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R. Arnone et al.
Fig. 19.2 Panel (a): NCOM surface currents of 19 October 2009. Currents are interpolated to
the resolution of the imagery. Panel (b): initialization field of 19 October 2009 for backscattering
coefficient. Notice the removal of the clouds using the steps outlined in the text
19.2.1 Bio-optical Initialization Field: “Nowcast”
The initialization bio-optical field is a critical step in the forecast. A bio-optical
forecast requires complete spatial coverage in the initialization daily field. This
is needed for several reasons: (1) to prevent gaps or No Data (ND) from creating
artificial local boundary conditions in the advective forecast and (2) to prevent artificial bio-optical boundaries between ND and known data. The initialization field
is constructed daily using all known data and the previous forecast field to provide
a sensible bio-optical forecast. A realistic initialization field prevents abrupt data
recreation and boundaries from artistically propagating into the forecast.
As seen in Fig. 19.1, a major limitation of the ocean color imagery is that
complete coverage of bio-optical properties is not available daily. There are many
times when limited coverage results from either cloud cover, algorithms failure
(atmospheric, high turbidity, saturated radiance, etc.), no satellite coverage. These
limitations require a procedure to “fill in the gaps”. The initialization field is based
on a series of additive steps to establish the “most recent” bio-optical coverage used
to set the forecast.
The additive pixel procedure is used to determine the complete spatial distribution of coastal bio-optical properties. The hierarchy and details of the procedure
are discussed in detail in Casey and Arnone (2007). The “gap filler” procedure is
summarized in Steps 1–4:
1. today’s bio-optical properties (best and most accurate);
2. spatial convolution of bio optical data in step 1 out several pixels (fills small
holes, speckle, etc.);
3. triangular interpolation of data in Step 2 to fill in gaps;
4. yesterday’s 24 h bio-optical forecast.
R. Arnone et al.
Fig. 19.2 Panel (a): NCOM surface currents of 19 October 2009. Currents are interpolated to
the resolution of the imagery. Panel (b): initialization field of 19 October 2009 for backscattering
coefficient. Notice the removal of the clouds using the steps outlined in the text
19.2.1 Bio-optical Initialization Field: “Nowcast”
The initialization bio-optical field is a critical step in the forecast. A bio-optical
forecast requires complete spatial coverage in the initialization daily field. This
is needed for several reasons: (1) to prevent gaps or No Data (ND) from creating
artificial local boundary conditions in the advective forecast and (2) to prevent artificial bio-optical boundaries between ND and known data. The initialization field
is constructed daily using all known data and the previous forecast field to provide
a sensible bio-optical forecast. A realistic initialization field prevents abrupt data
recreation and boundaries from artistically propagating into the forecast.
As seen in Fig. 19.1, a major limitation of the ocean color imagery is that
complete coverage of bio-optical properties is not available daily. There are many
times when limited coverage results from either cloud cover, algorithms failure
(atmospheric, high turbidity, saturated radiance, etc.), no satellite coverage. These
limitations require a procedure to “fill in the gaps”. The initialization field is based
on a series of additive steps to establish the “most recent” bio-optical coverage used
to set the forecast.
The additive pixel procedure is used to determine the complete spatial distribution of coastal bio-optical properties. The hierarchy and details of the procedure
are discussed in detail in Casey and Arnone (2007). The “gap filler” procedure is
summarized in Steps 1–4:
1. today’s bio-optical properties (best and most accurate);
2. spatial convolution of bio optical data in step 1 out several pixels (fills small
holes, speckle, etc.);
3. triangular interpolation of data in Step 2 to fill in gaps;
4. yesterday’s 24 h bio-optical forecast.