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RATPAC-B

Radiosonde Atmospheric Temperature Products for Assessing Climate dataset B (RATPAC-B) contains data for individual stations, as well as large-scale arithmetic averages corresponding to areas used for RATPAC-B. ​A collaborative effort by NOAA scientists collected observations at 85 stations using hydrogen-filled weather balloons equipped with a radiosonde, providing data from 13 atmospheric pressure levels and near-global coverage. RATPAC-B is one of two distinct datasets that emerged from a need for a radiosonde time series that was less influenced by inhomogeneities. 

The station data consist of adjusted data produced by Lanzante et al. (2003; hereafter LKS) for the period 1958–1997 and unadjusted data from the Integrated Global Radiosonde Archive (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.

Methods

The First Differencing ("FD") method used for RATPAC-A does not allow the production of individual station time series. Thus, scientists created a set of updated station time series to provide alternative large-scale mean time series for comparison with the FD time series. This is done by appending monthly mean station data from IGRA for 1997–present to the corresponding data modifications for both liberal and conservative (LIBCON) adjusted LKS station time series for 1958–1997. After 1997, there is no adjustment applied for inhomogeneities. Note that, as in RATPAC-A, the LKS authors preferred to use the LIBCON subset, one of several available versions of the LKS adjusted data.

The NOAA team combines the 00Z and 12Z observations where both are available. For consistency, only observation times from the IGRA data are used that are also present in the LKS adjusted station data. (Station data for the two observation times are also available separately). To minimize the discontinuity at 1997, adding a factor equal to the difference between the means of the IGRA and LKS data for 1996-1997 to the IGRA monthly means is necessary. The effect is to shift the IGRA data so that the means of the two datasets for the last two years of the LKS time series are equal. If both time series are present for fewer than nine months in those two years, the LKS authors use the period 1990–1997 instead.

LKS found a discontinuity at one or more levels at approximately 14 stations but removed data after the discontinuity rather than adjusting it because adjustment was not feasible. There is no appending after 1997 to avoid reintroducing known inhomogeneities for those stations in the IGRA data for those levels in creating RATPAC-B. Extension of four of the possible 85 stations (Preobrazheniya Island, Russia; Chetyrekhstolbovoy, Russia; Mould Bay, Canada; and Ashabad, Turkmenistan) is not necessary because they have no data after 1997. Four other stations (Abidjan, Cote d'Ivoire; Honiara, Solomon Islands; Bellingshausen, Antarctica; and Molodezhnaya, Antarctica) have closed since 1997.

The result is a set of station time series for 1958 through the present with no adjustments after 1997. Hemispheric, global, tropical, and extratropical means created from these station time series are available for comparison with RATPAC-A.

References

Lanzante, J.R., S.A. Klein, and D.J. Seidel, 2003: Temporal homogenization of monthly radiosonde temperature data. Part I: Methodology. Journal of Climate16, 224-240, http://dx.doi.org/10.1175/1520-0442(2003)016<0224:THOMRT>2.0.CO;2.