The Hamburg Weather Mast

Since 1967 the Meteorological Institute of the University of Hamburg operates a scientific, meteorological measuring site in Billwerder, a suburb of Hamburg, Germany. It is located on an area of the NDR (the North German Broadcasting Company) and consists of devices at a 300 m tall broadcasting mast as well as at our own 10 m mast nearby on a meadow. Additionally, several ground-based devices are installed outside the operator's hut beneath the tall mast. In 1994 completely new equipment was installed, since 1995 measurement runs continuously until today.

Geographic position and surroundings

The Hamburg Weather Mast is located in Hamburg-Billwerder, about 8 km south-east of the city centre. (city map). The geographic coordinates of the tall mast are 53 31' 09,0'' N and 10 06' 10,3'' E, and 53 31' 11,7'' N and 10 06' 18,5'' O of the 10 m mast respectively. The site is located only 30 cm above German reference surface, so a device's height above ground is nearly identical to its height above mean sea level.

The surroundings of the area are characterised by a mixture of agricultural land, fallow ground, spoil areas, and sparsely populated hamlets in the East, and industrial sites with mostly low buildings in the West. So the site is located directly in the transition region between rural and urban kinds of landuse.

The meteorological equipment: devices, heights and measured variables

The tall 300 m mast

The tall mast has six walkable platforms in height levels 50, 70, 110, 175, 250, and 280 m that can be accessed by a lift inside the mast. On each platform there is attached a south-oriented cantilever arm that holds the instruments. The distance between mast and instruments is nearly 6 m, the diameter of the mast is 2 m. Each platform, except that at 70 m, is equipped with the same instruments: A ventilated thermometer (Pt100) for measuring the air temperature, a (relative) humidity sensor (Humicap) and a 3d-ultra-sonic anemometer (METEK USA-1) for wind speed and direction as well as turbulence quantities like sensible heat flux and momentum flux. At 50 up to 250 m there are fast CO2/H2O analyzers added to the anemometers for latent heat and carbon dioxide fluxes (see below). On the 70 m level there is a thermometer only. On the 110 m level a dew point sensor (VTP6) is installed as a reference device.

The 10 m mast

The 10 m mast on the meadow holds the following devices: The instrumentation in the level at 10 m equals those ones on the platforms of the tall 300 m mast (temperature, humidity, wind, turbulence). In the height of 2 m temperature and humidity is measured, too. There is mounted an infra-red thermometer that "watches" the ground for measuring the surface temperature. On top of the 10 m mast there are two irradiation sensors for downward short-wave and long-wave irradiation from the upper hemisphere (Kipp & Zonen Pyranometer CMP21 and Pyrgeometer CGR4).

Measuring of turbulence

In 2000 the meteorological equipment on both masts was enhanced by five ultra-sonic anemometers/thermometers (USAT). They are mounted on top of the 10 m mast and on the platforms at 50, 110, 175, and 250 m. In the mid of 2010 we added a sixth USAT at the 280 m platform. These devices do not only measure wind speed and direction, but also the (virtual) temperature and the turbulent fluctuations of the three-dimensional wind vector. From these, amongst others the turbulent heat and momentum fluxes can be determined. Additionally, the fastest gust in each minute is determined out of the wind speed, that is measured with a 20 Hz sample rate. For that, we define the largest gust in a minute as the largest mean value over 3 seconds.

The ultra-sonic anemometers have replaced the prior used cup anemometers and wind vanes.

For measuring the latent heat flux, in addition to the sensible heat flux, fast infra-red CO2/H2O analyzers (Licor LI-7500) have been mounted directly at the 3d anemometers at 10 up to 250 m in 2013. These analyzers measure the concentration of water vapor and carbon dioxide simultaneously with the anemometer's wind vector.

A transmitter unit of a scintillometer is mounted at the 50 m level headed to the Geomatikum where the receiver is located on the roof. Over this path-length of about 10 km the vertical turbulent heat flux is measured and, in addition, the crosswind, too.

Propagation path of the scintillometer from Hamburg Waether Mast to Geomatikum (10 km)

Instruments at ground-level

A pressure sensor is located in the operator's hut (Vaisala PTB). Nearby there are devices for measuring clouds and precipitation.

The tipping bucket rain gauge registers the amount of rain based on a resolution of 0.1 mm. The gauge can be heated in winter, so snow can also be measured.

The duration of precipitation can be registered exactly by an infra-red rain sensor (IRSS 88), a photoelectric relay counting the rain drops falling through an aperture of 12 cm 3 cm. For each minute this device gives a 1 in case of rain and a 0 otherwise.

In the mid of 2008 we mounted a micro rain radar (METEK MRR-2). This device measures the rain rate, the fluid water content and the falling velocity of the rain drops in steps of 35 m up to 1000 m.

A ceilometer determines the height of the cloud base by measuring the run duration of an infra-red laser beam reflected by fluid water in the atmosphere up to 7500 m.

Data sampling and transmitting

All data is sampled by several computers inside the operator's hut. Most devices are queried once a second, but only averaged values are stored each minute. The ultra-sonic anemometers run on a sampling frequency of 20 Hz, the turbulent variables are calculated based on intervals of 1 and 5 minutes. The sampled data will be uploaded via DSL to our server in the Geomatikum every 15 minutes, where additional operations are made for creating the graphics on this website and storing the data in our archive.

The following tabular gives an overview over all height levels and measured variables. Alltogether there are about 35 independent measuring devices.

Variable/Device         Height (m)
--------------------------------------------------
Temperature             2 10 50 70 110 175 250 280
Relative humidity       2 10 50    110 175 250 280
Dew point                          110
Wind and turbulence       10 50    110 175 250 280
CO2/H2O concentration     10 50    110 175 250
Short-wave irradiation    10
Long-wave irradiation     10
Atmospheric pressure    2
Amount of rain          2
Duration of rain        1
Surface temperature     0
Height of cloud base    30 to 7500
Micro rain radar        35 to 1050
Scintillometer          50
Weather camera (webcam) 50
Photos: Ingo Lange
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