Diagnosing and Addressing Systematic Errors in the Navy’s NEPTUNE Prediction System

The Navy Environmental Prediction System Using a Nonhydrostatic Engine (NEPTUNE) is a next-generation global NWP system being developed at the Naval Research Laboratory (NRL). NEPTUNE makes use of a spectral element dynamical core. In this presentation, we will discuss the implementation and testing in NEPTUNE of different physical parameterization suites available in the Common Community Physics Package (CCPP). NEPTUNE global atmospheric predictions have been performed with horizontal grid spacings ranging from 9 to 19 km. We will discuss systematic errors that have been identified and address the sensitivity of these biases to changes in shallow and deep convective parameterizations. We conducted numerous NEPTUNE simulations with different physics configurations and evaluated the forecast skill and numerical stability. We show that using a CCPP physics suite implemented with the Tiedtke convection parameterization performs statistically better than the same suite using the simplified Arakawa and Schubert (SAS) parameterizations through comparisons with ERA-5 reanalyses, NASA’s Clouds and the Earth's Radiant Energy System (CERES), and NASA's Integrated Multi-satellitE Retrievals for GPM (IMERG) datasets.