Comment on egusphere-2026-2656

Abstract

Abstract. Temporal autocorrelations of aerosol are often reported, but poorly understood. We use simple box models, Perturbed Parameters Ensembles of global aerosol models, AEROCOM (AEROsol Comparison of Observations and Models) simulations as well as satellite and AERONET (AErosol RObotic NETwork) observations to study temporal autocorrelations in aerosol optical depth (AOD). In particular, we present the first global climatology of observed temporal autocorrelations. We develop a conceptual model for autocorrelations and relate them to important timescales, in particular lifetimes. We identify aerosol processes that affect autocorrelations and find autocorrelations provide information independent from yearly AOD, in particular on deposition processes. It is possible to estimate temporal autocorrelations in AOD from satellite observations by sensors like MODIS (MODerate resolution Imaging Spectroradiometer) or POLDER (POLarization and Directionality of the Earth’s Reflectances). In our unique global climatology of observed temporal autocorrelations, regional variation is significant. Over remote oceans, the autocorrelation after 6 days tends to be low (∼ 0.2 or lower) but it is quite high in tropical outflow regions (∼ 0.5). Over land, it varies considerably, from 0.2 to 0.7. These spatial variations are much larger than observed year-to-year variation. AEROCOM models often significantly overestimate autocorrelations. This suggests that loss processes are underestimated and/or contributions from seasonal sources are overestimated, which should have a marked impact on aerosol forcing estimates. Autocorrelations offer a new way to understand aerosol processes and evaluate models. Autocorrelations can be derived from existing observational datasets, for example surface black carbon mass concentrations or cloud condensation nuclei.

Authors 11

1. Nick Schutgens corresponding

   Vrije Universiteit Amsterdam

   Affiliation as printed

   Vrije Universiteit, 1081 HV Amsterdam, the Netherlands

2. Elisabeth J. Andrews

   National Oceanic and Atmospheric Administration · Cooperative Institute for Research in Environmental Sciences · University of Colorado Boulder · University of Colorado System · NOAA Global Monitoring Laboratory

   Affiliation as printed

   CIRES, University of Colorado, Boulder CO 80309, USA

   NOAA/Global Monitoring Laboratory, Boulder CO 80305, USA

3. Antti Arola

   Finnish Meteorological Institute

   Affiliation as printed

   FMI, P.O. Box 1627, FI-70211 Kuopio, Finland

4. Yusuf Bhatti Aachen SRON Space Research Organisation Netherlands

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Space Research Organisation Netherlands, 2333 CA Leiden, the Netherlands

5. Guanliang Fu Aachen SRON Space Research Organisation Netherlands

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Space Research Organisation Netherlands, 2333 CA Leiden, the Netherlands

6. Otto Hasekamp Aachen SRON Space Research Organisation Netherlands

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Space Research Organisation Netherlands, 2333 CA Leiden, the Netherlands

7. Pekka Kolmonen

   Finnish Meteorological Institute

   Affiliation as printed

   FMI, P.O. Box 1627, FI-70211 Kuopio, Finland

8. Antti Lipponen

   Finnish Meteorological Institute

   Affiliation as printed

   FMI, P.O. Box 1627, FI-70211 Kuopio, Finland

9. Tero Mielonen

   Finnish Meteorological Institute

   Affiliation as printed

   FMI, P.O. Box 1627, FI-70211 Kuopio, Finland

10. Leighton A. Regayre

    Met Office · University of Leeds

    Affiliation as printed

    Centre for Environmental Modelling and Computation, University of Leeds, Leeds, UK

    Met Office Hadley Centre, Exeter, UK

    School of Earth and Environment, University of Leeds, University of Leeds, Leeds, UK

11. Andrew M. Sayer

    University of Maryland, Baltimore · Goddard Space Flight Center

    Affiliation as printed

    Goddard Earth Sciences Technology And Research (GESTAR) II, University of Maryland, Baltimore, MD, USA

    NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA