{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,20]],"date-time":"2025-10-20T10:29:49Z","timestamp":1760956189421,"version":"build-2065373602"},"reference-count":27,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2022,11,2]],"date-time":"2022-11-02T00:00:00Z","timestamp":1667347200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Over the horizon radars (OTHR) rely on the propagation of high frequency (HF) radio waves via the ionosphere to successfully achieve their designated missions. Backscatter sounders (BSS) are environmental over-the-horizon radars which may be used to assess the ionospheric propagation conditions. However, high power observed by a BSS may be due to either good ionospheric propagation, a high surface backscatter coefficient, or a combination of both. Hence, an understanding of the surface backscatter coefficients and their temporal variation is essential to fully understand the ionospheric propagation conditions. A database of surface backscatter coefficients over a decade was created using backscatter ionogram data from four backscatter sounders in Australia. The temporal variations in the backscatter coefficients were investigated and it was found that the land backscatter coefficients were relatively constant over time, while the sea backscatter coefficients showed significant seasonal variation.<\/jats:p>","DOI":"10.3390\/rs14215514","type":"journal-article","created":{"date-parts":[[2022,11,2]],"date-time":"2022-11-02T03:36:44Z","timestamp":1667360204000},"page":"5514","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Seasonal Variation in Land and Sea Surface Backscatter Coefficients at High Frequencies"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0376-4511","authenticated-orcid":false,"given":"Danielle","family":"Edwards","sequence":"first","affiliation":[{"name":"Defence Science and Technology Group, Edinburgh 5111, Australia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6011-016X","authenticated-orcid":false,"given":"Manuel","family":"Cervera","sequence":"additional","affiliation":[{"name":"Defence Science and Technology Group, Edinburgh 5111, Australia"},{"name":"School of Physical Sciences, The University of Adelaide, Adelaide 5005, Australia"}]}],"member":"1968","published-online":{"date-parts":[[2022,11,2]]},"reference":[{"key":"ref_1","unstructured":"Norman, R.J., Parkinson, M.L., and Dyson, P.L. (2004). Comparing HF radar backscatter from the Southern Ocean with ray-tracing results using the IRI model. Proceedings of the Workshop on the Applications of Radio Science, Hobart, Tasmania, National Committee for Radio Science."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"5819","DOI":"10.1109\/TAP.2022.3161534","article-title":"High Frequency Land Backscatter Coefficients over Northern Australia and the Effects of Various Surface Properties","volume":"70","author":"Edwards","year":"2022","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"81","DOI":"10.1029\/RS021i001p00081","article-title":"Extraction of sea state from HF radar sea echo: Mathematical theory and modeling","volume":"21","author":"Lipa","year":"1986","journal-title":"Radio Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"865","DOI":"10.1002\/rds196838865","article-title":"A Review of Scattering From Surfaces with Different Roughness Scales","volume":"3","author":"Barrick","year":"1968","journal-title":"Radio Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1109\/8.655453","article-title":"Grazing behavior of scatter and propagation above any rough surface","volume":"46","author":"Barrick","year":"1998","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"897","DOI":"10.1029\/RS007i010p00897","article-title":"A Practical Evaluation of Earth-Backscatter Simulation and an Estimate of the HF Ground-Scatter Coefficient","volume":"7","author":"Althouse","year":"1972","journal-title":"Radio Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1583","DOI":"10.1109\/PROC.1967.5910","article-title":"High-frequency backscatter from terrain with trees","volume":"55","author":"Steele","year":"1967","journal-title":"Proc. IEEE"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1029\/RS007i002p00239","article-title":"Ground Backscatter Observed with High Resolution Oblique Sounders","volume":"7","author":"Balser","year":"1972","journal-title":"Radio Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"343","DOI":"10.1109\/TAP.1971.1139934","article-title":"High-frequency backscatter from terrain with cement-block walls","volume":"19","author":"Barnum","year":"1971","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Holdsworth, D.A. (2017, January 8\u201312). Skywave over-the-horizon radar track registration using earth surface and infrastructure backscatter. Proceedings of the IEEE Radar Conference, Seattle, WA, USA.","DOI":"10.1109\/RADAR.2017.7944347"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1077","DOI":"10.1029\/98RS00831","article-title":"Over-the-horizon radar target registration improvement by terrain feature localization","volume":"33","author":"Barnum","year":"1998","journal-title":"Radio Sci."