Independent Pixel and Monte Carlo Estimates of Stratocumulus Albedo

Cahalan, Robert F.; Ridgway, William L.; Wiscombe, W. J.; Gollmer, Steven M.; Harshvardhan, _

doi:10.1175/1520-0469(1994)051<3776:ipamce>2.0.co;2

Cited by 224 publications

(187 citation statements)

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“…Cahalan et al (1994a,b); Scheirer and Macke (2003). One approach to approximate horizontally inhomogeneous clouds with one-dimensional solvers is the independent pixel approximation (IPA) (Cahalan et al, 1994b). The IPA ignores horizontal photon transport but includes horizontal inhomogeneities in the cloud optical properties.…”

Section: Cloudsmentioning

confidence: 99%

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

2005

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Abstract. The libRadtran software package is a suite of tools for radiative transfer calculations in the Earth's atmosphere. Its main tool is the uvspec program. It may be used to compute radiances, irradiances and actinic fluxes in the solar and terrestrial part of the spectrum. The design of uvspec allows simple problems to be easily solved using defaults and included data, hence making it suitable for educational purposes. At the same time the flexibility in how and what input may be specified makes it a powerful and versatile tool for research tasks. The uvspec tool and additional tools included with libRadtran are described and realistic examples of their use are given. The libRadtran software package is available from http://www.libradtran.org.

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Section: Cloudsmentioning

confidence: 99%

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

2005

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“…3.5). For eCF > 10 %, a cloud correction based on the independent pixel approximation (IPA) (Cahalan et al, 1994) is applied for the three TG retrievals. It should also be noted that observations of the outermost pixels (i.e.…”

Section: Max-doas Instrument and Data Analysismentioning

confidence: 99%

Validation of OMI, GOME-2A and GOME-2B tropospheric NO<sub>2</sub>, SO<sub>2</sub> and HCHO products using MAX-DOAS observations from 2011 to 2014 in Wuxi, China: investigation of the effects of priori profiles and aerosols on the satellite products

et al. 2017

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Abstract. Tropospheric vertical column densities (VCDs) of NO 2 , SO 2 and HCHO derived from the Ozone Monitoring Instrument (OMI) on AURA and the Global Ozone Monitoring Experiment 2 aboard METOP-A (GOME-2A) and METOP-B (GOME-2B) are widely used to characterize the global distributions, trends and dominating sources of these trace gases. They are also useful for the comparison with chemical transport models (CTMs). We use tropospheric VCDs and vertical profiles of NO 2 , SO 2 and HCHO derived from MAX-DOAS measurements from 2011 to 2014 in Wuxi, China, to validate the corresponding products (daily and bi-monthly-averaged data) derived from OMI and GOME-2A/B by different scientific teams. Prior to the comparison, the spatial and temporal coincidence criteria for MAX-DOAS and satellite data are determined by a sensitivity study using different spatial and temporal averaging conditions. Cloud effects on both MAX-DOAS and satellite observations are also investigated. Our results indicate that the discrepancies between satellite and MAX-DOAS results increase with increasing effective cloud fraction and are dominated by the effects of clouds on the satellite products. In comparison with MAX-DOAS, we found a systematic underestimation of all SO 2 (40 to 57 %) and HCHO products (about 20 %), and an overestimation of the GOME-2A/B NO 2 products (about 30 %), but good consistency with the DOMINO version 2 NO 2 product. To better understand the reasons for these differences, we evaluated the a priori profile shapes used in the OMI retrievals (derived from CTM) by comparison with those derived from the MAX-DOAS observations. Significant differences are found for the SO 2 and HCHO profile shapes derived from the IMAGES model, whereas on average good agreement is found for the NO 2 profile shapes derived from the TM4 model. We also applied the MAX-DOAS profile shapes to the satellite rePublished by Copernicus Publications on behalf of the European Geosciences Union. 5008 Y. Wang et al.: Validation of OMI, GOME-2A and GOME-2B tropospheric NO 2 , SO 2 and HCHO products trievals and found that these modified satellite VCDs agree better with the MAX-DOAS VCDs than the VCDs from the original data sets by up to 10, 47 and 35 % for NO 2 , SO 2 and HCHO, respectively. Furthermore, we investigated the effect of aerosols on the satellite retrievals. For OMI observations of NO 2 , a systematic underestimation is found for large AOD, which is mainly attributed to effect of the aerosols on the cloud retrieval and the subsequent application of a cloud correction scheme (implicit aerosol correction). In contrast, the effect of aerosols on the clear-sky air mass factor (explicit aerosol correction) has a smaller effect. For SO 2 and HCHO observations selected in the same way, no clear aerosol effect is found, probably because for the considered data sets no cloud correction is applied (and also because of the larger scatter). From our findings we conclude that for satellite observations with cloud top pressure (CTP) > 900 hPa and effective ...

