{"id":50095,"date":"2023-01-31T11:02:00","date_gmt":"2023-01-31T11:02:00","guid":{"rendered":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/?p=50095"},"modified":"2023-02-01T21:34:00","modified_gmt":"2023-02-01T21:34:00","slug":"sar-imagery-collection-near-american-samoa","status":"publish","type":"post","link":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/archives\/50095","title":{"rendered":"SAR Imagery collection near American Samoa"},"content":{"rendered":"\n
\"\"<\/a>
Derived Winds and Normalized Radar Cross Section from Sentinel 1A SAR, 0553 UTC on 31 January 2023 (Click to enlarge)<\/figcaption><\/figure>\n\n\n\n

SAR data are being acquired over American Samoa for the next several weeks. SAR data from a Sentinel-1A overpass at 0553 UTC on 31 January, shown above (from this website<\/a>), shows mostly light winds, mostly less than 10 m\/s. The Normalized Radar Cross Section (NRCS) data<\/a> can be used to view any ice contamination in the wind speed image.<\/a> Ice can cause very strong reflection of the SAR signal that will be misinterpreted as strong winds. If significant ice is present in any convective tower, it will have a feathery appearance in the NRCS data.<\/p>\n\n\n\n

SAR netcdf files can also be imported into AWIPS, and the toggle below compares GOES-18 Band 13 imagery and SAR data at the same time. On this day it is challenging to relate the small increases in wind apparent in the SAR imagery to Band 13 satellite imagery.<\/p>\n\n\n\n

\"\"<\/a>
GOES-18 Band 13 infrared imagery (10.3 \u00b5m) and Sentinel S1A SAR data, 0550 UTC on 31 January 2023 (Click to enlarge)<\/figcaption><\/figure>\n\n\n\n
\n\n\n\n

MetopB overflew the Samoan Islands shortly after 0900 UTC (link<\/a>), and Advanced Scatterometer (ASCAT) winds from that platform also show weak winds. MetopC<\/a> ASCAT winds from 0831 and 1011<\/a> UTC show light winds as well.<\/p>\n\n\n\n

\"\"<\/a>
MetopB ASCAT winds at 0919 UTC on 31 January 2023 (Click to enlarge)<\/figcaption><\/figure>\n\n\n\n

Thanks to the NOAA Office of Observations and NOAA\/NESDIS\/STAR SMCD and SOCD for arranging these observations.<\/p>\n\n\n\n

\n\n\n\n

The Special Collection actually started on 30 January<\/a>, and two RADARSAT collections occurred, one at 0544 (Wind Analaysis is here<\/a>; NRCS is here<\/a>) and one at 1647 UTC (Wind Analysis<\/a> ; NRCS<\/a>). Toggles of the two image pairs are shown below.<\/p>\n\n\n\n

\"\"<\/a>
RADARSAT SAR Normalized Radar Cross Section (NRCS) and derived wind speed, 0544 UTC, 30 January 2023 (Click to enlarge)<\/figcaption><\/figure>\n\n\n\n
\"\"
RADARSAT SAR Normalized Radar Cross Section (NRCS) and derived wind speed, 1647 UTC, 30 January 2023 (Click to enlarge)<\/figcaption><\/figure>\n\n\n\n

The 1647 UTC wind speed analysis includes regions where contamination by thick ice in clouds is likely occurring. That is, those very strong wind values (nearly 50 knots!) centered near 16.25 S and 171.5 W are not true surface winds speeds, but arise because of strong reflection from thick ice within convective clouds in that vicinity. (The ice features have a feathery look in the NRCS fields). GOES-18 Band 13 imagery over that region, below, shows abundant deep convection. The GOES-18 Cloud Phase product (here<\/a>) indicated ice clouds over the convection, but only within certain regions of the convection was the ice thick enough to reflect enough SAR radiation to affect the derived wind speeds.<\/p>\n\n\n\n

\"\"
GOES-18 ABI Band 13 clean window infrared (10.3 \u00b5m) imagery, 1650 UTC on 30 January 2023 (Click to enlarge)<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

SAR data are being acquired over American Samoa for the next several weeks. SAR data from a Sentinel-1A overpass at 0553 UTC on 31 January, shown above (from this website), shows mostly light winds, mostly less than 10 m\/s. The Normalized Radar Cross Section (NRCS) data can be used to view any ice contamination in […]<\/p>\n","protected":false},"author":19,"featured_media":50108,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[58,47,104,25],"tags":[],"class_list":["post-50095","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-metop","category-other-satellites","category-sar","category-satellite-winds"],"acf":[],"_links":{"self":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/50095","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=50095"}],"version-history":[{"count":6,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/50095\/revisions"}],"predecessor-version":[{"id":50136,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/50095\/revisions\/50136"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media\/50108"}],"wp:attachment":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media?parent=50095"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/categories?post=50095"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/tags?post=50095"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}