In this Section:

	Background
	Project Overview
	Project Components:
	Physical Characteristics
	Social Vulnerability
	Impacts
	Monitoring
	References
	Related Links
	Contacts

Colorado River near Lake Powell in March 2002 (top) and March 2003 (bottom).
Credit: John Dohrenwend

Research and Products:
Drought Planning and Mitigation

Physical Characteristics

Overview | Research Methods | Results

Overview

CLIMAS researchers are analyzing drought patterns over time and space to better understand past events, to provide reports of current conditions, and to forecast future climate patterns for stakeholders. Analysis of historical drought includes looking at instrumental atmospheric and hydrologic data from the past century in the Southwest. In addition, CLIMAS paleoclimate research provides insight into prehistoric drought occurrence by reconstructing winter precipitation for the Southwest. More frequent droughts affect different topographic areas or smaller portions of the state, so it is important to understand drought events at many scales. More frequent droughts affect different topographic areas or smaller portions of the state, so it is important to understand drought events at many scales.

Historical and current drought information synthesized by CLIMAS researchers provides part of the background necessary for drought planning. CLIMAS also provides “one stop shopping” for up-to-date climate information, including drought information, through the monthly Southwest Climate Outlook.

Figure 3. Water-year precipitation average (inches) for Arizona climate divisions, 1896–2002. Link to the interactive map for full water-year precipitation data.[more details]

Research Methods

In order to provide a preliminary picture of drought variations across Arizona, CLIMAS researchers compiled and analyzed historical NOAA climate division data for the period, 1895 to 2002 (Figure 3). Water year (October–September) precipitation data and drought indices such as the Palmer Drought Severity Index and the Standardized Precipitation Index were analyzed in order to describe drought severity and variability and their spatial patterns across the state. These data were then compared with indices that measure large-scale atmospheric circulation patterns associated with multi-year variations in Pacific Ocean circulation, such as the Southern Oscillation Index and Pacific Decadal Oscillation. These measures reflect assorted qualities of drought on varied, but overlapping, time-scales. Each portrays drought severity, duration, and extent in a slightly different way.

In addition, each month, the Southwest Climate Outlook packet looks at drought at the local, regional, state, and national scale in order to provide a comprehensive depiction of current and forecasted conditions. It combines climate, water resources, and fire maps and data from national and state level institutions, with news highlights, interpretation and expert assessment of these products as they pertain to Arizona and New Mexico. Graphics illustrate climate trends for the region, as well as for discrete sites, and offer another tool to resource managers and decisionmakers.

Results

Figure 4. Southwest Climate Outlook. [more details]

A report and drought fact sheets have been produced to aid decision makers as they prepare for drought. An initial drought assessment,“Drought and Climate in Arizona: Top Ten Questions & Answers (PDF 744 KB)" provides lawmakers and the lay public with questions and answers about major climate-related aspects of drought including history, long-term averages, seasonality, interannual and long-term spatial and temporal variability, climate extremes, and climatic forcing. For example, this study revealed that the El Niño-Southern Oscillation connection with drought is stronger in southern Arizona than elsewhere in the state. Another key finding is that year-to-year precipitation variability in Arizona was highest between around 1930-1965, and that this variability has been increasing, again, in recent years.

While the historical drought information reveals trends over time, the Southwest Climate Outlook provides up-to-date information each month. Online access makes current climate summary information and forecasts widely accessible, and CLIMAS researchers plan to improve the system further by creating a web-access guide and a weblink database designed to aid users in locating information on drought and future conditions.

Ongoing research includes historical analysis, at the climate-division level, for the Upper Colorado River Basin region, which will yield results similar to Arizona's "Top Ten" list.The Upper Colorado River Basin region provides water to Arizona's Colorado River communities, as well as to agricultural and urban water users connected to the Central Arizona Project. Future work will examine drought variations at spatial scales within climate divisions, and the accuracy with which combinations of drought indices can be used to predict drought impacts.