National Oceanic and Atmospheric Administration

National Climatic Data Center, April 14, 1999

This section of the March report presents numerous regions throughout the world where significant climatic anomalies are highlighted and described.

Africa Temperature

The warm/cool anomaly structure on the map is related to a synoptic pattern with a northern hemispheric trough in the east and a ridge across the central portions of North Africa. This pattern was even stronger in February. It retained much of its structure, but was weaker, during March. Warm (positive) anomalies were limited to north central Africa and across portions of southern Africa. Cooler anomalies were prevalent across northwestern Africa and along the Great Rift Valley region on the east side of the continent.

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Wetness Anomalies in Africa

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Surface wetness was above average in portions of Morocco and northern Algeria. There were also several anomalously wet areas including portions of northern Tanzania, eastern Zambia, and southern Mozambique. Additional isolated positive anomalies were located over the Ivory Coast, Namibia, and Botswana. Dry areas included portions of northern Ethiopia and South Africa; both these areas have been drier than average for the last few months. The warm dry conditions over southern Africa have caused a significant drought during their normal rainy season. There are also dry areas along portions of the Great Rift Valley in eastern Africa.

Europe / Asia Temperature

Warm anomalies extended from interior Europe southeastward into western Asia, in sharp contrast to the cold anomalies across most of this region last month. (see Climate of February 1999) These warm anomalies in March led to rapid melting of the snow pack, which caused flooding across portions of southeastern Europe.

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Warm anomalies also persisted from last month across portions of southeast Asia. Especially noteworthy are Thailand and Vietnam, which have been experiencing extended drought conditions. Warm conditions also persisted over portions of southern China but the anomalies were not quite as extreme or widespread as previous months. A deep trough over portions of Siberia and Mongola kept those regions colder than average.

Wetness Anomalies in Europe

Last month a large portion of Europe was blanketed by snow cover. This snow pack rapidly melted away during March, leaving those areas wetter than normal. This was particularly true near the Hungarian-Romanian border, where the rapid snow melt caused extensive flooding, as indicated by the large positive wetness anomalies on the map.

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Further to the east in Russia, the snow cover remained unmelted longer than usual during the month, which is indicated by the negative wetness anomalies. In the Ukraine and southern Russia, it was warmer and drier than usual. Northern Lebanon and northern Israel received some much needed rain, while to the east and south in Jordan and along the Iran-Iraq border it was much drier than normal with drought conditions.

Wetness Anomalies in Asia

Low precipitation and above average temperatures in March worsened a drought over eastern China, although the central coastal area did receive some much needed rain. The dryness extended into northern Vietnam, which has also been experiencing a severe drought, while the southern portion of the country was favorably wet. Bangladesh and the surrounding areas were also drier than average even for this their dry season. There were areas of dryness in central India, northern Pakistan, and eastern Afghanistan. The western portion of Afghanistan was wetter than average.

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Snow Cover in Europe

The most pronounced feature on this map is the area of negative snow cover anomalies over southern Russia and the Ukraine. This area experienced fewer than usual days with snow cover because of the unusually warm and dry conditions which have persisted for several months.

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Seasonal to slightly warmer than average temperatures in Europe, contrasted to the extremely cold anomalies of last month. These warmer conditions promoted the rapid melting of the snow pack leading to negative anomalies in much of eastern Europe. Further east in Russia the snow cover remained largely intact.

Australia Temperature

Positive temperature anomalies persisted from last month across portions of New Zealand and the surrounding south Pacific Ocean. This warm structure extended northwestward into southeastern Australia and the center of the continent, although these anomalies were not as extreme as in earlier months. Temperatures across portions of southwestern Australia were quite cool due to cloudiness and precipitation related to the active monsoon and tropical cyclone season. It was also cooler and wetter across portions of northeastern Australia.

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Wetness Anomalies in Australia

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A broad monsoonal trough and several tropical systems passed through western Australia. Positive wetness anomalies were also observed along the western slopes of the Great Dividing Range in eastern Australia. The north central portion of the continent was drier than usual but overall the continent experienced an increase in positive wetness anomalies in March. Due to the sandy soil in western Australia, the water percolates through the surface quickly which weakens the wetness signal observed by the satellite. Because of this, even though a large portion of western Australia received record rainfall, that is not apparent in this analysis. A detailed analysis for Australia can be found at Australian Bureau of Meteorology Precipitation Analyses - March 1999.

U.S. Temperature

Frequent storms on both the east and west coasts of the U.S. corresponded with below average temperatures. In contrast, a mean ridge was maintained across the northern plains where above average temperatures were observed. Mild temperatures occurred across the Big Bend area of Texas and portions of northern New England.

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Wetness Anomalies in the United States

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Storminess produced wetter than average conditions from northern Texas into southern Kansas for the second month in a row. The negative wetness values over the midwestern states are likely a consequence of below normal precipitation for the month. In addition, surface moisture in a completely frozen state will not be detected as surface wetness. High surface wetness values are notable in the Red River Valley region.

The southeast was drier than usual which is not accurately depicted in this image. The wetness index is not an accurate measure of surface wetness over areas where dense vegetation obscures the surface water from the satellite. The same situation is also true over the Pacific northwest areas along and west of the Cascade Mountains. The southwestern quarter of the country was drier than usual and has been since December.

Percent Snow Cover in North America

This map illustrates the percent of the month covered by snow. For example, most of Canada was covered by snow over 90 percent of the month. The western United States were covered for most of the month due to remaining winter precipitation as well as new snowfall. Percentages were also high across portions of the extreme northern plains eastward across the northern Great Lakes into northern New England.

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Snow Cover Anomalies in North America

Storms typical of a La Niña pattern continued to slam into the Pacific Northwest coast in March. The number of days with snow cover was well above average across much of western North America. In fact, a ski resort on Mt. Baker, Washington reported an unofficial snowfall for the season in excess of 90 feet.

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In contrast, an area from eastern Montana into western Minnesota experienced below average snow cover due to a milder southerly flow and premature melting. Whereas areas to the north, along the Canadian - U.S. border, show a positive anomaly since much of the precipitation fell as snow. There were also positive snow cover anomalies centered around the Great Lakes region where temperatures were near or below average.

South America Temperature

Temperatures were generally near average or slighly cooler across most of South America. The positive anomalies were limited to central sections of the continent. This cool/warm contrast (dipole pattern) across sections of South America complements the liquid water image, below, where the warm areas in March were also dry and the cool areas were wet.

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South America Wetness Anomalies

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Bolivia had a dipole structure of below average wetness in the east, and above average wetness in the far west. This above average anomaly extended westward into Peru. This dipole structure was also apparent across the northern half of Argentina. There were isolated dry areas in southern Brazil, and a pronounced area of above average wetness in northern Columbia. This wet/dry contrast across portions of South America complements the temperature anomaly image above.

Basist, A., N.C. Grody, T.C. Peterson and C.N. Williams, 1998: Using the Special Sensor Microwave/Imager to Monitor Land Surface Temperatures, Wetness, and Snow Cover. Journal of Applied Meteorology, 37, 888-911.

For more information, refer to ...
SSMI Derived Products
Global Historical Climatology Network (GHCN)
The Blended GHCN - SSM/I Product
The Global Temperature Anomalies

Tom Ross
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: tom.ross@noaa.gov

David Easterling
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: david.easterling@noaa.gov

Mike Changery
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: mchangry@ncdc.noaa.gov

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