Impacts of Aerosol Loading on Surface Precipitation from Deep Convective Systems over North Central Mongolia     

Jambajamts Lkhamjav  Hyunho Lee  Ye-Lim Jeon  Jaemyeong Mango Seo  Jong-Jin Baik 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(4):587-598

The impacts of aerosol loading on surface precipitation from mid-latitude deep convective systems are examined using a bin microphysics model. For this, a precipitation case over north central Mongolia, which is a high-altitude inland region, on 21 August 2014 is simulated with aerosol number concentrations of 150, 300, 600, 1200, 2400, and 4800 cm^?3. The surface precipitation amount slightly decreases with increasing aerosol number concentration in the range of 150–600 cm^?3, while it notably increases in the range of 600–4800 cm^?3 (22% increase with eightfold aerosol loading). We attempt to explain why the surface precipitation amount increases with increasing aerosol number concentration in the range of 600–4800 cm^?3. A higher aerosol number concentration results in more drops of small sizes. More drops of small sizes grow through condensation while being transported upward and some of them freeze, thus increasing the mass content of ice crystals. The increased ice crystal mass content leads to an increase in the mass content of small-sized snow particles largely through deposition, and the increased mass content of small-sized snow particles leads to an increase in the mass content of large-sized snow particles largely through riming. In addition, more drops of small sizes increase the mass content of supercooled drops, which also leads to an increase in the mass content of large-sized snow particles through riming. The increased mass content of large-sized snow particles resulting from these pathways contributes to a larger surface precipitation amount through melting and collision-coalescence.  相似文献   

The long-term variability of Changma in the East Asian summer monsoon system: A review and revisit     

June-Yi Lee  MinHo Kwon  Kyung-Sook Yun  Seung-Ki Min  In-Hong Park  Yoo-Geun Ham  Emilia Kyung Jin  Joo-Hong Kim  Kyong-Hwan Seo  WonMoo Kim  So-Young Yim  Jin-Ho Yoon 《Asia-Pacific Journal of Atmospheric Sciences》2017,53(2):257-272

Changma, which is a vital part of East Asian summer monsoon (EASM) system, plays a critical role in modulating water and energy cycles in Korea. Better understanding of its long-term variability and change is therefore a matter of scientific and societal importance. It has been indicated that characteristics of Changma have undergone significant interdecadal changes in association with the mid-1970s global-scale climate shift and the mid-1990s EASM shift. This paper reviews and revisits the characteristics on the long-term changes of Changma focusing on the underlying mechanisms for the changes. The four important features are manifested mainly during the last few decades: 1) mean and extreme rainfalls during Changma period from June to September have been increased with the amplification of diurnal cycle of rainfall, 2) the dry spell between the first and second rainy periods has become shorter, 3) the rainfall amount as well as the number of rainy days during August have significantly increased, probably due to the increase in typhoon landfalls, and 4) the relationship between the Changma rainfall and Western Pacific Subtropical High on interannual time scale has been enhanced. The typhoon contribution to the increase in heavy rainfall is attributable to enhanced interaction between typhoons and midlatitude baroclinic environment. It is noted that the change in the relationship between Changma and the tropical sea surface temperature (SST) over the Indian, Pacific, and Atlantic Oceans is a key factor in the long-term changes of Changma and EASM. Possible sources for the recent mid-1990s change include 1) the tropical dipole-like SST pattern between the central Pacific and Indo-Pacific region (the global warming hiatus pattern), 2) the recent intensification of tropical SST gradients among the Indian Ocean, the western Pacific, and the eastern Pacific, and 3) the tropical Atlantic SST warming.  相似文献   

Effects of several salt marsh plants on mouse spleen and thymus cell proliferation using mtt assay     

Youngwan Seo  Hee-Jung Lee  You Ah Kim  Hyun Joo Youn  Burm-Jong Lee 《Ocean Science Journal》2005,40(4):209-212

In the present study, we have tested the effects of 21 salt marsh plants on cell proliferation of mouse immune cells (spleen and thymus) using MTT assay in culture. The methanolic extracts of six salt marsh plants (Rosa rugosa, Ixeris tamagawaensis, Artemisia capillaris, Tetragonia tetragonoides, Erigeron annus, and Glehnia littoralis) showed very powerful suppressive effects of mouse immune cell death and significant activities of cell proliferationin vitro. Especially, the methanolic extract ofRosa rugosa was found to have fifteen times compared to the control treatment, demonstrating that Rosa rugosa may have a potent stimulation effect on immune cell proliferation. These results suggest that several salt marsh plants includingRosa rugosa could be useful for further study as an immunomodulating agent.  相似文献   

