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Combined Climate Extreme Index

Overview

The goal of this diagnostic is to compute time series of a number of extreme events: heatwave, coldwave, heavy precipitation, drought and high wind. Then, the user can combine these different components (with or without weights). The result is an index similar to the Climate Extremes Index (CEI; Karl et al., 1996), the modified CEI (mCEI; Gleason et al., 2008) or the Actuaries Climate Index (ACI; American Academy of Actuaries, 2018). The output consists of a netcdf file containing the area-weighted and multi-model multi-metric index. This recipe can be applied to data with any temporal resolution, and the running average is computed based on the user-defined window length (e.g. a window length of 5 would compute the 5-day running mean when applied to data, or 5-month running mean when applied to monthly data).

In recipe_extreme_index.yml, after defining the area and reference and projection period, the weigths for each metric selected. The options are

  • weight_t90p the weight of the number of days when the maximum temperature exceeds the 90th percentile,
  • weight_t10p the weight of the number of days when the minimum temperature falls below the 10th percentile,
  • weight_Wx the weight of the number of days when wind power (third power of wind speed) exceeds the 90th percentile,
  • weight_cdd the weight of the maximum length of a dry spell, defined as the maximum number of consecutive days when the daily precipitation is lower than 1 mm, and
  • weight_rx5day the weight of the maximum precipitation accumulated during 5 consecutive days.

Available recipes and diagnostics

Recipes are stored in recipes/

  • recipe_extreme_index.yml

Diagnostics are stored in diag_scripts/magic_bsc/

  • extreme_index.R

User settings

User setting files are stored in recipes/

  1. recipe_extreme_index.yml

    Required settings for script

    • weight_t90p: 0.2 (from 0 to 1, the total sum of the weight should be 1)
    • weight_t10p: 0.2 (from 0 to 1, the total sum of the weight should be 1)
    • weight_Wx: 0.2 (from 0 to 1, the total sum of the weight should be 1)
    • weight_rx5day: 0.2 (from 0 to 1, the total sum of the weight should be 1)
    • weight_cdd: 0.2 (from 0 to 1, the total sum of the weight should be 1)
    • running_mean: 5 (depends on the length of the future projection period selected, but recommended not greater than 11)

Variables

  • tasmax (atmos, daily, longitude, latitude, time)
  • tasmin (atmos, daily, longitude, latitude, time)
  • sfcWind (atmos, daily, longitude, latitude, time)
  • pr (atmos, daily, longitude, latitude, time)

Observations and reformat scripts

None

References

Example plots

Average change in the heat component (t90p metric) of the Combined Climate Extreme Index for the 2020-2040 compared to the 1971-2000 reference period for the RCP 8.5 scenario simulated by MPI-ESM-MR.