• Title/Summary/Keyword: Cloud Optical Thickness

Search Result 39, Processing Time 0.025 seconds

Remote Sensing Cloud's Microphysical Properties by Satellite Data

  • Liu, Jian
    • Proceedings of the KSRS Conference
    • /
    • 2003.11a
    • /
    • pp.1258-1260
    • /
    • 2003
  • Cloud's properties can be showed on different spectral channel. The 0.65${\mu}$m reflectance is mainly function of cloud optical thickness and reflectance of 1.6${\mu}$m is sensitive to cloud phase and particle size distribution. So we can use multi-spectral information to analysis cloud's microphysical properties.

  • PDF

Study of aerosol-cloud interaction phenomena from satellite remote sensing and climate modeling

  • Nakajima, Teruyuki;Higurashi, Akiko;Kawamoto, Kazuaki;Okamoto, Hajime;Takemura, Toshihiko;Kuroda, Shunsuke
    • Proceedings of the KSRS Conference
    • /
    • 1999.11a
    • /
    • pp.100-102
    • /
    • 1999
  • We have analyzed AVHRR global data set for obtaining aerosol and cloud microphysical parameters, i. e., optical thickness and size index of particle polydispersions. From the results, it is found that the cloud optical thickness increases with increasing aerosol column number, which seems to be caused mainly by decreasing cloud particle radius, The cloud liquid water path was observed to be relatively constant without a significant dependence on the aerosol number. Further comparison of the satellite results with a general circulation model simulation.

  • PDF

Comparison of Aerosol Optical Thicknesses by MODIS and MI in Northeast Asia (동북아시아 지역에서 MODIS와 MI에 의한 에어로졸 광학두께 비교)

  • Kim, Eun-kyu;Lee, Kyu-Tae;Jung, Myeong-Jae
    • Korean Journal of Remote Sensing
    • /
    • v.33 no.5_1
    • /
    • pp.607-615
    • /
    • 2017
  • The aerosol optical thickness data retrieved by Moderate Resolution Imaging Spectrometer (MODIS) of Terra & Aqua and Meteorological Imager (MI) of Communication Ocean and Meteorological Satellite (COMS) are analyzed and compared with the measurement data of Aerosol Robotic Network (AERONET) in Northeast Asia. As the result, the aerosol optical thickness retrieved by MODIS and MI were well agreed at ocean region but quite different at cloud edge and barren surface. The reason was that MODIS aerosol optical thickness was retrieved using the visible and infrared channels but MI was retrieved with the visible channel only. Consequentially, the thin cloud be misinterpreted as aerosol by MI and the difference between MODIS and MI aerosol optical thicknesses could be occurred with Normal Distribution Vegetation Index (NDVI) and land surface property. Therefore, the accuracies of clear/cloud region and surface reflectivity are required in order to improve the aerosol optical thickness algorithm by MI.

VARIABILITY OF THE TRENDS OBSERVED FROM SEAWIFS-DERIVED SUB-MICRON AEROSOL FRACTION OVER EAST ASIAN SEAS BASED ON DIFFERENT CLOUD MASKING ALGORITHMS

  • Li, Li-Ping;Fukushima, Hajime;Takeno, Keisuke
    • Proceedings of the KSRS Conference
    • /
    • v.1
    • /
    • pp.316-319
    • /
    • 2006
  • Monthly-mean aerosol parameters derived from the 1998-2004 SeaWiFS observations over East Asian waters are analyzed. SeaWiFS GAC Level 1 data covering the Northeast Asian area are collected and processed by the standard atmospheric correction algorithm released by the SeaWiFS Project to produce daily aerosol optical thickness (AOT) and ${{\AA}}ngstr{\ddot{o}}m$ exponent imageries. Monthly mean AOT and ${{\AA}}ngstr{\ddot{o}}m$ exponent values are extracted from the daily composite images for six study areas chosen from the surrounding waters of Japan. A slight increasing trend of ${{\AA}}ngstr{\ddot{o}}m$ exponent is found and interpreted as about 4-5% increase in submicron fraction of aerosol optical thickness at 550nm. Two cloud screening methods, including the standard cloud masking method of SeaWiFS and the one based on the local variance method, are applied to the SeaWiFS data processing, in an attempt to inspect the influence to the observed statistical uptrend which probably induced by different cloud mask algorithms. The variability comes from the different cloud masking algorithms are discussed.

