Verification of Dual-wavelength Humidity Profile Retrievals Using S-PolKa During the DYNAMO Field Campaign

The NCAR scanning, S- and Ka-band dual-wavelength, dual-polarimetric, radar (S-PolKa) makes simultaneous S-band and Ka-band measurements with 1 degree beamwidth and nominal range resolution of 150 m. Both radars have dual-polarization and Doppler measurement capabilities. The S-PolKa radar is a resource to the research community as part of the NSF Deployment Pool and has been deployed for atmospheric studies around the world. The dual-wavelength and dual-polarization capabilities of S-PolKa enable the estimation of humidity profiles in the lower troposphere and liquid water content (LWC).

The S-PolKa system was deployed in the Maldives for 4.5 months during the Dynamics of the Madden Julian Oscillation (DYNAMO) field campaign. The humidity retrievals showed a large spatial and temporal variability that was also reflected in the sounding data. The S-PolKa retrieved humidity is verified against the 3 hourly sounding data using only data that was very close in time and space in order to minimize the impact of the natural variability and the sampling differences. The comparison indicated the radar humidity retrievals were unbiased in comparison to the sounding measurements. The retrievals are then used to investigate the variability of the humidity in the tropical DYNAMO domain. Because the radar retrievals cover a large spatial scale compared to soundings, the environmental mean and standard deviation of humidity lower troposphere can be estimated. This information is important to numerical modeling and process studies.