• Journal of the Korean Association of Geographic Information Studies
• /
• v.1 no.1
• /
• pp.86-98
• /
• 1998

In order to provide an information as input data of possible storm surges in advance, the typhoon center and maximum wind position analysis scheme must be developed for the initialization of pressure and wind field.This study proposes a semi-automatical and objective analysis method and a procedure on a real time basis using the satellite TBB data of the GMS IR1, NOAA satellite CH4 and CH5, and shows the result of an experimental analysis. It includes a simple method of determining the parameters of the typhoon using minimum top temperature of the convective cloud near the inner eyewall. The method analyzing the isotropic cross sectional variation of TBB gradient from center to environment was developed to determine the center of Rmax of typhoon. This position of intense eyewall from typhoon center can be considered as the position of maximum wind. The results of estimation of typhoon center show very good agreement to the results of synoptic analysis. It is found that the Rmax is approximately 50-200km. From the comparison of the GMS and NOAA IR TBB data, it is found that the Rmax from NOAA data tends to be longer than those from GMS data.

• Journal of the Korean earth science society
• /
• v.23 no.1
• /
• pp.59-71
• /
• 2002

Theoretical models of radiative transfer are developed to simulate the 85 GHz brightness temperature (T85) observed by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) radiometer as a function of rain rate. These simulations are performed separately over regions of the convective and stratiform rain. TRMM Precipitation Radar (PR) observations are utilized to construct vertical profiles of hydrometeors in the regions. For a given rain rate, the extinction in 85 GHz due to hydrometeors above the freezing level is found to be relatively weak in the convective regions compared to that in the stratiform. The hydrometeor profile above the freezing level responsible for the weak extinction in convective regions is inferred from theoretical considerations to contain two layers: 1) a mixed (or mixed-phase) layer of 2 km thickness with mixed-phase particles, liquid drops and graupel above the freezing level, and 2) a layer of graupel extending from the top of the mixed layer to the cloud top. Strong extinction in the stratiform regions is inferred to result from slowly-falling, low-density ice aggregates (snow) above the freezing level. These theoretical results are consistent with the T85 measured by TMI, and with the rain rate deduced from PR for the convective and stratiform rain regions. On the basis of this study, the accuracy of the rain rate sensed by TMI is inferred to depend critically on the specification of the convective or stratiform nature of the rain.

• Korean Journal of Remote Sensing
• /
• v.30 no.4
• /
• pp.465-480
• /
• 2014

In this study, we analyzed the spatio-temporal variations of satellite imagery for the two heavy rainfall cases (21 September, 2010, 9 August, 2011) occurred in the Korean Peninsula. In general, the possibility of strong convection can be increased when the region with plenty of moisture at the lower layer overlapped with the boundary between dark and bright area in the water vapor imagery. And the merging of convective cells caused by the difference in the moving velocities of two cells resulted in the intensification of convective activity and rainfall intensity. The rainfall intensity is more closely linked with the minimum cloud top temperature than the mean cloud top temperature. Also the spatio-temporal variations of rainfall intensity are impacted by the existence of merging processes. The merging can be predicted by the animation of satellite imagery but earlier detection of convective cells is almost impossible by using the infrared and water vapor imagery.

• Proceedings of the KSRS Conference
• /
• 1999.11a
• /
• pp.325-329
• /
• 1999

The characteristic of East Asian summer monsoon is investigated using 8-year (March 1987-February 1995) - averaged monthly and 5-day mean 1 degree latitude-longitude gridded GMS high-cloud-amount data (HCA). An analysis of these data shows the convective zone (ITCZ) clouds which defined as the percentage of the total grid area covered by clouds with a cloud-top temperature below the 400 hPa-level climatological temperature. The HCA increased clearly over equatorial zone during December and January and 30-40 $^{\circ}$N during May and June. These HCA patterns are coincided with seasonal cycles of summer monsoon which is introduced in historical references. The relationship with the summer monsoon winds as climatological changing of wind direction is analyzed by ECMWF re-analysis 2.5-degree latitude-longitude grid surface data which is calculated with 8-year averaged from January 1987 to January 1995. In addition, the monsoon winds are showed by separated U, V-wind components far manifestation a tendency of onset and retreat data of seasonal monsoon.

