August 2011 Upper Air Report

Contents of this Section:

• Troposphere
• Stratosphere
• References

Note: Beginning in December 2010, all data are reported here with respect to the 1981–2010 base period. Prior to December 2010, radiosonde data were reported with respect to the 1961–1990 base period and satellite data were reported with respect to the 1979–1998 base period. Remote Sensing Systems continues to provide data to NCDC with respect to the 1979–1998 base period; however, NCDC readjusts the data to the 1981–2010 base period so that the satellite measurements are comparable. This change provides a more consistent comparison between the various datasets.

Note: Effective with the January 2011 report, Remote Sensing Systems (RSS) transitioned to a new version (3.3) of the RSS MSU/AMSU atmospheric temperature datasets. Information about the differences between version 3.2 and 3.3 is available.

Upper Air Highlights

• University of Alabama Huntsville satellite analyses report that the lower troposphere August 2011 temperature was 0.33°C (0.59°F) above the 1981–2010 average, the third warmest August since satellite records began in 1979.
• Remote Sensing Systems satellite analyses report a lower troposphere August temperature anomaly of 0.16°C (0.34°F) above the 1981–2010 average, the sixth warmest August on record.
• University of Alabama Huntsville satellite analyses report an August 2011 mid troposphere temperature anomaly of 0.18°C (0.32°F) above average, the sixth warmest such period on record. When these analyses are adjusted to remove stratospheric influence, the anomaly increases to 0.28°C (0.50°F) above average, the fourth warmest on record.
• Remote Sensing Systems satellite analyses report an August 2011 mid troposphere temperature anomaly of 0.17°C (0.31°F) above average, the seventh warmest such period on record. When these analyses are adjusted to remove stratospheric influence, the anomaly increases to 0.25°C (0.45°F) above average, the fourth warmest on record.
• RATPAC radiosonde analysis indicates that during the first eight months of 2011 (January–August) the average mid troposphere temperature was the ninth warmest year-to-date in the 54-year period of record, while satellite analyses report that the temperature ranked 10^th warmest to 16^th warmest in the 33-year period of record, depending on the source.
• For the lower stratosphere, the Remote Sensing Systems and University of Alabama Huntsville satellite analyses both indicate that August 2011 was the sixth coolest August, the second coolest June–August, and the third coolest January–August in the 33-year period of record.

Troposphere

Temperatures above the Earth's surface are measured within the lower troposphere, middle troposphere, and stratosphere using in-situ balloon-borne instruments (radiosondes) and polar-orbiting satellites (NOAA's TIROS-N). The radiosonde and satellite records have been adjusted to remove time-dependent biases (artificialities caused by changes in radiosonde instruments and measurement practices as well as changes in satellite instruments and orbital features through time). Global averages from radiosonde data are available from 1958 to present, while satellite measurements date back to 1979.

Lower Troposphere

Current Month | Seasonal | Year-to-date

These temperatures are for the lowest eight kilometers (five miles) of the atmosphere. Information on the University of Alabama in Huntsville (UAH) and Remote Sensing Systems (RSS) sources of troposphere data is available.

Mid-troposphere

Current Month | Seasonal | Year-to-date

These temperatures are for the atmospheric layer centered in the mid-troposphere (approximately 3–10 km [2–6 miles] above the Earth's surface), which also includes a portion of the lower stratosphere. (The Microwave Sounding Unit [MSU] channel used to measure mid-tropospheric temperatures receives about 25 percent of its signal above 10 km [6 miles].) Because the stratosphere has cooled due to increasing greenhouse gases in the troposphere and losses of ozone in the stratosphere, the stratospheric contribution to the tropospheric average, as measured from satellites, August create an artificial component of cooling to the mid-troposphere temperatures. The University of Washington (UW) versions of the UAH and RSS analyses attempt to remove the stratospheric influence from the mid-troposphere measurements, and as a result the UW versions tend to have a larger warming trend than either the UAH or RSS versions. For additional information, please see NCDC's Microwave Sounding Unit page.

The radiosonde data used in this global analysis were developed using the Lanzante, Klein, Seidel (2003) ("LKS") bias-adjusted dataset and the First Difference Method (Free et al. 2004) (RATPAC). Additional details are available. Satellite data have been adjusted 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 a third analysis has been performed by Dr. Qiang Fu of the University of Washington (UW) (Fu et al. 2004)** to remove the influence of the stratosphere on the mid-troposphere value. Global averages from radiosonde data are available from 1958 to present, while satellite measurements began in 1979.

RATPAC January–August plot

RATPAC June–August plot

The global mid-troposphere temperatures were well above average during August 2011. As shown in the table below, satellite measurements for August 2011 ranked fourth to seventh warmest on record, depending on the data source.

Radiosonde measurements indicate that mid-tropospheric temperatures were 0.33°C (0.59°F) above average during the Northern Hemisphere summer (Southern Hemisphere winter) season, giving June–August a rank of fifth warmest on record. The table below shows that satellite measurements for the season were third to fifth warmest, depending on the data source.

Radiosonde measurements indicate that, for the January–August year-to-date period, temperatures in the mid-troposphere were 0.16°C (0.29°F) above average, resulting in the ninth warmest January–August period (out of 54 years). Satellite analyses of the January–August year-to-date period for the middle troposphere was the 10^th to 16^th warmest in the 33-year satellite record, depending on the data source.

*RATPAC rank is based on 54 years of data

*RATPAC rank is based on 54 years of data

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Stratosphere

Current Month | Seasonal

The table below summarizes stratospheric conditions for September 2011. On average, the stratosphere is located approximately 16–23 kilometers (10–14 miles) above the Earth's surface. Over the last decade, stratospheric temperatures have been below average in part due to the depletion of ozone. The large positive anomaly in 1982 was caused by the volcanic eruption of El Chichon in Mexico, and the sharp jump in temperature in 1991 was a result of the eruption of Mt. Pinatubo in the Philippines. In both cases the temperatures returned to pre-eruption levels within two years.

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References

Christy, John R., R.W. Spencer, and W.D. Braswell, 2000: MSU tropospheric Temperatures: Dataset Construction and Radiosonde Comparisons. J. of Atmos. and Oceanic Technology, 17, 1153-1170.

Free, M., D.J. Seidel, J.K. Angell, J. Lanzante, I. Durre and T.C. Peterson (2005) Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC): A new dataset of large-area anomaly time series, J. Geophys. Res., 10.1029/2005JD006169.

Free, M., J.K. Angell, I. Durre, J. Lanzante, T.C. Peterson and D.J. Seidel(2004), Using first differences to reduce inhomogeneity in radiosonde temperature datasets, J. Climate, 21, 4171-4179.

Fu, Q., C.M. Johanson, S.G. Warren, and D.J. Seidel, 2004: Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends. Nature, 429, 55-58.

Lanzante, J.R., S.A. Klein, and D.J. Seidel (2003a), Temporal homogenization of monthly radiosonde temperature data. Part I: Methodology, J. Climate, 16, 224-240.

Lanzante, J.R., S.A. Klein, and D.J. Seidel (2003b), Temporal homogenization of monthly radiosonde temperature data. Part II: trends, sensitivities, and MSU comparison, J. Climate, 16, 241 262.

Mears, Carl A., M.C. Schabel, F.J. Wentz, 2003: A Reanalysis of the MSU Channel 2 tropospheric Temperature Record. J. Clim, 16, 3650-3664.

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