Sohn B.J.,Seoul National University |
Ryu G.-H.,National Institute of Meteorological Research |
Song H.-J.,Seoul National University |
Ou M.-L.,National Institute of Meteorological Research
Monthly Weather Review | Year: 2013
In contrast to the view that deep convection causes heavy rainfall, Tropical Rainfall Measuring Mission (TRMM) measurements demonstrate that heavy rainfall (ranging from moderate to extreme rain rate) over the Korean peninsula is associated more with low-level clouds (referred to as warm-type clouds in this study) than with conventional deep convective clouds (cold-type clouds). Moreover, it is noted that the low-level warm-type clouds producing heavy rainfall over Korea appear to be closely linked to the atmospheric river, which can form a channel that transports water vapor across the Korean peninsula along the northwestern periphery of the North Pacific high. Much water vapor is transported through the channel and converges on the Korean peninsula when warm-type heavy rain occurs there. It may be possible to produce abundant liquid water owing to the excess of water vapor; this could increase the rate and extent of raindrop growth, primarily below the melting layer, causing heavy rain when these drops fall to the surface. The occurrence of heavy rainfall (also exhibited as medium-depth convection in radar observations over Okinawa, Japan) due to such liquid-water-rich lower warm clouds should induce difficulties in retrieving rainfall from space owing to the lack of scattering-inducing ice crystals over land and the warmer cloud tops. An understanding of the microphysical processes involved in the production of warm-type rain appears to be a prerequisite for better rain retrieval from space and rain forecasting in this wet region. © 2013 American Meteorological Society.
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.
Lee E.-H.,National Institute of Meteorological Research |
Sohn B.-J.,Seoul National University
Atmospheric Environment | Year: 2011
Trends in dust events over China and Mongolia were examined using 34 years (1974-2007) of visibility data over dust source regions of China and 10 years (1998-2007) of dust reports from Synoptic Observations (SYNOP) stations over China and Mongolia. Dust occurrences in Mongolia and northern Inner Mongolia increased over the 1998-2007 SYNOP data period while most dust source regions of China experienced a continuous decrease over the 34-year data period. Increased dust occurrences in Mongolia as well as in Inner Mongolia appear to be caused by degraded surface vegetation and reduced soil moisture associated with intensified drought conditions after the mid-1990s. Results suggest that recent increases in dust events over Korea and Japan are linked to increased dust occurrences over Mongolia and Inner Mongolia. © 2011 Elsevier Ltd.
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.
Kim D.-W.,National Institute of Meteorological Research |
Choi K.-S.,National Typhoon Center |
Byun H.-R.,Pukyong National University
Climate Dynamics | Year: 2012
This study compares the impacts of El Niño Modoki and El Niño on precipitation over Korea during the boreal winters from 1954 to 2009. Precipitation in Korea tends to be equal to or greater than the normal level during an El Niño Modoki winter, whereas there is no significant change during an El Niño winter. Greater than normal precipitation during El Niño Modoki was also found over the lower reaches of the Yangtze River, China and much of southern Japan. The latitudes of these regions are 5-10° further north than in southern China, where precipitation increases during El Niño. The following two anomalous atmospheric circulations were found to be causes that led to different precipitation distributions over East Asia. First, an atmospheric wave train in the lower troposphere, which propagated from the central tropical Pacific (cyclonic) through the southern Philippine Sea (anticyclonic) to East Asia (cyclonic), reached the southern China and northern Philippine Sea during El Niño, whereas it reached Korea and southern Japan during El Niño Modoki. Second, an anomalous local meridional circulation, which consists of air sinking in the tropics, flowing poleward in the lower troposphere, and rising in the subtropics, developed between the southern Philippine Sea and northern Philippine Sea during El Niño. During El Niño Modoki, however, this circulation expanded further to the north and was formed between the southern Philippine Sea and regions of Korea and southern Japan. © 2011 Springer-Verlag.
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.
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.
National Institute Of Meteorological Research | Date: 2016-01-06
An imaging system on an aerial vehicle, includes: a group of rotating camera including at least a first and a second rotating cameras on the aerial vehicle; and a control part which controls a first virtual rotation track of the first rotating camera and a second virtual rotation track of the second rotating camera and allows shots to be taken at multiple photograph-shooting points on the first virtual rotation track and the second virtual rotation track; wherein the control part controls a set of multiple photograph-shooting points on the first virtual rotation track and those on the second virtual rotation track to be substantially in a grid shape. Accordingly, a 3D image could be acquired by using the group of rotating cameras on the aerial vehicle during a relatively short endurance flight and more information on images created in such a method could be estimated.
National Institute Of Meteorological Research | Date: 2014-04-23
Provided is a three-dimensional display apparatus for displaying a global environment image on a spherical surface, namely, a three-dimensional spherical image display apparatus of a global environment which is configured such that the diameter of a sphere and the number of projectors can be variously changed according to the need.
National Institute Of Meteorological Research | Date: 2016-01-06
A method for estimating a position of a target by using an image acquired from a camera is provided. The method includes the steps of: (a) setting multiple virtual estimated reference points by dividing a view-path; (b) comparing altitude values of the respective estimated reference points with those of respective points on terrain; (c) searching neighboring virtual estimated reference points among the multiple virtual estimated reference points to satisfy a requirement under which a difference between an altitude z_(k )of one point among the neighboring estimated reference points and that of the terrain corresponding thereto and a difference between an altitude z_(k+1 )of the other point among the neighboring estimated reference points and that of the terrain corresponding thereto have different signs; and (d) determining that the actual position of the target exists between the searched estimated reference points P_(k).