DOI: 10.5061/dryad.mkkwh7189
title: Data from: L-band InSAR SWE retrievals over Northern Colorado

description: During the NASA SnowEx Time Series campaigns, NASA UAVSAR was tasked to
 acquire weekly to bi-weekly SAR imagery over the Never Summer Mountains
 and Medicine Bow Mountains of northern Colorado, near Cameron Pass. In
 2020, three InSAR pairs were collected spanning 12 February to 12 March,
 coinciding with 117 mm of snow water equivalent (SWE) accumulation at the
 Joe Wright SNOTEL station (ID = 551) or about 18% of peak SWE. In 2021,
 eight InSAR pairs were collected from 15 January to 22 March, coinciding
 with 282 mm of SWE accumulation at the SNOTEL station or about 48% of peak
 SWE. The UAVSAR flightline was ~40 km long with a swath width of 16 km.
 The primary flight heading was southeast (141°), with a secondary
 northwest heading (321°) flown when time allowed. To produce this dataset,
 we used the 141° heading for all InSAR pairs except the 27 January to 3
 February 2021 interval, which used the 321° heading. Associated NASA
 UAVSAR interferograms are archived with the Alaska Satellite Facility
 (Flight ID = Rocky Mountains NP, Colorado). This data set contains derived
 changes in SWE (ΔSWE), calculated using methods following Guneriussen et
 al. (2001), from the associated UAVSAR flights.
description: Detailed methods can be found in the associated publication
 (Bonnell et
 al., 2024). Changes in SWE (ΔSWE) were calculated following
 Guneriussen et al. (2001), which requires phase changes, local incidence
 angles, and relative permittivity. Phase changes were obtained from the
 UAVSAR unwrapped interferograms, local incidence angles were calculated in
 uavsar_pytools from the Copernicus DEM and UAVSAR look vectors, and relative permittivity was calculated from the mean snow surface density measured on snow accumulation boards. Finally, interferograms were calibrated to absoluate ΔSWE by subtracting the median difference between UAVSAR ΔSWE and ΔSWE calculated from a group of ground observations.
description: # Data from: L-band InSAR SWE retrievals over Northern Colorado
 [https://doi.org/10.5061/dryad.mkkwh7189](https://doi.org/10.5061/dryad.mkkwh7189) ## Description of the data and file structure Data products contain SWE-changes from NASA UAVSAR flights during the SnowEx 2020 and 2021 Time Series Campaigns. Products are continuous from 12 February to 12 March 2020. The 2021 products are continuous from 15 January to 10 March. The 10–16 March unwrapped InSAR pair yielded no coincident data for phase calibration and thus was not included here. The final interval for 2021 is 16–22 March. The products have not been atmospherically corrected because it was determined in the manuscript ([https://doi.org/10.5194/egusphere-2024-236](https://doi.org/10.5194/egusphere-2024-236)) that an atmospheric correction was not warranted. These products are analysis ready. Most SWE-change products have a temporal baseline of 5–8 days. However, two intervals were longer and may have higher uncertainty: 26 February to 12 March 2020 and 3–23 February 2021. Some files may be missing data due to phase unwrapping errors. See NASA UAVSAR for phase unwrapping methodology. File Naming Convention: Date1_Date2_YYYY_Polarization_Heading.tif * Date1: The first UAVSAR flight date for the InSAR interval. * Date2: The second UAVSAR flight date for the InSAR interval. * YYYY: The year the pair of UAVSAR flights took place. * Polarization: Two digit letter code describing the transmitting and receiving polarization. * HH: Horizontally transmitted/Horizontally received * HV: Horizontally transmitted/Vertically received * VH: Vertically transmitted/Horizontally received * VV: Vertically transmitted/Vertically received * Heading: Three digit number code for the UAVSAR flight heading. For this dataset, the primary flight heading is northeast (141) and the secondary flight heading is southwest (321). * .tif: These files are provided as geotiffs. Coordinate System: * All geotiffs are provided in WGS84 (EPSG:4326). This was the original coordinate system provided by NASA UAVSAR. ## Sharing/Access information This dataset contains changes in snow water equivalent (SWE) derived from the NASA UAVSAR Rocky Mountains NP, CO flight line. Original unwrapped InSAR pairs are archived with NASA UAVSAR and the Alaska Satellite Facility Distributed Active Archive Center. The SLC files can be found at NASA UAVSAR: * [https://uavsar.jpl.nasa.gov/cgi-bin/product.pl?jobName=rockmt_14107_01#data](https://uavsar.jpl.nasa.gov/cgi-bin/product.pl?jobName=rockmt_14107_01#data) * [https://uavsar.jpl.nasa.gov/cgi-bin/product.pl?jobName=rockmt_32109_02#data](https://uavsar.jpl.nasa.gov/cgi-bin/product.pl?jobName=rockmt_32109_02#data) UAVSAR unwrapped InSAR pairs were converted to SWE-change rasters following methods outlined by Guneriussen et al. (2001): * [https://doi.org/10.1109/36.957273](https://doi.org/10.1109/36.957273) The Guneriussen et al. (2001) method requires phase change (the unwrapped InSAR pairs referenced previously), relative permittivity, local incidence angles, snow surface densities, and phase calibration: * Relative permittivity was calculated from snow surface densities using the empirical equation from Kovacs et al. (1995):  * [https://doi.org/10.1016/0165-232X(94)00016-Q](https://doi.org/10.1016/0165-232X\(94\)00016-Q) * Snow surface densities were measured in situ during the NASA SnowEx Time Series Campaigns: * 2020: [https://doi.org/10.5067/POT9E0FFUUD1%0d](https://doi.org/10.5067/POT9E0FFUUD1%0d) * 2021: [https://doi.org/10.5067/QIANJYJGRWOV](https://doi.org/10.5067/QIANJYJGRWOV) * Local incidence angles were calculated from the UAVSAR look vectors (see SLC stacks above) and the Copernicus 30 m DEM (downsampled to ~5m) within uavsar_pytools: * [https://doi.org/10.5281/zenodo.6789624](https://doi.org/10.5281/zenodo.6789624) * Phase calibration was computed as the median difference between a subset of ground-penetrating radar measurements of SWE-change and UAVSAR SWE-change. Ground-penetrating radar datasets are archived here: * 2020: [https://doi.org/10.5067/U4Q3X27BMRR4](https://doi.org/10.5067/U4Q3X27BMRR4) * 2021: [https://doi.org/10.5067/SRWGLYCB6ZC4](https://doi.org/10.5067/SRWGLYCB6ZC4)