NCDC / Climate Monitoring / Climate of 2005 / April / Global / Help

Climate of 2005 - April in Historical Perspective

National Climatic Data Center
16 May 2005

Global Analysis / Global Hazards / United States / U.S. Drought / Extremes
Use these links to access detailed analyses of Global and U.S. data.

Global Highlights:

Based on preliminary data, global averaged combined land and sea surface temperature for April 2005 was 2nd warmest on record.
April temperatures were above average over the northern Great Plains of the U.S., Canada, the majority of Australia and eastern Asia. Colder-than-average conditions occurred primarily in far western Alaska, the southern U.S., and India.
Precipitation during April was above average over the eastern U.S., the Caribbean and western Europe, with drier than average conditions over much of Asia, the majority of Australia and Alaska.
Sea Surface Temperatures (SSTs) were slightly above normal across the central and eastern equatorial Pacific during April

The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. The most current data may be accessed via the Global Surface Temperature Anomalies page.

Introduction

Temperature anomalies for April 2005 are shown on the two maps below. The dot map on the left uses anomalies that were calculated from the Global Historical Climatology Network (GHCN) data set of land surface stations using a 1961-1990 base period. The map on the right is a weekly product based on data from the Comprehensive Ocean-Atmosphere Data Set (COADS) of SST data. During April, there were above average temperatures over much of Alaska, Canada, Mexico, Algeria, the majority of Europe, the Middle East, eastern China, Australia, as well as from the northern Great Plains to the northeastern U.S. Cooler than average temperatures were observed over the southern U.S., coastal Argentina, far western Alaska, India and parts of western Australia.

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Above average SSTs are also evident in the product above. Slightly warmer than average conditions occurred over large parts of the eastern and central Pacific, reflecting transitioning conditions from an El Niño warm phase to a neutral phase. SSTs were also warmer than average in much of the northern Pacific and northern Atlantic. Cooler than average SSTs were observed over areas northwest of the Hawaiian Islands, off the eastern seaboard of the U.S., and off the east coast of Japan.

The mean position of upper level ridges of high pressure and troughs of low pressure (depicted by positive and negative 500 millibar height anomalies on the April 2005 map) are generally reflected by areas of positive and negative temperature anomalies at the surface, respectively. For other Global products see the Climate Monitoring Global Products page.

Images of sea surface temperature conditions are available for all months during 2005 at the weekly SST page

Temperature Rankings and Graphics

Current Month / Year-to-date

April	Anomaly	Rank	Warmest Year on Record
Global Land Ocean Land and Ocean	+1.27°C (+2.29°F) +0.41°C (+0.74°F) +0.67°C (+1.21°F)	1st warmest 3rd warmest 2nd warmest	2nd - 1998 (+1.23°C/2.21°F) 1998 (+0.51°C/0.92°F) 1998 (+0.72°C/1.30°F)
Northern Hemisphere Land Ocean Land and Ocean	+1.26°C (+2.27°F) +0.47°C (+0.85°F) +0.79°C (+1.42°F)	1st warmest 1st warmest 1st warmest	2nd - 1998 (+1.25°C/2.25°F) 2nd - 2004 (+0.46°C/0.83°F) 2nd - 1998 (+0.77°C/1.39°F)
Southern Hemisphere Land Ocean Land and Ocean	+1.06°C (+1.91°F) +0.38°C (+0.68°F) +0.51°C (+0.92°F)	2nd warmest 7th warmest 3rd warmest	1998 (+1.07°C/1.93°F) 1998 (+0.56°C/1.01°F) 1998 (+0.66°C/1.19°F)

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January-April	Anomaly	Rank	Warmest Year on Record
Global Land Ocean Land and Ocean	+0.97°C (+1.75°F) +0.43°C (+0.77°F) +0.59°C (+1.06°F)	4th warmest 2nd warmest 4th warmest	2002 (+1.37°C/2.47°F) 1998 (+0.51°C/0.92°F) 1998 (+0.72°C/1.30°F)
Northern Hemisphere Land Ocean Land and Ocean	+0.93°C (+1.67°F) +0.46°C (+0.83°F) +0.65°C (+1.17°F)	10th warmest 2nd warmest 4th warmest	2002 (+1.60°C/2.90°F) 1998 (+0.51°C/0.92°F) 2002 (+0.86°C/1.55°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.90°C (+1.62°F) +0.43°C (+0.77°F) +0.52°C (+0.94°F)	warmest 5th warmest 2nd warmest	2nd - 1998 (+0.87°C/1.57°F) 1998 (+0.54°C/0.97°F) 1998 (+0.60°C/1.10°F)

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The most current data may be accessed via the Global Surface Temperature Anomalies page.

