US Drought Research Articles

Western US droughts: Climate happens

Western US droughts: Climate happens

Low frequency drought variability associated with climate indices

The variability in the sea surface temperature (SST) in the Pacific Ocean has an influence on the variability of the continental US precipitation, streamflow and drought. Analysis of the dominant oscillations of droughts and large-scale climate indices shows that interannual and interdecadal variations related to climate indices are significant indicators of drought occurrences. Using wavelet transforms and cross-correlations and Kriging, spatial structure of teleconnections of both El Niño Southern oscillation (ENSO) and Pacific decadal oscillation (PDO) to droughts during the 20th century is investigated, with particular reference to the state of Texas. Each region in Texas has different responses but arid regions show stronger correlations to climate anomalies than do sub-tropic humid regions. Lag times and correlation coefficients between droughts and climate indices are detected. Maps indicating the spatial variations of lag times and correlation coefficients are presented for annual and decadal scales. The proposed investigation permits to determine lag times between drought characteristics and climate indices along with significant correlations; these features are different from those of existing methods. Decision makers in the field of water resources management and agriculture can benefit from the evaluation of the ENSO variability and drought variability.

Characteristics of US drought and pluvials from a high‐resolution spatial dataset

AbstractAnomalous precipitation can be a devastating natural disaster having significant impacts on economies, society and the environment. This study examines the spatial and temporal characteristics of anomalous precipitation throughout the United States to obtain a greater understanding of drought/pluvial regimes, including intensity, duration and spatial coverage based on a high‐resolution precipitation dataset. With the help of the parameter‐elevation regression on independent slopes model (PRISM), approximately 4 km data for the United States is used to construct the Palmer drought severity index (PDSI) and the standardized precipitation index (SPI) for the period 1895–2003. Increased resolution from the PRISM dataset shows that drought/pluvial areas are not as homogeneous as seen in previous studies based on climate divisions and larger scales. While size, duration and locations of drought/pluvial events are influenced by the index used, the largest annual drought/pluvial events occur more frequently in the central United States, with a higher percentage of extreme values occurring in the western portion of the country. Four large pluvial events have occurred in the United States during the study period, with three of these having occurred during the past 30 years. Copyright © 2007 Royal Meteorological Society

Food costs and the 1988 US drought: An assessment of stock policies

Alternative government stock policies are evaluated in terms of their effects on the US livestock sector and consumer food prices before and after the 1988 drought using a comprehensive model of the US agricultural sector. Stock levels associated with the Food Security Act of 1985 (FSA85) are compared with those of a reduced-stock policy. This option reduced government corn stocks to zero and lowered overall stocks by almost 2 million bushels prior to the drought, saving taxpayers about $15 billion compared to the observed level of spending associated with FSA85. However, consumers were projected to spend almost $40 billion more following the drought in higher food (particularly meat) costs because of the dramatic shock lower corn stocks would have on corn prices and the livestock sector.

The 1988 US drought linked to anomalous sea surface temperature

THE 1988 drought in the United States has been widely reported, not least as an indicator of the reality of the "greenhouse effect"—see for example ref. 1. On the other hand, drought is a naturally occurring phenomenon. Here we have studied 30-day forecasts of the atmospheric flow over the United States using a complex numerical weather-prediction model initialized with data from May 1987 and May 1988. In addition, an experiment with 1988 initial conditions and 1987 sea surface temperatures was made. The results indicate that much of the difference between the 1987 and 1988 forecasts was associated with interannual variability in sea surface temperature. These results provide complementary evidence to that in ref. 2, which suggested that the US drought was linked to anomalous oceanic conditions in the tropical Pacific.

Landsat keeps an eye on continuing US drought

Landsat keeps an eye on continuing US drought

Heated response to US drought

Heated response to US drought

The 20-yr cycle in Greenland ice core records

CLIMATIC oscillations with a period of ∼20 yr have been reported in North American winter temperature records1,2 midwestern US drought indicators (ref. 3 and J. M. Mitchell, Jr personal communication), dendrochronological data4, and sea-surface temperature anomalies5. These oscillations have mostly been attributed to double sunspot cycles, which seem to occur at about 22-yr intervals. Other possible causes include an 18.6-yr modulation of the diurnal and semidiurnal lunar tidal forces5. Critics6,7 of these observations argue that such oscillations may only be an artefact of a red noise record, and are not uniformly present in a wide range of climatic data. It has also been argued that even if the oscillations are significant, their small amplitude renders them relatively unsuitable for climatic prediction1. However, if such oscillations prove to be real, identifying their nature and possible causes, even though their amplitude is small, can enhance our understanding of climatic change. To gain more insight into such 20-yr oscillations, we have examined characteristic oscillations in Greenland ice core oxygen isotope records. The results show that the strongest spectral peak occurs at a period of 20±0.5 yr with a statistically significant amplitude. This period is essentially the same as that found in eastern North American winter temperatures1. Moreover this 20-yr oscillation is found to be coherent in phase with the dominant variation in the Sun's motion about the centre of mass of the Solar System. This motion has been hypothesised8 to be closely linked with sunspots. On the basis of these observations we speculate here that a 20-yr oscillation may be a more fundamental solar and/or climatic oscillation than the nominal 22-yr cycle often mentioned.