ERA‐40 reanalysis hydrological applications in the characterization of regional drought

The use of a land surface model (TESSEL) for drought characterization is proposed. The method is tested with the 1958–2001 ECMWF ERA‐40 reanalysis and its results are successfully compared with those obtained with other indices (SPI, PDSI) computed from observations in Iberia, a region highly vulnerable to drought. The proposed index, Normalized Soil Moisture (NSM), requires no local tuning, and, in principle, is readily computable from point observations, reanalysis, forecasts or climate scenarios. NSM from offline integrations has an enhanced consistency for drought analysis when compared with NSM computed directly from ERA‐40 soil moisture. Analysis of the NSM fields indicates that while the spatial heterogeneity of precipitation is the main driver of the spatial variability of drought, the spatial distribution of soil characteristics modulates its temporal variability. This suggests the need for better soil maps at the global scale.

[1]  H. Kaiser.  The varimax criterion for analytic rotation in factor analysis , 1958 .

[2]  T. McKee,et al.  THE RELATIONSHIP OF DROUGHT FREQUENCY AND DURATION TO TIME SCALES , 1993 .

[3]  Pedro Viterbo,et al.  An Improved Land Surface Parameterization Scheme in the ECMWF Model and Its Validation. , 1995 .

[4]  A. Robock,et al.  Scales of temporal and spatial variability of midlatitude soil moisture , 1996 .

[5]  N. Guttman.  COMPARING THE PALMER DROUGHT INDEX AND THE STANDARDIZED PRECIPITATION INDEX 1 , 1998 .

[6]  Pedro Viterbo,et al.  Impact of the ECMWF reanalysis soil water on forecasts of the July 1993 Mississippi flood , 1999 .

[7]  Jean-François Mahfouf,et al.  Evaluation of the Optimum Interpolation and Nudging Techniques for Soil Moisture Analysis Using FIFE Data , 2000 .

[8]  Pedro Viterbo,et al.  Impact of BOREAS on the ECMWF forecast model , 2001 .

[9]  R. Heim.  A Review of Twentieth-Century Drought Indices Used in the United States , 2002 .

[10]  B. Lloyd‐Hughes,et al.  A drought climatology for Europe , 2002 .

[11]  K. Trenberth,et al.  A Global Dataset of Palmer Drought Severity Index for 1870–2002: Relationship with Soil Moisture and Effects of Surface Warming , 2004 .

[12]  Venkat Lakshmi,et al.  Soil moisture as an indicator of weather extremes , 2004 .

[13]  A. Sterl,et al.  The ERA‐40 re‐analysis , 2005 .

[14]  D. Lettenmaier,et al.  Twentieth-Century Drought in the Conterminous United States , 2005 .

[15]  Pedro Viterbo,et al.  The European Summer of 2003: Sensitivity to Soil Water Initial Conditions , 2006 .

[16]  Sergio M. Vicente-Serrano,et al.  Differences in Spatial Patterns of Drought on Different Time Scales: An Analysis of the Iberian Peninsula , 2006 .

[17]  E. Wood,et al.  Characteristics of global and regional drought, 1950–2000: Analysis of soil moisture data from off‐line simulation of the terrestrial hydrologic cycle , 2007 .