• Title/Summary/Keyword: radiometer

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Retrieval of Depolarization ratio using Sunphotometer data and Comparison with LIDAR Depolarization ratio (선포토미터 데이터를 이용한 편광소멸도 산출과 라이다 편광소멸도와의 비교)

  • Kim, Kwanchul;Choi, Sungchul;Noh, Youngmin
    • Korean Journal of Remote Sensing
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    • v.32 no.2
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    • pp.97-104
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    • 2016
  • We present linear particle depolarization ratio at 440, 675, 870, and 1020 nm retrieved from measurements with an AERONET sun/sky radiometer at Osaka, Japan. The retrieved data were compared with lidar derived linear particle depolarization ratio at 532 nm at the same site. We find good agreement between linear particle depolarization ratios derived with Sun photometer and measured by lidar except for those at 440 nm. The coefficients of determination between lidar derived data and sun/sky radiometer derived data were 0.28, 0.81, 0.88, and 0.89 at 440, 675, 870, and 1020 nm, respectively. We find that the linear particle depolarization ratio derived with sun/sky radiometer varies by the mixing between Asian dust and pollution particles. As the mixing ratio of Asian dust and pollution particles is increased, the linear particle depolarization ratio values are lower than the values of pure Asian dust. It was confirmed by the value of single-scattering albedo and particle size distribution.

Advanced Microwave Scanning Radiometer E Soil Moisture Evaluation for Haenam Flux Monitoring Network Site (해남 플럭스 타워 지점에서의 Advanced Microwave Scanning Radiometer E 토양수분자료의 검증)

  • Hur, Yoo-Mi;Choi, Min-Ha
    • Korean Journal of Remote Sensing
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    • v.27 no.2
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    • pp.131-140
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    • 2011
  • In this study, temporal variations of the Advanced Microwave Scanning Radiometer E (AMSR-E) soil moisture products were evaluated using ground based measurements from the Haenam flux monitoring network site for two years (2004 and 2006). Even if there were major comparison issues including spatial resolutions, AMSR-E soil moisture production showed a great potential to replicate temporal variability patterns with ground based measurements. Additional intensive validation efforts should be conducted at a variety of field conditions including vegetation type for better utilization of remotely sensed soil moisture and understanding of the land surface-atmosphere interactions in the view of hydrometeorology.

Observation of the Cold-air Drainage and Thermal Belt Formation in a Small Mountainous Watershed by Using an Infrared Imaging Radiometer (적외선 영상 복사계를 이용한 산간집수역의 찬공기 배수와 온난대 형성 관측)

  • Yun, Jin-I.
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.13 no.2
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    • pp.79-86
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    • 2011
  • Cold-air drainage and pooling occur in most mountain valleys at night. Local climates with cold-air pooling could affect phenology and distribution of crop plants. A high resolution infrared imaging radiometer was used to visualize the cold-air drainage and thermal belt formation over a small mountainous watershed (ca. $10{\times}5{\times}1$ km for the maximum length${\times}$width${\times}$depth). Thermal images on $640{\times}480$ pixels were scanned across the Akyang valley (south of Mt. Jiri National Park) by the radiometer installed at a local peak ('Hyongjebong', 1,117 m a.s.l.) at dawn of 17 May 2011, when the synoptic condition was favorable for the surface cooling and cold-air drainage. Major findings are: (1) Cold-air drainage and accumulation was clearly identified by the lowest brightness temperature mainly at the valley bottom. (2) So-called 'thermal belt' with higher brightness temperature was found partway up the valley sidewalls and showed up to $5^{\circ}C$ departure from the valley bottom temperature. (3) Digital thermography showed feasibility for validation of the high definition geospatial temperature models currently in use for the plot-specific agrometeorological service.

