DOI: 10.5061/dryad.x3ffbg7tg
title: L-band InSAR snow water equivalent retrievals over Fraser Experimental Forest, Colorado

description: The Fraser Experimental Forest, CO was one of seven sites in 2021 that
 received NASA UAVSAR flights during the SnowEx Time Series Campaign. Two
 flight headings (052° and 233°) were flown. Eight InSAR pairs were
 collected from 15 January to 22 March, with a typical temporal baseline of
 7 days from the 052° heading, whereas the 233° heading saw fewer flights
 during the same interval (four InSAR pairs collected). This dataset
 contains the calculated changes in SWE for each InSAR pair following
 Guneriussen et al. (2001).
description: Detailed methods are available in the main manuscript submitted
 to GRL. Generally, changes in SWE were calculated following the
 density-dependent method outlined by Guneriussen et al. (2001). This
 method calculates SWE change from the unwrapped InSAR phase (provided by
 UAVSAR unwrapped interferograms), local incidence angles, relative
 permittivity, and surface snow density. We calculated incidence angles
 from the available lidar DEM (Adebisi et al., 2022). Relative
 permittivities and densities were obtained from snow pits archived by
 Mason et al. (2024), where relative permittivity was calculated from the
 upper 10 cm densities of the available snow pits following Kovacs et al.
 (1995). For each InSAR pair, we calibrated the phase by estimating the
 phase change from the SWE change, which was documented by a snow pit in a
 high-coherence area.gr
description: # L-band InSAR snow water equivalent retrievals over Fraser Experimental
 Forest, Colorado
 [https://doi.org/10.5061/dryad.x3ffbg7tg](https://doi.org/10.5061/dryad.x3ffbg7tg) ## Description of the data and file structure **Description of the data and file structure:** Data products contain SWE changes calculated from NASA UAVSAR flights at Fraser Experimental Forest during the SnowEx 2021 Time Series Campaign. Two headings (052° and 233°). Dates for the 052° flights include 15–20 January, 20–27 January, 27 January to 3 February, 3–23 February, 23 February to 3 March, 3–10 March, 10–16 March, and 16–22 March. Dates for the 233° flights include 27 January to 3 February, 3–10 March, 10–16 March, and 16–22 March. Clear atmospheric phase ramps were visible for both headings of the 3–10 March unwrapped InSAR pairs and were atmospherically corrected before SWE-change calculations. These products are analysis-ready. SWE-change products typically have a temporal baseline of 7 days, except the 20-day temporal baseline for the 3–23 February interval. 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_Product_Calibration.tif Date1: The first UAVSAR flight date for the InSAR interval. Date2: The second UAVSAR flight date for the InSAR interval.0 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 052° and the secondary flight heading is 233°. Product: All products in this dataset are SWE products. Calibration: Describes the method for phase calibration. intBoard (interval board) products used the SWE change from the interval board at the HQ field site for calibration, whereas pitAdj (snow pit adjusted) used the SWE change from a snow pit at HQ. .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 Fraser, 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=fraser_05209_01](https://uavsar.jpl.nasa.gov/cgi-bin/product.pl?jobName=rockmt_14107_01#data\(opens) [https://uavsar.jpl.nasa.gov/cgi-bin/product.pl?jobName=fraser_23306_01](https://uavsar.jpl.nasa.gov/cgi-bin/product.pl?jobName=rockmt_32109_02#data\(opens) 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(opens](https://doi.org/10.1109/36.957273\(opens) in new window) 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(opens](https://doi.org/10.1016/0165-232X\(94\)00016-Q\(opens) in new window) Snow surface densities were measured in situ during the NASA SnowEx Time Series Campaigns: 2021: [https://doi.org/10.5067/QIANJYJGRWOV(opens](https://doi.org/10.5067/QIANJYJGRWOV\(opens) in new window) Local incidence angles were calculated from the UAVSAR look vectors (see SLC stacks above) and the lidar DEM (Adebisi et al., 2022; upsampled to ~5m) within uavsar_pytools: [https://doi.org/10.5281/zenodo.6789624(opens](https://doi.org/10.5281/zenodo.6789624\(opens) in new window) Phase calibration was computed as the difference between phase change estimated from measured SWE change at either a snow pit or interval board at the HQ field site and the 9-pixel median UAVSAR phase change surrounding the snow pit.