Global patterns of solar influence on high cloud cover
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One of the main sources of uncertainty in climate projections is represented by clouds, which have a profound influence on the Earth’s radiation budget through the feedbacks in which they are involved. The improvement of clouds representation in General Circulation Models relies largely on constraints derived from observations and on correct identification of processes that influence cloud formation or lifetime. Here we identify solar forced high cloud cover (HCC) patterns in reanalysis and observed data extending over the 1871–2009 period, based on their associations with known fingerprints of the same forcing on surface air temperature, sea surface temperature (SST) and sea level pressure fields. The solar influence on HCC has maximum amplitudes over the Pacific basin, where HCC anomalies are distributed in bands of alternating polarities. The colocation of the HCC and SST anomalies bands indicates a thermal influence on high clouds through convection and an amplification of the HCC anomalies by a positive feedback of long-wave fluxes, which increases the solar signal. Consistent with numerical simulations, the solar forced HCC pattern appears to be generated through a constructive interference between the so-called “top-down” and “bottom-up” mechanisms of solar influence on climate and is amplified by ocean–atmosphere positive feedbacks.
KeywordsHigh clouds Solar forcing Pacific Ocean Convection
This work was supported by project PN-II-ID-PCE-2011-3-0709, SOLACE (IDEI 283) of the Romanian National Authority for Scientific Research, CNCS, UEFISCDI. ISCCP project is acknowledged for the cloud data. Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment program, and Office of Biological and Environmental Research, and by the National Oceanic and Atmospheric Administration Climate Program Office. We thank two anonymous reviewers for their constructive comments, which contributed to a significant improvement of the manuscript.
- Hou YT, Campana KA, Yang SK (2002) Parametrization of solar radiation transfer in the NCEP models. NCEP Office Note 441:33Google Scholar
- Randall DA, Wood RA et al (2007) Cilmate models and their evaluation. In: Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M, Miller HL (eds) Climate change, the physical science basis. Contribution of working group I to the fourth assessment report of the intergovernmental panel on climate change. Cambridge University Press, CambridgeGoogle Scholar
- Rayner NA, Parker DE, Horton EB, Folland CK, Alexander LV, Rodwell DP, Kent EC, Kaplan A (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J Geophys Res 108:2-1–2-22, doi: 10.1029/2002JD002670
- Rossow WB, Walker AW, Beuschel DE, Roiter MD (1996) International satellite cloud climatology project (ISCCP): documentation of new cloud datasets. WMO/TD-737, World Meteorol. Org., Geneva. p 115Google Scholar
- van Loon H, Meehl GA, Shea DJ (2007) Coupled air-sea response to solar forcing in the Pacific region during northern winter. J Geophys Res 112:1–8Google Scholar