Papers by Yoon-kyoung Lee
Changes in the wind stress variation with the warm pool SST increase over the western Pacific
EGUGA, May 1, 2014
Changes in the relationship between the oceanic vertical structure variability in the warm-pool and El Nino over 1958-2004
AGU Fall Meeting Abstracts, Apr 1, 2012
Journal of remote sensing, 2019
The satellite-viewed cloudiness, a ratio of cloudy pixels to total pixels (Csat, prev), inevitabl... more The satellite-viewed cloudiness, a ratio of cloudy pixels to total pixels (Csat, prev), inevitably differs from the “ground-viewed” cloudiness (Cgrd) due to different viewpoints. Here we develop an algorithm to retrieve the satellite-viewed, but adjusted cloudiness to Cgrd (Csat, adj). The key process of the algorithm is to convert the cloudiness projected on the plane surface into the cloudiness on the celestial hemisphere from the observer. For this conversion, the supplementary satellite retrievals such as cloud detection and cloud top pressure are used as they provide locations of cloudy pixels and cloud base height information, respectively. The algorithm is tested for Himawari-8 level 1B data. The Csat, adj and Csat, prev are retrieved and validated with Cgrd of SYNOP station over Korea (22 stations) and China (724 stations) during only daytime for the first seven days of every month from July 2016 to June 2017. As results, the mean error of Csat, adj (0.61) is less that than ...
Role of the wind stress forcing on the changes in ENSO amplitude before and after the late 1970s
Longterm changes in wind stress center over the warm-pool region
On the influence of wind stress forcing on ENSO before and after the 1976 climate shift in SODA
Relationship between wind stress forcing and warm pool SST variability in the western Pacific
An estimation of the tropical cyclone size using COMS IR imagery
Asia-Pacific Journal of Atmospheric Sciences, 2021
Record-breaking rainfall occurred over East Asia during the summer of 2020. However, in which asp... more Record-breaking rainfall occurred over East Asia during the summer of 2020. However, in which aspect the summer of 2020 can be differentiated from the other years remains to be quantified. To this end, this study employs Markov chain analysis to quantify summer rainfall variability over East Asia using three Markov descriptors for heavy precipitation events of over 10 mm day−1: frequency, persistence, and entropy (i.e., irregularity). It is found that the heavy rainfall during the summer of 2020 can be attributed to an anomalously high frequency of rainfall in the central China and Japan and greater rainfall persistence over eastern China and Korea. Empirical orthogonal functions (EOFs) are used to analyze interannual variation in the descriptors using a few primary modes. For the summer 2020 period, the first and second modes for frequency account for the enhanced frequency over central China, and this is linked to sea surface temperature anomalies over the North Pacific, the equat...
Climate Dynamics, 2021
Climate models predict that East Asia (EA) will be substantially warmer than the present despite ... more Climate models predict that East Asia (EA) will be substantially warmer than the present despite large inter-model uncertainty. This study investigated the major sources of the climate projections and the inter-model uncertainty. Particularly, we decomposed the differences in surface temperatures between the historical and RCP8.5 runs from 26 CMIP5 into partial surface temperature changes due to individual radiative and non-radiative processes through the climate feedback-response analysis method. Results show that anthropogenic greenhouse forcing and subsequent water vapor feedback processes are primarily responsible for the surface warming over EA. Relatively more rapid warming over the snow/ice-covered area and southern China is due to feedback processes associated with surface albedo and cloud, respectively. The regional warming is, however, compensated by the surface non-radiative (sensible and latent heat) cooling. The inter-model projection uncertainty is substantially large ...
Atmosphere, 2015
An algorithm to symmetric radius of 15 ms −1 isotaches of tropical cyclones is suggested using in... more An algorithm to symmetric radius of 15 ms −1 isotaches of tropical cyclones is suggested using infrared (IR) imagery of geostationary satellite. It is assumed that symmetric tangential winds outside the maximum winds exponentially decrease with the radial distances of the tropical cyclone, which has a clear eye-wall structure. Four parameters for estimation of the tropical cyclone size are center location, maximum sustained wind, radius of the maximum wind, and relaxation coefficient for the decreasing rate with distances of the tropical cyclone. The estimation results are limitedly verified as comparing to surface winds of polar orbiting satellite such as ASCAT data.