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"81","DOI":"10.1016\/0011-7471(68)90029-6","article-title":"Observations of coherent backscatter of 2\u201310 MHz radio surface waves from the sea","volume":"15","author":"Crombie","year":"1968","journal-title":"Deep-Sea Res. Oceanogr. Abstr."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2","DOI":"10.1109\/TAP.1972.1140123","article-title":"First-order theory and analysis of MF\/HF\/VHF scatter from the sea","volume":"20","author":"Barrick","year":"1972","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Yingwei, T., Biyang, W., Hao, Z., Caijun, W., Jing, Y., and Weimin, H. (2017). Wave Height Estimation from First-Order Backscatter of a Dual-Frequency High Frequency Radar. Remote Sens., 9.","DOI":"10.3390\/rs9111186"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Edwards, D., Cervera, M., and MacKinnon, A. (2022). A Comparison of the Barrick and Backscatter Ionogram Methods of Calculating Sea Surface Backscatter Coefficients. Remote Sens., 14.","DOI":"10.3390\/rs14092139"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1186\/s40623-015-0378-9","article-title":"Diurnal and seasonal behavior of the Hokkaido East SuperDARN ground backscatter: Simulation and observation","volume":"68","author":"Oinats","year":"2016","journal-title":"Earth Planets Space"},{"key":"ref_17","unstructured":"Gardiner-Garden, R.S., and Pincombe, A.H. (1996). A Study of the Seasonal Pattern of Variability in the HF Radar Cross-Section of the Sea, Intelligence, Surveillance and Space Division, DST Group. DSTO-DPP-0261."},{"key":"ref_18","unstructured":"Cameron, A. (1995, January 8\u201311). The Jindalee operational radar network: Its architecture and surveillance capability. Proceedings of the International Radar Conference, Alexandria, VA, USA."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Holdsworth, D.A., Mulder, K., and Turley, M.D.E. (2022, January 21\u201325). Jindalee Operational Radar Network: New Growth from Old Roots. Proceedings of the IEEE Radar Conference (RadarConf22), New York City, NY, USA.","DOI":"10.1109\/RadarConf2248738.2022.9764214"},{"key":"ref_20","first-page":"122","article-title":"Real time ionospheric models for the Australian Defence Force","volume":"122135","author":"Barnes","year":"2000","journal-title":"Proc. WARS-2000"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"563","DOI":"10.1002\/2015RS005881","article-title":"The DST group ionospheric sounder replacement for JORN","volume":"51","author":"Harris","year":"2016","journal-title":"Radio Sci."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"431","DOI":"10.1002\/2013JA019247","article-title":"Modeling ionospheric disturbance features in quasi-vertically incident ionograms using 3-D magnetoionic ray tracing and atmospheric gravity waves","volume":"119","author":"Cervera","year":"2014","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_23","first-page":"307","article-title":"A new method of predicting the ionospheric absorption of high frequency waves at oblique incidence","volume":"41","author":"George","year":"1974","journal-title":"Telecommun. J."},{"key":"ref_24","unstructured":"Burke, G., Poggio, A., Logan, J., and Rockway, J. (1979, January 18\u201322). NEC\u2014Numerical electromagnetics code for antennas and scattering. Proceedings of the Antennas and Propagation Society International Symposium, Seatlle, WA, USA."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"e2021JC017198","DOI":"10.1029\/2021JC017198","article-title":"The Seasonal Cycle of Significant Wave Height in the Ocean: Local Versus Remote Forcing","volume":"126","author":"Colosi","year":"2021","journal-title":"J. Geophys. Res. Ocean."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"61","DOI":"10.1175\/1520-0477(1998)079<0061:APGTWA>2.0.CO;2","article-title":"A Practical Guide to Wavelet Analysis","volume":"79","author":"Torrence","year":"1998","journal-title":"Bull. Am. Meteorol. Soc."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"432","DOI":"10.2112\/JCR-SI50-083.1","article-title":"Waves and Climate Change on the Australian Coast","volume":"50","author":"Hemer","year":"2007","journal-title":"J. Coast. 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