• Atmosphere
• /
• v.20 no.3
• /
• pp.319-332
• /
• 2010

Sensitivity experiments of WRF model using different planetary boundary layer (PBL) and land surface model (LSM) parameterizations are evaluated for prediction of wind fields within the surface layer. The experiments were performed with three PBL schemes (YSU, Pleim, MYJ) in combination with three land surface models (Noah, RUC, Pleim). The WRF model was conducted on a nested grid from 27-km to 1-km horizontal resolution. The simulations validated wind speed and direction at 10 m and 80 m above ground level at a 1-km spatial resolution over the South Korea. Statistical verification results indicate that Pleim and YSU PBL schemes are in good agreement with observations at 10 m above ground level, while the MYJ scheme produced predictions similar to the observed wind speed at 80 m above ground level. LSM comparisons indicate that the RUC model performs best in predicting 10-m and 80-m wind speed. It is found that MYJ (PBL) - RUC (LSM) simulations yielded the best results for wind field in the surface layer. The choice of PBL and LSM parameterization will contribute to more accurate wind predictions for air quality studies and wind power using WRF.

• Korean Journal of Remote Sensing
• /
• v.34 no.1
• /
• pp.127-139
• /
• 2018

The GOCI atmospheric correction overland surfaces is essential for the time-series analysis of terrestrial environments with the very high temporal resolution. We develop an operational GOCI atmospheric correction method over land surfaces, which is rather different from the one developed for ocean surface. The GOCI atmospheric correction method basically reduces gases absorption and Rayleigh and aerosol scatterings and to derive surface reflectance from at-sensor radiance. We use the 6S radiative transfer model that requires several input parameters to calculate surface reflectance. In the sensitivity analysis, aerosol optical thickness was the most influential element among other input parameters including atmospheric model, terrain elevation, and aerosol type. To account for the highly variable nature of aerosol within the GOCI target area in northeast Asia, we generate the spatio-temporal aerosol maps using AERONET data for the aerosol correction. For a fast processing, the GOCI atmospheric correction method uses the pre-calculated look up table that directly converts at-sensor radiance to surface reflectance. The atmospheric correction method was validated by comparing with in-situ spectral measurements and MODIS reflectance products. The GOCI surface reflectance showed very similar magnitude and temporal patterns with the in-situ measurements and the MODIS reflectance. The GOCI surface reflectance was slightly higher than the in-situ measurement and MODIS reflectance by 0.01 to 0.06, which might be due to the different viewing angles. Anisotropic effect in the GOCI hourly reflectance needs to be further normalized during the following cloud-free compositing.

• Journal of Korean Society for Atmospheric Environment
• /
• v.18 no.6
• /
• pp.453-463
• /
• 2002

Prognostic meteorological model, MM5V3 (Mesoscale Model 5 Version 3) was used to assess the effects of the land-use modifications on spatial variations of temperature and wind fields in Busan during the selected period of summer season in 2000. We first examined sensitivity analysis for temperature between MM5V3 predictions and meteorological data observed at 4 AWS (Automatic Weather System) stations in Busan, which exhibited low structural and accurate errors (Mean Bias Error, MBE: 0.73, Root Mean Square Error, RMSE: 1.18 on maximum). The second part of this paper, MMSV3 simulations for the modification of land-use was performed with 1 km resolution in target domain, 46$\times$46 $\textrm{km}^2$ area around city of Busan. It was found that modification result from change of surface land-use in central urban area altered spatial distributions of temperature and wind. In particular, heat island core moved slightly to the seaward at 1300 LST. This results may imply that modification of surface land-use leads to change the thermal environments; in addition, it has a significant effect on local wind circulations and dispersions of air pollutants.

