SGP WACR and MMCR Reflectivity ComparisonA Diagnostic Tool?

Kevin Widener, Pacific Northwest National LaboratoryIntroductionA comparison of the data from the SGP WACR (94 GHz) and MMCR (35 GHz) is made for datacollected in 2007. The purpose of this radar reflectivity comparison is to ascertain whether thiscould serve as an automatic diagnostic for MMCR calibration since the WACR has an absolutereference by looking at a corner reflector. As can be seen, the differences can be significant butthey can also be right on.

ConclusionCan a comparison between MMCR and WACR serve as a diagnostic? Maybe, but care must betaken to account for Mie effects. Insects hinder the use of boundary layer clouds, especially atSGP.

MethodologyData selection criteria:

• Portions of clouds with little intervening atmospheric loss• Different cloud types and heights• No precipitation• No bugs

Data processing:• MMCR General mode• WACR co-polarization mode• MMCR scaled to match WACR resolution• Mean reflectivity vs. height comparison

Future Plans•Statistical comparison with cloud mask for all data.•AMF and SGP WACR Intercomparison between Germany and China deployments.•SGP WACR Scanning modification will be contracted in 2008 and completed in 2009. TheScanning WACR may then be deployed with the AMF in 2009.

ReferencesHogan, R.J., N. Gaussiat, A.J. Illingsworth, 2005: Stratocumulus Liquid Water Content from Dual-Wavelength Radar, J. Atmos. Oceanic Technol., 22, 1207-1218Matrosov, S.Y., A.J. Heymsfield, and Z. Wang, 2005: Dual-frequency radar ratio of nonspherical atmospheric hydrometeors, Geophys. Res. Lett., 32, L13816Sekelsky, S.M., W.L. Ecklund, J.M. Firda, K.S. Gage, and R.E. McIntosh, 1999: Particle Size Estimation in Ice-Phase Clouds Using Multifrequency Radar Reflectivity Measurements at 95, 33, and 2.8 GHz, J. Atmos. Sci., 38, 5-28

Converges as height increases

Constant MMCR > WACR (~2 dBZe)

Constant WACR > MMCR (~3 dBZe)

Constant MMCR > WACR (~3 dBZe)

Equivalent in one section and divergent in another section

Possible causes for differences:• Calibration errors• Different antenna beamwidths: MMCR = 0.19° and WACR = 0.37°• Mie Effects

Daily Plot Cloud Sample Mean and Difference

Backscatter from sphere

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35 GHz - 94 GHz Cross-section Difference for Sphere

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MMCR General Mode Reflectivity 20071206 05:36 - 07:41

WACR Co-POL Reflectivity 20071206 05:36 - 07:41

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Mean Reflectivity 20071206 05:36 - 07:41

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Mean Reflectivity 20071206 03:39 - 04:07

Reflectivity (dBZe)

Reflectivity (dBZe)

MMCR General Mode Reflectivity 20071206 03:39 - 04:07

WACR Co-POL Reflectivity 20071206 03:39 - 04:07 Ran

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MMCR General Mode Reflectivity 20071206

WACR Co-POL Reflectivity 20071206

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Mean Reflectivity 20070330 00:01 - 02:25

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Mean Reflectivity 20070330 15:08 - 17:58

MMCR General Mode Reflectivity 20070330 00:01 - 02:25

WACR Co-POL Reflectivity 20070330 00:01 - 02:25

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MMCR General Mode Reflectivity 20070330 15:08 - 17:58

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WACR Co-POL Reflectivity 20070330 15:08 - 17:58

MMCR General Mode Reflectivity 20070330

WACR Co-POL Reflectivity 20070330

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MMCR General Mode Reflectivity 20070330

WACR Co-POL Reflectivity 20070330

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MMCR General Mode Reflectivity 20070412

WACR Co-POL Reflectivity 20070412

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MMCR General Mode Reflectivity 20070412 10:29 - 12:09

WACR Co-POL Reflectivity 20070412 10:29 - 12:09

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Mean Reflectivity 20070412 10:29 - 12:09

Mean Reflectivity 20070603 10:20 - 13:48

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Reflectivity (dBZe)

MMCR General Mode Reflectivity 20070630 10:20 - 13:48

WACR Co-POL Reflectivity 20070630 10:20 - 13:48

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MMCR General Mode Reflectivity 20070412

WACR Co-POL Reflectivity 20070412

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