Global measurements of isoprene from the Cross-track Infrared Sounder

Isoprene is the dominant non-methane VOC emitted to the atmosphere and plays a critical role as a precursor of ozone and secondary aerosols, by coupling with the global nitrogen cycle, and by modulating the atmosphere's oxidizing capacity. Current bottom-up emission estimates span a wide range due to sparse in-situ observations in many parts of the world along with uncertainties in driving variables such as land cover and meteorology. Top-down constraints using space-based formaldehyde measurements suffer from uncertainties in isoprene chemistry across different NOx regimes, and from the fact that formaldehyde is also produced from fires and other VOCs. Here we present the first global measurements of isoprene using observations from the Cross-track Infrared Sounder (CrIS) and a neural network approach. We evaluate these measurements using aircraft observations and apply them in conjunction with the GEOS-Chem CTM to assess the new constraints they provide on isoprene and its impacts on atmospheric chemistry.