Rainfall estimation using raingages and radar — A Bayesian approach: 2. An application

In Seo and Smith (this issue), a set of estimators was built in a Bayesian framework to estimate rainfall depth at an ungaged location using raingage measurements and radar rainfall data. The estimators are equivalent to lognormal co-kriging (simple co-kriging in the Gaussian domain) with uncertain mean and variance of gage rainfall. In this paper, the estimators are evaluated via cross-validation using hourly radar rainfall data and simulated hourly raingage data. Generation of raingage data is based on sample statistics of actual raingage measurements and radar rainfall data. The estimators are compared with lognormal co-kriging and nonparametric estimators. The Bayesian estimators are shown to provide some improvement over lognormal co-kriging under the criteria of mean error, root mean square error, and standardized mean square error. It is shown that, if the prior could be assessed more accurately, the margin of improvement in predicting estimation variance could be larger. In updating the uncertain mean and variance of gage rainfall, inclusion of radar rainfall data is seen to provide little improvement over using raingage data only.     

Estimates of velocity-pressure and velocity-pressure gradient interactions in the surface layer over plant canopies

The budget equations of turbulent kinetic energy and shear stress contain interaction terms of velocity-pressure and velocity-pressure gradient. These terms were estimated in the surface layer using the air pressure observed at the surface and wind velocity components over plant canopies. The magnitude of the pressure interaction terms was significantly large; it was not negligible compared with the production terms in each budget equation. The present results obtained over a rough surface also confirmed previous results that pressure terms play an important role in the turbulent kinetic energy budgets and the shear stress budget. The height dependency of nondimensional pressure terms versus (z - d)/z ₀ was not clear.     

Turbulent transport of scalar quantities within and above a paddy field

An experiment was conducted to study turbulent transport processes of scalar quantities within and above a rice plant canopy. A sonic anemometer-thermometer and a Lyman- humidiometer were used to measure the turbulent fluxes of sensible and latent heat and related turbulence statistics within a paddy field. The sensible and latent heat fluxes measured at two heights within and above the plant canopy showed that the upper layer of this plant canopy was an active source region and that the source strength of sensible and latent heat depended on the solar radiation and physiology of rice plants. Analysis of joint probability distributions of w and T and of w and q within this plant canopy showed that downdrafts were remarkably efficient for upward transport of sensible and latent heat in the daytime. The vertical fluxes of temperature and humidity variance were also divergent from the upper layer of plant canopies. The power spectra of temperature and humidity within the plant canopy decreased rapidly in the high frequency range, compared with the - 2/3 law relationship of nS(n) vs log n observed above plant canopies.     

Atmospheric carbon dioxide variations at coastal site, Shibukawa, in Seto Inland Sea, Japan

Summary Four years of measurements (1980–83) of carbon dioxide at the northern coast site, Shibukawa, are presented. The data reveal well defined diurnal and seasonal variations. The amplitude of the daily carbon dioxide variation is about 30 ppm during the colder season (January–March; November–December), and about 60 ppm during the warmer season (April–October). The seasonal variation of daily minimum concentration of carbon dioxide has a maximum in the middle of summer (July–September) and a minimum in the winter months. This variation does not correspond to that expected from vegetation activity. The summer peak in carbon dioxide concentration seems to be inherent features at the coast site, Shibukawa; it is probably due to less activity of the vertical mixing under stable stratification of the air layer prevailing throughout the day. The year-to-year comparison of minimums in the winter months reveals an average annual increase of the carbon dioxide content of 6 ppm/year, which is much greater than 1.5 ppm/year observed in the troposphere over Japan [1]. This indicates that the carbon dioxide concentration and its variations at Shibukawa station represent the local scale values rather than the large scale one. The horizontal distribution of carbon dioxide concentration, measured over sea surface near Shibukawa station, also suggests the existence of many patches of high concentration of carbon dioxide due to the local point sources related to the human activity such as ships and industries distributed at the coast site.

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Variationen des atmosphärischen CO₂ bei Shibukawa im Küstengebiet des Inlandsees Seto in Japan

Zusammenfassung Es werden Ergebnisse über Tages- und Jahresgänge von vierjährigen Messungen (1980–83) des CO₂ bei Shibukawa an der nördlichen Küste des Sees vorgelegt. Die Amplitude des Tagesganges beträgt in der kalten Jahreszeit ungefähr 30 ppm und in der warmen Jahreszeit ungefähr 60 ppm. Im Jahresgang des täglichen Minimums des CO₂ fällt das Maximum auf den Sommer und das Minimum auf Wintermonate. Dies entspricht nicht der aus der Aktvität der Vegetation zu erwartenden Variation. Das Sommermaximum scheint eine Besonderheit der Lage von Shibukawa an der Küste zu sein und ist wahrscheinlich auf die zu geringe vertikale Durchmischung bei der tagsüber dort vorherrschenden stabilen Schichtung zurückzuführen. Der Vergleich der Minima der Wintermonate von Jahr zu Jahr läßt eine Zunahme um 6 ppm pro Jahr erkennen, die bedeutend größer ist als die Zunahme um 1,5 ppm pro Jahr in der Troposphäre über Japan [ 1 ]. Dies weist darauf hin, daß die CO₂-Konzentration und ihre Variationen in Shibukawa eher lokale als großräumige Werte darstellen.Die über der Seeoberfläche in der Nähe von Shibukawa gemessene Verteilung der CO₂-Konzentrationen zeigt viele Stellen mit hoher CO₂-Konzentration, die auf lokale Punktquellen menschlicher Aktivität wie auf Schiffe und auf an der Küste verteilte Industrien hinweisen.

