OSSE with NGGPS to Evaluate and Improve the Usage of Arctic Observations. Preparation for YIOO and beyond.

Recently as the Arctic sea ice has declined, the impact of Arctic weather on midlatitude extended-range forecasts has been widely discussed. However, the detailed results are not proven and the impact of Arctic observations requires dedicated research effort. For the Year of Polar Prediction (YOPP, 2017- 2019), forecast and verification systems in the Arctic need to be improved and an effective observing system must be evaluated.

This project relies on development of operational community, and newly developed capabilities will be evaluated through this project. The impact of Arctic observations using Observing System Experiments (OSE) and Observing System Simulation Experiments (OSSE) on global weather and climate forecasts will be evaluated using the recently developed Next Generation Global Prediction System (NGGPS). New NGGPS systems will be tested and evaluated using idealized data sets. Newly developed Community Radiative Transfer Model (CRTM), Community Surface Emissivity Model (CSEM), and arctic verification package will be also applied and evaluated.

Global OSSEs will be performed at relatively low resolution, and high resolution OSSEs will be conducted using a regional model and data assimilation. The results will be compared with theoretical predictions of the impact. In this project, OSSEs with idealized observations will be conducted in the initial stage. From previous experience, simulation of realistic observations requires significant resources and even so it is difficult to determine the realistic impact. Emissivity models over ice and snow require much more development otherwise they will introduce serious uncertainty to the evaluation of Arctic observations. Idealized observations will be designed based on the distribution of planned potential observations. Ground-based profilers, ship observations from the newly opened Arctic Ocean, and space-based observations such as GPS Radio Occultation, Doppler Wind Lidar, and Microwave and Infrared sounders, will be evaluated.

First, OSSE will be conducted in an academic environment with relatively low global resolution. The impact of higher resolution will be investigated with a regional OSSE for the Arctic employing advanced physics.

The Nature Run by a forecast model which has demonstrated extended range forecast skill will be produced by ECMWF. It will be acquired through NOAA and will be hosted at NCAR to be shared with the international scientific community through Joint OSSE (jointosse.org).