control: Field experiments in place of laboratory experimentsLong-term observations provide an essential methodology for environmental science We do not have replicates of the atmosphere, of climate….Page 14Thank you for your attention!

Atmosphere - land surface interactions: Why do we need long-term observations?

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Atmosphere - land surface interactions: Why do we need long-term observations?

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