RESEARCH

You are precious just the way you are👍🙂

Research Interests

Stratosphere-Troposphere coupling (QBO downward coupling)
Tropical-Extratropical teleconnection (ENSO, MJO teleconnections)
Improving sub-seasonal to seasonal (S2S) prediction skill of the dynamical prediction models

1. QBO downward coupling on East Asia

Figure 1. Schematic diagram of QBO-East Asia teleconnections adapted from the KMA 2024 report in cooperation with Park and Son.

The Quasi-Biennial Oscillation (QBO) is a dominant interannual variability of stratospheric circulation, characterized by the equatorial zonal wind switching its direction approximately every 14 months.

Although the QBO is an equatorial stratospheric phenomenon, it significantly affects the Northern Hemisphere surface climate by modulating the subtropical jet (Fig. 1 adapted from Park et al., 2022; Park and Son, 2022).

With the goals of improving our understanding and model representations of the QBO and its downward coupling, I and Prof. Son have investigated the 1) downward impact of the QBO on East Asia in late winter (Park et al., 2022), which is more important to that of ENSO (Park and Son, 2022). The 2) key mechanism of the downward coupling is under investigation with an GFDL idealized model experiment (Park et al., in prep.). The 3) operational prediction systems well predict the QBO downward (Park et al., in prep.), however the 4) QBO resolving climate models show a large inter-model spread (QBOi-ENSO WG2 and Park, in prep.). To understand the role of the QBO on this downward coupling simulation, the 5) QBO nudging experiments with models, participating in QBOi phase 2 of the Stratosphere-troposphere Processes And their Role in Climate (SPARC) Quasi-Biennial Oscillation initiative (QBOi), are also investigated (QBOi phase 2 ETWG and Park, in prep.).

2. ENSO teleconnection on East Asia

Figure 2. Schematic diagram of ENSO-East Asia teleconnections adapted from the KMA 2024 report in cooperation with Park and Son.

The El Niño–Southern Oscillation (ENSO) is the dominant mode of interannual variability in the climate system, which is characterized by anomalous sea surface temperature over the equatorial eastern and central Pacific.

During El Niño winters, large-scale anomalous deep convection develops near the central Pacific. The associated upper-level divergence excites the Rossby wave train from the deep tropics to the mid-latitudes, affecting the wintertime surface climate in the western North America, Europe, and Eurasia (Fig. 2. adapted from Park et al., 2023; Park and Son, 2024).

Given the persistent ENSO sea surface temperature anomalies, the ENSO teleconnections have typically been examined on a seasonal timescale. However, the 1) ENSO teleconnections become weakened in mid-winter, which is related to two tropical convection anomalies centered in the central Pacific, Maritime Continent, and Indian Ocean (Park et al., 2018; Park et al., 2023; Park and Son, 2024).

With the goals of improving model representations of the sub-seasonality of ENSO teleconnections, I and Prof. Son have investigated the 2) role of the Indian Ocean and suggested the fact that sub-seasonality of ENSO teleconnections is poorly predicted by 3) multi-model hindcasts, possibly due to the model prediction errors in the timing of Indian Ocean convection and the related teleconnections to mid-latitudes (Park et al., 2023; Park and Son, 2024).

To improve the ENSO teleconnections and surface climate prediction, the 4) regional impact (Park et al., in prep.) and the 5) physical mechanism of the deep convection organization over the Indian Ocean are also investigated (Park and Son, in prep.).

3. Their impacts

Figure 3. Correlations between the East Asian SAT and the two dominant modes of tropical climate variability; ENSO (black) and QBO (red). The filled dots denote the values which are statistically significant at the 95% confidence level.

"Early winter ENSO v.s. Late winter QBO"

ENSO and QBO teleconnections over the East Asia region vary within the winter season. The timing of their influences can be distinguished as '1) ENSO in early winter vs. QBO in late winter (Fig. 3a adapted from Park et al., 2022)'.

In early winter (December), ENSO exerts a dominant influence on East Asian surface climate (Park et al., 2018). The ENSO-East Asia teleconnections show a positive relationship between the ENSO and surface air temperature over the East Asia region, which is modulated by the atmospheric circulation variation over the Kuroshio Extension region.

In late winter (February-March), the influence of ENSO becomes weak, and that of QBO become relatively dominant (Park et al., 2022). The QBO-East Asia teleconnections exhibit a negative relationship between the QBO and surface air temperature over the East Asia region, which is related to the meridional shift of the Asian-Pacific jet (Park et al., 2022).

The above results indicate that ENSO and QBO should be considered in 2) sub-seasonal to seasonal prediction of East Asian winter surface climate.

4. Dynamical-statistical S2S prediction using ENSO & QBO

The newly developed dynamical-statistical prediction model accurately predicts the monthly temperature anomaly for December 2024, as confirmed by the KMA observational data open portal. Prediction value: +0.95 ~ Observation: +0.9.

We are continuously updating and testing the newly developed hybrid model ... (Jan 2025).

Page updated

Google Sites

Report abuse