An assessment of differences in lower stratospheric temperature records from (A)MSU, radiosondes, and GPS radio occultation

Abstract. Uncertainties for upper-air trend patterns are still substantial. Observations from the radio occultation (RO) technique offer new opportunities to assess the existing observational records there. Long-term time series are available from radiosondes and from the (Advanced) Microwave Sounding Unit (A)MSU. None of them were originally intended to deliver data for climate applications. Demanding intercalibration and homogenization procedures are required to account for changes in instrumentation and observation techniques. In this comparative study three (A)MSU anomaly time series and two homogenized radiosonde records are compared to RO data from the CHAMP, SAC-C, GRACE-A and F3C missions for September 2001 to December 2010. Differences of monthly anomalies are examined to assess the differences in the datasets due to structural uncertainties. The difference of anomalies of the (A)MSU datasets relative to RO shows a statistically significant trend within about (−0.2±0.1) K/10 yr (95% confidence interval) at all latitudes. This signals a systematic deviation of the two datasets over time. The radiosonde network has known deficiencies in its global coverage, with sparse representation of most of the southern hemisphere, the tropics and the oceans. In this study the error that results from sparse sampling is estimated and accounted for by subtracting it from radiosonde and RO datasets. Surprisingly the sampling error correction is also important in the Northern Hemisphere (NH), where the radiosonde network is dense over the continents but does not capture large atmospheric variations in NH winter. Considering the sampling error, the consistency of radiosonde and RO anomalies is improving substantially; the trend in the anomaly differences is generally very small. Regarding (A)MSU, its poor vertical resolution poses another problem by missing important features of the vertical atmospheric structure. This points to the advantage of homogeneously distributed measurements with high vertical resolution.

[1]  H. L. Miller,et al.  Climate Change 2007: The Physical Science Basis , 2007 .

[2]  John R. Christy,et al.  Analysis of the Merging Procedure for the MSU Daily Temperature Time Series , 1998 .

[3]  Lennart Bengtsson,et al.  GNSS Occultation Sounding for Climate Monitoring , 2001 .

[4]  Barbara Scherllin-Pirscher,et al.  Refractivity and temperature climate records from multiple radio occultation satellites consistent within 0.05 , 2011 .

[5]  John R. Christy,et al.  Uncertainty in Signals of Large-Scale Climate Variations in Radiosonde and Satellite Upper-Air Temperature Datasets , 2004 .

[6]  S. Hassol,et al.  Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences , 2006 .

[7]  John R. Christy,et al.  Tropospheric temperature change since 1979 from tropical radiosonde and satellite measurements , 2007 .

[8]  Ying-Hwa Kuo,et al.  Estimating the uncertainty of using GPS radio occultation data for climate monitoring: Intercomparison of CHAMP refractivity climate records from 2002 to 2006 from different data centers , 2009 .

[9]  F. Wentz,et al.  Construction of the RSS V3.2 Lower-Tropospheric Temperature Dataset from the MSU and AMSU Microwave Sounders , 2009 .

[10]  Martin Stendel,et al.  Validating the microwave sounding unit stratospheric record using GPS occultation , 2003 .

[11]  Ying-Hwa Kuo,et al.  Calibration of temperature in the lower stratosphere from microwave measurements using COSMIC radio occultation data: Preliminary results , 2009 .

[12]  Ying-Hwa Kuo,et al.  Empirical analysis and modeling of errors of atmospheric profiles from GPS radio occultation , 2011 .

[13]  Corinne Le Quéré,et al.  Climate Change 2013: The Physical Science Basis , 2013 .

[14]  Gottfried Kirchengast,et al.  Lower Stratospheric Temperatures from CHAMP RO Compared to MSU/AMSU Records: An Analysis of Error Sources , 2009 .

[15]  Leopold Haimberger,et al.  Toward Elimination of the Warm Bias in Historic Radiosonde Temperature Records—Some New Results from a Comprehensive Intercomparison of Upper-Air Data , 2008 .

[16]  Anthony J. Mannucci,et al.  CHAMP and SAC-C atmospheric occultation results and intercomparisons , 2004 .

[17]  J. Schofield,et al.  Observing Earth's atmosphere with radio occultation measurements using the Global Positioning System , 1997 .

[18]  Douglas Hunt,et al.  Comparing radiosonde and COSMIC atmospheric profile data to quantify differences among radiosonde types and the effects of imperfect collocation on comparison statistics , 2010 .

[19]  Ying-Hwa Kuo,et al.  Quantifying uncertainty in climatological fields from GPS radio occultation: an empirical-analytical error model , 2011 .

