A sudden change in summer rainfall characteristics in Korea during the late 1970s

Abstract

We have examined long-term climate change in Korea by studying daily rainfall data over a period of 48 years . The results show that there is a more frequent heavy rainfall anomaly larger than 100 mm per 3 months in recent years. For further investigation, we divide the whole period into two 24 year intervals, 1954-77 and 1978-2001. Two well-defined rainfall peaks occur during summertime in both intervals. During the earlier interval, primary and secondary rainfall peaks are found in early July and early September, respectively. In the later interval, on the other hand, the secondary peak is found in mid-late August, mainly attributed to enhanced heavy rainfall (≥30 mm day −1 ) events. Although a similar shift occurs in the primary peak, it is much smaller. Thus, the relatively dry spell between the two peaks becomes shorter in the later interval compared with the earlier one.The domain-mean geopotential height at 700 hPa ( 700 ) over mid-latitude Asia (30-50°N, 60-120°E) for the summer also experienced a sudden increase in the mid 1970s. A comparison of the spatial distribution of 700 between the two intervals shows large positive differences over the central-eastern Asian continent in the later interval. In contrast to the positive anomaly of 700 in the later interval, there is a decreasing trend in surface temperature. The increased 700 introduces a stronger northerly wind over East Asia and possibly produces a moisture convergence, enhanced convective activity, and heavy rainfall over the region, in particular over Korea and central China.

Assessment of the changes in extreme vulnerability over East Asia due to global warming

“…3f) is clearly defined in temporal variations of the index, increasing by about 50% during the period. This increase in precipitation extremes over Korea adds to a consensus of previous studies (e.g., Ho et al 2003;Wang et al 2006;Kim et al 2006) which conclude that Korea has become more vulnerable to wet extremes in recent decades.…”

Interdecadal Changes in Heavy Rainfall in China during the Northern Summer

“…Thus, there might be significant short-timescale changes in the EASM circulations, such as frequency and intensity of the synoptic-scale disturbances and typhoon activity. Interestingly, Ho et al (2003) suggested that the desertification over northern China leads to stronger and weaker convective activity over central and northern China, respectively. On the other hand, it is apparent that a significant transition in the northern spring sea surface temperatures over the equatorial Pacific is primarily responsible for the interdecadal changes in the Chinese summer rainfall through the strengthening and southward shift of the North Pacific subtropical high (Gong and Ho 2002).…”

The regime shift in the early 1980s of spring precipitation in Korea

“…The results of the analysis showed that there is a clear regime shift in 1980-1981; in addition, unlike the increasing trend (Ho et al, 2003) of summer (JJA) precipitation in Korea, post-1980 spring precipitation was reduced significantly (approximately 35 mm) compared to pre-1980. This trend was observed from 12 different weather observation stations around the country; in particular, the southwestern part (western part of the Sobaek Mountain Range) of the Korea showed the most significant decrease in the total amount of spring precipitation.…”

“…In another research, the total amounts of spring precipitation in the south China and in the central China have increased and have decreased since the late 1970s, respectively; the opposite phenomenon has been observed during summer (Yang and Lau, 2004). Compared to detailed regional studies in China, only Ho et al (2003) can be cited as a reference concerning the decadal variation (regime shift in the late 1970s) in regional precipitation in Korea, but their study only focusses on summer precipitation, thus indicating negligence of the socioeconomical importance of spring precipitation. Eventually, it is known that the climate regime shift in the spring precipitation in the East Asia, including Korea, is observed in the late 1970s or in the early 1980s.…”