Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurements
Scattering differences induced by frozen particle microphysical properties are investigated, using the vertically (V) and horizontally (H) polarized radiances from the Global Precipitation Measurement (GPM) Microwave Imager (GMI) 89 and 166 GHz channels. It is the first study on frozen particle micr...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/2741/2017/acp-17-2741-2017.pdf |
| _version_ | 1811300390350618624 |
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| author | J. Gong D. L. Wu |
| author_facet | J. Gong D. L. Wu |
| author_sort | J. Gong |
| collection | DOAJ |
| description | Scattering differences induced by frozen particle
microphysical properties are investigated, using the vertically (V) and
horizontally (H) polarized radiances from the Global Precipitation
Measurement (GPM) Microwave Imager (GMI) 89 and 166 GHz channels. It is the
first study on frozen particle microphysical properties on a global scale
that uses the dual-frequency microwave polarimetric signals.<br><br>From the ice cloud scenes identified by the 183.3 ± 3 GHz channel
brightness temperature (<i>T</i><sub>b</sub>), we find that the scattering by frozen particles is highly
polarized, with V–H polarimetric differences (PDs) being positive throughout
the tropics and the winter hemisphere mid-latitude jet regions, including PDs
from the GMI 89 and 166 GHz TBs, as well as the PD at 640 GHz from the ER-2
Compact Scanning Submillimeter-wave Imaging Radiometer (CoSSIR) during the
TC4 campaign. Large polarization dominantly occurs mostly near convective
outflow regions (i.e., anvils or stratiform precipitation), while the
polarization signal is small inside deep convective cores as well as at the
remote cirrus region. Neglecting the polarimetric signal would easily result
in as large as 30 % error in ice water path retrievals. There is a
universal <q>bell curve</q> in the PD–TB<sub>V</sub> relationship, where the PD amplitude
peaks at ∼ 10 K for all three channels in the tropics and increases
slightly with latitude (2–4 K). Moreover, the 166 GHz PD tends to increase
in the case where a melting layer is beneath the frozen particles aloft in
the atmosphere, while 89 GHz PD is less sensitive than 166 GHz to the
melting layer. This property creates a unique PD feature for the
identification of the melting layer and stratiform rain with passive sensors.<br><br>Horizontally oriented non-spherical frozen particles are thought to produce
the observed PD because of different ice scattering properties in the V and H
polarizations. On the other hand, turbulent mixing within deep convective
cores inevitably promotes the random orientation of these particles, a
mechanism that works effectively in reducing the PD. The current GMI
polarimetric measurements themselves cannot fully disentangle the possible
mechanisms. |
| first_indexed | 2024-04-13T06:51:32Z |
| format | Article |
| id | doaj.art-944f72656363486db164d36e59b5a58f |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-13T06:51:32Z |
| publishDate | 2017-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-944f72656363486db164d36e59b5a58f2022-12-22T02:57:24ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242017-02-011742741275710.5194/acp-17-2741-2017Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurementsJ. Gong0D. L. Wu1Universities Space Research Association, Columbia, MD, USAClimate and Radiation Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USAScattering differences induced by frozen particle microphysical properties are investigated, using the vertically (V) and horizontally (H) polarized radiances from the Global Precipitation Measurement (GPM) Microwave Imager (GMI) 89 and 166 GHz channels. It is the first study on frozen particle microphysical properties on a global scale that uses the dual-frequency microwave polarimetric signals.<br><br>From the ice cloud scenes identified by the 183.3 ± 3 GHz channel brightness temperature (<i>T</i><sub>b</sub>), we find that the scattering by frozen particles is highly polarized, with V–H polarimetric differences (PDs) being positive throughout the tropics and the winter hemisphere mid-latitude jet regions, including PDs from the GMI 89 and 166 GHz TBs, as well as the PD at 640 GHz from the ER-2 Compact Scanning Submillimeter-wave Imaging Radiometer (CoSSIR) during the TC4 campaign. Large polarization dominantly occurs mostly near convective outflow regions (i.e., anvils or stratiform precipitation), while the polarization signal is small inside deep convective cores as well as at the remote cirrus region. Neglecting the polarimetric signal would easily result in as large as 30 % error in ice water path retrievals. There is a universal <q>bell curve</q> in the PD–TB<sub>V</sub> relationship, where the PD amplitude peaks at ∼ 10 K for all three channels in the tropics and increases slightly with latitude (2–4 K). Moreover, the 166 GHz PD tends to increase in the case where a melting layer is beneath the frozen particles aloft in the atmosphere, while 89 GHz PD is less sensitive than 166 GHz to the melting layer. This property creates a unique PD feature for the identification of the melting layer and stratiform rain with passive sensors.<br><br>Horizontally oriented non-spherical frozen particles are thought to produce the observed PD because of different ice scattering properties in the V and H polarizations. On the other hand, turbulent mixing within deep convective cores inevitably promotes the random orientation of these particles, a mechanism that works effectively in reducing the PD. The current GMI polarimetric measurements themselves cannot fully disentangle the possible mechanisms.http://www.atmos-chem-phys.net/17/2741/2017/acp-17-2741-2017.pdf |
| spellingShingle | J. Gong D. L. Wu Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurements Atmospheric Chemistry and Physics |
| title | Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurements |
| title_full | Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurements |
| title_fullStr | Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurements |
| title_full_unstemmed | Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurements |
| title_short | Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurements |
| title_sort | microphysical properties of frozen particles inferred from global precipitation measurement gpm microwave imager gmi polarimetric measurements |
| url | http://www.atmos-chem-phys.net/17/2741/2017/acp-17-2741-2017.pdf |
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