Automatic sea fog detection over Chinese adjacent oceans using Terra/MODIS data

作者：Wu, Xiaojing; Li, Sanmei^*

来源：International Journal of Remote Sensing, 2014, 35(21): 7430-7457.

DOI：10.1080/01431161.2014.968685

• YELLOW SEA
• IR DATA
• FOG/STRATUS
• STRATUS
• CLOUDS
• MODIS

Sea fog is a problematic weather phenomenon for marine transportation and navigation. Lacking ground observations, sea fog monitoring mainly depends on meteorological and environmental satellites because they provide large swaths of data with good spatial and temporal resolution. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites provides several new features for sea fog detection because of the more available channels.
In addition to the traditional variable-dual channel difference (DCDIR), which is widely used to detect sea fog and stratus clouds at night, this study uses and analyses several other variables including NDSI (normalized difference snow index), BTDback (brightness temperature difference in the thermal infrared channel between a sea fog/stratus cloud pixel and nearby clear-sky ocean surface), NWVI (normalized difference near-infrared water vapour index) and D_NWVI (NWVI difference between a possible sea fog/stratus cloud pixel and nearby clear-sky ocean surface), for all seasons. BTDback, NWVI, and D_NWVI show outstanding ability to discriminate between sea fog and stratus clouds. Automatic sea fog detection algorithms are developed using these variables for both daytime and night time with Terra/MODIS data based on a threshold scheme. During development of the algorithms, a series of data processes are also considered to maintain stable performance of the algorithms over wide areas and in all seasons.
The algorithms are applied to Terra/MODIS data at a semi-operational mode from 2007 to 2013 and show promising results. Validation with data from field campaigns, one buoy station with good maintenance, 18 weather stations, and CALIOP (Cloud Aerosol Lidar with Orthogonal Polarization)/CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) demonstrates the accuracy of the algorithms. The sea fog detection results are highly consistent with fog observations from the field campaign data. The validation with the buoy station data shows an overall accuracy of 90% under all weather conditions, an accuracy of 86% during foggy weather condition, and a KSS (Hanssen-Kuiper Skill Score) of 0.81. The validation with two-year data from 18 weather stations and CALIOP/CALIPSO over the Bohai Sea and Yellow Sea shows accuracy of 76.3% and 77.9%, respectively. The promising results indicate high probability of applying the algorithms in operational systems over the oceans adjacent to China or even wider oceans using Terra/MODIS data.

• 出版日期2014
• 单位国家卫星气象中心; 中国科学院大学; 中国科学院大气物理研究所