James A. Brass

Effects of fire severity on nitrate mobilization in watersheds subject to chronic atmospheric deposition.

Severe fires in chaparral watersheds subjectto air pollution from metropolitan Los Angeles mobilized accumulated nitrogen and caused streamwater to be polluted with nitrate at concentrations exceeding the Federal Water Quality Standard. Streamwater NO 3 - concentrations were elevated during peak flows, the largest of which was a debris flow that transported NO 3 - at concentrations as high as 1.12 mequiv/L. Annual NO 3 - loss from severely burned watersheds, averaging 1.2 kequiv/ha, was 40 times greater than that from areas that remained unburned. Fires of moderate intensity produced a more subdued response in stream discharge and soil nitrification and less than one-seventh the NO 3 - loss observed after severe burning

REMOTE MEASUREMENT OF ENERGY AND CARBON FLUX FROM WILDFIRES IN BRAZIL

Temperature, intensity, spread, and dimensions of fires burning in tropical savanna and slashed tropical forest in central Brazil were measured for the first time by remote sensing with an infrared imaging spectrometer that was designed to accommodate the high radiances of wildland fires. Furthermore, the first in situ airborne measurements of sensible heat and carbon fluxes in fire plumes were combined with remote measurements of flame properties to provide consistent remote-sensing-based estimators of these fluxes. These estimators provide a means to determine rates of fuel consumption and carbon emission to the atmosphere by wildland fires as required for assessments of fire impacts on regional air pollution or global emissions of greenhouse gases. Observed fires developed complex fire-line geometry and thermal structure, even as average whole-fire temperatures varied little. Flame temperatures sometimes exceeded 1600 K along the leading edge of actively spreading fire lines, yet >90% of the radiant energy from observed fires was associated with temperatures of 830–1440 K. Fire in a partially slashed forest encompassed a high-intensity flaming front and a trailing reach of residual combustion extending 400 m. Fire fronts in tropical savanna typically formed with little depth and a high proportion of their radiant flux density associated with high temperatures due to low levels of residual combustion. Measured fires had such low and variable radiance compared with that of a blackbody of comparable temperature as to preclude the use of fire radiance at a single wavelength as a measure of fire intensity or temperature. One-half of the radiant flux density from a measured savanna fire was associated with values of a combined emissivity–fractional-area parameter <0.091 m2/m2; for a slash fire this fraction was associated with values <0.37 m2/m2. Observations reported here show wildland fires to be so complex and dynamic as to require frequent high-resolution measurements over their course and duration in order to specify their effects in the environment; an understanding of global fire impacts may require such measurements over a large sample of individual fires.

The Ikhana unmanned airborne system (UAS) western states fire imaging missions: from concept to reality (2006–2010)

Between 2006 and 2010, National Aeronautics and Space Administration (NASA) and the US Forest Service flew 14 unmanned airborne system (UAS) sensor missions, over 57 fires in the western US. The missions demonstrated the capabilities of a UAS platform (NASA Ikhana UAS), a multispectral sensor (autonomous modular sensor (AMS)), onboard processing and data visualization (Wildfire Collaborative Decision Environment (W-CDE)), to provide fire intelligence to management teams. Autonomous, on-board processing of the AMS sensor data allowed real-time fire product delivery to incident management teams on the wildfire events. The fire products included geo-rectified, colour-composite quick-look imagery, fire detection shape files, post-fire real-time normalized burn ratio imagery and burn area emergency response (BAER) imagery. The W-CDE was developed to allow the ingestion and visualization of AMS data and other pertinent fire-related information layers. This article highlights the technologies developed and employed, the UAS wildfire imaging missions performed and the outcomes and findings of the multi-year efforts.

Analysis of Forest Structure Using Thematic Mapper Simulator Data

Remotely sensed data from forested landscapes contain information on both cover type and structure. Structural properties include crown closure, basal area, leaf area index, and tree size. Cover type and structure together are useful variables for designing forest volume inventories. The potential of Thematic Mapper Simulator (TMS) data for sensing forest structure has been explored by principal components and feature selection techniques. Improved discrimination over multispectral scanner (MSS) data proved possible in a mixed conifer forest in Idaho for estimating crown closure and tree size (saplings/seedlings, pole, sawtimber). Classification accuracy increased monotonically with the addition of new channels up to seven; the four optimum channels were 4, 7, 5, and 3. The analysis of TMS data for 123 field sites in Sequoia National Park indicated that canopy closure could be well estimated by a variety of bands or band ratios (r = 0.62-0.69) without reference to forest type. Estimation of basal area was less successful ( r = 0.51 or less) on average, but improved for certain forest types when data were stratified by floristic composition. To achieve such a stratification, sites were ordinated by a detrended correspondence analysis (DECORANA) based on the canopy of dominant species. Within forest types, canopy closure continued to be the best predictor of spectral variation. Total basal area could be predicted in certain forest types with improved or moderate reliability using various linear ratios of TMS bands (e. g., red fir, 5/4, r = 0.76; lodgepole pine, 4/3, r = 0.82).

Perspectives on Fire Management in Mediterranean Ecosystems of Southern California

San Dimas Canyon seems a wild place beyond the reach of civilization. It is home to black bears, gray foxes, Anna’s hummingbirds, scrub jays, and in early summer, a multitude of biting insects. Along the steep, north-facing hillsides, the chaparral has the appearance of an ancient forest. From within the canyon it is difficult to remember that one is less than 7 km from metropolitan Los Angeles. It is also difficult to conceive of the landscape swept by flames 30- or 40-m high, or to visualize San Dimas Creek afterwards scoured by debris flows. Our difficulty in perceiving these catastrophic events makes it difficult to alter their course and consequences because to do so involves substantial cost and risks.