• Atmosphere
• /
• v.33 no.3
• /
• pp.307-317
• /
• 2023

This study investigates the physical mechanisms that contributed to the 2022 European record-breaking heatwave throughout May-August (MJJA). The European climate has experienced surface warming and drying in the recent decade (1979~2022) which influences the development of the 2022 European heatwave. Since its spatial pattern resembles the 2003 European heatwave which is a well-known case developed by the strong coupling of near-surface conditions to land surface processes, the 2022 heatwave is compared with the 2003 case. Understanding heatwave development is carried out by the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis version 5 (ERA5) and daily maximum surface temperature released by NCEP (National Centers for Environmental Prediction) CPC (Climate Prediction Center). The results suggest that the persistent high pressure along with clear sky tends to increase the downward shortwave radiation which leads to enhanced sensible heat flux with the land surface dryness. Terrestrial Coupling Index (TCI), a process-based multivariate metric, is employed to quantitatively measure segmented feedback processes, separately for the land, atmosphere, and two-legged couplings, which appears to the development of the 2022 heatwave, can be viewed as an expression of the recent trends, amplified by internal land-atmosphere interactions.

• Ecology and Resilient Infrastructure
• /
• v.3 no.4
• /
• pp.315-321
• /
• 2016

To identify the relationship between land use and thermal environment in an urban area, the air temperature was measured at different places of land use, and the changes of land use and air temperature were traced for 40 years in Incheon City. The relationship between land use and temperature was also investigated using satellite image data. The results of temperature measurements on a forest, a cropland (rice paddy), a bareland (school ground), and an urban area (asphalt road) from 19 to 21 August 2014 showed that air temperature was the highest on a pavement road. The temperature increased by about $1.4^{\circ}C$ ($0.035^{\circ}C/year$) for 40 years from 1975 to 2014 in Incheon. The changes in land use patterns of Incheon for the past 40 years showed that urban dry land, bareland and grassland have increased and cultivated land, wetland and forest land have decreased gradually. The land surface temperature (LST) was correlated with the normalized difference vegetation index (NDVI) and normalized difference built-up index (NDBI) extracted from Landsat satellite image. The land surface temperature was lower at higher NDVI, and higher at higher NDBI. Therefore, it is important to conserve and restore the land use of greenery, wetlands, and agricultural land in order to mitigate the heat island effect and improve the thermal environment in an urban area.

• The Journal of the Korea Contents Association
• /
• v.12 no.11
• /
• pp.482-491
• /
• 2012

Because the satellite imagery can detect the radiative heat from the surface using the thermal IR (TIR) channel, there have been many efforts to verify the relationship between the land surface temperature (LST) and urban heat island. However, the relationship between geomorphological characteristics like surface aspects and LST is relatively less studied. Therefore, the geomorphological elements, for example, surface aspects and surface slopes, are considered to evaluate their effects on the change of the surface temperature distribution using the Landsat 7 ETM+ TIR channel and the possibility of the image to detect anthropogenic heat from the surface. We found that the surface aspect is ignorable but the surface slope with the sun elevation influences on the surface temperature distribution. Also, the radiative heat from the surface to the atmosphere could not be accurately recorded by the satellite image due to the surface slope but the slope correction process used in this study could correct the surface temperature under slope condition and the slope correction, in fact, was not influenced on the average temperature of the surface. The possibility of the anthropogenic heat detection from the surface from the satellite imagery was verified as well.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.8 no.3
• /
• pp.23-27
• /
• 2008

The new conjunctive surface-subsurface flow model at a large scale was developed by using a 1-D Diffusion Wave (DW) model for surface flow interacting with the 3-D Volume Averaged Soil-moisture Transport (VAST) model for subsurface flow for the comprehensive terrestrial water and energy predictions in Land Surface Models (LSMs). A selection of numerical implementation schemes is employed for each flow component. The 3-D VAST model is implemented using a time splitting scheme applying an explicit method for lateral flow after a fully implicit method for vertical flow. The 1-D DW model is then solved by MacCormack finite difference scheme. This new conjunctive flow model is substituted for the existing 1-D hydrologic scheme in Common Land Model (CLM), one of the state-of-the-art LSMs. The new conjunctive flow model coupled to CLM is tested for a study domain around the Ohio Valley. The simulation results show that the interaction between surface flow and subsurface flow associated with the flow routing scheme matches the runoff prediction with the observations more closely in the new coupled CLM simulations. This improved terrestrial hydrologic module will be coupled to the Climate extension of the next-generation Weather Research and Forecasting (CWRF) model for advanced regional, continental, and global hydroclimatological studies and the prevention of disasters caused by climate changes.

• Journal of Environmental Science International
• /
• v.3 no.1
• /
• pp.1-9
• /
• 1994

We have Studied the characteristics of wind over Pusan coastal area in order to precisely predict surface wind having an important effect on oil spill fate using the data on surface observation of Pusan, Kimhae and Gadeogdo island which are collected during the 3 years from 1988 to 1990. We also investigated the correlation of the surface wind between Pusan, Kimhae and Gadeogdo island. In both Pusan areas and Kimhae, the land and sea breeze occurs during. the whole season except for winter. The occurrence frequency of land and sea breeze is significantly high from April to August. The correlation of surface wind between Pusan, Kimhae and Gadeogdo island surface wind is high in the daytime. The occurrence frequency of sea breeze in the Kimhae areas is higher than that in Pusan on the basis of the present criteria. For monthly occurrence, Pusan has the highest occurrence frequency of the sea breeze in August and Kimhae has in May.

• Journal of Korean Society on Water Environment
• /
• v.28 no.1
• /
• pp.137-147
• /
• 2012

Land surface temperature in ecohydrology is a variable that links surface structure to soil processes and yet its spatial prediction across landscapes with variable surface structure is poorly understood. And there are an insufficient number of soil temperature monitoring stations. In this study, a grid-based land surface temperature prediction model is proposed. Target sites are Andong and Namgang dam region. The proposed model is run in the following way. At first, geo-referenced site specific air temperatures are estimated using a kriging technique from data collected from 60 point weather stations. Then surface soil temperature is computed from the estimated geo-referenced site-specific air temperature and normalized difference vegetation index. After the model is calibrated with data collected from observed remote-sensed soil temperature, a soil temperature map is prepared based on the predictions of the model for each geo-referenced site. The daily and monthly simulated soil temperature shows that the proposed model is useful for reproducing observed soil temperature. Soil temperatures at 30 and 50 cm of soil depth are also well simulated.

• Korean Journal of Remote Sensing
• /
• v.39 no.4
• /
• pp.425-440
• /
• 2023

Monitoring water surface has become one of the most prominent areas of research in addressing environmental challenges.Accurate and automated detection of watersurface in remote sensing imagesis crucial for disaster prevention, urban planning, and water resource management, particularly for a country where water plays a vital role in human life. However, achieving precise detection poses challenges. Previous studies have explored different approaches,such as analyzing water indexes, like normalized difference water index (NDWI) derived from satellite imagery's visible or infrared bands and using k-means clustering analysis to identify land cover patterns and segment regions based on similar attributes. Nonetheless, challenges persist, notably distinguishing between waterspectralsignatures and cloud shadow or terrain shadow. In thisstudy, our objective is to enhance the precision of water surface detection by constructing a comprehensive water database (DB) using existing digital and land cover maps. This database serves as an initial assumption for automated water index analysis. We utilized 1:5,000 and 1:25,000 digital maps of Korea to extract water surface, specifically rivers, lakes, and reservoirs. Additionally, the 1:50,000 and 1:5,000 land cover maps of Korea aided in the extraction process. Our research demonstrates the effectiveness of utilizing a water DB product as our first approach for efficient water surface extraction from satellite images, complemented by our second and third approachesinvolving NDWI analysis and k-means analysis. The image segmentation and binary mask methods were employed for image analysis during the water extraction process. To evaluate the accuracy of our approach, we conducted two assessments using reference and ground truth data that we made during this research. Visual interpretation involved comparing our results with the global surface water (GSW) mask 60 m resolution, revealing significant improvements in quality and resolution. Additionally, accuracy assessment measures, including an overall accuracy of 90% and kappa values exceeding 0.8, further support the efficacy of our methodology. In conclusion, thisstudy'sresults demonstrate enhanced extraction quality and resolution. Through comprehensive assessment, our approach proves effective in achieving high accuracy in delineating watersurfaces from satellite images.