On the relationship between low cloud variability and lower tropospheric stability in the Southeast Pacific Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, CA, 90095, USA
05 Sep 2011
Received: 14 January 2011 – Published in Atmos. Chem. Phys. Discuss.: 02 February 2011 Abstract. In this study, we examine marine low cloud cover variability in the Southeast Pacific and its
association with lower-tropospheric stability (LTS) across a spectrum of timescales. On both daily
and interannual timescales, LTS and low cloud amount are very well correlated in austral summer (DJF).
Meanwhile in winter (JJA), when ambient LTS increases, the LTS–low cloud relationship substantially
weakens. The DJF LTS–low cloud relationship also weakens in years with unusually large ambient
LTS values. These are generally strong El Niño years, in which DJF LTS values are comparable
to those typically found in JJA. Thus the LTS–low cloud relationship is strongly modulated by
the seasonal cycle and the ENSO phenomenon. We also investigate the origin of LTS anomalies
closely associated with low cloud variability during austral summer. We find that the ocean
and atmosphere are independently involved in generating anomalies in LTS and hence
variability in the Southeast Pacific low cloud deck. This highlights the importance
of the physical (as opposed to chemical) component of the climate system in generating
internal variability in low cloud cover. It also illustrates the coupled nature of the
climate system in this region, and raises the possibility of cloud feedbacks related
to LTS. We conclude by addressing the implications of the LTS–low cloud relationship
in the Southeast Pacific for low cloud feedbacks in anthropogenic climate change.
Revised: 28 June 2011 – Accepted: 25 August 2011 – Published: 05 September 2011
Citation: Sun, F., Hall, A., and Qu, X.: On the relationship between low cloud variability and lower tropospheric stability in the Southeast Pacific, Atmos. Chem. Phys., 11, 9053-9065, doi:10.5194/acp-11-9053-2011, 2011.