KIAPS 관측자료 처리시스템에서의 AMSU-A 위성자료 초기 전처리와 편향보정 모듈 개발

이시혜(Sihye Lee),김주혜(Ju-Hye Kim),강전호(Jeon-Ho Kang),전형욱(Hyoung-Wook Chun) 한국기상학회 2013 대기 Vol.23 No.4

As a part of the KIAPS Observation Processing System (KOPS), we have developed the modules of satellite radiance data pre-processing and quality control, which include observation operators to interpolate model state variables into radiances in observation space. AMSU-A (Advanced Microwave Sounding Unit-A) level-1d radiance data have been extracted using the BUFR (Binary Universal Form for the Representation of meteorological data) decoder and a first guess has been calculated with RTTOV (Radiative Transfer for TIROS Operational Vertical Sounder) version 10.2. For initial quality checks, the pixels contaminated by large amounts of cloud liquid water, heavy precipitation, and sea ice have been removed. Channels for assimilation, rejection, or monitoring have been respectively selected for different surface types since the errors from the skin temperature are caused by inaccurate surface emissivity. Correcting the bias caused by errors in the instruments and radiative transfer model is crucial in radiance data pre-processing. We have developed bias correction modules in two steps based on 30-day innovation statistics (observed radiance minus background; O-B). The scan bias correction has been calculated individually for each channel, satellite, and scan position. Then a multiple linear regression of the scan-bias-corrected innovations with several predictors has been employed to correct the airmass bias.

KIAPS 전지구 수치예보모델 시스템에서 SAPHIR 자료동화 효과

이시혜(Sihye Lee),전형욱(Hyoung-Wook Chun),송효종(Hyo-Jong Song) 한국기상학회 2018 대기 Vol.28 No.2

The KIAPS global model and data assimilation system were extended to assimilate brightness temperature from the Sondeur Atmosphérique du Profil d’Humidité Intertropicale par Radiométrie (SAPHIR) passive microwave water vapor sounder on board the Megha-Tropiques satellite. Quality control procedures were developed to assess the SAPHIR data quality for assimilating clear-sky observations over the ocean, and to characterize observation biases and errors. In the global cycle, additional assimilation of SAPHIR observation shows globally significant benefits for 1.5% reduction of the humidity root-mean-square difference (RMSD) against European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) analysis. The positive forecast impacts for the humidity and temperature in the experiment assimilating SAPHIR were predominant at later lead times between 96- and 168-hour. Even though its spatial coverage is confined to lower latitudes of 30°S-30°N and the observable variable is humidity, the assimilation of SAPHIR has a positive impact on the other variables over the mid-latitude domain. Verification showed a 3% reduction of the humidity RMSD with assimilating SAPHIR, and moreover temperature, zonal wind and surface pressure RMSDs were reduced up to 3%, 5% and 7% near the tropical and mid-latitude regions, respectively.

통계적 방법에 근거한 AMSU-A 복사자료의 전처리 및 편향보정

이시혜(Sihye Lee),김상일(Sangil Kim),전형욱(Hyoung-Wook Chun),김주혜(Ju-Hye Kim),강전호(Jeon-Ho Kang) 한국기상학회 2014 대기 Vol.24 No.4

As a part of the KIAPS (Korea Institute of Atmospheric Prediction Systems) Package for Observation Processing (KPOP), we have developed the modules for Advanced Microwave Sounding Unit-A (AMSU-A) pre-processing and its bias correction. The KPOP system calculates the airmass bias correction coefficients via the method of multiple linear regression in which the scan-corrected innovation and the thicknesses of 850~300, 200~50, 50~5, and 10~1 hPa are respectively used for dependent and independent variables. Among the four airmass predictors, the multicollinearity has been shown by the Variance Inflation Factor (VIF) that quantifies the severity of multicollinearity in a least square regression. To resolve the multicollinearity, we adopted simple linear regression and Principal Component Regression (PCR) to calculate the airmass bias correction coefficients and compared the results with those from the multiple linear regression. The analysis shows that the order of performances is multiple linear, principal component, and simple linear regressions. For bias correction for the AMSU-A channel 4 which is the most sensitive to the lower troposphere, the multiple linear regression with all four airmass predictors is superior to the simple linear regression with one airmass predictor of 850~300 hPa. The results of PCR with 95% accumulated variances accounted for eigenvalues showed the similar results of the multiple linear regression.

