HadISDH.extremes Part I: A Gridded Wet Bulb Temperature Extremes Index Product for Climate Monitoring

Abstract

AbstractHadISDH.extremes is an annually updated global gridded monthly monitoring product of wet and dry bulb temperature-based extremes indices, from January 1973 to December 2022. Data quality, including spatial and temporal stability, is a key focus. The hourly data are quality controlled. Homogeneity is assessed on monthly means and used to score each gridbox according to its homogeneity rather than to apply adjustments. This enables user-specific screening for temporal stability and avoids errors from inferring adjustments from monthly means for the daily maximum values. For general use, a score (HQ Flag) of 0 to 6 is recommended. A range of indices are presented, aligning with existing standardised indices. Uniquely, provision of both wet and dry bulb indices allows exploration of heat event character — whether it is a “humid and hot”, “dry and hot” or “humid and warm” event. It is designed for analysis of long-term trends in regional features. HadISDH.extremes can be used to study local events, but given the greater vulnerability to errors of maximum compared to mean values, cross-validation with independent information is advised.