Cluster analysis of vertical polarimetric radio occultation profiles and corresponding liquid and ice water paths from Global Precipitation Measurement (GPM) microwave data
<p>Polarimetric radio occultations (PROs) of the Global Navigation Satellite System are able to characterize precipitation structure and intensity. Prior studies have shown the relationship between precipitation and water vapor pressure columns, known as the “precipitation pickup.” Less is kno...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-02-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/18/953/2025/amt-18-953-2025.pdf |
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| Summary: | <p>Polarimetric radio occultations (PROs) of the Global Navigation Satellite System are able to characterize precipitation structure and intensity. Prior studies have shown the relationship between precipitation and water vapor pressure columns, known as the “precipitation pickup.” Less is known about the relationship between the vertical distributions of temperature and moisture globally within precipitating scenes as measured from space. This work uses cluster analysis of PRO to explore how the vertical distributions of temperature and moisture – combined into PRO refractivity – relate to vertical distributions of precipitation and moisture variables. We evaluate the ability of <span class="inline-formula"><i>k</i></span>-means clustering to find relationships among PRO polarimetric phase difference, refractivity, liquid water path (LWP), ice water path (IWP), and water vapor pressure using over 2 years of data matched between the Global Precipitation Measurement (GPM) mission and the radio occultations (ROs) and heavy precipitation (HP) demonstration mission on board the Spanish Paz spacecraft (ROHP-PAZ). A polytropic potential refractivity model for polytropic atmospheres is introduced to ascertain how different vertical thermodynamic profiles that can occur during different precipitation scenarios are related to changes in the polytropic index and thereby vertical heat transfer rates. The cluster analyses suggest a relationship between the amplitude and shape of deviations from the potential refractivity model and water vapor pressure. These analyses also confirm a positive correlation between vertical shapes of polarimetric phase difference and both LWP and IWP. For certain values, the coefficients of the polytropic potential refractivity model flag physical vs. nonphysical retrievals and indicate when a profile has little to no moisture. The study reveals a similar relationship between the clustering for these coefficients and different water vapor pressure profiles.</p> |
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| ISSN: | 1867-1381 1867-8548 |