• Atmosphere
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• v.18 no.2
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• pp.147-158
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• 2008

Domestic IOP (intensive observing period) has mostly been represented by the KEOP (Korea Enhanced Observing Period), which started the 5-yr second phase in 2006 after the first phase (2001-2005). During the first phase, the KEOP had focused on special observations (e.g., frontal systems, typhoons, etc.) around the Haenam supersite, while extended observations have been attempted from the second phase, e.g., mountain and downstream meteorology in 2006 and heavy rainfall in the mid-central region and marine meteorology in 2007. So far the KEOP has collected some useful data for severe weather systems in Korea, which are very important in understanding the development mechanisms of disastrous weather systems moving into or developing in Korea. In the future, intensive observations should be made for all characteristic weather systems in Korea including the easterly in the central-eastern coastal areas, the orographically-developed systems around mountains, the heavy snowfall in the western coastal areas, the upstream/downstream effect around major mountain ranges, and the heavy rainfall in the mid-central region. Enhancing observations over the seas around the Korean Peninsula is utmost important to improve forecast accuracy on the weather systems moving into Korea through the seas. Observations of sand dust storm in the domestic and the source regions are also essential. Such various IOPs should serve as important components of international field campaign such as THORPEX (THe Observing system Research and Predictability EXperiment) through active international collaborations.

• Journal of Environmental Science International
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• v.26 no.6
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• pp.741-750
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• 2017

A model coupling a meteorological predictive model and a vegetation photosynthesis and respiration model was used to simulate $CO_2$ concentrations over coastal basin areas, and modeling results were estimated with aircraft observations during a massive sampling campaign. Along with the flight tracks, the model captured the meteorological variables of potential temperature and wind speed with mean bias results of $0.8^{\circ}C$, and 0.2 m/s, respectively. These results were statistically robust, which allowed for further estimation of the model's performance for $CO_2$ simulations. Two high-resolution emission data sets were adopted to determine $CO_2$ concentrations, and the results show that the model underestimated by 1.8 ppm and 0.9 ppm at higher altitude over the study areas during daytime and nighttime, respectively, on average. Overall, it was concluded that the model's $CO_2$ performance was fairly good at higher altitude over the study areas during the study period.

• Journal of Environmental Science International
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• v.16 no.1
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• pp.73-79
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• 2007

The purpose of this study is to clarify the effect of mountain-valley wind on heat island formed in urban area which is located around valley mouth. The meteorological observations were carried out over the Dalbi-valley under a clear summer pressure patterns, and some consideration were tried from the results. In order to make clear the climatological characteristics and air-mass modification process of the mountain-valley wind over the valley, the meteorological observations were done simultaneously at two points. The observational points were located at the breast and valley mouth parts, respectively. The results were as follows: First, it was found that the valley wind was observed through the daytime, and it was replaced by a mountain wind after sunset. Second, the heat budget is also investigated with observation data. The sensible heat flux over the breast of Dalbi-valley reached to about $200 W/m^2$ during daytime, which is a little more than one third of net radiation. On the other hand, the sensible heat flux represented negative values during nighttime. But the sensible heat flux over the valley mouth covered by asphalt showed plus value(about $20{\sim}30 W/m^2$) during the nighttime.

• Journal of Korean Society for Atmospheric Environment
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• v.10 no.4
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• pp.233-244
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• 1994

The phenomenon of yellow sand (dust clouds) occurred in Korea during the spring of 1993 and 1994 is studied in detail. In total 6 cases including 15 days of yellow sand were observed in 1993 and the annual number of these events was found to increased. Examinations in this study include meteorological charts satellite imagery, pilot reports (PIREP) of Korea Air Force, and air concentrations of total suspended particulates(TSP). We present on estimation of total atmospheric loadings based on the observation and theory. According to the PIREP, in general the dust clouds travelled in the lower troposphere up to the level 5km. The visibility within the clouds was in the range of 3-8km The area covered by yellow sand in an event exceeded 0.4 M $\textrm{km}^2$ . According to trajectory analyses, dust clouds invaded Korea in April and May 1993 were landed in the sink area after 2~4 days travelling for 2,000~3,000km from a source region. Estimates of total atmospheric loadings of a dust cloud for April 23~24 in 1993 were 1.5 M ton. In addition, 7 dust storms were also reported in synoptic observations in NW China and Mongolia during the spring in 1994. The yellow sand was not reported with meteorological observations in Korea, however pilots reported significant dust clouds over the Yellow Sea on 8 and 13 April and 20 May 1994.

