A Detailed Examination of the GPM Core Satellite Gridded Text Product

4. Data Line Content Details mm/hr convective fraction liquid fraction 1. Background The Global Precipitation Measurement (GPM) mission quarter-degree gridded-text product has a similar file format and a similar purpose as the Tropical Rainfall Measuring Mission (TRMM) 3G68 quarter-degree product. The GPM textgrid format is an hourly summary of surface precipitation retrievals from various GPM instruments and combinations of GPM instruments. The GMI Goddard Profiling (GPROF) retrieval provides the widest swath (800 km) and does the retrieval using the GPM Microwave Imager (GMI). The Ku radar provides the widest radar swath (250 km swath) and also provides continuity with the TRMM Ku Precipitation Radar. GPM's Ku+Ka band matched swath (125 km swath) provides a dual-frequency precipitation retrieval. The "combined" retrieval (125 km swath) provides a multi-instrument precipitation retrieval based on the GMI, the DPR Ku radar, and the DPR Ka radar. While the data are reported in hourly grids, all hours for a day are packaged into a single text file that is gzipped to reduce file size and to speed up downloading. The data are reported on a 0.25° x 0.25 ° grid. Each data line has a value for each item named in line 5 of the header and described in section 3. Hour values start at 0 as do minutes. Time in this product is presented in UTC. As a reminder, the grid-cell row index for the hourly grid matrix starts at 0 as does the gridcell column index. Users can be assured that each data line has the same number of fields on it, but users should check whether a field contains the missing-data value (-9) before using that field in their calculations. If any instrument group has a 0 value for the total-pixels field that would indicate that the instrument group has no observations falling within that grid box for that hour. In this situation, the textgrid has the precip-pixels field set to zero and all subsequent fields for that instrument group set to -9. Any occurrence of -9 always indicates that a value is not available for this item for the particular grid box and hour. When a level 2 retrieval product does not provide the information necessary for determining the field value in the gridded text product then the missing value indicator is used for the field. Currently, the retrieval quality flag for the grid is determined by the pixel with the lowest ) 1 ( ) 1 ( column and row at gridbox for the count Pixel 1. Eq.