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국제학술지

공지 (2024. 9. 4.)

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Multiday evolution of convective bursts during WNP TC development and nondevelopment using geostationary satellite...

Abstract: Tropical cyclones (TCs) develop through latent heating from a series of deep convection. To investigate the evolution of diurnal convective burst (CB) activities prior to TC formation, we analyzed 463 tropical disturbances that developed (80) or not developed (383) into TCs over the western North Pacific during the 2007–2009 period. Geostationary satellite data allowed defining deep convection where infrared (IR) brightness temperature is lower than that of water vapor (WV). Diurnal expansions from time series of IR minus WV < 0 areas near disturbance vortex centers for 5 days are defined as CB events. Combined analysis with the Modern Era Retrospective-Analysis shows that the multiday convective-environmental evolution for TC formation is entirely different from nonformation processes in terms of the occurrence of two consecutive diurnal CB events. Multiday CBs (mCB) are observed in 67.5% of the 80 TC formation cases and in 13.8% of the 383 nonformation cases. Intensities of the middle-to-low tropospheric relative vorticity of these two groups are comparable on 4 to 5 days prior to TC formation. However, vorticity intensification is weak for nondeveloping disturbances in environments of strong vertical wind shear; these disturbances eventually decay. The vorticity of developing disturbances continuously intensifies to TC strengths. The remaining 32.5% of the TC cases without mCB show weaker initial vorticity, but rapid intensification over 3 day periods before TC formation. The present results reveal that mCB is a common feature in pre-TC stages, and large-scale environments of weak vertical wind shear are critical for the formation of TC-strength circulations. Full title: Multiday evolution of convective bursts during western North Pacific tropical cyclone development and nondevelopment using geostationary satellite measurements
- 작성자Chang et al.
- 작성일2024.08.22
- 조회수9
- 2017
Dominance of climate warming effects on recent drying trends over wet monsoon regions

Abstract: Understanding changes in background dryness over land is key information for adapting to climate change because of its critical socioeconomic consequences. However, causes of continental dryness changes remain uncertain because various climate parameters control dryness. Here, we verify dominant climate variables determining dryness trends over continental eastern Asia, which is characterized by diverse hydroclimate regimes ranging from arid to humid, by quantifying the relative effects of changes in precipitation, solar radiation, wind speed, surface air temperature, and relative humidity on trends in the aridity index based on observed data from 189 weather stations for the period of 1961–2010. Before the early 1980s (1961–1983), change in precipitation is a primary condition for determining aridity trends. In the later period (1984–2010), the dominant climate parameter for aridity trends varies according to the hydroclimate regime. Drying trends in arid regions are mostly explained by reduced precipitation. In contrast, the increase in potential evapotranspiration due to increased atmospheric water-holding capacity, a secondary impact of warming, works to increase aridity over the humid monsoon region despite an enhanced water supply and relatively less warming. Our results show significant drying effects of warming over the humid monsoon region in recent decades; this also supports the drying trends over warm and water-sufficient regions in future climate.
- 작성자Park et al.
- 작성일2024.08.22
- 조회수18
- 2017
Climatic influence on corn sowing date in the Midwestern United States

ABSTRACT: This study investigated the climatic influence on the corn sowing date in the Midwestern United States by comparing the survey data of corn cultivation with meteorological records in nine states for the last 36 years (1979–2014). The results show that the year-to-year changes in the sowing date were significantly affected by springtime air temperature and precipitation in the nine states, although large state-to-state differences were found in the degree of sowing date–meteorology relationship. We determined that the 36-year climatological warm period (CWP) with daily mean temperatures ≥10 °C plays an important role in the state-to-state differences. For the states with longer CWPs, the influence of air temperature (precipitation) was generally weaker (stronger). This observed counteractive relationship should be considered for crop modelling for more effective assessment of the impact of climate change on agriculture.
- 작성자Choi et al.
- 작성일2024.08.22
- 조회수12
- 2017
An improved parameterization of the allocation of assimilated carbon to plant parts in vegetation dynamics for Noah-MP

