Question: SWOT pixel cloud data product misclassify cropland as water

[john6444]

Hi, all,

Recently I find that SWOT Pixel Cloud Data Product (SWOT_L2_HR_PIXC_D) misclassifies cropland (may be characterized with high soil moisture) as water area, which leads to incorrectly wider river channel width estimation if cropland is contiguous with river channel in this situation (see attached figures).

Specifically, I directly utilize classified results from SWOT pixel cloud data product. Only pixels with with a water fraction above 0.1 and not bright land that were classified as open water, water near land, or dark water ("water_frac" >= 0.1, "bright_land_flag" = 0, "classification" ranges from 3 to 5), which is slightly modified from Simoes‐Sousa et al. (2025)

Does any experience this issue before?

Reference:
Simoes‐Sousa I T, Camargo C M L, Tavora J, et al. The May 2024 flood disaster in southern Brazil: Causes, impacts, and SWOT‐based volume estimation[J]. Geophysical Research Letters, 2025, 52(4): e2024GL112442.

[hyoklee]

Hi, would you please share the exact .nc file name that corresponds to the image that you shared?
E.g., SWOT_L2_HR_PIXC_042_158_157R_20251128T072513_20251128T072524_PID0_01.nc.

Also, how did you apply water_frac_uncert dataset in your water classification?

[john6444]

Thanks for your response. SWOT pixel cloud data utilized here is "SWOT_L2_HR_PIXC_019_200_086L_20240806T215721_20240806T215732_PGD0_01.nc".

As for "water_frac_uncert", I did not apply it for open water classification because I find "water_frac_uncert" value between open water (river) and cropland is trivial (see attached figure "water_fraction_uncertainty_comparison.png"). Spatial distribution of selected pixel cloud data with respect to open water and cropland is shown in attached figure "river_pixel_cloud_data.png" and "cropland_pixel_cloud_data.png", respectively.

[hyoklee]

Thank you for providing the exact file name.

Would you please tell me lat/lon index to subset the region?
I tried to plot the data but I could not locate the region that shows the same pattern from the file.

Here are the 2 images that I got - one without uncertainty and another with uncertainty < 1.0.

[john6444]

Thanks for your detailed description. The specific spatial extent is at the end of Daqing River, whose specific longitude range is from 116.875035 to 116.931715 and latitude range is between 39.046942 and 39.065448. This chosen region is not large because it is only used as a demonstration of misclassifying neighbouring cropland (potentially with high soil moisture) as open water.

Thanks for your time.