• 대기
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• 제21권4호
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• pp.497-506
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• 2011

Korean mid- and upper-level aviation turbulence guidance (KTG) system is developed 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 into the 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 scores based 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 investigate the optimal performance of the KTG system, two types (RD-KTG and UM-KTG) of the KTG systems are developed and evaluated using the PIREPs over Korea and East Asia. Component diagnostics 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; ${\Delta}x$ = 30 km) and PIREPs data, while those in the UM-KTG are based on the 6 months (2010.12-2011.5) UM-based RDAPS (${\Delta}x$ = 12 km) and PIREPs data. In comparison between the RD-KTG and UM-KTG, overall performance of the 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 the statistical evaluations and sensitivity tests to the number of component diagnostics.

• 한국항공운항학회지
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• 제20권4호
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• pp.76-83
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• 2012

Korean aviation Turbulenc Guidance (KTG) system is developed using the operational unified model (UM) of the Korea Meteorological Administration (KMA) and pilot reports (PIREPs) over East Asia. The KTG system comprised of twenty turbulence diagnostics that represent various turbulence potentials and have the best forecasting skills, which are combined into a single ensemble-averaged index, namely KTG, at upper-(above FL250) and mid-(below FL250) levels. It is found that the overall performance of the KTG is higher than those produced from the one single best index, and satisfies the minimum criteria (80% accuracy) that the system is operationally useful in aviation industry.

• 한국항공운항학회지
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• 제15권4호
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• pp.94-99
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• 2007

The purpose of this study is analysis of aircraft turbulence of mid Korea using VWS from Osan radiosonde data and comparison with the PIREPs reporting the aircraft turbulence during $1990{\sim}1999$. The results of this study summarized that the frequence of aircraft events is more higher in winter time and in lower level(near the surface) of the atmosphere from VWS analysis using radiosonde data. And comparison with PIREPs data shows that relatively high skill score(44%) using the VWS method. It appears that the operational forecast skill score of aircraft turbulence is much higher using VWS than empirical method, due to the upgrade of the discrimination criteria of the aircraft turbulence.

• 한국항공운항학회지
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• 제19권3호
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• pp.54-60
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• 2011

The purpose of this study is verification of threshold of the aircraft turbulence index and icing index using PIREPs and KWRF on Korean peninsula, to operational weather support. There is improvement in new threshold value made of the pilot weather report data and the turbulence and icing index from KWRF model result, using the ROC Diagram method. the accuracy is up to 0.6 compared with the precedent study result 0.5. Through this study, It is founded on the research and development of the Korean peninsula aircraft turbulence and icing.

• 대기
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• 제19권3호
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• pp.269-287
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• 2009

CAT (clear-air turbulence) forecasting algorithm, the Graphical Turbulence Guidance (GTG) system developed at NCAR (national center for atmospheric research), is evaluated with available observations (e.g., pilot reports; PIREPs) reported in South Korea during the recent 5 years (2003-2008, excluding 2005). The GTG system includes several steps. First, 44 CAT indices are calculated in the domain of the Regional Data Assimilation and Prediction System (RDAPS) analysis data with 30 km horizontal grid spacing provided by KMA (Korean Meteorological Administration). Second, 10 indices that performed ten best forecasting scores are selected. Finally, 10 indices are combined by measuring the score based on the probability of detection, which is calculated using PIREPs exclusively of moderate-or-greater intensity. In order to investigate the best performance of the GTG system in Korea, various statistical examinations and sensitivity tests of the GTG system are performed by yearly and seasonally classified PIREPs. Performances of the GTG system based on yearly distributed PIREPs have annual variations because the compositions of indices are different from each year. Seasonal forecasting is generally better than yearly forecasting, because selected CAT indices in each season represent meteorological condition much more properly than applying the selected CAT indices to all seasons. Wintertime forecasting is the best among the four seasonal forecastings. This is likely due to that the GTG system consists of many CAT indices related to the jet stream, and turbulence associated with the jet stream can be activated mostly in wintertime under strong jet magnitude. On the other hand, summertime forecasting skill is much less than other seasons. Compared with current operational CAT prediction system (KITFA; Korean Integrated Turbulence Forecasting System), overall performance of the GTG system is better when CAT indices are selected seasonally.

• 대기
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• 제19권3호
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• pp.255-268
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• 2009

Based on the pilot reports (PIREPs) collected in South Korea from 2003 to 2008 and corresponding Regional Data Assimilation and Prediction System (RDAPS) analysis data of 30 km resolution, we validate the Korean Integrated Turbulence Forecasting Algorithm (KITFA) system that predicts clear-air turbulence (CAT) above the Korean peninsula. The CATs considered in this study are the upper level (higher than 20000 ft) turbulence excluding convectively induced turbulences. In the KITFA system, there are two main processes for predicting CATs: to select CAT indices and to determine their weighting scores. With the PIREPs observed for much longer period than those used in the current operational version of the KITFA system (March 4-April 8 of 2002), three improvable processes of the current KITFA system, re-calculation of weighting scores, change of method to calculate weighting scores, and re-selection of CAT indices, are tested. The largest increase of predictability is presented when CAT indices are selected by using longer PIREP data, with the minor change using different methods in calculation of weighting scores. The predictability is the largest in wintertime, and it is likely due to that most CAT indices are related to the jet stream that is strongest in wintertime. This result suggests that selecting proper CAT indices and calculating their weighting scores based on the longer PIREPs used in this study are required to improve the current KITFA.

