Mark Svoboda

Monitoring the 1996 Drought Using the Standardized Precipitation Index

Abstract Droughts are difficult to detect and monitor. Drought indices, most commonly the Palmer Drought Severity Index (PDSI), have been used with limited success as operational drought monitoring tools and triggers for policy responses. Recently, a new index, the Standardized Precipitation Index (SPI), was developed to improve drought detection and monitoring capabilities. The SPI has several characteristics that are an improvement over previous indices, including its simplicity and temporal flexibility, that allow its application for water resources on all timescales. In this article, the 1996 drought in the southern plains and southwestern United States is examined using the SPI. A series of maps are used to illustrate how the SPI would have assisted in being able to detect the onset of the drought and monitor its progression. A case study investigating the drought in greater detail for Texas is also given. The SPI demonstrated that it is a tool that should be used operationally as part of a state, re...

The drought monitor

Abstract The Drought Monitor was started in spring 1999 in response to a need for improved information about the status of drought across the United States. It serves as an example of interagency cooperation in a time of limited resources. The Drought Monitor process also illustrates the creative use of Internet technologies to disseminate authoritativeinformation about drought and to receive regional and local input that is in turn incorporated into the product. This paper describes the Drought Monitor and the interactive process through which it is created.

The Lincoln Declaration on Drought Indices: Universal Meteorological Drought Index Recommended

What: Fifty-four participants from 22 countries, including drought experts from each of the six WMO regions, met to discuss the development of standards for drought indices and guidelines for drought early warning systems WheN: 8–11 December 2009 Where: Lincoln, Nebraska spoNsors: WMO; National Drought Mitigation Center (NDMC) and the School of Natural Resources (SNR), both at the University of Nebraska– Lincoln; NOAA/National Integrated Drought Information System; U.S. Department of Agriculture; and the United Nations Convention to Combat Desertification Secretariat I mproved drought monitoring and early warning systems are urgently needed to cope with current and potentially changing drought patterns as we move into the future. Drought is a slow-moving natural hazard that can affect virtually all climatic regimes. Generally defined, drought is a deficiency of precipitation relative to what is expected (i.e., “normal”) that, when extended over a season or a longer period of time, results in the inability to meet the demands of human activities and the environment. As countries around the world begin to establish national drought strategies, one critical component should be the development of a comprehensive drought monitoring system that has the ability to provide an early warning of the drought’s onset, determine drought severity and spatial extent, and convey that information to decision-making groups in a timely manner. This information can then be used to either reduce or avoid the impacts of drought. With this in mind, drought experts from nearly two dozen nations,1 including from all six regions of the World Meteorological Organization (WMO), were brought together for the Inter-Regional Workshop on Indices and Early Warning Systems for Drought, which was a four-day workshop focused on developing standards for drought indices and guidelines for drought early warning systems (DEWS). The motivation behind this workshop came out of the primary recommendations from the February 2009 International Workshop on Drought and Extreme Temperatures in Beijing, China, where one of the main recommendations was for the WMO to identify AFFILIATIONS: hayes, svoboda, Wall, aNd WidhalM—National Drought Mitigation Center, University of Nebraska–Lincoln, Lincoln, Nebraska CORRESPONDING AUTHOR: Nicole Wall, 819 Hardin Hall, National Drought Mitigation Center, University of Nebraska– Lincoln, Lincoln, NE 68583 E-mail: nwall2@unl.edu

An Intercomparison of Drought Indicators Based on Thermal Remote Sensing and NLDAS-2 Simulations with U.S. Drought Monitor Classifications

AbstractComparison of multiple hydrologic indicators, derived from independent data sources and modeling approaches, may improve confidence in signals of emerging drought, particularly during periods of rapid onset. This paper compares the evaporative stress index (ESI)—a diagnostic fast-response indicator describing evapotranspiration (ET) deficits derived within a thermal remote sensing energy balance framework—with prognostic estimates of soil moisture (SM), ET, and runoff anomalies generated with the North American Land Data Assimilation System (NLDAS). Widely used empirical indices based on thermal remote sensing [vegetation health index (VHI)] and precipitation percentiles [standardized precipitation index (SPI)] were also included to assess relative performance. Spatial and temporal correlations computed between indices over the contiguous United States were compared with historical drought classifications recorded in the U.S. Drought Monitor (USDM). Based on correlation results, improved forms for...

Toward global drought early warning capability: Expanding international cooperation for the development of a framework for monitoring and forecasting

Drought is a global problem that has far-reaching impacts, especially on vulnerable populations in developing regions. This paper highlights the need for a Global Drought Early Warning System (GDEWS), the elements that constitute its underlying framework (GDEWF), and the recent progress made toward its development. Many countries lack drought monitoring systems, as well as the capacity to respond via appropriate political, institutional, and technological frameworks, and these have inhibited the development of integrated drought management plans or early warning systems. The GDEWS will provide a source of drought tools and products via the GDEWF for countries and regions to develop tailored drought early warning systems for their own users. A key goal of a GDEWS is to maximize the lead time for early warning, allowing drought managers and disaster coordinators more time to put mitigation measures in place to reduce the vulnerability to drought. To address this, the GDEWF will take both a top-down approach...

