Archive for May, 2008

Vegetation across Southern California

Wednesday, May 21st, 2008

MODIS true color images (Animated GIF)

A comparison of Aqua MODIS true color images from 05 March 2008 and 17 May 2008 (above) showed the “browning” of vegetation across Southern California after the Spring season rains (90-day total rainfall | 90-day percent of normal rainfall) had ended. A significant amount of snowmelt was also evident during that period over the southern Sierra Nevada mountains (as well as over the higher elevations of smaller ranges such as the San Gabriel, San Bernardino, and San Jacinto Mountains). The images (courtesy of Liam Gumley, CIMSS) were created in Google Earth using publicly available data from the SSEC MODIS Today website.

Even though the MODIS true color images above suggested an overall dry-down of the vegetation across the region, a comparison of AWIPS images of the MODIS Normalized Difference Vegetation Index (NDVI) and visible channel (below) indicated that many areas of southern California still exhibited a NDVI value as high as 0.5-0.6 on 20 May 2008. A National Public Radio story pointed out that the rapid growth of non-native plant species across parts of southern California could actually be a warning sign of an increased potential for future wildfire activity (once that vegetation continued to dry out over the upcoming Summer and Fall months).

MODIS NDVI + visible image (Animated GIF)

Occluding cyclone over the North Atlantic Ocean

Tuesday, May 20th, 2008

Northern hemisphere water vapor composite imagery (Animated GIF)

AWIPS images of the water vapor  satellite composite (above) showed the evolution of a wide variety of synoptic-scale features across the Northern Hemisphere at 3-hour intervals during the 19 May – 20 May 2008 period. Of particular interest was the water vapor signatures associated with an occluding cyclone over the North Atlantic Ocean (located south of Iceland and west of the British Isles). A closer view using Meteosat-9 images of the 6.2 µm water vapor channel at 15-minute intervals (below) revealed a great deal of interesting mesoscale structure as bands of moist and dry air wrapped into the occluding cyclone as it began to fill .

Meteosat-9 water vapor images (Animated GIF)