Utilización del Standardized Precipitation Evapotranspiration Index (SPEI)

Transcription

1 Utilización del Standardized Precipitation Evapotranspiration Index (SPEI) en el análisis y monitorización de las sequías: características, recomendaciones y comparación con otros indicadores Application of the Standardized Precipitation Evapotranspiration Index (SPEI) for drought analysis and monitoring: characteristics, recommendations and comparison with other indices Sergio M. VICENTE-SERRANO Santiago BEGUERÍA Natalia MARTÍN-HERNÁNDEZ Miquel TOMÁS-BURGUERA César AZORÍN-MOLINA Consejo Superior de Investigaciones Científicas (Spanish National Research Council Spain)

2 THE COMPLEXITY OF DROUGHT QUANTIFICATION AND ANALYSIS Droughts are difficult to pinpoint in time and space given different economic sectors and natural systems affected. We identify a drought by its effects or impacts on different types of systems (agriculture, water resources, ecology, forestry, economy, etc.), but there is not a physical variable we can measure to quantify droughts. Long-term drought objective metrics (streamflows, soil moisture, lake levels, etc.) are commonly not available. Moreover, using only objective metrics other relevant variables to determine drought severity (e.g. the atmospheric water demand) are not taken into account. We use the so-called DROUGHT INDICES for drought quantification and analysis.

3 EXISTING DROUGHT INDICES SPI (meses) SPI (48meses) z-values z-values z-values - -months SPEI Inflows months SPEI Reservoir storages months SPEI Releases

4 EXISTING DROUGHT INDICES Precipitation-based drought indices, including the SPI, rely on two assumptions: ) The variability of precipitation is much higher than that of other variables, such as the atmospheric water demand ) The other variables are stationary (i.e., they have no temporal trend). In this scenario, the importance of these other variables is negligible, and droughts are controlled by the temporal variability in precipitation. Is this scenario plausible nowadays?

5 STANDARDIZED PRECIPITATION EVAPOTRANSPIRATION INDEX (SPEI) The SPEI uses the difference between precipitation and ETo. This represents a simple climatic water balance which is calculated at different time scales to obtain the SPEI. With a value for ETo, the difference between the precipitation (P) and PET for the month i is calculated according to: D i = P i -ETo i, The calculated D values are aggregated at different time scales..5 month. f(x).5 months. 6 months.5 4 months months P-PET

6 STANDARDIZED PRECIPITATION EVAPOTRANSPIRATION INDEX (SPEI) Vicente-Serrano S.M. et al., () A Multi-scalar drought index sensitive to global warming: The Standardized Precipitation Evapotranspiration Index SPEI. Journal of Climate : Vicente-Serrano, S.M. et al. (): A new global.5 gridded dataset (96) of a multiscalar drought index: comparison with current drought index datasets based on the Palmer Drought Severity Index. Journal of Hydrometeorology. : 4 Beguería, S. et al., (): A multi-scalar global drought data set: the SPEIbase: A new gridded product for the analysis of drought variability and impacts. Bulletin of the American Meteorological Society. 9, 554 Vicente-Serrano, S.M. et al., (). Comment on Characteristics and trends in various forms of the Palmer Drought Severity Index (PDSI) during 9-8 by A. Dai. Journal of Geophysical Research-Atmosphere. 6, D9, doi:.9/jd64 Vicente-Serrano, S.M. et al., (). Performance of Drought Indices for Ecological, Agricultural, and Hydrological Applications. Earth Interactions. 6:. Beguería, S., et al. (4). Standardized Precipitation Evapotranspiration Index (SPEI) revisited: parameter fitting, evapotranspiration models, kernel weighting, tools, datasets and drought monitoring. International Journal of Climatology, 4:. Vicente-Serrano, S.M., Gerard Van der Schrier, Santiago Beguería, Cesar Azorin Molina, Juan-I. Lopez Moreno. Contribution of precipitation and reference evapotranspiration to drought indices under different climates. Journal of Hydrology. In press.

