GEWEX Software

The software used to run the GEWEX systems is entirely Linux-based and has been developed from scratch to meet the needs of ATDD. The configuration of a typical Linux-based GEWEX system is pictured below:

Main computer: Shuttle SpaceWalker Mini-Barebones System with 250 MB Internal Zip Disk. This is a neat computer box, measuring 270 mm x 190 mm x 170 mm. It provides a VIA chipset and supports Intel PIII/Celeron/VIA C3 processors. It has two PC133 memory slots, an onboard 2D/3D graphics engine, two onboard IEEE 1394 ports (FireWire), four Universal Serial Bus (USB) ports, one onboard 10/100 MB LAN port, and one onboard AC '97 audio interface. It also includes S-video and TV-out jacks, two 3.5" drive bays, one 5.25 inch drive bay, and one PCI slot which utilizes a riser card.

Serial Interface: Keyspan USB 4-port serial adapter. This provides four RS-232 serial ports in an easily expandable box. The com port connections are described below:

Com 1 - RM Young ultrasonic anemometer. The sonic provides 10 Hz U, V, W winds and air temperature. In addition, an ATDD IRGA <hyperlink> is used to measure CO2 and H2O concentrations through the sonic anemometer's built-in A/D system.

Com 2 - Campbell Scientific CR10/23X Data Logger. The data logger collects up to 15 channels of analog data and stores at 1 Hz. All data collected by the data logger are downloaded to the Linux computer once per day. Typical data measured include soil moisture and temperature, mean wind speed and direction from an RM Young propeller anemometer, rainfall data, solar radiation, and air pressure and temperature.

Com 3 - Olympus Camedia digital camera. This camera provides images of the site once per hour from 8:00 am until 6:00 pm. These images are archived on the 250MB removable Zip disk.

Com 4 - Motorola Cell-Modem back phone. The cellular phone modem is connected to Com 4 allowing remote access from a dial-up line. Routine data downloads and maintenance is performed using dial-up services provided by Kermit.

The Linux software has been developed in-house and the latest version is available for download here <hyperlink>. Download the README file <hyperlink> here for complete directions on how to install the software package.

REA Applications
An extended application of the GEWEX hardware and software involves the use of Relaxed Eddy Accumulation to measure fluxes of trace gases that cannot be easily measured at high frequency in real-time (e.g. Mercury, Methane, Sulfur, etc). Click here for a description of the REA process <hyperlink>.

The software control for the REA system is quite unique and simple. The control of the up, mid, and down sampling valves is performed using the RS-232 control lines CTS (Clear-To-Send) and DTR (Data-Terminal-Ready). By toggling these two lines high and low, four combinations can be obtained. This is easily accomplished in software and conveniently uses the vertical winds measured from the sonic anemometer. Below is a screen shot of the REA Linux system:

<Picture will be taken in the future>