Beginning a New Era of Drought Monitoring Across North America

A cooperative, multinational effort to improve the monitoring and assessment of climate extremes.

Examining Rapid Onset Drought Development Using the Thermal Infrared–Based Evaporative Stress Index

AbstractReliable indicators of rapid drought onset can help to improve the effectiveness of drought early warning systems. In this study, the evaporative stress index (ESI), which uses remotely sensed thermal infrared imagery to estimate evapotranspiration (ET), is compared to drought classifications in the U.S. Drought Monitor (USDM) and standard precipitation-based drought indicators for several cases of rapid drought development that have occurred across the United States in recent years. Analysis of meteorological time series from the North American Regional Reanalysis indicates that these events are typically characterized by warm air temperature and low cloud cover anomalies, often with high winds and dewpoint depressions that serve to hasten evaporative depletion of soil moisture reserves. Standardized change anomalies depicting the rate at which various multiweek ESI composites changed over different time intervals are computed to more easily identify areas experiencing rapid changes in ET. Overal...

Examining the Relationship between Drought Development and Rapid Changes in the Evaporative Stress Index

AbstractIn this study, the ability of a new drought metric based on thermal infrared remote sensing imagery to provide early warning of an elevated risk for drought intensification is assessed. This new metric, called the rapid change index (RCI), is designed to highlight areas undergoing rapid changes in moisture stress as inferred from weekly changes in the evaporative stress index (ESI) generated using the Atmosphere–Land Exchange Inverse (ALEXI) surface energy balance model. Two case study analyses across the central United States revealed that the initial appearance of negative RCI values indicative of rapid increases in moisture stress preceded the introduction of severe-to-exceptional drought in the U.S. Drought Monitor (USDM) by more than 4 weeks. Using data from 2000 to 2012, the probability of USDM intensification of at least one, two, or three categories over different time periods was computed as a function of the RCI magnitude. Compared to baseline probabilities, the RCI-derived probabilities...

Multi-GCM projections of future drought and climate variability indicators for the Mediterranean region

Abstract Future climate conditions for the Mediterranean region based on an ensemble of 16 Global Climate Models are expressed and mapped using three approaches, giving special attention to the intermodel uncertainty. (1) The scenarios of mean seasonal temperature and precipitation agree with the projections published previously by other authors. The results show an increase in temperature in all seasons and for all parts of the Mediterranean with good intermodel agreement. Precipitation is projected to decrease in all parts and all seasons (most significantly in summer) except for the northernmost parts in winter. The intermodel agreement for the precipitation changes is lower than for temperature. (2) Changes in drought conditions are represented using the Palmer Drought Severity Index and its intermediate Z-index product. The results indicate a significant decrease in soil moisture in all seasons, with the most significant decrease occurring in summer. The displayed changes exhibit high intermodel agreement. (3) The climate change scenarios are defined in terms of the changes in parameters of the stochastic daily weather generator calibrated with the modeled daily data; the emphasis is put on the parameters, which affect the diurnal and interdiurnal variability in weather series. These scenarios indicate a trend toward more extreme weather in the Mediterranean. Temperature maxima will increase not only because of an overall rise in temperature means, but partly (in some areas) because of increases in temperature variability and daily temperature range. Increased mean daily precipitation sums on wet days occurring in some seasons, and some parts of the Mediterranean may imply higher daily precipitation extremes, and decreased probability of wet day occurrence will imply longer drought spells all across the Mediterranean.

Application of USDM statistics in NLDAS-2: Optimal blended NLDAS drought index over the continental United States

This study performs three experiments to calibrate the drought area percentages in the continental United States (CONUS), six U.S. Drought Monitor (USDM) regions, and 48 states downloaded from the USDM archive website. The corresponding three experiments are named CONUS, Region, and State, respectively. The data sets used in these experiments are from the North American Land Data Assimilation System Phase 2 (NLDAS-2). The main purpose is to develop an automated USDM-based approach to objectively generate and reconstruct USDM-style drought maps using NLDAS-2 data by mimicking 10 year (2000–2009) USDM statistics. The results show that State and Region have larger correlation coefficients and smaller root-mean-square error (RMSE) and bias than CONUS when compared to the drought area percentages derived from the USDM, indicating that State and Region perform better than CONUS. In general, State marginally outperforms Region in terms of RMSE, bias, and correlation. Analysis of normalized optimal weight coefficients shows that soil moisture percentiles (top 1 m and total column) play the dominant role in most of the 48 states. The optimal blended NLDAS drought index (OBNDI) has higher simulation skills (correlation coefficient and Nash-Sutcliffe efficiency) in the South, Southeast, High Plains, and Midwest regions when compared to those in the West and Northeast. The highest simulation skills appear in TX and OK. By using optimal equations, we can reconstruct the long-term drought area percentages and OBNDI over the continental United States for the entire period of the NLDAS-2 data sets (January 1979 to present).