Abstract
Abstract. The U.S. Department of Energy (DOE) Atmospheric Radiation Measurements (ARM) facility has been at the forefront of millimeter-wavelength radar development and operations since the late 1990s. The operational performance of the ARM cloud radar network is very high; however, the calibration of the historical record is not well established. Here, a well-characterized spaceborne 94 GHz cloud profiling radar (CloudSat) is used to characterize the calibration of the ARM cloud radars. The calibration extends from 2007 to 2017 and includes both fixed and mobile deployments. Collectively, over 43 years of ARM profiling cloud radar observations are compared to CloudSat and the calibration offsets are reported as a function of time using a sliding window of 6 months. The study also provides the calibration offsets for each operating mode of the ARM cloud radars. Overall, significant calibration offsets are found that exceed the uncertainty of the technique (1–2 dB). The findings of this study are critical to past, ongoing, and planned studies of cloud and precipitation and should assist the DOE ARM to build a legacy decadal ground-based cloud radar dataset for global climate model validation.
Highlights
The first millimeter-wavelength cloud radars (MMCRs; Moran et al, 1998) of the U.S Department of Energy Atmospheric Radiation Measurement (ARM) facility were installed at the Tropical Western Pacific (TWP), Manus, and Southern Great Plains (SGP) sites in 1996
The OLI KAZR2 is compared against the CloudSat cloud profiling radar (CPR) for the period September 2015 to December 2017
If the calibration offset is positive, this suggests that the MD mode underestimates the radar reflectivity compared to CloudSat
Summary
The ARM facility has been at the forefront of short-wavelength radar development and operations for over 2 decades (Kollias et al, 2016). In 2005, the ARM facility started the deployment of its mobile facilities and the gradual modernization of the MMCR receiver. This led to the development of the W-band ARM Cloud Radar (WACR). The expansion included the addition of scanning millimeter- and centimeter-wavelength radars with Doppler and polarimetric capabilities (Kollias et al, 2014a; North et al, 2017) and the development of the next-generation profiling cloud radar, the Ka-band ARM Zenith Radar (KAZR) and its upgraded second generation (KAZR2)
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