Global Drought Research Articles

International Drought Workshop Series

No Abstract available.

Historical and Projected Climate Trends Along the Appalachian Trail, USA, and the Implications for Trail Usage

Recent climate analyses indicate that average global temperature is rising and both global drought occurrence and precipitation intensity are increasing. The nature of climate change is unique to each location, and its impact, both positive and negative, is predicted to be widespread. One area to be potentially affected includes management and use of outdoor natural resources such as the Appalachian Trail (AT), a 3500 km continuous hiking trail in the eastern United States. Observed historical (1895-2008) and projected future (to 2099) seasonal temperature and precipitation trends were examined along the AT. The AT has generally warmed since 1895, with greater warming occurring more recently. The warming has been greatest in the northern part of the AT and during winter. Precipitation trends show wide spatial variation depending upon the season, but generally precipitation has increased more in the northern than southern AT. Temperature and precipitation are projected to increase for all regions during all seasons in the future. Implications of these changes are discussed with respect to hiker experience and trail management.

A Multiscalar Global Drought Dataset: The SPEIbase: A New Gridded Product for the Analysis of Drought Variability and Impacts

This work has been supported by the research projects CGL2008-01189/BTE and CGL2006-11619/HID, funded by the Spanish Commission of Science and Technology and FEDER; EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV-2007-1- 212250), funded by the VII Framework Programme of the European Commission; and “Las sequias climaticas en la cuenca del Ebro y su respuesta hidrologica” and “La nieve en el Pirineo aragones: Distribucion espacial y su respuesta a las condiciones climatica,” funded by “Obra Social La Caixa” and the Aragon Government.

A New Global 0.5° Gridded Dataset (1901–2006) of a Multiscalar Drought Index: Comparison with Current Drought Index Datasets Based on the Palmer Drought Severity Index

Abstract A monthly global dataset of a multiscalar drought index is presented and compared in terms of spatial and temporal variability with the existing continental and global drought datasets based on the Palmer drought severity index (PDSI). The presented dataset is based on the standardized precipitation evapotranspiration index (SPEI). The index was obtained using the Climatic Research Unit (CRU) TS3.0 dataset at a spatial resolution of 0.5°. The advantages of the new dataset are that (i) it improves the spatial resolution of the unique global drought dataset at a global scale; (ii) it is spatially and temporally comparable to other datasets, given the probabilistic nature of the SPEI; and, in particular, (iii) it enables the identification of various drought types, given the multiscalar character of the SPEI. The dataset is freely available on the Web page of the Spanish National Research Council (CSIC) in three different formats [network Common Data Form (netCDF), binary raster, and plain text].

Impact of Common Sea Surface Temperature Anomalies on Global Drought and Pluvial Frequency

Abstract Climate model simulations run as part of the Climate Variability and Predictability (CLIVAR) Drought Working Group initiative were analyzed to determine the impact of three patterns of sea surface temperature (SST) anomalies on drought and pluvial frequency and intensity around the world. The three SST forcing patterns include a global pattern similar to the background warming trend, a pattern in the Pacific, and a pattern in the Atlantic. Five different global atmospheric models were forced by fixed SSTs to test the impact of these SST anomalies on droughts and pluvials relative to a climatologically forced control run. The five models generally yield similar results in the locations of drought and pluvial frequency changes throughout the annual cycle in response to each given SST pattern. In all of the simulations, areas with an increase in the mean drought (pluvial) conditions tend to also show an increase in the frequency of drought (pluvial) events. Additionally, areas with more frequent extreme events also tend to show higher intensity extremes. The cold Pacific anomaly increases drought occurrence in the United States and southern South America and increases pluvials in Central America and northern and central South America. The cold Atlantic anomaly increases drought occurrence in southern Central America, northern South America, and central Africa and increases pluvials in central South America. The warm Pacific and Atlantic anomalies generally lead to reversals of the drought and pluvial increases described with the corresponding cold anomalies. More modest impacts are seen in other parts of the world. The impact of the trend pattern is generally more modest than that of the two other anomaly patterns.

