연구보고서
- 저자
- 이우섭 박사
- 작성일
- 2016.01.23
- 조회
- 405
- 요약
- 목차
Extreme weather events, such as heat waves are receiving more attention in the scientific community in recent years, due to their severe impacts on society and terrestrial ecosystems. The frequency of occurrence of temperature extremes has changed dramatically in the past few decades, for which we cannot exclude the global warming and associated large-scale pattern changes as one of the possible causes. Although the relationship between extreme temperature occurrence and large-scale atmospheric circulation patterns has been extensively studied in the global and regional scales, only a few studies have examined the interannual variability in extreme temperature events in East Asia. The large-scale atmospheric circulation patterns that drive heat waves Korean need to be analyzed in more detail using multi-year observations. As a result, we have made an effort to define new indices to assist in seasonal forecasting and real-time monitoring of the heat waves in Korean.
This report consists of four studies on the following topics: variability and mechanism of heat waves in Korea, its seasonal prediction, predictability of the 2013 heat wave, and domestic policies on health sector adaptation to heat waves.
Variability and mechanism of Korean heat wave
This study investigates the interannual variation of the heat wave frequency (HWF) in Korea during the past 40 years (1973-2012) and explores its connection with large-scale atmospheric circulation patterns. Heat waves in Korea tend to develop most frequently in late summer during July and August. The leading empirical orthogonal function (EOF) that accounts for 50% of the total HWF variance shows a mono-sign pattern over South Korea. This suggests that heat waves have mostly occurred in a national scale. It also exhibits a regional variation with more chance of heat waves in the southeastern inland area. The regression of the leading principal component (PC) time series of HWF with the atmospheric circulation pattern identifies a north-south dipole mode between the South China Sea and East Asia. When this large-scale circulation mode facilitates deep convection in the South China Sea, it tends to weaken moisture transport from the South China Sea to East Asia. Enhanced deep convection in the South China Sea triggers a source of Rossby wave-train along southerly winds that generates positive geopotential height anomalies around Korea. The anomalous high pressure pattern is accompanied by large-scale subsidence in Korea, therefore providing a favorable condition for extreme hot and dry days in Korea.
The dipole pattern appearing in upper-level vorticity between the active (inactive) convection area over the East China Sea and the inactive (active) convection area over East Asia in the case of more (less) frequent heat waves in Korea is explored to find large-scale conditions favorable to heat wave occurence. The vorticity difference index (or KHI) shows a significantly high correlation (r=0.81).
Seasonal prediction of Korean heat wave
The prediction of summer heat wave in Korea remains a significant scientific challenge. In this study we examine the predictability of summer (July-August) Korean heat wave using seasonal prediction models from APEC Climate Center (APCC). The model data used in this study consists of hindcast data for the 23-year period (1983-2005) from 10 operational forecast models.
For the boreal summer, the upper-level vorticity pattern identifies a north- south dipole mode between the South China Sea and East Asia. Observation and individual models represent the dipole mode as the first of EOF of 200hPa vorticity over East Asia.
The temporal correlation between observed heat wave frequency and the first principal component (PC1) at 200hPa vorticity is 0.87. Thus we selected the PC1 of EOF1 for 200hPa vorticity over East Asia as a predictor. The observed 200hPa vorticity explains 20.2% of the total variance; however the models have much larger variances than the observations.
For the multi-model ensemble (MME) with 10 models, the forecast skill for HWF is 0.43 at one month lead time. However, only four models have significant temporal correlation coefficients (TCC) between the observed and simulated PC1 at 200hPa vorticity. The other models cannot predict the variability of HWI well. Thus, the 4 best models were selected based on the TCCs for heat wave frequency prediction. The TCC of HWF between those observed and simulated by best model MME reaches 0.51, which exceeds a 95% confidence level.
Predictability of the 2013 heat wave
We analyzed the atmospheric circulation features associated with the heat wave of the summer of 2013. We found that the strengthening of the Northwestern Pacific High resulting from anomalous convergence over South China contributed to the intensification of the heat wave in 2013. We have used the Korean heat wave Index (KHI) proposed by Lee and Lee (2014). The difference at 200hPa vorticity between the average over 25~30N, 110~130E and the average over 35~40N, 120~140E. KHIs greater than 0 indicate a probability of heat wave occurrence over Korea.
We also investigated the predictability of heat wave occurrence over Korea applying THORPEX Interactive Grand Global Ensemble (TIGGE) data for KHI associated with large scale circulation. The percent correct (PC), threat score (TS), and equitable threat score (ETS) were employed to evaluate the performance of the heat wave forecast. The verifications of PC and TS showed that the highest scores were clearly carried by the heat wave forecast using Heat Wave Index compared to other cases for day 5 through day 7 forecasts. Based on the TIGGE datasets, KHI showed higher predictability of the heat wave than those of Tmax and Bias corrected Tmax (BCT). The values of PC, TS, and ETS for the Koean Heat wave Index (KHI) suggest that the indices could be used for the 7-day forecast. It is concluded that the proposed Heat Wave Index can be useful for forecasting that in turn can reduce the health impacts of heat waves through appropriate and timely actions.
Policy Recommendation
The purpose of this topic is to examine domestic policies on health sector in adaptation to climate change, in particular heat wave. It further aims to recommend future research directions for enhanced response to climate change in public health sector, by taking into account the general features of health adaptation policies.
In this regard, this study first evaluated the current adaptation policies in public health sector examining IPCC WG II AR5, the National Climate Change Adaptation Master Plan (2011-2015) and research papers from the academic community. Second, the early warning system, disaster management, public health, and health care systems were investigated in terms of capacity to adapt to heat wave. The barriers or constraints in establishing and implementing health adaptation policies are analyzed qualitatively, considering the general characteristics of adaptation in the health sector to heat wave.
This study provides four major recommendations: to enhance vulnerability assessment on health-related impacts of heat waves; to improve early warning system; to reinforce the disaster management system; and to strengthen local health institutions for improving public health and emergency management systems.