Hydrological impacts of Hurricane Irene

August 29th, 2011 |
MODIS true color images: 16 August and 28 August 2011

MODIS true color images: 16 August and 28 August 2011

Heavy rainfall associated with Hurricane Irene included 20.40 inches at Virginia beach, Virginia and 20.00 inches at Jacksonville, North Carolina (HPC summary). Winds gusted as high as 115 mph at Cedar Island, North Carolina. The effects of the heavy rain and strong winds can be seen in a before/after comparison of 250-meter resolution MODIS true color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above). On the “before” image (16 August 2011), there was a large smoke plume seen from a fire that was burning in the Great Dismal Swamp area in far southeastern Virginia; on the “after” image (28 August 2011), water turbidity was significantly enhanced due to suspended sediment across the Outer Banks region of North Carolina — and a narrow filament of sediment was being actually being entrained into the flow of the Gulf Stream.

AWIPS images of the corresponding MODIS 0.65 µm visible channel data and the MODIS Sea Surface Temperature (SST) product (below) showed that the enhanced turbidity features seen on the MODIS true color image generally exhibited slightly cooler SST values (in the middle to upper 70s F, blue color enhancement) compares to the waters located closer to the Gulf Stream (SST values in the lower 80s F, darker red color enhancement).

MODIS 0.65 µm visible channel image + MODIS Sea Surface Temperature image

MODIS 0.65 µm visible channel image + MODIS Sea Surface Temperature image

Farther to the north, another before/after MODIS true color image comparison revealed additional areas of sediment being carried off the coast of the Northeast US (below). Also note that there was a great deal of sediment in the Hudson River (perhaps better seen in this 20 August / 29 August comparison).

MODIS true color images: 26 August and 29 August 2011

MODIS true color images: 26 August and 29 August 2011

Flooding continues along the Mississippi River

May 17th, 2011 |
MODIS 0.65 µm visible channel image + MODIS 2.1 µm near-IR "snow/ice channel" image

MODIS 0.65 µm visible channel image + MODIS 2.1 µm near-IR "snow/ice channel" image

AWIPS images of MODIS 0.65 µm visible channel data and MODIS 2.1 µm near-IR “snow/ice channel” data (above) demonstrated the utility of the snow/ice channel imagery for highlighting the areal extent of flooding along parts of the lower Mississippi River on 17 May 2011. Water is a strong absorber at the 2.1 µm wavelength, so it appears very dark on the MODIS snow/ice channel image.

CIMSS participation in GOES-R Proving Ground activities includes making MODIS imagery available for National Weather Service forecasters to add to their AWIPS workstations. The VISIT training lesson “MODIS Products in AWIPS” is also available to help users understand the products and their applications to weather analysis and forecasting.

A closer view using 250-meter resolution MODIS true color (using channels 1/4/3) and false color (using channels 7/2/1) MODIS Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) revealed the darker brown “muddy” appearance of much of the flooded areas adjacent to the Mississippi River, due to high sediment loading of the water. Water exhibited a very dark blue appearance on the MODIS false color image.

250-m resolution MODIS true color and false color Red/Green/Blue (RGB) images

250-m resolution MODIS true color and false color Red/Green/Blue (RGB) images

Flooding at the confluence of the Mississippi and Ohio Rivers

May 4th, 2011 |
MODIS 0.65 µm visible channel image + MODIS 2.1 µm near-IR "snow/ice channel" image

MODIS 0.65 µm visible channel image + MODIS 2.1 µm near-IR "snow/ice channel" image

 

A comparison of AWIPS images of the 1-km resolution MODIS 0.65 µm visible channel (first shown with a map overlay and location of METAR sites) and the corresponding 1-km resolution MODIS 2.1 µm near-IR “snow/ice channel” (above) shows the areal coverage of flood waters across the region of the confluence of the Mississippi River and the Ohio River on 04 May 2011. Since water happens to be a strong absorber at the 2.1 µm wavelength, it shows up as a very dark feature on the MODIS “snow/ice channel” image — making it more useful for locating areas of flooding than just a simple visible channel image.

A similar near-IR channel will be on the ABI instrument of the future GOES-R satellite. CIMSS participation in GOES-R Proving Ground activities includes making a variety of MODIS images and products available for National Weather Service offices to add to their local AWIPS workstations.

MODIS True-color imagery from the SSEC MODIS Today website can be used to compare data from this year and last year, shown below. In the linked-to-images, the Mississippi River north of Memphis (located at the bottom edge of each image) meanders through the center part of the images. There are several former meanders of the river in Arkansas and Tennessee that are filled with water this year, but not last.

 

MODIS true color images (04 May 2010 and 04 May 2011)

MODIS true color images (04 May 2010 and 04 May 2011)

 

Flooding continues along the Red River of the North

April 24th, 2011 |
MODIS false color image comparison between 11 April and 24 April 2011

MODIS false color image comparison between 11 April and 24 April 2011

 

A comparison of MODIS false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) shows the increase in areal coverage of flooding along the Red River of the North, from north of Grand Forks, North Dakota into southern Manitoba. Also evident is the melting of most of the snow cover across northeastern North Dakota, and the melting of portions of Devils Lake (snow and ice appear as cyan features on the false color images, while water has a darker blue appearance).