1. Overview of 2016/17 Winter Climate over South Korea
So-Young Yim, Hee-Young Cho, Sung-Ho Woo, Dong-Joon Kim
Climate Prediction Division, KMA
24 April, 2017

2. Outlines
Temperature and precipitation over South Korea in 2016/17 winter
Characteristics during the first half of 2016/17 winter
Main teleconnection patterns: Tibetan High and Scandinavian pattern

3. 2016/17 Wintertime Temperature over South Korea
DJF
DEC2016
JAN2017
FEB2017
+1.0℃
+1.6℃
+1.1℃
0.5℃
Daily temperature anomalies
This slide shows the spatial and temporal temperature anomalies over South Korea during 2016/17 winter. South Korea experienced warmer than normal condition during last winter. DJF-mean temperature was 1.0 Celsius degree above than normal. The lower panel is the daily temperature from December 2016 to February The extreme temperatures were observed during the period from mid-December 2016 to mid-January On the other hand, we suffered from cold waves in mid-January and early February 2017.
3rd warmest

4. 2016/17 Wintertime Precipitation over South Korea
DJF
DEC2016
JAN2017
FEB2017
124%
This slide shows precipitation ratio over South Korea during last winter. The ratio of DJF total precipitation amount to normal was 124%, slightly wetter than normal. However, as seen in the monthly precipitation charts, a large variation of precipitation was seen from month to month. In December 2016, total precipitation amount was almost three times more than normal due to the heavy rainfall event on Dec 21~22. In contrast, South Korea received only half of its average January rainfall during January 2017.

5. 2016/17 wintertime SAT and circulation anomalies
The upper panel shows surface air temperature anomalies in each month of 2016/17 winter. You can see a wave-like structure from the Scandinavia peninsula to East Asia. Warming over Scandinavia peninsula and Tibetan Plateau-northeastern Asia and cooling over Caspian sea-northern Siberian region. You can also see apparent wave-like teleconnection pattern in 300hPa geopotential height fields. This wave-like pattern weakened in Jan 2017 and redeveloped in Feb2017. During December 2016, a blocking high was existing over the Bering Sea, thus, cold airs were mostly located on the eastern part of South Korea. During the mid-January and early February 2017, South Korea experienced cold temperature extremes by persistent inflow of cold airs as a blocking high over the Bering Sea moved toward the northwest.

6. Influence of the warming over Kara-Barents on East Asia
Sea ice over the Barents-Kara Sea region related to the Korean winter climate
Arctic Sea ice in October and November 2016 were lowest since 1979.
The left figure is the correlation map between the surface air temperature anomalies with respect to de-trended SAT index averaged over the Barents-Kara Sea region(30E-70E, 70N-80N). The sea-ice loss over the Barents-Kara sea region is related to the warming over the Barents-Kara Sea region. The Barents-Kara Sea surface air temperature anomalies are negatively correlated with the temperature anomalies over the most of Eurasia. This indicates that when the surface air temperature gets warmer over the Barents-Kara Sea region, East Asia experience cold winters. The right figure shows how the Arctic was in autumn Arctic sea ice extent in autumn 2016 was the lowest since We expected that this arctic factor could lead a strong cold winter over the East Asia. But it was different from our expectation. As I said before, 2016/17 winter temperature was warmer than normal.
Kug et al. (2015, Nature Geosci.)
Correlation map between SAT anomalies with respect to de-trended monthly SAT index averaged over the Barents-Kara Sea region

7. Distinct wave-like patterns during warm period
Scandinavia Penn./North Atlantic to the Tibetan Plateau.
Scandinavia Penn./North Atlantic to the northeastern Asia
This slide shows the temperature anomalies at 850hPa and geopotential height anomalies at 500hPa. As shown in left figure, we can see cold temperature anomalies over the Barents-Kara region. Warm temperature anomalies are actually seen in the west of the Barents-Kara region, that is, over the Scandinavia Penn. and TP to northeastern Asia. This wave-like pattern is well seen in the circulation field. It looks like that two wave-like patterns are from the Scandinavia Penn. One is from Scandinavia Penn to TP and from Scandinavia Penn to northeastern Asia.

8. Positive AO and weak Siberian High
SLP
Intensity of Siberian High
In the lower troposphere, the southerly wind anomalies over South Korea dominant prevailed due to the impact of cyclonic anomalies over Siberian region indicating weak Siberian high activities and anticyclonic anomalies over the region covering from the eastern part of South Korea to North Pacific. In addition, the positive Arctic Oscillation (AO) were dominant, thus, the cold surge activities were inactive during this period.
In the SLP field, southerly wind anomalies prevailed over South Korea by the impact of cyclonic anomalies over Siberian region indicating weak Siberian high activities and anticyclonic anomalies over the region covering from the eastern part of South Korea and North Pacific.
Positive AO developed and was strong during the first half of 2016/17 winter.

9. Influences of Tibetan High
◦ The anticyclonic anomaly was developed over the
Tibetan Plateau region, which partly blocked an inflow of cold airs toward the East Asia from the north.
Tibetan High index: H300(70E-105E, 30N-40N)
As I said before, the anticyclonic anomaly was developed over the Tibetan region, which partly blocked an inflow of cold airs toward the East Asia from the north. In order to see circulations associated with Tibetan high system, we did composite analysis when the Tibetan high index is greater than 1 standard deviation. The Tibetan high index was defined by 300hPa-geoptential height anomalies averaged over the 70E-105E, 30N-40N. The composite pattern shows that strong positive anomalies are seen in the TP region and Bering Sea region. The negative anomalies are located over the north. Maybe strong TP could partly contribute to warm temperatures over South Korea.
Courtesy of Dr. JSKug

10. Scandinavian pattern (1)
◦ The cold advection from the upper ridge over the Scandinavia peninsula came into the Barents-Kara region. This could lead to the development of trough over the Ural-Barents-Kara region.
H200
H300
During last winter, a key feature is the teleconnection pattern from the Scandinavia penn. The cold advection from the upper ridge over the Scandinavia penn came into the Barents-Kara region. This may lead to the negative temperature anomalies even though the sea ice extent was very low during last winter. The upper trough associated with the negative temperature anomalies developed over the Ural-Barents-Kara region. Therefore the anomalous high developed over the Scandinavia penn could generate the wave-like pattern.
Courtesy of Dr. JSKug

11. Scandinavian pattern (2)
Scandinavian Index: H300(45N-65N, 10W-20E)
Courtesy of Dr. JSKug

12. Summary
South Korea experienced warmer and wetter than normal during 2016/17 winter.
The strong Tibetan high may block an inflow of cold airs toward the East Asia from the north.
Even though the sea ice extent over the Barents-Kara was very low, the surface air temperature anomaly over there was negative by the continuous cold advection from the Scandinavia Peninsula. The negative temperature anomalies over the Barents-Kara could lead to warm temperature anomalies over South Korea.