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Korean Meteorological Society (한국기상학회)
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Bias Correction for Aircraft Temperature Observation Part I: Analysis of Temperature Bias Characteristics by Comparison with Sonde Observation

항공기 온도 관측 자료의 편향 보정 Part I: 존데와 비교를 통한 온도 편향 특성 분석

  • Kwon, Hui-nae (Korea Institute of Atmospheric Prediction Systems (KIAPS)) ;
  • Kang, Jeon-ho (Korea Institute of Atmospheric Prediction Systems (KIAPS)) ;
  • Kwon, In-Hyuk (Korea Institute of Atmospheric Prediction Systems (KIAPS))
  • 권희내 ((재) 한국형수치예보모델개발사업단) ;
  • 강전호 ((재) 한국형수치예보모델개발사업단) ;
  • 권인혁 ((재) 한국형수치예보모델개발사업단)
  • Received : 2018.07.27
  • Accepted : 2018.09.29
  • Published : 2018.12.31
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Abstract

In this study, the temperature bias of aircraft observation was estimated through comparison with sonde observation prior to developing the temperature bias correction method at the Korea Institute of Atmospheric Prediction Systems (KIAPS). First, we tried to compare aircraft temperature with collocated sonde observations at 0000 UTC on June 22, 2012. However, it was difficult to estimate the temperature bias due to the lack of samples and the uncertainty of the sonde position at high altitudes. Second, we attempted a background innovation comparison for sonde and aircraft using KIAPS Package for Observation Processing (KPOP). The one month averaged background innovation shows the aircraft temperature have a warm bias against sonde for all levels. In particular, there is a globally distinct warm bias about 0.4 K between 200 hPa and 300 hPa corresponding to flight level. Spatially, most of the areas showed the warm bias except for below 300 hPa in some part of China at 0000 and 1200 UTC and below 850 hPa in Australia at 0000 UTC. In general, the temperature bias was larger at 1200 UTC than 0000 UTC. Based on the estimated temperature bias, we have applied the static bias correction method to the aircraft temperature observation. As a result, the warm bias of the aircraft temperature has decreased at most levels, but a slight cold bias has occurred in some areas.

Keywords

KSHHDL_2018_v28n4_357_f0001.png 이미지

Fig. 1. Distribution of positions collocated sonde and aircraft temperature observations at 0000 UTC on June 22, 2017. Black and blue dots mean positions of sonde temperature observations at analysis time and aircraft temperature observations within ± 30 minutes from analysis time respectively. Red dots mean positions of sonde and aircraft observations collocated out of black and blue dots.

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Fig. 2. Vertical profile of differences (black dots) between sonde and aircraft temperature (sonde minus aircraft), former altitude average (blue line with dots) and altitude average (red line with dots) of background innovation differences between sonde and aircraft temperature at 0000 UTC on June 22, 2017.

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Fig. 3. Vertical profile of wind speeds of sonde (blue dots) and aircraft (red dots), former altitude average of sonde (blue line) and aircraft (red line) wind speeds at 0000 UTC on June 22, 2017.

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Fig. 4. Distribution of positions about sonde and aircraft observations for a one month at 0000 UTC in June 2017. Black and blue dots mean positions of sonde temperature observations at analysis time and aircraft temperature observations within ± 30 minutes from analysis time respectively. Red boxes mean coverage of analysis data.

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Fig. 5. Vertical profiles of background innovation average of sonde and aircraft temperature for a 1 month at 0000 and 1200 UTC in June 2017 with respect to Global (GL), North America (NA), Europe (EU), East Asia (EA) and Australia (AU) (K).

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Fig. 6. Horizontal distributions of differences about background innovation average between aircraft and sonde temperature that means the aircraft temperature bias for a 1 month at 0000 UTC in June 2017 with respect to 200~300 hPa, 300~500 hPa, 500~850 hPa and 850 hPa~Surface (K). Each value is the minimum, maximum, mean and standard deviation of global aircraft temperature bias.

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Fig. 7. Same as Fig. 6 but for 1200 UTC (K).

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Fig. 8. Vertical profiles of average for aircraft temperature bias before and after bias correction at 0000 and 1200 UTC in June 2017 (K).

Table 1. The number of aircraft and sonde temperature observations for one-month at 0000 and 1200 UTC in June 2017 with respect to Global (GL), North America (NA), Europe (EU), East Asia (EA) and Australia (AU).

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Table 2. Vertical average of background innovation (O-B) and bias-corrected background innovation (C-B) about aircraft temperature for a 1 month at 0000 and 1200 UTC in June 2017 with respect to Global (GL), North America (NA), Europe (EU), East Asia (EA) and Australia (AU) (K).

KSHHDL_2018_v28n4_357_t0002.png 이미지

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