1.1.1. Terrain Properties and Characterization

Terrain affects all aspects of Army operations. The effective understanding and use of terrain is critical to military success on the battlefield. It is, in effect, a force multiplier, affecting mission planning, system performance, unit mobility and effectiveness, and training readiness. At present, the Army cannot rapidly and efficiently perform the terrain analysis that is required before personnel, vehicles, and weapons are deployed. A "rapid mapping" capability to remotely sense and interpret the features of and upon the Earth's surface and an automated capability/methodology for handling and analysis of large aggregates of remotely sensed data are critical for the 21^st-century Army. Terrain information may be considered elevation data; soil and environmental characteristics; natural terrestrial features and manmade structures; and urban environments. A capability to remotely sense and interpret the features of and upon the Earth's surface, together with an automated capability/methodology for handling and analysing of large aggregates of remotely sensed data, are critical for the improved terrain characterization capability required for most of the technology areas important to the Army Objective Force. Research related to terrain characterization is directed toward fostering the development of advanced geoscience-based capabilities for the rapid post-acquisition generation, analysis, and utilization of terrain data acquired through remote sensing technology. Characterizing terrain features and conditions from sparse data, plus accurate detecting of short-term dynamic surface conditions and terrain feature change, are high-priority research issues. A problem of particular importance is the accurate remote sensing measurement of soil moisture at the scales of Army operations (e.g., 102-103 m). Knowledge of the properties and phenomenology of the surface and near-subsurface is critical to support military operations on land, ranging from operational mobility, the detection of landmines and unexploded ordinance, natural material penetration/excavation, and military engineering activities to training and testing land sustainability. Effective military action requires a rapid and accurate assessment of the influence of soil and rock properties. Strength and deformation properties of geomaterials are highly variable due to the intrinsic heterogeneity of bedrock geology and soil formation processes and moisture content over variable spatial scales, rock mass competency, and groundwater pressure over small spatial scales. A thorough understanding of the behavior of geomaterials under different environmental and dynamic loading conditions is a critical need for mobility prediction and as input for projectile penetration prediction to destroy hardened and deeply buried targets. Also of concern is the issue that soil and rock properties and behavior measured in the field are typically much different than from those observed in the laboratory. This dilemma has profound consequences for predicting geomaterial behavior. Specific research is need to provide new approaches to (or techniques for) the non-intrusive geophysical characterization of subsurface materials and their spatial distribution; the prediction of location, frequency, and scale of subsurface heterogeneity; the detection and discrimination of buried objects (particularly landmines, unexploded ordinance, hazardous wastes, and contaminant plumes), tunnels and underground structures; and high-resolution field data sets for non-intrusive measurement validation. The ability to discriminate subsurface features and objects in the presence of surface roughness, natural geologic heterogeneity, and anthropogenic clutter requires advanced signal processing and analysis techniques.

