Thin-over-Thick Cloud overlap detection (Pavolonis and Heidinger, JAM 2004) can be applied to lunar reflection and split-window observations. The premise to the technique is that a thin cirrus cloud atop a warmer background (land/water –or- low cloud) will produce a large 11-12 micron brightness temperature difference due to the ice particle absorption properties. If a low cloud is present, then its high reflectance will be seen through the cirrus cloud. Since the 11-12 signal is only present for very thin clouds having characteristically *low* visible reflectance, the simultaneous presence a very *high* visible reflectance can only be explained by a sub-cirrus reflector—i.e., overlap. Not aware of any way to do something similar with IR channels alone…such that this technique *requires* visible channel data. The DNB will provide this information at night. We will attempt to demonstrate this capability based on OLS space/time match-ups with geostationary sensors.
We can imagine a scenario where a storm system passes over a data-sparse/denied area of interest during the day, possibly depositing snow. The system leaves the are in the evening hours--how will we know whether the region has snow cover? One way is to use microwave data, but the spatial resolution may be too coarse for the current need. The DNB will provide a 740 m resolution detailed depiction of any snow cover present in the scene. We use conventional IR-based cloud detection techniques and static city light masks to remove these features, and the residual ‘bright’ areas will correspond to the snow cover.
Will come back to the cloud/dust ambiguity later. In the example above, a massive dust storm over Africa is depicted by MODIS (left panel) as yellow, with the approximate location of the dust front indicated in green. The following night, the nighttime DMSP-OLS crossed this same region. An algorithm designed to enhance high reflecting targets within a specified temperature range was developed to enhance the lunar reflection off this dust storm—revealing the movement of the front over the 9 hour period (compare current front denoted by red line with 1110 GMT position denoted by green line). The movement is estimated at roughly 20 km/hr. In the NPOESS era, additional channels on VIIRS (e.g., 3.9 micron, 8.5 micron, 11/12 micron split window channels) will be combined with the DNB to improve the delineation of dust features at night
The Station Fire, north of LA, burned over 160 thousand acres (250 sq miles) and killed two firefighters.
Hugh Christian, Jr., NASA/MSFC Huntsville, AL: Lightning emission peak at 774 nm (can be used to detect daytime lightning above the background)….think this is in the Oxygen A-Band…?
1/25 1836 1/26 1737 1/26 1804 1/27 1725 1/28 1841
Enhancement after applying a very rudimentary enhancement based on mean scan-line subtraction and spatial coherence filter.
WE4.L10.5: ADVANCES IN NIGHTTIME SATELLITE REMOTE SENSING CAPABILITIES VIA THE NPOESS/VIIRS DAY/NIGHT BAND LOW-LIGHT VISIBLE SENSOR AND TRACING EVOLUTION OF THESE CAPABILITIES OVER LIFETIME OF IGARSS
Advances in Nighttime Satellite Remote Sensing Capabilities via the VIIRS Day/Night Band Low-Light Visible Sensor (and Tracing Evolution of these Capabilities Over the Lifetime of IGARSS) Steve Miller 1 , Tom Lee 2 , Bob Turner 3 , Jeremy Solbrig 2 , Rich Bankert 2 , Cindy Combs 1 , Stan Kidder 1 , and Chris Elvidge 4 1 Cooperative Institute for Research in the Atmosphere Colorado State University, Fort Collins, CO 2 Satellite Meteorological Applications Section Naval Research Laboratory, Monterey CA 3 Science Applications International Corporation (SAIC), Monterey, CA 4 National Oceanic and Atmospheric Administration (NOAA) National Geophysical Data Center, (NGDC), Boulder, CO IGARSS 2010, Hawaii IGARSS at 30: Perspectives on Remote Sensing Science and Sensors WE4.L10.5 Paper 5248 28 July 2010
