The Atmospheric Radiation Measurement Program Cloud Radars: Operational Modes

Abstract

During the past decade, the U.S. Department of Energy (DOE), through the Atmospheric Radiation Measurement (ARM) Program, has supported the development of several millimeter-wavelength radars for the study of clouds. This effort has culminated in the development and construction of a 35-GHz radar system by the Environmental Technology Laboratory (ETL) of the National Oceanic and Atmospheric Administration (NOAA). Radar systems based on the NOAA ETL design are now operating at the DOE ARM Southern Great Plains central facility in central Oklahoma and the DOE ARM North Slope of Alaska site near Barrow, Alaska. Operational systems are expected to come online within the next year at the DOE ARM tropical western Pacific sites located at Manus, Papua New Guinea, and Nauru. In order for these radars to detect the full range of atmospheric hydrometeors, specific modes of operation must be implemented on them that are tuned to accurately detect the reflectivities of specific types of hydrometeors. The set of four operational modes that are currently in use on these radars are presented and discussed. The characteristics of the data produced by these modes of operation are also presented in order to illustrate the nature of the cloud products that are, and will be, derived from them on a continuous basis.

Cloud base vertical velocity statistics: a comparison between an atmospheric mesoscale model and remote sensing observations

“…We analyse observations from two sites with zenith-pointing millimeter-wavelength Doppler cloud radars; the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in central Oklahoma, US (Clothiaux et al, 1999), and the Deutscher Wetterdienst (DWD) observatory in Lindenberg, Germany. Both sites are also equipped with co-located lidars, ceilometers, and complemented by a suite of surface instruments.…”

“…The Doppler cloud radar at SGP is the 35 GHz millimeterwavelength cloud radar, MMCR (Clothiaux et al, 1999), which has a number of operational modes; we therefore use the Active Remote Sensing of Clouds (ARSCL) dataset (Clothiaux et al, 2000(Clothiaux et al, , 2001 as input to the Cloudnet processing scheme. The ensuing vertical resolution is approximately 90 m. The Doppler cloud radar at Lindenberg is the 35.5 GHz MIRA and the vertical resolution of the Cloudnet product is approximately 30 m. The intrinsic error in the mean Doppler velocity is smaller than the bin width of the measured Doppler spectrum and, hence, for both Doppler cloud radars, the Doppler velocity resolution is on the order of 2 cm s −1 .…”

A Bayesian algorithm for the retrieval of liquid water cloud properties from microwave radiometer and millimeter radar data

“…It cycles through four different operational modes, each with different sensitivity, spatial and temporal resolution, and aliasing characteristics. Details of the operational parameters of the MMCR at each ARM site are given by Clothiaux et al [1999]. The Active Remote Sensing of Clouds (ARSCL) product described by Clothiaux et al [2000] combines information from all modes of the MMCR with MPL and CEIL data to produce a best estimate of cloud boundaries, hydrometeor reflectivities and vertical velocities at 10 s temporal and 45 m vertical resolution.…”

“…It depends on the mode used and the distance of the hydrometeors from the antenna. For each mode, we estimate the sensitivity at each range gate based on the parameters of the operational modes at Nauru given by Clothiaux et al [1999]. If radar reflectivity is expressed in units of mm 6 /m 3 , then the calibration error is multiplicative while the receiver noise error is additive.…”

“…Advances in instrumentation within the last 5 years have led to the development of unattended millimeter wavelength cloud radars with the vertical resolution ($45 m) and sensitivity (À60 dBZ) required to study boundary layer clouds [Moran et al, 1998;Clothiaux et al, 1999]. Several algorithms have been developed that seek to relate measured radar reflectivity to liquid water content.…”