Development of the Korean Mid- and Upper-Level Aviation Turbulence Guidance (KTG) System Using the Regional Unified Model

Abstract

Abstract Korean mid- and upper-level aviation turbulence guidance (KTG) system isdeveloped using the unified model (UM)-based regional data assimilation and prediction system(RDAPS) of the Korea Meteorological Administration. The KTG system includes three steps.First, the KTG system calculates a suite of diagnostics in the UM-RDAPS domain. Second,component diagnostics that have different units and numerical magnitudes are normalized intothe values between 0 and 1, according to their own thresholds in the KTG system. Finally,normalized diagnostics are combined into one KTG predictor by measuring the weighting scoresbased on the probability of detection, which is calculated using the observed pilot reports(PIREPs) exclusively of moderate-or-greater (MOG) and null (NIL) intensities. To investigatethe optimal performance of the KTG system, two types (RD-KTG and UM-KTG) of the KTGsystems are developed and evaluated using the PIREPs over Korea and East Asia. Componentdiagnostics and their thresholds in the RD-KTG are founded on the 8-yrs (2002.12-2010.11)MM5-based RDAPS (previous version of the RDAPS; ∆x = 30 km) and PIREPs data, whilethose in the UM-KTG are based on the 6 months (2010.12-2011.5) UM-based RDAPS (∆x =12km)and PIREPs data. In comparison between the RD-KTG and UM-KTG, overall performance ofthe UM-KTG (0.815) is better than that of the RD-KTG (0.79) during the recent 6 months,because forecasting skill for the upper-level wind is higher in the UM-RDAPS than in the MM5-RDAPS. It is also found that the UM-KTG is more efficient than the RD-KTG according to thestatistical evaluations and sensitivity tests to the number of component diagnostics. Keywords: mid- and upper-level turbulence, PIREPs, KTG system, forecasting skill