• Journal of the Korean earth science society
• /
• v.41 no.3
• /
• pp.222-237
• /
• 2020

A heavy (93 mm hr^-1) rainfall event accompanied by lightning occurred over Gangneung in the Yeongdong region of South Korea on August 6, 2018. This study investigated the underlying mechanism for the heavy rainfall event by using COMS satellite cloud products, surface- and upper-level weather charts, ECMWF reanalysis data, and radiosonde data. The COMS satellite cloud products showed rainfall exceeding 10 mm hr^-1, with the lowest cloud-top temperature of approximately -65℃ and high cloud optical thickness of approximately 20-25. The radiosonde data showed the existence of strong vertical wind shear between the upper and lower cloud layers. Furthermore, a strong inversion in the equivalent potential temperature was observed at a pressure altitude of 700 hPa. In addition, there was a highly developed cloud layer at a height of 13 km, corresponding with the vertical analysis of the ECMWF data. This demonstrated the increased atmospheric instability induced by the vertical differences in equivalent potential temperature in the Yeongdong region. Consequently, cold, dry air was trapped within relatively warm, humid air in the upper atmosphere over the East Sea and adjacent Yeongdong region. This caused unstable atmospheric conditions that led to rapidly developing convective clouds and heavy rainfall over Gangneung.

• Journal of Korea Water Resources Association
• /
• v.31 no.5
• /
• pp.621-635
• /
• 1998

The feasibility of cloud seeding in Korea is presented from analyses of precipitation, cloud amount, satellite data, and upper air data. The daily mean precipitation over Dae-Kwan-Ryong is the largest(~4.5 mm/day), while the intensity of precipitation (amount of yearly rainfall divided by the frequency of rain days) over Southern area is above 14 mm/day, which shows the largest in Korea. Both the daily mean and the intensity of precipitation over Andong area are the smallest with values of ~2.7 mm/day and ~11 mm/day, respectively. In the meanwhile, the occurrence frequency of appropriate cloud top temperature (-10'~-30') for cloud seeding over the region has a large value (~130 days/year). The precipitation patterns of the region vary with wind direction and intensity calculated from 43 AWSs(Automatic Weather Station) and the additional 7 rain guages which were installed along Northern and Southern part of the Sobaek mountain. The Sc(Stratocumulus) cloud type over Andong is frequently observed, and Cirrus and Altostratus next. From the results, it is estimated that the feasibility of cloud seeding over the area would be high if a proper strategy of cloud seeding is set up. LCL (Lifting Condensation Level) and CCL (Convective Condensation Level) have the most frequency in 1000-950 hPa being occupied 4/9 of total analysis period and in 400-500 hPa, respectively, with both small variations from season to season. The correlation between vapor mixing ratio and CCL is the highest in Summer and the lowest in Winter. It means that the height of cumulus in Summer is high with an abundant water vapor but vice versa in Winter, and that the strategy of cloud seeding should be different with seasons.

• Korean Journal of Remote Sensing
• /
• v.35 no.1
• /
• pp.117-136
• /
• 2019

In this study, a hybrid-type of day fog detection algorithm (DFDA) was developed based on the optical and textural characteristics of fog top, using the Himawari-8 /Advanced Himawari Imager data. Supplementary data, such as temperatures of numerical weather prediction model and sea surface temperatures of operational sea surface temperature and sea ice analysis, were used for fog detection. And 10 minutes data from visibility meter from the Korea Meteorological Administration were used for a quantitative verification of the fog detection results. Normalized albedo of fog top was utilized to distinguish between fog and other objects such as clouds, land, and oceans. The normalized local standard deviation of the fog surface and temperature difference between fog top and air temperature were also assessed to separate the fog from low cloud. Initial threshold values (ITVs) for the fog detection elements were selected using hat-shaped threshold values through frequency distribution analysis of fog cases.And the ITVs were optimized through the iteration method in terms of maximization of POD and minimization of FAR. The visual inspection and a quantitative verification using a visibility meter showed that the DFDA successfully detected a wide range of fog. The quantitative verification in both training and verification cases, the average POD (FAR) was 0.75 (0.41) and 0.74 (0.46), respectively. However, sophistication of the threshold values of the detection elements, as well as utilization of other channel data are necessary as the fog detection levels vary for different fog cases(POD: 0.65-0.87, FAR: 0.30-0.53).

