Derivation of regression coefficients for sea surface temperature retrieval over East Asia     

Myoung-Hwan AHN  Eun-Ha SOHN  Byong-Jun HWANG  Chu-Yong CHUNG  Xiangqian WU 《大气科学进展》2006,23(3):474-486

Among the regression-based algorithms for deriving SST from satellite measurements, regionally optimized algorithms normally perform better than the corresponding global algorithm. In this paper,three algorithms are considered for SST retrieval over the East Asia region (15°-55°N, 105°-170°E),including the multi-channel algorithm (MCSST), the quadratic algorithm (QSST), and the Pathfinder algorithm (PFSST). All algorithms are derived and validated using collocated buoy and Geostationary Meteorological Satellite (GMS-5) observations from 1997 to 2001. An important part of the derivation and validation of the algorithms is the quality control procedure for the buoy SST data and an improved cloud screening method for the satellite brightness temperature measurements. The regionally optimized MCSST algorithm shows an overall improvement over the global algorithm, removing the bias of about -0.13℃ and reducing the root-mean-square difference (rmsd) from 1.36℃ to 1.26℃. The QSST is only slightly better than the MCSST. For both algorithms, a seasonal dependence of the remaining error statistics is still evident. The Pathfinder approach for deriving a season-specific set of coefficients, one for August to October and one for the rest of the year, provides the smallest rmsd overall that is also stable over time.  相似文献   

Simplified model for predicting the onset of parametric rolling     

S. Surendran  S.K. Lee  K.H. Sohn   《Ocean Engineering》2007,34(3-4):630-637

The world container fleet shows the fastest growth of any ship type. The infrastructure for loading and unloading container ships are also growing in many ports around the world. Such a trend is due to the fact that the containerized transportation is becoming more and more attractive due to many factors. The increasing demand in container transportation is met by use of more number of container ships including Post-Panamax and Malacca-max containers. Loss of containers in seas and accidents of container vessels are reported from many parts of seas. New generation containers are severely hit by parametric rolling. Pure loss of stability, due to exponential increase of roll in either broaching—to or head sea conditions, is called parametric rolling, is subjected to rigorous investigation by many researchers. Algebraic expression based on well known Duffing's method is proposed for solutions in parametric rolling. The variation in GM and damping values from trough to crest conditions associated with bow flare immersion and emergence in head sea conditions with pitch resonance with the heading waves are said to be the prime reason for parametric rolling. A simple model to predict the beginning of parametric rolling is described in this paper.  相似文献   

Prediction of Monthly Mean Surface Air Temperature in a Region of China   总被引：3，自引：0，他引：3  

Jeong-Hyeong LEE  Keon-Tae SOHN 《大气科学进展》2007,24(3):503-508

In conventional time series analysis, a process is often modeled as three additive components： linear trend, seasonal effect, and random noise. In this paper, we perform an analysis of surface air temperature in a region of China using a decomposition method in time series analysis. Applications to the National Centers for Environmental Prediction/the National Center for Atmospheric Research （NCEP/NCAR） Collaborative Reanalysis data in this region of China are discussed. The main finding was that the surface air temperature trend estimated for January 1948 to February 2006 was not statistically significant at 0.5904℃ （100 yr）^-1. Forecasting aspects are also considered.  相似文献   

Prediction of Typhoon Tracks Using Dynamic Linear Models     

Keon-Tae SOHN  H. Joe KWON  Ae-Sook SUH 《大气科学进展》2003,20(3):379-384

This paper presents a study on the statistical forecasts of typhoon tracks. Numerical models have their own systematic errors, like a bias. In order to improve the accuracy of track forecasting, a statistical model called DLM (dynamic linear model) is applied to remove the systematic error. In the analysis of typhoons occurring over the western North Pacific in 1997 and 2000, DLM is useful as an adaptive model for the prediction of typhoon tracks.  相似文献   

The geography of mercury and PCBs in North Carolina's local seafood     

Freitag A  Sohn N  Hooper M  Rittschof D 《Marine pollution bulletin》2012,64(7):1330-1338

Mercury and PCBs are used by non-governmental organizations and federal agencies to inform seafood safety recommendations. Pollution dynamics suggest recommendations on the national scale may be too large to be accurate. We tested softshell and hardshell blue crab, white and pink shrimp, oysters, clams, spot, and mullet from fishers in each of the three North Carolina fishery districts. We measured mercury using EPA method 7473 and PCBs using a commercially available ELISA kit. Over 97% of samples were below the Environmental Protection Agency levels of concern for both mercury and PCBs. Mercury and PCBs have different spatial dynamics, but both differ significantly by water body, suggesting that seafood safety recommendations should occur by water body instead of at the national scale. This finding supports previous research suggesting that differences in water chemistry, terrestrial influence, and flushing time in a particular water body control the contaminant load in locally resident species.  相似文献   

Deep pooling of low degree melts and volatile fluxes at the 85°E segment of the Gakkel Ridge: Evidence from olivine-hosted melt inclusions and glasses     

Alison M. Shaw  Mark D. Behn  Susan E. Humphris  Robert A. Sohn  Patricia M. Gregg 《Earth and Planetary Science Letters》2010,289(3-4):311-322

