 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)
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- 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
Click
here for animated loop
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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
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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
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Lower tropospheric and lower stratospheric temperature data are
collected by NOAA's TIROS-N polar-orbiting satellites and adjusted
for time-dependent biases by NASA and the Global
Hydrology and Climate Center at the University of Alabama in
Huntsville.
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.
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