A GROUND-BASED NETWORK FOR ATMOSPHERIC-PRESSURE FLUCTUATIONS

In 1992, a surface-based, mesoscale microbarograph array with four pre ssure sensors was installed near the Hohenpeissenberg, southern German y, and has since been in continuous operation. In this paper, a descri ption of the sensors, the network, and the data evaluation is given. T he 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 res olution of 3 mu b and between periods of 2 s and 30 min. Sensors are c alibrated by lifting over a given height. Time constants are determine d 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 proc essing unit. Each sensor is installed at the bottom of a 1.50-m-high c ontainer, which is mounted flush with the ground. The sensor is therma lly insulated and protected such that the air exchange between the sen sor and the atmosphere is kept to a minimum. The average sensor separa tion is 1 km. A wavelet technique is applied to the data from each sen sor to isolate the gravity wave events from background fluctuations. I t is a general Ending that gravity waves are found in wave packets wit h 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 c an be identified from the pressure signals. Most of the time, backgrou nd signals are characterized by well-correlated pressure fluctuations of several-microbar amplitude. However, they have irregular shape prob ably due to the existence of drifting density inhomogeneities.