Fig. 2
From: Direct retrieval of isoprene from satellite-based infrared measurements
Accounting for spectral interferences in the quantification of isoprene. a CrIS brightness temperature differences (ΔTb) for September 2014 (daytime, cloud-screened data only) mapped on a 2.0° × 2.5° latitude–longitude grid. ΔTb values are calculated as the spectral difference between the peak of absorption and proximate near-continuum data for the isoprene ν28 band. b Simulated ΔTb distribution predicted based on GEOS-Chem model isoprene columns for the same month. c Simulated brightness temperature differences at the peak of the ν28 isoprene absorption (ΔTν28) between an isoprene-free atmosphere and an atmosphere containing the GEOS-Chem isoprene distribution, based on an observing system simulation experiment. Panel c represents the spectral signal in the CrIS data arising purely from isoprene that would be expected given the GEOS-Chem isoprene distribution. d Difference between panels (b) and (c). Panel d represents the contributions from interfering species to ΔTb when calculated from the on-peak (ν28) vs. off-peak radiances as in panels (a) and (b). e Isoprene column densities (1016 molecule cm−2) predicted by GEOS-Chem for the same month and spatial grid