KIM 예보시스템에서의 Aeolus/ALADIN 수평시선 바람 자료동화

이시혜(Sihye Lee),권인혁(In-Hyuk Kwon),강전호(Jeon-Ho Kang),전형욱(Hyoung-Wook Chun),설경희(Kyung-Hee Seol),정한별(Han-Byeol Jeong),김원호(Won-Ho Kim) 한국기상학회 2022 대기 Vol.32 No.1

The Korean Integrated Model (KIM) forecast system was extended to assimilate Horizontal Line-Of-Sight (HLOS) wind observations from the Atmospheric Laser Doppler Instrument (ALADIN) on board the Atmospheric Dynamic Mission (ADM)-Aeolus satellite. Quality control procedures were developed to assess the HLOS wind data quality, and observation operators added to the KIM three-dimensional variational data assimilation system to support the new observed variables. In a global cycling experiment, assimilation of ALADIN observations led to reductions in average root-mean-square error of 2.1% and 1.3% for the zonal and meridional wind analyses when compared against European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) analyses. Even though the observable variable is wind, the assimilation of ALADIN observation had an overall positive impact on the analyses of other variables, such as temperature and specific humidity. As a result, the KIM 72-hour wind forecast fields were improved in the Southern Hemisphere poleward of 30 degrees.

PACDEX 캠페인 자료로 분석한 블랙카본을 포함한 축적모드 에어로솔의 구름응결핵 가능성

이시혜(Sihye Lee),김영성(Young Sung Ghim),김상우(Sang-Woo Kim),윤순창(Soon-Chang Yoon) 한국대기환경학회 2010 한국대기환경학회지 Vol.26 No.4

2011년 봄 황사시기 제주도 고산에서의 황사와 오염입자의 광흡수 기여도 산정

이시혜(Sihye Lee),김상우(Sang-Woo Kim),윤순창(Soon-Chang Yoon) 한국대기환경학회 2012 한국대기환경학회지 Vol.28 No.4

동아시아와 남아시아지역에서 관측된 에어러솔의 광흡수 특성 비교

이혜정(Hae-Jung Lee),김상우(Sang-Woo Kim),윤순창(Soon-Chang Yoon),이시혜(Sihye Lee),김지형(Ji-Hyoung Kim) 한국기상학회 2011 대기 Vol.21 No.3

In this study, we compared light-absorption properties of aerosols observed in East and South Asia from black carbon (BC) mass concentration, aerosol scattering (σ<SUB>s</SUB>) and absorption (σ<SUB>a</SUB><SUB></SUB>) coefficients measurements at four sites: Korea Climate Observatory-Gosan (KCO-G), Korea Climate Observatory-Anmyeon (KCO-A), Maldives Climate Observatory-Hanimaadhoo (MCO-H) and Nepal Climate Observatory-Pyramid (NCO-P). No significant seasonal variations of BC mass concentration, σ<SUB>s</SUB> and σ<SUB>a</SUB>, despite of wet removal of aerosols by precipitation in summer, were observed in East Asia, whereas dramatic changes of lightabsorbing aerosol properties were observed in South Asia between dry and wet monsoon periods. Although BC mass concentration in East Asia is generally higher than that observed in South Asia, BC mass concentration at MCO-H during winter dry monsoon is similar to that of East Asia. The observed solar absorption efficiency (α) at 550 nm, where α = σ<SUB>a</SUB>/(σ<SUB>s</SUB> + σ<SUB>a</SUB>), at KCO-G and KCO-A is higher than that in MCO-H due to large portions of BC emission from fossil fuel combustion. Interestingly, α at NCO-P is 0.14, which is two times great than that in MCO-H and is about 40% higher than that in East Asia, though BC mass concentration at NCO-P is the lowest among four sites. Consistently, the highest elemental carbon to sulphate ratio is found at NCO-P.

KIAPS 자료동화 시스템에서 AMSU-A의 품질검사 및 편향보정 반복기법에 관한 연구

정한별(Han-Byeol Jeong),전형욱(Hyoung-Wook Chun),이시혜(Sihye Lee) 한국기상학회 2019 대기 Vol.29 No.3