7 STANDARDIZED PRECIPITATION EVAPOTRANSPIRATION INDEX (SPEI) Beguería et al. (4): International Journal of Climatology. 4: 8 6 ZARAGOZA ET, y =.5 x - 5 VIGO P, y = -9. x mm. 8 6 ET a, y =.5 x P, y =.5 x W, y = -.7 x ET, y =.7 x ET a, y =.4 x - 54 W, y =. x

8 STANDARDIZED PRECIPITATION EVAPOTRANSPIRATION INDEX (SPEI) ZARAGOZA SPEI Standardized (P-ETa) Standardized (ETa-PET) VIGO SPEI Standardized (P-ETa) Standardized (ETa-PET) Beguería et al. (4): International Journal of Climatology

9 ADVANTAGES IN COMPARISON TO OTHER INDICES The SPEI solves the problems of spatial comparability of the PDSI. Vicente-Serrano, S.M., et al. (). Journal of Hydrometeorology. : 4

10 ADVANTAGES IN COMPARISON TO OTHER INDICES GRIDDED DATA OBSERVATORIES C) Corr. RDI vs. P 4 R = Average P I) Corr. SPEI vs. ETo D) Corr. PDSI vs. P J) Corr. RDI vs. P R =. R = E) Corr. PDSI vs. ETo Average ETo Average ETo Average ETo L) Corr. SPDI vs. ETo R = R = K) Corr. PDSI vs. ETo. R = Desv. ETo Corr. PDSI vs. ETo Corr. SPDI vs. ETo. -. R =.5. F) Corr. SPDI vs. ETo.. Desv. P.4.4 R = Average ETo Corr. SPDI vs. ETo Corr. RDI vs. P Corr. PDSI vs. P.9 Corr. SPEI vs. ETo.8.95 Corr. RDI vs. P -.6 Average P. Corr. PDSI vs. ETo Average P Average P R = R =.49 R = Corr. SPEI vs. ETo.9 Corr. SPEI vs. P Corr. SPEI vs. ETo Corr. SPEI vs. P H) Corr. SPEI vs. ETo G) Corr. SPEI vs. P B) Corr. SPEI vs. ETo A) Corr. SPEI vs. P R = Desv. ETo Vicente-Serrano, S.M., Gerard Van der Schrier, Santiago Beguería, Cesar Azorin Molina, Juan-I. Lopez Moreno. Contribution of precipitation and reference evapotranspiration to drought indices under different climates. Journal of Hydrology. In press Desv. ETo 4

11 ADVANTAGES IN COMPARISON TO OTHER INDICES Vicente-Serrano, S.M., et al. () Performance of drought índices for ecological, agricultural and hydrological applications. Earth Interactions 6, 7.

12 ADVANTAGES IN COMPARISON TO OTHER INDICES Correlation Correlation SPI SPEI PDSI PHDI Z WPLM -. SPI SPEI PDSI PHDI Z WPLM CONTINUOUS JAN. FEB. MAR. APR. MAY. JUN. JUL. AUG. SEP. OCT. NOV. DEC. SPI SPEI PDSI PHDI Z-Index WPLM DROUGHT INDEX April. May June July August September October SPI SPEI PDSI PHDI Z WPLM Vicente-Serrano, S.M., et al. () Performance of drought índices for ecological, agricultural and hydrological applications. Earth Interactions 6, 7.

13 RECOMMENDATIONS TO CALCULATE THE SPEI.4 A) Plotting Position Probability Weighted Moments Standard deviation SPEI time-scale.4 B) Unbiased Probability Weighted Moments Standard deviation SPEI time-scale Beguería et al. (4): International Journal of Climatology. 4:

14 RECOMMENDATIONS TO CALCULATE THE SPEI Radiative Aerodinamic

15 RECOMMENDATIONS TO CALCULATE THE SPEI ETo (mm) ETo (mm) ETo (mm) ETo (mm) 4 8 January April July February May August October ETo (mm) November Annual March Vicente-Serrano, S.M., et al. (4). Sensitivity of reference evapotranspiration to changes in meteorological parameters in Spain (96). Water Resources Research June September December Annual ET Vicente-Serrano, S.M., et al (4). Reference evapotranspiration variability and trends in Spain, 96. Global and Planetary Change. Penman-Monteith Thornthwaite Hargreaves Hargreaves-Precip. Linacre Blaney-Criddle Kharrufa Priestley-Taylor FAO-Blan.-Crid. Turc Papadakis Radiation Annual Winter Spring Summer Autumn Penman-Montheith Thornthwaite Hargreaves Hargreaves-pp Linacre Blaney-Criddle Kharrufa Priestley-Taylor FAO-Blaney-Criddle Turc Papadakis Radiation

16 RECOMMENDATIONS TO CALCULATE THE SPEI Beguería et al. (4): International Journal of Climatology. 4: SPEI - (Th) SPEI SPEI - (Hg) (Pm) SPEI - (Hg-Th) SPEI - (Pm-Th) SPEI - (Pm-Hg)

17 RECOMMENDATIONS TO CALCULATE THE SPEI

18 RECOMMENDATIONS TO CALCULATE THE SPEI

19 RECOMMENDATIONS TO CALCULATE THE SPEI

20 RECOMMENDATIONS TO CALCULATE THE SPEI