{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,24]],"date-time":"2025-11-24T16:41:26Z","timestamp":1764002486363,"version":"build-2065373602"},"reference-count":32,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2021,11,25]],"date-time":"2021-11-25T00:00:00Z","timestamp":1637798400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41906153"],"award-info":[{"award-number":["41906153"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The Chinese HY-2D satellite was launched on 19 May 2021, carrying a Ku-band scatterometer. Together with the operating scatterometers onboard the HY-2B and HY-2C satellites, the HY-2 series scatterometer constellation was built, constituting different satellite orbits and hence opportunity for mutual intercomparison and intercalibration. To achieve intercalibration of backscatter measurements for these scatterometers, this study presents and performs three methods including: (1) direct comparison using collocated measurements, in which the nonlinear calibrations can also be derived; (2) intercalibration over the Amazon rainforest; (3) and the double-difference technique based on backscatter simulations over the global oceans, in which a geophysical model function and numerical weather prediction (NWP) model winds are needed. The results obtained using the three methods are comparable, i.e., the differences among them are within 0.1 dB. The intercalibration results are validated by comparing the HY-2 series scatterometer wind speeds with NWP model wind speeds. The curves of wind speed bias for the HY-2 series scatterometers are quite similar, particularly in wind speeds ranging from 4 to 20 m\/s. Based on the well-intercalibrated backscatter measurements, consistent sea surface wind products from HY-2 series scatterometers can be produced, and greatly benefit data applications.<\/jats:p>","DOI":"10.3390\/rs13234783","type":"journal-article","created":{"date-parts":[[2021,12,1]],"date-time":"2021-12-01T01:45:02Z","timestamp":1638323102000},"page":"4783","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Intercalibration of Backscatter Measurements among Ku-Band Scatterometers Onboard the Chinese HY-2 Satellite Constellation"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1672-2705","authenticated-orcid":false,"given":"Zhixiong","family":"Wang","sequence":"first","affiliation":[{"name":"School of Marine Sciences, Nanjing University of Information Science and Technology, Nanjing 210044, China"},{"name":"Laboratory for Regional Oceanography and Numerical Modeling, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266000, China"}]},{"given":"Juhong","family":"Zou","sequence":"additional","affiliation":[{"name":"National Satellite Ocean Application Service, Beijing 100081, China"},{"name":"Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou 511458, China"}]},{"given":"Youguang","family":"Zhang","sequence":"additional","affiliation":[{"name":"National Satellite Ocean Application Service, Beijing 100081, China"},{"name":"Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou 511458, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4018-4073","authenticated-orcid":false,"given":"Ad","family":"Stoffelen","sequence":"additional","affiliation":[{"name":"Royal Netherlands Meteorological Institute, 3730 AE De Bilt, The Netherlands"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6455-4630","authenticated-orcid":false,"given":"Wenming","family":"Lin","sequence":"additional","affiliation":[{"name":"School of Marine Sciences, Nanjing University of Information Science and Technology, Nanjing 210044, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1531-5262","authenticated-orcid":false,"given":"Yijun","family":"He","sequence":"additional","affiliation":[{"name":"School of Marine Sciences, Nanjing University of Information Science and Technology, Nanjing 210044, China"}]},{"given":"Qian","family":"Feng","sequence":"additional","affiliation":[{"name":"National Satellite Ocean Application Service, Beijing 100081, China"}]},{"given":"Yi","family":"Zhang","sequence":"additional","affiliation":[{"name":"National Satellite Ocean Application Service, Beijing 100081, China"}]},{"given":"Bo","family":"Mu","sequence":"additional","affiliation":[{"name":"National Satellite Ocean Application Service, Beijing 100081, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5468-1591","authenticated-orcid":false,"given":"Mingsen","family":"Lin","sequence":"additional","affiliation":[{"name":"National Satellite Ocean Application Service, Beijing 100081, China"}]}],"member":"1968","published-online":{"date-parts":[[2021,11,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"4281","DOI":"10.1109\/TGRS.2013.2281056","article-title":"A decade of QuikSCAT scatterometer sea ice extent data","volume":"52","author":"Remund","year":"2013","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2941","DOI":"10.5194\/tc-12-2941-2018","article-title":"A scatterometer record of sea ice extents and backscatter: 1992\u20132016","volume":"12","author":"Otosaka","year":"2018","journal-title":"Cryosphere"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Li, M., Zhao, C., Zhao, Y., Wang, Z., and Shi, L. (2016). Polar sea ice monitoring using HY-2A scatterometer measurements. Remote Sens., 8.","DOI":"10.3390\/rs8080688"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2519","DOI":"10.1175\/JHM-D-15-0046.1","article-title":"Exploiting over-land OceanSat-2 scatterometer observations to capture short-period time-integrated precipitation","volume":"16","author":"Turk","year":"2015","journal-title":"J. Hydrometeorol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"533","DOI":"10.1109\/JSTARS.2015.2508065","article-title":"Remote sensing of terrestrial rainfall from Ku-band scatterometers","volume":"9","author":"Brocca","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1023\/A:1015832919110","article-title":"Progress in scatterometer application","volume":"58","author":"Liu","year":"2002","journal-title":"J. Oceanogr."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1829","DOI":"10.1175\/JTECH-D-15-0008.1","article-title":"A scatterometer geophysical model function for climate-quality winds: QuikSCAT Ku-2011","volume":"32","author":"Ricciardulli","year":"2015","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2123","DOI":"10.1109\/JSTARS.2017.2681806","article-title":"The CMOD7 geophysical model function for ASCAT and ERS wind retrievals","volume":"10","author":"Stoffelen","year":"2017","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1016\/j.rse.2019.03.005","article-title":"Inconsistencies in scatterometer wind products based on ASCAT and OSCAT-2 collocations","volume":"225","author":"Wang","year":"2019","journal-title":"Remote Sens. Environ."