• Atmosphere
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• v.14 no.3
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• pp.41-54
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• 2004

In this study, a brief overview on a WMO/WWRP program - The Observing System Research and Predictability Experiment (THORPEX) and discussions on perspectives and potential benefits of Asian countries are provided. THORPEX is aimed at accelerating improvements in the accuracy of 1 to 14-day high-impact weather forecasts with research objectives of: 1) predictability and dynamical processes; 2) observing systems; 3) data assimilation and observing strategies; and 4) societal and economic applications. Direct benefits of Asian countries from THORPEX include improvement of: 1) forecast skills in global models, which exerts positive impact on mesoscale forecasts; 2) typhoon forecasts through dropwindsonde observations; and 3) forecast skills for high-impact weather systems via increased observations in neighboring countries. Various indirect benefits for scientific researches are also discussed. Extensive adaptive observation studies are recommended for all high-impact weather systems coming into the Korean peninsula, and enhancement of observations in the highly sensitive regions for the forecast error growth is required to improve forecast skills in the peninsula, possibly through international collaborations with neighboring countries.

• Korean Journal of Remote Sensing
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• v.10 no.1
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• pp.55-67
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• 1994

The International TOVS(TIROS Oprational Vertical Sounders) Process Package(ITPP-VI)is for a global usage, which needs a surface data to generate atmospheric soundings. If the initial input process in the ITPP-VI is not modified, it takes climatic surface data for producing sounding data in general. Korea Meteorological Administration(KMA) is trying to improve the quality of TOVS sounding data using real-time synoptic observations and make a use weather prediction and analysis in various ways. Serval cases in this study show that TOVS retrieved meteolorogical parameters such as atmopheric temperature, dew point depression and geopotential heights used by synoptic surface observations can delineate more detailed atmospheric feature rather than those used by climate surface data. In addition, the collocated comparisons of TOVS synoptic retrieved parameters with radiosonde observations are performed statistically. TOVS retrieved fields with the synoptic surface analyzed data show smaller bias reatively than those with the climatic data and also reduced root mean square differences below 700 hPa as expected.

• Atmosphere
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• v.29 no.4
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• pp.501-509
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• 2019

Asian Dust is a meteorological phenomenon that sand particles are raised from the arid and semi-arid regions-Taklamakan Desert, Gobi Desert and Inner Mongolia in China-and transported by westerlies and deposited on the surface. Asian dust results in a negative effect on human health as well as environmental, social and economic aspects. For monitoring of Asian Dust, Korea Meteorological Administration operates 29 stations using a continuous ambient particulate monitor. Kim et al. (2016) developed an automatic quality check (AQC) algorithm for objective and systematic quality check of observed PM₁₀ concentration and evaluated AQC with results of a manual quality check (MQC). The results showed the AQC algorithm could detect abnormal observations efficiently but it also presented a large number of false alarms which result from valid error check. To complement the deficiency of AQC and to develop an AQC system which can be applied in real-time, AQC has been modulated. Based on the analysis of instrument status codes, valid error check process was revised and 6 status codes were further considered as normal. Also, time continuity check and spike check were modified so that posterior data was not referred at inspection time. Two-year observed PM₁₀ concentration data and corresponding MQC results were used to evaluate the modulated AQC compared to the original AQC algorithm. The results showed a false alarm ratio decreased from 0.44 to 0.09 and the accuracy and the probability of detection were conserved well in spite of the exclusion of posterior data at inspection time.

