Global S&T Development Trend Analysis Platform of Resources and Environment
DOI | 10.5194/acp-18-12105-2018 |
Scale dependence of cirrus heterogeneity effects. Part II: MODIS NIR and SWIR channels | |
Fauchez, Thomas1,2; Platnick, Steven2; Varnai, Tamas2,3,4; Meyer, Kerry2; Cornet, Celine5; Szczap, Frederic6 | |
2018-08-22 | |
发表期刊 | ATMOSPHERIC CHEMISTRY AND PHYSICS |
ISSN | 1680-7316 |
EISSN | 1680-7324 |
出版年 | 2018 |
卷号 | 18期号:16页码:12105-12121 |
文章类型 | Article |
语种 | 英语 |
国家 | USA; France |
英文摘要 | In a context of global climate change, the understanding of the radiative role of clouds is crucial. On average, ice clouds such as cirrus have a significant positive radiative effect, but under some conditions the effect may be negative. However, many uncertainties remain regarding the role of ice clouds on Earth's radiative budget and in a changing climate. Global satellite observations are particularly well suited to monitoring clouds, retrieving their characteristics and inferring their radiative impact. To retrieve ice cloud properties (optical thickness and ice crystal effective size), current operational algorithms assume that each pixel of the observed scene is plane-parallel and homogeneous, and that there is no radiative connection between neighboring pixels. Yet these retrieval assumptions are far from accurate, as real radiative transfer is 3-D. This leads to the plane-parallel and homogeneous bias (PPHB) plus the independent pixel approximation bias (IPAB), which impacts both the estimation of top-of-the-atmosphere (TOA) radiation and the retrievals. An important factor that determines the impact of these assumptions is the sensor spatial resolution. High-spatial-resolution pixels can better represent cloud variability (low PPHB), but the radiative path through the cloud can involve many pixels (high IPAB). In contrast, low-spatial-resolution pixels poorly represent the cloud variability (high PPHB), but the radiation is better contained within the pixel field of view (low IPAB). In addition, the solar and viewing geometry (as well as cloud optical properties) can modulate the magnitude of the PPHB and IPAB. In this, Part II of our study, we simulate TOA 0.86 and 2.13 mu m solar reflectances over a cirrus uncinus scene produced by the 3DCLOUD model. Then, 3-D radiative transfer simulations are performed with the 3DMCPOL code at spatial resolutions ranging from 50m to 10 km, for 12 viewing geometries and nine solar geometries. It is found that, for simulated nadir observations taken at resolution higher than 2.5 km, horizontal radiation transport (HRT) dominates biases between 3-D and 1-D reflectance calculations, but these biases are mitigated by the side illumination and shadowing effects for off-zenith solar geometries. At resolutions coarser than 2.5 km, PPHB dominates. For off-nadir observations at resolutions higher than 2.5 km, the effect that we call THEAB (tilted and homogeneous extinction approximation bias) due to the oblique line of sight passing through many cloud columns contributes to a large increase of the reflectances, but 3-D radiative effects such as shadowing and side illumination for oblique Sun are also important. At resolutions coarser than 2.5 km, the PPHB is again the dominant effect. The magnitude and resolution dependence of PPHB and IPAB is very different for visible, near-infrared and shortwave infrared channels compared with the thermal infrared channels discussed in Part I of this study. The contrast of 3-D radiative effects between solar and thermal infrared channels may be a significant issue for retrieval techniques that simultaneously use radiative measurements across a wide range of solar reflectance and infrared wavelengths. |
领域 | 地球科学 |
收录类别 | SCI-E |
WOS记录号 | WOS:000442397700007 |
WOS关键词 | INDEPENDENT PIXEL APPROXIMATION ; CLOUD OPTICAL DEPTH ; RADIATIVE-TRANSFER ; ALBEDO ; STRATOCUMULUS ; BIASES ; CLIMATE ; MODEL ; TOP ; UNCERTAINTIES |
WOS类目 | Environmental Sciences ; Meteorology & Atmospheric Sciences |
WOS研究方向 | Environmental Sciences & Ecology ; Meteorology & Atmospheric Sciences |
引用统计 | |
文献类型 | 期刊论文 |
条目标识符 | http://119.78.100.173/C666/handle/2XK7JSWQ/19504 |
专题 | 地球科学 |
作者单位 | 1.Univ Space Res Assoc, Columbia, MD 21046 USA; 2.NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA; 3.Univ Maryland, Baltimore Cty Joint Ctr Earth Syst Technol, Baltimore, MD 21201 USA; 4.Dept Phys, Baltimore, MD USA; 5.Univ Lille 1, Lab Opt Atmospher, UMR 8518, Villeneuve Dascq, France; 6.Univ Blaise Pascal, Lab Meteorol Phys, UMR 6016, Clermont Ferrand, France |
推荐引用方式 GB/T 7714 | Fauchez, Thomas,Platnick, Steven,Varnai, Tamas,et al. Scale dependence of cirrus heterogeneity effects. Part II: MODIS NIR and SWIR channels[J]. ATMOSPHERIC CHEMISTRY AND PHYSICS,2018,18(16):12105-12121. |
APA | Fauchez, Thomas,Platnick, Steven,Varnai, Tamas,Meyer, Kerry,Cornet, Celine,&Szczap, Frederic.(2018).Scale dependence of cirrus heterogeneity effects. Part II: MODIS NIR and SWIR channels.ATMOSPHERIC CHEMISTRY AND PHYSICS,18(16),12105-12121. |
MLA | Fauchez, Thomas,et al."Scale dependence of cirrus heterogeneity effects. Part II: MODIS NIR and SWIR channels".ATMOSPHERIC CHEMISTRY AND PHYSICS 18.16(2018):12105-12121. |
条目包含的文件 | 条目无相关文件。 |
除非特别说明,本系统中所有内容都受版权保护,并保留所有权利。
修改评论