A new look at the environmental conditions favorable to secondary ice production
Por:
Korolev, Alexei, Heckman, Ivan, Wolde, Mengistu, Ackerman, Andrew S., Fridlind, Ann M., Ladino, Luis A., Paul Lawson R., Milbrandt, Jason, Williams, Earle
Publicada:
1 ene 2020
Categoría:
Atmospheric science
Resumen:
This study attempts a new identification of mechanisms of secondary ice production (SIP) based on the observation of small faceted ice crystals (hexagonal plates or columns) with typical sizes smaller than 100 µ m. Due to their young age, such small ice crystals can be used as tracers for identifying the conditions for SIP. Observations reported here were conducted in oceanic tropical mesoscale convective systems (MCSs) and midlatitude frontal clouds in the temperature range from 0 to-15 °C and heavily seeded by aged ice particles. It was found that in both MCSs and frontal clouds, SIP was observed right above the melting layer and extended to higher altitudes with colder temperatures. The roles of six possible mechanisms to generate the SIP particles are assessed using additional observations. In most observed SIP cases, small secondary ice particles spatially correlated with liquid-phase, vertical updrafts and aged rimed ice particles. However, in many cases, neither graupel nor liquid drops were observed in the SIP regions, and therefore, the conditions for an active Hallett-Mossop process were not met. In many cases, large concentrations of small pristine ice particles were observed right above the melting layer, starting at temperatures as warm as-0:5 °C. It is proposed that the initiation of SIP above the melting layer is stimulated by the recirculation of large liquid drops through the melting layer with convective turbulent updrafts. After re-entering a supercooled environment above the melting layer, they impact with aged ice, freeze, and shatter. The size of the splinters generated during SIP was estimated as 10 µ m or less. A principal conclusion of this work is that only the freezingdrop-shattering mechanism could be clearly supported by the airborne in situ observations. © 2020 Author(s).
Filiaciones:
Korolev, Alexei:
Environment and Climate Change Canada, Toronto, ON, Canada
Environm & Climate Change Canada, Toronto, ON, Canada
Heckman, Ivan:
Environment and Climate Change Canada, Toronto, ON, Canada
Environm & Climate Change Canada, Toronto, ON, Canada
Wolde, Mengistu:
National Research Council, Ottawa, ON, Canada
CNR, Ottawa, ON, Canada
Ackerman, Andrew S.:
NASA Goddard Institute for Space Studies, New York, NY, United States
NASA, Goddard Inst Space Studies, New York, NY 10025 USA
Fridlind, Ann M.:
NASA Goddard Institute for Space Studies, New York, NY, United States
NASA, Goddard Inst Space Studies, New York, NY 10025 USA
Ladino, Luis A.:
Environment and Climate Change Canada, Toronto, ON, Canada
Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Mexico City, Mexico
Environm & Climate Change Canada, Toronto, ON, Canada
Univ Nacl Autonoma Mexico, Ctr Ciencias Atmosfera, Mexico City, DF, Mexico
Paul Lawson R.:
Stratton Park Engineering Company, Boulder, CO, United States
Milbrandt, Jason:
Environment and Climate Change Canada, Toronto, ON, Canada
Environm & Climate Change Canada, Toronto, ON, Canada
Williams, Earle:
Massachusetts Institute of Technology, Boston, MA, United States
MIT, Boston, MA USA
Stratton Pk Engn Co, Boulder, CO USA
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