Feature selection and the information content of Thematic Mapper Simulator data for forest structural assessment

The information content of Thematic Mapper Simulator (TMS) data was investigated for a forested region in northern Idaho to determine the sensitivity of TMS data to forest structural characteristics (crown closure and site class). Feature selection performed via principal components analysis and a Monte Carlo simulation indicated that TMS channels 4 (0.77–0.90 μm), 7 (10.32–12.33 μm), 5 (1.53–1.73 μm), and 3 (8.63–0.69 μm) were the four optimal channels for forest structural analysis. These four channels utilized the full spectral capability of the Thematic Mapper, representing wavelengths from the visible, the near-infrared (IR), the mid-IR, and the thermal portions of the electromagnetic spectrum. As the number of channels supplied to the Monte Carlo feature selection routine increased, classification accuracy increased. The information content of the TMS data was analyzed by performing supervised maximum likelihood classifications on three data sets: 1) 7-channel 30-m 8-bit data, 2) the 4-optimal-channel 30-m 8-bit data, and 3) TMS data degraded to Landsat multispectral scanner (MSS)specifications, 3-channel 60-m 6-bit data. The greatest sensitivity to forest structural parameters, which included crown closure, site class, and succession within clearcuts, was obtained from the 7-channel TMS data, the 4-optimal-channel TMS data, and the simulated MSS data, respectively. The increased number of spectral hands was largely responsible for the increased accuracy of the TMS data over the simulated MSS data. The improved spatial resolution of the TMS data did not improve classification performance. Variance within the TMS scene was largely due to the structural characteristics of the forest canopy.

Thermal analysis of wildfires and effects on global ecosystem cycling

Abstract Biomass combustion plays an important role in the earths biogeochemical cycling. The monitoring of wildfires and their associated variables at global scales is feasible and can lead to predictions of the influence of combustion on biogeochemical cycling and tropospheric chemistry. Remote sensing data collected during the 1985 California (U.S.A.) wildfire season indicate that the information content of key thermal and infrared/thermal wave band channels centered at 11.5 μm, 3.8 μm, and 2.25 μm are invaluable for discriminating and calculating fire related variables. These variables include fire intensity, rate‐of‐spread, soil cooling recovery behind the fire front and plume structure. Coinciding Advanced Very High Resolution Radiometer (AVHRR) data provided information regarding temperature estimations and the movement of the smoke plume from one wildfire into the Los Angeles basin.

Estimating fire properties by remote sensing

Contemporary knowledge of the role of fire in the global environment is limited by inadequate measurements of the extent and impact of individual fires. Observations by operational polar-orbiting and geostationary satellites provide an indication of fire occurrence but are ill-suited for estimating the temperature, area, or radiant emissions of active wildland and agricultural fres. Simulations here of synthetic remote sensing pixels comprised of observed high-resolution fire data together with ash or vegetation background demonstrate that fire properties including flame temperature, fractional area, and radiant-energy flux can best be estimated from concurrent radiance measurements at wavelengths near 1.6, 3.9, and 12 pm. Successful observations at night may be made at scales to at least 1 kmn for the cluster of fire data simulated herein. During the daytime, uncertainty in the composition of the background and its reflection of solar radiation would limit successful observations to a scale of approximately 100 mn or less. Measurements at three wavelengths in the long-wave infrared would be unaffected by reflected solar radiation and could be applied to separate flame properties in a binary system of flame and background. However, likely variation in the composition of the background and its temperature limit the approach to measurements that are of high resolution in relation to the scale of the flaming front. Alternative approaches using radiances at wavelengths near 4 and 12 pm alone must fail absent a correction for the background, yet the correction is made imprecise by uncertainty in composition of the background where it comprises more than one-third of a pixel.

Solar-powered UAV mission for agricultural decision support

In September 2002, NASAs solar-powered Pathfinder-Plus UAV conducted a proof-of-concept mission over the 1500 ha plantation of the Kauai Coffee Company (KCC), Hawaii. While in U.S. National Airspace, the transponder-equipped UAV was supervised by Honolulu air traffic as a conventionally piloted aircraft. Two digital camera systems were housed in exterior-mounted environmental pods, and were controlled from a ground station established at plantation headquarters. During four hours on-station, the UAV exhibited the ability to navigate pre-planned flightlines, as well as perform spontaneous maneuvers to collect imagery in cloud-free areas. A line-of-sight (local area network) telemetry system using unlicensed radio frequency enabled rapid image download at rates exceeding 5 Mbit sec -1 . All images were thus available for viewing, enhancing, and printing within a few minutes of collection. During the latter part of the mission, the payload was operated over an established wide area network by an operator located on the U.S. mainland at a distance of 4000 km. The mission demonstrated the ability of a solar-powered UAV, equipped with downsized imaging systems, to monitor a localized region for an extended time period and deliver high-resolution imagery on demand. I. INTRODUCTION

Nighttime UAV Vineyard Mission: Challenges of See-and-Avoid in the NAS

A Nighttime UAV Vineyard Mission will demonstrate the use of a UAV-based thermal infrared imaging system for improved direction of frost damage mitigation efforts in agricultural crops. The UAV selected for this April 2005 mission is the APV-3. A flight height of 8,000 ft is planned, enabling thermal mapping coverage of the largest vineyard in California on an hourly basis. To accomplish the Nighttime Mission, it is necessary to demonstrate that the ground-based autopilot has the capability to see-and-avoid potentially conflicting aircraft in the National Airspace System (NAS). This paper provides a review of a daytime UAV test flight conducted in-visual range over the vineyard in August 2003 and describes additional tests being conducted to satisfy FAA see-and-avoid requirements for the planned out-of-visual range nighttime mission.