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국제학술지

공지 (2024. 9. 4.)

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Two types of diurnal variations in heavy rainfall during July over Korea

Abstract: This study examined the characteristics of the diurnal variations of heavy rainfall (⩾110 mm in 12 hours) in Korea and the related atmospheric circulation for July from 1980–2020. During the analysis period, two dominant pattens of diurnal variation of the heavy rainfall emerged: all-day heavy rainfall (AD) and morning only heavy rainfall (MO) types. For the AD-type, the heavy rainfall is caused by abundant moisture content in conjunction with active convection in the morning (0000–1200, LST; LST = UTC + 9) and the afternoon hours (1200–2400 LST). These systems are related to the enhanced moisture inflow and upward motion induced by the strengthening of the western North Pacific subtropical high and upper-tropospheric jet. For the MO-type, heavy rainfall occurs mostly in the morning hours; the associated atmospheric patterns are similar to the climatology. We find that the atmospheric pattern related to severe heavy rainfalls in 2020 corresponds to a typical AD-type and resembles the 1991 heavy-rainfall system in its overall synoptic/mesoscale circulations. The present results imply that extremely heavy rainfall episodes in Korea during the 2020 summer may occur again in the future associated with the recurring atmospheric phenomenon related to the heavy rainfall.
- 작성자Park et al.
- 작성일2024.09.04
- 조회수25
- 2021
What caused the extraordinarily hot 2018 summer in Korea?

Abstract: In 2018, heatwaves (HWs), defined as a period of abnormally hot weather with a daily maximum temperature (T_Max) exceeding its 95th percentile threshold for at least 3 consecutive days, were prevalent from June through August, and temperature records exceeded the reference values in many countries over East Asia (EA), including China (CH), Japan (JP), and the Korean Peninsula (KP). Particularly, extreme HWs from July through August lasted for the longest duration of 21.3 days, with T_Max reaching 36.9°C. The highest T_Max recorded since 1907 was 41°C in Hongcheon, located east of Seoul in the KP. Here, we examined the factors that influenced the 2018 HW, and how these relate to the 1994 HW, which was the second longest HW recorded in the KP. The results showed that abnormally strong and northwestward extended anticyclone features observed in July 2018 lasted as a persistent North Pacific anticyclone anomaly until August 2018, centered at the northern KP. These anticyclone features subsequently formed a modon-like blocking, with a cyclonic anomaly in the East China Sea. In August 1994, the North Pacific High (NPH) extended to eastern EA, which broke down the meridional dipole structure and HWs did not persist. The NPH, which persisted until August 2018, was accompanied by a sinking motion, suppression of precipitation, anomalous maximum temperature, weakening of the westerly jet stream, and increased insolation due to clear sky. We found that the prolonged and northwestward-shifted NPH, including the KP, drove the extraordinarily hot 2018 summer in Korea. In addition, low precipitation and massive evapotranspiration with persistent insolation in July 2018 influenced the dry condition at the surface. We suggest that the predictions for the location and duration of the NPH associated with the HWs are required to reduce heat-related mortality and the impact on agriculture because of excessive evapotranspiration.
- 작성자Ha et al.
- 작성일2024.08.22
- 조회수18
- 2020
Simulations of winter Arctic clouds and associated radiation fluxes using different cloud microphysics schemes in the...

Abstract: Arctic cloud simulations of the polar-optimized version of the Weather Research and Forecasting model (Polar WRF) were compared with retrievals using the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation measurements. For the period from 1 December 2015 to 31 January 2016, a series of 24- to 48-hr simulations initialized daily at 00 UTC were examined. In particular, two cloud microphysics schemes, the Morrison double moment and the WRF single-moment 6-class (WSM6), were tested. The modeled cloud top heights had a correlation coefficient (r) of 0.69–0.72 with those from satellite retrievals, and a mean bias of less than 400 m. For the mean ice water content profile and mixed-phase cloud occurrence, the Morrison scheme's clouds were in better agreement with satellite retrievals than the WSM6. However, the use of the Morrison scheme resulted in underestimates of outgoing longwave radiation by −11.7 W m-2 compared to satellite observations. The bias was reduced to −0.4 W m-2 with the WSM6 which produced a stronger precipitation rate (by 10%) resulting in a drier and less-cloudy atmosphere. This also leads to the 7-W m-2 mean difference in the surface downward longwave radiation (DLR) between the schemes, which is large enough to explain the spread of the Arctic DLR in the current climate models. However, as the temporal variation in DLR showed good agreement with ground observations (r: 0.68–0.92), it is concluded that the Polar WRF can be useful for studying cloud effects on the winter Arctic surface climate. Full title: Simulations of winter Arctic clouds and associated radiation fluxes using different cloud microphysics schemes in the Polar WRF: Comparisons with CloudSat, CALIPSO, and CERES
- 작성자Cho et al.
- 작성일2024.08.22
- 조회수16
- 2020
Projections of future drought intensity associated with various local greenhouse gas emission scenarios in East Asia

Abstract: Efforts to reduce greenhouse gas emissions are ongoing in many East Asian countries; however, their influences on future drought remain unknown. We analyzed future changes in drought intensity over East Asia using the Representative Concen tration Pathway (RCP) 8.5 and the new two limiting local greenhouse gas emission scenarios in East Asia: National Institute of Environmental Research (NIER)-H sce nario for high emission and NIER-L scenario for low emission. The two scenarios were made by a fully coupled global climate model with prescribed gas boundaries of high and low greenhouse gas emissions from an atmospheric chemistry model re flecting the up-to-date environmental policies of South Korea, China, and Japan. The application of a clustering analysis to the calculated drought index time series identi fied four zonally distributed drought regions in the present-day period (1951–2016). Among these regions, higher latitude regions showed a more rapidly increasing trend in drought intensity than other regions for the present-day period. All future scenarios projected the continuation of this meridional intensification trend of drought until 2100; however, the intensification rates in the NIER-L were much smaller than those in the RCP8.5 and NIER-H scenarios. Our results suggest that reducing greenhouse gas emissions is critical for East Asian countries to alleviate the potential damages of future droughts.
- 작성자Park et al.
- 작성일2024.08.22
- 조회수9
- 2020
Interannual variations of spring drought-prone conditions over three subregions of East Asia and associated...

Abstract: For proactive prevention of water shortage problems, it is important to understand the spatiotemporal variabilities of droughts and their development mechanisms. This study identified an interannual variation of spring drought-prone condition in each region of East Asia (EA)—northern, mid, and southern EA—for the period 1979–2015 by using the standardized precipitation evapotranspiration index (SPEI) and a hierarchical clustering analysis. According to our analyses, spring drought-prone condition in the northern EA region mainly depends on local surface heating and precipitation deficit due to adiabatic compression by a high-pressure anomaly over the region during the preceding winter to spring. The high-pressure anomaly was driven by an upper-level wave train propagating from the Europe related to a positive phase of the Arctic Oscillation. For drought-prone conditions in the mid and the southern EA regions, the local precipitation deficit caused by the negative moisture advection/convergence therein acts as a primary factor. During the preceding winter, the negative moisture advection/convergence anomalies both in mid and southern EA regions were induced by anomalous low-level cyclonic circulations over the western North Pacific related to the La Niña. In spring, however, the moisture condition in the southern EA region was affected by persistent La Niña while that in the mid-EA region was by the negative phase of North Pacific Oscillation. This gap makes the main location of the negative moisture advection/convergence anomalies just slightly different, but considerably alter the region exposed to the drought-prone condition. Full title: Interannual variations of spring drought-prone conditions over three subregions of East Asia and associated large-scale circulations
- 작성자Park et al.
- 작성일2024.08.22
- 조회수10
- 2020
Improved mapping and change detection of the start of the crop growing season in the US Corn Belt from long-term AVHRR..

Abstract: Long-term monitoring of crop phenology is a critical process to understand changes in cropland vegetation dynamics related to climate and human management. During the last four decades, seasonal changes in vegetation have been measured by satellite instruments, the Advanced Very High Resolution Radiometers (AVHRRs). However, an acceptable detection of crop phenology has been prevented due to its coarse spatial resolution (~8 km) pixels in which croplands are frequently mixed with non-cropland. This study introduces a novel method for detecting the start of the growing season in cropland (SOSC) from the AVHRR Normalized Difference Vegetation Index (NDVI) to examine the long-term changes in SOSC at the 8-km pixel level across the core cropping regions of the Midwestern United States (the so-called ‘the Corn Belt’) for 1982–2015. The AVHRR-based SOSC was compared with the SOSC retrieved from the pixels covering mostly croplands of the 250-m Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI. These two satellite-based SOSC shows reasonable correspondence in spatial patterns so that the annual values of the root mean square difference ranges from 3.6 to 7.4 days during the overlapping period of 2008–2015. Also, an acceptable correspondence was found between the interannual variations in the AVHRR SOSCs and in the state-level survey of crop stages. For sowing stages, correlation coefficients ranged from 0.43 to 0.68; for flowering stages those ranged from 0.51 to 0.83. By analyzing long-term SOSC changes with climate factors, we found a strong tendency that warmer pre-season condition is accompanied with earlier SOSC. In addition, larger pre-season precipitation tends to postpone SOSC as strongly as the pre-season temperature affects SOSC in a considerable portion of the core cropland. This study suggests that the postponing of sowing due to larger precipitation, which has rarely been highlighted in previous studies, requires more attentions in order for better understanding of vegetation dynamics in agriculture-climate studies. Full title: Improved mapping and change detection of the start of the crop growing season in the US Corn Belt from long-term AVHRR NDVI
- 작성자Gim et al.
- 작성일2024.08.22
- 조회수16
- 2020
Impact of Chinese air pollutants on a record-breaking PMs episode in South Korea for 11-15 January 2019

Abstract: A record-breaking episode of highly concentrated particulate matter (PM) with diameters ≤ 2.5 μm (PM2.5) and ≤10 μm (PM10) occurred in the Republic of Korea during the period January 11–15, 2019: the hourly PM2.5 (PM10) in Seoul was 188 μg m−3 (262 μg m-3) on January 14. At the Baengnyeong and Socheongcho stations, located in the Yellow Sea between China and Korea, the hourly PM2.5 concentration reached up to 155 μg m-3 and 119.8 μg m-3, respectively, 16−19-h prior to this episode. This and the fact that the maximum PM10 concentration at Baengnyeong was 199 μg m-3 indicated a westerly transport of air pollutants. Satellite observations and 72-h back trajectory analysis clearly indicate that air pollutants from China flowed into Korea via the westerlies. According to contribution analysis using particulate matter source apportionment technology in the Comprehensive Air-quality Model with extension, air pollutants originating from northeastern China including Hebei and Shandong provinces were largely linked to the present record-breaking high concentration event in Seoul. This study will elucidate the mechanism of transboundary transport of air pollutants and help East Asian countries cooperate on air quality management.
- 작성자Oh et al.
- 작성일2024.08.22
- 조회수10
- 2020
Enhanced regional terrestrial carbon uptake over Korea revealed by atmospheric CO2 measurements from 1999 to 2017