VERTICAL OZONE DENSITY PROFILING BY UV RADIOMETER ONBOARD KSR-III

  • Hwang Seung-Hyun;Kim Jhoon;Lee Soo-Jin;Kim Kwang-Soo;Ji Ki-Man;Shin Myung-Ho;Chung Eui-Seung
    • Bulletin of the Korean Space Science Society
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    • 2004.10b
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    • pp.372-375
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    • 2004
  • The UV radiometer payload was launched successfully from the west coastal area of Korea Peninsula aboard KSR-III on 28, Nov 2002. KSR-III was the Korean third generation sounding rocket and was developed as intermediate step to larger space launch vehicle with liquid propulsion engine system. UV radiometer onboard KSR-III consists of UV and visible band optical phototubes to measure the direct solar attenuation during rocket ascending phase. For UV detection, 4 channel of sensors were installed in electronics payload section and each channel has 255, 290, 310nm center wavelengths, respectively. 450nm channel was used as reference for correction of the rocket attitude during the flight. Transmission characteristics of all channels were calibrated precisely prior to the flight test at the Optical Lab. in KARI (Korea Aerospace Research Institute). During a total of 231s flight time, the onboard data telemetered to the ground station in real time. The ozone column density was calculated by this telemetry raw data. From the calculated column density, the vertical ozone profile over Korea Peninsula was obtained with sensor calibration data. Our results had reasonable agreements compared with various observations such as ground Umkhr measurement at Yonsei site, ozonesonde at Pohang site, and satellite measurements of HALOE and POAM. The sensitivity analysis of retrieval algorithm for parameters was performed and it was provided that significant error sources of the retrieval algorithm.

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Harmonic-Suppressed Hairpin Bandpass Filter for the Microwave Radiometer (마이크로파 라디오미터를 위한 하모닉 억제 특성을 가진 헤어핀 필터)

  • Yun, Tae-Soon
    • The Journal of the Korea institute of electronic communication sciences
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    • v.9 no.10
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    • pp.1169-1174
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    • 2014
  • In this paper, for improving the performance of selecting and the sensitivity of the L-Band microwave radiometer for remote sensing of soil-moisture, the harmonic-suppressed hairpin bandpass filter is described. As the harmonic frequencies of the SIR can be controlled by the ratio of the impedance and electrical length, SIRs are used in the hairpin BPF for suppressing harmonics. Manufactured harmonic-suppressed hairpin BPF has the SIRs of three types and its harmonic is suppressed under 35 [dB] until 5 times of the center frequency of 1390 [MHz].

Aerosol Optical Properties Retrieval and Separation of Asian Dust using AERONET Sun/Sky Radiometer Measurement at the Asian Dust Source Region (황사 발원지에서 선포토미터를 활용한 에어로졸의 광학적 특성 산출과 미세먼지속 황사구분)

  • Shin, Dongho;Noh, Youngmin
    • Korean Journal of Remote Sensing
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    • v.32 no.3
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    • pp.245-251
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    • 2016
  • We present linear particle depolarization ratio at 440, 675, 870, and 1020 nm retrieved from measurements with an AERONET sun/sky radiometer at the source region of Asian dust, Dunhuang. The linear particle depolarization ratios are retrieved at the two receptor sites (Gosan and Osaka). The highest linear particle depolarization ratio of 0.34 at 1020 nm is retrieved from nearly pure Asian dust. The linear particle depolarization ratio decreased as the volume concentration of fine-mode particle increased. We can confirm that the ratio of Asian dust is changed by the value of the linear particle depolarization ratio retrieved by AERONET data.

Comparison of the Characteristics of Precipitable Water Vapor Measured by Global Positioning System and Microwave Radiometer

  • Sohn, Dong-Hyo;Park, Kwan-Dong;Won, Ji-Hye;Cho, Jung-Ho;Roh, Kyoung-Min
    • Journal of Astronomy and Space Sciences
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    • v.29 no.1
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    • pp.1-10
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    • 2012
  • In this study, global positioning system (GPS)-derived precipitable water vapor (PWV) and microwave radiometer (MWR)-measured integrated water vapor (IWV) were compared and their characteristics were analyzed. Comparing those two quantities for two years from August 2009, we found that GPS PWV estimates were larger than MWR IWV. The average difference over the entire test period was 1.1 mm and the standard deviation was 1.2 mm. When the discrepancies between GPS PWV and MWR IWV were analyzed depending on season, the average difference was 0.7 mm and 1.9 mm in the winter and summer months, respectively. Thus, the average difference was about 2.5 times larger in summer than that in winter. However, MWR IWV measurements in the winter months were over-estimated than those in the summer months as the water vapor content got larger. The results of the diurnal analysis showed that MWR IWV was underestimated in the daytime, showing a difference of 0.8 mm. In the early morning hours, MWR IWV has a tendency to be over-estimated, with a difference of 1.3 mm with respect to GPS PWV.

