CERES Uniform Footprint Sampling

To ensure regional uniform footprint sampling consistent with view angle when the CERES instrument is in cross-track mode, SRBAVG employs a threshold based on the following equation.

Number_Footprints/cos(latitude) > (a₁* cos²(view angle) + a₀)*0.5

A region must have 50% coverage of the cross-track footprints to be used. From the scatter plot below very few region are rejected. All coefficients are based on 1° degree equal angle regions. For Terra a₁ is 69.0 and a₀ is -8.2 and for Aqua a₁ is 68.7 and a₀ is -8.2. The coefficients were obtained by linear regression.

Scatter plot of Terra footprints/cosine of latitude and cosine of the view angle squared for Dec. 2, 2003