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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 13 | Copyright
Atmos. Chem. Phys., 18, 9723-9739, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 10 Jul 2018

Research article | 10 Jul 2018

An analysis of the cloud environment over the Ross Sea and Ross Ice Shelf using CloudSat/CALIPSO satellite observations: the importance of synoptic forcing

Ben Jolly1, Peter Kuma2, Adrian McDonald2, and Simon Parsons2 Ben Jolly et al.
  • 1Landcare Research, Lincoln, New Zealand
  • 2Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand

Abstract. We use the 2B-GEOPROF-LIDAR R04 (2BGL4) and R05 (2BGL5) products and the 2B-CLDCLASS-LIDAR R04 (2BCL4) product, all generated by combining CloudSat radar and CALIPSO lidar satellite measurements with auxiliary data, to examine the vertical distribution of cloud occurrence around the Ross Ice Shelf (RIS) and Ross Sea region. We find that the 2BGL4 product, used in previous studies in this region, displays a discontinuity at 8.2km which is not observable in the other products. This artefact appears to correspond to a change in the horizontal and vertical resolution of the CALIPSO dataset used above this level. We then use the 2BCL4 product to examine the vertical distribution of cloud occurrence, phase, and type over the RIS and Ross Sea. In particular we examine how synoptic conditions in the region, derived using a previously developed synoptic classification, impact the cloud environment and the contrasting response in the two regions. We observe large differences between the cloud occurrence as a function of altitude for synoptic regimes relative to those for seasonal variations. A stronger variation in the occurrence of clear skies and multi-layer cloud and in all cloud type occurrences over both the Ross Sea and RIS is associated more with synoptic type than seasonal composites. In addition, anomalies from the mean joint histogram of cloud top height against thickness display significant differences over the Ross Sea and RIS sectors as a function of synoptic regime, but are near identical over these two regions when a seasonal analysis is completed. However, the frequency of particular phases of cloud, notably mixed phase and water, is much more strongly modulated by seasonal than synoptic regime compositing, which suggests that temperature is still the most important control on cloud phase in the region.

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Short summary
Clouds in the Ross Sea and Ross Ice Shelf regions are examined using a combination of satellite observations from the CloudSat and CALIPSO satellite datasets. We show that previous studies may have included an artefact at high altitudes which under-estimated cloud occurrence. We also find that the meteorological regime is a stronger control of cloud occurrence, cloud type and cloud top than season over this region, though season is a strong control on the phase of cloud.
Clouds in the Ross Sea and Ross Ice Shelf regions are examined using a combination of satellite...