Photo courtesy of NOAA Photo Library
The Team:The Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC) are datasets created through a collaborative effort involving NOAA scientists from the Air Resources Laboratory (Silver Spring, Maryland), the Geophysical Fluid Dynamics Laboratory (Princeton, New Jersey), and the National Climatic Data Center (NCDC) (Asheville, North Carolina).
The Problem:The temporal homogeneity of many radiosonde time series is suspect due to historical changes in instruments and measurement practices. Such changes may introduce artificial inhomogeneities to the time series, making them unsuitable for the study of long-term climate variations, such as through trend analysis.
The Goal:Create time series from radiosonde temperatures that are less influenced by any such inhomogeneities. Two distinct datasets, derived using different approaches, have been created based in large part on the Lanzante, Klein, Seidel (2003) ("LKS") bias-adjusted dataset.
The Data:The resulting datasets, RATPAC A and B, consist of station and regional-mean time series of temperature anomalies that extend from 1958 to present and are updated on a monthly basis. Derived from radiosonde observations taken at 85 of the 87 globally distributed stations used by LKS, the two datasets represent two different combinations of historical LKS-adjusted data and recent data from the Integrated Global Radiosonde Archive (IGRA).
RATPAC-A:Contains adjusted global, hemispheric, tropical and extratropical mean temperature anomalies. From 1958 through 1995, they are based on spatial averages of the LKS adjusted 87-station temperature data. After 1995, they are based on the IGRA station data, combined using a first difference method (Free et al. 2004).
RATPAC-B:Contains data for individual stations as well as large-scale arithmetic averages corresponding to areas used for RATPAC-A. The station data consist of adjusted data produced by LKS for the period 1958-1997 and unadjusted data from IGRA after 1997. The regional-mean time series in RATPAC-B are based on arithmetic averaging of these station data, rather than the first difference method used to create RATPAC-A.
For analysis of interannual and longer-term changes in global, hemispheric and tropical means, we recommend RATPAC-A. For individual station data, monthly data, or regional means on smaller scales, we recommend use of RATPAC-B, with careful attention paid to the potential of inhomogeneities impacting analysis after 1997.