PURPOSE
Monitor meteorological parameters in tallgrass prairie on a long term basis.
LOCATION OF SAMPLING STATIONS ( see Fig. 5)
Headquarters weather station (grid C-16).
Weighing Raingauges:
Headquarters 2 (C-16) 020A (C-30)
002C (M-31) N04D (J-27)
020B (O-28) K04B (T-23)
004B (G-26) N01B (P-23)
N02B (H-22) N04D (L-23)
FREQUENCY OF SAMPLING
Continuous sampling at headquarters weather station. Continuous from April 1 to October 31 for raingauges on prairie.
VARIABLES MEASURED
1) Air temperature at 2 m (C)
2) Relative humidity at 2 m (%)
3) Total solar radiation down (0.3-3.0 fm, cal cm-2 min-1)
4) Wind speed at 3 m (ms-1)
5) Wind direction at 3 m (degrees)
6) Precipitation (mm)
7) Soil temperature (C) at 25 cm (started June 1992)
METHODS
A Campbell Scientific (CR-10) data logger continuously monitors air temperature, relative humidity, solar radiation, wind speed, soil temperature, and precipitation, and samples wind direction at hourly intervals. A microprocessor in the CR-10 manipulates the raw data and outputs the average air temperature, soil temperature, relative humidity, wind speed, total precipitation, solar radiation, and the sampled wind direction each hour. Additionally, every 24 hours daily maximum, minimum, and average air temperatures, soil temperatures, relative humidity, total precipitation, and solar radiation areoutput. The CR-10 data is accessed through a modem in Bushnell Rm 205, usually on a weekly basis. The output from the CR-10 is also recorded on cassette tape (as a backup) and is transferred to a diskette compatible with an IBM-PC compatible when needed. The input and output programs stored in the CR-10 are listed in Fig. 6. See the CR-10 owners manual in Bushnell Rm 205 for specific operation instructions.
Precipitation is measured at headquarters by two weighing raingauges, one with a seven day clock and one with a 24 hour clock (equipped with a wind screen). Additionally, nine other weighing raingauges are installed on the Konza Prairie. Gauges in 020B, 004B, N02B, N04D (upland and lowland), K04B, and N01B have 24 hour clocks for finer resolution of storm events. Gauges in 020A and 002C have seven day clocks. The tipping bucket and the prairie raingauges are not operated during the winter months (November-March).
Routine Maintenance:
Charts on all weighing raingauges require changing each week. Catch buckets in the raingauges are emptied at the time of chart changing except when the headquarters raingauge is winterized with antifreeze (see Belfort manual for details). Clock mechanisms require rewinding each week and pens must be refilled with ink. The cassette tape on the CR-10 is changed every two months but may be left longer if necessary. The solar radiation sensor requires periodic (bi-monthly) checks for dust accumulation or other obstructions.
The CR-10 is battery operated, as is the cassette recorder. The CR-10 output includes the battery voltage every 24 hours and the batteries are constantly charged using a 110 outlet. Desiccant packets should also be changed when necessary. Batteries in the cassette should be changed when the indicator lights indicate low voltage or approximately every four months in summer and every two months in winter.
No periodic maintenance is required for the CR-10, but during the winter months, cold temperatures may render the cassette recorder inoperable. The tipping bucket raingauge should be taken indoors during the winter months and the weighing raingauge at headquarters should have each catch bucket filled with approximately two quarts of antifreeze. The prairie raingauges are sealed with plastic in the winter. Following significant precipitation events, the level of the antifreeze/water mixture in thebuckets should be checked to avoid overflow. The antifreeze/water system should be discarded and refilled if dilution of the antifreeze past levels of protection occurs.
Currently all chart changing and any changing of the cassette tape are done on Tuesdays since this is the day that the NADP samplers are serviced.