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“…Since the horizontal photon movement induces horizontal radiative interactions, both full 3-D and ICA modeling are available by turning on or off the horizontal movement option that is available in GRIMALDI. Then ICA bias is defined as the difference between ICA and full 3-D modeling results (Cahalan et al, 1994b), i.e. :…”

Section: -D Effects Associated With Horizontal Radiative Interactionsmentioning

confidence: 99%

Assessment of the calibration performance of satellite visible channels using cloud targets: application to Meteosat-8/9 and MTSAT-1R

Ham

Sohn

2010

Atmos. Chem. Phys.

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and MTSAT-1R visible channel reflectances. In the simulation, cloud three-dimensional (3-D) radiative effect associated with subgrid variations is taken into account using the lognormal-independent column approximation (LN-ICA) to minimize the simulation bias caused by the plane-parallel homogeneous assumption. Third, an independent method uses the typical optical properties of deep convective clouds (DCCs) to simulate reflectances of selected DCC targets.Although all three methods are not in perfect agreement, the results suggest that calibration coefficients of Meteosat-8/9 0.640-µm channels are underestimated by 6-7%. On the other hand, the calibration accuracy of MTSAT-1R visible channel appears to be variable with the target reflectance itself because of an underestimate of calibration coefficient (up to 20%) and a non-zero space offset. The results further suggest that the solar channel calibration scheme combining the Correspondence to: B. J. Sohn (sohn@snu.ac.kr) three methods in this paper can be used as a tool to monitor the calibration performance of visible sensors that are particularly not equipped with an onboard calibration system.

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Independent Pixel and Monte Carlo Estimates of Stratocumulus Albedo

Cited by 224 publications

References 0 publications

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

Validation of OMI, GOME-2A and GOME-2B tropospheric NO<sub>2</sub>, SO<sub>2</sub> and HCHO products using MAX-DOAS observations from 2011 to 2014 in Wuxi, China: investigation of the effects of priori profiles and aerosols on the satellite products

Assessment of the calibration performance of satellite visible channels using cloud targets: application to Meteosat-8/9 and MTSAT-1R

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Independent Pixel and Monte Carlo Estimates of Stratocumulus Albedo

Cited by 224 publications

References 0 publications

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

Validation of OMI, GOME-2A and GOME-2B tropospheric NO&lt;sub&gt;2&lt;/sub&gt;, SO&lt;sub&gt;2&lt;/sub&gt; and HCHO products using MAX-DOAS observations from 2011 to 2014 in Wuxi, China: investigation of the effects of priori profiles and aerosols on the satellite products

Assessment of the calibration performance of satellite visible channels using cloud targets: application to Meteosat-8/9 and MTSAT-1R

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Validation of OMI, GOME-2A and GOME-2B tropospheric NO<sub>2</sub>, SO<sub>2</sub> and HCHO products using MAX-DOAS observations from 2011 to 2014 in Wuxi, China: investigation of the effects of priori profiles and aerosols on the satellite products