Global Analysis - July 2001

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Note: GHCN-M Data Notice

An omission in processing a correction algorithm led to some small errors on the Global Historical Climatology Network-Monthly dataset (GHCN-M v3.2.0). This led to small errors in the reported land surface temperatures in the October, November, December and Annual U.S. and global climate reports. On February 14, 2013, NCDC fixed this error in its software, included an additional improvement (described below), and implemented both changes as GHCN-M version 3.2.1. With this update to GHCN-M, the Merged Land and Ocean Surface Temperature dataset also is subsequently revised as MLOST version 3.5.3.

The net result of this new version of GHCN-M reveals very small changes in temperature and ranks. The 2012 U.S. temperature is 0.01°F higher than reported in early January, but still remains approximately 1.0°F warmer than the next warmest year, and approximately 3.25°F warmer than the 20th century average. The U.S. annual time series from version 3.2.1 is almost identical to the series from version 3.2.0 and that the 1895-2012 annual temperature trend remains 0.13°F/decade. The trend for certain calendar months changed more than others (discussed below). For the globe, ranks of individual years changed in some instances by a few positions, but global land temperature trends changed no more than 0.01°C/century for any month since 1880.

NCDC uses two correction processes to remove inhomogeneities associated with factors unrelated to climate such as changes in observer practices, instrumentation, and changes in station location and environment that have occurred through time. The first correction for time of observation changes in the United States was inadvertently disabled during late 2012. That algorithm provides for a physically based correction for observing time changes based on station history information. NCDC also routinely runs a .pairwise correction. algorithm that addresses such issues, but in an indirect manner. It successfully corrected for many of the time of observation issues, which minimized the effect of this processing omission.

The version 3.2.1 release also includes the use of updated data to improve quality control and correction processes of other U.S. stations and neighboring stations in Canada and Mexico.

Compared to analyses released in January 2013, the trend for certain calendar months has changed more than others. This effect is related to the seasonal nature of the reintroduced time-of-observation correction. Trends in U.S. winter temperature are higher while trends in summer temperatures are lower. For the globe, ranks of individual years changed in some instances by a few positions, but global temperature trends changed no more than 0.01°C/century for any month since 1880.

More complete information about this issue is available at this supplemental page.

NCDC will not update the static reports from October through December 2012 and the 2012 U.S and Global annual reports, but will use the current dataset (GHCN-M v. 3.2.1 and MLOST v. 3.5.3) for the January 2013 report and other comparisons to previous months and years.

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Global Highlights:

  • Global average land and sea surface temperature was the second warmest on record for July
  • Lower tropospheric temperatures were slightly warmer than average during the month
  • Temperatures in the lower stratosphere were cooler than average
  • Above average precipitation was most notable across southeast China, with below average precipitation across Japan, the US Southern Plains and Venezuela
  

Contents of this Section:
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Top of Page Introduction

Anomalous warmth (using a 1992-2001 base period as shown in the adjacent blended product of satellite and in-situ data) was dominant across eastern and western Asia as well as the central parts of the United States and Canada in July. Strong upper level ridges of high pressure (depicted by positive 500 millibar height anomalies) were situated across much of Canada, as well as western and eastern areas of the Former Soviet Union (FSU). Temperature anomalies calculated from in-situ station data using a 1961-1990 base period also show the warmer than average temperatures in these regions as well as cooler than average temperatures across much of the central FSU, the eastern seaboard of the US and southern Argentina. Click Here for the Global Blended Temperature in July 2001
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Top of Page Temperature

  • July 2001 global land and ocean temperature was second warmest in the 1880 to present record and was 0.50°C (0.90°F) above the long-term average (0.42°C / 0.76°F above the 1961-1990 mean)
  • Temperatures averaged across the Northern Hemisphere ranked second warmest, or 0.63°C (1.13°F) above the long-term July mean
 Click Here for the Global Temp Anomalies in June 2001
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Click Here for the July Northern Hemisphere Temperatures
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  • The warmest July on record was observed across the extratropical oceans of the Northern Hemisphere (90°N-20°N), as the average ocean temperature was 0.66°C (1.19°F) above average
  • Using a 1961-1990 base period, the ocean temperature in the Northern Hemisphere extratropics was 0.63°C (1.13°F) above the 30-year average
  • Across extratropical areas of the Northern Hemisphere, 2001 had the second warmest July in the 1880 to present record, falling just 0.02°C (0.04°F) below the record July temperature anomaly of 0.83°C (1.49°F) that occurred during the El Niño year of 1998
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Top of Page Precipitation

  • Several landfalling typhoons in the western Pacific brought unusually heavy rains to the southeast coast of China
  • Monthly precipitation departures of 100-200 mm (3.94-7.87 inches) were common across Japan, Venezuela and the central US
  • Monsoon rains were lighter than average across most of the northern half of India
 Click Here for the Global Precip Anomalies in July 2001 larger image

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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.

Citing This Report

NOAA National Climatic Data Center, State of the Climate: Global Analysis for July 2001, published online August 2001, retrieved on June 19, 2013 from http://www.ncdc.noaa.gov/sotc/global/2001/7.