Seasonally Varying Reference Atmospheres for East Asia     

Byung-Ju SOHN  Geun-Hyeok RYU 《大气科学进展》2007,24(2):181-190

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An accurate and efficient radiative transfer model for simulating all-sky images from Fengyun satellite radiometers     

Yao  Bin  Liu  Chao  Teng  Shiwen  Bi  Lei  Zhang  Zhiqing  Zhang  Peng  Sohn  Byung-Ju 《中国科学:地球科学(英文版)》2020,63(11):1701-1713

Science China Earth Sciences - Forward radiative transfer models (RTM) are an indispensable tool for quantitative applications of satellite radiometers, e.g., for data calibration, instrument...  相似文献   

Evaluation of the weather generator CLIGEN with daily precipitation characteristics in Korea   总被引：1，自引：0，他引：1  

Young-Mi Min  Vladimir N. Kryjov  Kyong-Hee An  Saji N. Hameed  Soo-Jin Sohn  Woo-Jin Lee  Jai-Ho Oh 《Asia-Pacific Journal of Atmospheric Sciences》2011,47(3):255-263

The ability of the CLImate GENerator (CLIGEN) weather generator to reproduce daily precipitation characteristics for Korea was assessed on the basis of 55-year long historical daily precipitation records from eight weather stations (Seoul, Incheon, Daegu, Ulsan, Gwangju, Busan, Kangneung, and Jeonju) representing different parts of the Korean peninsula. The basic statistics of daily precipitation (mean, standard deviation, skewness of daily precipitation, number of rainy days, and the lengths of wet/dry period), probability distribution characteristics of daily precipitation (percentiles and maximum value), and the spatial covariance statistic generated by CLIGEN were compared with those derived from the observed weather series. Significance tests were conducted on the difference between the historical and generated statistics with the 1% significance level. The results show that CLIGEN simulates most of the daily precipitation characteristics satisfactorily with a tendency to slightly underestimate the mean and variability of daily precipitation. Especially, the number of rainy days is perfectly reproduced with mean relative error of 0.4% across all the stations. It is also found that the spatial covariance statistic from eight different stations is well reproduced by CLIGEN with respect to the leading EOF mode of summer season daily precipitation.  相似文献   

Climatological assessment of desert targets over East Asia — Australian region for the solar channel calibration of geostationary satellites     

Hyoung-Wook Chun  B. J. Sohn 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(2):239-246

Desert targets for solar channel calibration of geostationary satellites in the East Asia — Australian region were selected and their qualities were assessed with aid of Moderate Resolution Imaging Spectroradiometer data (i.e., white-sky surface albedo, aerosol optical thickness, and cloud fraction) from 2002 to 2008. The magnitude, spatial uniformity, and temporal stability of the white-sky surface albedo are examined in order to select bright and stable targets. Subsequently those selected targets over China, India, and Australia are further checked for their qualities in terms of data yielding ratio, aerosol optical thickness, cloud fraction, satellite viewing angle, and solar zenith angle. Results indicate that Chinese targets are found to be not adequate as calibration targets in spite of excellent surface conditions because of high percentage of cloud, possibly heavy aerosol loading, and lower solar elevation angle in particular during winter time. Indian site should be take care about relatively high temporal variation of surface condition and heavy aerosol loading. On the other hand, Australian desert targets are considered to be best when surface brightness, spatial and temporal stability, data yielding ratio, aerosol, and cloud are counted.  相似文献   

Transition from debris flow to hyperconcentrated flow in a submarine channel (the Cretaceous Cerro Toro Formation, southern Chile)     

