Drought

Status Update: 7 September 2011 (14:00 CEST)

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Recent drought events in the United States and the magnitude of drought losses indicate the continuing vulnerability of the country to drought. Until recently, drought management in many states, including Nebraska, has been largely response oriented with little or no attention to mitigation and preparedness. In 1998, Nebraska began to revise its drought plan in order to place more emphasis on mitigation. One of the main aspects of drought mitigation and planning is the assessment of who and what is vulnerable and why. This paper presents a method for spatial, Geographic Information Systems-based assessment of agricultural drought vulnerability in Nebraska. It was hypothesized that the key biophysical and social factors that define agricultural drought vulnerability were climate, soils, land use, and access to irrigation. The framework for derivation of an agricultural drought vulnerability map was created through development of a numerical weighting scheme to evaluate…

Drought is the most complex but least understood of all natural hazards. It is broadly defined as "severe water shortage". Low rainfall and fall in agricultural production has mainly caused droughts. A droughts impact constitutes losses of life, human suffering and damage to economy and environment. Drought have been a recurring feature of the Indian climate therefore study of Historical droughts may help in the delineation of major areas facing drought risk and thereby management plans can be formulated by the government authorities to cope with the disastrous effects of this hazard.

Remote sensing has proven useful for large-area vegetation monitoring given the synoptic coverage, high temporal repeat cycle, and continuous, moderate resolution observations of satellite-based sensors. In particular, time-series normalized difference vegetation index (NDVI) data from the global imager, the Advanced Very High Resolution Radiometer (AVHRR), has been widely used for vegetation and ecosystem monitoring (Tucker et al., 1985; Reed et al., 1994; Jakubauskas et al., 2002). Analysis of time-series NDVI data and NDVI-derived metrics have been an effective means for identifying vegetation condition anomalies (e.g., apparent declines in vegetation health). Operational efforts such as the Green Report (http://www.kars.ku.edu/products/greenreport.shtml), RangeView (http://rangeview.arizona.edu/), and the U.S. Forest Service’s Wildland Fire Assessment System (http://www.wfas.net/content/view/30/47/) provide NDVI-derived products that describe the percentage…

Droughts are normal recurring climatic phenomena that affect people and the landscapes they occupy at many scales (locally, regionally, and nationally) for periods of time varying from weeks to decades. The spatial and temporal variability and multiple impacts of droughts present challenges for mapping and monitoring on all scales.
Operational drought monitoring, by its very nature, requires repetitive measurements at the same location day after day, month after month, and year after year. Monitoring tools require reliable sources of time-series data at effective spatial and temporal scales to provide accurate and timely information. Satellite remote sensing is an obvious data source, supplying synoptic coverage of the land surface with objective, automated data collections for use in spatially specific models. Satellite information is especially appropriate over remote areas or areas with sparse field instrumentation.

Droughts are natural hazards with varying patterns in space, time, and intensity. Their dynamic character challenges our ability in planning, predicting, monitoring, and providing relief to affected areas. Because of the spatial and temporal variability and multiple impacts of droughts, we need to improve the tools and data available for mapping and monitoring this phenomenon on all scales. A team of researchers from the US Geological Survey’s EROS Data Center, the National Drought Mitigation Center, and the High Plains Regional Climate Center are developing methods for regional-scale mapping and monitoring drought conditions for the conterminous U.S. Currently in its first year, the project is focusing on developing a prototype model for the central U.S. The ultimate goal of the project is to deliver timely geo-referenced information (in the form of maps and data) about areas where the vegetation is impacted by drought, using the Internet as the primary delivery…

Desert ecosystems are characterised by large spatial and temporal variability mainly due to scarcity of moisture owing to insignificant precipitation. Desert vegetation is represented mostly by natural vegetation and least by agricultural crops. Desert plants are naturally adapted to hyper-arid climate where, rainfall is sparse and day-time temperature is very high. However, desert phenology is very sensitive to climatic parameters, particularly rainfall and temperature. Insufficient and erratic rainfall causes moisture-stress, whereas high heatflow imparts thermal-stress to vegetation. Due to higher sensitivity, slight decrease in rainfall and/or increase in temperature impart stresses on desert plants. Therefore, desert-plants suffer severely during intense droughts. Thar, the Great Indian Desert covers 446,000 km2 area in the north-western part of India and eastern part of Pakistan. The Indian portion of the Thar Desert covers 208,110 km2 area of which 61% lies in…

Northeast Thailand is the driest region in Thailand with a severe drought problem persisting for more than a decade. The impact of the drought on economy, environment and social well being is widely recognized and reported upon. Despite the importance of monitoring drought, most of previous studies have focused on drought risk and database creation. Therefore, to improve knowledge on vegetation response to precipitation at regional scale for drought monitoring, the objectives of this study were to determine the relationships between satellite-derived NDVI and rainfall over NE Thailand region, and to investigate the overall vegetation dynamics and inter-annual responses. Seven years (2000-06) of MODIS 16-day composite NDVI at 250m resolution and seven years (2000-06) of precipitation data from over 300 stations were used in this study. Spatial rainfall and NDVI anomalies as well as time lag relationships between rainfall and NDVI were analyzed. Results showed downward…

In this paper, drought status of northwestern China is evaluated using the Terra–Moderate Resolution Imaging Spectroradiometer (MODIS) data with a newly developed method called perpendicular drought index (PDI), which is defined as a line segment that is parallel with the soil line and perpendicular to the normal line of soil line intersecting the coordinate origin in the two-dimensional scatterplot of red against near infrared (NIR) wavelength reflectance. To validate the PDI in macroscale applications, quantitative evaluation of drought conditions inNingxia, Northwestern China is carried out by comparing the PDI with one ofthe well-known drought indexes, namely, temperature-vegetation index (TVX).Linear regression between ground-measured soil moisture data and the PDI andthe TVX was made. Results show that satellite based PDI and TVX hassignificant correlation with 0–20 cm averaged soil moisture obtained over themeteorological observing stations across…

This paper reports on the comparison of surface temperature and soil moisture observed by instruments onboard the Environmental Satellite (EnviSat) with simulations by an atmospheric circulation model over the period April 2005 to September 2007. The Naquriver basin has been selected as the study area, which is located on the eastern part of Tibetan Plateau. For the selected period, the PSU/NCAR meso scale model (referred to as MM5) has been employed in a coupled mode with NOAH LSm to simulate the soil moisture and surface temperature. Surface temperature and soil moisture have been retrieved from Advanced Along Track Scanning Radiometer (AATSR) and Advanced Synthetic Aperture Radar (ASAR) observations, respectively. Comparison of the simulated and satellite observed soil moisture and surface temperature showed that uncertainties in the simulated surface temperature and soil moisture are overall in agreement with each other, but are relatively large during spring and…