Chapter 6: The Birth of the Instrument Section

At that time much importance was attached to the significance of the pressure tendency, the change in atmospheric pressure over a period of three hours. The rate of change of pressure was more important than the pressure itself. It seemed to me that a device giving the rate of change of pressure would be simpler than trying to calculate the difference between two readings of the barometer over a three hour interval

When I considered the measurement of pressure at an elevated station like Alice Springs I could see that it would be preferable to obtain equipment that measured station level pressure very accurately.

One complication was that at stations like Alice Springs the atmospheric pressure was obtained from a barometer at 2 000 feet elevation. The station level pressure was determined and then a height correction was added to obtain sea-level pressure, this correction being dependent on the air temperature at Alice Springs. Then to get the pressure tendency you took the difference between these two fictitious sea-level pressures. It was ridiculous. Much later, well after I left the Bureau, Bill Gibbs saw the futility of the system and changed the method of reducing pressure to mean sea-level so it was not dependent on air temperature.

The system used at that time to reduce pressure to a fictitious value at mean sea level seemed to be all wrong but I couldn't convince anyone that it was silly.

In 1937 there was no Instrument Section in the Bureau of Meteorology. In that year there were many unserviceable instruments in an instrument store in the Bureau headquarters at No 2 Drummond Street. That store was controlled by the Climate Section and was demolished to make room for the new wing which was to be added. Nothing was being done to repair Bureau instruments. There were no standard instruments to check the calibration of those used in the observing network. All barometers, barographs, thermometers, thermographs, anemometers and pilot balloon theodolites were imported from overseas. We bought about five new barometers a year.

Bureau of Meteorology