Structure and Evolution of a Convective System with Bow Echo Associated with Terrain on Jeju Island, Korea (*)

Kang, Y.,Jeong, J.-H.,You, C.-H.,Lee, D.-I. Meteorological Society of Japan 2018 Journal of the Meteorological Society of Japan SER Vol.96 No.5

On the Elevation Dependency of Present-day Climate and Future Change over Korea from a High Resolution Regional Climate Simulation

IM, Eun-Soon,AHN, Joong-Bae Meteorological Society of Japan 2011 Journal of the Meteorological Society of Japan Vol.89 No.1

<P>This study investigates the elevation dependency of the present-day climate and future climate change in temperature and precipitation over Korea. A dynamically downscaled fine-scale climate simulation (20 km) shows reasonable agreement with two types of observations maintained by the Korea Meteorological Administration. The model exactly captures the strong relationship between the elevation and local climatology as seen in observed temperature and precipitation patterns. The behavior of the elevation dependency shown by the present-day climate simulation is also appeared in the climate change signal. The warming amplification is highly correlated with elevation. The warming is more pronounced at higher elevations than at lower elevations during winter, and maximum warming occurs at minimum temperature, showing an asymmetric response between minimum and maximum temperature. A noticeable differential rate of winter warming in response to the elevation can be explained by the snow-albedo feedback. Precipitation and snow changes also show the relevant topographical modulation under global warming. This study clearly demonstrates the importance of a refined topography for improving the accuracy of the local climatology and suitably reflecting the altitudinal distribution.</P>

An Evaluation of a Mass-Flux Cumulus Parameterization Scheme in the KMA Global Forecast System

PARK, Hoon,HONG, Song-You Meteorological Society of Japan 2007 Journal of the Meteorological Society of Japan SER Vol.85 No.2

<P>A mass-flux type cumulus parameterization scheme is evaluated in the Korea Meteorological Administration (KMA)’s Global Data Assimilation and Prediction System (GDAPS). Two sets of parallel assimilation runs, with a horizontal resolution corresponding to the spectral truncation of T213, approximately 50 km, are designed, one with the operational Kuo convection scheme, and another with a simplified Arakawa-Schubert (SAS) convection scheme, for the month of July 2001, which was a typical summer monsoon period in Korea. An additional sensitivity experiment, that excludes the moist downdrafts in the SAS scheme, is conducted. A 10-day forecast cycle is run, within a data assimilation window, beginning at every 1200 UTC in July 2001. A heavy rainfall event, that occurred in the Korean peninsula on 14-15 July 2001, is investigated in detail.For the heavy rainfall case, the SAS scheme tends to reduce the precipitation amount, as compared to the Kuo scheme. It is found that the exclusion of moist downdrafts in the SAS scheme, increases drying and heating rates, resulting in enhanced rainfall, as shown in the Kuo scheme. The monthly verification demonstrates that the systematic warm bias in the lower troposphere in the operational model is nearly absent when the SAS scheme is employed. In terms of statistical measure of the skill for the predicted sea-level pressure, and that for the upper level patterns, the experiment with the SAS (Kuo) scheme out-performs in the northern (southern) hemisphere. In the case of precipitation forecasts, the SAS scheme effectively corrects the spurious excessive precipitation over the tropical land area, due to the inclusion of moist downdrafts. However, the reduction in precipitation in the SAS scheme, deteriorates the forecast skill for high precipitation categories.</P>

More Absorbing Dust Aerosol Inferred from Sky Radiometer Measurements at Anmyeon, Korea

SOHN, Byung-Ju,NAKAJIMA, Teruyuk,CHUN, Hyoung-Wook,AOKI, Kazuma Meteorological Society of Japan 2007 Journal of the Meteorological Society of Japan SER Vol.85 No.6

<P>In this paper we present evidence that Asian dusts can become more absorbing aerosols when mixed with pollutants. Spectral direct/diffuse solar radiations were measured on April 7, 2000 at Anmyeon-Do, Korea, when a narrow and heavy dust band moved through the Anmyeon measurement site. Lowest SSA values (about 0.91) are found within the dust band, while comparatively high values (up to 0.97) are found outside over the non-dust area at about 300 km away from the dust band. Considering that the air masses passed through the Anmyeon site took nearly the same path through the Beijing area, obtained results strongly suggest that there may be interactions between air pollutants and mineral dust aerosols that lead to the decreased SSA and thus to the more solar absorption by dust aerosols. In other words, Asian dusts tend to become darkened after mixing with pollutant particles produced over the industrial /urban area of China.</P>

Satellite Assessment of Divergent Water Vapor Transport from NCEP, ERA40, and JRA25 Reanalyses over the Asian Summer Monsoon Region

