| Sensors | Rate | # | Make | Location | Height** |
| 3-Dimensional sonic anemometer model K | 10 | 2 | Applied Technologies | flux twr | 10m, 15m |
| 3-Dimensional sonic anemometer model K* | 10 | 1 | Applied Technologies | walkup twr | 10m |
| 3-Dimensional sonic anemometer research grade | 12 | 1 | Solent | walkup twr | 10m |
| Fast-response temperature | 20 | 3 | Atmos. Instrum. Res | flux twr | 10m |
| flux twr | 15m | ||||
| walkup twr | 10m | ||||
| Fast-response humidity Kr hygrometer | 20 | 2 | Campbell Scientific | flux twr | 10m, 15m |
| Fast-response humidity infrared hygrometer | 10 | 1 | Applied Applications | flux twr | 10m |
| Fast-response CO2 model 6151 | 10 | 1 | Licor | walkup twr | 10m |
| FSSP 15 channel* | 10 | 1 | PMS------? | walkup twr | 10m |
| Particle volume monitor* | 10 | 2 | Gerber inc------? | flux twr / walkup twr | 10m, 15m |
| PCNC1* | 1 | 1 | TSI------? | walkup twr | 3 m |
| PCNC2* | 1 | 1 | TSI------? | walkup twr | 3 m |
| Ozone* | 1 | 1 | Thermo Electron------? | walkup twr | 3 m |
| Wind speed and direction propvane | 1 | 6 | NCAR | prop twr | 1.5m, 5m, 7.5m, 10m, 12.5m, 15m |
| Platinum resistance thermometer and humiter psychrometer | 1 | 6 | NCAR | psyc twr & prop twr | 1.5m, 5m, 7.5m, 10m, 12.5m, 15m |
| Pressure sensor barometer | 1 | 1 | NCAR | psyc twr | 1.5m |
| Pyranometers | 1 | 2 | Eppley | Radiation stand | 1m >canopy |
| Pyrgeometers | 1 | 2 | Eppley | Radiation stand | 1m >canopy |
| Net radiometer Q5 | 1 | 1 | Micromet Systems | Radiation stand | 1m >canopy |
| Surface infrared radiometer | 1 | 1 | Everest Interscience------? | under canopy | 45° downlook |
| Photosynth. active radiometer | 1 | 3 | Eppley | near rad stand | up-, down-, thru-, canopy - looking |
| Soil temperature multiplexer | 1 | 12 | NCAR | Duff | 1, 3, 5, 7cm deep |
| Leaf mold | 1, 3, 5, 7cm deep | ||||
| in stump & tree | |||||
| Soil heat flux | 1 | 3 | Micromet Systems | Duff | 8cm deep |
| Leafmold | 8cm deep |
** all heights are relative to the level of the base of the prop tower
Sonic anemometers
Four sonic anemometers were deployed for the CACHE94 project. Two ATI K sonic anemometers, each associated with a PVM, were mounted on the flux tower. A Solent 3D sonic anemometer and the OSU ATI were mounted on the rotating boom of the walk-up tower. In general the systems on the flux tower were used to calculate the flux gradient of cloud droplets and the systems on the walk-up tower were used to determine the size dependant flux of cloud droplets. The orientation of the sonic anemometers was determined by optically sighting the transducer mounts using a theodolite. Because of the restricted access on the ridge top there was difficulty in making these sightings. Noise and spiking occurred when wind driven cloud water penetrated the electronics of the ATI anemometers. On many occasions the electronics were inspected for moisture and in some cases liquid water was found. Electronic card edges were cleaned and transducers reseated. An electrical grounding problem occurred for the boom-mounted anemometers. The pivoting sleeve electrically insulated the boom and a hard-wire ground had to be provided. This was done on 6 Sept''94. (see logbook#282) As the entire research program depended so critically on the operation of the sonic anemometers the devices were rigorously maintained.
