Evaluation of turbulent dissipation rate retrievals from Doppler Cloud Radar

[摘要] Turbulent dissipation rate retrievals from cloud radar Doppler velocitymeasurements are evaluated using independent, in situ observations in Arcticstratocumulus clouds. In situ validation data sets of dissipation rate arederived using sonic anemometer measurements from a tethered balloon and highfrequency pressure variation observations from a research aircraft, bothflown in proximity to stationary, ground-based radars. Modest biases arefound among the data sets in particularly low- or high-turbulence regimes,but in general the radar-retrieved values correspond well with the in situmeasurements. Root mean square differences are typically a factor of 4–6relative to any given magnitude of dissipation rate. These differences areno larger than those found when comparing dissipation rates computed fromtethered-balloon and meteorological tower-mounted sonic anemometermeasurements made at spatial distances of a few hundred meters. Temporal laganalyses suggest that approximately half of the observed differences are dueto spatial sampling considerations, such that the anticipated radar-basedretrieval uncertainty is on the order of a factor of 2–3. Moreover, radarretrievals are clearly able to capture the vertical dissipation ratestructure observed by the in situ sensors, while offering substantially moreinformation on the time variability of turbulence profiles. Together theseevaluations indicate that radar-based retrievals can, at a minimum, be usedto determine the vertical structure of turbulence in Arctic stratocumulusclouds.

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