1-km resolution MODIS fog product + 4-km resolution GOES-13 fog product

The early morning area forecast discussion issued by the National Weather service office at State College, Pennsylvania mentioned that river valley fog was being detected by the MODIS fog/stratus product:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
526 AM EDT FRI SEP 16 2011

.SYNOPSIS...
A LARGE HIGH PRESSURE SYSTEM OVER THE GREAT LAKES WILL BUILD SLOWLY EAST TO NEW ENGLAND BY SUNDAY AND MONDAY. A DYING COLD FRONT WILL LIKELY PUSH INTO THE REGION LATE MONDAY OR TUESDAY. A DIGGING TROF AND ASSOCIATED SLOW MOVING COLD FRONT COULD AFFECT THE REGION BY LATE NEXT WEEK.

.NEAR TERM /UNTIL 6 PM THIS EVENING/... EARLY AM MODIS 11-3.7UM IMAGERY SHOWING DENDRITIC PATTERN OF FOG IN THE DEEP RIVER VALLEYS OF THE ALLEGHENY MTNS.

A comparison of AWIPS images of the 1-km resolution MODIS fog/stratus product with the corresponding 4-km resolution GOES-13 fog/stratus product (above) demonstrated the advantage of higher spatial resolution for detecting such small-scale features. A subtle fog signal was beginning to show up at this time in the GOES-13 fog/stratus product image, but it was difficult to tell whether it was due to noise or actual fog features.

About an hour and 15 minutes later, a similar comparison using a 1-km resolution POES AVHRR fog/stratus image and the corresponding 4-km resolution GOES-13 fog/stratus product image (below) showed that while the fog signal had become better defined by this time on the GOES-13 image, the POES AVHRR image again showed the river valley fog features with much greater clarity.

1-km resolution POES AVHRR fog product + 4-km resolution GOES-13 fog product

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GOES-13 10.7 µm IR images

Maria intensified on 15 September 2011 to become the third hurricane of the 2011 season in the Atlantic Basin — convective bursts during this time period were seen on 4-km resolution GOES-13 10.7 µm IR images from the CIMSS Tropical Cyclones site (above).

AWIPS images of 1-km resolution MODIS 0.65 µm visible channel and 11.0 µm IR channel data (below) displayed cloud top IR brightness temperatures as cold as -84º C (darker purple color enhancement) associated with a couple of the convective bursts, and a curved convective band wrapping around the northern portion of what appeared to be the eye of Maria.

MODIS 0.65 µm visible channel and 11.0 µm IR channel images

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GOES-11 6.7 µm (left) and GOES-15 6.5 µm (right) water vapor channel images (click image to play animation)

McIDAS images of 8-km resolution GOES-11 6.7 µm and 4-km resolution GOES-15 6.5 µm water vapor channel data (above) demonstrated the advantage of improved spatial resolution for the detection of features and gradients in the water vapor imagery associated with a weak upper level low moving eastward across the southwestern US on 14 September 2010. GOES-15 is scheduled to replace GOES-11 as the operational GOES-West satellite in December 2011.

AWIPS images of the GOES-11 sounder Convective Available Potential Energy (CAPE) product (below) showed that the atmosphere was destabilizing in advance of the upper low, with CAPE values in the 1000-2000 J/kg range.

GOES-11 sounder Convective Available Potential Entegy (CAPE)

With the increasing instability and large scale lift ahead of the upper low, areas of thunderstorms developed over parts of Nevada, Arizona, and Utah, as seen on a MODIS 11.0 µm IR image with an overlay of cloud-to-ground lightning strikes (below). About an hour after the time of the MODIS image, one of these storms produced 1.0-inch diameter hail that covered the ground near Munds in northern Arizona (SPC storm reports).

MODIS 11.0 µm IR image + cloud-to-ground lightning strikes

CIMSS participation in GOES-R Proving Ground activities includes making a variety of MODIS and additional GOES Sounder images and products available for National Weather Service offices to add to their local AWIPS workstations. Currently there are 49 NWS offices receiving MODIS imagery and products from CIMSS.

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GOES Water Vapor Imagery and turbulence reports

Clear Air Turbulence can be a significant aircraft hazard, occasionally causing injuries and long delays. (See, for example, here and here for two recent examples. The second example resulted in a 6-hour delay (Link))

At the upper-tropospheric boundary between air masses, vertical shearing at the jet stream combined with the ageostrophic convergence of polar, subtropical and stratospheric air produces a region known for its potential for clear air turbulence called a “tropopause fold.” These features are evident in satellite-observed upper tropospheric water vapor by the large-scale spatial gradients in brightness temperature, which define boundaries between the air masses. The tropopause fold extends from this boundary to a limited distance into and underneath the wetter air mass.

Thus, water vapor imagery can be used to infer large changes in vertical motion that can herald the presence of turbulence in the atmosphere. For example, in the region of turbulence shown in the water vapor imagery above, the yellow enhancement — warm brightness temperatures — suggest water vapor concentrated lower in the atmosphere (subsidence); bluer enhancements — colder brightness temperatures — suggest water vapor that is concentrated higher in the atmosphere (rising motion).

The Tropopause Folding Turbulence Prediction (TFTP) product locates these regions in the atmosphere and identifies the sections most likely to produce turbulent flight conditions for aircraft. The upper-tropospheric water vapor channel of the GOES-R Advanced Baseline Imager (primary: channel 8, backup: channel 9) is the source for resolving gradients that reveal the horizontal distribution of tropopause folds. An ancillary numerical weather model constrains these features vertically in the atmosphere. The four key output products consist of two fields that define the lower and upper bounds of the turbulent volumes of air, and two fields that define the two flight directions that are the most susceptible to moderate or greater turbulence. For now, the GOES-East (or MODIS) water channels can be used as a proxy.

GOES Water Vapor Imagery and turbulence reports

The animated gif above shows the predicted tropopause fold (green), model results that show the tropopause (yellow, the 1-2 PV Unit surface) for a turbulence event that occurred in September 2011 (link). Note that the strongest turbulence (red airplane icon) occurred as the plane traversed the fold.

GOES-13 6.5 µm water vapor channel images (click image to play rocking animation)

The animation of water vapor imagery (above) centered on the time of the turbulence includes some key features. For example, the gradient in the water vapor field between the colder brightness temperatures over the Atlantic Ocean south of New England and the warmer brightness temperatures off the coast of New Jersey is tightening with time. There is also evidence of a jet feature propagating northeastward along the gradient from east of the mouth of Chesapeake Bay at the start of the loop to south of Long Island at the end of the loop. Both of these features are suggestive of an evolving tropopause fold.

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