Bias correction (BC) and quality control (QC) are essential steps for the proper use of satellite observations in data assimilation (DA) system. BC should be calculated over quality controlled observation. And also QC should be performed for bias corrected observation. In the Korea Institute of Atmospheric Prediction Systems (KIAPS) Package for Observation Processing (KPOP), we adopted an adaptive BC method that calculates the BC coefficients with background at the analysis time rather than using static BC coefficients. In this study, we have developed an iterative QC-BC method for Advanced Microwave Sounding Unit-A (AMSU-A) to reduce the negative feedback from the interaction between BC and QC. The new iterative QC-BC is evaluated in the KIAPS 3-dimensional variational (3DVAR) DA cycle for January 2016. The iterative QC-BC method for AMSU-A shows globally significant benefits for error reduction of the temperature. The positive impacts for the temperature were predominant at latitudes of 30˚~90˚ of both hemispheres. Moreover, the background warm bias across the troposphere is decreased. Even though AMSU-A is mainly designed for atmospheric temperature sounding, the improvement of AMSU-A pre-processing module has a positive impact on the wind component over latitudes of 30˚S near upper-troposphere, respectively. Consequently, the 3-day-forecast-accuracy is improved about 1% for temperature and zonal wind in the troposphere.

위성기반 GK2A의 대기운동벡터와 Aeolus/ALADIN 바람 비교

신혜민 ( Hyemin Shin ),안명환 ( Myoung-hwan Ahn ),김지수 ( Jisoo Kim ),이시혜 ( Sihye Lee ),이병일 ( Byung-Il Lee ) 대한원격탐사학회 2021 大韓遠隔探査學會誌 Vol.37 No.6

세계 최초 능동형 라이더 센서 Atmospheric Laser Doppler Instrument (ALADIN)의 바람 자료와 한국형 수치예보모델에 바람 자료로 활용되고 있는 Geostationary Korea Multi Purpose Satellite 2A (GK2A)의 대기운동벡터의 자료를 비교함으로써 두 위성의 바람 자료의 특징을 분석하였다. 2019년 9월부터 20220년 8월 1년의 자료를 ALADIN의 미(Mie)채널과 GK2A 적외채널에 대하여 비교한 결과 수집된 자료는 177,681개이며 평균 제곱근 오차(Root Mean Square Error; RMSE)는 3.73 m/s, 상관계수는 0.98이다. 상세한 분석을 위해 위도와 고도를 고려하여 비교한 결과, 대부분의 위도에서 표준화된 평균 제곱근 오차(Normalized Root Mean Squared Error; NRMSE)가 0.2~0.3으로 두 바람 자료가 일치하지만 상층, 중층의 경우 저위도지역에서, 하층의 경우 남반구 특정 위도(30°S-15°S)에서 0.4 이상으로 큰 값을 가진다. 이러한 결과는 계절에 상관없이 수증기채널, 가시채널에서도 동일하게 나타나며 채널 별 특징과 계절별 특징은 두드러지게 나타나지 않는다. 두 바람 자료 간에 차이가 큰 위도 영역에 대하여 구름의 분포를 확인해본 결과, 대기운동벡터의 고도 할당 정확도를 낮출 수 있는 권운 이나 적운이 다른 위도에 비해 더 많이 분포하고 있다. 이러한 특성에 따라, 정확한 고도 할당이 어려워 대기운동벡터의 오차가 크게 나타나는 남반구와 저위도 영역에서 ALADIN 바람 자료는 기존 대기운동벡터의 바람 정보를 보완함으로써 수치예보모델에 긍정적인 영향을 미칠 수 있음을 제시한다. This research aims to provide the characteristics of the world's first active lidar sensor Atmospheric Laser Doppler Instrument (ALADIN) wind data and Geostationary Korea Multi Purpose Satellite 2A (GK2A) Atmospheric Motion Vector (AMV) data by comparing two wind data. As a result of comparing the data from September 2019 to August 1, 2020, The total number of collocated data for the AMV (using IR channel) and Mie channel ALADIN data is 177,681 which gives the Root Mean Square Error (RMSE) of 3.73 m/s and the correlation coefficient is 0.98. For a more detailed analysis, Comparison result considering altitude and latitude, the Normalized Root Mean Squared Error (NRMSE) is 0.2-0.3 at most latitude bands. However, the upper and middle layers in the lower latitudes and the lower layer in the southern hemispheric are larger than 0.4 at specific latitudes. These results are the same for the water vapor channel and the visible channel regardless of the season, and the channel-specific and seasonal characteristics do not appear prominently. Furthermore, as a result of analyzing the distribution of clouds in the latitude band with a large difference between the two wind data, Cirrus or cumulus clouds, which can lower the accuracy of height assignment of AMV, are distributed more than at other latitude bands. Accordingly, it is suggested that ALADIN wind data in the southern hemisphere and low latitude band, where the error of the AMV is large, can have a positive effect on the numerical forecast model.