The Integrated Surface Flux Facility during CASES99


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Introduction

This document is a standard product of NCAR/ATD/ISF which gives an overview of the measurements taken using the Integrated Surface Flux Facility (ISFF) and conditions during the CASES99 field experiment.

If you reached this page from a search engine, click here to see the full report, with frames.

Data Access

NCAR ATD data for CASES-99 from the main tower and 6 surrounding stations are available in several forms:

Field Logbook

Also available is a computer-readable logbook of comments noted by ISFF personnel.

Status of 5-minute Statistics

Update Feb 11, 2005: Long-wave radiometer values during operations were added along with Tdome and Tcase values corrected for the various problems mentioned on the WWW page.

On May 11, 2001 new versions of the 5-minute statistics were made available on the web in NetCDF and ASCII form. The following corrections were applied to the new statistics.

Location

ISFF operated 6 10m towers and one 55m tower in a tightly spaced array (sites 1, 2, 3, 4, 5, 6 and 55 shown in the Site Plan). These were in the NE corner of section 2, T28S R6E (the corner of 120th and Ellis Rd), about 5 km SE of Leon, Kansas (about 50 km W of Wichita, Kansas). The approximate locations of all sites were: I think that the 55m tower location was from hand plotting on a map and the site 1-6 locations were from the last GPS value on tear-down. However, the radial positions should be more accurate. GPS positions noted during the experiment were:

Since the two GPS positions for site 1 appear to agree well, we can adjust a grid to agree with it. A set of values which are centered on the GPS position for site 1 and are consistent with the radial positions from the 55m tower are:

This array was developed to identify the length scales in three-dimensions of events, such as drainage currents, which may pass through the array. The surface was grass rangeland, which was relatively short since cows grazed it until 2 weeks prior to field operations. Prior to the experiment, the view from 1/2 mile west of this corner was: ENE, ESE, and SE.

The base trailer was located at the NW corner of 120th and Ellis, in the yard of an abandoned house.

Sensors

A diagram of the sensors on the 55m tower is available. Generally, there is a wind and temperature measurement every 5m, with turbulent wind, temperature, and humidity measured at least every 10m. A boom mounted at 47m has a pair each of upward and downward-looking longwave radiometers. These measurements will be combined with those from similar radiometers mounted on 4 stands near the surface to attempt to measure the radiative flux divergence at night.

We are acquiring data from several user-supplied sensors on the 55m tower:

We also are acquiring data from microbarographs owned by Carmen Nappo at tower sites 4, 5, and 6.

A thermocouple array will be deployed on the 55m tower by Jielun Sun, with a self-contained data system.

Table of Variables

This table lists all variables that were sampled by the ISFF system during CASES99.

Known Instrument Problems

These are the general comments from sensor summaries which are at the end of the logbook. Refer to these logbook entries for more details.

Sensor Maintenance

The sonic anemometer booms on the main tower were raised for sensor maintenance from time to time. Maintenance on the 6 PAM stations may have required that the mast be lowered. Either of these actions rotates the sonic anemometer so that the w axis has a large horizontal component. The obvious signature of these periods are anomalous sigma-w (variable w'w' in the 5 minute data). These periods have not been edited from the data, in either the 5 minute statistics or the high rate data. Most of the maintenance periods are documented in the field logbook but probably not all. If you see questionable sigma-w, check the field logbook for entries concerning maintenance of the sonic anemometer, fast water vapor or CO2 sensors, or hot wire anemometers.

Rain

From the logbook, there appear to have been 3 significant rain events during CASES99: During the September events, our gauges were not connected to our data system since their data loggers were in use for the radiometer intercomparison. The October event wasn't seen in the data, possibly because the storm stopped our data systems. The data from stns 1&2 show small events earlier in October, but these may be spurious. Thus, the entire rain gauge data set probably is useless.

Sonic Anemometers

We had several configuration, electronics, and transducer problems with the sonics. Of the 9 NCAR sonics deployed, only 4 were never changed. The most serious probably was the 10m ATI which was misconfigured to report like a UW array and was used until 10 Oct. We might be able to recover these data.

All of the sensors used from other institutions (4 CSAT3s and 1 ATI K-probe) worked normally.

