Tropical Storm Noel

October 28th, 2007

GOS-12 visible image + ASCAT winds

Tropical Storm Noel formed in the Caribbean Sea on 28 October 2007. A GOES-12 visible image with ASCAT winds sourced from the CIMSS Tropical Cyclones site (above) shows the cloudiness associated with the tropical storm, which was centered just south of Hispaniola. An animation of GOES-12 IR channel images (below) shows that a few bursts of convection developed in the northern quadrant of Noel during the day (also apparent in a 1-km resolution GOES-12 visible image animation).

GOES-12 IR images + ASCAT winds (Animated GIF)

Grand Canyon, Arizona: smoke from local and distant sources

October 26th, 2007

MODIS true color image

An end to the offshore Santa Ana wind regime and a change in the synoptic-scale flow pattern over the southwestern US (MODIS visible image + RUC model winds at 1 km and 2km AGL) resulted in a northward to northeastward transport of smoke from the ongoing Southern California fires on 26 October 2007. A 250-meter resolution MODIS true color image centered over the Grand Canyon in Arizona (above) shows a distinct smoke plume from a new fire that was burning along the north rim of the canyon, as well as a large amount of smoke covering the western portion of the Grand Canyon (which had been transported from the California fires).

A larger-scale MODIS true color image of the Southwest US (below) shows that the smoke from the southern California fires had spread as far as the San Joaquin Valley of California (even settling into some of the valleys along the western foothills of the Sierra Nevada Mountain Range), southern Nevada, northwestern Arizona, and extreme southwestern Utah. The IDEA MODIS Aerosol Optical Depth trajectory product from the previous day provided a fairly accurate forecast of smoke transport.

MODIS true color image

4-day composite of the southern California fires

October 24th, 2007

Wildfire ABBA 4-day composite (21-24 October 2007)

The Wildfire Automated Biomass Burning Algorithm (WFABBA) team produced a 4-day composite of the southern California fires, covering the period 21-24 October 2007. By 26 October, nearly 500,000 acres (~780 square miles) were burned and over 1600 homes were destroyed.  The WFABBA product provides frequent, low latency detections and characterizations of fires such as these, as well as the ability to build composites to show the overall development of the fires. Southern California fire activity can be monitored using WFABBA  from either GOES-11 or GOES-12.

California fires: a “smoke signal” in the water vapor imagery?

October 23rd, 2007

AWIPS GOES 4-panel (Animated GIF)

The large wildfires continued to burn across parts of southern California on 23 October 2007. AWIPS images of the GOES-11 imager visible channel (upper left panel), 6.7 µm water vapor channel (upper right panel), 10.7 µm IR channel (lower left panel), and the GOES-11 Sounder 4.0 µm IR channel (lower right panel) reveal an interesting signature of the smoke pall that had been transported westward out over the Pacific Ocean — on the water vapor channel! Since H2O is a byproduct of combustion, the water vapor content of the aged smoke pall is somewhat elevated compared to the rather dry ambient atmosphere over the eastern Pacific Ocean; this allows a subtle signature of the smoke feature to appear on the GOES imager water vapor channel. There is no signal on either of the IR channel images (bottom 2 panels) since smoke is transparent to thermal radiation at those wavelengths.

MODIS RGB images (Animated GIF)

A comparison of two 500-meter resolution Terra MODIS red/green/blue (RGB) image composites (above) shows a closer view at the fires in the Los Angeles and San Diego region. The MODIS Channel 01/04/03 RGB image approximates the “true color” images that appear on the SSEC MODIS Direct Broadcast site. The MODIS Channel 07/02/01 RGB image takes advantage of the temperature sensitivity of the “near-IR” Channel 07 (2.1 µm) to make the hottest active fires appear with a pink to red enhancement (the red pixels over water are due to sun glint). The large dark burn scar resulting from the 70,000-acre fire just southwest of San Diego (station identifier KSAN) is just starting to become evident on the 07/02/01 RGB image, even through the thick smoke plume seen on the 04/03/01 RGB image.

IDEA trajectory forecast

The IDEA MODIS aerosol optical depth (AOD) trajectory forecast (above) suggested that some of the thick smoke could get recirculated back over portions of northern California within the 48-hour forecast period; however, the trajectory trend indicated that these aerosols might remain just above the boundary layer, which would limit their impact on surface air quality in the San Francisco region. The National Weather Service also provides a 1-hour average vertical smoke integration product as part of their Air Quality Forecast Guidance.