[20]  J. Wickert,et al.  GPS radio occultation with GRACE: Atmospheric profiling utilizing the zero difference technique , 2004, physics/0409032.

[21]  Jens Wickert,et al.  Assessing the climate monitoring utility of Radio Occultation data: from CHAMP to FORMOSAT-3/COSMIC. , 2009 .

[22]  Ying-Hwa Kuo,et al.  A comparison of lower stratosphere temperature from microwave measurements with CHAMP GPS RO data , 2007 .

[23]  John R. Christy,et al.  UNCERTAINTIES IN CLIMATE TRENDS Lessons from Upper-Air Temperature Records , 2005 .

[24]  C. Zou,et al.  Stability of the MSU-Derived Atmospheric Temperature Trend , 2010 .

[25]  Jens Wickert,et al.  Observing upper troposphere–lower stratosphere climate with radio occultation data from the CHAMP satellite , 2008 .

[26]  U. Foelsche,et al.  Atmospheric temperature change detection with GPS radio occultation 1995 to 2008 , 2009 .

[27]  T. Shepherd,et al.  How Will the Stratosphere Affect Climate Change? , 2007, Science.

[28]  Rolf König,et al.  Atmosphere sounding by GPS radio occultation: First results from CHAMP , 2001 .

[29]  Gottfried Kirchengast,et al.  A multi-year comparison of lower stratospheric temperatures from CHAMP radio occultation data with MSU/AMSU records , 2007 .

[30]  Gottfried Kirchengast,et al.  Local time influence in single‐satellite radio occultation climatologies from Sun‐synchronous and non‐Sun‐synchronous satellites , 2007 .

[31]  J. Dykema,et al.  Climate Benchmarking Using GNSS Occultation , 2006 .

[32]  Leopold Haimberger,et al.  Critically Reassessing Tropospheric Temperature Trends from Radiosondes Using Realistic Validation Experiments , 2009 .

[33]  Leopold Haimberger,et al.  Homogenization of Radiosonde Temperature Time Series Using Innovation Statistics , 2007 .

[34]  J. Thepaut,et al.  The ERA‐Interim reanalysis: configuration and performance of the data assimilation system , 2011 .

[35]  Roger Saunders,et al.  RTTOV-8-SCIENCE AND VALIDATION REPORT , 2010 .

[36]  Stefano Schiavon,et al.  Climate Change 2007: The Physical Science Basis. , 2007 .

[37]  Ying-Hwa Kuo,et al.  Comparison of GPS radio occultation soundings with radiosondes , 2005 .

[38]  Jens Wickert,et al.  Variability of the upper troposphere and lower stratosphere observed with GPS radio occultation bending angles and temperatures , 2010 .

[39]  Mitchell D. Goldberg,et al.  Error Structure and Atmospheric Temperature Trends in Observations from the Microwave Sounding Unit , 2009 .

[40]  A. J. Miller,et al.  An update of observed stratospheric temperature trends , 2009 .

[41]  Benjamin M. Herman,et al.  Using limited time period trends as a means to determine attribution of discrepancies in microwave sounding unit–derived tropospheric temperature time series , 2008 .

[42]  S. Solomon,et al.  Recent Stratospheric Climate Trends as Evidenced in Radiosonde Data: Global Structure and Tropospheric Linkages , 2005 .

[43]  John R. Christy,et al.  Error Estimates of Version 5.0 of MSU–AMSU Bulk Atmospheric Temperatures , 2003 .

[44]  Lennart Bengtsson,et al.  An observing system simulation experiment for climate monitoring with GNSS radio occultation data: Setup and test bed study , 2008 .

[45]  Dian J. Seidel,et al.  Causes of differing temperature trends in radiosonde upper air data sets , 2005 .

[46]  W. G. Melbourne,et al.  The application of spaceborne GPS to atmospheric limb sounding and global change monitoring , 1994 .

[47]  Christian Rocken,et al.  The COSMIC/FORMOSAT-3 Mission: Early Results , 2008 .

[48]  W. Bertiger,et al.  A technical description of atmospheric sounding by GPS occultation , 2002 .

[49]  Carl A. Mears,et al.  Construction of the Remote Sensing Systems V3.2 Atmospheric Temperature Records from the MSU and AMSU Microwave Sounders , 2009 .

[50]  Ying-Hwa Kuo,et al.  Assessment of radiosonde temperature measurements in the upper troposphere and lower stratosphere using COSMIC radio occultation data , 2009 .