Y. K. Sohn  M. Y. Choe  H. R. Jo 《地学学报》2002,14(5):405-415

ABSTRACT It is important to understand the exact process whereby very large amounts of sediment are transported. This paper reports peculiar conglomerate beds reflecting the transition of submarine debris flows into hyperconcentrated flows, something that has been well documented only in subaerial debris-flow events until now. Voluminous debris flows generated along a Cretaceous submarine channel, southern Chile, transformed immediately into multiphase flows. Their deposits overlie fluted or grooved surfaces and comprise a lower division of clast-supported and imbricated pebble–cobble conglomerate with basal inverse grading and an upper division of clast- to matrix-supported, disorganized conglomerate with abundant intraformational clasts. The conglomerate beds suggest temporal succession of turbidity current, gravelly hyperconcentrated flow, and mud-rich debris flow phases. The multiphase flows resulted from progressive dilution of gravelly but cohesive debris flows that could hydroplane, in contrast to the flow transitions in subaerial environments, which involve mostly non-cohesive debris flows. This finding has significant implications for the definition, classification, and hazard assessment of submarine mass-movement processes and characterization of submarine reservoir rocks.  相似文献   

Use of total precipitable water classification of a priori error and quality control in atmospheric temperature and water vapor sounding retrieval     

Eun-Han KWON  Jinlong LI  B. J. SOHN  Elisabeth WEISZ 《大气科学进展》2012,29(2):263-273

This study investigates the use of dynamic a priori error information according to atmospheric moistness and the use of quality controls in temperature and water vapor profile retrievals from hyperspectral infrared (IR) sounders. Temperature and water vapor profiles are retrieved from Atmospheric InfraRed Sounder (AIRS) radiance measurements by applying a physical iterative method using regression retrieval as the first guess. Based on the dependency of first-guess errors on the degree of atmospheric moistness, the a priori first-guess errors classified by total precipitable water (TPW) are applied in the AIRS physical retrieval procedure. Compared to the retrieval results from a fixed a priori error, boundary layer moisture retrievals appear to be improved via TPW classification of a priori first-guess errors. Six quality control (QC) tests, which check non-converged or bad retrievals, large residuals, high terrain and desert areas, and large temperature and moisture deviations from the first guess regression retrieval, are also applied in the AIRS physical retrievals. Significantly large errors are found for the retrievals rejected by these six QCs, and the retrieval errors are substantially reduced via QC over land, which suggest the usefulness and high impact of the QCs, especially over land. In conclusion, the use of dynamic a priori error information according to atmospheric moistness, and the use of appropriate QCs dealing with the geographical information and the deviation from the first-guess as well as the conventional inverse performance are suggested to improve temperature and moisture retrievals and their applications.  相似文献   

Optical dating of hydromagmatic volcanoes on the southwestern coast of Jeju Island, Korea     

C.S. Cheong  J.H. Choi  Y.K. Sohn  J.C. Kim  G.Y. Jeong 《Quaternary Geochronology》2007,2(1-4):266-271

Jeju Island, the largest Quaternary volcanic island in Korea, has formed mostly since the early Pleistocene, but its latest chronology of volcanism and sedimentation is still poorly constrained. Here we report optically stimulated luminescence (OSL) ages for two hydromagmatic volcanoes on the southwestern coast of Jeju Island, i.e., the Songaksan and Suwolbong tuff rings. The basaltic tuffs of these volcanoes contain abundant quartz sands from underlying marine sedimentary sequences. Two samples collected from the middle part of the Songaksan Tuff yielded highly reproducible quartz single-aliquot regenerative-dose (SAR) OSL ages of 7.0±0.3 ka, providing the first direct age estimate of Holocene volcanism in Jeju Island. The quartz OSL age estimate of 5.1±0.3 ka for the younger reworked basaltic tuff (the Hamori Formation) is comparable with previous radiocarbon and U-series disequilibrium dating of fossil mollusk shells. Two samples from the Suwolbong Tuff show quartz OSL age estimates of 18.3±0.7 and 18.6±0.9 ka, which are identical within error ranges and younger than the quartz OSL age estimate of 23.2±1.0 ka for the underlying Gosan Formation. This study confirms that volcanism and attendant sedimentation were active in Jeju Island until very recently.  相似文献   

Validating infrared-based rainfall retrieval algorithms with 1-minute spatially dense raingage measurements over Korean peninsula     

H.-J. Oh  B.-J. Sohn  E. A. Smith  F. J. Turk  Ae-suk Seo  H.-S. Chung 《Meteorology and Atmospheric Physics》2002,81(3-4):273-287

