Abstract
Abstract. Dawn and dusk time is the high frequency period of sea fog occurrence, which is very important for all-day sea fog remote sensing detection. Most polar orbit satellites are limited by time resolution and transit time, and can not detect sea fog at dawn and dusk. Based on the Himawari-8 geostationary satellite data and the analysis of the spectral characteristics of sea fog at dawn and dusk, this paper determines the variation law of the reflectivity and brightness temperature of sea fog at dawn and dusk, chooses sensitive bands, sets the detection index of sea fog and its corresponding dynamic threshold, and realizes the detection of sea fog at dawn and dusk. The case study results indicate that our dynamic threshold algorithm can effectively detect the sea fog at dawn and dusk.
Highlights
Sea fog is a condensation phenomenon occurring in the lower atmosphere of the sea or coastal areas under the influence of the ocean
As remote sensing satellite technology has the advantages of fast information updating, wide coverage and low cost, it has become an important means of sea fog detection (Zhang et al, 2018).At present, the research of sea fog remote sensing detection technology mainly focuses on daytime and night-time, while the research of dawn and dusk time is relatively few
By comparing the detection results with the visibility data of coastal meteorological stations, it can be found that the algorithm can more accurately identify the sea fog in the Yellow Sea and Bohai Sea at dawn and dusk, and has certain accuracy, but there are some errors: (1) At 10:00 UTC, the visibility of Qingdao meteorological station is far greater than 1km, indicating that there is no sea fog near it
Summary
Sea fog is a condensation phenomenon occurring in the lower atmosphere of the sea or coastal areas under the influence of the ocean. As remote sensing satellite technology has the advantages of fast information updating, wide coverage and low cost, it has become an important means of sea fog detection (Zhang et al, 2018).At present, the research of sea fog remote sensing detection technology mainly focuses on daytime and night-time, while the research of dawn and dusk time is relatively few. Sea fog mostly occurs in the dawn (Jung-Hyun et al, 2019; Tang et al, 2012; Zhang et al, 2015), and the spectral characteristics of sea fog in this period are different from those in daytime and night-time. In order to realize the real-time monitoring of sea fog and provide data support for marine economic and military activities, the research of sea fog detection at dawn and dusk is indispensable and of great significance. Based on the analysis of the spectral characteristics of sea fog samples at dawn and dusk, a dynamic threshold method is constructed to detect sea fog at dawn and dusk in the Yellow Sea and Bohai Sea
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