QuikSCAT response to urban developments and seasonal cycles

We explore azimuthal variations in the 25-km resolution QuikSCAT L1B Ku-band satellite radar data in urban areas. The normalized microwave radar backscatter (σ0) increases from rural to urban regions suggesting that an anthropogenic influences from buildings and other infrastructure. A seasonal signal is also identified over all azimuthal angles in multiple global regions. Potential influencing factors of changes in the observed σ0 over land-use types from uninhabited to urban areas are explored including building and road orientation, precipitation, and vegetation. Buildings, roads, and curbs act as dihedral corner reflectors and enhance σ0 for azimuthal observation angles normal to the structure face. Azimuthal variations in the σ0 signal appear in urban areas with highly organized gridded street systems such as Beijing, China and Phoenix, Arizona; azimuthal variation is much less in cities with less organized streets such as Sao Paulo, Brazil. Changes in seasonal precipitation cannot be used to directly predict seasonal changes in σ0; however, changes in vegetation appear closely associated with a seasonal signal of σ0 in urban and rural areas.