We present new analyses of volatile, major, and trace elements for a suite of glasses and melt inclusions from the 85°E segment of the ultra-slow spreading Gakkel Ridge. Samples from this segment include limu o pele and glass shards, proposed to result from CO₂-driven explosive activity. The major element and volatile compositions of the melt inclusions are more variable and consistently more primitive than the glass data. CO₂ contents in the melt inclusions extend to higher values (167–1596 ppm) than in the co-existing glasses (187–227 ppm), indicating that the melt inclusions were trapped at greater depths. These melt inclusions record the highest CO₂ melt concentrations observed for a ridge environment. Based on a vapor saturation model, we estimate that the melt inclusions were trapped between seafloor depths (～ 4 km) and ～ 9 km below the seafloor. However, the glasses are all in equilibrium with their eruption depths, which is inconsistent with the rapid magma ascent rates expected for explosive activity. Melting conditions inferred from thermobarometry suggest relatively deep (25–40 km) and cold (1240°–1325 °C) melting conditions, consistent with a thermal structure calculated for the Gakkel Ridge. The water contents and trace element compositions of the melt inclusions and glasses are remarkably homogeneous; this is an unexpected result for ultra-slow spreading ridges, where magma mixing is generally thought to be less efficient based on the assumption that steady-state crustal magma chambers are absent in these environments. All melts can be described by a single liquid line of descent originating from a pooled melt composition that is consistent with the aggregate melt calculated from a geodynamic model for the Gakkel Ridge. These data suggest a model in which deep, low degree melts are efficiently pooled in the upper mantle (9–20 km depth), after which crystallization commences and continues during ascent and eruption. Based on our melting model and the assumption that CO₂ is perfectly incompatible, we show that the highest CO₂ concentrations of the melt inclusions (～ 1600 ppm) are consistent with the calculated CO₂ concentrations of primary undegassed melts. The highest measured CO₂/Nb ratio (443) of Gakkel Ridge melt inclusions predicts a mantle CO₂ content of 134 ppm and would result in a global ridge flux of 2.0 × 10¹² mol CO₂/yr.  相似文献   

Post-flight radiometric calibration of the Korean geostationary satellite COMS meteorological imager     

Bo-Ra Kim  Seung-Hee Ham  Dohyeong Kim  Byung-Ju Sohn 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(2):201-210

The first Korean geostationary satellite, the Communication, Ocean, Meteorological Satellite (COMS) carries the Meteorological Imager (MI) that measures solar radiance at 0.675 μm and infrared (IR) brightness temperatures at four spectral bands centered at 3.8, 6.7, 10.8, and 12.0 μm. This study reports the calibration status of the COMS MI solar and four IR channels, based mainly on a comparison with Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. The results obtained from four months of COMS MI solar channel measurements demonstrate that the solar channel has a dark bias of about 9–10%. On the other hand, the four IR channels appear to be well-calibrated as evidenced by a high correlation and near-unity slope between COMS and MODIS data. Nevertheless, existing biases of tenths of a kelvin are still considered to be substantial. Overall, the interpretation of COMS-derived meteorological products should take into account some uncertainty caused by possible calibration errors.  相似文献   

Mechanisms driving polymagmatic activity at a monogenetic volcano, Udo, Jeju Island, South Korea   总被引：3，自引：1，他引：2  

Marco Brenna  Shane J. Cronin  Ian E. M. Smith  Young Kwan Sohn  Karoly Németh 《Contributions to Mineralogy and Petrology》2010,160(6):931-950

High-resolution, stratigraphically ordered samples of the Udo tuff cone and lava shield offshore of Jeju Island, South Korea, show complex geochemical variation in the basaltic magmas that fed the eruption sequence. The eruption began explosively, producing phreatomagmatic deposits with relatively evolved alkali magma. The magma became more primitive over the course of the eruption, but the last magma to be explosively erupted had shifted back to a relatively evolved composition. A separate sub-alkali magma batch was subsequently effusively erupted to form a lava shield. Absence of weathering and only minor reworking between the tuff and overlying lava implies that there was no significant time break between the eruptions of the two magma batches. Modelling of the alkali magma suggests that it was generated from a parent melt in garnet peridotite at c. 3 to 3.5 GPa and underwent mainly clinopyroxene + olivine ± spinel fractionation at c. 1.5 to 2 GPa. The sub-alkali magma was, by contrast, generated from a chemically different peridotite with residual garnet at c. 2.5 GPa and evolved through olivine fractionation at a shallower level compared to its alkali contemporary. The continuous chemostratigraphic trend in the tuff cone, from relatively evolved to primitive and back to evolved, is interpreted to have resulted from a magma batch having risen through a single dyke and erupted the batch’s head, core and margins, respectively. The alkali magma acted as a path-opener for the sub-alkali magma. The occurrence of the two distinct batches suggests that different magmatic systems in the Jeju Island Volcanic Field have interacted throughout its history. The polymagmatic nature of this monogenetic eruption has important implications for hazard forecasting and for our understanding of basaltic field volcanism.  相似文献