Daniel Fisher

Automated Stereo Retrieval of Smoke Plume Injection Heights and Retrieval of Smoke Plume Masks From AATSR and Their Assessment With CALIPSO and MISR

The longevity and dispersion of smoke and associated chemical constituents released from wildfire events are dependent on several factors, crucially including the height at which the smoke is injected into the atmosphere. The aim here is to provide improved emission data for the initialization of chemical transport models in order to better predict aerosol and trace gas dispersion following injection into the free atmosphere. A new stereo-matching algorithm, named M6, which can effectively resolve smoke plume injection heights (SPIH), is presented here. M6 is extensively validated against two alternative spaceborne earth observation SPIH data sources and demonstrates good agreement. Further, due to the spectral and dual-view configuration of the Advanced Along-Track Scanning Radiometer imaging system, it is possible to automatically differentiate smoke from other atmospheric features effectively-a feat, which currently no other algorithm can achieve. Additionally, as the M6 algorithm shares a heritage with the other M-series matchers, it is here compared against one of its predecessors, M4, which, for the determination of SPIH, M6 is shown to substantially outperform.

Shortwave IR Adaption of the Mid-Infrared Radiance Method of Fire Radiative Power (FRP) Retrieval for Assessing Industrial Gas Flaring Output

The radiative power (MW) output of a gas flare is a useful metric from which the rate of methane combustion and carbon dioxide emission can be inferred for inventorying purposes and regular global surveys based on such assessments are now being used to keep track of global gas flare reduction efforts. Several multispectral remote sensing techniques to estimate gas flare radiative power output have been developed for use in such surveys and single band approaches similar to those long used for the estimation of landscape fire radiative power output (FRP) can also be applied. The MIR-Radiance method, now used for FRP retrieval within the MODIS active fire products, is one such single band approach—but its applicability to gas flare targets (which are significantly hotter than vegetation fires) has not yet been assessed. Here we show that the MIR-Radiance approach is in fact not immediately suitable for retrieval of gas flare FRP due to their higher combustion temperatures but that switching to use data from a SWIR (rather than MWIR) spectral channel once again enables the method to deliver unbiased FRP retrievals. Over an assumed flaring temperature range of 1600–2200 K we find a maximum FRP error of ±13.6% when using SWIR observations at 1.6 µm and ±6.3% when using observations made at 2.2 µm. Comparing these retrievals to those made by the multispectral VIIRS ‘NightFire’ algorithm (based on Planck Function fits to the multispectral signals) we find excellent agreement (bias = 0.5 MW, scatter = 1.6 MW). An important implication of the availability of this new SWIR radiance method for gas flare analysis is the potential to apply it to long time-series from older and/or more spectrally limited instruments, unsuited to the use of multispectral algorithms. This includes the ATSR series of sensors operating between 1991–2012 on the ERS-1, ERS-2 and ENVISAT satellites and such long-term data can be used with the SWIR-Radiance method to identify key trends in global gas flaring that have occurred over the last few decades.

Global warping coefficients for improving ATSR co-registration

Globally applicable warping coefficients for improving the co-registration between the forward and nadir views of the series of Along-Track Scanning Radiometer (ATSR) instruments are presented. The coefficients are derived from a polynomial-based warp, using a least squares fit on a set of automatically detected forward to nadir tie points. In-depth statistical analysis is presented here covering both an independent analysis of the warping coefficients using the Pyramidal-Gotcha algorithm and a global assessment using the Speeded Up Robust Features tie-pointing algorithm. This independent assessment shows that the co-registration between the nadir and forward views improves in all cases to pixel-level accuracy with geometric errors to, at worst, ±0.7 pixel. This global assessment analyses a worldwide distributed tie-point set to assess universal applicability. For Advanced ATSR and ATSR-1, the coefficients provide co-registration accuracies at the pixel level globally. The same is shown to be true for ATSR-2 prior to the gyroscope failure in January 2000.

Global analysis of the improvements in AATSR nadir-forward co-registration following the application of an automated registration algorithm

An automated registration method for the correction of AATSR co-registration is presented. AATSR co-registration between the nadir and forward views is known to be poor, generally greater than 1 pixel. Here we apply the SURF algorithm to automatically generate a set of tie-points between the forward and nadir images. These tie-points are then used to create a set of warping parameters which effectively co-register the forward and nadir images. The warping parameters have been tested globally for a number of years of AATSR data and are shown to provide improved co-registration to less than a pixel in all cases. The same method will, in the future, be applied to the other ATSR instruments which share similar co-registration problems.