**6. Discussion**

The atmosphere plays a fundamental role in regulating life on Earth. Changes in atmospheric composition can and do affect surface temperatures, hydrology, radiation budgets, weather, and even climate. Therefore, understanding the complex exchanges occurring between the atmosphere and surface requires accurate measurements of the variables characterizing both; for example atmospheric constituents, surface temperatures, and albedo. Quantifying these variables provides the necessary inputs for modeling the dynamic interactions and potential outcomes that result from changes in the relative proportions of atmospheric constituents. In light of the growing evidence for anthropogenic induced climate change, accurate characterization of the impact humans are having, both directly and indirectly, on altering Earth's systems is critical to guiding mitigation policy.

To that end, fire radiative energy may provide a efficient and accurate tool to monitor and measure biomass consumed and emissions from fire events. In order to be truly effective some of the idiosyncratic issues that plague sensors and algorithms need to be addressed, but perhaps most importantly, at least a global scale, is dealing with missed fire detections. For this, more comprehensive and distributed validation must occur.

In order to truly validate FRE estimates, greater spatial and temporal resolution data are needed. The evaluation of the FRE estimates with SEVIRI data offered a comparison with FRP retrievals made at higher temporal resolution, but incurred the downside of coarser spatial resolution. Future endeavors would include a scaling approach to test the temporal trajectory of instantaneous fire energy and total fire radiative energy released from a fire event. This would include the use of *in situ* observations, perhaps with a combination of field and laboratory experiments to reconcile differences between these two approaches. The next tier of retrievals would be from airborne observations, perhaps including both tower platforms (for small scale fires) and unmanned aircraft. The Ikhana unmanned airborne vehicle (UAV) used by the fire research at NASA AMES offers some opportunities in this regard. Recent field work demonstrated that while monitoring FRP from a helicopter seems ideal, many factors can limit the success of this tactic and that greater flexibility in choice of fires to observe and timing allowed for observation is needed. Moderate to high spatial resolution satellite observations would be employed in the next scaling layer and allow for greater spatial coverage while being constrained by higher spatial and temporal observations. To that end, geostationary satellite observations would cap the scaling approach, providing high temporal (15 – 30 minute) retrievals to aid in characterizing the diurnal cycle of fire radiative power as has been shown in this research. Incorporating sensors such as the Geostationary Operational Environmental Satellites (GOES) would offer greater spatial coverage beyond the SEVIRI sensor. Careful consideration of the limitations of comparison between sensors at multiple scales would obviously be needed (*Schroeder et al.,* 2005).

Other considerations worth pursuing to improve FRP retrievals from the MODIS sensor include parameterization of the sub-surface organic layer burning. According to French et al. (2004) surface organic layer burning is largest source of uncertainty in boreal biomass burning emission estimates. Page et al. (2002) estimated 0.19-0.23 Gt of carbon released to the atmosphere from peat combustion during 1997 Indonesian fires. Their estimates were based on peat thickness, pre-fire land cover, and burnt area data collected from ground measurements and Landsat TM/ETM imagery. Cloud cover has already been revealed by Schroeder et al. (2008) to limit fire detection capabilities for Brazilian fires. The spatial resolution of MODIS is another limitation to detecting fires in peatlands (and thus FRP estimation) as shown by Siegert et al. (2004). Developing a connection between field estimates of surface and sub-surface organic burning, burned area, and FRP would allow for parameterization of this component of fire radiative energy.