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"4387","DOI":"10.1109\/TGRS.2019.2963690","article-title":"Validation of new sea surface wind products from Scatterometers Onboard the HY-2B and MetOp-C satellites","volume":"58","author":"Wang","year":"2020","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"2135","DOI":"10.1109\/JSTARS.2016.2600749","article-title":"SST dependence of Ku-and C-band backscatter measurements","volume":"10","author":"Wang","year":"2017","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"6156","DOI":"10.1109\/JSTARS.2021.3087742","article-title":"Scatterometer Sea Surface Wind Product Validation for HY-2C","volume":"14","author":"Wang","year":"2021","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"923","DOI":"10.1109\/LGRS.2019.2940384","article-title":"Evaluating Chinese HY-2B HSCAT ocean wind products using buoys and other scatterometers","volume":"17","author":"Wang","year":"2019","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1478","DOI":"10.1109\/TGRS.2012.2217381","article-title":"C-band satellite scatterometer intercalibration","volume":"51","author":"Elyouncha","year":"2012","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2232","DOI":"10.1109\/JSTARS.2016.2639784","article-title":"Validation and cross-validation methods for ASCAT","volume":"10","author":"Anderson","year":"2017","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2195","DOI":"10.1109\/JSTARS.2017.2647842","article-title":"Cone metrics: A new tool for the intercomparison of scatterometer records","volume":"10","author":"Rivas","year":"2017","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"3393","DOI":"10.1109\/TGRS.2013.2272738","article-title":"Cross calibration of the OceanSAT-2 scatterometer with QuikSCAT scatterometer using natural terrestrial targets","volume":"52","author":"Bhowmick","year":"2013","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Zec, J., Jones, W.L., Alsabah, R., and Al-Sabbagh, A. (2017). RapidScat cross-calibration using the double difference technique. Remote Sens., 9.","DOI":"10.3390\/rs9111160"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2846","DOI":"10.1109\/TGRS.2015.2506463","article-title":"Calibration and validation of the RapidScat scatterometer using tropical rainforests","volume":"54","author":"Madsen","year":"2015","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"275","DOI":"10.1175\/1520-0426(1999)016<0275:ASMFCO>2.0.CO;2","article-title":"A simple method for calibration of a scatterometer over the ocean","volume":"16","author":"Stoffelen","year":"1999","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"2340","DOI":"10.1109\/JSTARS.2017.2685242","article-title":"Improved use of scatterometer measurements by using stress-equivalent reference winds","volume":"10","author":"Stoffelen","year":"2017","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"182","DOI":"10.1109\/LGRS.2004.842468","article-title":"Calibrating SeaWinds and QuikSCAT scatterometers using natural land targets","volume":"2","author":"Kunz","year":"2005","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Zhu, D., Zhang, L., Dong, X., Yun, R., and Lin, W. (August, January 28). Preliminary calibrations of the CFOSAT scatterometer. Proceedings of the 2019 IEEE International Geoscience and Remote Sensing Symposium, Yokohama, Japan.","DOI":"10.1109\/IGARSS.2019.8898712"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1127","DOI":"10.1109\/TGRS.2004.825589","article-title":"Diurnal change of Amazon rain forest\/spl sigma\/\/sup 0\/observed by Ku-band spaceborne radar","volume":"42","author":"Satake","year":"2004","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"6841","DOI":"10.1002\/2017GL073747","article-title":"Water stress detection in the Amazon using radar","volume":"44","author":"Paget","year":"2017","journal-title":"Geophys. Res. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"4383","DOI":"10.1109\/TGRS.2013.2281722","article-title":"Trends and variation in Ku-band backscatter of natural targets on land observed in QuikSCAT data","volume":"52","author":"Jaruwatanadilok","year":"2013","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_27","unstructured":"KNMI (2021, September 26). NSCAT-4 Geophysical Model Function. Available online: https:\/\/scatterometer.knmi.nl\/nscat4_gmf\/."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1171","DOI":"10.1175\/1520-0426(2001)018<1171:RDAQCO>2.0.CO;2","article-title":"Rain detection and quality control of SeaWinds","volume":"18","author":"Portabella","year":"2001","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_29","unstructured":"Stoffelen, A., and Vogelzang, J. (2021, November 08). Wind Bias Correction Guide. Document SAF\/OSI\/CDOP3\/KNMI\/SCI\/GUI\/390, NWPSAF-KN-UD-007, Version 1.5, 18-01-2021, KNMI, The Netherlands. Available online: https:\/\/nwp-saf.eumetsat.int\/site\/download\/documentation\/scatterometer\/Wind_Bias_Correction_Guide_v1.5.pdf."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"368","DOI":"10.1175\/2008JTECHO578.1","article-title":"On scatterometer ocean stress","volume":"26","author":"Portabella","year":"2009","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"2494","DOI":"10.1109\/TGRS.2019.2951726","article-title":"Improved rain screening for ku-band wind scatterometry","volume":"58","author":"Xu","year":"2019","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"831","DOI":"10.5194\/os-15-831-2019","article-title":"Characterizing ERA-Interim and ERA5 surface wind biases using ASCAT","volume":"15","author":"Stoffelen","year":"2019","journal-title":"Ocean Sci."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/23\/4783\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:35:57Z","timestamp":1760168157000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/23\/4783"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,11,25]]},"references-count":32,"journal-issue":{"issue":"23","published-online":{"date-parts":[[2021,12]]}},"alternative-id":["rs13234783"],"URL":"https:\/\/doi.org\/10.3390\/rs13234783","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2021,11,25]]}}}