A New Algorithm for Sea Fog/Stratus Detection Using GMS-5 IR Data

Myoung Hwan Ahn, Eun Ha Sohn, Byong Jun Hwang

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

A new algorithm for the detection of fog/stratus over the ocean from the GMS-5 infrared (IR) channel data is presented. The new algorithm uses a clear-sky radiance composite map (CSCM) to compare the hourly observations of the IR radiance. The feasibility of the simple comparison is justified by the theoretical simulations of the fog effect on the measured radiance using a radiative transfer model. The simulation results show that the presence of fog can be detected provided the visibility is worse than 1 km and the background clear-sky radiances are accurate enough with known uncertainties. For the current study, an accurate CSCM is constructed using a modified spatial and temporal coherence method, which takes advantage of the high temporal resolution of the GMS-5 observations. The new algorithm is applied for the period of 10-12 May 1999, when heavy sea fog formed near the southwest coast of the Korean Peninsula. Comparisons of the fog/stratus index, defined as the difference between the measured and clear-sky brightness temperature, from the new algorithm to the results from other methods, such as the dual channel difference of NOAA/AVHRR and the earth albedo method, show a good agreement. The fog/stratus index also compares favorably with the ground observations of visibility and relative humidity. The general characteristics of the fog/stratus index and visibility are relatively well matched, although the relationship among the absolute values, the fog/stratus index, visibility, and relative humidity, varies with time. This variation is thought to be due to the variation of the atmospheric conditions and the characteristics of fog/stratus, which affect the derived fog/stratus index.

Original languageEnglish
Pages (from-to)899-913
Number of pages15
JournalAdvances in Atmospheric Sciences
Volume20
Issue number6
DOIs
Publication statusPublished - 1 Nov 2003
Externally publishedYes

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stratus
fog
radiance
clear sky
visibility
relative humidity
detection
sea
general characteristics
brightness temperature
AVHRR
simulation
radiative transfer
albedo
index

Cite this

Ahn, Myoung Hwan ; Sohn, Eun Ha ; Hwang, Byong Jun. / A New Algorithm for Sea Fog/Stratus Detection Using GMS-5 IR Data. In: Advances in Atmospheric Sciences. 2003 ; Vol. 20, No. 6. pp. 899-913.
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A New Algorithm for Sea Fog/Stratus Detection Using GMS-5 IR Data. / Ahn, Myoung Hwan; Sohn, Eun Ha; Hwang, Byong Jun.

In: Advances in Atmospheric Sciences, Vol. 20, No. 6, 01.11.2003, p. 899-913.

Research output: Contribution to journalArticle

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