TY - JOUR
T1 - Dynamical conditions of ice supersaturation and ice nucleation in convective systems
T2 - A comparative analysis between in situ aircraft observations and WRF simulations
AU - D’Alessandro, John J.
AU - Diao, Minghui
AU - Wu, Chenglai
AU - Liu, Xiaohong
AU - Chen, Ming
AU - Morrison, Hugh
AU - Eidhammer, Trude
AU - Jensen, Jorgen B.
AU - Bansemer, Aaron
AU - Zondlo, Mark Andrew
AU - DiGangi, Josh P.
N1 - Funding Information:
M. Diao acknowledges the funding support of the National Center for Atmospheric Research (NCAR) Advanced Study Program (ASP) Faculty Fellowship in 2016. NCAR is sponsored by the National Science Foundation. J.D’Alessandro acknowledges the sup port of the Walker Graduate Fellowship from San Jose State University. X. Liu and C. Wu acknowledge support of the U.S. Department of Energy’s Atmospheric System Research Program (grant DE-SC0014239). For in situ observations on board the NSF GV research aircraft during the DC3 cam paign, the VCSEL hygrometer QC/QA is conducted by Josh DiGangi, Minghui Diao, Mark Zondlo, and Stuart Beaton; the Fast-2DC probe QC/QA is conducted by Aaron Bansemer; and the Rosemount temperature probe and vertical velocity measurements QC/QA are conducted by William Cooper and Jorgen Jensen. We thank the pilots and flight crew at the NCAR Research Aviation Facility for field support. The NSF DC3 data set is publically available and can be accessed at http://data.eol.ucar.edu/master_list/? project=DC3.
Publisher Copyright:
© 2017. American Geophysical Union. All Rights Reserved.
PY - 2017
Y1 - 2017
N2 - Occurrence frequency and dynamical conditions of ice supersaturation (ISS, where relative humidity with respect to ice (RHi)>100%) are examined in the upper troposphere around convective activity. Comparisons are conducted between in situ airborne observations and the Weather Research and Forecasting model simulations using four double-moment microphysical schemes at temperatures ≤ 40°C. All four schemes capture both clear-sky and in-cloud ISS conditions. However, the clear-sky (in-cloud) ISS conditions are completely (significantly) limited to the RHi thresholds of the Cooper parameterization. In all of the simulations, ISS occurrence frequencies are higher by ~34 orders of magnitude at higher updraft speeds (>1 ms-1) than those at the lower updraft speeds when ice water content (IWC)>0.01 gm-3, while observations show smaller differences up to ~1-2 orders of magnitude. The simulated ISS also occurs less frequently at weaker updrafts and downdrafts than observed. These results indicate that the simulations have a greater dependence on stronger updrafts to maintain/generate ISS at higher IWC. At lower IWC (≤0.01 gm-3), simulations unexpectedly show lower ISS frequencies at stronger updrafts. Overall, the Thompson aerosol-aware scheme has the closest magnitudes and frequencies of ISS >20% to the observations, and the modified Morrison has the closest correlations between ISS frequencies and vertical velocity at higher IWC and number density. The Cooper parameterization often generates excessive ice crystals and therefore suppresses the frequency and magnitude of ISS, indicating that it should be initiated at higher ISS (e.g., ≥25%).
AB - Occurrence frequency and dynamical conditions of ice supersaturation (ISS, where relative humidity with respect to ice (RHi)>100%) are examined in the upper troposphere around convective activity. Comparisons are conducted between in situ airborne observations and the Weather Research and Forecasting model simulations using four double-moment microphysical schemes at temperatures ≤ 40°C. All four schemes capture both clear-sky and in-cloud ISS conditions. However, the clear-sky (in-cloud) ISS conditions are completely (significantly) limited to the RHi thresholds of the Cooper parameterization. In all of the simulations, ISS occurrence frequencies are higher by ~34 orders of magnitude at higher updraft speeds (>1 ms-1) than those at the lower updraft speeds when ice water content (IWC)>0.01 gm-3, while observations show smaller differences up to ~1-2 orders of magnitude. The simulated ISS also occurs less frequently at weaker updrafts and downdrafts than observed. These results indicate that the simulations have a greater dependence on stronger updrafts to maintain/generate ISS at higher IWC. At lower IWC (≤0.01 gm-3), simulations unexpectedly show lower ISS frequencies at stronger updrafts. Overall, the Thompson aerosol-aware scheme has the closest magnitudes and frequencies of ISS >20% to the observations, and the modified Morrison has the closest correlations between ISS frequencies and vertical velocity at higher IWC and number density. The Cooper parameterization often generates excessive ice crystals and therefore suppresses the frequency and magnitude of ISS, indicating that it should be initiated at higher ISS (e.g., ≥25%).
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U2 - 10.1002/2016JD025994
DO - 10.1002/2016JD025994
M3 - Article
AN - SCOPUS:85014067483
SN - 0148-0227
VL - 122
SP - 2844
EP - 2866
JO - Journal of Geophysical Research
JF - Journal of Geophysical Research
IS - 5
ER -