NOAA REPORTS 2003 WAS MARKED BY CONTRASTING CONDITIONS ACROSS THE U.S. WHILE GLOBAL TEMPERATURES REMAIN HIGH
Dec. 16, 2003 — The 2003 climate in the United States was wetter and cooler-than-average in the East, warmer and drier-than-average in the West, while drought conditions persisted, or worsened, throughout much of the central and western regions, according to scientists at the NOAA Climatic Data Center in Asheville, N.C. Working from the world’s largest statistical weather database, the scientists also estimate that 2003 will likely be the third warmest year on record for the globe. (Click NOAA image for larger view of USA significant weather and climate events for 2003. Please credit “NOAA.”)
Precipitation and Drought
Conversely, 17 states along and west of the Mississippi River were significantly drier than average. The combination of below-average precipitation and warmer-than-average temperatures contributed to persistent or worsening drought conditions.
Near year’s end, moderate to extreme drought covered approximately 70 percent of 11 western states, a region where drought has persisted for the past three to five years in many locations. A major late winter storm that brought a near-record snowfall of 32 inches (81 cm) to Denver and totals exceeding 80 inches (203 cm) in higher elevation locations of the Front Range helped alleviate drought in parts of Colorado, but seasonal snowfall totals were well below average in much of the remainder of the West.
The persistent lack of adequate rain and snowfall left reservoirs throughout much of the West below average near the end of 2003, and the continuation of even moderate drought conditions has had an impact on water supplies. Lake Mead, an important reservoir in the Colorado River system, was approximately two-thirds of its total capacity near the beginning of summer, and summertime levels have been dropping since 1999.
However, lower levels of this reservoir and others in the West, have been reported during periods of persistent drought in the 1950s and 1960s. Tree-ring records from the Upper Colorado River basin indicate that droughts like those of the 1950s and 1960s are not uncommon in that area, and droughts more persistent and intense than those in the instrumental record (20th, 21st centuries) have occurred in the past 700 years.
The dry conditions also contributed to an active wildfire season in the western states. However, the number of acres burned in the United States through the end of November was 3.8 million acres, slightly less than the eight-year annual average and much less than the nearly 7 million acres burned in 2002, according to the National Interagency Fire Center.
At the end of November, 37 percent of the contiguous United States was in moderate-to-extreme drought in an area that stretched from Wisconsin to Texas and the Pacific coast states. The most extensive national drought coverage during the past 100 years (the period of instrumental record) occurred in July 1934, when 80 percent of the contiguous United States was in moderate-to-extreme drought.
The drought statistics are based on the Palmer Drought Index, a widely used measure of drought. The Palmer Drought Index uses numerical values derived from weather and climate data to classify moisture conditions throughout the contiguous United States and includes drought categories on a scale from mild to moderate, severe and extreme.
According to the NOAA National Hurricane Center, several factors contributed to the very active season including the absence of El Niño conditions in the Pacific and the persistence of conditions associated with the continuation of a multi-decadal period of enhanced activity that began in 1995. With the exception of 2002 and 1997, years that were both affected by El Niño, at least three major hurricanes have developed in every season since 1995. However, no significant long-term trend in hurricane strength or frequency has been observed in the Atlantic Basin.
During the past century, global surface temperatures have increased at a rate near 1.0 degree F/Century (0.6 degrees C/Century), but the trend has been three times larger since 1976, with some of the largest temperature increases occurring in the high latitudes. In 2003, warmer temperatures and shifts in atmospheric circulation patterns contributed to a second straight year of extremely low Arctic sea ice extent in September, according to the National Snow and Ice Data Center. However, Northern Hemisphere sea ice extent was more than that observed in September 2002.
Data collected by NOAA’s polar orbiting satellites and analyzed for NOAA by the University of Alabama in Huntsville and Remote Sensing Systems in Santa Rosa, Calif., also indicate that temperatures centered in the middle troposphere at altitudes from two to six miles are on pace to make 2003 the third-warmest year for the globe. The average lower troposphere temperature (surface to about five miles) for 2003 will also likely be the third warmest since the beginning of annual satellite measurements in 1979.
A record summer heat wave contributed to the large year-to-date anomalies in Europe. The all-time maximum temperature record in the United Kingdom was broken on Aug. 10, when the mercury reached 100.6 degrees F (38.1 degrees C) at Gravesend-Broadness (Kent). France had its warmest summer on record, which killed thousands.
Temperatures also soared across southern Asia in late May and June. During a 20-day heat wave, maximum temperatures reached as high as 113-122 degrees F (45-50 degrees C), and more than 1,500 deaths occurred in India, according to news reports.
Conversely, extremely cold winter temperatures occurred across Asia in January. Temperatures in northwestern Russia were as low as minus 50 degrees F (minus 45 degrees C), and thousands of deaths were attributed to extremely cold conditions in India and Bangladesh during the month, according to published reports. Moscow received snowfall in June for the first time since 1963. In the Peruvian highlands, temperatures dropped below minus 5 degrees F (minus 20 degrees C) during the Southern Hemisphere winter month of July, which led to the reported deaths of more than 200 people.
In Argentina, Santa Fe was reportedly hit by its worst flooding in centuries due to several days of heavy rainfall in April and May, which caused major rivers to overflow their banks. Heavy rains associated with Typhoon Maemi in September triggered landslides and flooding that were responsible for more than 130 deaths and the evacuation of more than 25,000 people from their homes in South Korea.
Normal-to-above-normal rainfall in the Sahel led to ideal growing conditions in much of this region of Africa. Rainfall in Zimbabwe and Mozambique brought some drought relief during the austral spring (September-November), but drought persisted in parts of those countries as well as South Africa and Botswana near years-end.
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