DOI: 10.5281/zenodo.18411292
title: Global Standardized Precipitation Evapotranspiration Index (SPEI) for the Common Era, calculated using monthly climate variables from MPI-ESM model simulations from past2k experiment in CMIP6

description: Data Production Process

Based on the monthly data of temperature (tasmin, tasmax), precipitation (pr), atmospheric pressure (ps), wind field (sfcWind), radiation (rsds, rsdt), and relative humidity (hurs) from January 1 CE to December 2014 CE, output by the MPI-ESM1-2-LR model under the CMIP6 past2k experiment (Mauritsen et al., 2019), potential evapotranspiration (PET) was calculated using the Penman-Monteith formula recommended by the Food and Agriculture Organization of the United Nations (FAO). According to the FAO guidelines for calculating PET, the original 10-meter wind speed outputs from the model were converted to wind speed at a height of 2 meters. Subsequently, utilizing the Standardized Precipitation Evapotranspiration Index (SPEI) calculation formula developed by Vicente-Serrano et al. (2010), a global gridded SPEI dataset for the past 2000 years was generated. This dataset includes SPEI data at three time scales: monthly scale (SPEI-01, reflecting short-term meteorological anomalies), seasonal scale (SPEI-03, reflecting water availability during critical crop growth periods, which is a core indicator for agricultural drought), and annual scale (SPEI-12, reflecting annual water balance, closely associated with river runoff, reservoir storage, and annual groundwater level variations). The spatial resolution of the calculated SPEI data is approximately 250 km, corresponding to a latitude-longitude grid of about 1.875 degrees. The data have been formatted into NetCDF4, the standard format for data sharing in the meteorological field, and include relevant metadata (such as latitude and longitude, spatial resolution, time, variable names, variable types, default values, etc.). This dataset can be used to study the spatiotemporal variations of drought at different time scales over the past 2000 years on global and regional scales. The model outputs mentioned above were downloaded from the Earth System Grid Federation (ESGF).

ReferencesMauritsen, T., Bader, J., Becker, T., et al. (2019). Developments in the MPI-M Earth System Model version 1.2 (MPI-ESM1.2) and Its Response to Increasing CO2. Journal of Advances in Modeling Earth Systems, 11, 998-1038.Vicente-Serrano S. M., Beguería S., López-Moreno J. I. (2010). A Multiscalar Drought Index Sensitive to Global Warming: The Standardized Precipitation Evapotranspiration Index. Journal of Climate, 23, 1696-1718.
description: Usage Notes

(1) Opening method: This dataset is saved in the standard NetCDF4 file format, which can be directly opened and utilized with software such as PanoplyWin, ArcGIS (version 10 and above), Matlab, R, Python, and other programs that support NetCDF files. It should be specially noted that, 'Time' in the dataset is expressed in the 'YMM' format, where 'Y' represents the year (AD) and 'MM' indicates the month (01-12). For example: time = 101 denotes January of the year 1 AD, time = 1201 represents January of the year 12 AD, time = 85110 corresponds to October of the year 851 AD, time = 200012 indicates December of the year 2000 AD. (2)  Data Application: This dataset can be utilized to investigate the spatiotemporal variations of drought at different time scales over the past 2000 years on global and regional scales. 

FundingThis work is jointly supported by the National Science Foundation of China (NSFC) project [Grant No. 42171044], the National Key R&D Program of China [Grant No. 2022YFF0801102] and the CAS “Light of West China” Program.