• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.64.3-64.3
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• 2015

We have developed a set of daily solar flare peak flux forecast models for strong flares using multiple linear regression and artificial neural network methods. We consider input parameters as solar activity data from January 1996 to December 2013 such as sunspot area, X-ray flare peak flux and weighted total flux of previous day, and mean flare rates of McIntosh sunspot group (Zpc) and Mount Wilson magnetic classification. For a training data set, we use the same number of 61 events for each C-, M-, and X-class from Jan. 1996 to Dec. 2004, while other previous models use all flares. For a testing data set, we use all flares from Jan. 2005 to Nov. 2013. The best three parameters related to the observed flare peak flux are weighted total flare flux of previous day (r = 0.51), X-ray flare peak flux (r = 0.48), and Mount Wilson magnetic classification (r = 0.47). A comparison between our neural network models and the previous models based on Heidke Skill Score (HSS) shows that our model for X-class flare is much better than the models and that for M-class flares is similar to them. Since all input parameters for our models are easily available, the models can be operated steadily and automatically in near-real time for space weather service.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.386-391
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• 1997

It is important to understand correctly a CHF under low flow condition for the purpose of enhancing the reactor safety and performance in the LWRs. The CHF experiments have been carried out for an internally heated vertical annulus in RCS loop facility. The experimental conditions cover ranges of pressure from 1.82 to 12.08 MPa, mass flux from 300 to 550kg/$m^2$. s and inlet subcooling of 210kJ/kg. The CHF data decrease with increasing pressure at high value of mass flux. For mass flux of about 300kg/$m^2$. s, the CHF rue little influenced by pressure. The CHF data are correlated well by using the dimensionless heat flux and dimensionless mass flux for a fixed inlet subcooling except the data group of 12.08 MPa. It seems that the Doerffer correlation and Katto correlation overestimate the CHF for low pressure and lower value of mass flux within this experimental ranges. The Bowling correlation gives a better prediction than the other two correlations.

• Ocean and Polar Research
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• v.43 no.1
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• pp.15-30
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• 2021

In this study, using 16 ORA-IP (Ocean Reanalysis Intercomparison Project) data, we investigated spatial and temporal changes of net surface heat flux in the East Asian seas and presented a new ensemble net surface heat flux index. The ensemble net surface heat flux index is produced considering the data distribution and the standard deviation of each ORA-IP. From the correlation analysis with air temperature averaged over the Korean Peninsula, ensemble net heat flux around the Korea Strait shows the highest correlation (0.731) with a 3 month time lag. For the correlation study regarding precipitation over the Korean Peninsula, it also shows significant correlation especially in winter and spring seasons. Similar results are also found in comparison with climate indices (AO, PDO, and NINO3.4), but ensemble net surface heat flux data in winter season reveals the strongest correlation patterns especially with winter temperature and spring precipitation.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.96.2-96.2
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• 2013

The solar images are taken by the CCD detectors of the Sun monitoring satellites. The solar images are constructed after removing the traces of cosmic rays on the raw CCD data files. Thus, while applying the method of removing the cosmic rays traces, we can estimate the cosmic rays flux by counting the number of traces. The cosmic ray flux in the steady state might be the sum of the solar and galactic cosmic rays. However, the abrupt change in the flux could be assumed to be originated from the Sun. Therefore, we can identify the solar origins of the sudden solar cosmic ray flux changes from the phenomena shown in the processed solar images taken by SOHO/EIT. As the results, the estimated cosmic ray flux in the steady state is the anti-correlated with sunspot numbers, which shows the minima in cosmic ray flux at the solar cycle maxima defined by the sunspot numbers. The profiles of estimated solar cosmic ray associated with the ground level enhancements have the significant increase in the cosmic ray flux with good correlation. Thus, the solar images are valuable data useful in estimating the solar cosmic ray long term and transient flux variations.

• Journal of Environmental Science International
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• v.10 no.1
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• pp.1-8
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• 2001

This study was carried out estimating the dry deposition flux of $SO_2$at eight urban areas in Korea during one year of 1996. To calculate the deposition flux, deposition velocities were calculated by turbulence parameters estimated from routine meteorological data. Also, hourly averaged $SO_2$concentrations which calculated from air pollution monitoring data of each city were used. The dry deposition velocities were mostly higher in the coastal areas than the other areas, which would be caused by relatively strong wind. And, they were high in the daytime because of turbulence activities. The deposition flux of $SO_2$is mainly related to the atmospheric concentration. The annual average $SO_2$concentration and the deposition flux were 22.62ppb and 1510.52g/$\textrm{km}^2$/hr at Pusan respectively. Also, the flux was higher in winter than other season, which was a significant contribution of exhausted fuel for heating. While the deposition velocity was high to 0.688cm/sec at Yosu in case of strong wind and small cloud cover, the deposition flux was high to 1597.4g/$\textrm{km}^2$/hr at Pusan in case of weak wind and small cloud cover.

