Search for: All records

This dataset is comprised of a series of PDF flight summaries that describe the general microphysical characteristics that were recorded along each flight leg for the 9 research flight missions of the WINTRE-MIX NRC Convair-580 aircraft. Each summary includes a written overview of the IOP and orientation of performed flight legs as well as a description of the microphysical characteristics of cloud measured along each transect by the NRC Convair-580. Several figures are provided for each flight leg detailing microphysical parameters such as particle number concentration and mean size distributions measured across these periods. Particle imagery from the 2DS probe is also provided for select periods across all flight legs to demonstrate the cloud composition of the weather systems of focus for each flight. General atmospheric state statistics are also provided in these summaries, as well as any data limitations observed with the parameters provided in each summary. 

Abstract During freezing rain, secondary ice produced by the fragmentation of freezing drops (FFD) can initiate a chain reaction, potentially transitioning freezing rain into ice pellets. Including this process in numerical weather prediction models is challenging due to the uncertainty of this mechanism. To bridge this gap, this study aims to evaluate the efficiency of the FFD process during ice pellet precipitation using measurements collected onboard the National Research Council Canada (NRC) Convair-580 research aircraft during the 2022 Winter Precipitation Type Research Multiscale Experiment (WINTRE-MIX). Below the supercooled raindrops freezing altitude, in situ probes measured a bimodal particle size distribution. Observations from imaging and optical-array probes show that most particles smaller than 500μm in diameter were nonspherical ice crystals, in the concentration of ∼500 L⁻¹. In contrast, most particles larger than 500μm were identified as fractured ice pellets and ice pellets with bulges, which suggested the occurrence of the FFD process. A conceptual model is then developed to show that five–eight fragments of ice were produced for each freezing drop. Two existing parameterizations of the FFD process are also tested. It is shown that one parameterization would result in less ice crystals than the measured number concentration, while the second one would result in too many ice crystals. Adjustments to these parameterizations are computed based on the collected observations. This analysis will be valuable for including the FFD process into simulations of freezing rain, ice pellets, and other weather phenomena where this process plays a significant role. Significance StatementThis study presents unique measurements from a winter storm recorded by state-of-the-art instruments onboard a research aircraft at the altitude where ice pellets are formed. The collected data suggest that the freezing of a few initial raindrops at an altitude of around 250 m above the ground resulted in the production of ice crystals. These ice crystals led to the freezing of additional raindrops in a feedback loop that can be referred to as ice multiplication. This process is quantified in the current study. The results will be valuable in improving the representation of ice pellets and freezing rain in computer simulations of winter storms. 

Abstract Kelvin–Helmholtz instability (KH) waves have been broadly shown to affect the growth of hydrometeors within a region of falling precipitation, but formation and growth from KH waves at cloud top needs further attention. Here, we present detailed observations of cloud-top KH waves that produced a snow plume that extended to the surface. Airborne transects of cloud radar aligned with range height indicator scans from ground-based precipitation radar track the progression and intensity of the KH wave kinetics and precipitation. In situ cloud probes and surface disdrometer measurements are used to quantify the impact of the snow plume on the composition of an underlying supercooled liquid water (SLW) cloud and the snowfall observed at the surface. KH wavelengths of 1.5 km consisted of ∼750-m-wide up- and downdrafts. A distinct fluctus region appeared as a wave-breaking cloud top where the fastest updraft was observed to exceed 5 m s⁻¹. Relatively weaker updrafts of 0.5–1.5 m s⁻¹beneath the fluctus and partially overlapping the dendritic growth zone were associated with steep gradients in reflectivity of −5 to 20 dBZ_ein as little as 500-m depths due to rapid growth of pristine planar ice crystals. The falling snow removed ∼80% of the SLW content from the underlying cloud and led to a twofold increase in surface liquid equivalent snowfall rate from 0.6 to 1.3 mm h⁻¹. This paper presents the first known study of cloud-top KH waves producing snowfall with observations of increased snowfall rates at the surface.