- Related Research Areas
- Carbon Cycle & Ecosystems, Water & Energy Cycles
The Soil Moisture Active Passive (SMAP) mission is a NASA NRC Decadal Survey mission, with projected launch in the 2012 time frame that will provide global mapping of soil moisture and its freeze/thaw state. Primary science objectives for SMAP as directed by the National Research Council's Decadal Survey include reducing uncertainty regarding carbon uptake and release in boreal landscapes and the so-called missing carbon sink on land. We propose to conduct research that addresses these carbon cycle science objectives and prepares for future ecological applications of the SMAP mission. The net ecosystem exchange (NEE) of CO2 with the atmosphere is a fundamental measure of the balance between carbon uptake by vegetation gross primary production (GPP) and carbon losses through autotrophic (Ra) and heterotrophic respiration (Rh). We have developed a simple terrestrial carbon flux (TCF) model utilizing satellite remote sensing inputs from optical-IR and microwave sensors to quantify NEE and component carbon fluxes for northern ecosystems on a daily basis. The TCF algorithms and remote sensing inputs are robust and have been verified using biophysical measurements from global CO2 flux tower networks, detailed ecosystem process model simulations and relatively fine scale remote sensing. We will apply the TCF model framework with current satellite remote sensing time series from MODIS and AMSR-E on the NASA EOS Aqua platform to quantify spatial patterns and temporal behavior in NEE and component carbon fluxes, as well as soil moisture and temperature controls on these processes for all northern land areas over the recent (2002 onward) climate record. Daily AMSR-E brightness temperature measurements are used to derive surface (<10 cm depth) soil wetness and temperature conditions, and associated moisture and temperature controls on Rh. General land cover attributes and GPP inputs from MODIS (MOD12Q2 and MOD17A2) time series are used with Rh to compute Ra and NEE at daily to annual time scales. The TCF model framework produces regional measures of NEE and component carbon fluxes that are within the accuracy range of tower CO2 eddy covariance measurement approaches. A bi-product of TCF calculations also includes regional mapping of surface soil organic carbon stocks. However, the determination of terrestrial CO2 source-sink activity requires additional information on anthropogenic and disturbance related CO2 emissions. We will implement the TCF simulations within an atmospheric transport model assimilation framework to quantify regional terrestrial source-sink activity for atmospheric CO2. This assimilation framework will also be used to quantify accuracy and relative value of the remote sensing derived carbon fluxes in relation to global atmospheric CO2 monitoring networks, tower CO2 eddy covariance measurements, and alternative carbon flux estimates from ecosystem process model simulations. This project will provide the means for operational satellite-based assessment and monitoring of NEE, the primary measure of carbon exchange between the land and atmosphere. This project will also produce a valuable new tool for assessing regional patterns, temporal variability and environmental controls on northern terrestrial source-sink activity for atmospheric CO2. The results of this study will define future algorithms and accuracy requirements for SMAP that satisfy carbon cycle science objectives of the NRC Decadal Survey, and advance our understanding of the way in which northern ecosystems respond to climate anomalies and their capacity to reinforce or mitigate global warming.
Project PI: John Kimball/The University of Montana
Division of Biological Sciences College of Forestry and Conservation University of Montana Missoula, MT 59812
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