[GTP] GTP Seminar January 21--John Finnigan

[Silvia Gentile]

NCAR
JOINT SEMINAR MMM/GTP
Limits to Accuracy and Optimal Instrument Deployment for Eddy Flux 
Measurement in Complex Terrain
John Finnigan
CSIRO Marine and Atmospheric Research


The influence of topography on the flow and turbulence remains a 
substantial challenge to interpreting micrometeorological observations 
of ecosystem-scale exchanges of energy, water and trace gases. 
Topographically induced perturbations to the flow and turbulence can 
lead to large localized perturbations in the observed vertical eddy 
fluxes and/or divergence in the horizontal advective fluxes which, even 
with substantial instrumentation, may not easily be diagnosed or corrected.
For simple scalar source distributions, analytic and numerical flow and 
transport models can be combined to provide information on the spatial 
pattern of the scalar concentration and flux fields in complex terrain 
and hence guide the positioning of towers and instrumentation. However, 
information about the ‘inverse’ problem is of more use to 
experimentalists. That is, what information about the scalar sources, 
such as magnitude and uncertainties, can we obtain from observations of 
fluxes and concentrations at a limited number of locations in complex 
terrain? Here we show that by inverting the flow models we can obtain 
information on the underlying limits of accuracy we can expect for 
observations of ecosystem exchange for a given set of instrument 
locations, instrumental accuracy and uncertainties in the models. We 
will also consider what are the optimal locations of instruments to 
reduce the uncertainty in ecosystem exchange estimates and, for a range 
of hill shapes, whether sufficiently accurate estimates of ecosystem 
exchange can be obtained using only one tower.


Thursday, 21 January 2010, 3:30 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg 2 Auditorium, Room 1022