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Cloud Climatologies from WACR-ARSCL at the Black Forest, Niamey and SGP Sites

Karen Johnson Brookhaven National Laboratory
Pavlos Kollias McGill University
Michael Jensen Brookhaven National Laboratory
Eugene Clothiaux The Pennsylvania State University

Category: Cloud Properties


Contours of WACR-ARSCL Best-estimate Reflectivity (dBZ) for Black Forest site on 2007.04.24, after non-hydrometeor returns have been eliminated. Black dots indicate lidar/ceilometer-determined cloud bases.

The ARM Program has continuously operated vertically pointing 95-GHz (3.2 mm) W-band ARM Cloud Radars (WACRs) at three locations: the fixed Southern Great Plains (SGP) site (ongoing since December 2005) and at the ARM Mobile Facility deployments to Niamey, Niger (2006), and Black Forest, Germany (2007), each for over 9 months. Data from the radars have been combined with that from each site's collocated micropulse lidar (MPL) and ceilometer to produce a value-added product known as WACR-ARSCL (WACR Active Remote Sensing of CLouds). The basic algorithm used in the WACR-ARSCL product is similar to that in the widely used ARSCL product, which is based on 35-GHz Millimeter Cloud Radar observations. An MPL-derived cloud mask is determined based on a comparison of lidar backscatter measurements to returns during known clear-sky periods. Next, a WACR cloud and precipitation mask is derived from signal-to-noise ratio thresholds determined for each time profile. The MPL cloud mask is combined with ceilometer cloud base estimates to produce a best-estimate cloud base for each time. The MPL and WACR cloud masks are merged, and then additional filtering of the resulting cloud mask is done in the lower troposphere (below approximately 3.5 km) to remove insect returns. Insects are identified using a combination of WACR linear depolarization ratios and reflectivity measurements. In this way, the remote sensing strengths of each instrument are synthesized to produce cloud boundaries and time-height profiles of reflectivity, mean Doppler velocity, Doppler spectral width, and linear depolarization ratio. Here we present WACR-ARSCL results and simple statistics of cloud occurrence for each of the three WACR deployments to date: Black Forest, Niamey, and SGP.

This poster will be displayed at ARM Science Team Meeting.