1.1.2. Terrestrial Processes and Landscape Dynamics

Environmental factors can directly affect the Army's strategy, mobility, field operations, and logistics. With the expected increased sensitivity of the future Army to these factors, the importance of this information will become even more critical. Therefore, the focus of this research area is the development of an improved understanding of surficial processes within the terrestrial environment that can affect Army operations. The dynamics of natural processes and systems operate over a wide range of scales and are only poorly understood at the time and space scales required by the Army; hence, much of what is needed is a fundamental understanding of the appropriate ways to couple processes of highly differing scales and types. A continuous dynamic interaction takes place between solid earth materials and the most abundant fluids, water and air. A variety of dynamic environmental parameters and conditions affect the performance of geophysical sensors. Fluvial processes are dominant in shaping the continental surface through both erosion and deposition. In more arid regions, eolian processes can give rise to both erosional and depositional landforms. Military problems arising from these interactions include localized flooding in battle areas, deterioration of trafficability, and obscuration from blowing dust and sand. The nearshore zone is a complex boundary region where air, land, and sea interact over a wide range of space and time scales. It is also a region in which incident energy is often dissipated or transformed to motions at other scales. The result is a highly nonlinear, coupled, dynamic system. Surface waves, coastal circulations, and sediment transport all have important impacts on Army operations within this region; however, information on these processes is essentially nonexistent for most areas around the globe. At 0°C, water changes from the liquid to solid phase, resulting in the formation of snow, ice, and frozen ground. Such conditions dramatically alter the battlefield environment and affect the performance of systems and materiel. Icing is a particular issue for aircraft, rotorcraft, optical sensors, and antennas. An improved understanding of the fundamental character and dynamic nature of the surface environment and its evolution through time, as well as the consequences of military interaction with this environment, is essential for the continued development, improvement, and sustainability of Army training and testing activities. In particular, there is a need for the development of first-principle physical/chemical process models and computer-based techniques for monitoring, modeling, and simulating the natural environment, as well as improved technologies and methodologies for environmental characterization and prediction. Special emphasis is given to the need to better understand, model/simulate, and predict those environments/conditions that are most dynamic or restrictive to systems performance or military operations. The development of an improved understanding, physical representation, and quantification of terrestrial processes affecting Army operations are of particular interest to this research area. Improved measurements and theoretical treatments are needed to treat the complex, often nonlinear dynamics governing these processes, which are a result of both physical and biologic processes and the interaction of these processes with terrain evolution. Such processes operate over a wide range of discontinuous time and space scales, which make them extremely difficult to characterize, quantify, and model. Explicit consideration of these processes and their interactions will lead to critically needed improvements in the ability to predict environmental effects on Army operations. Important in this context is research that seeks to explain the response of landscape to modification by Army use and the fundamental nature of subsurface flow and mass transport, and then numerically model these complex processes. Critical to developing an engineering-scale understanding of the properties and behavior of surface environments is a fundamental knowledge about the natural processes that operate on surficial materials at a variety of scales. Field observation, laboratory experiments, and computational modeling must be integrated to solve well-formulated problems. Predictive geotechnical models, based upon well-characterized constitutive relationships, are required to identify controlling processes and parameters across a spectrum of scales. Extreme environments (hot, cold, dry, and wet, or combinations thereof) pose unique challenges to future Army systems and personnel, because deserts, tropics, and cold regions are extremely hostile environments that dramatically affect human and materiel performance, thus, inducing a negative effect on the performance of military systems and operations. Extreme environments also are important because they can exhibit unusual recovery rates following disturbance. Within the U.S., approximately 70% of Department of Defense (DoD) lands occur in highly sensitive arid and semi-arid environments. The character of terrain in arid environments can determine how military operations are conducted on these lands and military activities can directly impact the terrain in a manner that causes both short-term and long-term stresses on the surficial environment and ecosystem. The repeated use of such lands for military purposes, particularly training and testing activities, increases the risk of soil disturbance, damage to vegetative cover, degradation of water quality, and the disruption of animal populations and archeological sites. These impacts can be particularly adverse over the long term as battlefield readiness and sustainable training requirements place significant demands on the delicate terrains that characterize arid and semi-arid environments.

2.2.1. Atmospheric Effects on Sensors and Systems

The Army depends heavily on propagation of electromagnetic and acoustic signals through the atmosphere for detection, ranging, and operation of smart munitions as well as reconnaissance and information dominance of the battlefield. Atmospheric turbulence can severely impact the performance of optical and infrared sensors as well as acoustic detection systems by affecting the propagation, imaging, and coherence of the received signals from active or passive systems. Furthermore the effects of surface and natural environmental conditions on propagation of images and signals must be considered because of the near-ground operation of many Army systems.

2.2.2. Characterization of the Atmosphere at High Resolution

Research efforts concentrate on increasing Army knowledge of physical processes in the atmospheric boundary layer at the engagement scale of the battlefield. This scale, characterized by horizontal distances to 20 km at resolutions at 10's of meters and times of seconds to hours, is the most inhomogeneous and changeable portion of the atmosphere.

The principal research concern is the diurnal evolution of the turbulent and stable atmospheric boundary layer. Research topics span a full spectrum of atmospheric boundary layer dynamical conditions including, but not limited to parameterization and scaling of boundary layer processes for micro-scale and mesoscale predictive models; surface conditions from simple to heterogeneous terrain elevation and slope, vegetation, and moisture; surface energy budgets; scale interactions; temperature and moisture fluctuations, especially as they affect the atmosphere as a medium for propagation of acoustic and electromagnetic signals; and natural or induced obstructions to visibility. A principal focus of the boundary layer dynamics is their application to prediction of the mean and fluctuating concentrations of chemical and biological agents in realistic terrains on appropriate scales.

Comprehensive measurements of wind velocity, temperature, moisture, surface energy exchanges, and fluxes at resolutions showing their scales of variability in the atmospheric boundary layer are essential for advancing understanding of boundary layer processes affecting Army operations and systems. The variables should be measured in space and time to clearly define the evolution of three-dimensional physical processes within a volume of interest. Such measurement programs should highlight both the instrumentation development and the interpretation of the physical processes from the sensed data.

These topics are considered from perspectives of theory, field experiments, and analyses of the faithfulness and validity of models and simulations of these processes. The research results are expected to contribute to improved models of boundary layer processes for visualization and field use through strong interactions with appropriate Army laboratory scientists.