In-situ vertical profiles of greenhouse gases: Why we need them and how we are going to get them in the future

For more than five years the NOAA/ESRL aircraft project has been collecting flask samples at as many as 20 sites throughout North America. A compilation of the data demonstrates that vertical profiles are valuable in many ways. In particular, we have demonstrated that it is possible to make continental-scale flux estimates that depend only on well known horizontal re-analysis winds. We also show how these datasets contribute to our understanding of large scale circulation and chemical processes that dominate the seasonal cycle of these gases. Finally, these datasets have been essential for validating satellite observations and GHG forward and inverse models. As the requirements grow for estimating fluxes at smaller scales, so will the need for a higher density of vertical profiles. The NOAA/ESRL aircraft project has taken a lead role in this with the development a new sampling technology called the AirCore, as well as the validation and testing of Wavelength-Scanned Cavity Ring Down Spectroscopy (WS-CRDS) technology that is suitable for deployment on commercial aircraft. With this technology we expect to increase the density of vertical profiles made each year by two orders of magnitude with only moderate increases in cost. The increase in vertical profile density will not only help us quantify terrestrial fluxes but also help to understand the key mechanisms driving the variability in fluxes.