At moderate protein inhibitors incident angles, such as those employed in the studies referenced above (e.g., 20�� to 49�� for RADARSAT-1 ScanSAR Wide mode), the bulk of the SAR backscatter is due to surface roughness elements that scale with the radar wavelength projected onto the scattering surface (i.e., Bragg scattering, selleck Pacritinib as opposed to specular and wedge Inhibitors,Modulators,Libraries scattering). Thus, for the ocean surface, those roughness elements include the centimeter-scale waves driven by the near-surface wind. It follows that the variability of normalized radar cross section (NRCS, average backscatter divided by area) on a SAR image of the ocean is a function of the coincident overlying meteorological phenomena. For a recent review of SAR principles, see .
For the remainder of this discussion, Inhibitors,Modulators,Libraries we will focus on moderate incident angle wide-swath SAR images because they are the most commonly employed in Inhibitors,Modulators,Libraries corresponding meteorological studies. Inhibitors,Modulators,Libraries From the information provided above, one may conclude that as near-surface wind speed increases, Inhibitors,Modulators,Libraries so does SAR NRCS. However, there is a growing body of evidence that there is near-surface wind speed limit to this function, at which point the SAR NRCS becomes saturated . This saturation is a function of incidence angle and polarization with HH-pol saturation occurring at a larger wind speed than VV-pol. The SAR NRCS is also a function of near-surface wind direction.
Because the centimeter-scale surface waves driven Inhibitors,Modulators,Libraries by the near-surface wind generally travel with their crests oriented perpendicular to the near-surface wind direction, there are local maxima in NRCS when the radar look direction is opposite Inhibitors,Modulators,Libraries and along the near-surface wind direction.
Local minima in NRCS occur when the radar look direction is perpendicular to the near-surface wind direction. The relative magnitudes of the maxima are incident angle and near-surface wind speed dependent. Brefeldin_A As incident angle increases (say, from 20�� Inhibitors,Modulators,Libraries to 49��) and near-surface wind speed decreases (say, from 40 ms-1 to 10 ms-1), the NRCS becomes largest for a radar look direction opposite to the near-surface wind direction and there is a larger difference in NRCS between the maxima and minima. Figure 1 demonstrates these relationships from empirically-derived C-band geophysical MODel (CMOD) functions (GMF) 4  and 5 .
Both GMFs are tuned to wind speed at 10 m above sea level.
Within Figure 1, they have been modified from vertical-vertical (VV) polarization to horizontal-horizontal (HH) polarization (i.e., to that of RADARSAT-1). These GMFs will be discussed in more detail Dacomitinib sellectchem below.Figure 1.The relationship between NRCS, near-surface wind speed, and radar-relative near-surface wind direction for CMOD 4 and CMOD 5, continued on next page.Radar selleck chemicals incident angle, wavelength, and polarization also affect the relationship between the near-surface wind vector and NRCS while sky condition (cloudy/clear, day/night) does not. As incident angle increases, NRCS decreases (see Figure 1).