2006 Fiscal Year Final Research Report Summary
A study on the diurnal variation of low cloud microphysical properties
| Project/Area Number |
16340143
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | Research Institute for Humanity and Nature |
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Principal Investigator |
HAYASAKA Tadahiro Research Institute for Humanity and Nature, Research Department, Professor, 研究部, 教授 (40202262)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAMOTO Kazuaki Research Institute for Humanity and Nature, Research Department, Assistant Professor, 研究部, 助手 (10353450)
YATAGAI Akiyo Research Institute for Humanity and Nature, Research Department, Assistant Professor, 研究部, 助手 (60353447)
KUBA Naomi Japan Agency for Marine-Earth Science and Technology, Frontier Research Center for Global Change, Scientist, 地球環境フロンティア研究センター, 研究員 (50399581)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Clouds / Diurnal variation / Satellite remote sensing |
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| Research Abstract |
The cloud is one of the most important factors controlling the Earth's climate change. The low level cloud has a large reflectance and is affected by anthropogenic aerosols, that is, the indirect effect. However, the basic properties of low cloud is not sufficiently investigated. The intent of the present study is to investigate the mechanism of diurnal variation of low cloud microphysical properties. We used satellite data such as GOES and NOAA/AVHRR.
The stratiform low clouds off the coast of California were investigated by using GOES data. The reflection property of the cloud was used to estimate optical thickness and effective particle radius of cloud. It is found that cloud optical thickness decreased from morning to afternoon while effective particle radius increased during the same period and then decreased. The variation of optical thickness may ascribed to heating due to absorption of solar radiation. On the other hand, effective particle radius might change as a result of condensation, evaporation, coagulation, and gravitational fall out. It should be noted that the properties observed here is limited to cloud top because we used the reflected solar radiation in visible and near infrared spectral region.
In addition, NOAA/AVHRR data were used. The NOAA is polar orbital satellite, but diurnal variation can be observed because the orbit of NOAA satellite drifts and then equator overpass time slightly delay. It is also shown from the analysis of NOAA/AVHRR data that effective particle radius of low cloud decreased from noon to evening. This is consistent with the result obtained from the above GOES data analysis and ground based measurements with microwave radiometer and pyranometer carried out by other research group.
There are several different mechanisms of cloud forming, maintaining and disappearing, so that we need further studies involving satellite remote sensing, ground based observation, and meso-scale modeling with cloud microphysical processes.
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