Running a forecast model with locally downloaded satellite data

August 27th, 2008 |
McIDAS-V images of CRAS model Precipitable Water

McIDAS-V images of CRAS model Precipitable Water pre-forecast spin-up

MODIS instruments (see here, as well) on board NASA’s Terra and Aqua satellites offer high resolution multi-banded views of the Earth’s atmosphere. Information from the channels can be used to derive total precipitable water in regions where clouds do not exist (as explained here). In the present case, MODIS TPW is compared to colocated TPW values in a CRAS model run that is centered on the direct broadcast MODIS ground station site at SSEC. Where the values differ, mixing ratios are adjusted so that the model value more closely matches the satellite-observed TPWs (Lapse rates are preserved in the adjustment). Satellite-observed TPWs are available only in clear fields of view; cloud initializations, however, are adding information where clouds are observed.

The case above (imagery produced using McIDAS-V) shows the 12-hour pre-forecast spin-up for the model with an initial time of 12:00 UTC on 25 August 2008. Six different MODIS orbits that were received at the SSEC direct broadcast ground station between 00:00 UTC and 12:00 UTC directly affect the initial model fields that are derived from GFS output. Note how the addition of MODIS data moistens the atmosphere in and around the remains of Tropical Storm Fay over the south central US, and also moistens the atmosphere over the Pacific Ocean west of California.

This method is used to introduce satellite information downloaded locally into a model run; more accurate initial fields are helpful in producing a more accurate forecast. In the present case, once the more accurate initial fields are generated, the model then steps forward in time (with GFS fields used to constrain the boundaries).

GOES-13 imagery: dissipating river valley fog, and mountain waves

August 27th, 2008 |

GOES-12 and GOES-13 visible images (Animated GIF)

A comparison of GOES-12 and GOES-13 visible images centered near Rolla (station identifier KVIH) in southern Missouri (above) showed that widespread river valley fog was dissipating during the morning hours on 27 August 2008. Note the improvement in image-to-image navigation on the GOES-13 data (less “wobble” of the images), due to changes in the spacecraft design on the newer GOES-13 satellite.

A comparison of GOES-11 and GOES-13 water vapor channel images (below) demonstrates the improved detection of mesoscale mountain waves over far southwestern Alberta and northwestern Montana on that same day. The spatial resolution of the GOES-13 water vapor channel is 4 km, compared to 8 km on the older GOES-11 satellite.

GOES-11 and GOES-13 water vapor images (Animated GIF)

GOES-11 and GOES-13 water vapor images (Animated GIF)

Mountain waves seen on water vapor imagery have long been recognized as an indicator of potential clear air turbulence. There was one pilot report (PIREP) of light to moderate turbulence at an altitude of 32,000 feet near Great Falls, Montana around 17:40 UTC (below).

AWIPS image of GOES water vapor image + PIREP

AWIPS image of GOES water vapor image + PIREP