PARK, Seong-Chan,SOHN, Byung-Ju,WANG, Bin Meteorological Society of Japan 2007 Journal of the Meteorological Society of Japan SER Vol.85 No.5

<P>The divergent component of water vapor transports was constructed using evaporation, precipitation, and total precipitable water estimated from the Special Sensor Microwave Imager (SSM/I). The SSM/I moisture budget parameters were then compared with those from the National Centers for Environmental Prediction (NCEP), the European Centre for Medium-Range Weather Forecasts (ECMWF) 40-year Reanalysis (ERA40), and the Japanese 25-year Reanalysis Project (JRA25) data over the Asian monsoon region for the May to September (MJJAS) period from 1988 to 2000.The climatology of SSM/I water vapor transports clearly indicates three major water vapor sources for the Asian monsoon, i.e., the subtropical Indian Ocean and Pacific Ocean in the Southern Hemisphere, and the North Pacific Ocean. In contrast, sinks are located in the Asian summer monsoon trough, the equatorial convective zones over the Indian and western Pacific Oceans, and over the East Asian monsoon region from the northern tip of Philippine Sea to the Kuroshio extension region. These sources and sinks are linked to well-known large-scale rotational circulation features, i.e., the cross-equatorial flow associated with monsoon circulation over the Indian Ocean, the anticyclonic circulation along the western periphery of the western North Pacific High, and the cross-equatorial flow north of New Guinea. In conjunction with the fluctuation of these sources and sinks, the northward propagating climatological intraseasonal oscillations in water vapor flux convergence are evident in the South and East Asian monsoon regions in the SSM/I data.From the comparison of water budget parameters of NCEP, ERA40, and JRA25 reanalysis with SSM/I-derived features, we found that the general features of all three reanalyses are in good agreement with those from SSM/I; however, the magnitudes of water vapor transports are comparatively weaker in all three reanalyses than what SSM/I measurements suggested. In addition, much weaker water vapor transports in three reanalyses are found in the intraseasonal oscillation signals with less distinct patterns, compared to what are inferred from the SSM/I measurements.</P>

On the Critical Separation Distance of Binary Vortices in a Nondivergent Barotropic Atmosphere

SHIN, Seol-Eun,HAN, Ji-Young,BAIK, Jong-Jin Meteorological Society of Japan 2006 Journal of the Meteorological Society of Japan Vol.84 No.5

<P>The motion of binary cyclonic vortices with equal structure and strength in no environmental flow is investigated with a focus on what determines their merger or separation. For this, proposals in previous studies on the critical separation distance of binary vortices are validated using a nondivergent barotropic model on an <I>f</I>-plane.Results from numerical experiments indicate that the sign of the initial relative vorticity in the mid-region between two vortices largely determines their merger or separation. This is consistent with the proposal of Falkovich et al. When the initial relative vorticity in the mid-region between two vortices is negative, the two vortices separate. However, it is found that an initial positive relative vorticity between the two vortices does not guarantee their merger. Only when the initial positive relative vorticity exceeds a certain threshold value, the two vonices merge. Based upon the results of numerical experiments, it is suggested that the critical separation distance of binary vortices is slightly smaller than twice the radius at which the relative vorticity of one vortex becomes zero. The merger or separation of binary vortices can be conceptually explained by the advection of the symmetric relative vorticity of one vortex by the symmetric tangential flow of the other vortex. This relative vorticity advection produces vorticity anomalies with different magnitudes to the north and south of each vortex and results in net eastward or westward secondary flow near its center when the two vortices are initially placed in the east-west direction.</P>

Ground-Based Mie-Scattering Lidar Measurements of Aerosol Extinction Profiles during ABC-EAREX 2005: Comparisons of Instruments and Inversion Algorithms

YOON, Soon-Chang,KIM, Sang-Woo,KIM, Man-Hae,SHIMIZU, Atsushi,SUGIMOTO, Nobuo Meteorological Society of Japan 2008 Journal of the Meteorological Society of Japan Vol.86 No.2

<P>An intercomparison study of ground-based Mie-scattering lidar systems was held at Gosan, Korea during ABC-EAREX 2005 in order to ensure the correctness and accuracy of the lidar retrieval algorithms as well as the aerosol extinction profiles. We compared the vertical profiles of the range-corrected raw lidar signals as well as the aerosol extinction coefficients determined from different types of Mie-scattering lidar systems. Three different aerosol loading cases were selected; in these cases, the mean deviations of the range-corrected raw lidar signals were estimated to be 4.5%, 8.0%, and 7.3%. An intercomparison of the instruments by an identical data-handling procedure (Fernald approach) demonstrated that the aerosol extinction profiles for the three selected cases were in agreement within a bias difference of 0.0051 km<SUP>-1</SUP>. The mean deviation of the signals for the aerosol layer between 0.6 and 3.0 km was 3.0%. The systems were intercompared for two lidar inversion algorithms by using simultaneous lidar measurement data sets as input; these input data sets showed agreement with their aerosol extinction profiles within a bias difference of 0.0086 km<SUP>-1</SUP> and a mean deviation of 11.6%.</P>

