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국제학술지

공지 (2025. 10. 28.)

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Reexamination of the influence of ENSO on landfalling tropical cyclones in Korea

Abstract: This study examines the influence of the El Niño-Southern Oscillation (ENSO) on the frequency of landfalling tropical cyclones (TCs) in the Korean Peninsula during the TC season, June through October, of the years 1951–2010. An ENSO year is defined when the seasonal mean of the NINO3.4 sea surface temperature (SST) anomalies is greater/less than the typical seasonal mean by 0.5°C. The overall results of this study support that ENSO does not affect the landfalling TCs in Korea; the mean frequencies of the TC landfalls (influences) during El Niño and La Niña calculated over the entire analysis period are 1.1 (3.3) and 1.2 (3.0), respectively. The variations in the basin-wide distribution of TCs show that the influence of ENSO on TC distribution is extended over southeastern Japan with no significant signals coming from over the Korean Peninsula and the East China Sea. The change in the intensity of the landfalling TCs in the Korean Peninsula due to ENSO leads to the same conclusion as that in the frequency of the landfalling TCs. In addition, the same conclusion is obtained when the TC season duration is expanded to include the entire year and when different definitions of the ENSO years (e.g., based on the preceding or following winter NINO3.4 SST anomalies) are selected for analysis.
- 작성자Ho and Kim
- 작성일2024.07.09
- 조회수61
- 2011
Relationship between Arctic Oscillation and cold surges over East Asia

Abstract: The present study reveals the changes in the characteristics of cold surges over East Asia associated with the Arctic Oscillation (AO). Based on circulation features, cold surges are grouped into two general types: wave train and blocking types. The blocking type of cold surge tends to occur during negative AO periods, that is, the AO-related polarity of the blocking type. However, the wave train type is observed during both positive and negative AO periods, although the wave train features associated with negative AO are relatively weaker. The cold surges during negative AO are stronger than those during positive AO in terms of both amplitude and duration. The cold surges during positive AO in which the extent of effect is confined to inland China passes through East Asia quickly because of weaker Siberian high and Aleutian low, leading to short duration of these cold surges. In contrast, the cold surge during negative AO, characterized by a well-organized anticyclone–cyclone couplet with high pressure over continental East Asia and low pressure over Japan, brings continuous cold air into the entire East Asian region for more than one week with long-lasting cold advection. It is also found that the tracks of the cold surges during negative AO tend to occur more frequently over Korea and Japan and less frequently over China, compared with those during positive AO. The tracks are related to a west–east dipole structure of the ratio of rain conversion to snow according to AO phase, resulting in freezing precipitation or snowfall events over inland China (Korea and Japan) are likely to occur more frequently during the positive (negative) AO periods.
- 작성자Park et al.
- 작성일2024.07.09
- 조회수90
- 2011
Strong landfall typhoons in Korea and Japan in a recent decade

Abstract: Long-term changes in tropical cyclones (TCs) that made landfall in Korea and Japan during the TC seasons (June–October) are examined for the period 1977–2008. The TC activity is characterized by four parameters: power dissipation index (PDI), TC-induced rainfall, number of landfall TCs, and TC duration. The analysis period is divided into 2 decades (1977–1988 and 1997–2008). The PDI and TC-induced rainfall increase significantly in the later decade. This enhancement in the TC activity is because of the increase in the number of landfall TCs and the longer duration of the TCs over the two countries. The increase in the number of landfall TCs is associated with the enhanced northward steering flows over the East China Sea. The longer TC duration is mainly due to the high intensity of the approaching TCs prior to landfall. The other factors (i.e., tracks, translational speeds, mean drift lengths, and weakening rates of TCs) could also affect the TC duration, but they are found to be not significant. The results of our study reveal that the recent intensification of TCs is attributable to the changes observed in the later decade in the large-scale environments in the vicinity of the two countries. These changes include warmer sea surface temperature, highly humid midtroposphere, and weaker vertical wind shear over the region. In addition, another responsible factor is the anomalous upward motion driven by the relocation of secondary circulation near the jet entrance, which is highly related with weaker upper tropospheric jet stream in the recent decade.
- 작성자Park et al.
- 작성일2024.07.09
- 조회수74
- 2011
Observational diagnosis of cloud phase in the winter Antarctic atmosphere for parameterizations in climate models

