{"id":11355,"date":"2012-09-19T20:33:42","date_gmt":"2012-09-19T20:33:42","guid":{"rendered":"http:\/\/cimss.ssec.wisc.edu\/satellite-blog\/?p=11355"},"modified":"2012-09-21T15:49:05","modified_gmt":"2012-09-21T15:49:05","slug":"noise-in-the-shortwave-goes-13-sounder-channels","status":"publish","type":"post","link":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/archives\/11355","title":{"rendered":"Noise in the Shortwave GOES-13 Sounder Channels"},"content":{"rendered":"
\"Multipanel<\/a>

Multipanel display of GOES-East Sounder Channels<\/p><\/div>\n

The shortwave infrared channels on the GOES-13 sounder have displayed increasing amounts of noise over the past months. The multi-channel display, above, shows distinct noise in the channels at 4.57 \u00c2\u00b5m, 4.53 \u00c2\u00b5m, 4.45 \u00c2\u00b5m and 4.13 \u00c2\u00b5m. Animations of the GOES-13\/GOES-15 imagery from AWIPS shows that the noise is far more obvious in the GOES-13 channel. It is especially noteworthy in the 4.45 \u00c2\u00b5m channel<\/a> (called the 4.5 \u00c2\u00b5m channel in AWIPS) but also readily apparent in the 4.13 \u00c2\u00b5m channel<\/a> (called the 4.0 \u00c2\u00b5m channel in AWIPS).<\/p>\n

Data from these noisy channels are used in the computation of derived products. The effect of the noise is manifest as small-scale noise in the derived fields of total precipitable water<\/a>, for example, and the bad data is most noticeable at night, because the shortwave data are used to identify cloudy pixels; during the day, visible imagery identifies cloudy pixels. Thus, maps of, for example, lifted index have too many pixels flagged as cloudy at night<\/a> compared to during the day<\/a>. Also compare the 0600 UTC Total Precipitable Water<\/a> (TPW) image to the 1900 UTC<\/a> image.<\/p>\n

\"Sounder<\/a>

Sounder Cloud-Top Pressure From GOES-13 and GOES-14 (click image to toggle between images)<\/p><\/div>\n

Because the shortwave data are used to identify cloudy pixels, night-time estimates of cloud-top pressure as also impacted, as shown above. The GOES-13 Sounder-derived cloud-top pressure<\/a> includes several regions that are indicated as cloudy because of the noisy shortwave data. A similar field derived from GOES-14<\/a> sounder data does not include the cloudy pixels. Data from 1800 UTC<\/a> — when visible imagery can be used to screen out clear pixels with more efficacy — shows less contamination that can be traced to the shortwave fields. That is, the fields derived from the GOES-13<\/a> and GOES-14<\/a> Sounder look more similar. <\/p>\n

NESDIS scientists are evaluating how the shortwave bands can be excluded from the GOES-13 Sounder computation to reduce night-time noise in the output fields. Real-time GOES Sounder imagery is available at this link<\/a>. Derived products, including Convective Available Potential Energy (CAPE), TPW, Lifted Index and cloud-top properties can also be viewed at that link.<\/p>\n

(Some imagery in this blog post courtesy of Tim Schmit, NOAA\/NESDIS)<\/p>\n

This plot<\/a>, courtesy of Mat Gunshor, CIMSS, shows the standard deviation of the difference between observed brightness temperature and forward-calculated brightness temperatuers. A big jump in noise occurred in late August.<\/p>\n","protected":false},"excerpt":{"rendered":"

The shortwave infrared channels on the GOES-13 sounder have displayed increasing amounts of noise over the past months. The multi-channel display, above, shows distinct noise in the channels at 4.57 \u00c2\u00b5m, 4.53 \u00c2\u00b5m, 4.45 \u00c2\u00b5m and 4.13 \u00c2\u00b5m. Animations of the GOES-13\/GOES-15 imagery from AWIPS shows that the noise is far more obvious in the […]<\/p>\n","protected":false},"author":19,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[50,11,40,43],"tags":[],"class_list":["post-11355","post","type-post","status-publish","format-standard","hentry","category-calibration","category-goes-13","category-goes-14","category-goes-15"],"acf":[],"_links":{"self":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/11355","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=11355"}],"version-history":[{"count":14,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/11355\/revisions"}],"predecessor-version":[{"id":11390,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/11355\/revisions\/11390"}],"wp:attachment":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media?parent=11355"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/categories?post=11355"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/tags?post=11355"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}