Introduction

The April 2003 mean temperature was above the 1988-2002 average across Alaska, South Africa and Europe as shown in the adjacent map of blended satellite and in situ data. Cooler than average temperatures occurred over the northeastern U.S., western Asia, the Mediterranean region and the west coast of the U.S. The mean position of upper level ridges and troughs of low pressure (depicted by positive and negative 500 millibar height anomalies) are generally reflected by areas of positive and negative temperature anomalies at the surface, respectively.

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April temperature anomalies calculated from the Global Historical Climatology Network data set of land surface stations (using a 1961-1990 base period) also show above average temperatures throughout much of northwestern Canada and Alaska, much of western Europe, Southeast Asia and the southwestern coast of Australia. Monthly temperatures were 3-5°C (5.4-9.0°F) above the mean. Cooler than average temperatures were present throughout the Mediterranean region into western Asia, parts of the western United States and the eastern coast of Argentina where monthly temperatures were as much as 2-5°C (3.6-9.0°F) below average.

Temperature

April For April 2003, the global average land and ocean surface temperature was 0.51°C (0.92°F) above the 1880-2002 average, ranking as the fourth warmest April in the period of record The warmest April occurred in 1998, when the global anomaly was +0.74°C (+1.33°F) Globally averaged land temperatures were seventh warmest on record, 0.77°C (1.39°F) above the long-term mean

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April 2003 temperatures averaged across the Northern Hemisphere were seventh warmest on record, 0.53°C (0.95°F) above the long term mean Temperatures averaged throughout the Southern Hemisphere were third warmest, 0.46°C (0.83°F) above average

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For January-April 2003, the global average land and ocean surface temperature was 0.55°C (0.99°F) above the 1880-2002 average, ranking as the third warmest January-April in the period of record (see top graph at left)

Serial monthly global surface temperature departures with respect to a 1971-2000 mean are shown in the figure to the right Globally averaged surface temperatures (land and ocean) have been warmer than the 1971-2000 average for the last 84 consecutive months

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Precipitation

During April 2003, much above average precipitation fell across the southeastern U.S., Argentina, the Korean peninsula and the U.S.Pacific Northwest. Below average precipitation was observed in Brazil, northwestern Australia, southern Africa and Madagascar. Also, much of Canada was dryer than average in some of the same regions that have been experiencing drought Additional regional analysis can be found on the Global Hazards page

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ENSO SST Analysis

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El Nino conditions continued to rapidly dissipate in April as sea surface temperatures continued to cool in the central and equatorial Pacific, as shown in the adjacent animation of weekly sea surface temperature anomalies. This trend as well as others, such as a steady decrease in the central and eastern equatorial Pacific oceanic thermocline are indicators of a transition to La Nina conditions. The most up-to-date information on ENSO (El Nino/Southern Oscillation) conditions can be found at NOAA's Climate Prediction Center (CPC) and the CPC ENSO Diagnostic Discussion . Images of sea surface temperature conditions are available for all months to date during 2003 at 2003 weekly sst

Microwave Sounding Unit Data

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Temperatures in the lowest 8km (5 miles) of the troposphere were 0.14°C (0.25°F) above the 1979-1998 average during April 2003, the eighth warmest April in the satellite period of record (1979 to present) Temperatures in the Northern Hemisphere were fourth warmest on record for April, 0.25°C (0.45°F) above the mean Temperatures in the Southern Hemisphere were twelfth warmest on record for April, 0.02°C (0.04°F) above the mean

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April 2003 temperatures were below the 1984-1990 average in the lower stratosphere, 0.27°C (0.49°F) cooler than the mean This was the tenth consecutive April with below average temperatures in the lower stratosphere

  For additional details on precipitation and temperatures in April, see the Global Hazards page .

References:

Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global Historical Climatology Network Database. Bull. Amer. Meteorol. Soc., 78, 2837-2849.

For all climate questions other than questions concerning this report, please contact the National Climatic Data Center's Climate Services Division:

Climate Services Division
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fax: 828-271-4876
phone: 828-271-4800
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For questions about this report, please contact:

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

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

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