Investigating the Synoptic Component in Atmospheric CO2 Variability Using An Atmospheric Transport Model
Nick
Parazoo, Atmospheric Science, Colorado State University, nparazoo@atmos.colostate.edu
Scott
Denning, Atmospheric Science, Colorado State University, denning@atmos.colostate.edu
(Presenting)
Ravi
Lokupitiya, Atmospheric Science, Colorado State University, ravi@atmos.colostate.edu
Ian
Baker, Atmospheric Science, Colorado State University, baker@atmos.colostate.edu
Zhengxin
Zhu, NASA GSFC, zhu@code916.gsfc.nasa.gov
Randall
Kawa, NASA GSFC, kawa@maia.gsfc.nasa.gov
A popular method for estimating the global distribution of terrestrial CO2 sources and sinks is to invert atmospheric CO2 measurements through the use of atmospheric transport models. In the past this approach has utilized monthly mean CO2 measurements in remote marine boundary layer environments. The global network of monitoring stations is growing, however, and continuous measurements are becoming more high frequency and continental. Inversions of continental data will help to improve the inversion results but taking advantage of the measurements requires an understanding of the processes driving the high-frequency variability.
This study focuses on synoptic scale variability, which is often regarded as noise. To simulate the transport of CO2 in the atmosphere, we use a global Parameterized Chemical Transport Model (PCTM) driven by surface CO2 fluxes and GEOS4 reanalysis. The results are compared to a network of well-calibrated continuous CO2 mixing ratio measurements in North America. Our results show that PCTM does a reasonable job capturing the various scales of variability at the measurement sites. The seasonal cycle is well represented by the model with some wintertime overestimation in the higher latitude sites. The diurnal cycle suffers from weak nocturnal buildup, especially in the higher latitude sites. Synoptic variability is captured surprisingly well throughout the year at all the stations. This study focuses on the roles of horizontal advection, vertical advection, and ecosystem response to synoptic weather in explaining CO2 signals during frontal passage events.