Several intercomparisons of data from the WCR and the Ka-band radar of NOAA/ETL Radar Meteorology and Oceonograohy Division (Dr. R. Kropfli, Chief) are available from a research flight conducted in a nimbostratus situation. The flight took place during the 1995 coastal meteorology study in Oregon. At upper levels, the cloud consisted entirely of ice crystals; below the melting level (near 2400 m) light rain was falling. WCR was operated in the uplooking mode while the KingAir was making traverses over the NOAA radar site. The NOAA radar was executing RHI scans roughly in the plane of the aircraft flight. Brooks Martner of NOAA/ETL operated the NOAA/Ka radar during this study, and kindly provided the data for these intercomparisons.

As additional reference for the intercomparison of the two radars, we include some calculated reflectivity values as well. These are based on dropsize distributions from PMS-1D and PMS-2D probes, and with the 95 GHz reflectivity calculated using Mie scattering functions.

The conclusions that we draw from these data are:

• 1. For drizzle, reflectivities from the two radars are in agreement within about 2 dBZ.
• 2. For the ice cloud, reflectivities are mostly within 3-4 dBZ, but in some cases the difference reached 10 dBZ.
• 3. Reflectivity from the WCR is consistently higher than from NOAA-K.
• 4. Velocity measurements are in excellent agreement, except for the 6 m/s value for the dizzle with NOAA-K in Case 1. This latter value is a puzzle at this time.
• 5. Reflectivity calculated from in-situ data is 3-5 dBZ lower than measured values in Case 1, and is in exact agreement with measurements in Case 2.

Case 1:

The KingAir flew over the NOAA Ka site (lat=N45.82, lon=W123.92) about 100 m North of the site and 5 seconds after NOAA radar was at 90 deg elevation. The NOAA radar was scanning continuously between 20 and 160 deg elevations and 270 azimuth. Thus, the best comparison is between the NOAA uplooking data at 16:18:55 and the WCR data during KingAir overflight at 16:18:49. No attenuation correction was applied to either sets of radar reflectivity data.

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Case 2:

KingAir overflight above the NOAA Ka site on Sep 6, 1995 at 16:54:32 UTC

The KingAir overflew the NOAA radar 500 m North of the site and 25 seconds before the NOAA radar was pointing at the zenith. There was a pronounced reflectivity gradient in the West-East plane over the site. This led to a decrease of about 4 dBZ between 16:53:37 and 16:54:58 at low altitudes. Therefore, in this case the comparison was not done for 90 deg elevation with the NOAA radar. The selected data segments coincide in time but there is about 500 m horizontal separation in the sampled volumes. The velocity comparison is for the vertically pointing NOAA radar at 16:54:58 and KingAir overflight at 16:54:32.

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