{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:36:41Z","timestamp":1760240201001,"version":"build-2065373602"},"reference-count":30,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2019,3,28]],"date-time":"2019-03-28T00:00:00Z","timestamp":1553731200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"the National Key R&amp;D Program of China","award":["2016YFC1401005"],"award-info":[{"award-number":["2016YFC1401005"]}]},{"name":"the National Science Foundation of China","award":["61501130"],"award-info":[{"award-number":["61501130"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The co-located normalized radar backscatter cross section measurements from the Global Precipitation Measurement (GPM) Ku\/Ka-band dual-frequency precipitation radar (DPR) and sea surface wind; wave and temperature observations from the National Data Buoy Center (NDBC) moored buoys are used to analyze the dependence and sensitivity of Ku- and Ka-band backscatter on surface conditions at low-incidence angles. Then the potential for inverting wind and wave parameters directly from low-incidence \u03c30 measurements is discussed. The results show that the KaPR \u03c30 is more sensitive to surface conditions than the KuPR \u03c30 overall. Nevertheless; both the KuPR \u03c30 and KaPR \u03c30 are strongly correlated with wind speed (U10) and average wave steepness (\u03b4a) with the exception of specific transitional incidence angles. Moreover, U10 and \u03b4a could be retrieved from pointwise \u03c30 near nadir and near 18\u00b0. Near 18\u00b0; wind direction information is needed as the effect of wind direction on \u03c30 becomes increasingly significant with incidence angle. To improve the performance of U10 retrieval; especially for low U10; auxiliary \u03b4a information would be most helpful; and sea surface temperature is better taken into account. Other wave parameters; such as significant wave height; wave period and wave age; are partly correlated with \u03c30. It is generally more difficult to retrieve those parameters directly from pointwise \u03c30. For the retrieval of those wave parameters; various auxiliary information is needed. Wind direction and wave direction cannot be retrieved from pointwise \u03c30.<\/jats:p>","DOI":"10.3390\/rs11070754","type":"journal-article","created":{"date-parts":[[2019,3,29]],"date-time":"2019-03-29T03:38:52Z","timestamp":1553830732000},"page":"754","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":19,"title":["Analysis of Ku- and Ka-Band Sea Surface Backscattering Characteristics at Low-Incidence Angles Based on the GPM Dual-Frequency Precipitation Radar Measurements"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9185-3743","authenticated-orcid":false,"given":"Qiushuang","family":"Yan","sequence":"first","affiliation":[{"name":"First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China"},{"name":"School of Earth Science and Technology, China University of Petroleum, Qingdao 266580, China"}]},{"given":"Jie","family":"Zhang","sequence":"additional","affiliation":[{"name":"First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China"},{"name":"Oceanic telemetry Engineering and Technology Research Center, Ministry of Natural Resources, Qingdao 266061, China"},{"name":"School of Earth Science and Technology, China University of Petroleum, Qingdao 266580, China"}]},{"given":"Chenqing","family":"Fan","sequence":"additional","affiliation":[{"name":"First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China"},{"name":"Oceanic telemetry Engineering and Technology Research Center, Ministry of Natural Resources, Qingdao 266061, China"}]},{"given":"Junmin","family":"Meng","sequence":"additional","affiliation":[{"name":"First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China"},{"name":"Oceanic telemetry Engineering and Technology Research Center, Ministry of Natural Resources, Qingdao 266061, China"}]}],"member":"1968","published-online":{"date-parts":[[2019,3,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"549","DOI":"10.1175\/1520-0426(2003)20<549:TRBWSR>2.0.CO;2","article-title":"The relationship between winds, surface roughness, and radar backscatter at low incidence angles from TRMM precipitation radar measurements","volume":"20","author":"Freilich","year":"2003","journal-title":"J. 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