The response of clouds and aerosols to cosmic ray decreases

Abstract

A method is developed to rank Forbush decreases (FDs) in the galactic cosmic ray radiation according to their expected impact on the ionization of the lower atmosphere. Then a Monte Carlo bootstrap‐based statistical test is formulated to estimate the significance of the apparent response in physical and microphysical cloud parameters to FDs. The test is subsequently applied to one ground‐based and three satellite‐based data sets. Responses (>95%) to FDs are found in the following parameters of the analyzed data sets. AERONET: Ångström exponent (cloud condensation nuclei changes), SSM/I: liquid water content, International Satellite Cloud Climate Project (ISCCP): total, high, and middle, IR‐detected clouds over the oceans, Moderate Resolution Imaging Spectroradiometer (MODIS): cloud effective emissivity, cloud optical thickness, liquid water, cloud fraction, liquid water path, and liquid cloud effective radius. Moreover, the responses in MODIS are found to correlate positively with the strength of the FDs, and the signs and magnitudes of the responses agree with model‐based expectations. The effect is mainly seen in liquid clouds. An impact through changes in UV‐driven photo chemistry is shown to be negligible and an impact via UV absorption in the stratosphere is found to have no effect on clouds. The total solar irradiance has a relative decrease in connection with FDs of the order of 10−3, which is too small to have a thermodynamic impact on timescales of a few days. The results demonstrate that there is a real influence of FDs on clouds probably through ions.

New Insights on the Physical Nature of the Atmospheric Greenhouse Effect Deduced from an Empirical Planetary Temperature Model

“…The hereto proposed passive nature of planetary albedos does not imply that the global cloud cover could not be influenced by an external forcing such as solar wind, galactic cosmic rays, and/or gravitational fields of other celestial objects. Empirical evidence strongly suggests that it can [108][109][110][111][112][113], but the magnitude of such influences is expected to be small compared to the total albedo due to the presence of stabilizing negative feedbacks within the system. We also anticipate that the sensitivity of GMATs to an albedo change will greatly vary among planetary bodies.…”

Solar 27-day rotational period detected in wide-area lightning activity in Japan

“…This mechanism is under debate, but several possible pathways have been suggested, including total solar irradiance (TSI; Foukal, 2004Foukal, , 2006, ultraviolet (UV; Hood, 1986;Shindell, 1999;Kodera and Kuroda, 2002), and galactic cosmic rays (GCRs; Svensmark and Friis-Christensen, 1997;Marsh and Svensmark, 2000;Svensmark et al, 2016).…”

Solar rotational cycle in lightning activity in Japan during the 18–19th centuries

“…The mechanisms for a solar influence on the climate and weather are not certain; however, possible explanations are given based on the forcing of solar radiation (Foukal, 2004(Foukal, , 2006Hood, 1986;Shindell, 1999;Kodera and Kuroda, 2002;Zhou and Tung, 2013), galactic cosmic rays (Svensmark and Friis-Christensen, 1997;Marsh and Svensmark, 2000;Yamaguchi et al, 2010;Svensmark et al, 2016), solar energetic particles (Jackman et al, 2009;Scott et al, 2014), and from the changes in the atmospheric electric circuit (Tinsley, 1996;Owens et al, 2015). The variations of solar-related parameters associated with solar rotations are quasi-periodic.…”