{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T04:27:26Z","timestamp":1772252846874,"version":"3.50.1"},"reference-count":29,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2023,5,17]],"date-time":"2023-05-17T00:00:00Z","timestamp":1684281600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000104","name":"NASA","doi-asserted-by":"publisher","award":["80NSSC18K156"],"award-info":[{"award-number":["80NSSC18K156"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"NASA","doi-asserted-by":"publisher","award":["80NSSC21K1963"],"award-info":[{"award-number":["80NSSC21K1963"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"NASA","doi-asserted-by":"publisher","award":["80NSSC22K0713"],"award-info":[{"award-number":["80NSSC22K0713"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"NASA Goddard Space Flight Center (GSFC)","doi-asserted-by":"publisher","award":["80NSSC18K156"],"award-info":[{"award-number":["80NSSC18K156"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"NASA Goddard Space Flight Center (GSFC)","doi-asserted-by":"publisher","award":["80NSSC21K1963"],"award-info":[{"award-number":["80NSSC21K1963"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"NASA Goddard Space Flight Center (GSFC)","doi-asserted-by":"publisher","award":["80NSSC22K0713"],"award-info":[{"award-number":["80NSSC22K0713"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Presented is a methodology to explicitly identify and account for cloud-free satellite measurements below a sensor\u2019s measurement detection level. These low signals can often be found in satellite observations of minor atmospheric species with weak spectral signals (e.g., ammonia (NH3)). Not accounting for these non-detects can high-bias averaged measurements in locations that exhibit conditions below the detection limit of the sensor. The approach taken here is to utilize the information content from the satellite signal to explicitly identify non-detects and then account for them with a consistent approach. The methodology is applied to the CrIS Fast Physical Retrieval (CFPR) ammonia product and results in a more realistic averaged dataset under conditions where there are a significant number of non-detects. These results show that in larger emission source regions (i.e., surface values &gt; 7.5 ppbv) the non-detects occur less than 5% of the time and have a relatively small impact (decreases by less than 5%) on the gridded averaged values (e.g., annual ammonia source regions). However, in regions that have low ammonia concentration amounts (i.e., surface values &lt; 1 ppbv) the fraction of non-detects can be greater than 70%, and accounting for these values can decrease annual gridded averaged values by over 50% and make the distributions closer to what is expected based on surface station observations.<\/jats:p>","DOI":"10.3390\/rs15102610","type":"journal-article","created":{"date-parts":[[2023,5,18]],"date-time":"2023-05-18T06:32:58Z","timestamp":1684391578000},"page":"2610","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Accounting for Non-Detects: Application to Satellite Ammonia Observations"],"prefix":"10.3390","volume":"15","author":[{"given":"Evan","family":"White","sequence":"first","affiliation":[{"name":"Environment and Climate Change Canada, Toronto, ON M3H 5T4, Canada"},{"name":"Faculty of Science, University of Waterloo, Waterloo, ON N2L 3G1, Canada"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2867-9612","authenticated-orcid":false,"given":"Mark W.","family":"Shephard","sequence":"additional","affiliation":[{"name":"Environment and Climate Change Canada, Toronto, ON M3H 5T4, Canada"}]},{"given":"Karen E.","family":"Cady-Pereira","sequence":"additional","affiliation":[{"name":"Atmospheric and Environmental Research (AER), Inc., Lexington, MA 02421, USA"}]},{"given":"Shailesh K.","family":"Kharol","sequence":"additional","affiliation":[{"name":"Environment and Climate Change Canada, Toronto, ON M3H 5T4, Canada"},{"name":"Atmo Analytics Inc., Brampton, ON L6S 6L2, Canada"}]},{"given":"Sean","family":"Ford","sequence":"additional","affiliation":[{"name":"Environment and Climate Change Canada, Toronto, ON M3H 5T4, Canada"},{"name":"Faculty of Science, University of British Columbia, Vancouver, BC V6T 1Z4, Canada"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0128-8205","authenticated-orcid":false,"given":"Enrico","family":"Dammers","sequence":"additional","affiliation":[{"name":"TNO, Climate Air and Sustainability, 3584 CB Utrecht, The Netherlands"}]},{"given":"Evan","family":"Chow","sequence":"additional","affiliation":[{"name":"Environment and Climate Change Canada, Toronto, ON M3H 5T4, Canada"},{"name":"Faculty of Science, University of Waterloo, Waterloo, ON N2L 3G1, Canada"}]},{"given":"Nikolai","family":"Thiessen","sequence":"additional","affiliation":[{"name":"Environment and Climate Change Canada, Toronto, ON M3H 5T4, Canada"},{"name":"Faculty of Science, University of British Columbia, Vancouver, BC V6T 1Z4, Canada"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5408-2289","authenticated-orcid":false,"given":"David","family":"Tobin","sequence":"additional","affiliation":[{"name":"Space Science and Engineering Center (SSEC), University of Wisconsin-Madison, Madison, WI 53715, USA"}]},{"given":"Greg","family":"Quinn","sequence":"additional","affiliation":[{"name":"Space Science and Engineering Center (SSEC), University of Wisconsin-Madison, Madison, WI 53715, USA"}]},{"given":"Jason","family":"O\u2019Brien","sequence":"additional","affiliation":[{"name":"Environment and Climate Change Canada, Toronto, ON M3H 5T4, Canada"}]},{"given":"Jesse","family":"Bash","sequence":"additional","affiliation":[{"name":"US Environmental Protection Agency, Research Triangle Park, Durham, NC 27709, USA"}]}],"member":"1968","published-online":{"date-parts":[[2023,5,17]]},"reference":[{"key":"ref_1","first-page":"520","article-title":"Satellites Detect a Methane Ultra-emission Event from an Offshore Platform in the Gulf of Mexico","volume":"9","author":"Guanter","year":"2022","journal-title":"Environ. 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