Relationships between mass and particle size derived from aircraft data collected during Stormvex

Description

Mixed-phase clouds, where ice particles and supercooled liquid droplets co-exist, are widely distributed. The specific properties of mixed-phase clouds play a crucial role in determining their radiative properties, lifetimes and the precipitation generated by them. The complicated nature of mixed-phased clouds and a limited amount of data available from them result in uncertainties in retrieving the cloud and precipitation properties and in representing their physical process in predictive models. In the winter 2010-2011, two field campaigns were conducted in Steamboat Springs, CO. The NSF-funded Colorado Airborne Multi-Phase Cloud Study (CAMPS) and the ARM-funded Storm Peak Laboratory Cloud Property Validation Experiment (StormVEx) gathered a large correlative data set of remote sensing observations and in situ measurements in mixed-phase precipitating clouds. As part of CAMPS, the Wyoming King Air research aircraft performed 29 flights. Data were collected regarding the vertical and horizontal structure of winter mixed-phase clouds with both remote and in situ sensors that contain particle probes. Crucially, bulk probes that measured liquid and total water content were also part of the King Air instrumentation. The inference of bulk ice water from the difference between the total water and liquid water contents allow us to examine the relationships between mass and particle size that is an important unknown for both retrievals and atmospheric models. Optimal estimation (OE) is a commonly used inverse method in the geosciences. Based on Bayes theorem, OE can return an optimal solution by maximizing the a posteriori probability. In this study, an OE algorithm is applied to retrieve the parameters of the mass-dimensional power law relationship (M=a*Db) of ice particles in mixed-phase clouds using King Air data. We assume modified gamma distribution for the ice particle size distribution in our forward model that, in turn, is derived from airborne imaging probes. Ice mass is calculated using total condensed water content and liquid water content from the King Air in situ sensors closed-path tunable-diode laser hygrometer and cloud droplet probe. In our poster, we will describe the retrieval algorithm in detail and the uncertainties of deployed in situ sensors will be quantified. The parameters of mass-dimension relationships for different ice crystal habits will be presented and application of these parameters to different cases will be discussed.