• Sleep Medicine and Psychophysiology
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• v.21 no.2
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• pp.51-60
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• 2014

A 'circadian rhythm' is a self-sustained biological rhythm (cycle) that repeats itself approximately every 24 hours. Circadian rhythms are generated by an internal clock, or pacemaker, and persist even in the absence of environmental time cues, collectively termed 'zeitgebers.' Although organisms generate circadian rhythms internally, they are entrained by environmental stimuli, particularly the light-dark cycle. Measurement of the endogenous melatonin rhythm provides relatively reliable surrogate way of assessing the timing of the internal circadian clock. Also, core body temperature and cortisol can be used as markers of circadian rhythms. The sleep-wake cycle, body temperature, and melatonin rhythm have a stable internal phase relationship in humans and other diurnal species. They play an important role in controlling daily behavioral rhythms including task performance, blood pressure, and synthesis and secretion of several hormones. In this review, we address not only the properties, methods of measurement, and markers of circadian rhythms, but also the physiological and psychological importance of human circadian rhythms.

• Atmosphere
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• v.17 no.2
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• pp.147-157
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• 2007

A weekend effect has been investigated in diurnal temperature range (DTR) for Seoul in Korea using 50-year (1955 ~ 2005) surface measurements of maximum and minimum temperatures, and particle mass concentrations (PM10). The minimum temperature increases by 0.42K per decade, 2 times faster than the maximum temperature during 1955 to 2005, for rapid urbanization has occurred in Seoul. The weekend effect, which is defined as the DTR for Sunday minus the average DTR for Tuseday through Thursday, can be as large as +0.08 K for the recent 20-year period relative to 0.01K for 1955 to 1975. Especially the wintertime DTR tends to have a remarkable positive weekend effect (+0.17K), that is, larger DTR on Sunday compared to weekdays, which seems to be associated with increased maximum temperature and thus an increase in DTR. This result could be explained by relative differences in PM10 concentration between Sunday and weekdays (Tuesday through Thursday), such that PM10 concentration on Sundays appears to be systematically lower about 12% than on weekdays. The annually average weekend DTR increases by 0.2K with $10{\mu}gm^{-3}$ decrease in PM10 concentration in comparison with weekdays. The results could be possible evidence of an anthropogenic link to DTR, one of climate important indicators, since no meteorological phenomenon is supposed to occur over a 7 day cycle.

• Atmosphere
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• v.17 no.2
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• pp.115-123
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• 2007

The present study uses the GOES IR brightness temperature to examine the temporal and spatial variability of cloud activity over the region $25^{\circ}N-45^{\circ}N$, $105^{\circ}E-135^{\circ}E$ and analyzes the coherence of eastern Asian summer season rainfall in Weather Research and Forecast (WRF) model. Time-longitude diagram of the time period from June to July 2005 shows a signal of eastward propagation in the WRF model and convective index derived from GOES IR data. The rain streaks in time-latitude diagram reveal coherence during the experiment period. Diurnal and synoptic scales are evident in the power spectrum of the time series of convective index and WRF rainfall. The diurnal cycle of early morning rainfall in the WRF model agrees with GOES IR data in the Korean Peninsula, but the afternoon convection observed by satellite observation in China is not consistent with the WRF rainfall which is represented at the dawn. Although there are errors in strength and timing of convection, the model predicts a coherent tendency of rainfall occurrence during summer season.

