Global representation of aerosol vertical profiles by sums of lognormal modes: Consequences for the passive remote sensing of aerosol heights

Abstract

Aerosol extinction profiles from a climatology of CALIPSO measurements are analyzed with respect to their representation by truncated sums of up to three lognormal functions. Discussed are results for the climatological mean and a realistic profile, which is constructed from the climatological mean and its standard deviation. The realistic profile shows, in general, a more feature‐rich structure and is used as proxy for actual measurements. It was found that a single lognormal mode is on global scale able to explain 59% of the vertical profile, while a sum of two modes is able to explain 74%. Including a third lognormal mode leads only to a minor improvement to 79%. The strong regional and weaker seasonal dependency of the reconstruction accuracy with respect to the number of used lognormal modes is presented and discussed in detail. These findings have implications for the design of future operational aerosol height retrievals for upcoming instruments such as Tropospheric Monitoring Instrument on board European Space Agency's Sentinel 5 precursor or Sentinel 4.

Evaluation of the operational Aerosol Layer Height retrieval algorithm for Sentinel-5 Precursor: application to O<sub>2</sub> A band observations from GOME-2A

“…2 indicate that the retrieved height parameter (here the height of a scattering layer with constant particle extinction coefficient) is quite robust against model errors in the assumed aerosol type. This finding agrees with Hollstein and Fischer (2014), who show in a similar simulation study that the retrieved center height of a lognormal aerosol profile is also quite stable with respect to aerosol type. The simulations of Sect.…”

“…The observation that residues increase and retrieved layer pressure decreases when boundary layer aerosols are added to the scene suggests that some information about boundary layer aerosols is contained in the spectrum. Alternatively, profile parameterisations using empirically determined orthogonal functions (e.g., Hollstein and Filipitsch, 2014) could also be worth investigating in this respect. In view of the limited information content, we strongly doubt however whether A. F. J. Sanders et al: Evaluation of the Aerosol Layer Height retrieval algorithm for Sentinel-5 Precursor adding many more profile parameters to the state vector will improve the retrieval.…”

“…Various instrument requirement and sensitivity studies investigating the potential of spectral measurements of the O 2 A band for aerosol retrieval have appeared in the past. These studies include the ones by Geddes and Bösch (2015), Hollstein and Fischer (2014), Sanders and De Haan (2013), Hollstein et al (2012), Hasekamp and Sidans (2009), Siddans et al (2007), Corradini and Cervino (2006), and Gabella et al (1999). Overall, these studies show, among other things, that retrieval precision is typically better when the aerosols are optically thicker or more elevated, or when the solar zenith angle is larger.…”

Evaluation of the operational Aerosol Layer Height retrieval algorithm for Sentinel-5 Precursor: application to O<sub>2</sub> A band observations from GOME-2A

“…The observation that residues increase and retrieved layer pressure decreases when boundary layer aerosols are added to the scene suggests that some information about boundary layer aerosols is contained in the spectrum. Alternatively, profile parameterisations using empirically determined orthogonal functions (e.g., Hollstein and Filipitsch, 2014) could also be worth investigating in this respect. In view of the limited information content, we strongly doubt however whether adding many more profile parameters to the state vector will improve the retrieval.…”

Potential Approach for Single-Peak Extinction Fitting of Aerosol Profiles Based on In Situ Measurements for the Improvement of Surface PM2.5 Retrieval from Satellite AOD Product

“…Log-normal distribution has most often been used to predict aerosol size distributions in previous studies [48][49][50][51]. As a result of its high similarity to the single-peak aerosol extinction profile, log-normal modes have also been used to represent the vertical distribution of aerosols in the literature [52,53].…”