DOI: 10.5281/zenodo.11044872
title: Dheed : a global database of dry and hot extreme events from 2016 to 2021

description: Dheed : a global database of dry and hot extreme events from 1950 to 2021

Method

Hot and dry extreme events are detected using ECMWF ReAnalysis (ERA5) hourly data (see limitations). Hot conditions are assessed through daily maximum 2m temperature (Tmax). Dry conditions are assessed through daily differences between total precipitation and evapotranspiration averaged over the preceding 30, 90 and 180 days (PEI_30, PEI_90, PEI_180). Conditions at a specific location (spatial grid cell) are considered extreme when Tmax is greater then the 99th percentile and a drought indicator is less than the 1st percentile of their respective distributions over time. These Discrete Extreme Occurrences (DEO) are stored in the EventCube. Through a connected component analysis, connected DEOs are assigned unique labels when they are contiguous in space or time. These labels are stored in the labelcube. Summary statistcs for all uniquely labelled extreme events are stored in table EventStats. 

For a graphical overview of the method, see the workflow.

Dataset description

EventCube_ranked_pot0.01_ne0.1.zarr [4.8G]

Global data cube with Int8 values coding for types of Discrete Extreme Occurrences from 1950 to 2021. The first bit to the right (little end) is set to 1 where P(X~Tmax) > 0.99. The second to fourth bits are set to 1 where P(X~PEI) < 0.01, for PEI~30, PEI~90 and PEI~180 respectively. The fifth bit is for non extremes, i.e. where all four indicators lie in the middle of their distribution (P(X) > 0.1 AND P(X) < 0.9). Bits 6 to 8 contain no information. 

labelcube_ranked_pot0.01_ne0.1_cmp_2016_2021.zarr [96M]

Global data cube of labels obtained by labelling connected blobs of Discrete Extreme Occurrences from EventCube_ranked_pot0.01_ne0.1 from 2016 to 2021 where both daily maximum temperature and any of the drought indicators are extremes, i.e. where values in EventCube are > 1 AND odd. No filtering was applied.

EventStats_ranked_pot0.01_ne0.1_cmp_2016_2021.csv

Table of statistics for labelled hot and dry extreme events from labelcube_ranked_pot0.01_ne0.1_cmp_2016_2021. For each labelled event (`label`), the table gives the spatio-temporal bounding box (`start_time`, `end_time`, `longitude_min`, `longitude_max`, `latitude_min`, `latitude_max`), statistices on the the indicators (`t2mmax_mean`, `t2mmax_min`, `t2mmax_max`, `pei_30_mean`, `pei_30_min`, `pei_30_max`, `pei_90_mean`, `pei_90_min`, `pei_90_max`, `pei_180_mean`, `pei_180_min`, `pei_180_max`), the percentage of the event affected by a single indicator (`heat`, `drought30`, `drought90`, `drought180`, `compound`), the percentage of the event that occurred over land (`land_share`), a proxy of the total volume of the event as the number of voxels weighted by cos(latitude) (`volume`), its duration as end_time - start_time + 1 day (`duration`), a proxy of its total affected area as the ratio between volume and duration (`area`). Entries are sorted by decreasing volume.

EventStats_ranked_pot0.01_ne0.1_cmp_2016_2021_landonly.csv

Table of statistics for labelled hot and dry extreme events from labelcube_ranked_pot0.01_ne0.1_cmp_2016_2021 calculated over land grid cells only. See description of EventStats_ranked_pot0.01_ne0.1_cmp_2016_2021.csv for details. 

Limitations



At the time of computation, only ERA5 preliminary back-extension from 1950 to 1978 was available. An updated version of the dataset uses the current version of ERA5.

Heatwaves are computed from daily maximum temperature only.

There is no minumum duration set for heatwaves.

Compound hot and dry conditions are assessed from the single variate temporal distribution of temperature and drought indicators. Multi-variate distributions are not considered.