An Update of Observed Stratospheric Temperature Trends
The following temperature data sets are available for stratospheric trend evaluations. Data are available on the ftp server at /sparc/ref_clim/randel/temp_trend/. Instructions to read the data are available in the readme.format file. More detailed descriptions of these data and further references are available in Randel et al. (2009).
Radiosonde-Based Data Sets
Several different data sets have been developed, based on historical radiosonde measurements, incorporating homogeneity adjustments to account for changes in instrumentation or observational practices that introduce spurious time series changes. The data sets have been developed by separate research groups using different techniques to identify and make adjustments in the original measurements.
RATPAC (bin, ascii): Annual and large-area mean mean temperature anomalies derived from a limited (85-station) network. Data are available at 13 pressure levels for 4 latitude bands (90 N-S, 30 N-S, 30-90 N and 30-90 S). Time series begin in 1958. Reference: Free et al. (2005).
RATPAC-lite (bin, ascii): Station-based radiosonde data set, derived from a 47-station subset of RATPAC, with stations chosen based on comparisons with MSU satellite measurements. Data are available as monthly anomalies on standard pressure levels, with time series beginning in 1979. Reference: Randel and Wu (2006).
HadAT2 (bin, ascii): Monthly global gridded data set, derived using nearby radiosonde data to identify and adjust artificial break points. Monthly zonally averaged data are available on 9 pressure levels, on a 5 degree latitude grid, beginning in 1958. Reference: Thorne et al. (2005).
IUK (Iterative Universal Kriging) (bin, ascii): A statistically-based technique, incorporating day minus night differences and accounting for seasonally dependent biases. No input from station metadata, forecast models or satellite information is used. Data are originally available for individual stations, but are provided here as a globally gridded data set, using averages of available data within 10 degree latitude by 10 degree longitude bins. Monthly time series begin in 1958. Reference: Sherwood et al. (2008).
RAOBCORE1.4 (bin, ascii): These data are derived using differences between radiosonde data and background forecasts of an atmospheric climate data assimilation (reanalysis) system to identify artificial break points in the radiosonde data. These are then adjusted using using the reanalysis data. Monthly time series are available beginning in 1958, on a regular 10 degree latitude by 10 degree longitude grid. Reference: Haimberger (2007).
RICH (bin, ascii): These data are similar to RAOBCORE1.4, using reanalysis data to identify artificial break points, but use nearby radiosonde data to make adjustments. Data details are the same as for RAOBCORE1.4. Reference: Haimberger et al. (2008).
Satellite Data Sets
Stratospheric temperature measurements from operational NOAA satellites are available beginning in 1979. Continuous time series are derived from combining measurements from many individual satellite instruments, taking account of satellite orbit drift and decay, calibration and other factors (using temporal overlap between individual instruments).
Microwave Sounding Unit (MSU): MSU Channel 4 data represent a weighted layer average over ~13-22 km. Time series of MSU temperatures are obtained from two separate research groups, Remote Sensing Systems (RSS) (bin, ascii) and the University of Alabama at Huntsville (UAH) (bin, ascii), and results are slightly different between these analyses. Monthly data are available as globally gridded fields (5 degree latitude by 10 degree longitude), with time series beginning in 1979.
Stratospheric Sounding Unit (SSU) (only available in ascii): SSU measurements include data for a number of separate channels, covering altitudes from the middle to upper stratosphere. Data are included for a number of nadir channels (25, 26, and 27), together with several synthetic channels derived using combinations and differences of nadir and off-nadir scans (so-called x-channels, 15x, 26x, 36x and 47x). Data from each of these channels corresponds to averages over 10-15 km thick layers, and weighting functions for each of the channels are included on a pressure (altitude) scale, with 33 vertical levels. Note that these weighting functions are from an updated analysis (calculations described in Shine et al, (2008), and the x-channel results are slightly different from previous calculations. Time series of SSU data are available as monthly zonal mean temperature anomalies for each channel on a 10 degree latitude grid covering 70 N to 70 S. The anomaly time series have been adjusted to take account of the effects of increasing atmospheric CO2 on the SSU weighting functions (Shine et al, 2008). Anomalies have been calculated compared to a seasonal climatology calculated for 1980-1994, and these background data are also available here for the nadir channels (25, 26, and 27) and the x-channels (15x, 26x, 36x and 47x).
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 data set of large-area anomaly time series, J. Geophys. Res., 110, D22101, doi:10.1029/2005JD006169.
Haimberger L. (2007), Homogenization of radiosonde temperature time series using innovation statistics. J. Climate, 20, 1377–1403, doi:10.1175/JCLI4050.1.
Haimberger, L., C. Tavolato and S. Sperka (2008), Toward elimination of the warm bias in historic radiosonde temperature records — some new results from a comprehensive intercomparison of upper air data. J. Climate, 21, 4587-4606, doi:10.1175/2008JCLI1929.1.
Randel, W.J., and F. Wu (2006), Biases in stratospheric and tropospheric temperature trends derived from historical radiosonde data. J. Climate, 19, 2094-2104, doi:10.1175/JCLI3717.1.
Randel, W.J., et al., (2009), An update of observed stratospheric temperature trends. J. Geophys. Res., 114, D02107, doi:10.1029/2008JD010421.
Sherwood, S. C., C. L. Meyer, R. J. Allen and H. A. Titchner (2008), Robust tropospheric warming revealed by iteratively homogenized radiosonde data. J. Climate, 21, 5336-5352, doi:10.1175/2008JCLI2320.1.
Shine, K.P., J. J. Barnett and W.J. Randel (2008), Temperature trends derived from Stratospheric Sounding Unit radiances: the effect of increasing CO2 on the weighting function. Geophys. Res., Lett., 35, L02710, doi:10.1029/2007GL032218.
Thorne, P. W., D. E. Parker, S. F. B. Tett, P. D. Jones, M. McCarthy, H. Coleman and P. Brohan (2005), Revisiting radiosonde upper-air temperatures from 1958 to 2002, J. Geophys. Res., 110, D18105, doi:10.1029/2004JD005753.