Temporal scales of tropospheric CO2, precipitation, and ecosystem responses in the central Great Plains

Natural and anthropogenic sources of CO2 around the globe contribute to mid-tropospheric concentrations, yet it remains unknown how measurements of mid-tropospheric CO2 relate to regional ecosystem dynamics. NASA Atmospheric Infrared Sounder (AIRS) measurements of CO2 concentrations in the mid-troposphere from 2002 to 2010 were examined in relation to precipitation and vegetation phenology across the US Great Plains. Wavelet multi-resolution analysis and the information theory metric of relative entropy were applied to assess regional relationships between mid-tropospheric CO2, Normalized Difference Vegetation Index (NDVI), and precipitation (PPT). Results show that AIRS observations of mid-tropospheric CO2 exchange greater amounts of information with regional PPT and NDVI at seasonal, annual, and longer time scales compared to shorter time scales. PPT and NDVI contribute to mid-tropospheric CO2 at the 18-month time scale, while spatial patterns seen at this time scale for PPT and mid-tropospheric CO2 are reflective of the influence of PPT on NDVI at the annual scale. Identification of these dominant temporal scales may facilitate utilization of AIRS CO2 for monitoring regional source/sink dynamics related to climate and land-use/cover change.

► AIRS CO2 exchanges more information with PPT and NDVI at seasonal to longer scales.
► PPT and NDVI contribute to mid-tropospheric CO2 at the 18-month scale.
► CO2-NDVI 18-month correlations indicate coupling of surface and atmospheric column.
► Lack of CO2-NDVI correlations at shorter scales may be due to advective transport.
► AIRS CO2 can be used at identified temporal scales to assess climate forcings.