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Park S.-U.,Seoul National University | Park M.-S.,Seoul National University | Chun Y.,National Institute of Meteorological Research
Atmospheric Environment | Year: 2010

A 20-m Asian dust monitoring tower was installed at Erdene in Dornogobi, Mongolia in later 2008, which is one of the high Asian dust source regions in the Asian domain, to investigate meteorological conditions for the dust events. The tower was equipped with meteorological sensors (temperature, humidity and wind speed at four levels, precipitation and pressure near the surface), radiation sensors (solar radiation, net radiation) and soil measurement sensors (soil moisture and soil temperature at three levels and soil heat flux at one level) and turbulent measurement (sonic anemometer) at the 8m height and PM10 concentration measurement (beta guage) at the 3m height. Measurement was made for a full year of 2009. The observed data indicated that dust events occur all year round with the maximum hourly mean maximum concentration of 4107μgm-3 in the early May to a minimum of 92μgm-3 in later August. It was found that the dust concentration at this site is directly related to the wind speed exceeding the threshold wind speed (likewise the corresponding friction velocity) during the winter to early spring. However, the observed dust concentration is not only related to the wind speed exceeding the threshold wind speed but also to the Normalized Difference Vegetation Index (NDVI) during the late spring to the late autumn due to the growth of vegetation. It was also found that the surface soil moisture content does not affect the dust concentration due to the relatively short residence time of the soil moisture in the surface soil. The presently monitored data can be used to verify parameters used in the Asian Dust Aerosol Model (ADAM) that is the operational forecasting dust model in the Korea Meteorological Administration (KMA). © 2010 Elsevier Ltd. Source

Ku B.,Seoul National University | Ku B.,National Institute of Meteorological Research | Park R.J.,Seoul National University
Atmospheric Environment | Year: 2011

Soil dust is the dominant aerosol by mass concentration in the troposphere and has considerable effects on air quality and climate. Parts of East Asia, including southern Mongolia, northern China, and the Taklamakan Desert, are important dust source regions. Accurate simulations of dust storm events are crucial for protecting human health and assessing the climatic impacts of dust events. However, even state-of-the-art aerosol models still contain large uncertainties in soil dust simulations, particularly for the dust emissions over East Asia. In this study, we attempted to reduce these uncertainties by using an inverse modeling technique to simulate dust emissions. We used the measured mass concentration of particles less than 10 μm in aerodynamic diameter (PM10) in the surface air over East Asia, in combination with an inverse model, to understand the dust sources. The global three-dimensional GEOS-Chem chemical transport model (CTM) was used as a forward model. The inverse model analysis yielded a 76% decrease in dust emissions from the southern region of the Gobi Desert, relative to the a priori result. The a posteriori dust emissions from the Taklamakan Desert and deserts in eastern and Inner Mongolia were two to three fold higher than the a priori dust emissions. The simulation results with the a posteriori dust sources showed much better agreement with these observations, indicating that the inverse modeling technique can be useful for estimation of the optimized dust emissions from individually sourced regions. © 2011 Elsevier Ltd. Source

Hong S.,National Institute of Meteorological Research
International Journal of Remote Sensing | Year: 2010

Many satellite remote sensors perform unpolarized measurements. A systematic procedure to decompose measured unpolarized emissivity is proposed using the definition of total reflectivity and the relationship between vertically and horizontally polarized reflectivity. Two polarizations are retrieved for various view angles with mixed emissivity simulated using the refractive index of water for ultraviolet,visible, infrared and microwave wavelengths. The results indicate that the absolute bias errors are small and consistent within Brewster angles, irrespective of the wavelengths. However, the relative bias is less than 4% and 5% for vertical and horizontal polarization, respectively, for any instrument working at infrared and microwave wavelengths. The relative bias for horizontal polarization is 20-30% for ultraviolet and visible wavelengths due to small absolute reflectivity values. Consequently, the method proposed in this study is applicable to specular surfaces for various view angles without the dielectric properties of a medium being required. © 2010 Taylor & Francis. Source

Lee J.,National Institute of Meteorological Research
Physics and Chemistry of the Earth | Year: 2013

In this work, we develop the indirect boundary element method (IBEM) to simulate the seismic site response in a realistic, large-scale 3-D sedimentary basin. Most previous applications of boundary element method have used full-space Green's functions for wave propagation between element points. We use half-space Green's functions, which include the seismic wavefield interactions at the free surface and require only the boundary elements of the basin interface. In this way, the size of the matrix equation for solution in the IBEM can be reduced to approximately a quarter of that using full-space Green's functions. The site response modeling of the Granada basin in southern Spain using the IBEM shows that the basin-induced scattering waves were identified as propagating back and forth inside the basin. The scattered waves also generate surface waves that are weakly propagated outside of the basin. The wave propagation inside and outside of the basin shows different patterns. We observe that the scattered wave is locally amplified, and its propagation direction deviates from that of the incident waves propagation direction. Therefore, the computed seismic response in the basin could provide us with good estimates of the seismic motion. © 2013 Elsevier Ltd. Source

Lee J.-W.,Yonsei University | Hong S.-Y.,Yonsei University | Chang E.-C.,University of Tokyo | Suh M.-S.,Kongju National University | Kang H.-S.,National Institute of Meteorological Research
Climate Dynamics | Year: 2014

This study assesses future climate change over East Asia using the Global/Regional Integrated Model system-Regional Model Program (RMP). The RMP is forced by two types of future climate scenarios produced by the Hadley Center Global Environmental Model version 2 (HG2); the representative concentration pathways (RCP) 4.5 and 8.5 scenarios for the intergovernmental panel on climate change fifth assessment report (AR5). Analyses for the current (1980-2005) climate are performed to evaluate the RMP's ability to reproduce precipitation and temperature. Two different future (2006-2050) simulations are compared with the current climatology to investigate the climatic change over East Asia centered in Korea. The RMP satisfactorily reproduces the observed seasonal mean and variation of precipitation and temperature. The spatial distribution of the simulated large-scale features and precipitation by the RMP is generally less reflective of current climatic conditions than that is given by the HG2, but their inter-annual variations in East Asia are better captured by the RMP. Furthermore, the RMP shows higher reproducibility of climate extremes including excessive heat wave and precipitation events over South Korea. In the future, strong warming is distinctly coupled with intensified monsoonal precipitation over East Asia. In particular, extreme weather conditions are increased and intensified over South Korea as follows: (1) The frequency of heat wave events with temperature greater than 30 °C is projected to increase by 131 and 111 % in the RCP 8.5 and 4.5 downscaling, relative to the current climate. (2) The RCP 8.5 downscaling shows the frequency and variability of heavy rainfall to increase by 24 and 31.5 %, respectively, while the statistics given by the RCP 4.5 downscaling are similar to those of the current climate. © 2013 Springer-Verlag Berlin Heidelberg. Source

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