A North American regional reanalysis climatology of the Haines Index

Abstract

A warm-season (May through October) Haines Index climatology is derived using 32-km regional reanalysis temperature and humidity data from 1980 to 2007. We compute lapse rates, dewpoint depressions, Haines Index factors A and B, and values for each of the low-, mid- and high-elevation variants of the Haines Index. Statistical techniques are used to investigate the spatial and temporal variability of the index across North America. The new climatology is compared with a previous climatology derived from 2.5° (~280 km) global reanalysis data. Maps from the two climatologies are found to be very similar for most of North America. The largest differences appear along the eastern coastline and in regions of large elevation gradients, where the orography in the 32-km climatology is better resolved than that of the 2.5° climatology. In coastal areas of eastern North America and where there is steeply sloping terrain, the new climatology can augment the information from the 2.5° climatology to help analyse the performance and interpret the results of the Haines Index in these regions. A linear trend analysis of the total number of high-Haines Index days occurring in each warm season reveals no significant linear trends over the 28-year data period.