• Journal of Fisheries and Marine Sciences Education
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• v.17 no.2
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• pp.209-217
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• 2005

The energy balance of the surface layer of the water (the Yellow Sea, the East China Sea and the East Sea) was examined using satellite data. Variations of the net heat flux were similar to those of the latent heat flux which was more intensive than the sensible heat flux. The sensible heat flux was affected the difference between the sea surface temperature and the air temperature and was less important over the Yellow Sea. The maximum of the latent heat flux occurred in autumn when the air is drier and the wind is stronger. The shortwave radiation flux decreased with the latitude and depended on the cloudiness as the longwave radiation flux does. Annual variations of heat fluxes show that the latent heat flux was more intensive over the East China Sea than the East Sea and the Yellow Sea, while the spatial differences of the other heat fluxes were weak.

• Journal of The Korean Astronomical Society
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• v.39 no.4
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• pp.151-155
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• 2006

Long slit spectrometers are widely used in optical and infrared bands in astronomy. Absolute flux calibration for extended sources, however, is not straightforward, because a portion of the radiation energy from a flux calibration star is blocked by the narrow slit width. Assuming that the point spread function(PSF) of the star is circularly symmetric, we develop a robust method to extrapolate the detected stellar flux to the unobscured flux using the measured PSF along the slit-length direction. We apply this method to our long slit data and prove that the uncertainty of the absolute flux calibration is less than a few percents.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.1
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• pp.19-26
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• 2009

The standardization of eddy-covariance data processing is essential for the analysis and synthesis of vast amount of data being accumulated through continuous observations in various flux measurement networks. End users eventually benefit from the open and transparent standardization protocol by clear understanding of final products such as evapotranspiration and gross primary productivity. In this paper, we briefly introduced KoFlux efforts to standardize data processing methodologies and then estimated uncertainties of surface fluxes due to different processing methods. Based on our scrutiny of the data observed at Gwangneung KoFlux site, net ecosystem exchange and ecosystem respiration were sensitive to the selection of different processing methods. Gross primary production, however, was consistent within errors due to cancellation of the differences in NEE and Re, emphasizing that independent observation of ecosystem respiration is required for accurate estimates of carbon exchange. Nocturnal soil evaporation was small and thus the annually integrated evapotranspiration was not sensitive to the selection of different data processing methods. The implementation of such standardized data processing protocol to AsiaFlux will enable the establishment of consistent database for validation of models of carbon cycle, dynamic vegetation, and land-atmosphere interaction at regional scale.

• Ocean and Polar Research
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• v.26 no.2
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• pp.145-154
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• 2004

Surface energy and $CO_2$ fluxes have been measured over an ocean at Ieodo Ocean Research Station of KORDI since May 2003. Eddy covariance technique, which is a direct flux measurement, is used to quantitatively understand the interaction between the ocean surface and the atmospheric boundary layer. Although fluxes were continuously measured during the period from May 2003 to February 2004, the quality control of these data yielded <20% of data retrieval. The atmospheric stability did not show any distinct dirunal patterns and remained near-neutral to stable from May to June but mostly unstable during fall and winter in 2003. Sensible heat flux showed a good correlation with the difference between the sea water temperature and the air temperature. The maximum fluxes of sensible heat and latent heat were $120Wm^{-2}$ and $350Wm^{-2}$ respectively, with an averaged Bowen ratio of 0.2. The ocean around the tower absorbed $CO_2$ from the atmosphere and the uptake rates showed seasonal variations. Based our preliminary results, the daytime $CO_2$ flux was steady with an average of $-0.1 mgCO_2m^{-2}s^{-1}$ in summer and increased in winter. The nighttime $CO_2$ uptake was greater and fluctuating, reaching up to $-0.1 mgCO_2m^{-2}s^{-1}$ but these data require further examination due to weak turbulent mixing at nighttime. The magnitude of $CO_2$ flux was positively correlated with the half hourly changes in horizontal mean wind speed. Due to the paucity of quality data, further data collection is needed for more detailed analyses and interpretation.

• Atmosphere
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• v.29 no.5
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• pp.567-583
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• 2019

In this study, the high-resolution numerical simulations considering detailed anthropogenic heat, albedo, emission and roughness length are analyzed by using single layer Urban Canopy Model (UCM) in Weather Research Forecast (WRF). For this, improved urban parameter data for Seoul Metropolitan Area (SMA) was collected from global data. And then the parameters were applied to WRF-UCM model after it was processed into 2-dimensional topographical data. The 6 experiments were simulated by using the model with each parameter and verified against observation from Automated Weather Station (AWS) and flux tower for the temperature and sensible heat flux. The data for sensible heat flux of flux towers on Jungnang and Bucheon, the temperature of AWS on Jungnang, Gangnam, Bucheon and Neonggok were used as verification data. In the case of summer, the improvement of simulation by using detailed anthropogenic heat was higher than the other experiments in sensible flux simulation. The results of winter case show improved in all simulations using each advanced parameters in temperature and sensible heat flux simulation. Improvement of urban parameters in this study are possible to reflect the heat characteristics of urban area. Especially, detailed application of anthropogenic heat contributed to the enhancement of predicted value for sensible heat flux and temperature.