• Water Engineering Research
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• v.3 no.1
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• pp.31-44
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• 2002

The effect of diurnal cycle, intermittent visit of observation satellite, sensor installation, partial coverage of remote sensing, heterogeneity of soil properties and precipitation to the soil moisture estimation error were analyzed to present the global sampling strategy of soil moisture. Three models, the theoretical soil moisture model, WGR model proposed Waymire of at. (1984) to generate rainfall, and Turning Band Method to generate two dimensional soil porosity, active soil depth and loss coefficient field were used to construct sufficient two-dimensional soil moisture data based on different scenarios. The sampling error is dominated by sampling interval and design scheme. The effect of heterogeneity of soil properties and rainfall to sampling error is smaller than that of temporal gap and spatial gap. Selecting a small sampling interval can dramatically reduce the sampling error generated by other factors such as heterogeneity of rainfall, soil properties, topography, and climatic conditions. If the annual mean of coverage portion is about 90%, the effect of partial coverage to sampling error can be disregarded. The water retention capacity of fields is very important in the sampling error. The smaller the water retention capacity of the field (small soil porosity and thin active soil depth), the greater the sampling error. These results indicate that the sampling error is very sensitive to water retention capacity. Block random installation gets more accurate data than random installation of soil moisture gages. The Walnut Gulch soil moisture data show that the diurnal variation of soil moisture causes sampling error between 1 and 4 % in daily estimation.

• Molecules and Cells
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• v.28 no.5
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• pp.417-422
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• 2009

Mitogen activated protein kinase (MAPK) are known to get activated during various stress signals and transduce the message from the cell membrane to the nucleus for appropriate cellular reorganization. Though, a certain basal activity of MAPK is often observed in the control plants. Prolonged exposure of rice plants to lowered or elevated temperature exhibited a rhythm in the activation of MAPKs. We analyzed existence of a possible endogenous rhythm in the activity of MAPKs in rice plants. The plants growing at constant temperature entrained in 16/8 h day-night cycle showed diurnal rhythm in activity. When the activation of MAPK was tested under continuous conditions by shifting plants to continuous darkness for a period of 72 h, the periodic rhythm persisted and followed a circadian pattern. Analysis of the transcripts of group A, B and C members of MAPKs under above conditions by quantitative real time PCR revealed that the members of group C exhibit periodic rhythm. Our data indicates that the MAP kinase activity in rice follows rhythmic expression in a circadian manner.

• Journal of Astronomy and Space Sciences
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• v.37 no.1
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• pp.19-27
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• 2020

Pc1 pulsations are important to consider for the interpretation of wave-particle interactions in the Earth's magnetosphere. In fact, the wave properties of these pulsations change dynamically when they propagate from the source region in the space to the ground. A detailed study of the wave features can help understanding their time evolution mechanisms. In this study, we statistically analyzed Pc1 pulsations observed by a Bohyunsan (BOH) magneto-impedance (MI) sensor located in Korea (L = 1.3) for ~one solar cycle (November 2009-August 2018). In particular, we investigated the temporal occurrence ratio of Pc1 pulsations (considering seasonal, diurnal, and annual variations in the solar cycle), their wave properties (e.g., duration, peak frequency, and bandwidth), and their relationship with geomagnetic activities by considering the Kp and Dst indices in correspondence of the Pc1 pulsation events. We found that the Pc1 waves frequently occurred in March in the dawn (1-3 magnetic local time (MLT)) sector, during the declining phase of the solar cycle. They generally continued for 2-5 minutes, reaching a peak frequency of ~0.9 Hz. Finally, most of the pulsations have strong dependence on the geomagnetic storm and observed during the early recovery phase of the geomagnetic storm.

• Journal of the Korean earth science society
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• v.25 no.6
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• pp.474-483
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• 2004

This paper analyzed the characteristics of daily ozone variations over Kangreung and Wonju. It was found that the diurnal cycle of ozone over Wonju has a primary ozone peak in the afternoon and a minimum around sunrise, which is a typical diurnal ozone cycle observable in the urban area. However, the cycle over Kangreung shows a primary peak in the afternoon and secondary peak around 3 a.m. The amounts of ozone in the secondary peak is occasionally higher than that in the primary peak. This nocturnal ozone peak is frequently observed year-round, and the highest frequency and extent are observed in spring. The possible cause of this nocturnal ozone increase was investigated using meteorological parameters and the HYSPLIT trajectory model. It was found that the nocturnal ozone peak is highly correlated with strong wind speed, which has led to positive temperature anomaly. The trajectory model revealed that when the secondary peak occurred, the air was originated from the west and a sinking motion subsequently followed. These findings suggested that when the westerly wind is strongest in spring, the polluted airs from urban areas are transported to the upper boundary layer over Kangreung area. In the case of strong wind during the night, nocturnal ozone peaks were produced by active vertical mixing between lower boundary and upper boundary layers.

