Impatto dello schema di post processamento dei dati eddy covariance nella stima del bilancio del carbonio degli ecosistemi terrestri
Author(s)
Trotta, Carlo
Date Issued
April 13, 2012
Type
Doctoral Thesis
Abstract
For several decades studies on the causes and e ects of climate change
have become the subject of discussion not only in environmental sciences
but also in many other disciplines (economics, sociology, medicine, etc..).
Among the causes of climate change, the increase of carbon dioxide (CO2)
into the atmosphere, is considered one of the main factors that a ect this
phenomenon, then, most of the scienti c community's e orts are directed to
an improved understanding of the mechanisms that regulate and in
uence
the carbon cycle. Terrestrial ecosystems are a major component of the car-
bon cycle en e ect, through the processes of photosynthesis and respiration,
are able to sink or source CO2 into the atmosphere and directly in
uen-
cing the Carbon Balance (CB). One of the main techniques used to measure
CO2 exchange between terrestrial ecosystems and the atmosphere is (Ed-
dy Covariance, EC). With the EC measurements, in addition to measuring
the exchange of CO2, it was possible to quantify and understand the role
of terrestrial ecosystems in the carbon cycle but also to develop, validate
and apply a wide range of models. The EC measurements, before their use,
require some corrections. A rst phase of corrections cover data measured
directly in the eld (raw data) and a second phase, named post-processing,
ltering the raw data aggregated to a half hour time scale. For the post-
processing have proposed various methods of ltering. Since you can not
decide a priori which of the combinations of ltering is more correct, the dif-
ferences in results must be considered and interpreted as uncertainty. The
main objective of this thesis is to apply di erent patterns of post processing,
to quantify the uncertainty and attribute, at each step of post processing, a
weight than overall uncertainty. After the quanti cation of uncertainty the
attention was paid both to quantify the impact that di erent patterns of
post processing have on the annual carbon balance but also to de ne the
intrinsic uncertainty of the post processing factors that cause the most di-
sagreement. For an example of the impact that the uncertainty of the post
processing of the EC data has during the application phase the results of
di erent schemes have used to parameterize the light-response curve. The
choice of a di erent pattern of post-processing due to the di erences of the
nal results and have a considerable impact on the parameterization of the
light-response curve. The main factor of uncertainty is the threshold of u*
used to delete the data measured in periods of low turbulence. For the sites
analyzed years the average annual NEE (net exchange of CO2 between eco-
systems and atmosphere), respiration and GPP (gross primary production)
include, respectively, between -60 and -900, +800 and +1800 to +1000 and
+2000 gC m2. The di erences between the values and annual average
ows
for NEE are 50 gC m2 while for Reco and GPP are around 150 gC
m 2. These results demonstrate that the choice of a di erent pattern of
post-processing EC data has a signi cant impact on the uncertainty on the
global carbon balance.
Additional information
Dottorato di ricerca in Ecologia forestale
Subjects
File(s)![Thumbnail Image]()
Name
ctrotta_tesid.pdf
Size
1.3 MB
Format
Adobe PDF
Checksum (MD5)
1af94b25384ddb786cae592de859e7b1