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Browse and Order ARM AMF Niamey Cloud Data
Observations from the 95 GHz W-band ARM Cloud Radar (WACR), Micropulse Lidar (MPL), and ceilometer have been combined using the new WACR Active Remote Sensing of Clouds (WACR-ARSCL) VAP (Kollias and Miller, 2007) to produce cloud boundaries and time-height profiles of cloud location, radar moments, and linear depolarization ratio (LDR) fields. The data are available as an ARM evaluation product for the entire Niamey WACR deployment, 3/16/2006-12/29/2006. The temporal resolution is 5 seconds. The vertical resolution is equal to that of the WACR, 42.856 m.
The basic algorithm used in the WACR-ARSCL VAP is similar to that employed by the ARSCL VAP, which is based on 35-GHz Millimeter Cloud Radar observations (Clothiaux et al., 2000). First, an MPL-based cloud mask is determined based on the 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, 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 LDR and reflectivity measurements.
The WACR-ARSCL VAP produces two data streams, each having one file per day. The file below was derived from the WACR-ARSCL data products. It contains hourly cloud occurrence frequency for the entire Niamey deployment in a single file.
(File size: 11.3 MB)
Clothiaux, E. E., T. P. Ackerman, G. G. Mace, K. P. Moran, R. T. Marchand. M. A. Miller, B. E. Martner, 2000: Objective determination of cloud heights and radar reflectivities using a combination of active remote sensors at the ARM CART sites. J. Appl. Meteor., 39, 645-665.
Kollias, P. and M. A. Miller, Cloud and precipitation observations at Niamey during the 2006 ARM Mobile Facility deployment. Submitted to Geophys. Res. Lett.