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quality checks and are stored in digital form (which also applies to all past rec 
ords). 
Before new instruments are installed and used operationally, they are tested at 
special test facilities (e.g. at Hamburg) to ensure that they comply with all re 
quirements to replace the previous instrumentation (precicion, accuracy, availabil 
ity, and so on). 
With this, it is ensured that all primary weather stations (Wst I [meteorological 
watch office], Wst II [automatic weather office]) mostly comply with GCMPs and 
the secondary weather station which are operated by voluntary observers with 
some restrictions (Wst III [voluntary weather station], Nst(A) [automatic precipita 
tion station] and Nst(k) [conventional precipitation station]). 
(b) Incorporating atmospheric pressure sensors into drifting buoy programmes (A5) 
Germany runs no own drifting buoys on its own, but contributes to EUCOS/E- 
SURFMAR. 
(c) Ensuring availability of three-hourly mean sea level pressure and wind speed and 
direction data from GSN stations (A10) 
The GSN stations are equipped with automatic sensors. These data (e.g. mean 
pressure at sea level, wind speed and direction) are hourly exchanged on the 
GTS. 
(d) Implementing a reference network of high-altitude, high-quality radiosondes (A16) 
In 2007, WMO assigned the Lead centre of the GCOS Reference Upper-air Net 
work (GRUAN) to the MOL-RAO. DWD has employed three new staff for this ob 
ligation at Lindenberg. This was completed on 1 July 2008. Currently, the guide 
lines for running GRUAN reference observations are drafted. MOL-RAO will also 
be among the first reference stations in the frame of GRUAN. Currently, regular 
reference observation of water vapour in the upper troposphere and lower strato 
sphere using different type of sensors are conducted. This work is supported by 
systematic investigations of instrument performance in a climate chamber. 
(e) Operating the WWW/GOS radiosonde network in full compliance with the GCMPs 
and coding conventions (A17) 
Being a GUAN station, MOL-RAO complies with the GCMPs and coding conven 
tions. All other measured with use routinely the same radio-sonde for at least two 
soundings a day (till 30 km). 
(f) Submitting metadata records and inter-comparisons for radiosonde observations 
to the specified international data centres (A18) 
Currently, a database is installed at MOL-RAO that will contain all metadata of 
GRUAN stations as well as the data from radiosonde (and other) inter-comparison 
campaigns. 
(g) Developing a network of ground-based Global Positional System (GPS) receivers 
for measuring water vapour (A21) 
Germany is operating a ground-based network of Global Positional System (GPS) 
receivers since 2000. The responsible and processing centre is located at the