HadAT2 Radiosonde Data

HadAT2 temperatures are provided as monthly anomalies with respect to the monthly 1966-1995 climatology from the year 1958 to present (10° longitude by 5° latitude grid on nine pressure levels). A detailed description of the construction of the HadAT2 data set was given by Coleman and Thorne (2005) and by Thorne

Table 1 Characteristics of the original data sets including information on version and horizontal resolution as well as available time period and basic sampling (Steiner et al. 2007)

Data set characteristics

Table 1 Characteristics of the original data sets including information on version and horizontal resolution as well as available time period and basic sampling (Steiner et al. 2007)

Data set characteristics

Horizontal

Time period

Basic sampling

Data set

Version

resolution

monthly data

per day globally

CHAMP RO

CCR v2.3

10° zonal means

09/2001-12/2006

~ 150 profiles

SAC-C RO

06/2002-08/2002

~ 150 profiles

GRACE RO

06/2006

~ 150 profiles

COSMIC RO

12/2006

~ 200 profiles/satellite, 2 satellites used

ECMWF

T42L60

10° zonal means

09/2001-01/2006

~ 8 000 grid points, 4

T42L91

02/2006-12/2006

times/day

MSU/AMSU

RSS v2.1

2.5° lat x 2.5° lon

11/1978-12/2006

~ 30 000 TLS observations

UAH v5.1

2.5° lat x 2.5° lon

12/1978-12/2006

HadAT2 MSU

HadAT2

5° zonal means

01/1958-12/2006

1-2 soundings, 676 stations

et al. (2005b). Standard deviations of global monthly temperature anomalies of radiosonde time-series are about 0.45 K in the stratosphere (Seidel et al. 2004).

Sampling errors become important in the Southern Hemisphere where not all latitude bands are represented and above 100 hPa where there is a significant reduction of measurements. Due to systematic uncertainties (daytime biases) and limitations in the homogenization method trends from HadAT2 are potentially underestimated in the tropical troposphere (McCarthy et al. 2008). This problem may be overcome with new adjusted radiosonde time series (Haimberger 2007; Haimberger et al. 2008) which will be better suited for future climate studies.

Synthetic MSU temperatures based on HadAT2 were available from the Hadley Centre/Met Office, UK, at www.hadobs.org. We used monthly-mean zonal-means at 5° latitude resolution for TLS, which were available for January 1958-December 2006. The data set characteristics are summarized in Table 1.

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