Radar Refractivity: validation and application to forecasting Crystalyne R. Pettet, Tammy M. Weckwerth, and James W. Wilson—NCAR/ATD Frédéric Fabry and ShinJu Park—McGill University

Validation

Sfc comparisons S-Pol N varies most strongly with moisture

High correlation between S-Pol N and station N Sfc comparisons High correlation between S-Pol N and station N

S-Pol N compares favorably with areas of relatively constant mobile N Mobile mesonets S-Pol N compares favorably with areas of relatively constant mobile N

S-Pol N gradients are smoothed Mobile mesonets S-Pol N gradients are smoothed

UWKA S-Pol N gradient smoothed over ~10 km S-Pol N compares favorably with areas of relatively constant UWKA N

AERI—Atmospheric Emitted Radiance Interferometer

AERI Transition between 220-355 m from high to low r values

P-3 If CBL is well-mixed, N represents at least half the depth of the CBL.

AERI—diurnal and height differences N bias is strongest at night and improves with mixing of CBL Strongest relationship occurs at low levels

AERI—diurnal and height differences Low levels—strong relationship from one hour after sunrise until 2 hours after sunset Increasing height—strong relationship begins later in the morning and drops off by 2200 UTC

Soundings Similar results to AERI—lowest 200-250 m

SRL Strong correspondence between SRL mixing ratio magnitude, surface station mixing ratio, and S-Pol N

Forecasting Utility

Boundary development

CI—10 June 2002

CI— 10 June 2002

CI—12-13 June 2002

CI— 12-13 June 2002

Summary Radar refractivity shows excellent correlation with refractivity calculated from other datasets Vertical depth represented by radar refractivity is typically below 200-250 m AGL, but may be dependent upon the extent of vertical mixing Horizontal scale of refractivity varies, and appears to be as high as 2 km at times and lower than 4 km at other times

Summary Radar refractivity shows great promise as a potential nowcasting and forecasting tool

For more information… Contact me at pettet@ucar.edu to get a pdf of the manuscript that has been submitted to JAM that this talk is based on.