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logo Field Report - Tahoe '99

"Smoke Over Water"

From 11/11 to 11/23/99, Jim Conel and Mark Helmlinger collected field data at Lake Tahoe, California, from a dock near Tahoe City, on the western shore of the lake, and out on the lake itself. Lake Tahoe was chosen as a target for the validation of AirMISR aerosol retreival algorithms. The deep waters of the lake reflect very little sunlight. Any light seen in an image of the lake surface from above can be assumed to be scattered off junk in the air, rather than bounced off the water or something under it. In this way, a dark target makes the math simpler.

The timing of the experiment was decided by the controlled burn schedule of the local forests. We wanted smoke to waft over the lake on an otherwise clear day, making for ideal test conditions. Unfortunately, ideal conditions for a controlled burn meant waiting for wind directions that carried most of the smoke out of the Tahoe basin! Some aerosols did exist over the target at the time of overflight, but from the town's wood stoves, not the fires.

During a previous, unsuccessful deployment to Lake Tahoe, we found a dock which exteded more than 100 meters out into the lake. All of our sky monitoring instruments were mounted together on the dock. An extra sunphotometer and our PARABOLAIII sphere-scanning radiometer were mounted on a large cruise ship, the Tahoe Gal, for the golden day of overflight. The path of the ship during the day was recorded, and we beleive it actually appears in some of the AirMISR images. Special thanks are due to the owner and captain-for-the-day of the Tahoe Gal, Larry Boerner, who patiently took us and our instruments on our own peculiar tour of the lake. For more information about the Tahoe Gal, see: http://www.tahoeguide.com/go/tahoegal

