Projecting Changes in S. Florida Rainfall for the 21st century: Scenarios, Downscaling and Analysis

Developing scenarios for climate change adaptation for sub-tropical coastal areas where changes in precipitation have consequences for drought and flood is necessary. Here, a Non-Homogeneous Hidden Markov Model (NHMM) is applied for simulating future daily rainfall at nineteen stations in South Florida. The CMIP 5 simulation of the coupled ocean-atmosphere model CMCC-CMS from 1950-2100 is used for projection. The application directly considers seasonality through changes in the driving variables, rather than developing separate models for each canonical season. Biases between the re-analysis model and retrospective simulations of the CMCC-CMS are addressed. The results indicate that, as a consequence of increase of the CO2 concentration and temperature, South Florida may be subjected to drier conditions for most of the year. The number of wet days reduces while extreme rainfall frequency increases. These are consistent with trends of rainfall observed in the recent data. A modest reduction in total rainfall in the February to May period, and a slight increase in the September-October projected rainfall is noted. Changes in the expression of the North Atlantic Subtropical High in the model appear to correspond to circulation changes that determine the new seasonality and patterns of rainfall in the region.