Comparison of Precipitation Representation from GPM and MICRE over the Southern Ocean

Abstract:

The NASA-JAXA Global Precipitation Measurement (GPM) Mission demonstrates agreement between zonal precipitation averages from its range of products within the ±35˚ latitude limits; however, there is disagreement between its global-gridded product (IMERG) and instantaneous products (DPR, GMI, CORRA) from the Core Observatory dual-frequency precipitation radar and microwave imager measurements at higher latitudes. The Southern Ocean provides the largest discrepancies beyond the sub-Tropics, where the IMERG version-6 final run product can exceed the zonal mean precipitation accumulation from the CORRA version-5 product by up to a factor of three. The fact that the IMERG algorithm includes calibration of its precipitation estimates to the CORRA product suggests issues with the IMERG algorithm that require investigating. This study aims to identify the cause of the GPM product differences by exploiting precipitation measurements (gauges, W-band radar, and disdrometers) collected over Macquarie Island (Latitude: 54.6˚, Longitude: 158.9˚), situated midway between Australia and Antarctica in the South-Western Pacific Ocean. Collection of the data took place during the Macquarie Island Cloud and Radiation Experiment (MICRE) over a year period (April 2016 – March 2017); MICRE data are intercompared to the different satellite products, and biases of the GPM products are identified and discussed in relation to the different precipitation regimes.