Revised CMIP6-LOCA2 (v20240915) precipitation extreme metrics from 1950-2100 for the Contiguous United States

NOAA’s Assessment Technical Support Unit (TSU) created a suite of temperature and precipitation metrics of extremes and threshold exceedance variables based on the Climate Model Intercomparison Program Phase 6 CMIP6 Localized Constructed Analogs (CMIP6-LOCA2) data set to support the Fifth National Climate Assessment (NCA5). Following the v20240915 revision of the CMIP6-LOCA2 precipitation projections, these metrics required updating. This release provides the revised precipitation extreme metrics. The revised precipitation projections address a 5-10% weaknesses in extreme precipitation values (~99.9th percentile value), primarily in summer in a band extending from the Gulf of California northwards through Nevada and eastern Oregon and Washington (see https://cirrus.ucsd.edu/~pierce/docs/LOCA2_new_precip_release_notes_2024-10-15.pdf). Using the same approach as the original TSU work, daily precipitation from CMIP6-LOCA2 (v20240915) was processed with the Python xclim library to generate a suite of annual extreme precipitation metrics.

This work supports the Climate Resilience Information System (CRIS, https://cris.climate.gov) by updating the precipitation metrics to v20240915 and providing spatial summaries for US counties, Watershed Boundary Dataset (WBD) HU8 hydrologic units, and Census Tribal Boundary and Annexation Survey (BAS) for Tribal lands. As in the NCA5, CRIS uses a 14-model weighted ensemble meanreferred to here as the “CRIS-Ensemble”which is a subset of the 27 CMIP6-LOCA2 models available for the ssp245, ssp370, and ssp585 scenarios.

The 27 included CMIP6 GCMs are: ACCESS-CM2, ACCESS-ESM1-5, AWI-CM-1-1-MR, BCC-CSM2-MR, CESM2-LENS, CNRM-CM6-1, CNRM-CM6-1-HR, CNRM-ESM2-1, CanESM5, EC-Earth3, EC-Earth3-Veg, FGOALS-g3, GFDL-CM4, GFDL-ESM4, HadGEM3-GC31-LL, HadGEM3-GC31-MM, INM-CM4-8, INM-CM5-0, IPSL-CM6A-LR, KACE-1-0-G, MIROC6, MPI-ESM1-2-HR, MPI-ESM1-2-LR, MRI-ESM2-0, NorESM2-LM, NorESM2-MM, TaiESM1

The variables included are:
Annual highest precipitation total over a 1-day period (prmax1day, units=in)
Annual highest precipitation total over a 10-day period (prmax10day, units=in)
Annual highest precipitation total over a 5-day period (prmax5day, units=in)
Annual maximum consecutive number of dry days (dry_spell_max_length, units=d)
Annual maximum consecutive number of wet days (wet_spell_max_length, units=d)
Annual number of days where precipitation exceeded the historical (1951-1980) 90th percentile (pr_days_above_nonzero_90th, units=d)
Annual number of days where precipitation exceeded the historical (1951-1980) 95th percentile (pr_days_above_nonzero_95th, units=d)
Annual number of days where precipitation exceeded the historical (1951-1980) 99th percentile (pr_days_above_nonzero_99th, units=d)
Annual number of days with total precipitation ≥ to 1 inch (pr_days_ge_1in, units=d)
Annual number of days with total precipitation ≥ to 2 inch (pr_days_ge_2in, units=d)
Annual number of days with total precipitation ≥ to 3 inch (pr_days_ge_3in, units=d)
Annual number of days with total precipitation ≥ to 4 inch (pr_days_ge_4in, units=d)
Annual number of days with total precipitation ≥ to 5 inch (pr_days_ge_5in, units=d)
Annual number of dry days (2.54 mm/d threshold) (dry_days, units=d)
Annual number of wet days (2.54 mm/d threshold) (wetdays, units=d)
Annual total of daily precipitation exceeding the historical (1951-1980) 90th percentile (pr_above_nonzero_90th, units=in)
Annual total of daily precipitation exceeding the historical (1951-1980) 95th percentile (pr_above_nonzero_95th, units=in)
Annual total of daily precipitation exceeding the historical (1951-1980) 99th percentile (pr_above_nonzero_99th, units=in)
Annual total precipitation (pr_annual, units=in)