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=fraser_23306_01
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 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 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 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 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.