All data are processed to version 5 (V5) as of May 22, 2023. The $CI_{cyano}$ continues to be evaluated and the product has known outstanding issues listed in full release notes below.
The CyAN Project and OBPG will periodically reprocess and redistribute the MERIS and OLCI $CI_{cyano}$ time-series. Reprocessing will occur every 10 to 16 months.
Important:
There should be no change/trend analysis across versions. Only a single version should be used in any change/trend analysis.
Version 5 improvements/changes
The following improvements have been implemented in version 5 (May 2023).
This version includes an improved filter for turbid water exclusion, which reduces $CI_{cyano}$ values in highly turbid environments.
Correction to clear water correction when retrieved Kd is invalid.
Applied OLCI to MERIS inter-calibration for CI (Wynne et al., 2021)
Updated gains now using ESA’s Collection-3 vicarious calibration.
Summary of Analysis
The calibration changes should increase sensitivity at low-end and have limited impact at high-end.
A change in the binning process in how maximum values are selected has led to general increase in $CI_{cyano}$ values, especially in the 7-day composite products. This change was necessary, because a complication in using area weighting and maximum value selection.
Version 5 shows on average a 15-20% increase in $CI_{cyano}$ values. This is driven by gain changes (using updated ESA gains)
The turbid water adjustment should reduce false positives in turbid waters.
The following imagery and analysis helps highlight the impact of code and processing changes from CyAN V4 to V5 on different regions around CONUS. The imagery may show the entire tile or a selected region or body of water. The scatter plots comparing V4 to V5 $CI_{cyano}$ values are data for the entire tile.
Central Wisconsin (6_2) August 5, 2022 (2022217)
Difference maps from 5 August 2022 for the Lake Winnebago area (a) and Wisconsin Tile (b) highlighting changes at the pixel level between version 4 and version 5. Red indicates a V5 increase in $CI_{cyano}$. Corresponding $CI_{cyano}$ imagery maps for version 4 (b) and version 5 (c) are shown. A scatterplot summarizing differences between V4 and V5 $CI_{cyano}$ values for the Wisconsin tile with color indicating data density (e). True color (f).
Florida tile (7_5) August 20, 2022 (2022232)
Difference maps from 20 August 2022 for the Florida Tile (6_2; a) and a focus on the Lake Okeechobee area (d) highlighting changes at the pixel level between version 4 and version 5. Red indicates a V5 increase in $CI_{cyano}$. Corresponding $CI_{cyano}$ imagery maps for version 4 (b) and version 5 (c) are shown. A scatterplot summarizing differences between V4 and V5 $CI_{cyano}$ values for the Florida tile with color indicating data density (e). True color (f).
Utah Lake (3_3) August 24, 2022 (2022236)
Difference maps from 24 August 2022 highlighting changes at the pixel level between version 4 and version 5 for Utah Lake (a) and the full Utah region tile (d). Red indicates increase in V5. Corresponding $CI_{cyano}$ imagery version 4 map (b) and version 5 map (c) are shown. A scatterplot summarizing differences between V4 and V5 $CI_{cyano}$ values for the Utah Lake tile (3_3) the color indicates data density (e). True color (f).
Lake Erie Tile (7_2) August 24, 2022 (2022236)
Difference maps from 24 August 2022 highlighting changes at the pixel level between version 4 and version 5 for Lake Erie (a) and the regional tile (d). Red indicates increase in V5. Corresponding mapped $CI_{cyano}$ imagery for Lake Erie version 4 (b) and version 5 (c) are shown. The scatterplot summarizes differences between V4 and V5 $CI_{cyano}$ values for the regional tile (7_2) with color indicating data density (e). True color (f).
Central California Tile (1_3) August 27, 2022 (2022239)
Difference maps for 27 August 2022 for a region including San Francisco Bay (a) and the central California tile (d) highlighting pixel level changes between version 4 and version 5. Red indicates a V5 increase in $CI_{cyano}$. Corresponding $CI_{cyano}$ imagery maps for version 4 (b) and version 5 (c). A scatterplot summarizing differences between V4 and V5 $CI_{cyano}$ values for the central California tile with color indicating data density (e). True color (f).
Lake Pontchartrain Tile (6_5) October 1, 2022 (2022274)
Difference maps for 1 October 2022 highlighting changes at the pixel level between version 4 and version 5 for Lake Pontchartrain (a) and the regional tile (d). Red indicates increase in V5. Corresponding mapped $CI_{cyano}$ imagery for Lake Pontchartrain and the surrounding area version 4 (b) and version 5 (c). The scatterplot summarizes differences between V4 and V5 $CI_{cyano}$ values for the full regional tile (7_2) with color indicating data density (e). True color (f).
