• Extended F/T record to 2021;
• Applied modified seasonal threshold algorithm (MSTA) for the F/T classification where MSTA Tb reference F/T conditions are calibrated annually for each pixel using ERA5 (Hersbach et al., 2018) daily surface air temperature (SAT) records;
• Constant threshold applied over global permanent snow/ice regions to determine the F/T state when the correlation (r-value) between ERA5 SAT and brightness temperature (Tb) is low (absolute value of r less than 0.5). The constant Tb threshold used to distinguish F/T events was determined annually using mean Tb threshold values derived from pixels with higher correlation (absolute value of r greater than 0.5) between SSM/I Tb and ERA5 SAT;
• Applied diurnal amplitude variation (DAV) of Tb from ascending and descending orbital overpass retrievals as an additional step to confirm thaw condition for the PM overpass only;
• Updated quality control (QC) flags included in the product granules identifying grid cells and days with missing and interpolated Tb observations, and characterizing extensive open water bodies, complex terrain, and precipitation events;
• Updated annual data quality assurance (QA) maps included to indicate product performance and reliability.