Spelling suggestions: "subject:"agradient independent method"" "subject:"9gradient independent method""
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Gas flux estimation from surface gas concentrationsShahnaz, Sabina 27 May 2016 (has links)
A gradient-independent model of gas fluxes was formulated and tested. The
model is built on the relationship between gas flux and the time history of surface gas
concentration, known as half-order derivative (HOD), when the transport of the gas in the
boundary layer is described by a diffusion equation. The eddy-diffusivity of gas is
parameterized based on the similarity theory of boundary layer turbulence combined with
the MEP model of surface heat fluxes. Test of the new model using in-situ data of CO2
concentration and fluxes at several locations with diverse vegetation cover, geographic
and climatic conditions confirms its usefulness and potential for monitoring and
modeling greenhouse gases. The proposed model may also be used for estimating other
GHGS fluxes such as methane (CH4) and Water vapor flux. This proof-of-concept study
justifies the proposed model as a practical solution for monitoring and modeling global
GHGS budget over remote areas and oceans where ground observations of GHGS fluxes
are limited or non-existent. One focus of the on-going research is to investigate its
application to producing regional and global distributions of carbon fluxes for identifying
sinks and sources of carbon and re-evaluating the regional and global carbon budget at
monthly and annual time scales.
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Gas flux estimation from surface gas concentrationsShahnaz, Sabina 27 May 2016 (has links)
The goal of this study is to develop a gradient-independent method for modeling surface gas flux using surface gas concentration data. The proposed method is built on the relationship between gas flux and the time history of surface gas concentration, known as half-order derivative (HOD), when the transport of gas in the boundary layer is described by a diffusion equation. The new model is tested using in-situ data of CO2 concentration time series at half hour (or hour) intervals from Ameriflux Network at several locations in US, Canada, Mexico and Brazil to estimate CO2 fluxes. In this research the estimated CO2 flux using HOD method are compared with observed CO2 fluxes from four study sites out of 160+ sites with diverse vegetation cover, geographic and climatic conditions to test the generality of model within reasonable endeavor. The sites are Cedar Bridge National Forest, New Jersey, Delta Junction 1920 Control, Alaska, Lucky Hills Shrub land, Arizona, and LBA Tapajos Mature Forest, Brazil. The modeled CO2 flux demonstrates close agreement with field observations confirming the usefulness and potential of HOD model for estimating CO2 gas fluxes.
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