L-band radiometer measurements of soil water under growing clover grass

A field experiment with an L-band radiometer at 1.4 GHz was performed from May-July 2004 at an experimental site near Zurich, Switzerland. Before the experiment started, clover grass was seeded. Thermal infrared, in situ temperature, and time-domain reflectometer (TDR) measurements were taken simultaneously with hourly radiometer measurements. This setup allowed for investigation of the microwave optical depths and mode opacities (parallel and perpendicular to the soil surface) of the clover grass canopy. Optical depths and opacities were determined by in situ analysis and remotely sensed measurements using a nonscattering radiative transfer model. Due to the canopy structure, optical depth and opacity depend on the polarization and radiometer direction, respectively. A linear relation between vegetation water-mass equivalent and polarization-averaged optical depth was observed. Furthermore, measured and modeled radiative transfer properties of the canopy were compared. The model is based on an effective-medium approach considering the vegetation components as ellipsoidal inclusions. The effect of the canopy structure on the opacities was simulated by assuming an anisotropic orientation of the vegetation components. The observed effect of modified canopy structure due to a hail event was successfully reproduced by the model. It is demonstrated that anisotropic vegetation models should be used to represent the emission properties of vegetation. The sensitivity of radiometer measurements to soil water content was investigated in terms of the fractional contribution of radiation emitted from the soil to total radiation. The fraction of soil-emitted radiation was reduced to approximately 0.3 at the most developed vegetation state. The results presented contribute toward a better understanding of the interaction between L-band radiation and vegetation canopies. Such knowledge is important for evaluating data generated from future satellite measurements.     

Microwave (1-100 GHz) dielectric model of leaves

A semiempirical formula for the complex dielectric permittivity of leaves from different plants is found from a comparison of published measurements covering the frequency range from 1 to 100 GHz. The explicit parameters are the dry-matter fraction m_d of the leaf and the permittivity ϵ_SW of saline water with a salinity of about 1 percent. The physical part of the formula is its basis on ϵ_SW while the empirical part is its linearity with m_d. The formula is applicable to fresh leaves; their m _d values are in the range 0.1d<0.5. A test indicates that besides the m_d variation and the spectral dependence the formula also describes the temperature variation correctly     

The effect of work ethic on employees' individual innovation behavior

The present study examines the previously untested effect of work ethic on individual innovation behavior. These entrenched personal values that may remain unaffected by organizational constitution are suggested to shape a person's inclination to engage in innovative action. Deploying partial least squares (PLS) structural equation modeling (SEM), we show that being self‐reliant and time‐efficient positively influences employees' innovation behavior, while an attitude toward hard work and leisure has a negative impact. Moreover, self‐reliance, leisure orientation, and centrality of work are positively moderated by fair salary, a specific form of relational reward that previously has been identified as an antecedent of motivation. The work at hand thus contributes to extant research by enhancing knowledge about the antecedents of innovative behavior, showing that inherent work‐related values matter. As such, the study demonstrates the importance of considering the linkage of personal differences and motivational factors when examining the complex processes of individual innovation behavior.     

Testing a New Model for the L-Band Radiation of Moist Leaf Litter

The crown vegetation of a deciduous forest is known to be semitransparent at low microwave frequencies, and leaf litter covering the forest soil has been recognized to have a significant impact on ground emission. The proposed approach for modeling the L-band radiative transfer through leaf litter consists of an isotropic effective medium approach for the litter permittivities, a coherent radiative transfer model for computing the coherent reflectivities from dielectric depth profiles, and an averaging procedure for computing the reflectivities determining the field-scale brightness temperatures. Evaluations were performed for the case of leaf litter on top of a conducting wire grid (litter-grid formation) and for litter on underlying soil (litter-soil formation). A model sensitivity analysis was performed with respect to parameters characterizing litter thickness variations and boundary roughness. For the litter-soil formation, the model was rather sensitive to local irregularities at the air-to-litter boundary. Modeled microwave signatures reproduced the major features of the measurements performed on a site comprising a litter-grid formation. Under dry conditions, the investigated litter layer was nearly ldquoinvisible.rdquo When the same litter layer was wetted, it acted as an important radiation source to be taken into account for the quantitative remote soil moisture detection of forested areas. Under certain conditions, the simulations revealed an increasing brightness when the litter is wetted prior to the underlying soil. Further wetting of the litter-soil system then resulted in a decreasing brightness as expected for increased moisture. Such effects are important to know to avoid misleading interpretations of L-band signatures.