• Atmosphere
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• v.29 no.4
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• pp.439-450
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• 2019

Present weather plays an important role not only for atmospheric sciences but also for public welfare and road safety. While the widely used state-of-the-art visibility and present weather sensor yields present weather, a single type of measurement is far from perfect to replace long history of human-eye based observation. Truly automatic present weather observation enables us to increase spatial resolution by an order of magnitude with existing facilities in Korea. 8 years of human-eyed present weather records in 19 sites over Korea are compared with visibility sensors and auxiliary measurements, such as humidity of AWS. As clear condition agrees with high probability, next best categories follow fog, rain, snow, mist, haze and drizzle in comparison with human-eyed observation. Fog, mist and haze are often confused due to nature of machine sensing visibility. Such ambiguous weather conditions are improved with empirically induced criteria in combination with visibility and humidity. Differences between instrument manufacturers are also found indicating nonstandard present weather decision. Analysis shows manufacturer dependent present weather differences are induced by manufacturer's own algorithms, not by visibility measurement. Accuracies of present weather for haze, mist, and fog are all improved by 61.5%, 44.9%, and 26.9% respectively. The result shows that automatic present weather sensing is feasible for operational purpose with minimal human interactions if appropriate algorithm is applied. Further study is ongoing for impact of different sensing types between manufacturers for both visibility and present weather data.

• Atmosphere
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• v.28 no.4
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• pp.427-441
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• 2018

This study examines the impact of the urban parameterization scheme and the land cover change on simulated near surface temperature using Unified Model (UM) over the Seoul metropolitan area. We perform four simulations by varying the land cover and the urban parameterization scheme, and then compare the model results with 46 AWS observation data from 2 to 9 August 2016. Four simulations were performed with different combination of two urban parameterization schemes and two land cover data. Two schemes are Best scheme and MORUSES (Met Office Reading Urban Surface Exchange Scheme) and two land cover data are IGBP (International Geosphere and Biosphere Programme) and EGIS (Environmental Geographic information service) land cover data. When land use data change from IGBP to EGIS, urban ratio over the study area increased by 15.9%. The results of the study showed that the higher change in urban fraction between IGBP and EGIS, the higher the improvement in temperature performance, and the higher the urban fraction, the higher the effect of improving temperature performance of the urban parameterization scheme. 1.5-m temperature increased rapidly during the early morning due to increase of sensible heat flux in EXP2 compared to CTL. The MORUSES with EGIS (EXP3) provided best agreement with observations and represents a reasonable option for simulating the near surface temperature of urban area.

• Atmosphere
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• v.31 no.1
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• pp.29-43
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• 2021

In this study, two-step statistical approach including Principal Component Analysis (PCA) and Multiple Linear Regression (MLR) was employed, and main meteorological factors explaining the high-PM2.5 episodes were identified in two regions: Seoul and Busan. We first performed PCA to isolate the Principal Component (PC) that is linear combination of the meteorological variables observed at two levels: surface and 850 hPa level. The employed variables at surface are: temperature (T2m), wind speed, sea level pressure, south-north and west-east wind component and those at 850 hPa upper level variables are: south-north (v850) and west-east (u850) wind component and vertical stability. Secondly we carried out MLR analysis and verified the relationships between PM2.5 daily mean concentration and meteorological PCs. Our two-step statistical approach revealed that in Seoul, dominant factors for influencing the high PM2.5 days are mainly composed of upper wind characteristics in winter including positive u850 and negative v850, indicating that continental (or Siberian) anticyclone had a strong influence. In Busan, however, the dominant factors in explanaining in high PM2.5 concentrations were associated with high T2m and negative u850 in summer. This is suggesting that marine anticyclone had a considerable effect on Busan's high PM2.5 with high temperature which is relevant to the vigorous photochemical secondary generation. Our results of both differences and similarities between two regions derived from only statistical approaches imply the high-PM2.5 episodes in Korea show their own unique characteristics and seasonality which are mostly explainable by two layer (surface and upper) mesoscale meteorological variables.