A Ground-Based Network for Atmospheric Pressure Fluctuations

Abstract

In 1992, a surface-based, mesoscale microbarograph array with four pressure sensors was installed near the Hohenpeißenberg, southern Germany, and has since been in continuous operation. In this paper, a description of the sensors, the network, and the data evaluation is given. The sensors are based on conventional microphone techniques, where the pressure difference between the ambient air and an internal reservoir is measured. The latter is connected with the former by an adjustable needle valve. Pressure fluctuations are resolved with an amplitude resolution of 3 µb and between periods of 2 s and 30 min. Sensors are calibrated by lifting over a given height. Time constants are determined with a pressure-pulse technique and are on the order of 300 s. Data are sampled at 1 Hz and are transmitted on-line to a central data processing unit. Each sensor is installed at the bottom of a 1.50-m-high container, which is mounted flush with the ground. The sensor is thermally insulated and protected such that the air exchange between the sensor and the atmosphere is kept to a minimum. The average sensor separation is 1 km. A wavelet technique is applied to the data from each sensor to isolate the gravity wave events from background fluctuations. It is a general finding that gravity waves are found in wave packets with a maximum of four to five wavelengths only. Wave events are clearly recognizable by their sinusoidal shape. Furthermore, frontal passages, positive and negative solitary waves, and turbulent wind situations can be identified from the pressure signals. Most of the time, background signals are characterized by well-correlated pressure fluctuations of several-microbar amplitude. However, they have irregular shape probably due to the existence of drifting density inhomogeneities.