Temporal Scales of Tropospheric CO2, Precipitation, and Ecosystem Responses in the Central U.S.

Abstract

Concentrations of CO2 in the mid-troposphere retrieved by NASA's Atmospheric Infrared Sounder (AIRS) were examined in relation to surface carbon dynamics, vegetation phenology, and precipitation (PPT) in the central US. Wavelet multi-resolution analysis was applied and the information theory metric of relative entropy computed for comparisons of eddy covariance tower CO2 measurements at three sites in Northeastern Kansas with different land cover types. Sites experiencing woody encroachment agreed with AIRS mid-tropospheric CO2 on a four-day time scale, while the tallgrass prairie site showed agreement at one month. Local, surface CO2 measurements and regional PPT and normalized difference vegetation index (NDVI) values show greatest correlations with AIRS mid-tropospheric CO2 at the 18-month scale. AIRS observations agree with regional PPT and NDVI at seasonal and interannual scales suggesting that AIRS CO2 measurements can be used to assess regional source-sink dynamics related to climate forcings.