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- Title
Retrieval of cloud properties from sky radiometer observed spectral zenith radiances.
- Authors
Khatri, Pradeep; Hironobu Iwabuchi; Tadahiro Hayasaka; Hitoshi Irie; Tamio Takamura; Akihiro Yamazaki; Damiani, Alessandro; Husi Letu; Qin Kai
- Abstract
An optimal-estimation based algorithm to retrieve cloud optical thickness (COD) and cloud-particle effective radius (CER) from spectral zenith radiances observed by a narrow field of view (FOV) ground-based sky radiometer is developed. To further address the filter-degradation problem while analyzing data of long-term observation, an on-site calibration procedure is proposed, which is found to have a very good accuracy with respect to a standard procedure, i.e., a procedure of deriving calibration constants using a master instrument. An error evaluation study conducted by assuming errors in observation-based transmittances and ancillary data of water vapor concentration and surface albedo suggests that the errors in input data can influence retrieved CER more effectively than COD. Except for some narrow domains that fall within COD < 15, the retrieval errors are very small for both COD and CER. The retrieved cloud properties are found to reproduce the broadband radiances observed by a narrow FOV radiometer more precisely than broadband irradiances observed by a wide FOV pyranometer, justifying the quality of retrieved product (at least COD) and, at the same time, indicating the important influence of instrument FOV in cloud remote sensing. Further, CODs (CERs) between sky radiometer and satellite observations show fairly good (poor) agreement.
- Subjects
ALBEDO; RADIOMETERS; RADIANCE; SKY; WATER vapor; REMOTE sensing
- Publication
Atmospheric Measurement Techniques Discussions, 2019, p1
- ISSN
1867-8610
- Publication type
Article
- DOI
10.5194/amt-2019-273