Statistics of multi‐year droughts from the method for object‐based diagnostic evaluation

This study uses the Method for Object-based Diagnostic Evaluation (MODE) technique to examine and compare the statistics of drought attributes over the upper Colorado River basin (UCRB). The drought objects are based on the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) on a 36-month timescale (SPI36 and SPEI36, respectively). The drought indicators are calculated using monthly precipitation as well as minimum and maximum temperatures from the Precipitation- Elevation Regression on Independent Slopes Model datasets from 1948 to 2012. MODE uses paired object attributes such as centroid distance, orientation angle, area ratio, and intersection area and a combination of parameter thresholds to determine the number of objects identified and retained in the merging and matching process in the two fields. Using MODE run with convolution radius of 0 (no smoothing) and an area threshold of 4 grid points, this study computes and analyzes object statistics including centroid locations, areas and intensity percentiles. Results of the analysis show that SPI36 produces more drought objects than SPEI36. Although the spatial patterns are roughly similar leading up to almost similar statistics of object attributes, such as locations of the object centroids, the SPI36 produces higher percentile intensity of drought objects than does SPEI36, which is clearly obvious in the 90th percentile intensity of drought objects. The largest difference between SPEI36 and SPI36 occurs in the area of drought objects during the early 2000s when the region experienced multi-year drought resulting from increased warming of the atmosphere. This study demonstrates the use of MODE as a tool to evaluate and monitor drought event over the UCRB.This is the peer reviewed version of the following article: Abatan, Abayomi A., William J. Gutowski Jr, Caspar M. Ammann, Laurna Kaatz, Barbara G. Brown, Lawrence Buja, Randy Bullock, Tressa Fowler, Eric Gilleland, and John Halley Gotway. "Statistics of multi‐year droughts from the method for object‐based diagnostic evaluation." International Journal of Climatology 38, no. 8 (2018): 3405-3420, which has been published in final form at doi: 10.1002/joc.5512. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.</p

Statistics of multi‐year droughts from the method for object‐based diagnostic evaluation

This study uses the Method for Object-based Diagnostic Evaluation (MODE) technique to examine and compare the statistics of drought attributes over the upper Colorado River basin (UCRB). The drought objects are based on the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) on a 36-month timescale (SPI36 and SPEI36, respectively). The drought indicators are calculated using monthly precipitation as well as minimum and maximum temperatures from the Precipitation- Elevation Regression on Independent Slopes Model datasets from 1948 to 2012. MODE uses paired object attributes such as centroid distance, orientation angle, area ratio, and intersection area and a combination of parameter thresholds to determine the number of objects identified and retained in the merging and matching process in the two fields. Using MODE run with convolution radius of 0 (no smoothing) and an area threshold of 4 grid points, this study computes and analyzes object statistics including centroid locations, areas and intensity percentiles. Results of the analysis show that SPI36 produces more drought objects than SPEI36. Although the spatial patterns are roughly similar leading up to almost similar statistics of object attributes, such as locations of the object centroids, the SPI36 produces higher percentile intensity of drought objects than does SPEI36, which is clearly obvious in the 90th percentile intensity of drought objects. The largest difference between SPEI36 and SPI36 occurs in the area of drought objects during the early 2000s when the region experienced multi-year drought resulting from increased warming of the atmosphere. This study demonstrates the use of MODE as a tool to evaluate and monitor drought event over the UCRB.This is the peer reviewed version of the following article: Abatan, Abayomi A., William J. Gutowski Jr, Caspar M. Ammann, Laurna Kaatz, Barbara G. Brown, Lawrence Buja, Randy Bullock, Tressa Fowler, Eric Gilleland, and John Halley Gotway. "Statistics of multi‐year droughts from the method for object‐based diagnostic evaluation." International Journal of Climatology 38, no. 8 (2018): 3405-3420, which has been published in final form at doi: 10.1002/joc.5512. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.</p

Multiyear Droughts and Pluvials over the Upper Colorado River Basin and Associated Circulations

This study analyzes spatial and temporal characteristics of multiyear droughts and pluvials over the southwestern United States with a focus on the upper Colorado River basin. The study uses two multiscalar moisture indices: standardized precipitation evapotranspiration index (SPEI) and standardized precipitation index (SPI) on a 36-month scale (SPEI36 and SPI36, respectively). The indices are calculated from monthly average precipitation and maximum and minimum temperatures from the Parameter-Elevation Regressions on Independent Slopes Model dataset for the period 1950–2012. The study examines the relationship between individual climate variables as well as large-scale atmospheric circulation features found in reanalysis output during drought and pluvial periods. The results indicate that SPEI36 and SPI36 show similar temporal and spatial patterns, but that the inclusion of temperatures in SPEI36 leads to more extreme magnitudes in SPEI36 than in SPI36. Analysis of large-scale atmospheric fields indicates an interplay between different fields that yields extremes over the study region. Widespread drought (pluvial) events are associated with enhanced positive (negative) 500-hPa geopotential height anomaly linked to subsidence (ascent) and negative (positive) moisture convergence and precipitable water anomalies. Considering the broader context of the conditions responsible for the occurrence of prolonged hydrologic anomalies provides water resource managers and other decision-makers with valuable understanding of these events. This perspective also offers evaluation opportunities for climate models.This article is published as Abatan, Abayomi A., William J. Gutowski Jr, Caspar M. Ammann, Laurna Kaatz, Barbara G. Brown, Lawrence Buja, Randy Bullock, Tressa Fowler, Eric Gilleland, and John Halley Gotway. "Multiyear Droughts and Pluvials over the Upper Colorado River Basin and Associated Circulations." Journal of Hydrometeorology 18, no. 3 (2017): 799-818. doi: 10.1175/JHM-D-16-0125.1. Posted with permission.</p

tutorial Thank You Support for MET is provided by the Developmental Testbed Center (DTC), NOAA and the Air Force Weather Agency (AFWA).Thank You The Verification Advisory Panel

– Set of verification tools for evaluating forecasts via • standard statistics • object-based methods • scale decompositions • Why? – Make verifiying easy. – Encourage verification. – Promote consistency across users. • How? – A (unix like) package of software tools and scripts. – Community contributed methods, graphics, etc. Student Introductions • Name • AffiliationShow of hands Who has used WRF? Who has used MET