March 2002 National Climate Report

National Temperatures

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The graph to the left shows monthly mean temperature averaged across the contiguous United States based on long-term data from the U.S. Historical Climatology Network (USHCN). The value for 2002 is estimated from preliminary Climate Division data using the first difference approach. March 2002 ranked as the 33rd coldest March in the 1895 to present record. The preliminary nationally averaged temperature was 40.5° F (4.7° C) which was 1.8° F (1.0° C) below the long-term mean. The March temperature values from 1895 through 2002 are available.

March 2002 marks the first time since March 2001 that temperatures in the contigous US averaged below normal, though March is characterized as displaying large interannual variability throughout the 108-year record. The Mean 500mb Height and Anomalies chart shows substantial negative height anomalies across the north central plains, corresponding to below average temperatures. Positive height anomalies existed along the east coast and over Alaska. These were associated with warmer than average temperatures in western Alaska and slightly above average temperatures in several eastern states. A more detailed analysis including how statewide and regionwide temperatures compare to other years is available.

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Temperature Departures

The map to the right, based on over 500 airport stations, shows departures from the 1971-2000 normal temperatures for March 2002. Warmer than average temperatures are limited to the Atlantic coast with the largest positive departures in the contiguous U.S. (greater than 1.8° F [1° C]) occurring in the New York City region, eastern North Carolina and Florida. Negative temperature anomalies were evident across the remainder of the contiguous U.S, as well as Hawaii and eastern Alaska. The most significant negative departures occurred in the Northern Plains where temperatures were colder than average by more than 7.2°F (5.0°C).

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The day-to-day variability of daily mean temperature was up to 150% of normal over most of the contiguous U.S. in March. This is associated with a series of cold outbreaks moving south and east across the central plains during the month, as can be seen in an animated map of daily temperature anomalies.

National Precipitation

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The graph to the left is a time series depicting precipitation averaged across the contiguous U.S. Based upon preliminary precipitation data, March 2002 was slightly above average, ranking 35th wettest. However, there was considerable regional variability in precipitation across the country. States in the West and Southwest regions continued to receive less rainfall than average this month, while states from Texas to New Hampshire were wetter or much wetter than average.

Tennessee, Kentucky and Arkansas received much above average precipitation for March, with much of the rain coming from a storm on the 16th-18th which led to severe flooding in parts of Kentucky. A more detailed analysis including how statewide and regionwide precipitation compares to other years is available.

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Precipitation Anomalies

The map to the right, based on more than 500 airport stations, shows March 2002 total precipitation as a percent of the 1971-2000 station normals. Above normal precipitation generally occurred from Texas to New Hampshire, with more than 180% of normal precipitation falling in some locations. The rest of the country was mostly dry, including, most notably, southern Californa and the Southwest, Florida, southern Texas, and the Central Plains. Alaska was also mostly dry and Hawaii and Puerto Rico received slightly below normal precipitation for the month.

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National Snow Cover

Snow cover across the country generally decreased throughout the month however, there were some significant snow storms in parts of the country, including Minnesota and Michigan (see image below).

The map to the right shows snow cover in the East North Central region of the US on March 15th after a storm left portions of Minnesota, Wisconsin and Michigan's Upper Peninsula blanketed in snow. Areas of Minnesota received up to 18 inches (45 cm) of snow. Anchorage, Alaska also received record snowfall in March. Over 28 inches (71 cm) of snow fell in Anchorage in a 24-hour period between March 16th and 17th.

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Citing This Report

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