Flash drought monitor (FDM) datasets

Flash drought monitor (FDM) is the first near-real time monitoring system for operational tracking of flash drought conditions in Spain (https://flash-drought.csic.es). FDM is based on Standardized Precipitation Evapotranspiration Index (SPEI) at short time scale (1-month) and high spatial (1.21 km2) and temporal (weekly) resolution data. Flash drought events were identified following the methodology suggested by Noguera et al. (2020). Thus, we defined a flash drought event as: (i) a minimum length of 4 weeks in the development phase; (ii) a ΔSPEI equal to or <−2 z-units; and (iii) a final SPEI value equal to or <−1.28 z-units (corresponding to return periods of 10 years). See additional details in Noguera et al. (2020).

Here, we provide the datasets used by FDM to monitor flash drought conditions in Spain for the period 1961-2021. We include the SPEI (1-month time scale) dataset used for flash drought identification, as well as meteorological datasets required for SPEI calculation [i.e., precipitation and reference evapotranspiration (ETo)]. Likewise, we include the dataset with the flash drought conditions recorded in Spain for the period 1961-2021, indicating the number of weeks elapsing from the onset of a flash drought by means of the following encoding: value = 0 (no flash drought), value = 1 (flash drought onset), value = 2 (1st week from onset), value = 3 (2nd week from onset), value = 4 (3rd week from onset). All datasets are provided in netCDF (network Common Data Form) format, and contain high spatial (1.21 km2) and temporal (weekly) resolution data for the period 1961-2021.

The precipitation and ETo datasets were created using all daily observational information of precipitation, maximum and minimum air temperature, relative humidity, sunshine duration (as a surrogate of solar radiation) and wind speed from the National Spanish Meteorological Service (AEMET). FAO-56 Penman–Monteith equation (Allen et al., 1998) was used to calculate the reference evapotranspiration (ETo), which is a spatially and temporally comparable metric for the atmospheric evaporative demand (AED). Employing precipitation and ETo data we computed SPEI at a 1-month time scale following the methodology proposed by Vicente-Serrano et al. (2010). Additional details of the datasets development and validation are available in Vicente-Serrano et al. (2017).

References:

Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop Evapotranspiration: Guidelines for Computing Crop Water Requirements.

Noguera, I., Domínguez-Castro, F., & Vicente-Serrano, S. M. (2020). Characteristics and trends of flash droughts in Spain, 1961–2018. Annals of the New York Academy of Sciences, 1472(1), 155– 172. https://doi.org/10.1111/nyas.14365

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(7), 1696–1718. https://doi.org/10.1175/2009JCLI2909.1

Vicente-Serrano, S. M., Tomas-Burguera, M., Beguería, S., Reig, F., Latorre, B., Peña-Gallardo, M., et al. (2017). A High Resolution Dataset of Drought Indices for Spain. Data, 2(3), 22. https://doi.org/10.3390/data2030022