Abstract: The cloud phase composition of cold clouds in the Antarctic atmosphere is explored using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instruments for the period 2000–2006. We used the averaged fraction of liquid-phase clouds out of the total cloud amount at the cloud tops since the value is comparable in the two measurements. MODIS data for the winter months (June, July, and August) reveal liquid cloud fraction out of the total cloud amount significantly decreases with decreasing cloud-top temperature below 0°C. In addition, the CALIOP vertical profiles show that below the ice clouds, low-lying liquid clouds are distributed over ∼20% of the area. With increasing latitude, the liquid cloud fraction decreases as a function of the local temperature. The MODIS-observed relation between the cloud-top liquid fraction and cloud-top temperature is then applied to evaluate the cloud phase parameterization in climate models, in which condensed cloud water is repartitioned between liquid water and ice on the basis of the grid point temperature. It is found that models assuming overly high cut-offs (≫ −40°C) for the separation of ice clouds from mixed-phase clouds may significantly underestimate the liquid cloud fraction in the winter Antarctic atmosphere. Correction of the bias in the liquid cloud fraction would serve to reduce the large uncertainty in cloud radiative effects.
- 작성자Choi et al.
- 작성일2024.06.19
- 조회수57
- 2010
Bayesian forecasting of seasonal typhoon activity: A track-pattern-oriented categorization approach

Abstract: A new approach to forecasting regional and seasonal tropical cyclone (TC) frequency in the western North Pacific using the antecedent large-scale environmental conditions is proposed. This approach, based on TC track types, yields probabilistic forecasts and its utility to a smaller region in the western Pacific is demonstrated. Environmental variables used include the monthly mean of sea surface temperatures, sea level pressures, low-level relative vorticity, vertical wind shear, and precipitable water of the preceding May. The region considered is the vicinity of Taiwan, and typhoon season runs from June through October. Specifically, historical TC tracks are categorized through a fuzzy clustering method into seven distinct types. For each cluster, a Poisson or probit regression model cast in the Bayesian framework is applied individually to forecast the seasonal TC activity. With a noninformative prior assumption for the model parameters, and following Chu and Zhao for the Poisson regression model, a Bayesian inference for the probit regression model is derived. A Gibbs sampler based on the Markov chain Monte Carlo method is designed to integrate the posterior predictive distribution. Because cluster 5 is the most dominant type affecting Taiwan, a leave-one-out cross-validation procedure is applied to predict seasonal TC frequency for this type for the period of 1979–2006, and the correlation skill is found to be 0.76.
- 작성자Chu et al.
- 작성일2024.06.19
- 조회수72
- 2010
Dipolar redistribution of summertime TCG between the Philippine Sea and the northern SCS and its possible mechanisms

Abstract: Recent observational records show that the dipole oscillation between the Philippine Sea (PS) and the northern South China Sea (nSCS) is a leading empirical orthogonal function (EOF) of summertime tropical cyclone (TC) genesis in the western North Pacific (WNP). This PS-nSCS oscillation is characterized by a distinguished decadal variability in addition to an interannual variability. Meanwhile, the typical El Niño–Southern Oscillation (ENSO)-related mode is found in the second EOF mode, which is predominantly interannual. With regard to the PS-nSCS oscillation, its interannual component appears to be linked with the previous wintertime ENSO event, but the linkage is not so robust in the sense that about half of its significant events are classified as the ENSO-related case, whereas its decadal component is coupled to a sea surface temperature anomaly (SSTA) in the central Pacific with its equatorial core near the Niño-4 region, which is flanked by an opposite SSTA on both sides along the latitudinal belt. Interestingly, this SSTA pattern resembles that related to the ENSO Modoki, and equivalently, the transitional phase of ENSO. The ENSO Modoki is regionally manifested by the anomalous zonal SST gradient between the equatorial western and central Pacific; thus the decadal modulation of this anomalous zonal SST gradient can be regarded as an actual forcing that forms and modulates the decadal PS-nSCS oscillation. In addition, the decadal PS-nSCS oscillation is compared with the decadal basin-wide TC genesis variation in terms of the Pacific SSTA pattern and the associated anomalous large-scale environments. Full title: Dipolar redistribution of summertime tropical cyclone genesis between the Philippine Sea and the northern South China Sea and its possible mechanisms
- 작성자Kim et al.
- 작성일2024.06.19
- 조회수51
- 2010
Influence of tropical cyclone landfalls on spatiotemporal variations in typhoon season rainfall over South China

