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 observatio...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.展开更多
The GMS-5 infrared cloud imagery for two yearly first raining seasons in 1998 and 1999 are used to study the relationship between brightness temperature and surface rain rates. The result shows that it is likely to ha...The GMS-5 infrared cloud imagery for two yearly first raining seasons in 1998 and 1999 are used to study the relationship between brightness temperature and surface rain rates. The result shows that it is likely to have large probability of heavy precipitation with the decrease of brightness temperature and the gradual increase of rainfall intensity; for areas of low temperature, the brightness temperature is better determined for atmosphere above rain gauge stations with multiple points sampling than with single point one; for the yearly first raining season, the threshold brightness temperature is set at 4.6℃ for indication of heavy precipitation in the Fujian area.展开更多
The retrieved results in this paper by GMS-5/VISSR thermal infrared data with single time/dual channel Split-Window Algorithm reveal the characteristics of diurnal and seasonal variation of clear-sky land surface temp...The retrieved results in this paper by GMS-5/VISSR thermal infrared data with single time/dual channel Split-Window Algorithm reveal the characteristics of diurnal and seasonal variation of clear-sky land surface temperature （LST） of several representative land surface types in China, including Tarim Basin, QinghaiTibetan Plateau, Hunshandake Sands, North China Plain, and South China. The seasonal variation of clear-sky LST in above areas varies distinctly for the different surface albedo, soil water content, and the extent of influence by solar radiation. The monthly average diurnal ranges of LST have two peaks and two valleys in one year. The characteristics of LST in most land of East Asia and that of sea surface temperature （SST） in the south of Taiwan Strait and the Yellow Sea are also analyzed as comparison. Tarim Basin and Hunshandake Sands have not only considerable LST diurnal cycle but also remarkable seasonal variation. In 2000, the maximum monthly average diurnal ranges of LST in both areas are over 30 K, and the annual range in Hunshadake Sands reaches 58.50 K. Seasonal variation of LST in the Qinghai-Tibetan Plateau is less than those in East Asia, Tarim Basin, and Hunshandake Sands. However, the maximum diurnal range exists in this area. The yearly average diurnal range is 28.05 K in the Qinghai-Tibetan Plateau in 2000. The characteristics of diurnal, seasonal, and annual variation from 1998 to 2000 are also shown in this research. All the results will be valuable to the research of climate change, radiation balance, and estimation for the change of land surface types.展开更多
基金This work was supported by the Basic Research Project (Satellite Data Processing Technique) of METRI
文摘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.
基金Scientific Research project of Fujian Meteorological Bureau for 1998
文摘The GMS-5 infrared cloud imagery for two yearly first raining seasons in 1998 and 1999 are used to study the relationship between brightness temperature and surface rain rates. The result shows that it is likely to have large probability of heavy precipitation with the decrease of brightness temperature and the gradual increase of rainfall intensity; for areas of low temperature, the brightness temperature is better determined for atmosphere above rain gauge stations with multiple points sampling than with single point one; for the yearly first raining season, the threshold brightness temperature is set at 4.6℃ for indication of heavy precipitation in the Fujian area.
基金Supported jointly by the National Facilities and Information Infrastructure for Science and Technology Project (2005DKA31700) and the National Nature Science Foundation of China (Nos.40333034 and 49790020).
文摘The retrieved results in this paper by GMS-5/VISSR thermal infrared data with single time/dual channel Split-Window Algorithm reveal the characteristics of diurnal and seasonal variation of clear-sky land surface temperature （LST） of several representative land surface types in China, including Tarim Basin, QinghaiTibetan Plateau, Hunshandake Sands, North China Plain, and South China. The seasonal variation of clear-sky LST in above areas varies distinctly for the different surface albedo, soil water content, and the extent of influence by solar radiation. The monthly average diurnal ranges of LST have two peaks and two valleys in one year. The characteristics of LST in most land of East Asia and that of sea surface temperature （SST） in the south of Taiwan Strait and the Yellow Sea are also analyzed as comparison. Tarim Basin and Hunshandake Sands have not only considerable LST diurnal cycle but also remarkable seasonal variation. In 2000, the maximum monthly average diurnal ranges of LST in both areas are over 30 K, and the annual range in Hunshadake Sands reaches 58.50 K. Seasonal variation of LST in the Qinghai-Tibetan Plateau is less than those in East Asia, Tarim Basin, and Hunshandake Sands. However, the maximum diurnal range exists in this area. The yearly average diurnal range is 28.05 K in the Qinghai-Tibetan Plateau in 2000. The characteristics of diurnal, seasonal, and annual variation from 1998 to 2000 are also shown in this research. All the results will be valuable to the research of climate change, radiation balance, and estimation for the change of land surface types.