Abstract: Understanding changes in terrestrial carbon balance is important to improve our knowledge of the regional carbon cycle and climate change. However, evaluating regional changes in the terrestrial carbon balance is challenging due to the lack of surface flux measurements. This study reveals that the terrestrial carbon uptake over the Republic of Korea has been enhanced from 1999 to 2017 by analyzing long-term atmospheric CO2 concentration measurements at the Anmyeondo Station (36.53°N, 126.32°E) located in the western coast. The influence of terrestrial carbon flux on atmospheric CO2 concentrations (ΔCO2) is estimated from the difference of CO2 concentrations that were influenced by the land sector (through easterly winds) and the Yellow Sea sector (through westerly winds). We find a significant trend in ΔCO2 of −4.75 ppm per decade (p < .05) during the vegetation growing season (May through October), suggesting that the regional terrestrial carbon uptake has increased relative to the surrounding ocean areas. Combined analysis with satellite measured normalized difference vegetation index and gross primary production shows that the enhanced carbon uptake is associated with significant nationwide increases in vegetation and its production. Process-based terrestrial model and inverse model simulations estimate that regional terrestrial carbon uptake increases by up to 18.9 and 8.0 Tg C for the study period, accounting for 13.4% and 5.7% of the average annual domestic carbon emissions, respectively. Atmospheric chemical transport model simulations indicate that the enhanced terrestrial carbon sink is the primary reason for the observed ΔCO2 trend rather than anthropogenic emissions and atmospheric circulation changes. Our results highlight the fact that atmospheric CO2 measurements could open up the possibility of detecting regional changes in the terrestrial carbon cycle even where anthropogenic emissions are not negligible.
- 작성자Yun et al.
- 작성일2024.08.22
- 조회수9
- 2020
Dominance of large-scale atmospheric circulations in long-term variations of winter PM10 concentrations over East Asia

Abstract: Concentrations of wintertime particulate matters of diameters below 10 μm (PM10) in South Korea and China have decreased since the 2000s largely owing to the emissions reduction policies of the two countries; however, this decreasing tendency has been notably weakened, or even been reversed, in recent years. This study examines the influence of large-scale atmospheric circulations on this PM10 change over East Asia for the winters (December–February) of the 2004/05–2015/16 period using an empirical orthogonal function (EOF) analysis. The first EOF mode, which accounts for 32.7% of the total variance, indicates decreases in PM10 concentrations until 2012 and thereafter increases in them particularly at most stations in eastern and northeastern China. Regression patterns of meteorological variables with respect to the first EOF time series indicate that the wintertime PM10 variations over East Asia are greatly influenced by the Ural blocking; the weakening of the Ural blocking after 2014 led to the weakening of cold air flows from the north and provided atmospheric conditions favorable for bad air quality events over East Asia. The second EOF mode, which accounts for 20.1% of the total variance, shows a similar spatial distribution as the linear trend of PM10 concentrations during the analysis period and would be related to the long-term changes in emissions. Our findings emphasize that the long-term variations in air quality over East Asia are affected primarily by the variations in large-scale atmospheric circulations with secondary contributions from the changes in emissions.
- 작성자Lee et al.
- 작성일2024.08.22
- 조회수12
- 2020
A dipole mode of spring precipitation between southern China and Southeast Asia associated with the eastern and cent...

Abtract: Because spring precipitation in East Asia is critical for recharging water resources after dry winters, its spatiotemporal variations and related mechanisms need in-depth research. This study analyzed a leading spatiotemporal variability of precipitation over East Asia for boreal spring (March-May) during 1979 to 2017. We found that a dipole mode dominates the anomalous spring precipitation between southern China and Southeast Asia with significant interannual and decadal variations. The interannual dipole mode is attributable to the eastern Pacific (EP)-type El Niño-Southern Oscillation (ENSO) while the decadal dipole mode is related to the decadal variation of the central Pacific (CP)-type ENSO. In the El Niño phases of both time scales, the anticyclonic anomaly over the South China Sea and Philippines causes moisture convergence (divergence) over southern China (Southeast Asia), resulting in positive (negative) precipitation anomalies therein; the opposite occurs in the La Niña phases. The ensemble experiments using the Community Atmosphere Model version 5.1 confirmed that the tropical sea surface temperature (SST) in the EP- and CP-type ENSO can be the major drivers of the interannual and decadal dipole modes, respectively. About half of 15 climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) showed that the El Niño phase of dipole mode will become dominant in the future. The individual models' future projections however considerably vary, implying that there is still large uncertainty. Full title: A dipole mode of spring precipitation between southern China and Southeast Asia associated with the eastern and central Pacific types of ENSO
- 작성자Park et al.
- 작성일2024.08.22
- 조회수10
- 2020