Wave-like wind fluctuations observed in the stable surface layer over a plant canopy     

T. Maitani  Y. Hiramatsu  T. Seo 《Boundary-Layer Meteorology》1984,29(3):273-283

Observations of wind velocity and temperature fluctuations were made in the nocturnal surface inversion layer over a paddy field. A remarkable wave-like motion of about 8 min period was seen in horizontal wind speed and standard deviation of vertical wind velocity. In addition, fluctuations of horizontal wind speed and anticlockwise rotation of wind direction with a period of about 30 min were found by power spectral analysis. The phenomena persisted for more than 2 hours. Similar phenomena were also observed at a coastal site at a distance of about 10 km from the paddy field.  相似文献   

A case study of temperature fluctuations within and above a wheat field before and after sunset     

T. Maitani  T. Seo 《Boundary-Layer Meteorology》1986,35(3):247-256

Temperature fluctuations in the stable air layer before and after sunset were measured at 4 heights within and above a wheat field. Large positive temperature fluctuations were frequently observed within the plant canopy. The standard deviations, skewness factors and flatness factors of temperature fluctuations within the canopy showed peculiar time variations, having remarkable positive skewness factors. The occurrence of large positive temperature fluctuations was probably related to the difference of temperature gradients below and above the observation height, i.e., these fluctuations frequently occurred when the temperature gradient above the observation height was greater than that below the observation height. Furthermore, the vertical mixing associated with the penetration of downdrafts from the air layer above the canopy was requisite for the occurrence of the phenomenon.  相似文献   

Rainfall estimation using raingages and radar — A Bayesian approach: 1. Derivation of estimators     

D. -J. Seo  J. A. Smith 《Stochastic Hydrology and Hydraulics》1991,5(1):17-29

Procedures for estimating rainfall from radar and raingage observations are constructed in a Bayesian framework. Given that the number of raingage measurements is typically very small, mean and variance of gage rainfall are treated as uncertain parameters. Under the assumption that log gage rainfall and log radar rainfall are jointly multivariate normal, the estimation problem is equivalent to lognormal co-kriging with uncertain mean and variance of the gage rainfall field.The posterior distribution is obtained under the assumption that the prior for the mean and inverse of the variance of log gage rainfall is normal-gamma 2. Estimate and estimation variance do not have closed-form expressions, but can be easily evaluated by numerically integrating two single integrals. To reduce computational burden associated with evaluating sufficient statistics for the likelihood function, an approximate form of parameter updating is given. Also, as a further approximation, the parameters are updated using raingage measurements only, yielding closed-form expressions for estimate and estimation variance in the Gaussian domain.  相似文献   

Effect of barley straw biochar application on greenhouse gas emissions from upland soil for Chinese cabbage cultivation in short-term laboratory experiments   总被引：1，自引：0，他引：1  

Se-Won Kang  Dong-Cheol Seo  Yong-Hwa Cheong  Ju-Wang Park  Jong-Hwan Park  Hang-Won Kang  Ki-Do Park  Yong Sik Ok  Ju-Sik Cho 《山地科学学报》2016,13(4):693-702

Chinese cabbage was cultivated in upland soil with the addition of biochar in order to investigate the potential for reduction of greenhouse gas emissions. Barley straw biochar (BSB) was introduced in a Wagner pot (1/5000a) in amounts of 0 (BSB0, control), 100 (BSB100), 300 (BSB300), and 500 (BSB500) kg 10a^-1. After the addition of BSB into the upland soil, carbon dioxide (CO₂) emission increased while methane (CH₄) and nitrous oxide (N₂O) emissions decreased. The highest CO₂ flux was measured for the BSB500 sample, (84.6 g m^-2) followed by BSB300, BSB100, and BSB0 in decreasing order. Relative to those of control, the total CH₄ flux and N₂O flux for the BSB500 treatment were lower by 31.6% and 26.1%, respectively. The global warming potential (GWP) of the treatment without biochar was 281.4 g CO₂ m^-2 and those for treatments with biochar were in the range from 194.1 to 224.9 g CO₂ m^-2. Therefore, introducing BSB into upland soil to cultivate Chinese cabbages can reduce the global warming potential.  相似文献   

