Ground mobile observation system for measuring multisurface microwave emissivity
<p>Large microwave surface emissivities with a highly heterogeneous distribution and the relatively small hydrometeor signal over land make it challenging to use satellite microwave data to retrieve precipitation and to be assimilated into numerical models. To better understand the microwave e...
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| Autores principales: | , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/17c1c8210a7a478296c1e0a68908f726 |
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| Sumario: | <p>Large microwave surface emissivities with a highly heterogeneous
distribution and the relatively small hydrometeor signal over land make it
challenging to use satellite microwave data to retrieve precipitation and to
be assimilated into numerical models. To better understand the microwave
emissivity over land surfaces, we designed and established a ground
observation system for the in situ observation of microwave emissivities
over several typical surfaces. The major components of the system include a
dual-frequency polarized ground microwave radiometer, a mobile observation
platform, and auxiliary sensors to measure the surface temperature and soil
temperature and moisture; moreover, observation fields are designed
comprising five different land surfaces.</p>
<p>Based on the observed data from the mobile system, we preliminarily
investigated the variations in the surface microwave emissivity over
different land surfaces. The results show that the horizontally polarized
emissivity is more sensitive to land surface variability than the
vertically polarized emissivity is: the former decreases to 0.75 over cement
and increases to 0.90 over sand and bare soil and up to 0.97 over grass. The
corresponding emissivity polarization difference is obvious over water
(<span class="inline-formula"><i>></i>0.3</span>) and cement (approximately 0.25) but reduces to 0.1 over
sand and 0.05 over bare soil and almost 0.01 or close to zero over grass;
this trend is similar to that of the <span class="inline-formula"><i>T</i><sub>b</sub></span> polarization difference. At
different elevation angles, the horizontally/vertically polarized
emissivities over land surfaces obviously increase/slightly decrease with
increasing elevation angles but exhibit the opposite trend over water.</p> |
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