Revisiting Aerosol–Cloud Interactions From Weekly Cycles

Geophysical Research Letters, vol. 51

Abstract

Abstract Weekly cycles (WCs) in cloud properties have been reported and linked to aerosol effects. Yet the extent to which human activities contribute to their occurrence remains unclear. Here, we revisit aerosol–cloud interactions from the WCs over central Europe using long‐term satellite and reanalysis data. Significant WCs in aerosol and cloud droplet number concentration ( N d ) are detected with minima/maxima on Monday/Friday, indicating a clear signal of the Twomey effect. Notably, N d –to–aerosol sensitivity from WCs is found to decrease at larger aerosol concentrations, confirming the nonlinear behavior of the aerosol– N d relation (in log–log space) reported previously, but from a distinct perspective. Nevertheless, no discernible WCs in liquid water path are found. The pronounced WCs in cloud cover are demonstrated to be driven by natural variability. Our results indicate that the WCs offer a useful pathway for investigating the Twomey effect, but are not as effective for detecting cloud adjustments.

Authors 3

1. Hailing Jia corresponding Aachen SRON Netherlands Institute for Space Research Leiden The Netherlands SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Netherlands Institute for Space Research Leiden The Netherlands

   SRON Netherlands Institute for Space Research, Leiden, The Netherlands

2. Otto Hasekamp Aachen SRON Netherlands Institute for Space Research Leiden The Netherlands SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Netherlands Institute for Space Research Leiden The Netherlands

   SRON Netherlands Institute for Space Research, Leiden, The Netherlands

3. Johannes Quaas

   Leipzig University

   Affiliation as printed

   Leipzig Institute for Meteorology Leipzig University Leipzig Germany

   Leipzig Institute for Meteorology, Leipzig University, Leipzig, Germany