A visual scan of the data from March 1988 to December 1990 was undertaken to identify cases where correlations with local phenomena were apparent. The bulk of the correlations found were with wind speed, but a limited number of wind direction and humidity effects were also detected. No correlations with temperature or pressure were visible in this initial examination of the data. When the wind speed rises above a certain critical value, the electric field generally increases sharply with wind speed. The critical wind speed values vary considerably from event to event however and for 30 events specifically analysed, the values ranged from as low as 4 knots to as high as 28 knots. The 'fair weather' electric field at Davis lies between about 80 V m-1 and 250 V m-1. In this example however, the electric field values reached in excess of 3500 V m-1. Local effects of this magnitude are very easy to identify.
There is evidence to suggest that the relative humidity plays a part in determining how strongly the electric field correlates with the wind speed. When the humidity is high, the correlations between wind speed and wind direction are strong, and when it is low, the correlations are weak. Typically for electric field analysis, what appears dramatically correlated in one example is found to be highly variable when a larger number of events are investigated. In an attempt to gain some quantitative measure of the effect of humidity on the electric field. The lower the humidity, the less likely the electric field will be dramatically influenced by the wind speed. There are however, exceptions at both high and low wind speeds.
Data have been converted to ADAS (Antarctic Data Acquisition System) format. Software is available for interpreting this format.
All monthly and annual reports that have been retained are available for download from the provided URL.
The following parameters are logged.
1.0 EXPERIMENTAL PARAMETERS
1.1 PARAMETERS LOGGED
* denotes a channel which is included in the daily plots
Channel No. Parameter
1 Wind Speed *
2 Temperature *
3 Wind Direction *
4 Electric Field, (Most Sensitive) *
5 Electric Field, (3rd Most Sensitive) *
6 Electric Field, (2nd Most Sensitive) *
7 Humidity *
8 Zero Reference Voltage *
9 Box 1 Temperature
10 Box 2 Temperature
11 Atmospheric Pressue (No longer connected)
12 Standard Voltage Reference *
13 Electric Field (Least Sensitive) *
14 Wind Speed (Least Sensitive)
15 Not Used
16 Not Used
3.0 SAMPLE INTERPRETATION OF E.F.M MET INSTRUMENTS
** Humidity equation used is :
Humidity % = (0.020345 * Digital Value) + 38.3 (%)
** Temperature equation used is:
Temperature = (0.03588 * Digital Value) - 60.26 (degrees Celsius)
** Wind speed equation used is:
Wind Speed = (5.474 E-3 * Digital Value) + 10.9 (knots)
** Wind direction equation used is:
Wind Direction = (0.10167 * Digital Value) + 212.4 (Degrees east of north)