Abstract: In the land surface models predicting vegetation growth and decay, representation of the seasonality of land surface energy and mass fluxes largely depends on how to describe the vegetation dynamics. In this study, we developed a new parameterization scheme to characterize allocation of the assimilated carbon to plant parts, including leaves and fine roots. The amount of carbon allocation in this scheme depends on the climatological net primary production (NPP) of the plants. The newly developed scheme is implemented in the augmented Noah land surface model with multiple parameterization options (Noah-MP) along with other biophysical processes related to variations in photosynthetic capacity. The scheme and the augmented biophysical processes are evaluated against tower measurements of vegetation from four forest sites in various regions—two for the deciduous broadleaf and two for the needleleaf evergreen forest. Results from the augmented Noah-MP showed good agreement with the observations and demonstrated improvements in representing the seasonality of leaf area index (LAI), gross primary production (GPP), ecosystem respiration (ER), and latent heat flux. In particular, significant improvements are found in simulating amplitudes and phase shift timing in the LAI seasonal cycle, and the amount of GPP and ER in the growing season. Furthermore, the augmented Noah-MP performed reasonably well in simulating the spatial distributions of LAI, GPP, and NPP in East Asia, consistent with the satellite observations.
- 작성자Gim et al.
- 작성일2024.08.22
- 조회수10
- 2017
Seasonal forecasting of intense tropical cyclones over the North Atlantic and the western North Pacific basins

Intense tropical cyclones (TCs) accompanying torrential rain and powerful wind gusts often cause substantial socio-economic losses in the regions around their landfall. This study analyzes intense TCs in the North Atlantic (NA) and the western North Pacific (WNP) basins during the period 1982–2013. Different intensity criteria are used to define intense TCs for these two basins, category 1 and above for NA and category 3 and above for WNP, because the number of TCs in the NA basin is much smaller than that in the WNP basin. Using a fuzzy clustering method, intense TC tracks in the NA and the WNP basins are classified into two and three representative patterns, respectively. On the basis of the clustering results, a track-pattern-based model is then developed for forecasting the seasonal activities of intense TCs in the two basins. Cross-validation of the model skill for 1982–2013 as well as verification of a forecast for the 2014 TC season suggest that our intense TC model is applicable to operational uses.
- 작성자Choi et al.
- 작성일2024.08.28
- 조회수10
- 2016
Highlighting socioeconomic damages caused by weakened tropical cyclones in the Republic of Korea

To alleviate enormous socioeconomic damages by tropical cyclones (TCs), the Korea Meteorological Administration (KMA) retains a special warning system for strong TCs (STCs, maximum wind speed of the best-track data ≥17 m s−1), but not for relatively weak TCs (WTCs) which are not regarded as threatening as STCs; the warning system encompasses complex extreme phenomena such as gust, downpour, storm surge, and wind wave possibly arising from STCs. However, it is necessary to examine if WTCs can be actually as harmful as STCs with various extreme phenomena. Here, we compare the risks and intensities of WTCs with those of STCs for each province by analyzing the national damage reports and the near-surface wind and rainfall records from 60 weather stations in the Republic of Korea. According to our result, WTCs bring huge damages comparable to STCs in the northwestern Korea, the most populated and the richest area in the country, while WTCs cause much less destruction than STCs in the southeast. The large damages in the northwestern Korea can be explained by different mean landfall locations between WTCs and STCs; the storm centers of WTCs make landfall closer to the northwestern coastline than STCs’. Significant correlations between wind/rainfall and the damage amount by WTCs suggest that WTCs can also induce multiple extreme phenomena like STCs. Thus, the KMA needs to develop a special warning system for WTCs like for STCs.
- 작성자Park et al.
- 작성일2024.08.28
- 조회수12
- 2016
Evaluating the predictability of PM10 grades in Seoul, Korea using a neural network model based on synoptic patterns

