Global meteorological drought – Part 2: Seasonal forecasts
Global seasonal forecasts of meteorological drought using the standardized precipitation index (SPI) are produced using two data sets as initial conditions: the Global Precipitation Climatology Centre (GPCC) and the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis (E...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-07-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | http://www.hydrol-earth-syst-sci.net/18/2669/2014/hess-18-2669-2014.pdf |
| Summary: | Global seasonal forecasts of meteorological drought using the standardized
precipitation index (SPI) are produced using two data sets as initial
conditions: the Global Precipitation Climatology Centre (GPCC) and the European Centre for Medium-Range Weather Forecasts
(ECMWF) ERA-Interim reanalysis (ERAI); and two seasonal forecasts of precipitation,
the most recent ECMWF seasonal forecast system and climatologically based
ensemble forecasts. The forecast evaluation focuses on the periods where
precipitation deficits are likely to have higher drought impacts, and the
results were summarized over different regions in the world. The verification
of the forecasts with lead time indicated that generally for all regions the
least reduction on skill was found for (i) long lead times using ERAI or
GPCC for monitoring and (ii) short lead times using ECMWF or climatological
seasonal forecasts. The memory effect of initial conditions was found to be
1 month of lead time for the SPI-3, 4 months for the SPI-6 and 6 (or more)
months for the SPI-12. Results show that dynamical forecasts of precipitation
provide added value with skills at least equal to and often above that of
climatological forecasts. Furthermore, it is very difficult to improve on the
use of climatological forecasts for long lead times. Our results also support
recent questions of whether seasonal forecasting of global drought onset was
essentially a stochastic forecasting problem. Results are presented
regionally and globally, and our results point to several regions in the
world where drought onset forecasting is feasible and skilful. |
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| ISSN: | 1027-5606 1607-7938 |