Polarimetric radar and in situ observations of riming and snowfall microphysics during CLACE 2014
This study investigates the microphysics of winter alpine snowfall occurring in mixed-phase clouds in an inner-Alpine valley during January and February 2014. The available observations include high-resolution polarimetric radar and in situ measurements of the ice-phase and liquid-phase components o...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/15/13787/2015/acp-15-13787-2015.pdf |
| Summary: | This study investigates the microphysics of winter alpine snowfall occurring
in mixed-phase clouds in an inner-Alpine valley during January and February
2014. The available observations include high-resolution polarimetric radar
and in situ measurements of the ice-phase and liquid-phase components of
clouds and precipitation. Radar-based hydrometeor classification suggests
that riming is an important factor to favor an efficient growth of the
precipitating mass and correlates with snow accumulation rates at ground
level. The time steps during which rimed precipitation is dominant are
analyzed in terms of temporal evolution and vertical structure. Snowfall
identified as rimed often appears after a short time period during which the
atmospheric conditions favor wind gusts and updrafts and supercooled liquid
water (SLW) is available. When a turbulent atmospheric layer persists for
several hours and ensures continuous SLW generation, riming can be sustained
longer and large accumulations of snow at ground level can be generated. The
microphysical interpretation and the meteorological situation
associated with one such event are detailed in the paper. The vertical
structure of polarimetric radar observations during intense snowfall
classified as rimed shows a peculiar maximum of specific differential phase
shift <i>K</i><sub>dp</sub>, associated with large number concentrations and riming of
anisotropic crystals. Below this <i>K</i><sub>dp</sub> peak there is usually an
enhancement in radar reflectivity <i>Z</i><sub>H</sub>, proportional to the <i>K</i><sub>dp</sub>
enhancement and interpreted as aggregation of ice crystals. These
signatures seem to be recurring during intense snowfall. |
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| ISSN: | 1680-7316 1680-7324 |