Modeling the Recent Evolution of Global Drought and Projections for the Twenty-First Century with the Hadley Centre Climate Model

Abstract Meteorological drought in the Hadley Centre global climate model is assessed using the Palmer Drought Severity Index (PDSI), a commonly used drought index. At interannual time scales, for the majority of the land surface, the model captures the observed relationship between the El Niño–Southern Oscillation and regions of relative wetness and dryness represented by high and low values of the PDSI respectively. At decadal time scales, on a global basis, the model reproduces the observed drying trend (decreasing PDSI) since 1952. An optimal detection analysis shows that there is a significant influence of anthropogenic emissions of greenhouse gasses and sulphate aerosols in the production of this drying trend. On a regional basis, the specific regions of wetting and drying are not always accurately simulated. In this paper, present-day drought events are defined as continuous time periods where the PDSI is less than the 20th percentile of the PDSI distribution between 1952 and 1998 (i.e., on average 20% of the land surface is in drought at any one time). Overall, the model predicts slightly less frequent but longer events than are observed. Future projections of drought in the twenty-first century made using the Special Report on Emissions Scenarios (SRES) A2 emission scenario show regions of strong wetting and drying with a net overall global drying trend. For example, the proportion of the land surface in extreme drought is predicted to increase from 1% for the present day to 30% by the end of the twenty-first century.

Sequential Association Rule Mining with Time Lags

This paper presents MOWCATL, an efficient method for mining frequent association rules from multiple sequential data sets. Our goal is to find patterns in one or more sequences that precede the occurrence of patterns in other sequences. Recent work has highlighted the importance of using constraints to focus the mining process on the association rules relevant to the user. To refine the data mining process, this approach introduces the use of separate antecedent and consequent inclusion constraints, in addition to the traditional frequency and support constraints in sequential data mining. Moreover, separate antecedent and consequent maximum window widths are used to specify the antecedent and consequent patterns that are separated by either a maximal width time lag or a fixed width time lag. Multiple time series drought risk management data are used to show that our approach can be effectively employed in real-life problems. This approach is compared to existing methods to show how they complement each other to discover associations in the drought risk management domain. The experimental results validate the superior performance of our method for efficiently finding relationships between global climatic episodes and local drought conditions. Both the maximal and fixed width time lags are shown to be useful when finding interesting associations.

Progress in Breeding Wheat for Yield and Adaptation in Global Drought Affected Environments

The impact of wheat (Triticum aestivum L.) germplasm from the International Maize and Wheat Improvement Center (CIMMYT) in the highly productive environments of the developing world has been significant. However, 55% of the area sown to wheat in these countries is periodically affected by drought and the impact of CIMMYT germplasm on productivity in these areas is not dear. Our objective was to measure rates of yield improvement for the period 1979 through 1998 using yield data from CIMMYT's Elite Spring Wheat Trial (ESWYT) and Semi-Arid Wheat Yield Trial (SAWYT). The mean yield of the five highest yielding entries from each site was expressed as a percent of the trial mean (%TM). The trial mean yield (TM) and the mean yield of locally adapted check cultivars (LC) were used to provide estimates of the productivity of each environment. Measuring rates of progress by means of %TM, TM, and LC were favored to the use of mean yield alone as variable annual rainfall and subsequent fluctuations in productivity influence yield in dry environments. Yearly rates of progress were determined by measuring change in %TM and change in TM. In environments yielding less than 4 Mg ha -1 the respective increases in %TM and TM for SAWYT were 4.38 and 0.09% yr -1 . The equivalent rates for ESWYT were 0.34 and 0.19% yr -1 . In environments yielding 4 Mg ha -1 or more the respective rates of progress in %TM and TM for SAWYT were 0.85 and 2.87% yr -1 compared with 0.26 and 0.494% yr -1 observed in the ESWYT. Comparisons of %TM, TM, and LC for representative locations in Mexico, Argentina, Syria, and Portugal demonstrated progress in %TM ranging from highly significant to stable, regardless of local fluctuations in productivity.

