Process OMI and CMAQ NO2 columns

Produces apples-to-apples comparison between model and satellite columns

Process OMI VCD for model comparison after regridding

James East
2021-09-27

Needs to do:

• Get model data at right time step (nearest neighbor)
• Get model pressure levels
• interpolate SW to model, accounting for tropopause
• Compute model VCD (simple) and partial columns
  • $\Omega_V^M$[ppm] = $\frac{MW_{air}Av1e-4}{1e6} \sum_{surface}^{tp} \frac{\rho (z)}{\Delta H (z)}*C_{NO_2}(z)$
• Apply SW to model partial columns and sum for model SCD
  • $\Omega_S^M$ = $\sum_{surface}^{tp} \Omega_V^M(z)*w(z)$
• Compute model AMF (see Cooper et al. 2020 ACP)
  • $\text{AMF}M=M_G * \sum{surface}^{tp}w(z)\frac{n(z)}{\Omega_V^M}$
  • $M_G=\sec \theta_o + \sec \theta$
  • $\theta_o$ is solar zenith angle
  • $\theta$ is viewing zenith angle
  • see OMNO2G README p. 28 (https://aura.gesdisc.eosdis.nasa.gov/data/Aura_OMI_Level2/OMNO2.003/doc/README.OMNO2.pdf)
• Compute satellite VCD with CMAQ profile (see Duncan et al. 2014 Section S.5 and Palmer et al. 2001 eqs 13-15 and discussion)
  • $\Omega_V^{O'} = \frac{\Omega_V^O * \text{AMF}_{\text{OMI}}}{\text{AMF}_M}$
• Add OMI VCD with CMAQ profile to file
• Add CMAQ VCD & SCD to file
• Change dims to match IOAPI expectations for easier future comparison
• 1 retrieval at a time for now, loop later

Assumptions:

• Tropopause cutoff based on OMI tropopause definition
• All sat fields regridded to CMAQ grid first
• Surface pressure set to CMAQ for SW application
• Cloud filtering based on OMI cloud fraction
• Conservative horizontal regridding (requires nco >= 5.0.1)