{"id":50490,"date":"2023-02-16T20:16:12","date_gmt":"2023-02-16T20:16:12","guid":{"rendered":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/?p=50490"},"modified":"2023-02-20T21:40:35","modified_gmt":"2023-02-20T21:40:35","slug":"more-sar-data-over-cyclone-freddy-and-parallax","status":"publish","type":"post","link":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/archives\/50490","title":{"rendered":"More SAR data over Cyclone Freddy, and parallax"},"content":{"rendered":"\n
\"\"<\/a>
RADARSAT and RCM1 SAR Winds over Cyclone Freddy, 0004 and 0012 UTC on 16 February 2023 (Click to enlarge)<\/figcaption><\/figure>\n\n\n\n

RADARSAT-2 and RCM-1 had two closely-spaced overpasses over Cyclone Freddy in the Indian Ocean early on 16 February 2023, as shown above. Eyewall speeds exceed 130 knots in the RCM-1 data! (Imagery and data are available here<\/a>). The quadrant analyses for RCM-1<\/a> and for RADARSAT-2<\/a> show hurricane-force winds extending out about 40 nautical miles from the storm center. The toggle below shows 0000 UTC Himawari-9 clean window imagery overlain with the 0004 UTC RADARSAT-2 SAR Winds. Because Freddy now is almost at the limb of the Himawari-9 imagery (as shown here<\/a>), there is a noticeable parallax shift in the Himawari-9 clouds — away from the sub-satellite point (for Himawari-9, that’s at 140.7o<\/sup> E longitude<\/a>; Freddy was at 82.2o<\/sup> E Longitude!)<\/p>\n\n\n\n

\"\"<\/a>
Himawari-9 Clean Window infrared (10.4 \u00b5m) imagery and RADARSAT-2 SAR winds, 0000 UTC on 16 February 2023 (Click to enlarge)<\/figcaption><\/figure>\n\n\n\n

The toggle below compares 0000 UTC Clean Window imagery from Himawari-9 (AHI data) and from GEOKOMPSAT-2 (over the Equator at 128.2o<\/sup> E<\/a>) (AMI data). The parallax shift in the AMI data is smaller than with AHI because Freddy is closer to GEOKOMPSAT-2’s subsatellite point. (Himawari HSD and Geokompsat-2 Level 1b files were processed with geo2grid<\/a> software for these images). However, both satellites show an eye to the west of its SAR-derived location. Note also the degradation in Himawari-9 image acuity over the western part of the domain; brightness temperatures are also cooler over the western quarter of the domain, likely due to limb cooling (also discussed in this blog post<\/a>): radiation from the edge<\/em> of a Full-Disk scan (compared to radiation from the sub-satellite point) will pass through more of the colder upper troposphere (because of the much more slanted path towards the satellite) before reaching the satellite detectors, and a cooler temperature will be perceived.<\/p>\n\n\n\n

\"\"
Himawari-9 and Geokompsat-2 Clean Window infrared (10.4 \u00b5m and 10.5 \u00b5m, respectively) at 0000 UTC on 16 February 2023 (Click to enlarge)<\/figcaption><\/figure>\n\n\n\n

Earlier SAR captures of Freddy’s eye with comparisons to Himawari-9 imagery are available here<\/a>. Thanks to JMA<\/a> and KMA<\/a>s for the data!<\/p>\n\n\n\n

\n\n\n\n

The toggle below compares EWS-G1<\/a> infrared imagery (4-km resolution) with AHI data remapped to the EWS-G1 projection. Both satellites were sampling the eye near 0000 UTC on 16 February. EWS-G1 is over the equator near 66o<\/sup>E, so any eye displacement due to parallax will be to the east of the eye, i.e. in the opposite direction of the Himawari-9 parallax displacement.<\/p>\n\n\n\n

\"\"<\/a>
Clean window infrared Himawari-9 imagery (10.4 \u00b5m, remapped to the EWS-G1 projection) and EWS-G1 imagery (10.8 \u00b5m), ca. 0000 UTC on 16 February 2023 (Click to enlarge)<\/figcaption><\/figure>\n\n\n\n
\n\n\n\n

Cyclone Freddy was at its strongest at around 0000 UTC on 16 February, as noted here<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

RADARSAT-2 and RCM-1 had two closely-spaced overpasses over Cyclone Freddy in the Indian Ocean early on 16 February 2023, as shown above. Eyewall speeds exceed 130 knots in the RCM-1 data! (Imagery and data are available here). The quadrant analyses for RCM-1 and for RADARSAT-2 show hurricane-force winds extending out about 40 nautical miles from […]<\/p>\n","protected":false},"author":19,"featured_media":50495,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[92,82,73,104,25,2],"tags":[],"class_list":["post-50490","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ews-g1","category-gk2a","category-himawari-9","category-sar","category-satellite-winds","category-tropical-cyclones"],"acf":[],"_links":{"self":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/50490","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=50490"}],"version-history":[{"count":6,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/50490\/revisions"}],"predecessor-version":[{"id":50624,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/50490\/revisions\/50624"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media\/50495"}],"wp:attachment":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media?parent=50490"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/categories?post=50490"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/tags?post=50490"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}