     

Impact of UV-A radiation on erythemal UV and UV-index estimation over Korea

Because total UV(TUV) in the UV-A region is 100 times higher than in the UV-B region,UV-A is a considerable component when calculating erythemal UV(EUV) and UV-index.The ratio of EUV to TUV in the UV-A value [EUV(A)/TUV(A)]is investigated to convert the EUV(A) from TUV(A) for broadband observation. The representative value of EUV(A)/TUV(A),from the simulation study,is 6.9 × 10-4,changing from 6.1 × 10-4to 7.0 × 10-4as aerosol optical depth,total ozone and solar zenith angle change. By adopting the observational data of EUV(B) and TUV(A) from UV-biometer measurements at Yonsei University [(37.57?N,126.95?E),84 m above sea level],the EUV irradiance increases to 15% of EUV(B) due to the consideration of EUV(A) from the data of TUV(A) observation. Compared to the total EUV observed from the Brewer spectrophotometer at the same site,the EUV(B) from the UV-biometer observes only 95% of total EUV,and its underestimation is caused by neglecting the effect of UV-A. However,the sum of EUV(B) and EUV(A) [EUV(A+B)] from two UV-biometers is 10% larger than the EUV from the Brewer spectrophotometer because of the spectral overlap effect in the range 320–340nm. The correction factor for the overlap effect adjusts 8% of total EUV.     

Evaluation of a regional ocean reanalysis system for the East Asian Marginal Seas based on the ensemble Kalman filter

Ocean Science Journal - This study introduces the East Asian Marginal Seas (EAMS) reanalysis system and evaluates its products from 1982 to 2006. The EAMS reanalysis system consists of an ocean...     

Development of the Operational Oceanographic System of Korea

Ocean Science Journal - The Korea Operational Oceanographic System (KOOS) was developed at the Korea Institute of Ocean Science and Technology (KIOST) to produce real-time forecasting and...     

Experimental study on the aseismic capacity of a wooden house using shaking table

The aseismic capacity of a typical Korean wooden house built using traditional construction methods is quantitatively estimated. Tenon joints were used in wooden frames. Two 1:4 scale models were tested for rock and soil foundation conditions. Scaled real earthquake time histories were input for the tests. The natural frequency and modal damping ratio of the wooden house in the elastic range were 1·66 Hz and 7 per cent, respectively. The Peak Ground Acceleration (PGA) at the collapse of the house at the soil site was 0·25g, whereas PGA for moderate damage at the rock site was 0·6g. A significant reduction in acceleration response and increase in displacement response was observed for rock and soil foundation conditions, respectively. The wooden house studied is much more vulnerable at soil sites than at rock sites due to the rich low-frequency contents of the input motion and the flexible characteristics of the wooden house. Non-linear dynamic analyses using the modified Double-Target model were compared with test results. The modified Double-Target model appropriately simulates the non-linear inelastic behaviour of a wooden house with tenon joints. Copyright © 1999 John Wiley & Sons, Ltd.     

Petrology, geochronology and tectonic implications of Mesozoic high Ba–Sr granites in the Haemi area, Hongseong Belt, South Korea

Collision between the North and South China continental blocks began in the Korean peninsula during the Permian (290–260 Ma). The Haemi area in the Hongseong collision belt (proposed as the eastern extension in South Korea of the Dabie–Sulu collision zone of China) within the Gyeonggi Massif comprises post-collisional high Ba–Sr granite with intermediate enclaves that intruded into the Precambrian rocks. The intermediate enclaves have a shoshonitic affinity whereas the granite is a high-K calc-alkaline variety. The chondrite-normalized rare earth element (REE) pattern with relative enrichment of LREE over HREE and absence of a significant negative Eu anomaly typifies both enclaves and granite. Geochemical similarities of enclaves and granite are attributed to the involvement of enriched mantle sources in their genesis. However, dominant crustal components were involved in the formation of high Ba–Sr granites. A granite crystallization age of 233 ± 2 Ma was obtained from SHRIMP U–Pb zircon dating. This age is slightly younger than the Triassic collision event in the Hongseong Belt. Geochemical data, U–Pb zircon age, and regional tectonics indicate that the Haemi high Ba–Sr granite formed in a post-collisional tectonic environment. A Mesozoic post-collisional lithospheric delamination model can account for the genesis of high Ba–Sr granite in the Haemi area.