Linkage among ice crystal microphysics, mesoscale dynamics, and cloud and precipitation structures revealed by collocated microwave radiometer and multifrequency radar observations
<p>Ice clouds and falling snow are ubiquitous globally and play important roles in the Earth's radiation budget and precipitation processes. Ice particle microphysical properties (e.g., size, habit and orientation) are not only influenced by the ambient environment's dynamic and ther...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/20/12633/2020/acp-20-12633-2020.pdf |
| Summary: | <p>Ice clouds and falling snow are ubiquitous globally and
play important roles in the Earth's radiation budget and precipitation
processes. Ice particle microphysical properties (e.g., size, habit and
orientation) are not only influenced by the ambient environment's dynamic
and thermodynamic conditions, but are also intimately connected to the cloud
radiative effects and particle fall speeds, which therefore have an impact
on future climate projection as well as on the details of the surface
precipitation (e.g., onset time, location, type and strength).</p>
<p>Our previous work revealed that high-frequency (<span class="inline-formula">></span> 150 GHz)
polarimetric radiance difference (PD) from passive microwave sensors is a
good indicator of the bulk aspect ratio of horizontally oriented ice
particles that often occur inside anvil clouds and/or stratiform
precipitation. In this current work, we further investigate the
dynamic and thermodynamic mechanisms and cloud–precipitation structures
associated with ice-phase microphysics corresponding to different PD
signals. In order to do so, collocated CloudSat radar (W-band) and Global
Precipitation Measurement Dual-frequency Precipitation Radar (GPM DPR, Ku–Ka-bands) observations as well as European Centre for Medium-Range Weather
Forecasts (ECMWF) atmosphere background profiles are grouped according to
the magnitude of PD for only stratiform precipitation and/or anvil cloud
scenes. We found that horizontally oriented snow aggregates or large snow
particles are likely the major contributor to the high-PD signals at 166 GHz, while low-PD magnitudes can be attributed to small cloud ice, randomly
oriented snow aggregates, riming snow or supercooled water. Further, high-PD
(low-PD) scenes are found to be associated with stronger (weaker) wind shear
and higher (lower) ambient humidity, both of which help promote (prohibit)
the growth of frozen particles and the organization of convective systems.
An ensemble of squall line cases is studied at the end to demonstrate that
the PD asymmetry in the leading and trailing edges of the deep convection
line is closely tied to the anvil cloud and stratiform precipitation layers,
respectively, suggesting the potential usefulness of PD as a proxy of
stratiform–convective precipitation flag, as well as a proxy of convection
life stage.</p> |
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| ISSN: | 1680-7316 1680-7324 |