Global Precipitation Mission (GPM) satellite data is crucial to weather decision making and historical precipitation climatological analysis. The production information at the NASA STORM website is made available anywhere from 24 to 36 hours after the original satellite flyover, while near real-time (NRT) data is output within 30 minutes for GPM microwave imagery (GMI) and 2 hours for dual-frequency precipitation radar (DPR). However, there had been no place for visualization of NRT data until GPMNRTView.
Matt Lammers, web analyst/developer for the NASA Precipitation Processing System (PPS), has developed a pipeline for efficiently processing the GPM NRT HDF5 files into CZML and making those files available for visualization for a rolling 12-hour period. Swath-based file sizes are kept small by tracking a cross-track set of pixels as they change through time rather than storing positions and visibility information for every pixel in the segment. This allows for further condensing of space by only tracking changes in color rather than storing each value for each instrument scan. This does force the user to step through time to make data appear, but this can be sped up using the Cesium time widget controls.
Four products are available in GPMNRTView. Level 2A DPR is a narrow swath-based product that plots data points at storm top height, rather than on the surface, to provide a 3D representation of precipitation. Level 1C GMI is a wider swath-based product showing various brightness temperatures at various frequencies. Depending on the frequency, different atmospheric properties can be teased from the information, including wind speed and precipitation intensity. Level 2A GPROF takes the Level 1C GMI data and algorithmically converts it into precipitation information, such as probability of precipitation and precipitation rate.
The final product, Level 3 IMERG-Half Hour, takes information from several precipitation satellites along with model data and surface observations and generates precipitation rate information for a 0.1 × 0.1 degree latitude/longitude grid for a given half hour period with a latency of approximately 3 hours. With this data, not only is the entire globe shown at once (rather than information appearing for a swath as it animates), but also the data points can be moused-over to see the raw values.