Abstract: This study examined the impact of tropical cyclone (TC) landfalls on the spatiotemporal variations in the rainfall over South China for the period 1957–2005. The target region was selected to show the noteworthy contribution of TC landfalls to the total rainfall during the typhoon season (July–October). Two prevailing spatial variations in the rainfall were obtained from an EOF analysis. The first EOF mode displays single-sign variability over South China with an explained variance of 23.4%. The associated time series of this mode fluctuates on a decadal timescale and was found to be correlated with TC genesis in the South China Sea. The second EOF mode shows a seesaw pattern between Hainan Island/Guangdong Province and the remaining regions with an explained variance of 11.4%. This seesaw pattern results from an anti-correlation in seasonal TC landfalls between the two regions, which was found in previous studies. This is related to the strengthening (weakening) of the upper tropospheric jets and the corresponding development of a massive anticyclonic (cyclonic) circulation over East Asia. The EOF analysis was also conducted using just the data for rainfall caused by landfalling TCs. This revealed that the first EOF mode using just the TC-induced rainfall is nearly identical to the second mode from the total rainfall. The obvious seesaw pattern of the first mode when employing just the TC-induced rainfall in the EOF analysis implies that this pattern has larger temporal variability than the single-signed pattern (i.e., the first EOF mode using the total rainfall) in terms of TC landfalls. This study suggests that TC landfalls over South China and the accompanying rainfall significantly modulate the spatial variation of the typhoon season rainfall there.
- 작성자Lee et al.
- 작성일2024.06.19
- 조회수58
- 2010
Influences of AO and MJO on cold surges and heavy snowfalls over Korea: A case study for the winter of 2009–2010

Abstract: In the winter of 2009–2010, frequent and long-lasting cold weather affected Korea. Four major cold surges and several heavy snowfall events were observed, including a record-breaking event on 4 January 2010. These four cold surges had distinct properties with regard to their relationships to the phases of the Arctic Oscillation (AO) and the Madden-Julian Oscillation (MJO), suggesting the possible influences of the AO and MJO on the cold surges and heavy snowfalls. The four cold surges were of two distinct types: the wave train type and the blocking type, which were differentiated by their mechanisms. With regard to the relationships of the cold surges to the AO, three cold surges occurred during a strongly negative AO period, which lasted for more than 1 month. The Siberian High expanded from the Arctic high-pressure region to East Asia during the negative AO period. A cold surge occurred during a positive AO, with the expansion of the Siberian High across the Eurasian continent. An MJO-induced circulation, corresponding to strong tropical convection over the tropical Indian Ocean, seems to have reinforced the cold surges over East Asia. In addition, the active local Hadley circulation modulated by a convection center over the Indian Ocean tends to enhance midlatitude synoptic disturbances across East Asia and provides favorable conditions for upward motion over the region. In short, the effects of the AO and MJO, along with the existing low-level moisture supply, contributed to heavy snowfalls associated with strong cold surges over Korea during the winter of 2009–2010. Full title: Influences of Arctic Oscillation and Madden-Julian Oscillation on cold surges and heavy snowfalls over Korea: A case study for the winter of 2009–2010
- 작성자Park et al.
- 작성일2024.06.19
- 조회수91
- 2010
On the relationship between Indian Ocean sea surface temperature and the transition from El Niño to La Niña