Mike Davis, Late Victorian Holocausts: El Niño Famines and the Making of the Third World. London: Verso, 2001. 464 pp. $27.00 cloth

Three great global droughts, in 1876-1879, 1889-1891, and 1896-1900, afflicted much of the most populous part of the tropical world in the late nineteenth century. These droughts were the result of what we can now recognize as a more or less regular succession of mega-climatic events known as El Nino. These phenomena occurred previously, notably in the late eighteenth century, but the late nineteenth century events were extraordinarily severe, and death by starvation and disease was on a staggering, unprecedented scale. Estimates of the number who perished range from thirty-one million to sixty-one million people. The sheer magnitude of what can rightly be called a holocaust of non-Western peoples has generally been obscured by a persistent metropolitan perspective, by the social distance from mass suffering of colonial administrative elites and by historians incurious about, or dismissive of, such “cycles of Cathay.” It is a signal service of this impressive, eloquent study that the dimension of this human suffering on a global scale has been both exposed and foregrounded in the operation of late-Victorian formal and informal imperialisms.

Global drought and flood-watch from NOAA polar-orbitting satellites

Drought and flood are the most damaging environmental phenomenon. In a quarter of the century since 1967, droughts affected sixty and floods thirty percent of 2.8 billion people who suffered from weather-related disasters. Moreover, they were a cause of 1.6 million deaths from the total number of 3.5 million people killed by all disasters during 1967–1991. Since drought and flood cover large areas, it is difficult to monitor them using conventional systems. In recent years, the National Oceanic and Atmospheric Administration (NOAA) has designed a new AVHRR-based indices that have shown to be useful for detection and monitoring large area vegetation stress resulted from drought or soil oversaturation following flooding and excessive rains. These indices are Vegetation Condition Index (VCI), Temperature Condition Index (TCI) and their combination (V/TCI). These indices showed their excellent ability to detect vegetation stress due to drought and soil oversaturation and are useful in measuring time of onset, intensity, duration, and impact on vegetation of these phenomenon. This paper shows the principals of VCI/TCI application.

Global Drought Watch from Space

Abstract Drought is the most damaging environmental phenomenon. During 1967–91, droughts affected 50% of the 2.8 billion people who suffered from weather-related disasters. Since droughts cover large areas, it is difficult to monitor them using conventional systems. In recent years the National Oceanic and Atmospheric Administration has designed a new Advanced Very High Resolution Radiometer- (AVHRR) based Vegetation Condition Index (VCI) and Temperature Condition Index (TCI), which have been useful in detecting and monitoring large area, drought-related vegetation stress. The VCI was derived from the Normalized Difference Vegetation Index (NDVI), which is the ratio of the difference between AVHRR-measured near-infrared and visible reflectance to their sum. The TCI was derived from the 10.3–11.3-mm AVHRR-measured radiances, converted to brightness temperature (BT). Algorithms were developed to reduce the noise and to adjust NDVI and BT for land surface nonhomogeneity. The VCI and TCI are used to determine...

Observed variability in the thermal response of the upper North central Arabian Sea to the forcing of onset Vortex during summer monsoon experiments

Temperature data collected in the upper layers of the central Arabian Sea before and after the onset of the summer monsoon during the three monsoon experiments ISMEX-73 (1973), MONSOON-77 (1977) and MONEX-79 (1979) from stationary ships are made use of to document the observed variability in the upper ocean thermal structure with the onset of the monsoon. Cooling and deepening of the mixed layer and warming below the layer were found to be of unequal magnitudes under the influence of onset vortex during these three years. Similar differences were also noticed in the profiles of vertical thermal gradient. Absence of a secondary maximum in the vertical thermal gradient during 1973 suggests a weak summer monsoonal forcing during 1972, which was viewed as a global drought year. Large differences were noticed in the changes of accumulative heat content between 1973 and 1979 which were good and bad monsoon years respectively.

Preliminary investigations on the global summer monsoonal drought mechanics and the latitudinal teleconnections

The question of possible teleconnections between the middle latitude general circulation and the Indian south-west monsoon was investigated in this paper. Within the framework of a simple model it was shown that there can exist such an interaction via the ultra-long Rossby waves.