Mark's photos of the experiment & explanations

Our ride for the overflight: The Tahoe Gal
The Tahoe Gal enabled us to make optical depth measurements at the center of the AirMISR target, which was actually offshore a bit. We also made water-leaving radiance measurements as well as PARABOLA sphere radiance measurements while bobbing over the deeper parts of the target area. More photos from aboard the Gal follow . . . The Tahoe Gal enabled us to make optical depth measurements at the center of the AirMISR target, which was actually offshore a bit. We also made water-leaving radiance measurements as well as PARABOLA sphere radiance measurements while bobbing over the deeper parts of the target area. More photos from aboard the Gal follow
Our insruments set up at the end of the State Park dock at Tahoe City
Our suite of non-floating instruments, from left to right: MET station, MFRSR, (my custom cart with crates), PARABOLA, CIMEL, and Auto-Reagan. If the horizon is not too low, these instruments can be placed closer together, as they will appear against the mountains to each other. A bit of a crowd, in any case. Our suite of non-floating instruments, from left to right: MET station, MFRSR, (my custom cart with crates), PARABOLA, CIMEL, and Auto-Reagan. If the horizon is not too low, these instruments can be placed closer together, as they will appear against the mountains to each other. A bit of a crowd, in any case.
Our dock for the duration - photo taken looking east
The State Park we used as a base of operations was closed for the season, and with permission, we kind of took over the end of this dock, some 120 meters long. Security was never a problem, though I did keep a close eye peeled, and many nice people came by to ask good questions. I handed out a lot of brochures. The State Park we used as a base of operations was closed for the season, and with permission, we kind of took over the end of this dock, some 120 meters long. Security was never a problem, though I did keep a close eye peeled, and many nice people came by to ask good questions. I handed out a lot of brochures.
Later in the morning, our instruments soak up the sun
All of our field instruments are solar powered, as shown here. Each has a separate gell cell, charge controller, and one to ten 20W solar panels connected in parallel to keep the battery topped off. Each battery has enough capacity to run its instrument all day without a charge. The solar panels merely save me the trouble of carrying the batteries around to be charged at the end of the day. All of our field instruments are solar powered, as shown here. Each has a separate gell cell, charge controller, and one to ten 20W solar panels connected in parallel to keep the battery topped off. Each battery has enough capacity to run its instrument all day without a charge. The solar panels merely save me the trouble of carrying the batteries around to be charged at the end of the day.
One big fish
The young men in the previous photo were fishing with small poles and trapping crawdads in a cage with chicken necks. They were more suprised than I when they hauled this trout out with low test line. The fish weighed four pounds, I think. The young men in the previous photo were fishing with small poles and trapping crawdads in a cage with chicken necks. They were more suprised than I when they hauled this trout out with low test line. The fish weighed four pounds, I think.
PARABOLA mounted at the end of the dock
We collected PARABOLA data all day long from this location. The water here was about 4 meters deep. You could see the bottom, and it shows up in the data. The water is exceptionally clear in Lake Tahoe. Note the Spectralon panel mounted on the northern side of PARABOLA, rather than the southern, which is the usual way we like to do it. We collected PARABOLA data all day long from this location. The water here was about 4 meters deep. You could see the bottom, and it shows up in the data. The water is exceptionally clear in Lake Tahoe. Note the Spectralon panel mounted on the northern side of PARABOLA, rather than the southern, which is the usual way we like to do it.
Sunrise on a cloudy day, looking east by northeast from base camp
Ah yes, one of the many advantages of waking up before the crack of dawn. Often, morning clouds prevent observations. This was the beginning of a "down day". I finally got to do some laundry. Ah yes, one of the many advantages of waking up before the crack of dawn. Often, morning clouds prevent observations. This was the beginning of a 'down day.' I finally got to do some laundry.
Base Camp, adjacent to Tahoe City, California
Jim Conel pauses to update his notes and reveiw maps at our campground. We had the place to ourselves. How do you like my accomodations? I parked as close to the dock as I could find level ground. I lived in the RV for the duration, keeping an eye on the dock. I have found RV's to be quite handy, and great for hauling all my stuff around to the really awful places I get sent. Jim Conel pauses to update his notes and reveiw maps at our campground. We had the place to ourselves. How do you like my accomodations? I parked as close to the dock as I could find level ground. I lived in the RV for the duration, keeping an eye on the dock. I have found RV's to be quite handy, and great for hauling all my stuff around to the really awful places I get sent.
Our CIMEL, set up at the end of the dock
Our CIMEL sunphotometer and sky radiometer has been modified into a portable campaign-oriented instrument. Added features include anti-tangling cable guides and robust solar panels, as well as a heavy-duty custom tripod mount. Kitted into three tough cases, I can set this instrument up nearly anywhere in an hour without special tools. Our CIMEL sunphotometer and sky radiometer has been modified into a portable campaign-oriented instrument. Added features include anti-tangling cable guides and robust solar panels, as well as a heavy-duty custom tripod mount. Kitted into three tough cases, I can set this instrument up nearly anywhere in an hour without special tools.
Smoke over our Multi-Filter Shadowband Radiometer
In the foreground, our MFRSR does its thing from the end of the dock while a paltry smoke plume is blown out over the lake to the north. The shadowband can be seen moving away from the Spectralon diffuser of the instrument. Two readings are made: Total sky radiance in six spectral bands and (when shaded by the shadowband) the indirect radiance contribution to the Total. In the foreground, our MFRSR does its thing from the end of the dock while a paltry smoke plume is blown out over the lake to the north. The shadowband can be seen moving away from the Spectralon diffuser of the instrument. Two readings are made: Total sky radiance in six spectral bands and (when shaded by the shadowband) the indirect radiance contribution to the Total.
