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.