Evaluations of upper-level turbulence diagnostics by graphical turbulence guidance (GTG) in the East Asia

Forecasting algorithm of upper-level turbulence, the Graphical Turbulence Guidance (GTG) system developed at National Center for Atmospheric Research (NCAR), is evaluated with available turbulence observations (e.g., pilot reports; PIREPs) reported in the East Asia during 6 years (2003–2008). PIREPs used in this study are received from the NCAR/RAL (Research Application Laboratory) and the Korea Aviation Meteorological Agency (KAMA). Among total number of PIREPs (27,028) within a time window (±2 hrs) around the current NWP model time (00 and 12 UTC), null (NIL), light (LGT), and MOG (moderate or greater) intensity of PIREPs are 16,959 (63%), 8,914 (33%), 1,155 (4%), respectively. To examine dependency of the GTG system for NWP model, the GTG system is applied to both the Regional Data Assimilation and Prediction System (RDAPS) analyses data with 30 km horizontal grid spacing provided by Korean Meteorological Administration (KMA) and the Global Forecasting System (GFS) analyses data with 0.33º×0.33º horizontal grid spacing provided by National Center for Environmental Prediction (NCEP). In order to investigate the best forecasting skill of the GTG system, various statistical examinations and sensitivity tests of the GTG system are performed by yearly and seasonally classified PIREPs in the East Asia.