Fast thermometers
The fast thermometers performed well throughout the deployment with only one instance of needed replacement.
Fast Krypton hygrometers
Campbell Scientific Krypton hygrometer had persistent problems due to the high moisture environment. Their electronics were not adequately sealed against water penetration and when the electronics became moist the noise level increased. Attempts were made during the deployment to achieve a better seal but this was not completely successful. The lenses scaled in the high humidity and constant exposure to liquid water. It was found necessary to swab the lenses at least once a week. Green scum of some kind appeared to grow around the lenses and this needed to be cleaned away. Early in the deployment, during ops1, the mounting of the hygrometers was changed to align the optical path horizontal rather than vertical. This was done in an attempt to reduce water pooling on the lenses. It had some effect but the sensor still accumulated water during cloud events. Eventually both Krypton sensors failed and the Analytic Applications infrared hygrometer was used to measure water vapor.
Fast Analytic Applications infrared hygrometer
This sensor was installed on the ASTER array to be tested as part of an arrangement between OSU and Analytic Applications. Although the sensor was not as rapid in its response (no information beyond 1 Hz) it was capable of surviving the adverse moisture conditions. At the end of the deployment it was used to calculate moisture fluxes.
Fast CO2 sensor
The sensor was supplied by ASTER and was maintained by Peter Anthoni of OSU. The sensor was installed in the seatainer and sample air was drawn from the vicinity of the OSU ATI sonic anemometer through 15 m of high density polyethylene tube. The delay was measured to be 1.4 seconds. The sensor was zeroed by switching the intake flow through a canister containing sodalime. The solenoid switching was actuated under command of the OSU PC. This OSU PC output a mode signal to define these periods. Calibration checks performed after jday 241, when calibration gas became available, indicated that the atmospheric CO2 was 355 +_ 10 ppm. After jday 229 record was kept of the sample air flow rate and the Licor measurement cell temperature. The sensor sometimes suffered from aspiration of water along the sample tube and from incomplete zeroing due to channeling of air flow when the zero cannister was horizontal. These problems were overcome by maintaining a loop in the intake line and by mounting the zero cannister in a vertical position.
FSSP
The Particle Measurements Systems Forward Scattering Probe, model FSSP-100ER, was operated, calibrated and maintained by OSU. The probe was interfaced with a PMS card in the OSU PC which then forwarded the counts and housekeeping data to ASTER via a serial line to the ADAM. The FSSP segregated the individual counts into 15 channels. The sensor could be operated in two size range modes allowing the aerosol/hydrosol size distribution to be resolved either as 2- 32 microns or 2-47 microns. In addition to the counts in each size range, five house keeping messages were recorded: range, integration time, total strobes, electronic dead-time and valid strobes. ASTER software was then used to calculate other hydrosol moments viz. droplet volume/size distributions.
PVMs
The Particle Volume Monitor is a laser diffraction instrument which continuously determines the extinction of a collimated laser beam over the open 30 cm horizontal path-length orthogonal to the wind direction. With the zero correction derived from measurements made in clean air the extinction resultant from the interposition of hydrosols is proportional to the total volume of the water droplets within the beam volume. A translucent glass disk can be manually interposed in the optical path to yield a calibration signal equivalent to some given droplet volume.
The two PVM were used during CACHE94 to define the vertical water droplet gradient generated by the deposition flux of cloud droplets resulting from the interception of the cloud by the forested slopes. During the CACHE94 deployment the two PVM's were often moved from one location to another to undertake intercomparisons and to compare the PVM measurement against the FSSP measurements. The record of their sucessive movements within the ASTER array is outlined below and is illustrated schematically in Figure 7.
Ozone sensor
The Dasibi ultraviolet absorption sensor was maintained by Dave Covert of the Atmospheric Sciences Department of the University of Washington. A fault in the sensor sometimes caused a sudden offset to develop in the data.
