Abstract
Drought index is a useful tool to assess and respond to drought. However, current drought indices could not fully reveal land use effects and they have limitations in applications. Besides, El Niño Southern Oscillation (ENSO), strongly influences the climate of Florida. Hence, understanding ENSO patterns on a regional scale and developing a new land use drought index suitable for Florida are critical in agriculture and water resources planning and management. This paper presents a 32 km high resolution land use adapted drought index, which relies on five types of land uses (lake, urban, forest, wetland, and agriculture) in Florida. The land uses were obtained from National Centers for Environmental Prediction (NCEP) North American Regional Reanalysis (NARR) data from 1979 to 2002. The results showed that Bowen ratio responded to land use and could be used as an indicator to monitor drought events. Then, an innovative regional land use drought index was developed from the normalized Bowen ratio, which could reflect not only the level of severity during drought events resulting from land use effects, but also La Niña driven drought impacts. The proposed new index may help scientists answer the critical questions about drought effect on various land uses and potential feedbacks of changes in land use and land cover to climate.
Highlights
When a large area over a period of time loses a significant amount of water without availability of replenishment, the area is said to be under drought condition [1]
In the United States, great efforts have been made to develop a variety of drought indices for water resources management, and agricultural drought monitoring and forecasting, including Palmer Drought Severity Index (PDSI) [4], Crop Moisture Index (CMI) [5], Standardized Precipitation Index (SPI) [6], and Surface Water Supply Index (SWSI) [7]
It is suggested that ET can consume up to 80% of rainfall according to general circulation model (GCM) simulations and has a substantial influence on drought condition, but such influence is difficult to validate due to limited observations [10,11]
Summary
When a large area over a period of time loses a significant amount of water without availability of replenishment, the area is said to be under drought condition [1]. In the United States, great efforts have been made to develop a variety of drought indices for water resources management, and agricultural drought monitoring and forecasting, including Palmer Drought Severity Index (PDSI) [4], Crop Moisture Index (CMI) [5], Standardized Precipitation Index (SPI) [6], and Surface Water Supply Index (SWSI) [7]. As current drought indices are calculated from climate data based on point measurements of meteorological stations, which are sparsely set up in remote areas and not uniformly distributed, their applications are subject to limitations and drawbacks. The more complex drought indices, PDSI and CMI, which are based on water balance model, assumed that parameters such as land use/land cover, and soil properties are uniform over the entire climatic zone (7000–100,000 km2) [12]. Improvements in current drought monitoring and forecasting techniques will allow better preparation, lead to better management practices, and mitigate the vulnerability of society to drought and its subsequent impacts
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