1. USING GOES-R TO HELP MONITOR UPPER LEVEL SO2
Anthony J. Schreiner*, Timothy J. Jun Li*, Gary P. Ellrod#, Mat Gunshor*
*Cooperative Institute for Meteorological Satellite Studies (CIMSS) @NOAA/NESDIS #NOAA/NESDIS
University of Wisconsin Office of Research and Applications Office of Research and Applications
Madison, WI Madison, WI Camp Springs, MD
Introduction
Background – Current GOES
GOES-R
GOES Imager
Monitoring of SO2 plumes resulting from volcanic eruptions is not only possible via remote sensors, but also useful in that SO2 plumes are associated with volcanic ash clouds. The picture at left shows a volcanic eruption on the island of Montserrat in
GOES ABI
The current GOES Imager (including GOES-12) is not capable of detecting upper-level SO2. This is demonstrated via the sensitivity figure at right.
The figure to the left shows the original and current band widths proposed for the GOES-R Advanced Baseline Imager (ABI), the next generation Imager for the GOES platform. Unlike the current Imager, monitoring of some upper
Figure Upper Right: Top half is calculated earth-emitted infrared spectrum for a “normal” atmosphere (purple) and “SO2 enriched” atmosphere (blue), and spectral response functions for GOES-8 –11 Water Vapor Band (WVB) (6.7 m) and GOES-12 WVB (6.5 m), both in red. Lower half is the difference between “normal” and “SO2 enriched” atmospheres (green).
Figure Lower Left: Same as Upper Right except for the three WVB’s (7.4 m, 7.0 m, and 6.5 m) of the GOES Sounder.
the Eastern Caribbean during the period July This case was used to show the capability of the current Geostationary Operational Environmental Satellite sensing instruments to observe the resulting plume from this eruption. It also is an opportunity to show the potential for the GOES-R platform to monitor these eruptions.
Such an event is within the sensitivity of both the current GOES Sounder and GOES-R ABI as is shown by the figures below.
GOES Sounder
The current version of the GOES Sounder is capable of detecting some upper-level SO2 as is shown in the figure at left. Spatial resolution of the instrument is 10 km at the satellite sub-point and a theoretical refresh rate of one hour. It should be noted that in the tropical regions, where most of
level SO2 will be possible. The image (below, right) is a derived, simulated GOES-R ABI product. From Atmospheric Infrared Sounder (AIRS) measurements, a 7.34 m and 13.3 m bands are convolved. Then the two simulated ABI bands are differenced. Given the improved
spatial resolution and properly defined band width derived images of this type provide the detailed information needed for monitoring SO2 and consequently volcanic ash clouds resulting from volcanic eruptions. The spatial resolution will also be improved. Instead of hourly derived imagery of this type (in reality once every six hours), for ABI it will be possible to obtain at least fifteen minute imagery.
the active volcanoes seen by the GOES Sounder are located, the current refresh rate is once per six hours. In addition to the three water vapor bands shown above, the GOES Sounder consists of an additional 15 IR bands and one visible band.
Case Study – Current GOES
The first major eruption of this case study occurred around 0230 UTC on 13 July. This was triggered by a major collapse of the Soufriere Hills lava dome. The resulting ash plume reached a level of approximately 16 km based on estimates from the Volcanic Ash Advisory Center in Washington, D.C. A calculation of SO2 concentration (Dobson Units) based on AIRS radiance information (figure, upper left) from 13 July at 1653 UTC shows a plume
extending toward the northeast from Montserrat Island. Using a trajectory model (NOAA HYSPLIT Model), forward trajectories were calculated (lower left).
Lower right is a series of figures showing GOES Sounder bands 10, 8, and 5 and band 10 minus band 5, top to bottom, respectively. The derived image is obtained in order to, effectively, subtract out the background temperature difference, since these two bands are “sensing” the same layer of the atmosphere. The resulting difference band shows the “SO2 plume” (dark areas) over an 18 hour period following the eruption.
7.4 m (Band 10)
GOES HES
The GOES Hyperspectral Environmental Suite (HES) sounder should include the SO2 absorption regions in order to permit quantitative measurements and monitor smaller events. Given the refresh rate and spatial and spectral resolution of HES it will be possible to quantify diurnal changes during volcanic eruptions.
These figures were provided by Dr. Fred Prata of CSIRO.
11.0 m (Band 8)
13.3 m (Band 5)
Summary
The current GOES Sounder is able to detect upper-level SO2 on relatively crude spatial and temporal scales.
GOES-R ABI and HES together have the potential to delineate upper level SO2 at unprecedented scales, possibly including quantitative estimates of SO2.
Band 10 – Band 5
13 July UTC
13 July UTC
13 July UTC
14 July UTC