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DTSTAMP:20260609T172213Z
DESCRIPTION:Eingeladen durch Prof Foken.It is a common fate of long-term ec
 osystem observation programs that\, after some years\, the merit of contin
 uation is put to question. The reason for such doubt in their value is not
  due to operating costs alone\, but is rooted in the common view that long
 -term observations smack of “monitoring”: simple stockpiling of data\, pas
 sive lying in wait for potential serendipitous discoveries\, endeavors tha
 t have little in common with the accepted way to conduct hypothesis or que
 stion driven research. Our claims and postulates are examined at the hand 
 of examples of long-term measurements of ecosystem-atmosphere exchange mea
 surements over forests in the US Midwest and Southern Germany. We argue th
 at a comprehensive long-term observation program\, with continuous data qu
 ality control\, analysis and interpretation\, combined with modeling\, goe
 s far beyond mere fishing for serendipity. Such programs are invaluable to
 ols to detect the scales of environmental variability and long-term trends
 \; they form the basis for the identification of anomalies and their under
 lying processes\; they are the most important data source for the independ
 ent evaluation of Earth-system-climate models. The most obvious significan
 ce of continuous long-term observations is their utility for continuous ev
 aluation of a model over long time periods. A more subtle point arises fro
 m the recognition that every environmental observation site is to a certai
 n extent unique\, and thus the dimensionality of the manifold of drivers a
 nd forcings in which a measured parameter assumes a given value at a given
  time is very large. In consequence\, every observation must be seen a-pri
 ori as a unique value in a non-stationary\, non-homogeneous field\, collec
 ted in a unique set of conditions. Without the availability of an associat
 ed value\, to which it can directly be compared (e.g.\, a known reference)
  it is not possible to obtain a well constrained estimate of its uncertain
 ty. Without a measure for uncertainty\, the utility of such observations f
 or comparison with others or with modeling results is jeopardized. However
 \, if the data point is embedded in a comprehensive long-term series\, inc
 luding observations that characterize the environmental forcing conditions
  in which the data were collected\, it is possible to stratify the data se
 t and objectively select a sample with comparable environmental conditions
 . Because the stratified sub-set exhibits a degree of homogeneity\, it is 
 permissible to use it for statistical analysis and uncertainty estimation.
  Clearly\, the probability that a sufficient number of data points that me
 et given comparability criteria within a narrowly stratified data set can 
 be identified\, increases with the length of the data series. Thus\, long-
 term observations provide an essential tool for environmental science to e
 scape a fundamental methodological dilemma.  
DTSTART;TZID=Europe/Berlin:20100715T161500
DTEND;TZID=Europe/Berlin:20100715T174500
LOCATION:H6
SUMMARY:Prof. Dr. Hans Peter Schmid\, Institute for Meteorology and Climate
  Research (IMK-IFU)\, Garmisch-Partenkirchen: How long is long enough in e
 cosystem observation?
TRANSP:TRANSPARENT
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