ATLAS/ICESat-2 L3A Inland Water Surface Height, Version 3
Data set id:
There is a more recent version of these data.
Changes for this version include:
- The water body shape file has been updated to include improved river shapes (see Section 3.6, ATBD for ATL13).
- The first photon bias (FPB) correction has been implemented to calculate the apparent width of the full-width at half-max (FWHX) standard deviation of the ATL13 surface (see "Section 188.8.131.52 | First photon bias correction" in the ATBD for ATL13), the apparent strength, and the average detector time. This bug fix improves surface retrievals, especially for highly specular water surfaces.
- Implemented an estimate of short segment wind speed from ATL09 input wind vector components at 10m, interpolated to short segment index photon times (gt[x]/met_wind10_atl09); and derived standard deviation of water surface at the long segment rate (gt[x]/met_wind10_atl13).
- Using a previously identified water body bottom, implemented a minimum height for the range over which to perform the subsurface deconvolution and the bottom height of the vertical profile for long segments. This improves subsurface attenuation when the bottom is detected.
- The threshold procedure that tests photon counts within short-segment histogram multimode bins against sseg_mode_cnt_test, to determine whether to include/exclude from the segment, has been updated to use the standard deviation of signal photon heights per shot segment (sseg_stdev). This bug fix addresses bias due to the removal of ATL13 outputs in the case of large wave heights.
- The value of ancillary_data/inland_water/geoseg_edge_buffer is now selected based on the type and size of a given water body. This change fixes a bug in previous versions and improves the identification of shorelines (see "4.3.1 | Photons contributing to the water surface height," ATBD for ATL13).
- Added a parameter in the water surface height computation that incorporates the maximum available geolocation segments from ATL03, as indicated by geoseg_edge_buffer (default = 5), that lie outside both lake mask edge crossings (added for use in future products currently under development).
- Changed the sign for electromagnetic bias (H_bias_EM). This fixes a bug in previous versions.
- The expression for orthometric water surface height (equations 4.23 and 4.24, ATBD for ATL13) and depth from the mean water surface to the detected bottom have been updated to exclude H_bias_EM, when it is designated as invalid, and H_bias_fit is designated as valid. This update improves this special case.
- Implemented a new scheme that removes misidentified water surfaces due to near-shore influences. After testing that a valid number of short segments have passed all other anomaly testing (valid_sseg_count), and determining the maximum length of a short segment that can be marked as anomalous due to shore buffering (shore_buff_sseg_length), the number of short segments to be designated as anomalous, due to near-shore influences (shore_buffer), is implemented as a 9x9 matrix that depends on water body type and size.
- Cloud confidence flag parameters gt[x]/cloud_flag_atm_atl09, gt[x]/cloud_flag_asr_atl09, and gt[x]/layer_flag_atl09 are now retrieved from the ATL09 product and reported on ATL13 at the short segment rate using nearest neighbor interpolation. This was added to help analyze and better understand short-segment data products.
- Implemented surface (skin) temperature (gt[x]/met_ts_atl09) and NOAA snow/ice flag (gt[x]/snow_ice_atl09) at the short segment rate, derived by interpolation/resampling ATL09 inputs (met_ts and snow_ice) at the 1 Hz and 25 Hz rates. These parameters were added to help analyze and improve overall understanding of short-segment data products.
- Added six water body transect parameters to gt[x]/ (transect_id; sseg_start_lat; sseg_start_lon; sseg_end_lat; sseg_end_lon; and segment_azimuth) which will be used by future inland water body products, currently in development.
This data set (ATL13) contains along-track water surface heights and descriptive statistics for inland water bodies. Water bodies include lakes, reservoirs, bays, and estuaries. Descriptive statistics include along-track surface slope (where data permit), mean and standard deviation, subsurface signal (532 nm) attenuation, wave height, and coarse depth to bottom topography.
13 October 2018 to 11 November 2020
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Blue outlined yellow areas on the map below indicate the spatial coverage for this data set.
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