NCDC added Alaska climate divisions to its nClimDiv dataset on Friday, March 6, 2015, coincident with the release of the February 2015 monthly monitoring report. For more information on this data, please visit the Alaska Climate Divisions FAQ.
- A file containing the national monthly percent area severely
dry and wet from 1900 to present is available for the severe to extreme and moderate to extreme categories.
- Historical temperature, precipitation, and Palmer drought data
from 1895 to present for climate divisions, states, and regions in
the contiguous U.S. are available at the Climate Division:
Temperature-Precipitation-Drought Data page in files having
names that start with "drd964x" and ending with "txt" (without the
|By the end of July, the
area of drought covered the Plains from the Rockies eastward to the
Midwest and the South from Arizona to the Atlantic Ocean (August 1 Drought
Monitor). In the drought areas, soil
moisture was low, streamflow
was especially low in the northern and central Plains and the
Southeast, and vegetative
health was poor.
Coupled with very dry conditions were high temperatures
in the drought stricken areas.
Drought and high temperatures impacted many sectors of the economy.
Crops were highly stressed or dying, livestock was dying or
prematurely sold because of a lack of feed and water, water
restrictions were common in many areas, and wildlife in search of
food and water was reported in urban areas. Disaster conditions
have been declared by the governors of several states. Dry
conditions also led to dozens of
fires in the western half of the country. Drought impacts have
been collected and summarized by county at the National Drought
Drought Impact Reporter.
Cracked soil in Iowa (photo courtesy of Dave Reinig, Little Sioux,
Severely stressed Iowa corn field (photo courtesy of Dave Reinig,
Little Sioux, Iowa)
The July precipitation pattern at the primary stations in Alaska
was below normal in most of the southern part of the state. In
the precipitation pattern was dry throughout the State. In Puerto
Rico, the month was predominantly dry in the central and
western interior areas, based on National
Weather Service radar estimates of precipitation.
Some regional highlights:
- Several states experienced the tenth percentile of
precipitation, or drier, multi-month seasons (May-July,
soil moisture conditions, based on model computations (CPC-1,
MRCC), were drier than normal across the Plains and South. At
depth, soil moisture
west of the Mississippi River continued much below normal.
- Low streamflows,
as computed by models and based on USGS observations,
continued in the Southeast westward and northward into the
State/Regional/National Moisture Status
July 2006 Paleoclimatic Analysis for Northeast
|The graph below
(annual values in light blue, 5-year weighted average in dark blue)
shows the annual (August-July) precipitation, 1896-2006, for
Wyoming Division 6. The value for 2006 (13.22") is only the 20th
lowest since 1896, but it marks the seventh year in a row with
below-normal precipitation. The most persistent drought, however,
was the Dust Bowl, with 12 years of below-normal precipitation
(1929-1940), including the lowest
60-month total precipitation (1934-1938; indicated with yellow
arrow) on record. The second-lowest 60-month total is the current
drought, 2002-2006 (orange arrow).
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larger image (200
|The graph to the left
also shows a 388-year tree-ring record (1603-1990; annual values in
light red; 5-year smoothed values in dark red) that corresponds
well to the variability in August-July precipitation. This record
is the average of three tree-ring chronologies (Douglas-fir and
ponderosa pine) from Wyoming, South Dakota, and North Dakota. The
correlation between the annual values of the tree-ring record and
August-July precipitation is 0.671, indicating a high degree of
shared variance. The tree-ring record captures the multi-year
variability of the observed precipitation record particularly
|The tree-ring record,
as a proxy for precipitation, can put the persistent droughts of
the last century in northeastern Wyoming into a much longer
perspective. There are four 5-year periods in the tree-ring record
(red arrows) with average ring-width anomalies similar to that for
1934-1938, suggesting that those periods were droughts of similar
severity to the worst part of the Dust Bowl, and by extension,
similar to the current drought. The most severe of these
paleodroughts, judging from the ring-width anomalies, was from
1756-1760. But no paleodrought appears to match the overall
persistence of the Dust Bowl years. The current drought, like the
Dust Bowl, appears to be among the worst multi-year droughts of the
past 400 years.
- Sieg, C. H., Meko, D., DeGaetano, A. T., and Ni, W. 1996.
"Dendroclimatic potential in the Northern Great Plains." Pages
295-302 in J. S. Dean, D. M. Meko, and T. W. Swetnam, Eds.,
Tree Rings, Environment and Humanity. Tucson: