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This paper investigates the factors affecting the annual number of tropical cyclones (TCs) passing within 100 km of the coast of Korea and Japan (KJ). Using a training set consisting of the coefficients of empirical orthogonal functions of these factors between 1965 and 2005, equations are derived to predict the annual number of these TCs over the whole season in April, and to update this prediction for the July-November (JN) season in June. Results show that the El Niño-Southern Oscillation (ENSO) plays a key role in determining the behaviour of TCs affecting KJ, with more TCs affecting the region during El Niño and less during La Niña. This difference can be attributed to ENSO modifying the flow patterns, which in turn affects TC behaviour. The prediction equations suggest that the 500-hPa geopotential height is more important in determining the number of TCs affecting KJ in the whole season, while both the 850-hPa geopotential height and 850-hPa vorticity play a role in the JN season. Both prediction schemes are able to produce acceptable results, with forecast skills of 42.3 and 33.3% over climatology for the whole, and JN seasons, respectively. The predicted TC number for 2006, 2007, and 2008 are also mostly accurate to within one standard deviation of the observed number. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

We investigate the temporal variations of ground-level ozone and balloon-based ozone profiles at Pohang (36.02 ∘ N, 129.23 ∘ E) in the Korean Peninsula. Satellite measurements and chemical reanalysis products are also intercompared to address their capability of providing consistent information on the temporal and vertical variability of atmospheric ozone. Sub-seasonal variations of the summertime lower-tropospheric ozone exhibit a bimodal pattern related to atmospheric weather patterns modulated by the East Asian monsoon circulation. The peak ozone abundances occur during the pre-summer monsoon with enhanced ozone formation due to favorable meteorological conditions (dry and sunny). Ozone concentrations reach their minimum during the summer monsoon and then re-emerge in autumn before the winter monsoon arrives. Profile measurements indicate that ground-level ozone is vertically mixed up to 400 hPa in summer, while the impact of the summer monsoon on ozone dilution is found up to 600 hPa. Compared to satellite measurements, reanalysis products largely overestimate ozone abundances in both the troposphere and stratosphere and give inconsistent features of temporal variations. Nadir-viewing measurements from the Ozone Monitoring Instrument (OMI) slightly underestimate the boundary layer ozone but represent the bimodal peaks of ozone in the lower troposphere and the interannual changes in the lower-tropospheric ozone in August well, with higher ozone concentrations during strong El Niño events and low ozone concentrations during the 2020 La Niña event. [ABSTRACT FROM AUTHOR]

The combined effect of the El Niño–Southern Oscillation (ENSO) and Arctic Oscillation (AO) on the variability of boreal winter (December–February) temperature over South Korea is examined at the subseasonal time scale using subseasonal-to-seasonal (S2S) hindcast data. Daily hindcast data from the European Centre for Medium-Range Weather Forecasts (ECMWF) database is used. We selected the following six composite cases using a threshold of ±0.5 for each index: El Niño and positive AO (EP), El Niño and negative AO (EN), La Niña and positive AO (LP), La Niña and negative AO (LN), positive AO only (PA), and negative AO only (NA). Results from reanalysis data suggest the possibility of using these two climate factors as predictors for 1-month prediction of South Korea up to 4 weeks in advance. Thus, we confirmed that the ENSO plays a statistically significant role in strengthening (weakening) the AO influences on the temperature anomalies in the in phase (out of phase). For example, there is a significant increase (decrease) in mean temperature anomalies through positive (negative) geopotential height (GPH) anomalies and warm (cold) temperature advection over South Korea in the EP (LN) case. The ECMWF S2S hindcast demonstrated an acceptable ability to reproduce circulation patterns over East Asia up to 3 weeks in advance, and sufficiently predicted weekly mean temperature anomalies over South Korea in EP, LN, and PA cases. [ABSTRACT FROM AUTHOR]

The link between tropical cyclone (TC) activity in the South China Sea (SCS) and global climate change is commonly debated and there is a clear need for long-term geological records of TC activity if we are to clarify this connection. Multi-millennial, high-resolution paleo-storm records from the SCS are rare in the region and this causes difficulties for those exploring potential climate drivers of TC variability over centennial to millennial timescales and reduces our ability to fully assess the risks associated with future TC activity. This paper presents an age-constrained, mud-dominated sedimentary sequence from a coastal lagoon on Hainan Island, China. Multiproxy analyses incorporating chronological, lithological, sedimentological, and geochemical evidence were used to infer storm deposits preserved within the sequence and to reconstruct a time series of storm activity in the SCS during the mid-to-late Holocene. This long sedimentary record shows that TCs were highly active over the periods 5500 to 3500 and 1700 to 0 cal yrs. BP, and these periods contrast with a relatively quiet period 3500–1700 cal yrs. BP. An apparent inverse correlation between TC reconstructions from the SCS and those from the Korean Peninsula and Japan implies an oscillating pattern across the SCS and western North Pacific (WNP) over centennial to millennial timescales. A comparison between the sedimentary and paleoclimatic records implies that the El Niño–Southern Oscillation was not the only mechanism responsible for typhoon variability over the past 7500 cal yrs. BP, suggesting that other factors such as the thermal state of the western Pacific warm pool likely also had a strong influence on both SCS and WNP TC variability. • Sedimentological evidence from Hainan Island was used to reconstruct typhoon activity in the SCS over the mid–late Holocene. • There exists a well-defined seesaw pattern in storm activity across the WNP basin during the study period. • Periods of increased (reduced) storm activity in the SCS typically coincide with La Niña (El Niño) periods and warm (cold) phases of the WPWP during the mid-late Holocene. [ABSTRACT FROM AUTHOR]

The northern and the southern modes are two distinct principle modes that dominate the winter mean surface air temperature (Ts) variations over East Asia (EA). The cold southern mode is represented by a significant cooling south of 45°N and is linked to La Niña events. An objective criterion, which could distinguish the spatial distributions and the maximum center of sea surface temperature anomaly (SSTA), is used to classify the La Niña events into two categories: mega-La Niña and equatorial La Niña. Their impacts are inspected onto the Ts southern mode. The mega-La Niña, featured by a significant K-shape warming in the western Pacific with the maximum SSTA cooling centered in the tropical central Pacific. As a response, an anomalous barotropic high is generated over North Pacific (NP) implying a weak zonal gradient between ocean and the EA continent, which induces a neutral Ts southern mode. The equatorial La Niña characterizes a significant cooling in the tropical eastern Pacific with convective descending motions shifting eastward to the east of the dateline. The resultant low-level circulation anomalies show an anomalous subtropical NP low and a gigantic abnormal EA continent high. The strong zonal gradient results in significant northerly anomalies over EA from 55°N to southeastern China. Over the mid-upper troposphere, the anomalous subtropical NP low extends westward to the Korean Peninsula, leading to a strengthened and southward shifted EA trough. Such abnormal circulation patterns favor the intrusion of cold air to southern EA and correspond to a strong Ts southern mode. The numerical results well validate the above processes and physical mechanisms. [ABSTRACT FROM AUTHOR]