Changes in the relationship between increase of the warm-pool SST and El Nino during recent decades
Longterm changes over the western Pacific warm pool
Changes in the ocean stratification over the warm pool region
Changes in the linear relationship of ENSO-PDO under the global warming
International Journal of Climatology, 2012
ABSTRACT We examine changes in El Niño and Southern Oscillation (ENSO)/Pacific Decadal Oscillatio... more ABSTRACT We examine changes in El Niño and Southern Oscillation (ENSO)/Pacific Decadal Oscillation (PDO) relationship under the global warming using coupled climate models participated in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). The temporal structure for the ENSO–PDO relationship is changed remarkably. The relationship between ENSO and PDO during the boreal winter (December, January and February) becomes stronger so that there would be more frequent in phase occurrence of ENSO and PDO (i.e. El Niño—a positive phase of PDO or La Niña—a negative phase of PDO). As PDO could constructively interfere with the ENSO-related climate when ENSO and PDO are in phase, in the future one may expect stronger climate signal because of ENSO in the midlatitude. The IPCC AR4 model also shows that the Pacific North America-like pattern is slightly shifted eastward and much stronger. We also discuss the possible reason for these changes. Copyright © 2012 Royal Meteorological Society
Theoretical and Applied Climatology, 2011
In order to understand the change in oceanic variability associated with the climate shift of the... more In order to understand the change in oceanic variability associated with the climate shift of the mid-1970s, we analyze the contribution of momentum forcing to the leading baroclinic modes over the tropical Pacific using Simple Ocean Data Assimilation (SODA, version 2.0.2) for the period of 1958-1997. Specifically, we look at the statistical relationship between the wind projection coefficients and climate indices and attempt to provide a physical explanation for the observed changes. It is found that the wind stress projection coefficients according to the oceanic baroclinic modes are different in terms of their magnitude and phase in the tropical Pacific, reflecting a specific forcing associated with each mode before and after the 1976 climate shift. Compared to that before the 1970s, the first baroclinic mode is had a greater effect on the interannual sea surface temperature due to equatorial wave dynamics, and there was an increased delayed response of the second baroclinic mode variability to the interannual atmospheric forcing after the late 1970s. This reflects changes in ENSO feedback processes associated with the climate shift. Our analysis further indicates that, after the late 1970s, there was a decrease in the wind stress forcing projecting onto the Ekman layer, which is associated with increased mixed-layer depth. This result suggests that the changes in the ENSO properties before and after the late 1970s are largely associated with the changes in the way in which the wind stress forcing is dynamically projected onto the surface layer of the tropical Pacific Ocean over interannual timescales.
In order to understand the change in oceanic variability associated with the climate shift of the... more In order to understand the change in oceanic variability associated with the climate shift of the mid-1970s, we analyze the contribution of momentum forcing to the leading baroclinic modes over the tropical Pacific using Simple Ocean Data Assimilation (SODA, version 2.0.2) for the period of 1958-1997. Specifically, we look at the statistical relationship between the wind projection coefficients and climate indices and attempt to provide a physical explanation for the observed changes. It is found that the wind stress projection coefficients according to the oceanic baroclinic modes are different in terms of their magnitude and phase in the tropical Pacific, reflecting a specific forcing associated with each mode before and after the 1976 climate shift. Compared to that before the 1970s, the first baroclinic mode is had a greater effect on the interannual sea surface temperature due to equatorial wave dynamics, and there was an increased delayed response of the second baroclinic mode variability to the interannual atmospheric forcing after the late 1970s. This reflects changes in ENSO feedback processes associated with the climate shift. Our analysis further indicates that, after the late 1970s, there was a decrease in the wind stress forcing projecting onto the Ekman layer, which is associated with increased mixed-layer depth. This result suggests that the changes in the ENSO properties before and after the late 1970s are largely associated with the changes in the way in which the wind stress forcing is dynamically projected onto the surface layer of the tropical Pacific Ocean over interannual timescales.
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Papers by Yoon-kyoung Lee