|The Instrumental Record
Instrumental records of drought (observed data measured by weather monitoring instruments) are a
valuable resource which help detect the onset of drought. Although scientists have not yet refined
drought prediction skills, these instrumental data provide us with information on current and developing
droughts. The instrumental records also give us a picture of the short-term behavior (less than 100
years) and spatial patterns of drought, helping scientists learn more about the character of droughts.
Actual observed data are important in paleoclimatic studies because they enable the calibration of the
instrumental data with proxy data, a process needed to generate reconstructions of climate from proxy
data, and also allow us to determine how accurately different proxy records reconstruct climate.
Varying Patterns of 20th Century Drought:
Maps of drought extent and discussion of several major droughts in the 20th Century.
The Changing Relationships between El Nino/Southern Oscillation
(ENSO) Variability and Moisture Balance in the Continental United States:
Variations in the
El Nino/Southern Oscillation (ENSO)
in the equatorial Pacific are accompanied by changes
in atmospheric flow and pressure systems in mid-latitudes.
These changes, in turn, affect climate across North America,
especially in winter. Thus, certain phases of ENSO can increase
the likelihood of more unusual and/or persistent weather conditions,
such as drought, in some areas. For example, during El Nino,
winters are wetter from California to the southeastern United States,
while unusually warm conditions tend to persist from Alaska south
through southwestern Canada and eastward to the Great Lakes.
During La Nina, drought conditions are likely across the southwestern
and southeastern U.S. while the northwestern U.S. can experience
unusually wet winters, and cool conditions persist in a broad band
from Alaska to western Canada and across the northern tier of the
U.S. "The Changing Relationships between El Nino/Southern Oscillation
(ENSO) Variability and Moisture Balance in the Continental United States"
is an animation that illustrates these how these relationships change over time.
Links to other web sites with information on current and
developing climate and drought conditions in
the United States:
- The Drought Monitor:
This web page is sponsored by the U.S. Department of Agriculture, NOAA and the National Drought
Mitigation Center. It includes the National Drought Summary (summary of current and developing
droughts), current conditions, drought forecasts for the United States, and links to information on
NOAA Climate Diagnostics Center:
The mission of CDC is to identify the nature and causes of climate
variations on time scales ranging from a month to centuries.
The goal of this work is to develop the
ability to predict important climate
variations on these time scales. The CDC web pages contains much
online climate data, as well as a
suite of interactive web pages on
ENSO climate risks (temperature and precipitation)
in the United States,
other climate relationships ,
and global climate associated with
ENSO extremes since 1948.
Global monthly PDSI data from 1860 to present
can also be plotted as maps by selecting, under
"Which Variable," the Palmer Drought Index.
NOAA Climate Prediction Center
The goal of this site is to provide continuous monitoring of short-term climate fluctuations, including
diagnosis and prediction for agencies both inside and outside the federal government in coping with
such climate related problems as food supply, energy allocation, and water resources. Both PDSI and
precipitation data are available, as well as information on
ENSO and its impacts on North American climate.
Links to web sites from which drought and climate data can be obtained:
Back to... The Data.
Standard Precipitation Index
This web page allows users to obtain data for U.S. climate divisions for the
latest complete month and
for up to 72 months prior to the last complete month.
Variables include: accumulated precipitation,
accumulated precipitation departures from normal,
percent of average precipitation, precipitation
percentile, and standardized precipitation index.
This web page is generated by the Western Regional
Climate Center (WRCC).
Online Climate Data from NOAA's National Climatic Data Center (NCDC)
This web site provides viewing and downloading of online climate data,
including surface data (graphs, climatology and events, hourly, daily, monthly,
and modeled data), upper air data, marine data, and current conditions.