DOI QR코드

DOI QR Code

Development of a Retrieval Algorithm for Adjustment of Satellite-viewed Cloudiness

위성관측운량 보정을 위한 알고리즘의 개발

Son, Jiyoung;Lee, Yoon-Kyoung;Choi, Yong-Sang;Ok, Jung;Kim, Hye-Sil
손지영;이윤경;최용상;옥정;김혜실

  • Received : 2019.05.17
  • Accepted : 2019.06.03
  • Published : 2019.06.30

Abstract

The satellite-viewed cloudiness, a ratio of cloudy pixels to total pixels ($C_{sat,\;prev}$), inevitably differs from the "ground-viewed" cloudiness ($C_{grd}$) due to different viewpoints. Here we develop an algorithm to retrieve the satellite-viewed, but adjusted cloudiness to $C_{grd} (C_{sat,\;adj})$. The key process of the algorithm is to convert the cloudiness projected on the plane surface into the cloudiness on the celestial hemisphere from the observer. For this conversion, the supplementary satellite retrievals such as cloud detection and cloud top pressure are used as they provide locations of cloudy pixels and cloud base height information, respectively. The algorithm is tested for Himawari-8 level 1B data. The $C_{sat,\;adj}$ and $C_{sat,\;prev}$ are retrieved and validated with $C_{grd}$ of SYNOP station over Korea (22 stations) and China (724 stations) during only daytime for the first seven days of every month from July 2016 to June 2017. As results, the mean error of $C_{sat,\;adj}$ (0.61) is less that than that of $C_{sat,\;prev}$ (1.01). The percent of detection for 'Cloudy' scenario of $C_{sat,\;adj}$ (73%) is higher than that of $C_{sat,\;prev}$ (60%) The percent of correction, the accuracy, of $C_{sat,\;adj}$ is 61%, while that of $C_{sat,\;prev}$ is 55% for all seasons. For the December-January-February period when cloudy pixels are readily overestimated, the proportion of correction of $C_{sat,\;adj$ is 60%, while that of $C_{sat,\;prev}$ is 56%. Therefore, we conclude that the present algorithm can effectively get the satellite cloudiness near to the ground-viewed cloudiness.

Keywords

Satellite-viewed cloudiness;Ground-viewed cloudiness;Adjusted satellite-viewed cloudiness;Coordinate transformation

Acknowledgement

Grant : 정지궤도 기상 위성 지상국 개발, 구름 강수 분야 알고리즘/활용기술 개발

Supported by : 기상청 국가기상위성센터, 한국전자통신연구원(ETRI)