Optical Thickness and Effective Radius Retrievals of Low Stratus and Fog from MTSAT Daytime Data as a Prerequisite for Yellow Sea Fog Detection

Li Yi,Xiaomeng Shi,Suping Zhang,Boris Thies,Jörg Bendix

doi:10.3390/rs8010008

Abstract

Operational nowcasting techniques for sea fog over the Yellow Sea rely on data from weather satellites because ground-based observations are hardly available. While there are several algorithms for detecting low stratus (LST) that are applicable to geostationary weather satellite data, sea fog retrieval is more complicated. These schemes mostly need ancillary data such as Cloud Optical Thickness (COT) and Droplet Effective Radius (DER). To retrieve the necessary parameters for sea fog detection over the Yellow Sea, the Comprehensive Analysis Program for Cloud Optical Measurement (CAPCOM) scheme developed by Kawamoto et al. (2001) was adapted to the Japanese Multifunctional Transport Satellites (MTSAT) system-Japanese Advanced Meteorological Imager (JAMI). COT and DER values were then retrieved for 64 cases over the Yellow Sea (= 85,000 LST pixels) and compared with the COT and DER products from the MYD06/MOD06, CAPCOM-MODIS (Moderate Resolution Imaging Spectroradiometer) and CloudSat (cloud radar). Results showed that the COT and DER values retrieved from JAMI were satisfactory. The MTSAT-2 JAMI data delivered better COT values than the MTSAT-1R JAMI data, due to the re-calibration of MTSAT-2 JAMI’s visible (VIS) band in 2011. Similarly, improvements were seen in DER retrieval, even though the VIS re-calibration primarily affects COT retrieval. By comparing the difference in stratus thickness calculated by MTSAT-1R and MTSAT-2, the COT and DER retrieved from MTSAT-2 JAMI can be used in ground fog retrieval schemes. These values exhibit less bias, especially in cases involving high cloud top and thin cloud thickness. Both the COT and DER retrievals from MTSAT-2 JAMI offer potential as reliable parameters for Yellow Sea fog detection.

Highlights

A specific manifestation of low stratus (LST), fog plays a key role in the Earth’s climate system [1]through modifying the radiation balance [2]
Results showed that the Cloud Optical Thickness (COT) and Droplet Effective Radius (DER) values retrieved from Japanese Advanced Meteorological Imager (JAMI) were satisfactory
By comparing the difference in stratus thickness calculated by Multifunctional Transport Satellites (MTSAT)-1R and MTSAT-2, the COT and DER retrieved from MTSAT-2

Summary

Introduction

A specific manifestation of low stratus (LST), fog plays a key role in the Earth’s climate system [1]through modifying the radiation balance [2]. We used an inverse method to obtain COT and (3.74 DERμm), from CAPCOM (Figure 3).the. This required following steps:and channel and channel 4 (10.8 μm) of NOAA. Initial estimates of COT and DER, sounding data, infrared wavelength brightness microphysics at the global and regional levels, respectively. We used an inverse method to obtain temperature (Tir), and angular variables COT and DER from CAPCOM (Figure 3) This required the following three steps: azimuth angle, RAZ) to simulate radiance reflected upwards by clouds in the visible (L0vis, about (1) Initial estimates of COT and DER, sounding data, infrared wavelength brightness temperature. 0.7 μm) and mid-infrared (L0mir, about 3.9 μm) channels with a radiative transfer model, which (Tir), and angular variables

Objectives

Results

Discussion

Conclusion