With STORM Virtual Globe, Matt Lammers from the NASA Precipitation Processing System (PPS) group established a way to visualize the two- and three-dimensional precipitation data acquired from the Global Precipitation Measurement (GPM) Core satellite. However, for outreach purposes, PPS wanted to highlight specific high-impact events that GPM has observed since its launch in early 2014. This tool is updated frequently when GPM flies over new major events such as tropical cyclones and outbreaks of tornadoes. The tool is now known as STORM Event Viewer.

GPM is a collaborative effort between the United States’ National Aeronautic and Space Administration (NASA) and the Japan Aerospace Exploration Agency (JAXA). It has two primary instruments: the Dual-frequency Precipitation Radar (DPR) and GPM Microwave Imager (GMI). DPR provides 3D scans of snow and liquid water above the Earth’s surface. GMI observes the brightness temperature of microwave radiation coming from Earth at numerous different frequencies. Both instruments combine to provide a thorough assessment of precipitation rates and types as the satellite orbits Earth once every 90 minutes between 65 N and 65 S latitude.

STORM Event Viewer combines the data from both of these instruments to tell a story about a weather system. The wide swath of surface precipitation calculated using GMI data gives the regional context for precipitation, and it can sometimes capture the structure of a storm when the DPR swath is too narrow to see it. The DPR swath provides a thin band of 3D information that illustrates how deep convection is, what the precipitation type transition is like in taller clouds, and how healthy the eye of a tropical cyclone appears.

Much as in STORM Virtual Globe, STORM Event Viewer generates simple JSON files server-side on the fly from HDF5 binary files. These JSON files provide latitude, longitude, elevation, and precipitation rate values from which CesiumJS can then generate pointPrimitive objects. Because some of these events garner a lot of attention, JSON files are sometimes generated and stored ahead of time to minimize server impact and prevent latency.

To broaden the appeal of STORM Event Viewer, PPS adapted the interface to make it more friendly for mobile/tablet users and to enable its embedding in NASA news releases and articles. EVMini is stripped down for smaller screens, although it maintains the ability for users to view individual data point values and to read brief summaries of the events for context. It runs smoothly despite all of the points being displayed because CesiumJS is so mobile-friendly. EVMicro is designed to be embedded, so it removes all of the controls, preserving a simple interactive visualization that highlights the satellite data and the ability to delineate between frozen and liquid precipitation in the DPR scan.