Radiative Forcing of Asian Dust Determined from the Synergized GOME and GMS Satellite Data—A Case Study

COSTA, Maria Joã,o,SOHN, Byung-Ju,LEVIZZANI, Vincenzo,SILVA, Ana Maria Meteorological Society of Japan 2006 Journal of the Meteorological Society of Japan Vol.84 No.1

<P>Aerosol optical characteristics of Asian dust are studied by combining Global Ozone Monitoring Experiment (GOME) data, with Geostationary Meteorological Satellite (GMS-5) visible data, collected during a Yellow Sand event occurred on 7 April 2000. Retrieved results were compared with those from solar aureole measurements at Anmyon-Do, Korea. It was shown that the single scattering albedo of Asian dust can be as low as 0.76, much smaller than the generally known values of 0.9 in the Asian dust source region, such as Dunhuang or 0.93 for Saharan dust. This finding suggests that Asian dust can be much absorbing aerosols. The overall atmospheric forcing efficiency (radiation fluxes per unit aerosol optical thickness at 0.5 μm) of Asian dust observed on 7 April 2000, is about 102 Wm<SUP>−2</SUP> in the atmospheric layer, and −116.9 Wm<SUP>−2</SUP> at the surface. These results strongly indicate that the regional surface and atmospheric radiation energy budget, can be significantly altered by the presence of Asian dust.</P>

Comparison of Three Western North Pacific Tropical Cyclone Best Track Datasets in a Seasonal Context

YING, Ming,CHA, Eun-Jeong,KWON, H. Joe Meteorological Society of Japan 2011 Journal of the Meteorological Society of Japan Vol.89 No.3

<P>The quality of tropical cyclone (TC) best track data has increasingly received more attention in climate research in recent years because of the rising interest in the possible effects of global warming on TC activity. In this paper, three best track datasets for the western North Pacific TCs were compared in a seasonal context. Firstly, the statistical characteristics were examined based on their distributions. Then, the potential impact of particular features within the datasets was evaluated by using contrastive cluster analyses. The mean amplitude of the annual cycle in the Japan Meteorological Agency (JMA) data is largest among the three datasets. The smallest interannual variability helped the Shanghai Typhoon Institute of China Meteorological Administration (CMA-STI) dataset to resist the negative effect of outliers. An inhomogeneity around 2003–2004 was identified in the Joint Typhoon Warning Center (JTWC) data by the outliers and was compared with the JMA and CMA-STI data. By using contrastive cluster analyses, the differences among the datasets and some effects related to particular issues, including the representation of the annual cycle, the outliers, and wind conversion were evaluated. The JTWC dataset is affected by outliers and wind conversion among the different average times, whereas the representation of the annual cycle was important for the CMA-STI data. After excluding all the outliers, the results indicated more consistent classifications of the TC annual cycle between the JMA and JTWC data.</P>

Summer Precipitation Changes in Northeast Asia from the AOGCM Global Warming Experiments

LEE, Eun-Jeong,KWON, Won-Tae,BAEK, Hee-Jeong Meteorological Society of Japan 2008 Journal of the Meteorological Society of Japan Vol.86 No.4

<P>In order to evaluate the model performance in simulating the Northeast Asian summer climate, and to investigate the effect of global warming on the summer climate over the Northeast Asian region, the multi-model ensemble of eight atmosphere-ocean coupled general circulation models in the historical (20C3M) and the scenarios (A2, A1B, B1) runs are analyzed, which is participating to the Intergovern mental Panel on Climate Change fourth Assessment Report (IPCC AR4). From comparison of the ob servation and the 20C3M experiment, it is found that the multi-model ensemble quite well simulates the Northeast Asian summer precipitation and circulation, especially in the rst two empirical orthogonal function (EOF) modes and the associated regressed eld. The rst EOF mode represents the decaying phase of El Nino and Southern Oscillation (ENSO), which contributes to the development of the Philip pines Sea anticyclone. The second one is associated with the fast transition of ENSO.In future climate, the increase of the precipitation to 2099 at A2, and A1B simulation reaches 10% com pared with the mean precipitation for 1961-1990 over the Northeast Asian region. After the stabilization of the greenhouse gas concentration in 2100, the precipitation is enhanced during 30 or 50 years more due to the inertia inherent in the climate system. From EOF analysis, it seems that the increased Northeast Asian summer precipitation due to global warming is contributed by the effect of the enhanced monsoon circulation in the decaying phase of El Nino rather than the mean linear increase of global climate or the circulation in the fast transitional period of ENSO.</P>