• Journal of the Korean earth science society
• /
• v.24 no.6
• /
• pp.558-567
• /
• 2003

The regional dependency of cloud-radiative forcing at the top of atmosphere is studied using ERBE (Earth Radiation Budget Experiment), ISCCP (International Satellite Cloud Climatology Project) and NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data for 60 months from January 1985 to December 1989 over tropical ocean. In the interannual time scale, the dependency of cloud-radiative forcing on the sea surface temperature over the equatorial eastern Pacific ocean is about 7.4Wm$^{-2}$K$^{-1}$ for longwave radiation and about -4.4Wm$^{-2}$K$^{-1}$ for shortwave radiation, respectively. This shows that the net cloud-radiative forcing due to the increase of sea surface temperature over the equatorial eastern Pacific ocean heats the atmosphere. But the dependency is reversed over tropical oceans with -3.4Wm$^{-2}$K$^{-1}$ for longwave and 1.9WmWm$^{-2}$K$^{-1}$ for shortwave radiation, indicating that the net cloud-radiative forcing cools the atmosphere over tropical oceans. In raw data including seasonal cycle, the dependency of cloud-radiative forcing over the equatorial eastern Pacific ocean is very similar to that in interannual time scale in both the magnitude and the sign. But the dependency of cloud-radiative forcing on the sea surface temperature over tropical oceans is about 0.2Wm$^{-2}$K$^{-1}$ for longwave and 2.7Wm$^{-2}$K$^{-1}$ for shortwave radiation, respectively. These results represent that the role of seasonal cycle on the cloud radiative forcing is gradually more important than role of interannual time scale as the ocean area is broadening from the tropical central Pacific to the tropical ocean.

• Atmosphere
• /
• v.20 no.2
• /
• pp.131-151
• /
• 2010

This study establishes a conceptual model to analyze heavy rainfall events in Korea using multi-functional transport satellite-1R satellite images. Three heavy rainfall episodes in two major synoptic types, such as synoptic low (SL) type and synoptic flow convergence (SC) type, are analyzed through a conceptual model procedure which proceeds on two steps: 1) conveyer belt model analysis to detect convective area, and 2) cloud top temperature analysis from black body temperature (TBB) data to distinguish convective cloud from stratiform cloud, and eventually estimate heavy rainfall area and intensity. Major synoptic patterns causing heavy rainfall are Changma, synoptic low approach, upper level low in the SL type, and upper level low, indirect effect of typhoon, convergence of tropical air in the SC type. The relationship between rainfall and TBBs in overall well resolved areas of heavy rainfall. The SC type tended to underestimate the intensity of heavy rainfall, but the analysis with the use of water vapor channel has improved the performance. The conceptual model improved a concrete utilization of images and data of satellite, as summarizing characteristics of major synoptic type causing heavy rainfall and composing an algorism to assess the area and intensity of heavy rainfall. The further assessment with various cases is required for the operational use.

• Atmosphere
• /
• v.22 no.4
• /
• pp.473-481
• /
• 2012

The objective methods estimating the radius of maximum wind (RMW) of tropical cyclones (TCs) are discussed using infraed (IR) imagery of geostationary satellite, and an alternative method is suggested that can estimate RMW in the TCs having eyes using IR imagery. The RMW-estimating methods are based on the characteristic structure of the eyewall of a tropical cyclone. RMW is dependent upon the radius of the eye and the distance from the center to the top of the most developed convective cloud. In order to test these methods, blackbody brightness temperature of Korean geostationary satellite, COMS (Communication, Ocean, and Meteorological Satellite) IR imagery are utilized in this study. The estimated RMWs are compared with surface winds of ASCAT (Advanced Scatterometer) of a polar orbiting satellite.