Why Operational Meteorologists Need More Satellite Soundings

Traditionally, operational meteorologists use radiosondes and numerical weather prediction models (NWP) to build an understanding of dynamic atmospheric processes. Forecasters trust and understand these data sources and are slow to adopt new technologies, lest it compromises the quality of their decision-making. Hyperspectral satellite sounding technology first became available in 2002 but it took more than a decade before its release within the National Weather Service’s (NWS) Advanced Weather Interactive Processing System (AWIPS-II). Now forecasters use satellite soundings alongside radiosondes and NWP to build their conceptual models of severe weather.

The system NOAA adopted in 2008 to generate satellite soundings from all present and future low-Earth orbiting (LEO) platforms is the NOAA-Unique Combined Atmospheric Processing System (NUCAPS). NUCAPS retrieves soundings as profiles of temperature and moisture as well as column amounts of trace gases from the top-of-atmosphere radiance measurements made by two types of sounders: microwave and hyperspectral infrared. The former stabilizes the error due to clouds while the latter captures variation of the vertical atmosphere. Hyperspectral technology achieves a vertical resolution that is an order of magnitude higher than those achievable by any of other type of space-based instrument, which means that NUCAPS generates unique products that give forecasters a detailed view of the three-dimensional atmosphere (latitude x longitude x height) from space.

In May 2018, developers and meteorologists together evaluated the real-time value of NUCAPS soundings from the Suomi-NPP platform in pre-convective forecasting. The Suomi-NPP has a local overpass time of 01:30 am/pm and is thus well-positioned to capture conditions ahead of afternoon convection. We saw forecasters interrogate individual NUCAPS soundings, like they would interrogate radiosondes, but that was not all. With wide swaths of satellite soundings available from each overpass, forecasters also interrogated the spatial gradients of temperature and moisture by visualizing their values at different pressure levels (or heights), i.e., horizontal slices through the swaths of vertical profiles. By the end of the evaluation, forecasters asked to have additional access to NUCAPS soundings from the NOAA-20 platform. This would not only increase the data load but add a critically important fourth dimension, namely time.

The goal of this presentation is two-fold, (i) we will give an overview of the ways in which forecasters have learned to exploit this non-traditional sounding product (i.e, NUCAPS), and (ii) we will present some of the novel ways in which a time-sequence of NUCAPS soundings could add value in future.