The study reported here was designed to examine the impact of background meteorological conditions on the propagation of noise from urban freeways in the Phoenix area. The aim was to understand and predict how sound waves emanating from highways respond to the vertical profiles of atmospheric temperature gradients and velocity shear, so that sound measurements can be interpreted with regard to the environmental variability.

The information presented here highlights the findings of a drought history study in support of the Governor's Drought Task Force activities, such as determining triggers for drought mitigation and response actions, based on observed hydroclimatic and other information. The material is intended to provide the relevant climatology background for non-specialists, and it is presented in a top ten or frequently asked question format. The questions and answers cover the major climate-related aspects of drought including long-term averages, seasonality, interannual and long-term spatial and temporal drought variations, extremes, and causes of climatic variability. The answers to each question include bulleted Quick Answers followed by a concise explanation of more detailed information. Example figures are presented within the text.