Measurements of the C-H overtone transition strengths combined with estimates of the photodissociation cross sections for these transitions suggest that near-IR photodissociation of peroxy acetyl nitrate (PAN) is less significant (J(near-IR) approximate to 3 x 10(-8) s(-1) at noon) in the lower atmosphere than competing sinks resulting from unimolecular decomposition and ultraviolet photolysis. This is in contrast to the photochemical behavior of a related peroxy nitrate, pernitric acid (PNA), that undergoes rapid near-IR photolysis in the atmosphere with J(near-IR) approximate to 10(-5) s(-1) at noon (Roehl et al., 2002). This difference is attributed to the larger binding energy and larger number of vibrational degrees of freedom in PAN, which make 4 nu(CH) the lowest overtone excitation with a high photodissociation yield (as opposed to 2 nu(OH) in PNA).

We observe significant interannual variability in the strength of the seasonal cycle drawdown in northern midlatitudes from measurements of CO₂ made by the Total Carbon Column Observing Network (TCCON) and the Greenhouse Gases Observing Satellite (GOSAT). This variability correlates with surface temperature in the boreal regions. Using TCCON measurements, we find that the slope of the relationship between the X_CO2 seasonal cycle minima and boreal surface temperature is 1.2 ± 0.7 ppm K⁻¹. Assimilations from CarbonTracker 2011 and CO₂ simulations using the Simple Biosphere exchange Model (SiB) transported by GEOS-Chem underestimate this covariation. Both atmospheric transport and biospheric activity contribute to the observed covariation.