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The BOREAS Intensive Field Campaign #2 1996

[July 8, 1996 to August 9, 1996]

BOREAS Intensive Field Campaign #2 (IFC-2 '96) officially ran from July 8 through August 9, 1996. IFC-2 '96 concentrated on understanding energy-water-carbon exchanges between the boreal forest and the atmosphere, and in gathering supporting airborne and satellite remote sensing data. Some 120 scientists and five research aircraft worked at the two BOREAS study areas: the Southern Study Area (SSA) near Prince Albert, Saskatchewan, and the Northern Study Area (NSA), 400 miles away to the north-east, in Thompson, Manitoba.

Site Status

In the SSA, two towers were manned and working since early in the season: the TF-1 crew were at the Old Aspen (SSA-OA), and the TF-9 crew at the Old Black Spruce site (SSA-OBS). These tower sites were the pivots for a continuously orbiting swarm of Terrestrial Ecologists (TE-2, TE-4, TE-5, TE-6, TE-7, TE-10, TE-12), balloon sondes (TF-7), hydrologists (HYD-1, HYD-9) and remote sensing scientists, including Don Deering with PARABOLA (RSS-1). Dave Fitzjarrald and Ricardo Sakai (TF-8) installed ceilometers and digital sky cameras at the SSA-OBS and NSA-OJP sites to support the boundary layer work.
In the NSA, all four TF sites were operating -- NSA-OBS (TF-3), NSA-OJP (TF-8), NSA-Fen, and NSA-YJP (TF-10). The Trace Gas Biogeochemistry group (TGB) were in the NSA in force again -- TGB-1, TGB-3, TGB-4, TGB-5. A schedule of radiosondes was working at both study areas; these were complemented by the ceilometers, flux towers and flux aircraft to study boundary layer processes. Work proceeded pretty much as planned on all fronts with only minor glitches; some preliminary results are discussed later in this report.

Aircraft Operations

IFC-2 started off with about ten days of mixed, cloudy weather. The NASA C-130 (equipped with ASAS and SLICER) and the Canadian Navajo aircraft (equipped with CASI) were not able to acquire any data until 7/18, when they covered the NSA, and 7/20 when some sites in the SSA were overflown. The NASA ER-2, equipped with the AVIRIS and MAS sensors, was available for flights from 7/29 onwards.
The two other BOREAS aircraft are equipped to study the lower atmosphere. The Canadian NRC Twin Otter is practically a flying laboratory, able to measure surface-atmosphere fluxes of heat, water vapor and CO2, and many other things. It flies low (about 100 feet AGL) over the forest and can measure fluxes over areas of 2 km to several hundred kilometers. The "Eyeball" aircraft, a twin-engined PA-34 (AFM-14), was used in 1994 to carry out weather and site reconnaissance flights. In 1996, it is equipped with a CO2 analyzer and has been used to make measurements of regional CO2 gradients and vertical profiles over the study areas. Preliminary data analyses show that regional CO2 fluxes can be estimated from successive profile flights made following the mean wind. The Twin Otter and Eyeball flew almost every day between 7/9 and 7/18, when the Eyeball pilot (Piers Sellers) left the site in preparation for moving away from NASA/GSFC.

