Integrated framework for retrievals in a networked radar environment and error characterization of retrievals

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Description

The Midlatitude Continental Convective Clouds Experiment (MC3E) (Jensen et al. 2011) was a joint DOE Atmospheric Radiation Measurement (ARM) Climate Research Facility and NASA Global Precipitation Measurement (GPM) field campaign that took place from April–June 2011 in central Oklahoma centered at the ARM Southern Great Plains site. The field campaign involved a large suite of observing infrastructure currently available in the central United States, combined with an extensive sounding array, remote sensing and in situ aircraft observations, NASA GPM ground validation remote sensors, and new ARM instrumentation. The overarching goal was to provide the most complete characterization of convective cloud systems, precipitation, and the environment that has ever been obtained, providing constraints for model cumulus parameterizations and space-based rainfall retrieval algorithms over land that had never before been available. The experiment consisted of a large number of ground radars, including NASA scanning dual-polarization radar systems (NPOL) at S-band, wind profilers, and a dense network of surface disdrometers. In addition to these special MC3E instruments, there were three networked scanning X-band radar systems, four wind profilers, a C-band scanning radar, and a dual-wavelength (Ka/W) scanning cloud radar.

There is extensive literature on the retrieval algorithms for precipitation and cloud parameters from single-frequency, dual-polarization radar systems. With the cost of instruments such as radars becoming more affordable, multiple radar deployments are becoming more common in special programs, and MC3E is a textbook example of such a deployment. Networked deployments are becoming more common, popularized by the Collaborative Adaptive Sensing of the Atmosphere (CASA) program (Chandrasekar et al. 2010), resulting in networked retrievals, which were initially used for attenuation mitigation. Since then networked retrievals have expanded reach to include retrieval of drop size distribution (DSDs) from networked X-band or Ku-band radars (Yoshikawa et al. 2012). All the above retrieval methodologies were for homogeneous, single-frequency systems; however, the multi-frequency nature of the deployment during MC3E is the motivation for the integrated formulation presented in this paper.

This paper presents a comprehensive integrated retrieval methodology to obtain microphysical retrieval such as the DSD for the complete MC3E network for the multi-frequency radar systems. The basic principles of the methodology include a Maximum Likelihood formulation of the microphysical parameter retrievals, while maximizing the posterior probabilities of the multiple retrieval systems. Numerical simulations are used to establish the integrity of the retrievals followed by demonstration with radar and in situ observations.