T/RH

Two sensors had problems during CASES99. Stn3 was noted to have had a bad fan from 29 Sep-9 Oct (possibly due to the rain on 28 Sep). 15m had a weak fan and old RH probe, which were replaced on 12 and 20 Oct, respectively.

Stn 5 died due to cable problems which were fixed 4 Oct. The data that are present should be good.

Radiometers

A complex set of radiometers was deployed during CASES99 to attempt to measure heating in the nocturnal boundary layer due to the flux divergence of longwave radiation. Unfortunately, there were several problems in this deployment: Fortunately, all of these are correctable in post-processing, though this has not yet been done (6/02).

Prop-vanes

There was one prop failure noted during CASES99 (probably due to rain) which caused a loss of most data from 15m on the 58m tower between 28 Sep and 9 Oct. Station 5 lost data due to S-bus cable problems (I think) which were fixed 4 Oct.

Wind directions from the tower appear not to have been very accurate. However, the boom angles were shot twice and differed by only 37 minutes at worst.

Wind directions from sites 1-6 were better behaved, with differences typically less than 3 degrees. Site 3 was the worst, with directions consistently about 3 degrees counterclockwise from the average of the rest. It is possible that this difference is real (since it was close to a gully). [Though it was site 2's boom angle that was different by 3 degrees during the two shoots.]

Everest Infrared Surface Temperature

The Everest at stn 3 died during the rain on 27-28 Sep. It was replaced 29 Sep.

Chronology

[expected] Day: Action

Data Processing Notes

Time Jumps

Our data systems synchronized periodically to GPS time, as per the agreement between CASES99 investigators and our standard practice. The EVE data systems used for stns1-6 synchronized every 3 hours to GPS. The ADAM data systems on the 58m tower synchronized every 4 hours to our base computer, which in turn synchronized periodically to GPS. This has the potential to have time run "backwards", though we usually hope that the update rate is fast enough to make the clock update less than one sample period (50ms).

However, for the files on Oct 14, 00:00 UTC, our data show that some of the stations had "extra" samples, indicating that the EVE clocks were running fast and that the update rate was not sufficient. On this day, the number of extra samples at 20 samples/s was:
s1 3 samples
s2 5 samples
s3 2 samples
s4 3 samples
s5 -1 samples
s6 5 samples
cosmos (1.5-20m) 755ms
daisy (10,20m hotwire; 15,25m props) 801ms
marigold (40m hotwire; 30,35m anem.) -176ms
ragwort (40-55m) 1163ms
This is only one example of the time differences and drift amounts were different at other times. In general, these drifts can be expected to change at least as a function of temperature.

For flux computations, it is only important that data be synchronized within a particular data system to better than one sample period, which is always the case for the CASES99 (and other ISFF) data sets. Therefore, we haven't attempted to "fix" these time tags. However, those investigators looking at event propogation between data systems or high-rate time series across the 3 or 4-hour boundaries to sub-second accuracy need to be aware of these time jumps.

Daily Weather Plots

Click on the following to obtain once/day plots for several important measured variables. Most plots have 2 frames, with the top frame representing the measurements made on the 55m tower and the bottom frame those from the 10m towers. Each plot represents 24 hours of data, beginning and ending at 10am CDT. Please read the scales carefully for more details.
October 
Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
10  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
11  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
12  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
13  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
14  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
15  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
16  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
17  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
18  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
19  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
20  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
21  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
22  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
23  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
24  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
25  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
26  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
27  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
28  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
29  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
30  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil
31  Spd Dir T MR P u* w'w' w'tc' w'h2o' w'co2'/rain R Rnet/Tsfc Soil

Other plots

Integrated Sounding System Plots

There are two ISS operating for CASES99: Smileyberg (ISS1) and Eldorado (ISS3). Profiler, surface, and GLASS data are transferred to ATD from each site every 6 hours and plotted. Plot images are arranged by date. For the moment, access to the plots is restricted. If you notice any problems, contact granger@ucar.edu.

No other plots yet. (Please suggest formats for plots you would like to see.)


Last modified: Wednesday, 17-Sep-2014
© NCAR/Earth Observing Laboratory
This page was prepared by Steven Oncley, NCAR Research Technology Facility