Abstract: The relationship between Indian Ocean sea surface temperature and the transition of El Niño events into either La Niña or El Niño–Southern Oscillation neutral conditions is examined in both observations and the retrospective ensemble hindcasts of the National Center for Environmental Prediction Climate Forecast System. The southern Indian Ocean is shown to demonstrate a particularly robust and consistent relationship with the evolution of these transitions. These associations are described, and a physical mechanism involving air-sea interaction in the Indian and western Pacific Oceans is proposed. Observations suggest that easterly surface wind anomalies in the western Pacific Ocean are associated with the emergence of La Niña during boreal summer and fall. Here it is shown that these winds are significantly correlated to southern Indian Ocean sea surface temperature in the preceding spring that is characterized by a large-scale zonal dipole of cool and warm anomalies in the southwestern and southeastern Indian Oceans, respectively. These associations are particularly pronounced for strong El Niño conditions, during the dissipation of which a pronounced wavetrain-like atmospheric pattern accompanies sea surface temperature anomalies in the southern Indian Ocean. Together, the circulation and sea surface temperature anomalies increase the meridional cross-equatorial temperature gradient in the western Indian Ocean and mute intraseasonal variability while strengthening surface equatorial easterly winds in the Indo-Pacific warm pool. Collectively, these anomalies favor subsequent La Niña development. On the basis of these observed associations, a predictive model that demonstrates skill in anticipating the nature of El Niño transitions, involving the southern Indian Ocean, Asian monsoon, and El Niño–Southern Oscillation, is proposed. In the National Center for Environmental Prediction Climate Forecast System, the relationships described above are simulated both consistently and realistically, despite model weaknesses, further bolstering a key role of southern Indian Ocean and predictive relationship. Comparison of fully coupled and sea surface temperature–forced simulations suggests a key role for air-sea interaction in the observed associations. Moreover, it is demonstrated that coupled simulations of El Niño–Southern Oscillation may benefit substantially from improved representation of Indian Ocean variability and Indo-Pacific interaction.
- 작성자Yoo et al.
- 작성일2024.06.19
- 조회수51
- 2010
Potential impact of vegetation feedback on European heat waves in a 2 x CO 2 climate

Abstract: Inclusion of the effects of vegetation feedback in a global climate change simulation suggests that the vegetation–climate feedback works to alleviate partially the summer surface warming and the associated heat waves over Europe induced by the increase in atmospheric CO2 concentrations. The projected warming of 4°C over most of Europe with static vegetation has been reduced by 1°C as the dynamic vegetation feedback effects are included. Examination of the simulated surface energy fluxes suggests that additional greening in the presence of vegetation feedback effects enhances evapotranspiration and precipitation, thereby limiting the warming, particularly in the daily maximum temperature. The greening also tends to reduce the frequency and duration of heat waves. Results in this study strongly suggest that the inclusion of vegetation feedback within climate models is a crucial factor for improving the projection of warm season temperatures and heat waves over Europe.
- 작성자Jeong et al.
- 작성일2024.06.19
- 조회수74
- 2010
Roughness length of water vapor over land surfaces and its influence on latent heat flux

Abstract: Latent heat flux at the surface is largely dependent on the roughness length for water vapor (z0q). The determination of z0q is still uncertain because of its multifaceted characteristics of surface properties, atmospheric conditions and insufficient observations. In this study, observed values from the Fluxes Over Snow Surface II field experiment (FLOSS-II) from November 2002 to March 2003 were utilized to estimate z0q over various land surfaces: bare soil, snow, and senescent grass. The present results indicate that the estimated z0q over bare soil is much smaller than the roughness length of momentum (z0m); thus, the ratio z0m/z0q is larger than those of previous studies by a factor of 20 - 150 for the available flow regime of the roughness Reynolds number, Re* > 0.1. On the snow surface, the ratio is comparable to a previous estimation for the rough flow (Re* > 1), but smaller by a factor of 10 - 50 as the flow became smooth (Re* < 1). Using the estimated ratio, an optimal regression equation of z0m/z0q is determined as a function of Re* for each surface type. The present parameterization of the ratio is found to greatly reduce biases of latent heat flux estimation compared with that estimated by the conventional method, suggesting the usefulness of current parameterization for numerical modeling.
- 작성자Park et al.
- 작성일2024.06.19
- 조회수62
- 2010
Satellite retrievals of (quasi-)spherical particles at cold temperatures

