| Abstract | dc.description.abstract | Stratocumulus cloud cover patterns and their relationship to drizzle were
characterized at San Felix Island (SFI: 26.5°S, 80°W) in the Southeast Pacific. Small
closed, large closed and open cells were identified in about 65% of the MODIS
(Moderate Resolution Imaging Spectro-radiometer) satellite images during 2003. The
MODIS imagery was combined with ceilometer and surface meteorological
measurements, human observations of cloud types and drizzle, and large-scale
meteorological analyses for January through June. We identified two drizzle regimes: a
synoptically-quiescent summer (Jan-March) regime characterized by a strong
anticyclone, large closed cells, and frequent drizzle, and an autumn (April-June) regime
characterized by a weaker anticyclone, small closed cells and open cells, and
precipitation that was mainly associated with synoptic activity. The large closed cells had
higher mean cloud bases and tops than the small closed cells, accounted for 45% of the
cumulus-under- stratocumulus reports, and 29% of the total drizzle and rain reports.
Large closed cells occupied more intermittently-coupled boundary layers than did the
small closed cells. Open cells also occurred in more decoupled conditions, but only
accounted for 18% of the total reports of drizzle and rain. The atmospheric stability of
large and small closed cells were similar, but large closed cells were more commonly
associated with a strong anticyclone, and small closed cells with wave activity
superimposed upon a weakened anticyclone. The increased drizzle and occurrence of
cumulus-under-stratocumulus in the summer rather than autumn is consistent with higher
nighttime liquid water paths. A contribution of this study is the documentation of the
ways in which synoptic activity can affect stratocumulus decks. | en_US |
