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2026 Vol.59, Issue 1 Preview Page

Research Article / 우수학생논문상

Evaluating the applicability of Multi-satellite based soil moisture products in Korea

국내에서 다중 위성 기반 토양수분 산출물의 적용성 평가

Sungjin Hana
,
Kijin Parkb
,
Jongmin Parkc
,
Byungkyu Kimd*
한 성진a
,
박 기진b
,
박 종민c
,
김 병규d*
aUndergraduate Student, Department of Environmental Engineering, Korea National University of Transportation, Chungju, Korea
b Master Student, Department of Environmental Engineering, Korea National University of Transportation, Chungju, Korea
cAssistant Professor, Department of Environmental Engineering, Korea National University of Transportation, Chungju, Korea
dSenior Researcher, Advanced Railroad Civil Engineering Division, Korea Railroad Research Institute, Uiwang, Korea
a국립한국교통대학교 환경공학전공 학사과정
b국립한국교통대학교 환경공학과 석사과정
c국립한국교통대학교 환경공학전공 조교수
d한국철도기술연구원 첨단궤도토목본부 선임연구원
*Corresponding Author
31 January 2026. pp. 39-49
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Abstract

This study quantitatively evaluated surface soil moisture from the advanced scatterometer (ASCAT) (C-band) and soil moisture active passive (SMAP) Level-4 (L-band) against in-situ observations at seven sites across Korea, focusing on seasonal behavior and hydrologic state (dry/wet). Excluding winter season, we assessed correlation coefficient (R), Bias, and root mean square error (RMSE) for spring, summer, and autumn, and classified years as dry or wet based on the normal mean precipitation. Overall, SMAP soil moisture exhibited lower Bias and RMSE than ASCAT (RMSE: 0.08~0.15 vs. 0.10~0.20 m3 m-3), which is resulted from the higher vegetation penetration of L-band and improved temporal representativeness of the 3-hourly assimilation output. Seasonally, both sensors showed higher R in summer as variability increased due to the monsoon and convective rainfall (ASCAT: 0.57~0.80; SMAP: 0.40~0.78). However, at sites adjacent to airports and military airfields, potential radio-frequency interference in the SMAP L-band, and at sites near rivers and reservoirs, mixed land–water surfaces within the same pixel, amplified errors. In orchards and irrigated areas, canopy structure and irrigation limited SMAP’s ability to capture seasonal variability. During wet periods, many sites exhibited increases in R along with rises in Bias and RMSE, likely due to the nonlinearity of satellite-based products near saturation, post-rainfall surface heterogeneity, and increased vegetation water content.

Keywords
Soil moisture
ASCAT
SMAP
Seasonal analysis
Hydrological conditions

본 연구는 국내 7개 관측소를 대상으로 C-band Advanced scatterometer (ASCAT)와 L-band Soil moisture active passive (SMAP) 표층 토양수분을 지상관측과 비교하여 계절성과 수문상태(건조/습윤)에 따른 성능 차이를 정량 평가하였다. 겨울을 제외한 봄·여름·가을 자료에 대해 correlation coefficient (R), Bias, root mean square error (RMSE) 지표를 사용하고, 지점별 정상 연평균 강수량을 기준으로 각각의 연도를 건조/습윤으로 구분하였다. 그 결과 SMAP 토양수분은 전반적으로 Bias와 RMSE가 낮게 나타났으며(RMSE:0.08~0.15 vs. 0.10~0.20 m3 m-3), 이는 L-band의 높은 식생 투과성과 3시간 간격 동화 산출의 시간 대표성 개선 효과에 기인한 것으로 해석된다. 계절적 성능은 두 센서 모두 여름철 장마·대류성 강우로 인해 변동폭이 증가함에 따라 R이 상승(ASCAT 0.57~0.80, SMAP: 0.40~0.78)했다. 단, 일부 공항·군공항 인접 지점에서 SMAP L-band의 전파간섭 가능성, 하천·저수지 인접 지점에서는 동일 픽셀 내 지표-수체 혼재로 오차가 확대되었고, 과수원·관개지에서는 캐노피 구조와 관개의 영향으로 SMAP의 계절 변동성 모의가 제한되었다. 습윤기에는 다수 지점에서 R이 증가하는 동시에 Bias 및 RMSE도 증가하였으며, 이는 포화 근접 시 위성 기반 산출물의 비선형성, 강우 직후 지표 이질성, 식생 수분함량 증가가 주요 원인으로 판단된다.

키워드
토양수분
ASCAT
SMAP
계절적 평가
습윤/건조 평가
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Information
  • Publisher :KOREA WATER RESOURECES ASSOCIATION
  • Publisher(Ko) :한국수자원학회
  • Journal Title :Journal of Korea Water Resources Association
  • Journal Title(Ko) :한국수자원학회 논문집
  • Volume : 59
  • No :1
  • Pages :39-49
  • Received Date : 2025-10-20
  • Revised Date : 2025-11-07
  • Accepted Date : 2025-11-07
  • DOI :https://doi.org/10.3741/JKWRA.2026.59.1.39
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