Abstract: Measurements from NASA's A-train satellites indicate that spherical or quasi-spherical particles may constitute up to 30% of the total cloud particles at temperatures below −30°C, and up to 10% even for temperatures below −40°C, the temperature range typically found in the upper troposphere and the lower stratosphere. Current climate models calculate cloud radiative forcing on the basis on an assumption that essentially no spherical or quasi-spherical particles exist below −40°C (even below −15°C). The findings in this study show that this widely used assumption in climate models may need re-examination. Further research is also needed to confirm and quantify these findings, especially improvements in the satellite retrievals of cloud particle shapes that, in the mean, currently contain about 10% uncertainties.
- 작성자Choi et al.
- 작성일2024.06.19
- 조회수87
- 2010
Seasonal prediction of summertime tropical cyclone activity over the East China Sea using the least absolute deviation..

Abstract: In the present study, we have employed two statistical models to predict summertime (July–September) tropical cyclone (TC) activity over the East China Sea using the least absolute deviation (LAD) regression and the Poisson regression method. Through a lagged correlation analysis of the relationship between the seasonal TC frequency in the target region and several pre-season environmental parameters for the period 1979–2003, physically interpretable and statistically significant large-scale environmental parameters were identified as potential predictors. After applying the predictor screening method based on the stepwise regression, three predictors, i.e. sea surface temperature, outgoing long-wave radiation and 850-hPa relative vorticity were finally chosen. They are related to the phase transition of El Niño/Southern Oscillation and the strength of the western North Pacific summer monsoon. The correlation coefficient between the predicted and the observed frequency is 0.75 for the LAD model and 0.78 for the Poisson model. The predictions using the two models have a skill improvement of about 60% compared to the reference forecasts. The present study suggests that both models are skillful in predicting summertime TC frequency over the East China Sea with the Poisson model being slightly more skillful than the LAD model. Full title: Seasonal prediction of summertime tropical cyclone activity over the East China Sea using the least absolute deviation regression and the Poisson regression
- 작성자Kim et al.
- 작성일2024.06.19
- 조회수61
- 2010
Space observations of cold-cloud phase change

Abstract: This study examines the vertically resolved cloud measurements from the cloud-aerosol lidar with orthogonal polarization instrument on Aqua satellite from June 2006 through May 2007 to estimate the extent to which the mixed cloud-phase composition can vary according to the ambient temperature, an important concern for the uncertainty in calculating cloud radiative effects. At -20 °C, the global average fraction of supercooled clouds in the total cloud population is found to be about 50% in the data period. Between -10 and -40 °C, the fraction is smaller at lower temperatures. However, there are appreciable regional and temporal deviations from the global mean (> ± 20%) at the isotherm. In the analysis with coincident dust aerosol data from the same instrument, it appears that the variation in the supercooled cloud fraction is negatively correlated with the frequencies of dust aerosols at the -20 °C isotherm. This result suggests a possibility that dust particles lifted to the cold cloud layer effectively glaciate supercooled clouds. Observations of radiative flux from the clouds and earth’s radiant energy system instrument aboard Terra satellite, as well as radiative transfer model simulations, show that the 20% variation in the supercooled cloud fraction is quantitatively important in cloud radiative effects, especially in shortwave, which are 10 - 20 W m-2 for regions of mixed-phase clouds affected by dust. In particular, our results demonstrate that dust, by glaciating supercooled water, can decrease albedo, thus compensating for the increase in albedo due to the dust aerosols themselves. This has important implications for the determination of climate sensitivity.
- 작성자Choi et al.
- 작성일2024.06.19
- 조회수58
- 2010
Spatial interpolation of daily precipitation in China: 1951-2005

