As clouds are starting to dissipate with the slow demise of Sandy, we are getting some beneficial peeks through the clouds with the VIIRS Day-Night Band (DNB). As we demonstrated with Isaac in the New Orleans area, the DNB is great for inferring quite a bit about power outages and even cloud cover through interactions of emitted light versus reflected moonlight. We have assembled two examples of the DNB imagery over the northeastern United States. The first image is from the morning of October 26. Although some low clouds were present across several states, they were not thick enough to completely mask the cities below, resulting in a vibrant display of light (though diffuse) throughout the major cities extending from Washington D.C./Baltimore through Boston.
This morning, November 1, we obtained some additional city light views (and some cloud cover remnants from Post-Tropical Cyclone Sandy) across the area. As you toggle between the first two slides, your eyes will pick up some loss of city lights along the coastal areas of New Jersey, Long Island, and portions of southern Maine. News reports confirm power outages in many of these areas. Unfortunately, some of the lingering cloud cover makes it a bit difficult to make strong claims about power outages in more areas, as some of the missing city lights may be cloud-obscured. However, these coastal areas appear to be cloud free given that the city lights that *are* present are appearing as fine, small points of bright light that are not being diffused or scattered by clouds at higher altitude. We can highlight areas where we feel pretty confident that the changes are due to power loss, not cloud cover, but it can be tricky given that even thin clouds can obscure the lights below – similar to viewing cities from above in an airplane. There may be other areas where city lights are out but not fully viewable in the difference image – for example, portions of eastern Massachusetts would likely have had similar impacts, but this morning’s cloud cover makes it difficult to determine. In these images, the clouds that are present are visible from reflected moonlight given that we are still at or near to the full moon phase.
As skies continue to clear, there may also be other means of watching the recovery by looking for city lights that reappear. This is just another great example of VIIRS applications in response to disasters. SPoRT provides this type of imagery via our website and to NWS partnering offices and National Centers that we collaborate with through NOAA’s Joint Polar Satellite System (JPSS) Proving Ground. The final imagery here are derived from data obtained from the Cooperative Institute for Meteorological Satellite Studies (CIMSS) at the University of Wisconsin Madison and are processed using a lunar reflectance algorithm provided to us by colleagues at the Cooperative Institute for Research in the Atmosphere (CIRA) at Colorado State University in Ft. Collins, Colorado.