DOI: 10.5066/p9kemhym
title: Change factors to derive future precipitation depth-duration-frequency (DDF) curves at 174 National Oceanic and Atmospheric Administration (NOAA) Atlas 14 stations in central and south Florida

description: This data release consists of Microsoft Excel workbooks, shapefiles, and a figure (png format) related to a cooperative project between the U.S. Geological Survey (USGS) and the South Florida Water Management District (SFWMD) to derive future change factors for precipitation depth-duration-frequency (DDF) curves at 174 National Oceanic and Atmospheric Administration (NOAA) Atlas 14 stations in central and south Florida. The change factors were computed as the ratio of future (2050-2089) to historical (1966-2005) extreme precipitation depths fitted to extreme precipitation data using a constrained maximum likelihood (CML) approach. The change factors are tabulated by duration (1, 3, and 7 days) and return period (5, 10, 25, 50, 100, and 200 years). The official historical NOAA Atlas 14 DDF curves based on partial-duration series (PDS) can be multiplied by the change factors derived in this project to determine potential future extreme precipitation for events of a given duration and return period. Various statistical, dynamical and hybrid downscaled precipitation datasets were used to derive the change factors at the grid cells closest to the NOAA Atlas 14 stations including (1) the Coordinated Regional Downscaling Experiment (CORDEX), (2) the Localized Constructed Analogues (LOCA) dataset, (3) the Multivariate Adaptive Constructed Analogs (MACA) dataset, (4) the Analog Resampling and Statistical Scaling Method by Jupiter Intelligence using the Weather Research and Forecasting Model (JupiterWRF). The emission scenarios evaluated include representative concentration pathways RCP4.5 and RCP8.5 from the Coupled Model Intercomparison Project Phase 5 (CMIP5) for the downscaled climate datasets CORDEX, LOCA, and MACA. The emission scenarios evaluated for the JupiterWRF downscaled dataset include RCP8.5 from CMIP5, and shared socioeconomic pathways SSP2-4.5 and SSP5-8.5 from the Coupled Model Intercomparison Project Phase 6 (CMIP6). Only daily durations are evaluated for JupiterWRF. When applying change factors to the historical NOAA Atlas 14 DDF curves to derive future precipitation DDF for the entire range of durations and return periods evaluated as part of this project, there is a possibility that the resulting future DDF curves may be inconsistent across duration and return period. By inconsistent it is meant that the precipitation depths may decrease for longer durations instead of increasing. Depending on the change factors used, this may happen in up to 6 percent of cases. In such a case, it is recommended that users use the higher of the future precipitation depths derived for the duration of interest and the previous shorter duration. This data release consists of four shapefiles: (1) polygons for the basins defined in the South Florida Water Management District (SFWMD)'s ArcHydro Enhanced Database (AHED) (AHED_basins.shp); (2) polygons of climate regions (Climate_regions.shp); (3) polygons of Areal Reduction Factor (ARF) regions for the state of Florida (ARF_regions.shp); and (4) point locations of NOAA Atlas 14 stations in central and south Florida for which depth-duration-frequency curves and change factors of precipitation depths were developed as part of this project (Atlas14_stations.shp). This data release also includes 21 tables. Four tables contain computed change factors for the four downscaled climate datasets: (1) CORDEX (CF_CORDEX_future_to_historical.xlsx); (2) LOCA (CF_LOCA_future_to_historical.xlsx); (3) MACA (CF_MACA_future_to_historical.xlsx); and (4) JupiterWRF (CF_JupiterWRF_future_to_historical.xlsx). Eight tables contain the corresponding DDF values for the historical and future periods in each of the four downscaled climate datasets: (1) CORDEX historical (DDF_CORDEX_historical.xlsx); (2) CORDEX future (DDF_CORDEX_future.xlsx); (3) LOCA historical (DDF_LOCA_historical.xlsx); (4) LOCA future (DDF_LOCA_future.xlsx); (5) MACA historical (DDF_MACA_historical.xlsx); (6) MACA future (DDF_MACA_future.xlsx); (7) JupiterWRF historical (DDF_JupiterWRF_historical.xlsx); and (8) JupiterWRF future (DDF_JupiterWRF_future.xlsx). Six tables contain quantiles of change factors at 174 NOAA Atlas 14 stations in central and south Florida derived from various downscaled climate datasets considering: (1) all models and all future emission scenarios evaluated (CFquantiles_future_to_historical_all_models_allRCPs.xlsx); (2) all models and only the RCP4.5 and SSP2-4.5 future emission scenarios (CFquantiles_future_to_historical_all_models_RCP4.5.xlsx); (3) all models and only the RCP8.5 and SSP5-8.5 future emission scenarios (CFquantiles_future_to_historical_all_models_RCP8.5.xlsx); (4) best models and all future emission scenarios evaluated (CFquantiles_future_to_historical_best_models_allRCPs.xlsx); (5) best models and only the RCP4.5 and SSP2-4.5 future emission scenarios (CFquantiles_future_to_historical_best_models_RCP4.5.xlsx); and (6) best models and only the RCP8.5 and SSP5-8.5 future emission scenarios (CFquantiles_future_to_historical_best_models_RCP8.5.xlsx). Finally, three tables contain miscellaneous information: (1) information about downscaled climate datasets and National Oceanic and Atmospheric Administration (NOAA) Atlas 14 stations used in this project (Datasets_station_information.xlsx); (2) best models for each downscaled climate dataset and for all downscaled climate datasets considered together (Best_model_lists.xlsx); and (3) areal reduction factors by region in Florida (Areal_reduction_factors.xlsx). An R script is provided which generates boxplots of change factors at a NOAA Atlas 14 station, or for all NOAA Atlas 14 stations in an ArcHydro Enhanced Database (AHED) basin or county (create_boxplot.R). A Microsoft Word file documenting code usage and available options is also provided within this data release (Documentation_R_script_create_boxplot.docx). Disclaimer: A bias-correction error was recently found in the bias-corrected CORDEX data used in this project as described at https://na-cordex.org/bias-correction-error.html. The impact of this error in the computed DDF curves and change factors is not fully known. Once a corrected CORDEX datasset becomes available, the USGS will publish a new set of DDF curves and change factors for CORDEX based on the new data if necessary. Users should exercise caution when using CORDEX change factors in decision-making until the data is revised.