Determination of Soil Parameters to Analyze Mechanical Behavior Using Lade's Double-Surface Work-Hardening Model     

Sewook Oh  Junwon Seo 《Marine Georesources & Geotechnology》2016,34(5):465-473

In this study, Lade's double-surface work-hardening constitutive model was adopted which uses the elasto-plasticity model as a basic conceptual framework. The model can analyze work hardening and work softening of nonlinear stress-strain behavior, and is regarded as superior to other elasto-plasticity constitutive models in terms of estimation. In the double-surface work-hardening constitutive model, 14 soil parameters are needed to estimate soil behaviors. To determine them, laboratory tests—isotropical consolidation test and conventional compression test—were conducted. Determining of soil parameters is highly complicated and time-consuming; randomness cannot be ruled out in determining parameters that are sensitive to stress-strain estimation, and error may occur. For this reason, a linear and nonlinear regression analysis was used to determine soil parameters. In estimation of undrained behavior, the estimated stress-strain behavior based on the two constitutive models largely overlapped with the test results. However, in estimating drained behavior, the outcome of the two models and the test results were mostly the same, but between the two models, the double-surface work-hardening constitutive model had a sharper slope in initial stress state, and a smaller maximum deviatoric stress.  相似文献   

Estimating fractional green vegetation cover of Mongolian grasslands using digital camera images and MODIS satellite vegetation indices     

Jaebeom Kim  Bumsuk Seo  Amratuvshin Narantsetseg  Youngji Han 《地理信息系统科学与遥感》2020,57(1):49-59

ABSTRACT

Fractional green vegetation cover (FVC) is a useful indicator for monitoring grassland status. Satellite imagery with coarse spatial but high temporal resolutions has been preferred to monitor seasonal and inter-annual FVC dynamics in wide geographic area such as Mongolian steppe. However, the coarse spatial resolution can cause a certain uncertainty in the satellite-based FVC estimation, which calls attention to develop a robust statistical test for the relationship between field FVC and satellite-derived vegetation indices. In the arid and semi-arid Mongolian steppe, nadir pointing digital camera images (DCI) were collected and used to produce a FVC dataset to support the evaluation of satellite-based FVC retrievals. An optimal DCI processing method was determined with respect to three color spaces (RGB, HIS, L*a*b*) and six green pixel classification algorithms, from which a country-wide dataset of DCI-FVC was produced and used for evaluating the accuracy of satellite-based FVC estimates from MODIS vegetation indices. We applied three empirical and three semi-empirical MODIS-FVC retrieval models. DCI data were collected from 96 sites across the Mongolian steppe from 2012 to 2014. The histogram algorithm using the hue (H) value of the HIS color space was the optimal DCI method (r² = 0.94, percent root-mean-square-error (RMSE) = 7.1%). For MODIS-FVC retrievals, semi-empirical Baret model was the best-performing model with the highest r² (0.69) and the lowest RMSE (49.7%), while the lowest MB (+1.1%) was found for the regression model with normalized difference vegetation index (NDVI). The high RMSE (>50% or so) is an issue requiring further enhancement of satellite-based FVC retrievals accounting for key plant and soil parameters relevant to the Mongolian steppe and for scale mismatch between sampling and MODIS data.  相似文献   

Four-dimensional reflectivity data comparison between two ground-based radars: methodology and statistical analysis     

Bong-Chul Seo  Witold F. Krajewski  James A. Smith 《水文科学杂志》2014,59(7):1320-1334

Abstract

A methodology is proposed to compare radar reflectivity data obtained from two partially overlapping ground-based radars in order to explain relative differences in radar-rainfall products and establish sound merging procedures for multi-radar observing networks. To identify radar calibration differences, radar reflectivity is compared for well-matched radar sampling volumes viewing common meteorological targets. Temporal separation and three-dimensional matching of two different sampling volumes were considered based on the original polar coordinates of radar observation. Since the proposed method assumes radar beam propagation under standard atmospheric conditions, anomalous propagation cases were eliminated from the analysis. The reflectivity comparison results show systematic differences over time, but the variability of these differences is surprisingly large due to the sensitive nature of the radar reflectivity measurement.