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Precipitation

The maps below represent anomaly values based on the GHCN data set of land surface stations using a base period of 1961-1990. During April 2005, above average precipitation fell over the northeastern U.S., the lower Mississippi Valley of the U.S., north-central South America, Puerto Rico, western Europe, southern India and parts of western Australia. Below average precipitation was observed over the southern Great Plains of the U.S., Alaska, the majority of eastern and southeastern Asia, much of Australia, Madagascar and the Iberian Peninsula.

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ENSO SST Analysis

Last week of the month's ENSO condtions Map

Click here for animated loop

SSTs decreased in the eastern equatorial Pacific during April, indicating that ENSO is transitioning from a weak warm phase (El Niño) to neutral conditions (shown in the adjacent animation of weekly sea surface temperature anomalies). A comprehensive summary of April 2005 ENSO conditions can be found on the ENSO monitoring page. For the latest advisory on ENSO conditions go to NOAA's Climate Prediction Center (CPC) and the CPC ENSO Diagnostic Discussion
Images of sea surface temperature conditions are available for all months during 2005 at the weekly SST page

Troposphere

Current Month
The table below summarizes mid-tropospheric conditions for April 2005. These temperatures are for the atmospheric layer centered in the mid-troposphere (approximately 2-6 miles above the Earth's surface) which also includes a portion of the lower stratosphere. (The MSU channel used to measure mid-tropospheric temperatures receives about 25 percent of its signal above 6 miles).

Analysis of the satellite record that began in 1979 indicates that global temperatures are increasing in the mid-troposphere, but the magnitude of the trend differs based on the analysis methods used in adjusting for factors such as orbital decay and inter-satellite differences.

Scientists at the University of Washington {UW}, developed a method for quantifying the stratospheric contribution to the satellite record of tropospheric temperatures and applied an adjustment to the UAH and RSS temperature record that attempts to remove the satellite contribution (cooling influence) from the middle troposphere record. This method results in trends that are larger than the those from the respective source.

The UAH and the UW-UAH adjusted data indicate that April 2005 was the 3rd and 2nd warmest April, respectively. The RSS data and the UW-RSS adjusted data both indicate that April 2005 was 2nd, since records began in 1979.

April	Anomaly	Rank	Warmest Year on Record	Trend
UAH mid-trop	+0.27°C/0.49°F	3rd warmest	1998 (+0.71°C/1.28°F)	+0.06°C/decade
*RSS mid-trop	+0.36°C/0.65°F	2nd warmest	1998 (+0.78°C/1.40°F)	+0.13°C/decade
**UW-UAH mid-trop	+0.39°C/0.70°F	2nd warmest	1998 (+0.86°C/1.55°F)	+0.12°C/decade
*UW-RSS mid-trop	+0.47°C/0.85°F	2nd warmest	1998 (+0.92°C/1.66°F)	+0.19°C/decade

*Version 02_1

Mid-tropospheric and lower stratospheric temperature data are collected by NOAA's TIROS-N polar-orbiting satellites and adjusted for time-dependent biases by the Global Hydrology and Climate Center at the University of Alabama in Huntsville (UAH). An independent analysis is also performed by Remote Sensing Systems(RSS) and the University of Washington.

**An adjustment on both the RSS and UAH datasets provided by Fu et al. (2004) (University of Washington) is accomplished by deriving separate weighting coefficients for the MSU T2 and T4 over the tropics (30N to 30S), northern and southern hemispheres, and for the global mean by fitting radiosonde troposphere anomalies to radiosonde-simulated T2 and T4 anomalies over the period from 1958-2004 as

T850-300 = a0 + a2*T2 + a4*T4

where T850-300 is the radiosonde 850-300 hPa layer; T2 and T4 are the radiosonde simulated MSU brightness temperature anomalies; and a0, a2, and a4 are the coefficients derived from this linear regression.

Stratosphere

Current Month
The table below summarizes stratospheric conditions for April 2005. The stratosphere is located between 10-14 miles above the Earth's surface. Over the last decade, stratospheric temperatures have been below average in large part due to the depletion of ozone. The large increase in temperature in 1982 was caused by the volcanic eruption of El Chichon in Mexico, and the increase in 1991 was a result of the eruption of Mt. Pinatubo in the Philippines. Therefore the base period used is 1984-1990 which was chosen to avoid contamination by these eruptions.

April	Anomaly	Rank	Warmest Year on Record
UAH stratosphere	-0.49°C (-0.88°F)	4th coolest	1983 (+0.91°C/1.64°F)
*RSS stratosphere	-0.45°C (-0.81°F)	3rd coolest	1992 (+0.86°C/1.55°F)

*Version 02_1

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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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For questions about this report, please contact:

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fax: 828-271-4328
email: Jay.Lawrimore@noaa.gov

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email: David.Easterling@noaa.gov

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