Pacific Equatorial Sea Surface Temperature Variation During the 2015 El Niño Period Observed by Advanced Very-High-Resolution Radiometer of NOAA Satellites

  • Lee, Seongsuk;Yi, Yu
    • Journal of Astronomy and Space Sciences
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    • v.35 no.2
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    • pp.105-109
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    • 2018
  • El $Ni{\tilde{n}}o$ is the largest fluctuation in the climate system, and it can lead to effects influencing humans all over the world. An El $Ni{\tilde{n}}o$ occurs when sea surface temperatures in the central and eastern tropical Pacific Ocean become substantially higher than average. We investigated the change in sea surface temperature in the Pacific Ocean during the El $Ni{\tilde{n}}o$ period of 2015 and 2016 using the advanced very-high-resolution radiometer (AVHRR) of NOAA Satellites. We calculated anomalies of the Pacific equatorial sea surface temperature for the normal period of 1981-2010 to identify the variation of the 2015 El $Ni{\tilde{n}}o$ and warm water area. Generally, the warm water in the western tropical Pacific Ocean shifts eastward along the equator toward the coast of South America during an El $Ni{\tilde{n}}o$ period. However, we identified an additional warm water region in the $Ni{\tilde{n}}o$ 1+2 and Peru coastal area. This indicates that there are other factors that increase the sea surface temperature. In the future, we will study the heat coming from the bottom of the sea to understand the origin of the heat transport of the Pacific Ocean.

High Spatial Resolution Imaging of the Contiguous Objects Using Sub-Y-Type Interferometric Synthetic Aperture Radiometer

  • Lee Ho-Jin;Park Hyuk;Kim Sung-Hyun;Choi Jun-Ho;Seo Seung-Won;Kim Yong-Hoon;Kang Gum-Sil
    • Proceedings of the KSRS Conference
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    • 2004.10a
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    • pp.53-56
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    • 2004
  • Recently the interferometric synthetic aperture radiometer with sub-Y-type antenna array was suggested to improve the spatial resolution than that of conventional Y-type with the same number of antenna elements. The sub-Y-type performance has been reported under a point source target. In this paper, the performance of sub-Y-type is evaluated under contiguous objects. The angular resolution of sub-Y-type with 52 antennas was compared with that of Y-type with the 40 antennas. The images of sub-Y -type and Y-type array were simulated under the contiguous objects. The sub-Y-type showed higher resolution than Y-type in the simulation and experiments. The sub-Y-type has high spatial resolution than Y-type in case of contiguous source as well as single point source.

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EXPERIMENTAL DEMONSTRATION OF ADVANTAGE OF MOTION INDUCED SYNTHETIC APERTURE RADIOMETER

  • Park, Hyuk;Kim, Sung-Hyun;Lee, Ho-Jin;Moon, Nam-Won;Yu, Hwan-Wook;NamGoong, Up;Sim, Won-Seon;Kim, Yong-Hoon
    • Proceedings of the KSRS Conference
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    • 2008.10a
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    • pp.22-25
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    • 2008
  • Aperture synthesis with platform motion has been presented as a useful tool to achieve the high spatial resolution imaging. Using a motion induced synthetic aperture radiometer (MISAR), a passive microwave image can be achieved with a small number of antennas. Moreover, the MISAR is capable of imaging better than the case without motion, using the same configuration of antenna array. With a platform motion, visibility can be sampled more efficiently, and as a result the imaging performance of the MISAR shows higher quality than the case without platform motion. In this paper, the advantage of MISAR is demonstrated experimentally. Using a laboratory model of inteferometric radiometer, the point source images are obtained under the condition with platform motion and without platform motion. In the experimental results, the point source response of the MISAR shows better quality of sidelobe level and beam efficiency than the case without platform motion.

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