Smoke over the CIMEL, looking southwest
Another controlled burn to the south produce this plume, but not on a day that we could fly the ER-2 with AirMISR aboard, or get a ride on the Tahoe Gal. Sigh. Timing is everything. Another controlled burn to the south produce this plume, but not on a day that we could fly the ER-2 with AirMISR aboard, or get a ride on the Tahoe Gal. Sigh. Timing is everything.
PARABOLA and MFRSR on dock
A view of the same fire, with PARABOLA doing its thing on the right and our MFRSR just making a measurement on the left. View is to the south-southwest. Note the wind direction has changed. One learns patience on field deployments. A view of the same fire, with PARABOLA doing its thing on the right and our MFRSR just making a measurement on the left. View is to the south-southwest. Note the wind direction has changed. One learns patience on field deployments.
Pre-dawn setup of a sunphotometer on the Tahoe Gal
Jim is programming the sunphotometer, telling it when to turn on and how long and often to take data. I have modified this instrument considerably from its original configuration, most notably attaching the control microprocessor to the back of the radiometer head to make it a one-piece instrument. Jim is programming the sunphotometer, telling it when to turn on and how long and often to take data. I have modified this instrument considerably from its original configuration, most notably attaching the control microprocessor to the back of the radiometer head to make it a one-piece instrument.
PARABOLA walking the plank off the bow of the Tahoe Gal
Note the white standard panel at its feet and the white box beneath that which houses power supplies and a Zip drive. PARABOLA runs off of solar-generated 110VAC supplied by long extension cords and can take hundreds of scans a day. Each spherical radiance scan takes about three minutes, and contains 2664 readings at a 5 deg FOV for 8 spectral bands with 20bit dynamic range taken at five degree increments. Note the white standard panel at its feet and the white box beneath that which houses power supplies and a Zip drive. PARABOLA runs off of solar-generated 110VAC supplied by long extension cords and can take hundreds of scans a day. Each spherical radiance scan takes about three minutes, and contains 2664 readings at a 5 deg FOV for 8 spectral bands with 20bit dynamic range taken at five degree increments.
An important meeting
Jim and Larry discuss experiment plans on the upper deck of the Tahoe Gal prior to departure for deep water. Armed with target coordinates from Jim, Larry will pilot us into position with his GPS during the overflight times. Jim and Larry discuss experiment plans on the upper deck of the Tahoe Gal prior to departure for deep water. Armed with target coordinates from Jim, Larry will pilot us into position with his GPS during the overflight times.
The Captain's nest
Larry got us to where we wanted to be, when we needed to be there. Once on location, Jim and I threw him a curveball: Keep the boat turning very slowly, with the sun, so that the shadows on deck always line up the same. This was so PARABOLA data would be easier to use. He did a great job - Thanks Larry! Larry got us to where we wanted to be, when we needed to be there. Once on location, Jim and I threw him a curveball: Keep the boat turning very slowly, with the sun, so that the shadows on deck always line up the same. This was so PARABOLA data would be easier to use. He did a great job - Thanks Larry!
Jim downloading data from one of our sunphotometers
Note the cable from the instrument to the laptop computer Jim is holding. The instrument tracks the sun and collects 10 spectral channels of solar intensity information through the atmosphere. Raw readings are processed to produce optical depth information used to estimate amounts of smoke and dust overhead, among other things. Jim had to restart the machine because it could not keep a sun lock at the rate Larry turned the boat around to leave the dock. No worries - it tracked perfectly thereafter. Note the cable from the instrument to the laptop computer Jim is holding. The instrument tracks the sun and collects 10 spectral channels of solar intensity information through the atmosphere. Raw readings are processed to produce optical depth information used to estimate amounts of smoke and dust overhead, among other things. Jim had to restart the machine because it could not keep a sun lock at the rate Larry turned the boat around to leave the dock. No worries - it tracked perfectly thereafter.
Jim takes notes among a sea of solar panels
We set up our solar power station on the top deck of the Tahoe Gal for the Auto-Reagan, PARABOLA, computers, and cell phone. That way, we were able to run our stuff without Larry having to run the engines. This enabled us to gather a whole day's worth of data in place, even though the cruise was relatively short. We set up our solar power station on the top deck of the Tahoe Gal for the Auto-Reagan, PARABOLA, computers, and cell phone. That way, we were able to run our stuff without Larry having to run the engines. This enabled us to gather a whole day's worth of data in place, even though the cruise was relatively short.
Jim lectures the panel(s)
I put the panels up on chairs to get them out of the shadow of the railing. When the sun angle shifted around so that I turned the chairs to face it, Jim could not resist. Man, talk about a captive audience! You could say they with crystallized with interest. Jim is a radiant speaker - it was an electrifying talk - OK, I'll quit. I put the panels up on chairs to get them out of the shadow of the railing. When the sun angle shifted around so that I turned the chairs to face it, Jim could not resist. Man, talk about a captive audience! You could say they with crystallized with interest. Jim is a radiant speaker - it was an electrifying talk - OK, I'll quit.
A commanding view
Larry peers out from the wheel house of the Tahoe Gal. Visible to the right is the boom arm for the gangplank, so this view is roughly what PARABOLA sees. Smile Larry! Again, our many thanks to Larry's indulgence of our quirky demands, defacing of the Gal by festooning her with instruments, and his good questions and great patience. Larry peers out from the wheel house of the Tahoe Gal. Visible to the right is the boom arm for the gangplank, so this view is roughly what PARABOLA sees. Smile Larry! Again, our many thanks to Larry's indulgence of our quirky demands, defacing of the Gal by festooning her with instruments, and his good questions and great patience.