Day/Night Band Case Study

Louisiana Moon Glint—Preliminary Review12 January 2014

Steve MillerCSU/CIRA

Moon Glint Angle

Ocean Surface

θ < ~30˚

θ

Glint Angle

θ < ~10˚

When the Moon-Satellite geometry is favorable, there is the possibility for brightening of the water surface from lunar reflectance, just as in the day.

12 Jan 2014 0741 UTC 12 Jan 2014 0842 UTC

Poss

ible

Spe

cula

r Zon

e

Luna

r Glin

t Ang

le (D

egre

es)

Day/

Nig

ht B

and

Radi

ance

(Sca

led)

Moon Glint Zone (θ < ~30˚) Outside GlintZone (θ >> 30˚)

Specular Lunar Reflectance(Smooth Waters)

Same LocationOutside of GlintZone 1 hr Later

Specular Characteristics

Calm waters mirror reflectance of Lunar Disk. (inside of the θ < ~10˚ cone)

Wind-roughened diffuse reflectance of Moonlight

Calm waters mirror reflectance without Lunar Disk (outside of the θ < ~10˚ cone).

Cloud Shadow

SSMI+AMSR-E Derived Surface Winds

Courtesy NRL Monterey’s NEXSAT Webpage

Zoom Area

Zoom Area

0 5 10 15 20 25 30 35 40 45

PMW data questionable due to proximity to coast. Moonglint suggests that water surface was smooth…possibly due heavy coastal turbidity or meteorological effect (e.g., ducting of surface winds atop low-level inversion layer)?

SSM/I + AMSR-E 12 Jan 2014 0000 UTC VIIRS Day/Night Band 12 Jan 2014 0741 UTC

Notes and Preliminary Conclusions• The DNB imagery brightening near the Louisiana coast (and

accompanying darkness further to the west, and diffuse brightness in the GOMEX) is all consistent with the expected behavior of moonglint.

• Glint angle geometry consistent with features observed.• Demarcation of specular/diffuse zones suggests a sharp shift from

calm to roughened waters offshore.• Additional analysis of true color imagery may reveal heavy turbidity

near coast (one possible means to achieving calm waters even in the presence of light surface wind)

• Analysis of other meteorological fields would be useful for understanding any mesoscale features such as low level inversions and ducting/decoupling of surface winds.

• Further interpretation of SSM/I and AMSR-E derived wind fields pending with NRL Monterey experts.