  • PDF

Analysis of Cloud Properties Related to Yeongdong Heavy Snow Using the MODIS Cloud Product (MODIS 구름 산출물을 이용한 영동대설 관련 구름 특성의 분석)

  • Ahn, Bo-Young;Cho, Kuh-Hee;Lee, Jeong-Soon;Lee, Kyu-Tae;Kwon, Tae-Yong
    • Korean Journal of Remote Sensing
    • /
    • v.23 no.2
    • /
    • pp.71-87
    • /
    • 2007
  • In this study, 14 heavy snow events in Yeongdong area which are local phenomena are analyzed using MODIS cloud products provided from NASA/GSFC. The clouds of Yeongdong area at observed at specific time by MODIS are classified into A, B, C Types, based on the characteristic of cloud properties: cloud top temperature, cloud optical thickness, Effective Particle Radius, and Cloud Particle Phase. The analysis of relations between cloud properties and precipitation amount for each cloud type show that there are statistically significant correlations between Cloud Optical Thickness and precipitation amount for both A and B type and also significant correlation is found between Cloud Top Temperature and precipitation amount for A type. However, for C type there is not any significant correlations between cloud properties and precipitation amount. A-type clouds are mainly lower stratus clouds with small-size droplet, which may be formed under the low level cold advection derived synoptically in the East sea. B-type clouds are developed cumuliform clouds, which are closely related to the low pressure center developing over the East sea. On the other hand, C-type clouds are likely multi-layer clouds, which make satellite observation difficult due to covering of high clouds over low level clouds directly related with Yeongdong heavy snow. It is, therefore, concluded that MODIS cloud products may be useful except the multi-layer clouds for understanding the mechanism of heavy snow and estimating the precipitation amount from satellite data in the case of Yeongdong heavy snow.

The Variation of UV Radiation by Cloud Scattering at King Sejong Station in West Antarctica (남극 세종기지에서의 구름 산란에 의한 자외선 변화)

  • Lee, Kyu-Tae;Lee, Bang-Yong;Won, Young-In;Kim, Youn-Joung;Lee, Won-Hak;Jee, Joon-Bum
    • Ocean and Polar Research
    • /
    • v.26 no.2
    • /
    • pp.133-143
    • /
    • 2004
  • For the purpose of understanding the cloud scattering effect of UV radiation at King Sejong station In West Antarctica, we analyzed the data measured by UV-Biometer at surface and compared its result with solar radiation model. The parameterization of UV radiation by cloud ice crystal was applied to solar radiation model and the sensitivity of this model for the variation of ice crystal was tested. The cloud optical thickness was calculated by using this solar radiation model. It was compared the result from calculation with CERES satellite data. In solar radiation model, the UV radiation was less scattered with increase of ice crystal size in cloud and this scattering effect was more important to UV-A radiation than Erythemal UV-B radiation. But scattering effects by altitude of cloud was not serious. The calculated cloud optical thicknesses in Erythemal UV-B and UV-A region were compared with CERES satellite data and the result by UV-A was more accurate than Erythemal UV-B region.

THE DEVELOPMENT OF IR-BASED VISIBLE CHANNEL CALIBRATION USING DEEP CONVECTIVE CLOUDS

  • Ham, Seung-Hee;Sohn, Byung-Ju
    • Proceedings of the KSRS Conference
    • /
    • 2008.10a
    • /
    • pp.430-432
    • /
    • 2008
  • Visible channel calibration method using deep convective clouds (DCCs) is developed. The method has advantages that visible radiance is not sensitive to cloud optical thickness (COT) for deep convective clouds because visible radiance no longer increases when COT exceeds 100. Therefore, once DCCs are chosen appropriately, and then cloud optical properties can be assumed without operational ancillary data for the specification of cloud conditions in radiative transfer model. In this study, it is investigated whether IR measurements can be used for the selection of DCC targets. To construct appropriate threshold value for the selection of DCCs, the statistics of cloud optical properties are collected with MODIS measurements. When MODIS brightness temperature (TB) at 11 ${\mu}$ m is restricted to be less than 190 K, it is shown that more than 85% of selected pixels show COT ${\geq}$ 100. Moreover, effective radius ($r_e$) distribution shows a sharp peak around 20 ${\mu}m$. Based on those MODIS observations, cloud optical properties are assumed as COT = 200 and $r_e$ = 20 ${\mu}m$ for the simulation of MODIS visible (0.646 ${\mu}m$) band radiances over DCC targets.

