VIIRS Global DNB Product Status

VIIRS Global DNB Product Status

Chris ElvidgeEarth Observation Group

NOAA National Geophysical Data Center

Kim Baugh, Feng-Chi Hsu, Mikhail ZhizhinCIRES, University of Colorado

October 22, 2012

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Enabling software developed at NGDC• Reprojection toolkit• DNB terrain correction• Stray light filter• M10 combustion source detection system• M15 cloud detection relative to NCEP surface

temperature grids• Modification of DMSP nighttime lights

compositing software

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Stray Light Filter Raw

Subtracted component

Filtered

The First VIIRS Global Cloud-Free CompositeApril 18-26, 2012 - Low moon nights

Output is a 15 arc second grid (86401 x 33601)

The First VIIRS Global Cloud-Free CompositeApril 18-26, 2012Washington, DC

VIIRS DMSP-OLS

The First VIIRS Global Cloud-Free CompositeApril 18-26, 2012Denver, Colorado

VIIRS DMSP-OLS

The First VIIRS Global Cloud-Free CompositeApril 18-26, 2012

Delhi, India

VIIRS DMSP-OLS

IssuesResidual Stray Light

Northward Extent 65 Degrees

1. Difficulty setting noise threshold due to residual stray light2. Current hardware lacks memory to geolocate aggregates north of 65 degrees3. Slight westward bias in DNB geolocation relative to M10 gas flare detections4. Low numbers of cloud-free coverages in numerous locations5. Fuzzy lights can be found in some areas

Geolocation Bias

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Basra Gas Flares, IraqRed = M10 compositeCyan = DNB compositeThe DNB geolocation is shifted slightly to the west.

Plan to Address Issues1. Stray Light: Make separate composites for stray light and

non-stray light data. Stray light is present for data observed with ground solar zenith angles in the range of 90 to 118 degrees. Develop separate noise thresholds, remove background noise, recombine.

2. Extending North: Move processing to computer with more memory. This is happening this week!

3. Geolocation Bias: Measure the bias between DNB and M10 combustion source detections in the global cloud-free composites. Introduce bias correction as a variable in the reprojection toolkit. Reprocess!

4. Expanding the number of cloud-free coverages: Add data from additional months.

5. Fuzzy lights: Develop fuzzy light detector. Screen out fuzzy lights in the compositing process.

Composite with no stray light contaminated data

Composite with stray light contaminated data

Composite with stray light filtered data

Effect of Stray Light Filtering

Use of April cloud-free composite as a reference for the detection of power outages on November 1,

2012