Abstract: Climate research relies heavily on good quality instrumental data; for modeling efforts gridded data are needed. So far, relatively little effort has been made to create gridded climate data for China. This is especially true for high-resolution daily data. This work, focuses on identifying an accurate method to produce gridded daily precipitation in China based on the observed data at 753 stations for the period 1951–2005. Five interpolation methods, including ordinary nearest neighbor, local polynomial, radial basis function, inverse distance weighting, and ordinary kriging, have been used and compared. Cross-validation shows that the ordinary kriging based on seasonal semi-variograms gives the best performance, closely followed by the inverse distance weighting with a power of 2. Finally the ordinary kriging is chosen to interpolate the station data to a 18 km× 18 km grid system covering the whole country. Precipitation for each 0.5° × 0.5° latitude-longitude block is then obtained by averaging the values at the grid nodes within the block. Owing to the higher station density in the eastern part of the country, the interpolation errors are much smaller than those in the west (west of 100°E). Excluding 145 stations in the western region, the daily, monthly, and annual relative mean absolute errors of the interpolation for the remaining 608 stations are 74%, 29%, and 16%, respectively. The interpolated daily precipitation has been made available on the internet for the scientific community.
- 작성자Chen et al.
- 작성일2024.06.19
- 조회수78
- 2010
Adaptive change in intra-winter distribution of relatively cold events to East Asian warming

Abstract: For the past few decades, daily winter temperatures over East Asia have been higher and less variable. Generally, these simple temperature-distribution shifts should lead to a decrease in the occurrence of cold extremes, but observations of the changes in the extremes are often complicated. In the present study, the change in the occurrence of relatively cold events (daily temperature anomaly, ≤ -2σ for that season) in each winter monsoon over East Asia was examined using ground observations of daily temperature for the period 1954 - 2006. The time-mean temperature for each winter was subtracted to remove the interannual variability and long-term trend. Our analyses reveal that the intraseasonal temperature distribution over East Asia has changed with a negative skew, and the frequency of the relatively cold events has slightly increased (by 0.09 days per decade) over the past few decades, on an average, for the entire analysis domain (east of 105°E, 122 stations). In particular, the increase occurs more dominantly (82% of the total stations) in regions north of 40°N where a stronger warming has progressed. The frequency of relatively cold events is found to be significantly correlated with the variance of the Siberian high and the mean of the Arctic Oscillation. The increasing trend in the frequency of relatively cold events may serve to partly countervail the decrease (-1.12 days per decade) in the frequency of absolute cold events (daily temperature anomaly, ≤ -2σ overall) across the entire observation period.
- 작성자Choi et al.
- 작성일2024.06.17
- 조회수60
- 2009
Arctic and Antarctic Oscillation signatures in tropical coral proxies over the South China Sea

Abstract: Arctic Oscillation (AO) and Antarctic Oscillation (AAO) are the leading modes of atmospheric circulation in mid-high latitudes. Previous studies have revealed that the climatic influences of the two modes are dominant in extra-tropical regions. This study finds that AO and AAO signals are also well recorded in coral proxies in the tropical South China Sea. There are significant interannual signals of AO and AAO in the strontium (Sr) content, which represents the sea surface temperature (SST). Among all the seasons, the most significant correlation occurs during winter in both hemispheres: the strongest AO-Sr and AAO-Sr coral correlations occur in January and August, respectively. This study also determined that the Sr content lags behind AO and AAO by 1–3 months. Large-scale anomalies in sea level pressure and horizontal wind at 850 hPa level support the strength of AO/AAO-coral teleconnections. In addition, a comparison with oxygen isotope records from two coral sites in neighboring oceans yields significant AO and AAO signatures with similar time lags. These results help to better understand monsoon climates and their teleconnection to high-latitude climate changes.
- 작성자Gong et al.
- 작성일2024.06.17
- 조회수81
- 2009
Estimates of ground-level aerosol mass concentrations using a chemical transport model with MODIS aerosol observations..