  • PDF

MODIS-estimated Microphysical Properties of Clouds Developed in the Presence of Biomass Burning Aerosols (MODIS 관측자료를 이용한 러시아 산불 영향 하에 발달한 구름의 미세 물리적 특성 연구)

  • Kim, Shin-Young;Sohn, Byung-Ju
    • Korean Journal of Remote Sensing
    • /
    • v.24 no.4
    • /
    • pp.289-298
    • /
    • 2008
  • An algorithm was developed to retrieve both cloud optical thickness and effective particle radius considered the aerosol effect on clouds. This study apply the algorithm of Nakajima and Nakajima (1995) that is used to retrieve cloud optical thickness and effective particle radius from visible, near infrared satellite spectral measurements. To retrieve cloud properties, Look-up table (LUT) was made under different atmospheric conditions by using a radiative transfer model. Especially the vertical distribution of aerosol is based on a tropospheric aerosol profile in radiative transfer model. In the case study, we selected the extensive forest fire occurred in Russia in May 2003. The aerosol released from this fire may be transported to Korea. Cloud properties obtained from these distinct atmospheric situations are analysed in terms of their possible changes due to the interactions of the clouds with the aerosol particle plumes. Cloud properties over the East sea at this time was retrieved using new algorithm. The algorithm is applied to measurements from the MODerate Resolution Imaging Spectrometer (MODIS) onboard the Terra spacecrafts. As a result, cloud effective particle radius was decreased and cloud optical thickness was increased during aerosol event. Specially, cloud effective particle radius is hardly greater than $20{\mu}m$ when aerosol particles were present over the East Sea. Clouds developing in the aerosol event tend to have more numerous but smaller droplets.

Development of Aerosol Retrieval Algorithm Over Ocean Using FY-1C/1D Data

  • Xiuqing, Hu;Naimeng, Lu;Hong, Qiu
    • Proceedings of the KSRS Conference
    • /
    • 2003.11a
    • /
    • pp.1255-1257
    • /
    • 2003
  • This study proposes a single-channel satellite remote sensing algorithm for retrieving aerosol optical thickness over global ocean using FY-1C/1D data. An efficient lookup table (LUT)method is adopted in this algorithm to generate apparent reflectance in channel 1 and channel 2 of FY-1C/1D over ocean. The algorithm scale the apparent reflectance in cloud-free conditions to aerosol optical thickness using a state-of-art radiative transfer model 6S with input of the relative spectral response of channel 1 and 2 of FY-1C/1D. Monthly mean composite maps of the aerosol optical thickness have been obtained from FY-1C/1D global area coverage data between 2001 and 2003. Aerosol optical thickness maps can show the major aerosol source which are located off the west coast of northern and southern Africa, Arabian Sea and India Ocean. These result is very similar to other satellite sensors such as AVHRR and MODIS in the location area of heavy aerosol optical thickness over global ocean. The algorithm have been used to FY-1D operational performance and it is the first operational aerosol remote sensing product in China.

  • PDF

Lidar Measurement of Optical Properties of Cirrus Clouds at Kwangju, Korea

  • Noh, Y.M.;Choi, S.C.;Kim, Y.J.
    • Proceedings of the KSRS Conference
    • /
    • 2003.11a
    • /
    • pp.959-961
    • /
    • 2003
  • Cirrus clouds observation was conducted using a lidar system in order to measure their height, thickness and optical depth at Kwangju (35$^{\circ}$10'N, 126$^{\circ}$53'), Korea in winter, December 2002, and spring March and April 2003. Cirrus clouds at high altitude can be distinguished from atmospheric aerosols location by high depolarization ratio and high altitude. Cirrus clouds were observed at 5${\sim}$12km altitudes with a high depolarization ratio from 0.2 to 0.5. Optical depth of cirrus clouds had varied from 0.28 to 1.81. Radiative effect of observed cirrus cloud on climate system was estimated to be negative net flux from ?0.24 to ?31.04 W/m$^{2}$.

  • PDF