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윤경숙,허기영,추정은,하경자,이은정,최유미,Akio Kitoh 한국기상학회 2012 Asia-Pacific Journal of Atmospheric Sciences Vol.48 No.3
We investigate the future changes in the climate zone and six extreme temperature indices in Korea, using the 20-km highresolution atmospheric general circulation model (MRI-AGCM3.1S). The Trewartha and Köppen climate classification schemes are applied, and four summer-based extreme temperature indices (i.e.,summer days, tropical nights, growing degree days, and cooling degree days (CDD) and two winter-based indices (frost days and heating degree days (HDD) are analyzed. To represent significantly the change in threshold indices, the monthly mean bias is corrected in model. The model result reasonably captures the temporal and spatial distribution of the present-day extreme temperatures associated with topography. It was found that in the future climate, the area of the subtropical climate zone in Korea expands northward and increases by 21% under the Trewartha classification scheme and by 35% under the Köppen classification scheme. The spatial change in extreme climate indices is significantly modulated by geographical characteristics in relation to land-ocean thermal inertia and topographical effects. The change is manifested more in coastal regions than in inland regions,except for that in summer days and HDD. Regions with higher indices in the present climate tend to reveal a larger increase in the future climate. The summer-based indices display an increasing trend, while the winter-based indices show a decreasing trend. The most significant increase is in tropical nights (+452%), whereas the most significant decrease is in HDD (-25%). As an important indicator of energy-saving applications, the changes in HDD and CDD are compared in terms of the frequency and intensity. The future changes in CDD reveal a higher frequency but a lower temperature than those in HDD. The more frequent changes in CDD may be due to a higher and less dispersed occurrence probability of extreme temperatures during the warm season. The greater increase in extreme temperature events during the summer season remains an important implication of projecting future changes in extreme climate events.
Effects of Mountain Uplift on Global Monsoon Precipitation
이준이,Bin Wang,서경환,하경자,Akio Kitoh,Jian Liu 한국기상학회 2015 Asia-Pacific Journal of Atmospheric Sciences Vol.51 No.3
This study explores the role of the global mountain uplift (MU), which occurred during the middle and late Cenozoic, in modulating global monsoon precipitation using the Meteorological Research Institute atmosphere-ocean coupled model experiments. First, the MU causes changes in the annual mean of major monsoon precipitation. Although the annual mean precipitation over the entire globe remains about the same from the no-mountain experiment (MU0) to the realistic MU (MU1), that over the Asian-Australian monsoon region and Americas increases by about 16% and 9%, respectively. Second, the MU plays an essential role in advancing seasonal march, and summer-monsoon onset, especially in the Northern Hemisphere, by shaping pre-monsoon circulation. The rainy seasons are lengthened as a result of the earlier onset of the summer monsoon since the monsoon retreat is not sensitive to the MU. The East Asian monsoon is a unique consequence of the MU, while other monsoons are attributed primarily to land-sea distribution. Third, the strength of the global monsoon is shown to be substantially affected by the MU. In particular, the second annual cycle (AC) mode of global precipitation (the spring-autumn asymmetry mode) is more sensitive to the progressive MU than the first mode of the AC (the solstice mode), suggesting that the MU may have a greater impact during transition seasons than solstice seasons. Finally, the MU strongly modulates interannual variation in global monsoon precipitation in relation to El Niño and Southern Oscillation (ENSO). The Progressive MU changes not only the spatial distribution but also the periodicity of the first and second AC mode of global precipitation on interannual timescale.