Abstract: We estimate ground-level mass concentrations of PM2.5 and PM10 (particulate matter smaller than 2.5 and 10 μm in diameter, respectively) for 2001 using a global chemical transport model with Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) retrievals. Our method improves on previous techniques by using a new satellite product (fine-mode fraction (FMF)) and is applied to East Asia, where such an approach has not previously been attempted. We evaluate the method by comparing the PM estimates with the observations from Air Quality System sites and Acid Deposition Monitoring Network sites across East Asia. The spatial patterns of the annual and seasonal means of the estimated PM10 concentrations are in better agreement with the observations than the results of the model alone. The PM2.5 estimates based on both MODIS AOD and FMF data show considerable improvement relative to those using AOD data alone or simply the model and are in better agreement with the observations at three available sites in Korea and Japan. The greatest improvement is found in the cases where the model significantly underestimates the data. Our best estimates of the annual mean PM2.5 and PM10 concentrations over East Asia are 14.7 and 71.2 μg m−3, respectively. However, the uncertainties in our PM2.5 and PM10 estimates are up to 2.5 and 20 μg m−3, respectively. Full title: Estimates of ground-level aerosol mass concentrations using a chemical transport model with Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol observations over East Asia
- 작성자Choi et al.
- 작성일2024.06.17
- 조회수58
- 2009
Estimating bulk optical properties of aerosols over the western North Pacific by using MODIS and CERES measurements

Abstract: Over the western North Pacific, a large amount of land aerosols from Asian-Pacific countries is transported by the prevailing westerlies. This transport makes the radiative characteristics of these aerosols diverse, particularly when one compares those characteristics over the coastal sea with those over the open sea. In this paper we discuss a method that uses satellite data to obtain the single-scattering albedo (ω) and asymmetry factor (g) of atmospheric aerosols for two large-scale subdivisions—the coastal sea (within 250 km from the coast) and the open sea (the remaining area)—over the western North Pacific (110°E–180°, 20°N–50°N). Our estimation method uses satellite measurements, obtained over a six-year period (2000–2005), of aerosol optical depth (AOD) and shortwave fluxes at both the surface and the top of the atmosphere (TOA); the measurements are obtained using the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth's Radiant Energy System (CERES). For the two subdivisions, the estimated annual means of (ω, g) at 630 nm are significantly different: (0.94, 0.65) over the coastal sea and (0.97, 0.70) over the open sea. From a quantitative viewpoint, this result indicates that in comparison with aerosols over the open sea, those over the coastal sea show greater absorption and lesser forward scattering of solar radiation. The estimated optical properties are responsible for the aerosol surface cooling observed by MODIS and CERES, which is approximately 138 and 108 W m−2 per AOD over the coastal sea and open sea, respectively.
- 작성자Choi et al.
- 작성일2024.06.17
- 조회수57
- 2009
Flux-gradient relationship of water vapor in the surface layer obtained from CASES-99 experiment

Abstract: The flux-gradient relationship of water vapor Φq was obtained from the Cooperative Atmosphere-Surface Exchange Study-1999 (CASES-99) field experiment, which was conducted on a flat and grassy field in the southeastern part of Kansas, USA, during October 1999. The CASES-99 data include turbulence measurements of wind, temperature, and vapor density along with their time-averaged values at various levels above the ground. Quality control of the data on the turbulent wind velocity, sonic temperature, and vapor density was performed prior to flux calculation. The turbulent sensible heat and latent heat fluxes were calculated using a 30-min window, and they were subsequently corrected and checked for the fulfillment of the steady state and for turbulence intensity. Weak fluxes and through-tower wind data were also excluded from the analysis. Vertical gradients of the mean values were obtained by differentiating functions fitted to the measured mean profiles. It was found that Φq is comparable to ΦT for weakly stable stratification and less than ΦT for strongly stable stratification. On the contrary, Φq was found to be larger than ΦT by approximately 20% for the neutral and unstable stratifications. The best fitting functions for water vapor are found to be Φq = 1.21(1 − 13.1z/L)−1/2 and Φq = 1.21(1 + 60.4z/L)−1/3 for the unstable and stable stratifications, respectively.
- 작성자Park et al.
- 작성일2024.06.17
- 조회수248
- 2009