Using NUCAPS profiles before Pyrocumulus events

September 11th, 2022 |
GOES-17 True-color imagery, 2101 UTC 10 September to 0106 UTC on 11 September

A CSPP Geosphere mp4 animation from late on 10 September, above (link), shows the development of a pyrocumulus cloud at the south edge of the Cedar Creek fire complex in Oregon (previously discussed here, here and here). The animation above starts at 2101 UTC, shortly after a NOAA-20 overpass above the region. NUCAPS profiles over the regions can define the thermodynamics to help forecasters determine is pyrocumulus clouds might develop. The Green points in the sounding availability plots, below, denote retrievals that converged to a solution using both microwave and infrared data from the ATMS and CrIS instruments, respectively. This includes the profiles near the very warm Cedar Creek fire pixels in east-central Oregon. (Here is a zoomed-in view over the fire with GOES-17 FDCA Fire Power observations; note the two different regions of active fire).

GOES-17 Band 7 (3.9 µm) imagery at 2020 UTC on 10 September 2022 along with NUCAPS Sounding Availability plots (Click to enlarge)

The animation below steps through 3 NUCAPS profiles near the fire. A dry atmosphere is apparent, but note also the very steep lapse rates. If convection develops, aided by the heat of the fire, there is little to inhibit its growth to the tropopause.

NUCAPS profiles east, over and west of the Cedar Creek fire, ca. 2050 UTC on 10 September 2022 (Click to enlarge)

NUCAPS profiles can be gridded to provide horizontal fields of thermodynamic variables. The lapse rate computed from 850 and 500 mb temperatures, below, also shows very steep lapse rates (note that portions of Oregon are at/above 850 mb and no data are available).

GOES-17 Band 7 (3.9 µm) imagery along with NUCAPS gridded lapse rates (850-500 mb), ca. 2030 UTC on 10 September 2022 (Click to enlarge)

One things that happens when a Pyrocumulus develops: the cloud is trackable (in contrast to any surrounding smoke). The CSPP Geosphere animation below (link) shows the Night Microphysics (at night) and True-Color (during the day) — the cloud can be tracked until is dissipates near dawn, and the true-color imagery the next day shows the smoke associated with the pyrocumulus has also moved to the east. Note also in the animation how the active fires show up in the GOES-17 Night Microphysics as different shades of magenta.

Hourly imagery from CSPP Geosphere, 2206 10 September 2022 – 1706 UTC on 11 September 2022

Although infrared imagery is challenged to view smoke at night, as suggested in the animation above, the VIIRS Day Night band sees it (if there is sufficient illumination by the Moon). That was the case early on 11 September, as shown below (in an image taken from the VIIRS Today website). Both the light signature from fires are apparent as is the smoke plume from the pyrocumulus.

NOAA-20 Day Night Band visible (0.7 µm) imagery over Oregon, ca. 1100 UTC on 11 September 2022 (click to enlarge)

AWIPS Satellite imagery in this blog post were created using the TOWR-S AWIPS. Thank you!

5.1 micrometers and IASI

September 11th, 2022 |

A previous post discussed the 5.1 micrometer channel that might be part of the imager (GXI) to fly on GeoXO, the next-generation satellite (beyond GOES-R) to be launched in the 2030s. That previous post, however, used Cross-track Infrared Sounder (CrIS) data, and CrIS observes close to, but not at, 5.1 micrometers. However, the Infrared Atmospheric Sounding Interferometer (IASI) that is part of the payload on Metop-B and Metop-C (it was on Metop-A as well!) does take observations at 5.1 micrometers. The animation shows a Metop-A IASI observations at 5.1, 6.19, 6.9 and 7.3 micrometers (or wavenumbers 1950, 1615, 1438 and 1369) from a granule over Europe. Of note is apparent moisture aloft — shown as cooler brightness temperatures especially at 6.9 micrometers — that has no apparent signal at 5.1 micrometers because of less sensitivity to mid-tropospheric water vapor at the shorter wavelength. Indeed, 5.1 micrometer brightness temperatures are much warmer than the other channels.

Metop-A observations at 5.1, 6.19, 6.9 and 7.3 micrometers, 1140 UTC on 15 January 2007. (Click to enlarge)

A greyscaled image of 5.1 micrometers, below, shows how the boundary layer influences the signal in clear air.

5.1 micrometer image from IASI data (click to enlarge)

What did geostationary imagery look like on this day? Meteosat-8 imagery at 6.19 and 7.3 micrometers is shown below.

Meteosat-8 Bands 5 and 6 (6.2 and 7.3 micrometers) at 1930 UTC on 15 January 2007 (Click to enlarge)

How dry was this airmass over the Mediterranean? Soundings from 0000 and 1200 UTC on 15 January 2007 (link, from the Wyoming Sounding site) show total precipitable water values between 10 and 14 mm.

The addition of the 5.1 micrometer channel is designed to aid in convective forecasting: gradients in water vapor very low in the atmosphere should be apparent.