Radar Reflectivity–Based Estimates of Mixed Layer Depth

P. L. Heinselman Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma
NOAA/OAR/National Severe Storms Laboratory, Norman, Oklahoma

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P. L. Spencer Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma
NOAA/OAR/National Severe Storms Laboratory, Norman, Oklahoma

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K. L. Elmore Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma
NOAA/OAR/National Severe Storms Laboratory, Norman, Oklahoma

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D. J. Stensrud NOAA/OAR/National Severe Storms Laboratory, Norman, Oklahoma

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R. M. Hluchan School of Meteorology, University of Oklahoma, Norman, Oklahoma

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P. C. Burke NOAA/National Weather Service, Norman, Oklahoma

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Abstract

This study investigates the potential for estimating mixed layer depth by taking advantage of the radial gradients in the radar reflectivity field produced by the large vertical gradients in water vapor mixing ratio that are characteristic of the mixing height. During the day, this relationship often results in a ring of maximum reflectivity observed to progress radially outward from the radar as mixed layer depth increases. A comparison of mixed layer depths estimated from the Oklahoma City WSR-88D (KTLX) with those estimated from a nearby 915-MHz profiler reveals that mixed layer depths from the WSR-88D are slightly too high (up to 0.3 km) during the first three hours of the diurnal cycle, nearly unbiased midday, and slightly too low (0.2 km or less) thereafter. The procedure estimates mixed layer depths only during the daytime hours from 1300 to 2300 UTC. The weather conditions for the 17 days studied were fairly quiescent, with sunny skies and light winds.

@ Current affiliation: Weather Decision Technologies, Inc., Norman, Oklahoma

Corresponding author address: Pamela L. Heinselman, 120 David L. Boren Blvd., Suite 4900, Norman, OK 73072. Email: pam.heinselman@noaa.gov

Abstract

This study investigates the potential for estimating mixed layer depth by taking advantage of the radial gradients in the radar reflectivity field produced by the large vertical gradients in water vapor mixing ratio that are characteristic of the mixing height. During the day, this relationship often results in a ring of maximum reflectivity observed to progress radially outward from the radar as mixed layer depth increases. A comparison of mixed layer depths estimated from the Oklahoma City WSR-88D (KTLX) with those estimated from a nearby 915-MHz profiler reveals that mixed layer depths from the WSR-88D are slightly too high (up to 0.3 km) during the first three hours of the diurnal cycle, nearly unbiased midday, and slightly too low (0.2 km or less) thereafter. The procedure estimates mixed layer depths only during the daytime hours from 1300 to 2300 UTC. The weather conditions for the 17 days studied were fairly quiescent, with sunny skies and light winds.

@ Current affiliation: Weather Decision Technologies, Inc., Norman, Oklahoma

Corresponding author address: Pamela L. Heinselman, 120 David L. Boren Blvd., Suite 4900, Norman, OK 73072. Email: pam.heinselman@noaa.gov

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