Total ice water content (IWC) derived from an isokinetic evaporator probe and ice crystal particle size distributions (PSDs) measured by a two-dimensional stereo probe and precipitation imaging probe installed on an aircraft during the 2014 European High Altitude Ice Crystals–North American High IWC field campaign (HAIC/HIWC) were used to characterize regions of high IWC consisting mainly of small ice crystals (HIWC_S) with IWC ≥ 1.0 g m−3and median mass diameter (MMD) < 0.5 mm. A novel fitting routine developed to automatically determine whether a unimodal, bimodal, or trimodal gamma distribution best fits a PSD was used to compare characteristics of HIWC_S and other PSDs (e.g., multimodality, gamma fit parameters) for HIWC_S simulations. The variation of these characteristics and bulk properties (MMD, IWC) was regressed with temperature, IWC, and vertical velocity. HIWC_S regions were most pronounced in updraft cores. The three modes of the PSD reveal different dominant processes contributing to ice growth: nucleation for maximum dimension
Dependence of Ice Crystal Size Distributions in High Ice Water Content Conditions on Environmental Conditions: Results from the HAIC-HIWC Cayenne Campaign
Abstract A new method that automatically determines the modality of an observed particle size distribution (PSD) and the representation of each mode as a gamma function was used to characterize data obtained during the High Altitude Ice Crystals and High Ice Water Content (HAIC-HIWC) project based out of Cayenne, French Guiana, in 2015. PSDs measured by a 2D stereo probe and a precipitation imaging probe for particles with maximum dimension ( D max ) > 55 μ m were used to show how the gamma parameters varied with environmental conditions, including temperature ( T ) and convective properties such as cloud type, mesoscale convective system (MCS) age, distance away from the nearest convective peak, and underlying surface characteristics. Four kinds of modality PSDs were observed: unimodal PSDs and three types of multimodal PSDs (Bimodal1 with breakpoints 100 ± 20 μ m between modes, Bimodal2 with breakpoints 1000 ± 300 μ m, and Trimodal PSDs with two breakpoints). The T and ice water content (IWC) are the most important factors influencing the modality of PSDs, with the frequency of multimodal PSDs increasing with increasing T and IWC. An ellipsoid of equally plausible solutions in ( N o – λ–μ ) phase space is defined for each mode of the observed PSDs for different environmental conditions. The percentage overlap between ellipsoids was used to quantify the differences between overlapping ellipsoids for varying conditions. The volumes of the ellipsoid decrease with increasing IWC for most cases, and ( N o – λ–μ ) vary with environmental conditions related to distribution of IWC. HIWC regions are dominated by small irregular ice crystals and columns. The parameters ( N o – λ–μ ) in each mode exhibit mutual dependence.
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- Award ID(s):
- 1842094
- NSF-PAR ID:
- 10413487
- Date Published:
- Journal Name:
- Journal of the Atmospheric Sciences
- Volume:
- 79
- Issue:
- 12
- ISSN:
- 0022-4928
- Page Range / eLocation ID:
- 3103 to 3134
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract This study investigates the evolution of temperature and lifetime of evaporating, supercooled cloud droplets considering initial droplet radius (
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1175/JAS-D-22-0008.1
