Towards an Operational NOAA GEO Hyperspectral Infrared Sounder

This paper describes technologically mature options available to fly an operational hyperspectral IR sounder over the U.S. on a geostationary satellite in the near-term, as well as the business case for doing so.

The 2018 Earth Science and Applications from Space (ESAS) Decadal Survey, “Thriving on Our Changing Planet: A Decadal Strategy for Earth Observation from Space,” identified several “most important” objectives, including: “What planetary boundary layer (PBL) processes are integral to the air-surface exchanges of energy, momentum and mass, and how do these impact weather forecasts and air quality simulations? Why do convective storms, heavy precipitation, and clouds occur exactly when and where they do?” Only a GEO hyperspectral IR sounder has the technological maturity today to answer these questions and, in doing so, address the NOAA National Weather Service vision to “provide weather, water, and climate data, forecasts and warnings for the protection of life and property and enhancement of the national economy.” Such a GEO sounder could fill both a weather satellite role and a unique severe weather satellite role. Polar sounders deliver inadequate temporal coverage, GPS occultations are inadequate in both spatial resolution and temporal coverage, the ABI instrument delivers inadequate vertical resolution, while GEO microwave would deliver a vertical resolution 2-3 times lower. China has flown their Geosynchronous Interferometric Infrared Sounder (GIIRS) for over two years. The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) is developing an operational advanced hyperspectral GEO IR sounder (IRS) as a part of Meteosat Third Generation (MTG-3) in the mid 2020’s.

The PBL plays a critical role in the initiation of convective storms, including those that may evolve into long-lived supercell storms. These are influenced by the Convective Available Potential Energy (CAPE), as well as inhibition and triggering mechanisms which together determine the likelihood of deep convection. The chief aim of the International H2O Project (IHOP_2002) was improved characterization of the 4D distribution of water vapor and its application to improving the understanding and prediction of convection. A GEO hyperspectral IR sounder OSSE for storm nowcasting by Revercomb et al., based on a WRF model run for the 12-13 June 2002 IHOP experiment at 3-km resolution, conclusively showed that an operational GEO hyperspectral IR sounder could observe the evolution of the PBL and provide well-focused instability (e.g., CAPE) and warning information hours before NEXRAD radars show returns.

In 2009, a recommended WMO 2025 vision for the space-based component of the Integrated Global Observing System (WIGOS) for the operational geostationary satellite constellation included “at least 6, separated by no more than 70 deg longitude, [accommodating] high-resolution multi-spectral Vis/IR imagers, lightning imagers, and IR hyperspectral sounders.” The Implementation Plan for the Evolution of Global Observing Systems (EGOS-IP; WIGOS TR No. 2013–4) noted at the time that “the evaluation of the potential of hyperspectral sounders on GEO was performed with the GIFTS mission...Several operators of geostationary satellites have firm plans to include hyperspectral IR sounders for the next series of satellites...These planned sounders put the emphasis on high horizontal resolution (better than 10km), and on high vertical resolution (about 1km). Their main objective is to provide frequent information on the 3D structure of atmospheric temperature and humidity, for the whole Earth disk.” The EGOS-IP set as an action: “All meteorological geostationary satellites should be equipped with hyperspectral IR sensors for frequent temperature and humidity soundings, as well as tracer wind profiling with adequately high resolution (horizontal, vertical, time) [by] 2015-2025 for making the instruments operational.”