Formaldehyde - Tropospheric Column

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The graph below shows time series of the monthly mean difference between TROPOMI and NDACC FTIR (FTIR smoothed following procedure of Rodgers and Connor (2003)) at individual sites and for all sites combined, as well as a regression model fitting a trend (or drift) and a seasonal cycle. The second figure shows the drifts obtained per station, and obtained over all stations (© Update March, 2026 of Vigouroux et al., AMT 2020).

relative bias vs mean FTIR per station Drift HCHO
Top panel: all monthly means differences at individual sites and in black squares with error bars are shown the means of the differences (between TROPOMI and smoothed FTIR) at all sites for each month. The red curve is the regression model which includes a trend and a seasonal cycle. Bottom panel: drifts (trends in the absolute differences between the monthly means of TROPOMI and FTIR data. The smaller markers are for direct comparisons (no smoothing) and the larger ones are with smoothing (Rodgers and Connor 2003). The drift when all stations are considered simultaneously is added (92 latitude).