Climate of 2001
December in Historical Perspective

National Climatic Data Center, 15 January 2002

Global Highlights:

• *Global average land and ocean temperature was tenth warmest for December
• Lower tropospheric temperatures were above average during December
• Temperatures in the lower stratosphere were cooler than average
• During December, above average precipitation was most notable across the eastern Mediterranean region and parts of Brazil with below average precipitation across the eastern U.S and most of western and southern Europe

Contents of this Section:

• Introduction
• Global Temperatures
• Global Precipitation
• Microwave Sounding Unit Data

Introduction

Using a 1992-2001 base period as shown in the adjacent blended temperature product of satellite and in-situ data, anomalously cold temperatures during December in the Northern Hemisphere were closely correlated to the location of upper level troughs of low pressure. Dominant troughs of low pressure (depicted by negative 500 millibar height anomalies) were centered across eastern Europe and southern Alaska. Temperature anomalies calculated from in-situ station data using a 1961-1990 base period also show the cooler than average temperatures in these regions with warmer than average temperatures observed over most of North America, the Middle East and the African Sahel region.

larger image

Temperature

A slow evolution toward El Niño conditions continued during December, as the global land and ocean temperature was the tenth warmest in the 1880-2000 record and was 0.36°C (0.65°F) above the long-term average (0.22°C / 0.40°F above the 1961-1990 mean) Temperatures averaged across ocean areas were third warmest on record, or 0.48°C (0.86°F) above the long-term December mean

larger image

larger image

Based on data available at the time of this report, land temperatures in the tropical regions (20°N-20°S) were warmest on record for December, or 0.99°C (1.78°F) above the 1880-2000 mean

• Much of Europe was relatively dry, with only southeastern Europe and the eastern Mediterranean region experiencing wetter than average weather
• Dry conditions persisted in the eastern U.S., southeast Canada and northern Argentina
• Above average precipitation fell in parts of Brazil and southeast China

• December temperatures in the lowest 8km (5 miles) of the troposphere were 0.14°C (0.25°F) above average, with similar temperature anomalies across the Northern and Southern Hemisphere

• December temperatures were below average in the lower stratosphere, with a departure of -0.30°C (-0.54°F)
• This was the 9th consecutive December with below average stratospheric temperatures