As of November 2014, the Korean Ministry of Environment (KME) has been forecasting the concentration of particulate matter with diameters ≤ 10 μm (PM10) classified into four grades: low (PM10 ≤ 30 μg m−3), moderate (30 150 μg m−3). The KME operational center generates PM10 forecasts using statistical and chemistry-transport models, but the overall performance and the hit rate for the four PM10 grades has not previously been evaluated. To provide a statistical reference for the current air quality forecasting system, we have developed a neural network model based on the synoptic patterns of several meteorological fields such as geopotential height, air temperature, relative humidity, and wind. Hindcast of the four PM10 grades in Seoul, Korea was performed for the cold seasons (October–March) of 2001–2014 when the high and very high PM10 grades are frequently observed. Because synoptic patterns of the meteorological fields are distinctive for each PM10 grade, these fields were adopted and quantified as predictors in the form of cosine similarities to train the neural network model. Using these predictors in conjunction with the PM10 concentration in Seoul from the day before prediction as an additional predictor, an overall hit rate of 69% was achieved; the hit rates for the low, moderate, high, and very high PM10 grades were 33%, 83%, 45%, and 33%, respectively. Our findings also suggest that the synoptic patterns of meteorological variables are reliable predictors for the identification of the favorable conditions for each PM10 grade, as well as for the transboundary transport of PM10 from China. This evaluation of PM10 predictability can be reliably used as a statistical reference and further, complement to the current air quality forecasting system.
- 작성자Hur et al.
- 작성일2024.08.28
- 조회수11
- 2016
Does El Niño-Southern Oscillation affect the precipitation in Korea on seasonal time scales?

A number of studies in the past two decades have attempted to find the relationship between the precipitation in Korea and the El Niño-Southern Oscillation (ENSO) on various time scales. Comprehensive analyses of station precipitation data in Korea for the 61-year period, 1954-2014, in this study show that the effects of ENSO on the seasonal precipitation in Korea are practically negligible. The correlation between summer precipitation and ENSO is insignificant regardless of the intensity, type (e.g., eastern-Pacific or central-Pacific), and stage (e.g., developing, mature, or decaying) of ENSO. Somewhat meaningful correlation between ENSO and precipitation in Korea occurs only in the ENSO-developing fall. Because summer rainfall accounts for over half of the annual total and fall is a dry season in Korea, the overall effects of ENSO on precipitation in Korea are practically nonexistent.
- 작성자Ho et al.
- 작성일2024.08.28
- 조회수8
- 2016
A track pattern–based seasonal prediction of tropical cyclone activity over the North Atlantic

A seasonal prediction model of tropical cyclone (TC) activities for the period August-October over the North Atlantic (NA) has been developed on the basis of TC track patterns. Using the fuzzy c-means method, a total of 432 TCs in the period 1965-2012 are categorized into the following four groups: 1) TCs off the East Coast of the United States, 2) TCs over the Gulf of Mexico, 3) TCs that recurve into the open oceans of the central NA, and 4) TCs that move westward in the southern NA. The model is applied to predict the four TC groups separately in conjunction with global climate forecasts from the National Centers for Environmental Prediction (NCEP) Climate Forecast System version 2 (CFSv2). By adding the distributions of the four TC tracks with pre-calculated weighting factors, this seasonal TC forecast model provides the spatial distribution of TC activities over the entire NA basin. Multiple forecasts initialized in six consecutive months from February to July are generated at monthly intervals to examine the applicability of this model in operational TC forecasting. Cross-validations of individual forecasts show that the model can reasonably predict the observed TC frequencies over NA at the 99% confidence level. The model shows a stable spatial prediction skill, proving its advantage for forecasting regional TC activities several months in advance. In particular, the model can generate reliable information on regional TC counts in the near-coastal regions as well as in entire NA basin.
- 작성자Choi et al.
- 작성일2024.08.28
- 조회수10
- 2016
Airborne measurements of high pollutant concentration events in the free troposphere over the West Coast

Aircrafts enable the direct measurement of chemical components in the free troposphere (FT). This study employed airborne measurements to examine the occurrences of high concentrations of SO2 and NOx in the FT over the coastal region west of the Seoul metropolitan area, South Korea. The data from a long-term (1997-2011) airborne measurement campaign were used to determine the meteorological conditions favorable for carrying these pollutants into the Seoul area. The back trajectory analyses of 21 instances of high FT pollutant concentration events showed ascending patterns from the major pollutant sources, mainly the industrial complexes in eastern China, in 9 instances and passing patterns in 12 instances. In the ascending instances, developing low-pressure systems over the source regions provide favorable conditions to uplift air pollutants from the surface into the FT. In the passing instances, an anomalous low-pressure system near the surface prevented airflows from descending into the boundary layer and upper-level anticyclonic systems helped to keep the ascending airflows in the FT. This study proposes the basic mechanisms for predicting air quality in the Seoul area, considering that air pollutants in the FT often entrain into the boundary layer to increase local concentrations.
- 작성자Lee et al.
- 작성일2024.08.28
- 조회수11
- 2016