Prop-vanes
The prop-vanes were beset with problems during the CACHE94 deployment. The desire to achieve >1Hz data rate resulted in a serial communication overload of the already fully dedicated marigold ADAM. Transferring the prop data to the ADAM daisy alleviated this difficulty. Throughout the project the props suffered from the problem of water penetration due to wind driven cloud conditions. Attempts to seal the prop bodies were made but with uneven results. An additional mishap occurred when strong easterly winds caused the hauling line to tangle with the propellers resulting in damage to several of the sensors. Attention must be given to these difficulties when the prop-vane data is used.
Psychrometers
The psychrometers too had a problem with wind driven cloud causing water penetration into their electronics. Throughout the deployment psychrometers needed to be brought down from their mounts to be dried out and sometimes replaced.
Barometers
In general the pressure sensor performed well throughout the deployment.
Radiation sensors
The radiation array needed to be positioned in order to achieve measurements representative of the forested slope of Cheeka Peak. An approximately fifteen meter long trail was cut through the vegetation down the south slope of the ridge. The depth of the vegetation, the height of the canopy above the surface, was approximately three meters. The slope of the surface at the location of the radiation stand was approximately 25o - 30o, necessitating extreme measures in erecting the radiation stand. The top bar of the radiation stand was leveled to within a few degrees and the integrated radiometer array was adjusted to level within one degree of horizontal. The down-looking radiometers were only one meter above the top of the canopy of the Salal bushes. At several meters distance two top spikes of Grand Fir reach above the level of the up-looking radiometers. The effect of this particular deployment of the radiometer array would not have imposed any peculiarity on the value of the down-welling radiation. However for the value of the upwelling radiation there are constraints and the legitimacy of the radiation measurements is questionable.
Pyrgeometers
The down-looking pyrgeometer experienced a loss of power for the compensation circuit when its internal battery failed on jd 234. The battery was replaced on jd 236.
Pyranometers
The pyranometers appeared to have no problems during CACHE94.
Net radiometer
The value of the net radiation appeared to have an especially high value compared to our past experience and we had to adjust the amplifier gain to compensate for this. The high value was rationalized as due the efficient absorption by the dark canopy and canopy holes.
Surface temperature
The Everest infrared temperature sensor was mounted below the radiation stand viewing several square meters of the surface of the organic mulch at an angle of 45°.
Photosynthetically active radiometer, PAR
Three photosynthetically active radiometers were initially deployed at the top of the southern slope near the edge of the canopy. They were each horizontal to within one degree. One was deployed atop a stump with full sky view, and the other two were deployed within the canopy of a Salal bush. On jday 236 the PAR sensors were moved onto and below the radiation stand. Two sensors were mounted on a wooden board that extended ~1 m out from the horizontal beam of the radiation stand. One faced upward, the other downward. The third sensor was placed below the canopy in the vicinity of the radiation stand.
Soil sensors
The surface below the canopy was not well defined. Rather than a simple soil level the surface graded from stems, fallen branches, dead logs, decomposing leaves, duff and finally, after many centimeters of organic material, to mineral soil. Two soil heat flux and temperature arrays were installed in a variant of the conventional manner. This was done in the vicinity of the radiation stand in one area of decomposing leaves and another area of duff (purely organic soil without significant leaf structure). A third set of temperature sensors were installed in dead and living wood: one in the surface of a dead log resting on the surface, the second in the trunk of a six centimeter diameter living tree thirty centimeters from the surface and another in the same tree at ten centimeters from the surface.
The soil temperature probes were connected to the data system via a four channel multiplexer. The multiplexer circuitry failed several times and had to be repaired.
Soil samples
Because the surface and above-surface vegetative cover was so inhomogenous there was no regimen of soil moisture determinations during the CACHE94 deployment. Only a limited number of samples were analyzed for moisture content. From an area alongside the trail samples of organic surface material were taken to the depth of eight or so centimeters. These were then weighed when first taken, were dried at 110°C and were reweighed.