{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,25]],"date-time":"2026-03-25T10:37:47Z","timestamp":1774435067819,"version":"3.50.1"},"reference-count":52,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2021,11,16]],"date-time":"2021-11-16T00:00:00Z","timestamp":1637020800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["80NSSC20K0921"],"award-info":[{"award-number":["80NSSC20K0921"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["80NSSC18K0877"],"award-info":[{"award-number":["80NSSC18K0877"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["1824152"],"award-info":[{"award-number":["1824152"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.mdpi.com"],"crossmark-restriction":true},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Extensive efforts have been made to observe the accumulation and melting of seasonal snow. However, making accurate observations of snow water equivalent (SWE) at global scales is challenging. Active radar systems show promise, provided the dielectric properties of the snowpack are accurately constrained. The dielectric constant (k) determines the velocity of a radar wave through snow, which is a critical component of time-of-flight radar techniques such as ground penetrating radar and interferometric synthetic aperture radar (InSAR). However, equations used to estimate k have been validated only for specific conditions with limited in situ validation for seasonal snow applications. The goal of this work was to further understand the dielectric permittivity of seasonal snow under both dry and wet conditions. We utilized extensive direct field observations of k, along with corresponding snow density and liquid water content (LWC) measurements. Data were collected in the Jemez Mountains, NM; Sandia Mountains, NM; Grand Mesa, CO; and Cameron Pass, CO from February 2020 to May 2021. We present empirical relationships based on 146 snow pits for dry snow conditions and 92 independent LWC observations in naturally melting snowpacks. Regression results had r2 values of 0.57 and 0.37 for dry and wet snow conditions, respectively. Our results in dry snow showed large differences between our in situ observations and commonly applied equations. We attribute these differences to assumptions in the shape of the snow grains that may not hold true for seasonal snow applications. Different assumptions, and thus different equations, may be necessary for varying snowpack conditions in different climates, suggesting that further testing is necessary. When considering wet snow, large differences were found between commonly applied equations and our in situ measurements. Many previous equations assume a background (dry snow) k that we found to be inaccurate, as previously stated, and is the primary driver of resulting uncertainty. Our results suggest large errors in SWE (10\u201315%) or LWC (0.05\u20130.07 volumetric LWC) estimates based on current equations. The work presented here could prove useful for making accurate observations of changes in SWE using future InSAR opportunities such as NISAR and ROSE-L.<\/jats:p>","DOI":"10.3390\/rs13224617","type":"journal-article","created":{"date-parts":[[2021,11,17]],"date-time":"2021-11-17T02:42:28Z","timestamp":1637116948000},"page":"4617","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":25,"title":["In Situ Determination of Dry and Wet Snow Permittivity: Improving Equations for Low Frequency Radar Applications"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1565-909X","authenticated-orcid":false,"given":"Ryan W.","family":"Webb","sequence":"first","affiliation":[{"name":"Center for Water and the Environment, University of New Mexico, Albuquerque, NM 87131, USA"},{"name":"Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO 80309, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Adrian","family":"Marziliano","sequence":"additional","affiliation":[{"name":"Center for Water and the Environment, University of New Mexico, Albuquerque, NM 87131, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9462-6842","authenticated-orcid":false,"given":"Daniel","family":"McGrath","sequence":"additional","affiliation":[{"name":"Department of Geosciences, Colorado State University, Fort Collins, CO 80523, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Randall","family":"Bonnell","sequence":"additional","affiliation":[{"name":"Department of Geosciences, Colorado State University, Fort Collins, CO 80523, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tate G.","family":"Meehan","sequence":"additional","affiliation":[{"name":"Department of Geoscience, Boise State University, Boise, ID 83706, USA"},{"name":"US Army Cold Regions Research and Engineering Laboratory, Hanover, NH 03755, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Carrie","family":"Vuyovich","sequence":"additional","affiliation":[{"name":"NASA-Goddard Space Flight Center, Greenbelt, MD 20770, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hans-Peter","family":"Marshall","sequence":"additional","affiliation":[{"name":"Department of Geoscience, Boise State University, Boise, ID 83706, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,11,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"303","DOI":"10.1038\/nature04141","article-title":"Potential impacts of a warming climate on water availability in snow-dominated regions","volume":"438","author":"Barnett","year":"2005","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"114016","DOI":"10.1088\/1748-9326\/10\/11\/114016","article-title":"The potential for snow to supply human water demand in the present and future","volume":"10","author":"Mankin","year":"2015","journal-title":"Environ. 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