IRIS: ICESat-2 River Surface Slope

ICESat-2 River Surface Slope (IRIS)

When using this data please cite Scherer D., Schwatke C., Dettmering D., Seitz F.: ICESat-2 river surface slope (IRIS): A global reach-scale water surface slope dataset. Scientific Data, 10(1), 359, 10.1038/s41597-023-02215-x, 2023.

A detailed description of the methodology and validation is published in Scherer D., Schwatke C., Dettmering D., Seitz F. : ICESat-2 Based River Surface Slope and Its Impact on Water Level Time Series From Satellite Altimetry. Water Resources Research, 10.1029/2022WR032842, 2022.

1. Summary
The unique multibeam lidar altimeter of ICESat-2 is used to measure reach-scale water surface slope (WSS) every time the spacecraft’s orbit crosses a reach. The method of deriving WSS from simultaneous ICESat-2 ATL13 (Jasinski et al., 2021) observations is described in detail and validated in Scherer et al. (2022). In this ICESat-2 River Surface Slope (IRIS) dataset, we provide the minimum, average, and maximum slope derived with three different approaches (across, along, and combined) per reach. Additionally, we give the standard deviation and epochs of the derived WSS data. The reaches are defined by the SWOT River Database (SWORD, Altenau et al., 2021).

An interactive map is available at DAHITI.

2. Version History

IRIS v0: Only includes the reaches studied in Scherer et al. (2022).
Based on ICESat-2 ATL13 v5, Cycle 1-13 (October 2018 to October 2021) and SWORD Version v1.

IRIS v1: Global coverage (limited by ICESat-2 data availability and cloud cover).
Based on ICESat-2 ATL13 v5, Cycle 1-16 (October 2018 to August 2022) and SWORD Version v2.

IRIS v2: Global coverage with 6,083 additional reaches and 92,347 more observations compared to v1.
Based on ICESat-2 ATL13 v6, Cycle 1-19 (October 2018 to April 2023) and SWORD Version v15.

IRIS v2.1: Based on ICESat-2 ATL13 v6, Cycle 1-19 (October 2018 to April 2023) and SWORD Version v16.

IRIS v2.2: 3,251 additional reaches and 58,862 new observations compared to v2.1.
Based on ICESat-2 ATL13 v6, Cycle 1-20 (October 2018 to August 2023) and SWORD Version v16.

IRIS v2.3: 1,595 additional reaches and 32,590 new observations compared to v2.2.
Based on ICESat-2 ATL13 v6, Cycle 1-21 (October 2018 to October 2023) and SWORD Version v16.

IRIS v2.6: 2,755 additional reaches and 362,136 new observations compared to v2.3.
Based on ICESat-2 ATL13 v6, Cycle 1-23 (October 2018 to May 2024) and SWORD Version v16.

3. Data Format and Variable Description

From Version 2.6, IRIS is also available as GeoPackage.
The IRIS data is stored in a single NetCDF4 file which is structured in a single group containing the following variables:
reach_id:
The SWORD reach identifier [-]
lon:
Approx. centroid longitude of the SWORD reach [degrees east]
lat:
Approx. centroid latitude of the SWORD reach [degrees north]
across_flag, along_flag, combined_flag:
Flags indicating whether ICESat-2 [across/along/combined] slope is available (1) for the reach or not (0) [-]
avg_across_slope, avg_along_slope, avg_combined_slope:
Average (median) ICESat-2 [across/along/combined] slope for the reach [mm/km]
min_across_slope, min_along_slope, min_combined_slope:
Minimum ICESat-2 [across/along/combined] slope for the reach [mm/km]
max_across_slope, max_along_slope, max_combined_slope:
Maximum ICESat-2 [across/along/combined] slope for the reach [mm/km]
std_across_slope, std_along_slope, std_combined_slope:
ICESat-2 [across/along/combined] slope standard deviation for the reach [mm/km]
n_across_slope, n_along_slope, n_combined_slope:
Number of days with ICESat-2 [across/along/combined] slope observations for the reach [-]
min_date_across_slope, min_date_along_slope:, min_date_combined_slope:
First date of ICESat-2 [across/along/combined] slope observations for the reach [days since 2000-01-01]
max_date_across_slope, max_date_along_slope:, max_date_combined_slope:
Latest date of ICESat-2 [across/along/combined] slope observations for the reach [days since 2000-01-01]

4. References

Scherer D., Schwatke C., Dettmering D., Seitz F.: ICESat-2 river surface slope (IRIS): A global reach-scale water surface slope dataset. Scientific Data, 10(1), 359, 10.1038/s41597-023-02215-x, 2023
Scherer D., Schwatke C., Dettmering D., Seitz F. (2022): ICESat-2 Based River Surface Slope and Its Impact on Water Level Time Series From Satellite Altimetry, Water Resources Research, https://doi.org/10.1029/2022WR032842
Jasinski M., Stoll J., Hancock D., Robbins J., Nattala J., Morison J., Jones B., Ondrusek M., Pavelsky T.M., Parrish C. and the ICESat-2-Science-Team (2021). ATLAS/ICESat-2 L3A Inland Water Surface Height, Version 5. [Dataset]
Altenau E.H., Pavelsky T.M., Durand, M.T., Yang X., Frasson, R.P.d.M., Bendezu, L. (2021): SWOT River Database (SWORD) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.3898569