• Journal of The Geomorphological Association of Korea
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• v.19 no.3
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• pp.109-121
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• 2012

Rock-surface temperatures were observed at a trachytic lava dome, called as Baeknokdam Northwest Face, in the summit area of Mt. Halla, Jeju Island, to examine the frequency and occurrence season of freeze-thaw cycles and the rate of temperature changes during a freezing period. Long-term measurements were recorded over 18 months from November 2006 to April 2008, at a 1-hour logging interval and rock depth of 1.5 cm. Both diurnal freeze-thaw cycles and effective freeze-thaw cycles appear in larger numbers on a south-facing rock face than a north-facing rock face. The diurnal cycles were dominantly observed on February and March for the south face and on November and April for the north face, respectively. The annual freeze-thaw cycles were confirmed in terms of the presence of seasonal freezing periods lasting from mid-November to mid-April for the south face and from early-November to late-April for the north face, respectively. The rate of decreasing temperatures during the seasonal freezing periods is larger on the north face than the south face. Notwithstanding the lower numbers of freeze-thaw events, the north face experiences a higher frost intensity since the number of hours below $-3^{\circ}C$ is larger on the north face than the south face. The number of freeze-thaw events and the duration of days with continuous sub-zero rock temperatures largely depend on the solar radiation controlled by the aspect of the monitored rock surfaces, and thus the high-frequency short-term frost cycle dominantly appears on the south face and the annual frost cycle on the north face, respectively.

• Radiation Oncology Journal
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• v.3 no.2
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• pp.169-174
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• 1985

The mouse is one of the most popular experimental animal which has wide variation of strains, diet, environment, breeding technique, and diurnal cycle. Total 731 mice (male 372, female 359) were used for the standard data of our laboratory. Proper age for experiment were $30\pm3$days, body weight were $25\pm2gm (male)$, $23\pm1gm$. (female), minimal diurnal variation showed from 9A.M. to 12P.M.

• Atmosphere
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• v.29 no.4
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• pp.429-438
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• 2019

Organic carbon (OC) and elemental carbon (EC) in PM_2.5 were measured with Sunset Laboratory Model-5 Semi-Continuous OC/EC Field Analyzer by NIOSH/TOT method at Anmyeondo Global Atmosphere Watch (GAW) Regional Station (37°32'N, 127°19'E) in July and August, 2017. The mean values of OC and EC were 3.7 ㎍ m^-3 and 0.7 ㎍ m^-3, respectively. During the study period, the concentrations of reactive gases and aerosol compositions were evidently lower than those of other seasons. It is mostly due to meteorological setting of the northeast Asia, where the influence of continental outflow is at its minimum during this season under southwesterly wind. While the diurnal variation of OC and EC were not clear, the concentrations of O₃, CO, NOx, EC, and OC were evidently enhanced under easterly wind at night from 20:00 to 8:00. However, the high concentration of EC was observed concurrently with CO and NOx under northerly wind during 20:00~24:00. It indicates the influence of thermal power plant and industrial facilities, which was recognized as a major emission source during KORUS-AQ campaign. The diurnal variations of pollutants clearly showed the influence of land-sea breeze, in which OC showed good correlation between EC and O₃ in seabreeze. It is estimated to be the recirculation of pollutants in land-sea breeze cycle. This study suggests that in general, Anmyeondo station serves well as a background monitoring station. However, the variation in meteorological condition is so dynamic that it is primary factor to determine the concentrations of secondary species as well as primary pollutants at Anmyeondo station.