Motivation <ul><li>Satellite detection/characterization of low cloud cover, aerosols, snow cover, and other environmental parameters via optical-spectrum radiometers is limited in most cases to daytime observations, when sunlight is available. </li></ul> The many new capabilities that the DNB will enable is one of the most novel and perhaps most important elements of VIIRS <ul><li>Awareness of these parameters and their properties at night is critical to a wide array operational users, and in particular to the general aviation community. </li></ul><ul><li>The “Day/Night Band” (DNB) sensor, capable of detecting extremely low levels of visible light will be flown for the first time on a civilian operational satellite (the Joint Polar Satellite System; JPSS) as part of the Visible/Infrared Imager/Radiometer Suite (VIIRS). </li></ul>
How Have Low-Light Applications Evolved? <ul><li>Progress limited by technology which has been the same since the early years of the environmental satellite era… </li></ul><ul><li>2-band VIS (0.4-1.1 m), IR (10-13.4 m) </li></ul><ul><li>8-bit digitization </li></ul><ul><li>Coarse spatial resolution (~ 3 km) </li></ul><ul><li>No practical calibration </li></ul>1960’s 1970’s 1980’s 1990’s 2000’s Today The Operational Linescan System (OLS) on the Defense Meteorological Satellite Program (DMSP) series. Natural gas flares (Croft 1973) Aurora (Snyder et al, 1973) City lights (Akasofu et al., 1975) Fishing fleets and urban settlements (Croft 1978) Lightning (Orville 1981) Snow cover (Foster, 1983) Fires (Cahoon et al., 1993) Calibration, Energy Consumption, (Elvidge et al. 1997, 1998,1999) Bioluminescence (Miller et al., 2005) Aerosol Retrievals (Zhang et al, 2008) Designed for cloud imagery across day/twilight/night. Declassified in 1972. OLS
The VIIRS Day/Night Band ** <ul><li>Panchromatic visible-band imaging radiometer to fly on JPSS as part of the VIIRS channel suite </li></ul><ul><li>740m resolution (nearly constant along swath), via variable aggregation of CCD elements both along track and scan </li></ul><ul><li>12-14 bit radiometric resolution, 3 stages of dynamically selected gain to handle scene brightness across 7 orders of magnitude </li></ul><ul><li>On-orbit calibration via transfer from HGS to MGS and LGS </li></ul><ul><li>Minimal stray light (solar glare) effects </li></ul><ul><li>First opportunity to blend low-light sensor measurements with numerous NIR/IR bands for multi-spectral applications </li></ul>** Lee, T. F., S. D. Miller, F. J. Turk, C. Schueler, R. Julian, S. Deyo, P. Dills, and S. Wang, 2006: The NPOESS/VIIRS day/night visible sensor , Bull. Amer. Meteor. Soc ., 87 (2), 191-199. Presented here are examples of VIIRS/DNB multi-spectral capabilities, demonstrated in a limited way via the DNB’s heritage sensor—the DMSP Operational Linescan System
1) Lunar Reflection Methods ‘ Harvesting the Moon’ for Day-Like Capabilities… Miller, S. D., and R. E. Turner, 2009. IEEE Trans. Geosci. Rem. Sens ., 47 (7), 2316-2329. (A code for quantifying lunar irradiance)
Cloud Overlap Detection at Night Limited information on cloud layering is available from multi-spectral VIS/IR measurements: thin cirrus atop thick lower-level clouds The VIIRS DNB will offer the only capability for detecting such two-layer cloud structures at night. Low Clouds Thin Cirrus Thick Stratus
Low Clouds & Ship Tracks Day/Night Band’s sensitivity to reflected moonlight will improve the detection of ship tracks and other low-cloud features at night… DAY NIGHT GOES VIS loop Courtesy CIMSS
Low Clouds/Fog Over Cold Terrain Detection enabled where conventional IR techniques often fail due to extremely cold surfaces…
Snow Cover Detection at Night Multi-spectral techniques that include a nighttime visible band can separate cloud from snow cover and sea-ice. We can simulate the capability of VIIRS via space/time matching of OLS and sensors possessing NIR channels… Snow Cover
Concept New Moon City Lights Snow Low Clouds High Clouds Nighttime Visible Band Only (DMSP/OLS) Add Stable Night Lights Mask Add High / Low Cloud Detection (GOES) Combine LEO and time-matched GEO to provide augmented channel suite for improved discrimination.
