Evaluation of gridded scanning ARM cloud radar reflectivity observations and vertical doppler velocity retrievals

Abstract

Abstract. The scanning Atmospheric Radiation Measurement (ARM) cloud radars (SACRs) provide continuous atmospheric observations aspiring to capture the 3-D cloudscale structure. Sampling clouds in 3-D is challenging due to their temporal-spatial scales, the need to sample the sky at high elevations and cloud radar limitations. Thus, a suggested scan strategy is to repetitively slice the atmosphere from horizon to horizon as clouds advect over the radar (Cross-Wind Range-Height Indicator -CW-RHI). Here, the processing and gridding of the SACR CW-RHI scans are presented. First, the SACR sample observations from the ARM Southern Great Plains and Cape Cod sites are post-processed (detection mask, gaseous attenuation correction, insect filtering and velocity de-aliasing). The resulting radial Doppler moment fields are then mapped to Cartesian coordinates with time as one of the dimensions. Next the Cartesian-gridded Doppler velocity fields are decomposed into the horizontal wind velocity contribution and the vertical Doppler velocity component. For validation purposes, all gridded and retrieved fields are compared to collocated zenith-pointing ARM cloud radar measurements. We consider that the SACR sensitivity loss with range, the cloud type observed and the research purpose should be considered in determining the gridded domain size. Our results also demonstrate that the gridded SACR observations resolve the main features of low and high stratiform clouds. It is established that the CW-RHI observations complemented with processing techniques could lead to robust 3-D cloud dynamical representations up to 25-30 degrees off zenith. The proposed gridded products are expected to advance our understanding of 3-D cloud morphology, dynamics and anisotropy and lead to more realistic 3-D radiative transfer calculations.

Developing and Evaluating Ice Cloud Parameterizations for Forward Modeling of Radar Moments Using in situ Aircraft Observations

“…The presence of more modern cloud radars such as the K a -band ARM zenith radar (KAZR; Lamer et al 2014) or the MIRA-35 cloud radar (Melchionna et al 2008), which are available at numerous ground-based sites today, can also lead to better possibilities for the exploration of higher moments and the Doppler spectrum because of their better sensitivity and larger spectral resolution. The question of why deviations from the A(D) power law for particles greater 1 mm are essential to obtain consistent results for the higher moments has to be investigated in greater detail in the future.…”

The Two‐Column Aerosol Project: Phase I—Overview and impact of elevated aerosol layers on aerosol optical depth

“…The second example is the same case as presented by Lamer et al . [] and shows a vertical cut of the gridded 3‐D field for a deck of stratocumulus clouds with a vertical extent of less than 500 m that were observed on 19 November 2012 (Figure , bottom). The relatively low observed reflectivity in this stratocumulus cloud layer challenged the SACR's detectability threshold resulting in an apparent gradual reduction of the observed cloud thickness with range.…”

“…The relatively low observed reflectivity in this stratocumulus cloud layer challenged the SACR's detectability threshold resulting in an apparent gradual reduction of the observed cloud thickness with range. Despite this limitation [ Lamer et al ., ], the gridded SACR observations can provide valuable information about cloud structure needed for evaluating both high‐resolution simulations and for testing cloud parameterizations.…”

Observations of fair-weather cumuli over land: Dynamical factors controlling cloud size and cover

“…A histogram of the maximum cloud top reflectivity of the 882 cumuli observed by the KAZR reveals that any radar with a sensitivity below −43 dB Z at 2 km would miss to observe another 50% of the nonprecipitating cumulus field at the SGP (Figure b). This adds considerable challenges for off‐zenith (three‐dimensional) cloud observations using scanning cloud radars [ Lamer et al , ; Kollias et al , ].…”