Summary ?This study compares and contrasts six infrared-based satellite rain estimation techniques and their validation during a 2-month period from June 20–August 20, 1998 over the Korean peninsula. Two probability matching techniques (PMM1, PMM2), a look-up table technique (LUT), a convective-stratiform technique (CST), the Negri-Adler-Wetzel technique (NAWT), and the Arkin technique (ARKT) are applied to hourly infrared GMS imagery. Retrieved rainrates are compared against one-minute reporting raingage observations from the dense Automated Weather Station (AWS) network of Korea. The high spatial resolution and fine temporal resolution of the AWS measurements provide a unique and effective means to validate rain estimates derived from instantaneous space measurements, which is a main scientific focus of this study. Validation results indicate that all techniques exhibit better performance for more evenly spread rain events while exhibiting lesser performance for weak and sporadic rains for which validation sampling becomes more of a problem. Validation statistics show that climatologically-local techniques such as the PMM and LUT algorithms perform better than techniques developed in climatologically different regimes, indicating the well-known dependence of rain physics on the immediate environment. Nevertheless, the validation results suggest how the rain determination parameters including attributed rain and threshold brightness temperature could be optimized locally before application. As others have found, the most difficult problem with satellite infrared techniques is in the detection and quantification of heavy rainfall events arising from uncertainties in discriminating non-precipitating anvil clouds from convective clouds. However, for the set of algorithms under examination here, given the sharp resolution of the validation measurements, it is evident that the CST algorithm exhibits superior performance in differentiating between non-precipitating anvil and heavy rain. Received January 4, 2002; revised March 11, 2002  相似文献   

Energy transports by ocean and atmosphere based on an entropy extremum principle. Part II: Two-dimensional transports     

B. -J. Sohn  E. A. Smith 《Meteorology and Atmospheric Physics》1994,53(1-2):61-75

Summary The maximum entropy production (MEP) principle used in Part J has been extended to separate the two-dimensional required energy transports determined from Nimbus 7 satellite net radiation measurements into atmospheric and oceanic components. In terms of the meridional component of the ocean transport vectors, results show northward ocean transports throughout the entire Atlantic ocean from southern hemisphere high latitudes to northern hemisphere polar regions, southward transports throughout the entire Indian Ocean, and poleward transports separated at approximately 10°S in the Pacific Ocean. The ocean transport patterns are consistent with well-known features concerning heat transport within the three ocean basins. However, uncertainty remains in the magnitudes of the transports. Because of the large remaining discrepancies between published estimates based on direct measurements and indirect estimates derived from energy budget methods, assessing the accuracy of the magnitudes is difficult, although there is evidence that the limited model resolution leads to synergistic biases in the North Atlantic and North Pacific. In terms of the crossmeridional energy transport component, results suggest that most of the net energy transfer in the tropics takes place within the ocean. In the southern hemisphere high latitudes, the Pacific and Indian Oceans export heat cross-meridionally to the Atlantic Ocean through the passages below Cape Horn and the Cape of Good Hope, although the magnitudes of these inter-ocean heat exchanges are small. Another important aspect of the southern hemisphere results is that poleward transports are dominated by the atmospheric component with strong zonal asymmetry. By contrast, in the northern hemisphere, atmospheric transports over the ocean are generally weaker than the corresponding southern hemisphere terms, indicating that the northern hemisphere oceans are relatively more effective in transferring heat poleward. Finally, poleward atmospheric transports over the continental areas exceed those over the ocean at equivalent latitudes as a result of the generally greater energy deficits over the land areas.With 7 Figures  相似文献   

Proceedings of the Eleventh Commonwealth Mining and Metallurgical Congress,Hong Kong, 1978: M.J. Jones (Editor). Institution of Mining and Metallurgy,London, 1979, 818 pp., £35.00, U.S.$ 77.00.     

H.Y. Sohn  J.A. Herbst  M.P. Nackowski  W.G. Pariseau 《International Journal of Mineral Processing》1980,7(3):275-277

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