D. L. Nelson

MISR Aerosol Product Attributes and Statistical Comparisons With MODIS

In this paper, Multi-angle Imaging SpectroRadiometer (MISR) aerosol product attributes are described, including geometry and algorithm performance flags. Actual retrieval coverage is mapped and explained in detail using representative global monthly data. Statistical comparisons are made with coincident aerosol optical depth (AOD) and Angstrom exponent (ANG) retrieval results from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The relationship between these results and the ones previously obtained for MISR and MODIS individually, based on comparisons with coincident ground-truth observations, is established. For the data examined, MISR and MODIS each obtain successful aerosol retrievals about 15% of the time, and coincident MISR-MODIS aerosol retrievals are obtained for about 6%-7% of the total overlap region. Cloud avoidance, glint and oblique-Sun exclusions, and other algorithm physical limitations account for these results. For both MISR and MODIS, successful retrievals are obtained for over 75% of locations where attempts are made. Where coincident AOD retrievals are obtained over ocean, the MISR-MODIS correlation coefficient is about 0.9; over land, the correlation coefficient is about 0.7. Differences are traced to specific known algorithm issues or conditions. Over-ocean ANG comparisons yield a correlation of 0.67, showing consistency in distinguishing aerosol air masses dominated by coarse-mode versus fine-mode particles. Sampling considerations imply that care must be taken when assessing monthly global aerosol direct radiative forcing and AOD trends with these products, but they can be used directly for many other applications, such as regional AOD gradient and aerosol air mass type mapping and aerosol transport model validation. Users are urged to take seriously the published product data-quality statements.

Example applications of the MISR INteractive eXplorer (MINX) software tool to wildfire smoke plume analyses

The Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard Terra acquires imagery at 275-m resolution at nine angles ranging from 0° to 70° off-nadir. This multi-angle capability facilitates the stereoscopic retrieval of smoke heights associated with near-source plumes. A new visualization and analysis program called MISR INteractive eXplorer (MINX) takes advantage of wind-direction information inherent in smoke plumes from active fires to determine plume heights and wind speeds at higher resolution and with greater accuracy than provided by the standard, operational MISR product. Among the software tools many features are several designed for in-depth study of plumes, including animations of the nine MISR camera images that provide a visual 3-D perspective, and interactive digitization of plumes in order to automatically retrieve heights and winds. Aerosol properties from MISR, and fire power based on infrared brightness temperatures from MODIS (also on Terra) are archived along with the retrieved height and wind data. MINX retrievals have sufficient spatial detail to provide valuable input to studies of plume dynamics as well as large-scale climatological studies. Current efforts are focusing on fires in North America, but application to other areas of the world is also envisioned. Case study examples will be presented to illustrate MINX capabilities.

MISR Stereo Heights of Grassland Fire Smoke Plumes in Australia

Plume heights from wildfires are used in climate modeling to predict and understand trends in aerosol transport. This paper examines whether smoke from grassland fires in the desert regions of western and central Australia ever rises above the atmospheric boundary layer. Three methods for deriving plume heights from the Multi-angle Imaging SpectroRadiometer (MISR) instrument were utilized: (1) the MISR standard stereo-height algorithm; (2) the MISR enhanced stereo product; and (3) the MISR INteractive eXplorer (MINX) v.1 tool. To provide context and to search for correlative factors, stereo heights were combined with fire radiant energy flux from the Moderate Resolution Imaging Spectroradiometer instrument, atmospheric structure information from the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis project model, surface cover from the Australia National Vegetation Information System, and forward and backward trajectories from the National Oceanic and Atmospheric Administration Hybrid Single-Particle Lagrangian Integrated Trajectory model. Although most smoke plumes concentrate in the near-surface boundary layer as expected, some appear to rise higher. Smoke that gets above the boundary layer will travel farther, remain in the atmosphere longer, and therefore have a larger environmental impact. It was previously thought unlikely for grassland fires to inject smoke above the boundary layer. Our findings suggest that climate modelers should reevaluate common assumptions about the heights of smoke plumes when producing aerosol transport models involving grassland fires. A closer examination of grassland fire energetics may also be warranted.

RVS WFIRST sensor chip assembly development results

Raytheon Vision Systems (RVS) has been developing high performance low background VisSWIR focal plane arrays suitable for the NASA WFIRST mission. These near infrared sensor chip assemblies (SCAs) are manufactured using HgCdTe on CdZnTe substrates with a 10 micron pixel pitch. WFIRST requirements are for a 4k x 4K format 4-side buttable package to populate a large scale 6 x 3 mosaic focal plane array of 18 SCAs. RVS devices will be compatible with the NASA developed FPA 4-side buttable package, and flight interface electronics. Initial development efforts at RVS have focused on a 2k x 2k format 10 micron pixel design based on an existing readout integrated circuit (ROIC) to demonstrate desired detector material performance at a relevant scale. This paper will provide performance results on the RVS efforts. RVS has successfully developed multiple 4k x 4k 10 micron pixel ROICs and we plan to demonstrate readiness to scale our design efforts to the desired 4k x 4k format for WFIRST in 2016.