Arctic Fog Detection Using Infrared Spectral Measurements

Abstract

The rapid increase in open-water surface area in the Arctic, resulting from sea ice melting during the summer likely as a result of global warming, may lead to an increase in fog [defined as a cloud with a base height below 1000 ft (~304 m)], which may imperil ships and small aircraft transportation in the region. There is a need for monitoring fog formation over the Arctic. Given that ground-based observations of fog over Arctic open water are very sparse, satellite observations may become the most effective way for Arctic fog monitoring. We developed a fog detection algorithm using the temperature difference between the cloud top and the surface, called ∂ T in this work. A fog event is said to be detected if ∂ T is greater than a threshold, which is typically between −6 and −12 K, depending on the time of the day (day or night) and the surface types (open water or sea ice). We applied this method to the coastal regions of Chukchi Sea and Beaufort Sea near Barrow, Alaska (now known as Utqiaġvik), during the months of March–October. Training with satellite observations between 2007 and 2014 over this region, the ∂ T method can detect Arctic fog with an optimal probability of detection (POD) between 74% and 90% and false alarm rate (FAR) between 5% and 17%. These statistics are validated with data between 2015 and 2016 and are shown to be robust from one subperiod to another.

Hydroxymethanesulfonate (HMS) Formation during Summertime Fog in an Arctic Oil Field

“…This demonstrates that fog often formed on a regional scale, covering the oil fields and surrounding region of the North Slope of Alaska. This is in agreement with previous work showing that fog can be widespread across the Beaufort Sea and is most abundant in the Arctic from June to September …”

“…The formation, dissipation, and droplet size distribution of Arctic fog, as well as aerosol interactions, have previously been investigated, 53−55 with fog frequently observed on the North Slope of Alaska during summertime. 56,57 As the third largest oil field in North America, the North Slope of Alaska oil fields cover ∼14000 km 2 . In this study, local combustion emissions 46,48,50,51 and fog processing were investigated using an aerosol time-of-flight mass spectrometer (ATOFMS) 58 during August and September 2016 at Oliktok Point, AK, within the oil fields.…”

“…In the Arctic, there is growing attention on the significance of local combustion emissions, including from large oil fields across the region. − However, few measurements of atmospheric trace gases and aerosols within Arctic oil fields exist, − with none, to the best of our knowledge, examining subsequent aqueous-phase processing. The formation, dissipation, and droplet size distribution of Arctic fog, as well as aerosol interactions, have previously been investigated, − with fog frequently observed on the North Slope of Alaska during summertime. , As the third largest oil field in North America, the North Slope of Alaska oil fields cover ∼14000 km 2 . In this study, local combustion emissions ,,, and fog processing were investigated using an aerosol time-of-flight mass spectrometer (ATOFMS) during August and September 2016 at Oliktok Point, AK, within the oil fields.…”

Interannual Variability in Summertime Sea Fog Over the Northern Yellow Sea and Its Association With the Local Sea Surface Temperature

“…Thus, the vertical structure of fog/low‐level clouds from independent observations away from coast is still desirable. In addition, previous studies used CALIPSO to detect sea fog or validate their results of algorithms of sea fog retrievals (Shin & Kim, 2018; Wu & Li, 2014; Wu et al., 2015; Yi et al., 2019).…”

“…Although previous studies have concentrated on the climatic features and synoptic boundary processes of the YS fog, fewer studies investigate its interannual variability partly due to the difficulty in distinguishing fog from low‐level clouds in satellite observations (e.g., Gao et al., 2009; Norris & Leovy, 1994; Yi et al., 2015; Yi et al., 2019). A few studies on interannual variation in sea fog rely on the coastal observations and sporadic ship reports (Bai et al., 2010; Garreaud et al., 2008; Long et al., 2016).…”