Observing System Experiment Impacts from Various Satellite Instruments using the NCEP Global Data Assimilation System

Observing system experiments (OSEs), during two seasons are used to quantify the contributions made to the forecast quality by removing specific instrument types of satellite data. The impacts are measured by comparing the analysis and the forecast results from an assimilation-forecast system using all data types with those individually excluding AMSU-A, MHS, GPS-RO, Hyperspectral (AIRS and IASI) and Atmospheric Motion Vectors (Polar and Geostationary) satellite data. For these observing system experiments, forecast results are compared through 168 h for periods covering more than a month during both the summer and winter seasons of each hemisphere. The assimilation –forecast system used for these experiments is the National Centers for Environmental Prediction (NCEP) Global Data Assimilation System (GDAS) and the Global Forecast System (GFS). The May 2011 version of the GDAS/GFS, at a resolution of T574L64 will be used. The case studies chosen consist of 67 days beginning 1 December 2010 and 1 August 2011. The first 15 days are ignored to allow the GDAS/GFS to adjust to the missing data. Impact statistics are derived from the 45 days following the adjustment period. Anomaly correlations (ACs) of extratropical geopotential heights by hemisphere, root-mean-square (RMS) errors of winds in the tropics, forecast impacts (FIs), and hurricane track forecasts are evaluated for experiments run during both seasons.