• 대기
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• 제25권2호
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• pp.367-374
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• 2015

Korean Peninsula has high potential for occurrence of aviation turbulence. A Korean aviation Turbulence Guidance (KTG) system focused on the Korean Peninsula, named Korean-Peninsula KTG (KP-KTG) system, is developed using the high resolution (horizontal grid spacing of 1.5 km) Local Data Assimilation and Prediction System (LDAPS) of the Korea Meteorological Administration (KMA). The KP-KTG system is constructed first by selection of 15 best diagnostics of aviation turbulence using the method of probability of detection (POD) with pilot reports (PIREPs) and the LDAPS analysis data. The 15 best diagnostics are combined into an ensemble KTG predictor, named KP-KTG, with their weighting scores computed by the values of area under curve (AUC) of each diagnostics. The performance of the KP-KTG, represented by AUC, is larger than 0.84 in the recent two years (June 2012~May 2014), which is very good considering relatively small number of PIREPs. The KP-KTG can provide localized turbulence forecasting in Korean Peninsula, and its skill score is as good as that of the operational-KTG conducting in East Asia.

• 대기
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• 제24권2호
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• pp.235-243
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• 2014

Sources of aviation turbulence vary through the seasons, especially in the East Asia including Korean peninsula, associated primarily with the changes in the jet/front system and convective activities. For this reason, a seasonal Korean aviation Turbulence Guidance (KTG) system (seasonal-KTG) is developed in the present study by using pilot reports (PIREPs) and analysis data of the operational Unified Model (UM) of the Korea Meteorological Administration (KMA) for two years between June 2011 and May 2013. Twenty best diagnostics of aviation turbulence in each season are selected by the method of probability of detection (POD) using the PIREPs and UM data. After calculating a weighting value of each selected diagnostics using their area under curve (AUC), the 20 best diagnostics are combined with the weighting scores into a single ensemble-averaged index by season. Compared with the current operational-KTG system that is based on the diagnostics applying all seasons, the performances of the seasonal-KTG system are better in all seasons, except in fall.

• 대기
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• 제27권2호
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• pp.119-131
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• 2017

We present and discuss the Tropopause Folding Turbulence Detection (TFTD) algorithm for the Korean Communication, Ocean, Meteorological Satellite (COMS) which is originally developed for the Tropopause Folding Turbulence Product (TFTP) from the Geostationary Operational Environmental Satellite (GOES)-R. The TFTD algorithm assumes that the tropopause folding is linked to the Clear Air Turbulence (CAT), and thereby the tropopause folding areas are detected from the rapid spatial gradients of the upper tropospheric specific humidity. The Layer Averaged Specific Humidity (LASH) is used to represent the upper tropospheric specific humidity calculated using COMS $6.7{\mu}m$ water vapor channel and ERA-interim reanalysis temperature at 300, 400, and 500 hPa. The comparison of LASH with the numerical model specific humidity shows a strong negative correlation of 80% or more. We apply the single threshold, which is determined from sensitivity analysis, for cloud-clearing to overcome strong gradient of LASH at the edge of clouds. The tropopause break lines are detected from the location of strong LASH-gradient using the Canny edge detection based on the image processing technique. The tropopause folding area is defined by expanding the break lines by 2-degree positive gradient direction. The validations of COMS TFTD is performed with Pilot Reports (PIREPs) filtered out Convective Induced Turbulence (CIT) from Dec 2013 to Nov 2014 over the South Korea. The score test shows 0.49 PODy (Probability of Detection 'Yes') and 0.64 PODn (Probability of Detection 'No'). Low POD results from various kinds of CAT reported from PIREPs and the characteristics of high sensitivity in edge detection algorithm.

• 한국항공운항학회지
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• 제18권1호
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• pp.89-99
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• 2010

The purpose of this study is analysis of Korean peninsula aircraft turbulence using the numerical weather prediction model, KWRF with the various turbulence index and pilot weather report data. Compared with the pilot weather report data and Calculated the turbulence index using the KWRF model result, many turbulence index show the similar horizontal distribution, except for the TUB2 and VWS. The analysis of vertical structure of turbulence, there are some difference each turbulence index respectively, but severe turbulence turn up in 15,000ft almost turbulence index. above 20,000ft height, intensity of turbulence vary each turbulence index. Through this turbulence study, It is founded on the research and development of the Korean peninsula aircraft turbulence