The atmospheric radiation measurement program cloud profiling radars

An evaluation of signal processing and sampling strategies

Pavlos Kollias, Eugene E. Clothiaux, Bruce A. Albrecht, Mark Miller, Kenneth P. Moran, Karen L. Johnson

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

The U.S. Department of Energy (DOE) Atmospheric Radiation Measurements (ARM) program operates millimeter-wavelength cloud radars (MMCRs) in several specific locations within different climatological regimes. These vertically pointing cloud profiling radars supply the three most important Doppler spectrum moment estimates, which are the radar reflectivity (or zero moment), the mean Doppler velocity (or first moment), and the Doppler spectrum width (or second moment), as a function of time and height. The ARM MMCR Doppler moment estimates form the basis of a number of algorithms for retrieving cloud microphysical and radiative properties. The retrieval algorithms are highly sensitive to the quality and accuracy of the MMCR Doppler moment estimates. The significance of these sensitivities should not be underestimated, because the inherent physical variability of clouds, instrument-induced noise, and sampling strategy limitations all potentially introduce errors into the Doppler moment estimates. In this article, the accuracies of the first three Doppler moment estimates from the ARM MMCRs are evaluated for a set of typical cloud conditions from the three DOE ARM program sites. Results of the analysis suggest that significant errors in the Doppler moment estimates are possible in the current configurations of the ARM MMCRs. In particular, weakly reflecting clouds with low signal-to-noise ratios (SNRs), as well as turbulent clouds with nonzero updraft and downdraft velocities that are coupled with high SNR, are shown to produce degraded Doppler moment estimates in the current ARM MMCR operational mode processing strategies. Analysis of the Doppler moment estimates and MMCR receiver noise characteristics suggests that the introduction of a set of quality control criteria is necessary for identifying periods of degraded receiver performance that leads to larger uncertainties in the Doppler moment estimates. Moreover, the temporal sampling of the ARM MMCRs was found to be insufficient for representing the actual dynamical states in many types of clouds, especially boundary layer clouds. New digital signal processors (DSPs) are currently being developed for the ARM MMCRs. The findings presented in this study will be used in the design of a new set of operational strategies for the ARM MMCRs once they have been upgraded with the new DSPs.

Original languageEnglish (US)
Pages (from-to)930-948
Number of pages19
JournalJournal of Atmospheric and Oceanic Technology
Volume22
Issue number7
DOIs
StatePublished - Jul 1 2005
Externally publishedYes

Fingerprint

Atmospheric radiation
Signal sampling
signal processing
Signal processing
sampling
wavelength
Wavelength
evaluation
programme
radiation
Digital signal processors
signal-to-noise ratio
Signal to noise ratio
Sampling

All Science Journal Classification (ASJC) codes

  • Ocean Engineering
  • Atmospheric Science

Cite this

Kollias, Pavlos ; Clothiaux, Eugene E. ; Albrecht, Bruce A. ; Miller, Mark ; Moran, Kenneth P. ; Johnson, Karen L. / The atmospheric radiation measurement program cloud profiling radars : An evaluation of signal processing and sampling strategies. In: Journal of Atmospheric and Oceanic Technology. 2005 ; Vol. 22, No. 7. pp. 930-948.
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The atmospheric radiation measurement program cloud profiling radars : An evaluation of signal processing and sampling strategies. / Kollias, Pavlos; Clothiaux, Eugene E.; Albrecht, Bruce A.; Miller, Mark; Moran, Kenneth P.; Johnson, Karen L.

In: Journal of Atmospheric and Oceanic Technology, Vol. 22, No. 7, 01.07.2005, p. 930-948.

Research output: Contribution to journalArticle

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AU - Kollias, Pavlos

AU - Clothiaux, Eugene E.

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