Impact of cloud horizontal inhomogeneity and directional sampling on the retrieval of cloud droplet size by the POLDER instrument

	Impact of cloud horizontal inhomogeneity and directional sampling on the retrieval of cloud droplet size by the POLDER instrument
	Shang, H.1; Chen, L.1; Breon, F. M.1; Letu, H.1; Li, S.1; Wang, Z.1; Su, L.1
刊名	ATMOSPHERIC MEASUREMENT TECHNIQUES
	2015
卷号	8 期号:11 页码:5715-5725
通讯作者	Chen, L (reprint author), Chinese Acad Sci, Inst Remote Sensing & Digital Earth, State Key Lab Remote Sensing Sci, Beijing, Peoples R China.
英文摘要	The principles of cloud droplet size retrieval via Polarization and Directionality of the Earth's Reflectance (POLDER) requires that clouds be horizontally homogeneous. The retrieval is performed by combining all measurements from an area of 150 km x 150 km to compensate for POLDER's insufficient directional sampling. Using POLDER-like data simulated with the RT3 model, we investigate the impact of cloud horizontal inhomogeneity and directional sampling on the retrieval and analyze which spatial resolution is potentially accessible from the measurements. Case studies show that the sub-grid-scale variability in droplet effective radius (CDR) can significantly reduce valid retrievals and introduce small biases to the CDR (similar to 1.5 mu m) and effective variance (EV) estimates. Nevertheless, the sub-grid-scale variations in EV and cloud optical thickness (COT) only influence the EV retrievals and not the CDR estimate. In the directional sampling cases studied, the retrieval using limited observations is accurate and is largely free of random noise. Several improvements have been made to the original POLDER droplet size retrieval. For example, measurements in the primary rainbow region (137-145 degrees) are used to ensure retrievals of large droplet (> 15 mu m) and to reduce the uncertainties caused by cloud heterogeneity. We apply the improved method using the POLDER global L1B data from June 2008, and the new CDR results are compared with the operational CDRs. The comparison shows that the operational CDRs tend to be underestimated for large droplets because the cloudbow oscillations in the scattering angle region of 145-165 degrees are weak for cloud fields with CDR > 15 mu m. Finally, a sub-grid-scale retrieval case demonstrates that a higher resolution, e.g., 42 km x 42 km, can be used when inverting cloud droplet size distribution parameters from POLDER measurements.
研究领域[WOS]	Meteorology & Atmospheric Sciences
收录类别	SCI
语种	英语
WOS记录号	WOS:000365978100023
内容类型	期刊论文
源URL	[http://ir.ceode.ac.cn/handle/183411/38304]
专题	遥感与数字地球研究所_SCI/EI期刊论文_期刊论文
作者单位	1.[Shang, H. 2.Chen, L. 3.Letu, H. 4.Li, S. 5.Su, L.] Chinese Acad Sci, Inst Remote Sensing & Digital Earth, State Key Lab Remote Sensing Sci, Beijing, Peoples R China 6.[Shang, H.] Univ Chinese Acad Sci, Coll Resources & Environm, Beijing, Peoples R China 7.[Breon, F. M.] UVSQ, CEA, CNRS, UMR,Lab Sci Climat & Environm, Gif Sur Yvette, France 8.[Letu, H.] Tokai Univ, Res & Informat Ctr, Tokyo 151, Japan 9.[Wang, Z.] Minist Environm Protect, Satellite Environm Ctr, Beijing, Peoples R China
推荐引用方式 GB/T 7714	Shang, H.,Chen, L.,Breon, F. M.,et al. Impact of cloud horizontal inhomogeneity and directional sampling on the retrieval of cloud droplet size by the POLDER instrument[J]. ATMOSPHERIC MEASUREMENT TECHNIQUES,2015,8(11):5715-5725.
APA	Shang, H..,Chen, L..,Breon, F. M..,Letu, H..,Li, S..,...&Su, L..(2015).Impact of cloud horizontal inhomogeneity and directional sampling on the retrieval of cloud droplet size by the POLDER instrument.ATMOSPHERIC MEASUREMENT TECHNIQUES,8(11),5715-5725.
MLA	Shang, H.,et al."Impact of cloud horizontal inhomogeneity and directional sampling on the retrieval of cloud droplet size by the POLDER instrument".ATMOSPHERIC MEASUREMENT TECHNIQUES 8.11(2015):5715-5725.