Preliminary Results

During IFC-2 '96, the TF teams saw the very high H-fluxes and low LE-fluxes that generated such surprise in 1994 (Bowen ratios greater than 2 were and are common. ). Water was freely available and spring was late this year; but we still saw the 'green desert' effect. The CH4 fluxes observed by the TGB teams started up in a serious way on 06/08/96 and followed their usual Hollow (high flux) and Hummock (low flux) pattern.
The TF-1 group at the SSA-OA saw large LE fluxes, in contrast to all the groups working at the coniferous sites. These were matched by much higher (about a factor of 10) stomatal conductances. The total LAI at SSA-OA was an impressive 5 to 6, including the understory. At the SSA-OBS site, the TF-9 team measured fluxes since March -- the system 'woke-up' on 3/23 and has been ramping up since. A tethered balloon worked well there, in spite of having to fight a stiff nocturnal jet at about 250 feet AGL. A number of teams (TF-9, TE-6, TE-12) measured understory and overstory C-fluxes and conductances, as well as sampling the undercanopy light regime. Moss fluxes are being measured -- so far, it looks like moss accounts for about 15-25% of the C-uptake at the SSA-OBS. The Twin Otter team (AFM-4) showed some recent analyses of the BOREAS-94 data. Bowen ratios over SSA-OA were typically 0.3-0.5 (jives with this years data too) and Fc values of 0.7-0.85 mg m-2 s-1, were observed. (By contrast, for SSA-OBS they estimate Fc=0.2-0.25 mg m-2 s-1). For the AFM-14 (Eyeball) CO2 flights, the inflight calibration rig allowed measurement accuracy to about 0.05 ppm CO2. 110 flight hours of data have been collected and the results are being analyzed. Large regional gradients in CO2 concentration are very obvious. Carlos Nobre, Dave Fitzjarrald, Piers Sellers, and Ray Desjardins are now intrigued about the prospect of using similar equipment (Eyeball + CO2 analyzer + calibration rig) to do large-scale carbon budgets for Amazonia in LBA.

Dr. Forrest Hall's Mid-IFC Report

On 7/25/96 (mid IFC-2 '96), Dr. Forrest Hall wrote:
"The second half of the 1996 BOREAS IFC-2 is going well although from the beginning of the campaign, an extended period of cool, cloudy weather has hampered aircraft operations -- the good news is that this weather is in stark contrast to the hot, dry, smoky weather encountered during the same period of 1994. The contrast is important to understanding how energy, water, CO2 flux and ecosystem function respond to widely different climatic regimes. The other good news is that no fires have been reported near either the southern or northern study areas.
In spite of the cloudy weather, BOREAS operations has utilized its short-range weather forecasts and excellent radio and telephone communication to take advantage of brief periods of clear weather. In the northern study area near Thompson, Manitoba the long-range ability of the NASA C-130 (based in the south) was used to acquire a complete ASAS remote sensing data. On Wednesday, July 25 the C-130 had taken off and aborted a mission over the southern study area following significant cumulus development. Forrest Hall, who had flown to the northern study area, was in the field at the Old Black Spruce site there when Ops radioed him at about 10:30 in the morning that the C-130 was aborting in the south. Based on clear weather in the north that had developed as a result of an unexpected weak high-pressure ridge, and a quick weather update to ascertain that the site would likely be clear for a few more hours, a field decision was made to send the C-130 north. (This was relayed from Forrest to NSA-Ops by radio, who phoned SSA-Ops, who radioed up the change in plan to the airborne C-130. The complete communication loop, (over 400 miles and through these intermediaries) was done within 2 minutes)". One hour later it arrived to clear skies and completed northern data acquisition for the ASAS.
ASAS data collection in the southern study area is still only about 60% complete. The Canadian Navajo Chieftain with the CASI multispectral scanner on board has also acquired partial data sets in the south and the north. The Canadian Twin Otter has acquired several good data sets of regional energy, water and CO2 flux in the south. We are expecting enough clear weather in the remaining 15 days of the IFC to complete the IFC with 100% of our objectives achieved. Aircraft missions to measure dynamic changes in the atmospheric CO2 concentration were successful and no more measurements are scheduled until October.
On the ground, a significant increase in bear population is making field measurements much more interesting. Black bears and their cubs have been spotted frequently around the sites in both the south and north. A few days ago, Dr. Tom Gower, University of Wisconsin, having lunch at the southern Old Black Spruce site, returned from a temporary diversion to find one sharing his lunch. Other investigators have been tuning in heavy metal on the radio in an attempt to repel the critters (seems to work). Otherwise, improvements in the experiment design from 1994 seem to be working well and the new measurements should permit a much more complete understanding of the ecosystem components of the carbon budget (moss, soil, wood, leaves).

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Last Updated: April 25, 1997