ISFF Deployment for SGS 2000

This page contains information being used to plan this field experiment, which is scheduled for Sept. 2000. Expect it to change signficantly during the year 2000.


Here is a partial list of phone numbers and some driving directions.


Here is a "contact sheet" of photographs taken by NCAR folks during SGS. Also, the Johns Hopkins folks have their own set of photographs. Expect more.


SGS requires that the wind and temperature fields be spatially filtered in at least two dimensions -- along the wind and across the wind. Using Taylor's hypothesis, filtering in the direction of the wind can be accomplished by filtering in time. However, to filter across the wind, multiple sensors placed perpendicular to the wind direction are needed. A digital filter can be made which reasonably approximates a Gaussian filter using a minimum of 5 sensors. Since SGS needs to apply a double filter to calculate second moments, e.g. stress, an overlapping array of five 5-sensor filters is needed at the same height. This can be achieved with a line of 9 sonic anemometers, which also is suitable for measuring lateral gradients (or differences) of filtered quantities.

SGS also would like to measure the vertical difference between the filtered fields. This requires an additional set of 5 sensors at a different height.

Tower array

The core measurements for SGS will be from an array of 14 sonic anemometers. These 14 will consist of one set of 9 anemometers at one height and a second set of 5 anemometers at another height. Both arrays will be equally spaced in a line set up perpendicular to the wind. To minimize the number of towers -- especially if individual tower are used -- the spacing at one height should be double the spacing at the other height. It is desirable to keep the ratio of spacing to height the same at both heights, so one height must be double the first.

Vertical arrays of temperature, wind, and flux sensors will be placed on three additional nearby towers to determine the mean turbulent structure of the surface flux layer.

Site considerations

In order for the tower data to be used as a filter in the cross-wind direction, the towers must be aligned as close as possible (on the order of 10 degrees) perpendicular to the wind. Since we do not want to move the towers frequently (very labor intensive), we need the wind to come from a consistent wind direction. Wind climatology in the San Joaquin Valley shows that winds are from 330 degrees (close to NW) much of the time (both day and night) in most regions.

Since SGS will follow EBEX, we will know what the mean wind direction was for the exact SGS site for the previous month.

The SGS measurement height requirements are height above the effective zero-plane of the flow field. Thus it is preferred to make the measurements in a fallow field to avoid the additional zero-plane displacement height due to a crop canopy. We would also like to have a uniform surface that extends in the upwind (to the north-northwest) direction as far as possible, but hopefully for a minimum of 1 mile.

To reduce the amount of effort, we hope to operate SGS from the same base trailer as EBEX. However, this will require a fortuitous combination of several sections of cotton adjacent to several sections of fallow, wheat, or other crops to be harvested by September. (An ideal layout is shown here.) If necessary, we will move the base trailer as well, though we still would prefer to work with only one landowner.

Site possibilities

We have three potential sites for SGS. These are listed in my site report. Housing will be at the Edgewater apartments.

Logistics considerations

The EBEX field experiment will end data collection on August 24, allowing the transition of equipment to SGS to begin on August 25. It is anticipated that SGS data collection may begin by September 3 or (hopefully) earlier.