{"id":53521,"date":"2023-07-18T08:30:00","date_gmt":"2023-07-18T08:30:00","guid":{"rendered":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/?p=53521"},"modified":"2023-07-18T18:01:15","modified_gmt":"2023-07-18T18:01:15","slug":"sar-winds-over-american-samoa-waters","status":"publish","type":"post","link":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/archives\/53521","title":{"rendered":"SAR Winds over American Samoa waters"},"content":{"rendered":"\n<figure class=\"wp-block-video\"><video height=\"810\" style=\"aspect-ratio: 1344 \/ 810;\" width=\"1344\" controls loop src=\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/goeswest_abi_radf_true_color_night_s20230718040022_e20230718073022_f22.mp4\"><\/video><figcaption class=\"wp-element-caption\">Visible (daytime) and Night Microphysics (nighttime) from 0400 to 0730 UTC on 18 July 2023<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">GOES-18 data above show persistent convection around Samoa and American Samoa between 0400 and 0730 UTC.  Sentinel-1A overflew the region just after 0550 UTC, yielding information about wind features.  At that time, a convective storm was developing in between Tutuila and Upolu.  The animation below steps through the Band 13 (Clean window infrared, 10.3 \u00b5m) imagery, with a toggle that <a href=\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/G18Band13SARWinds-20230718_055022.png\">includes the SAR winds<\/a>.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><a href=\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/G18Band13-20230718_0500_to_0620anim2.gif\"><img loading=\"lazy\" decoding=\"async\" width=\"1313\" height=\"902\" src=\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/G18Band13-20230718_0500_to_0620anim2.gif\" alt=\"\" class=\"wp-image-53525\"\/><\/a><figcaption class=\"wp-element-caption\">GOES-18 Clean Window Infrared (Band 13, 10.3 \u00b5m) near the islands of Tutuila (right) and Opolu (left), 0500 to 0620 UTC 18 July 2023.  SAR Winds at 0552 UTC are also shown.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p class=\"wp-block-paragraph\">SAR detected strong winds under the convection &#8212; up to about 30 knots.  The toggle below compares <a href=\"https:\/\/www.star.nesdis.noaa.gov\/socd\/mecb\/sar\/AKDEMO_products\/APL_winds\/wind_images2\/2023-07\/S1A_ESA_2023_07_18_05_52_40_0742974760_171.19W_13.79S_VV_C5_GFS025CDF_wind.png\">winds<\/a> and <a href=\"https:\/\/www.star.nesdis.noaa.gov\/socd\/mecb\/sar\/AKDEMO_products\/APL_winds\/wind_images2\/2023-07\/S1A_ESA_2023_07_18_05_52_40_0742974760_171.19W_13.79S_VV_C_nrcs.png\">Normalized Radar Cross Section<\/a> fields taken from <a href=\"https:\/\/www.star.nesdis.noaa.gov\/socd\/mecb\/sar\/AKDEMO_products\/APL_winds\/wind_images2\/sarwinds_daily_rcs.html\">this website<\/a>.  Past SAR blog posts at this site have suggested that SAR winds are diagnosed too high in regions where significant ice is present in a convective cloud &#8211; because of reflection of the SAR Radar signal off that ice back to the satellite.  A recent paper (<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0034425720305502\">link<\/a>) suggests that the enhanced backscatter arises not from the ice, but from scattering from wobbling, non-spherical, oblate hydrometeors within the melting layer.  That is, the cloud ice is necessary, but the signal arises only when the ice enters the melting layer.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><a href=\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/S1A_ESA_2023_07_18_05_52_40_0742974760_171.19W_13.79S_VV_C_nrcs_wind_toggle.gif\"><img loading=\"lazy\" decoding=\"async\" width=\"2030\" height=\"1800\" src=\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/S1A_ESA_2023_07_18_05_52_40_0742974760_171.19W_13.79S_VV_C_nrcs_wind_toggle.gif\" alt=\"\" class=\"wp-image-53529\"\/><\/a><figcaption class=\"wp-element-caption\">SAR Derived winds and Normalized Radar Cross Setion, 0552 UTC, 18 July 2023 (click to enlarge)<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p class=\"wp-block-paragraph\">Wave observations from the <a href=\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/AunuuBuoySite_PACIOOS.png\">Aunuu buoy<\/a> (available <a href=\"http:\/\/www.pacioos.hawaii.edu\/waves-category\/buoy\/\">at this website<\/a>), below, show waveheights decreasing during the time of the convective development above (which was, after all, far removed from the buoy site).<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"640\" src=\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/WaveInformationAunuu_17july2023-1024x640.png\" alt=\"\" class=\"wp-image-53532\" srcset=\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/WaveInformationAunuu_17july2023-1024x640.png 1024w, https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/WaveInformationAunuu_17july2023-300x187.png 300w, https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/WaveInformationAunuu_17july2023-768x480.png 768w, https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2023\/07\/WaveInformationAunuu_17july2023.png 1124w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Wave information from the Aunuu buoy site east of Tutuila (Click to enlarge);  note that 17:00 on 17 July is 0600 UTC 18 July<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>GOES-18 data above show persistent convection around Samoa and American Samoa between 0400 and 0730 UTC. Sentinel-1A overflew the region just after 0550 UTC, yielding information about wind features. At that time, a convective storm was developing in between Tutuila and Upolu. The animation below steps through the Band 13 (Clean window infrared, 10.3 \u00b5m) [&hellip;]<\/p>\n","protected":false},"author":19,"featured_media":53526,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[114,104,25],"tags":[],"class_list":["post-53521","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-goes-18","category-sar","category-satellite-winds"],"acf":[],"_links":{"self":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/53521","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/users\/19"}],"replies":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/comments?post=53521"}],"version-history":[{"count":5,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/53521\/revisions"}],"predecessor-version":[{"id":53535,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/53521\/revisions\/53535"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media\/53526"}],"wp:attachment":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media?parent=53521"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/categories?post=53521"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/tags?post=53521"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}