Motivation: The a and b coefficients of ice particle mass (m)-Dimension (D) relationships are typically represented as a power law of the form m = a*D**b, and can vary significantly depending on meteorological conditions, particle habits, the probes used to obtain the data, techniques used to process the cloud probe data, and other unknown reasons. My Ph.D. work aims to improve how these relations are used in remote sensing retrievals and microphysical parameterization schemes.
How It’s Done: Ground-based radar and in-situ microphysics data are combined to create a colocated dataset that allows total water content (TWC) measurements and radar reflectivity (Z) to be compared to TWC/Z derived from ice particle size distributions (PSDs) using a χ² minimization procedure. This technique also considers uncertainties in the measurements to allow a range of a and b coefficients to be regarded as equally plausible for similar environmental conditions (i.e. temperature or TWC).
Preliminary Results: For a given environment, the range of equally plausible solutions are represented as a surface in (a,b) phase space. Below is an example of how these coefficients vary as a function of temperature and storm environment during the Mid-latitude Continental Convective Clouds Experiment (MC3E).
Work is ongoing to expand the technique to more flights that span a wider range of environmental conditions such as temperature and TWC. Much like MC3E, which is part of a series of Global Precipitation Measurement (GPM) ground validation field studies, data from the GPM Cold Precipitation Experiment (GCPEx) and Olympic Mountains Experiment (OLYMPEX) are being used to better understand how m-D empirical relationships are influenced by the storm environment.
A manuscript detailing the construction of these a/b surfaces and results from MC3E are available as a preprint in ACP: https://www.atmos-chem-phys-discuss.net/acp-2018-795/