Modeling North Pacific Decadal Variations and Their Teleconnection Patterns

• Main Authors: Pei-Ning Feng, 馮培寧
• Other Authors: Yu-Heng Tseng
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/56059170489058455207

碩士 === 國立臺灣大學 === 大氣科學研究所 === 100 === Low-frequency fluctuations of the ocean and atmosphere over the North Pacific on interannual to decadal time scales significantly impact on the weather, climate and even the marine ecosystems in the East Asia and Western North Pacific. However, modeling the North Pacific climate variability remains a challenging task. It is well-known that the variability in the north Pacific is complicated, and the mechanisms behind the climate variability and its teleconnection with other basins still remain unclear. In this research, our goals are identifying and understanding these patterns and variations in the model so as to provide a completed picture of the North Pacific Climate. Empirical Orthogonal Function (EOF) has been commonly used to identify the leading modes at different horizontal levels, which change phase at annual, interannual to quasi-decadal scale. From top to the surface, the leading EOF mode of 500 hPa geopotential height is well-known as Pacific/North-American Pattern (PNA). For the Sea Level Pressure (SLP) pattern, the first EOF mode is known as Aleutian Low (AL) in the Pacific Ocean, and North Atlantic Oscillation (NAO) in the North Atlantic region. At the Sea Surface Temperature (SST) and Sea Surface Height (SSH), the corresponding pattern in the Pacific Ocean is well-known for Pacific Decadal Oscillation (PDO) in the mid-latitude and the El Nino Southern Oscillation (ENSO) in the tropics. Recently, the second modes of climate patterns raise more and more researches and they are referred as an important role on modulating the climate variability because they were highly correlated with the change of the ecosystems. The second EOF modes include low frequency oscillations in decadal scales. In the Pacific Ocean, the second mode at 500hPa, SLP and SSH(or SST) are Western Pacific (WP), North Pacific Oscillation (NPO) and North Pacific Gyre Oscillation (NPGO) respectively. We will evaluate those climate variables and teleconnection patterns in the North Pacific by using latest coupled model, TaiWan Earth System Model (TWESM). By comparing the model results with IPCC-AR4 models and observations data, we obtained a reasonable simulation. According to the simulation, we attempted to investigate the marginal maritime area in western Pacific to see if the variabilities would impact. The TWESM is able to reproduce the evolution of the leading modes in the marginal seas and with background variabilities while the hidden mechanisms still need more studies. Eventually, we anticipate to bridging the low-frequency climate variation to the global climate pattern.