A “Poor-Man’s” VIIRS Simulation CO NE KS NM WY UT SD OK MT Low Cloud High Cloud City Lights Snow Cover
Quasi-Looping Capability Potential for further blending with geostationary data for analysis of radiation fog development. Low Cloud High Cloud City Lights Snow Cover
Dust Detection at Night Nighttime: IR Only Daytime: MODIS VIS + IR 3 March 2004, 1110 GMT 3 March 2004, 2017 GMT Moonlight reflectance highlights dust plumes at night. A mid-morning (0930/2130) orbit would be particularly valuable for tracking the advance of plumes after sunset. Nighttime: OLS VIS + IR
DMSP/OLS 8/30/2004 0504 UTC 11.0 µ m IR Window Georgette Eastern Pacific 15 N 20 N 125 W 120 W Tropical Cyclone Fixes at Night <ul><li>Exposed low-level circulation occurs when storms enter a high vertical shear environment </li></ul><ul><li>Decoupling of the upper and lower level cloud fields </li></ul><ul><li>Displacements between upper and lower level centers can exceed 100 km in some cases </li></ul>Helps avoid the “Sunrise Surprise” Upper-Level Circulation Lower-Level Circulation ~200km SE
2) Terrestrial Emission Methods The Night is Not as Dark as You Might Think…
Artificial Light Sources Yellow =No Change Red =Lights Out Green =New Lights Courtesy C. Elvidge, NOAA/NGDC New Orleans The higher resolution (0.74 km) nighttime lights background from VIIRS/DNB will enable superior ‘residual light’ applications. DMSP/OLS 8/28/2005 0220 UTC DMSP/OLS 8/30/2005 0154 UTC ?
Wildfire Smoke Plumes Fire Smoke Plume Illuminated By Moonlight JPL
Actively Burning Fires Ensenada 10/22/2007 2055 UTC (Aqua) 10/22/2007 0423 UTC (F-16) 10/23/2007 0620 UTC (Terra) 10/23/2007 0201 UTC (F-16) Active fires produce significantly greater smoke flux, potentially impacting nighttime visibility (T&D). Ferguson and Hardy, Int. J. Wildland Fire, 1994 Active Smoldering
Lightning Flashes Correlation of dense flash zones with embedded convective rainfall region (vs. trailing stratiform).
Space Weather: Auroras Aleutian Chain NORTH PACIFIC Auroral boundaries are a VIIRS EDR
Bioluminescence: ‘ Milky Seas ’ Miller et al., 2005 (Proc. Nat Acad. Sci.)
Conclusions <ul><li>The Day/Night Band will offer new and unique nighttime observing capabilities to the operational community. No longer at the mercy of IR-only applications at night. </li></ul><ul><li>The first VIIRS is slated to fly on the NPOESS (now JPSS) Preparatory Project. </li></ul><ul><li>Beyond “near constant contrast” imagery, the DNB currently does not factor into the VIIRS Environmental Data Records (EDRs). </li></ul> A golden opportunity exists for the R&D community to augment the performance of the VIIRS EDRs through incorporation of calibrated, high spatial resolution nighttime visible data.
Lunar Phase Variability The moon is not a self-illuminating body, and its brightness varies significantly (and non-linearly) across the lunar cycle.
A Lunar Irradiance Model for the DNB Reflectance = F( physical properties ) = I up / ( E M ) I up = isotropic upwelling irradiance (measured by sensor) E M = cosine-weighted lunar irradiance (the model) <ul><li>Computes the down-welling, top-of-atmosphere lunar spectral irradiance (W/m 2 - m) between 0.2 and 2.8 m at 1 nm resolution. </li></ul><ul><li>A ‘standard geometry’ (1 AU, mean Earth-Moon distance) version rendered at 1-degree lunar phase resolution. </li></ul><ul><li>Sun/Earth/Moon geometry tables provided at 1-hr resolution, used for adjusting standard geometry to current geometry. </li></ul><ul><li>Irradiance spectra computed for a given date/time, convolved with the spectra with VIIRS/DNB sensor response function. </li></ul>I(1) I(2) E(1) < E(2) (1) > (2) I(1) = I(2) (1) (2) E M Radiance Measurement Ambiguity E(1) E(2)
Example Results Model predicts down-welling top-of-atmosphere lunar irradiance for any date/time over the years 2000-2100 Miller, S. D., and R. E. Turner, 2009. IEEE Trans. Geosci. Rem. Sens ., 47 (7), 2316-2329. (Code included in supplemental materials)