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Henry F. Diaz

Using High Resolution Paleoclimate Reconstructions Since AD 1500 in Support of Research on Environmental/Societal Change in Hawai‘i
Recent work to extend the instrumental record of Hawaiian rainfall (available since the early 1900s ) back several centuries indicates the presence of large and significant variations in rainfall on decadal time scales (see time series graphic above). Parallel efforts to understand agricultural changes in the Hawaiian Islands prior to European influences suggests that after about 1650 CE there was a shift in emphasis to productive maximizing strategies, with implications for the region’s economic and socio-political stability.The above is one of the motivating ideas for conducting this workshop. Previous work by several of the participants argued that an increased reliance on risky product maximization strategies...
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Possible Future Changes to Water Resources in the Salt and Verde River Basins Associated with Atmospheric River Events
The Salt and Verde river basins in northeastern Arizona are a vital source of fresh water for the greater Phoenix metropolitan area and for two Native American tribes who rely on the basins’ natural resources for their livelihoods. The region depends on winter rain and snow to replenish the river basins’ water supply. Atmospheric rivers – long, narrow channels in the atmosphere that carry water vapor from the Pacific Ocean – supply a substantial portion of this winter precipitation. While atmospheric rivers are critical for maintaining water resources and preventing drought, they occasionally cause extreme storms that lead to flooding. Scientists project that climate change will affect the intensity and frequency...
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In the expectation that global climate will change steadily in the coming decades, this research project had the goal to obtain a more detailed view of the climatic changes that Hawai’i could experience by the mid and late 21st century. Given the importance of rainfall for Hawaiian ecosystems and freshwater reserves, this project investigated past seasonal rainfall pattern and developed a statistical model to estimate future rainfall changes for the major islands. As a result of this research, high-resolution maps and data are now available that researchers can use to study potential impacts on endangered species, or use the rainfall changes as input in decision-support tools.This data product provides data files...
Abstract: The aim of this paper is to present a statistical downscaling method in which the relationships between present-day daily weather patterns and local rainfall data are derived and used to project future shifts in the frequency of heavy rainfall events under changing global climate conditions. National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) reanalysis data from wet season months (November to April) 1958–2010 are composited for heavy rain days at 12 rainfall stations in the Hawaiian Islands. The occurrence of heavy rain events (days with amounts above the 90th percentile estimated from all wet season rain days 1958–2010) was found to be strongly correlated...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/2014JD022059/abstract): Seasonal mean rainfall projections for Hawai‘i are given based on statistical downscaling of the latest Coupled Model Intercomparison Project phase 5 (CMIP5) global model results for two future representative concentration pathways (RCP4.5 and RCP8.5). The spatial information content of our statistical downscaling method is improved over previous efforts through the inclusion of spatially extensive, high-quality monthly rainfall data set and the use of improved large-scale climate predictor information. Predictor variables include moisture transport in the middle atmosphere (700 hPa), vertical temperature gradients, and geopotential...
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