Retrieving the Polar Mixed‐Phase Cloud Liquid Water Path by Combining CALIOP and IIR Measurements

Luo, Tao; Wang, Zhien; Li, Xuebin; Deng, Shumei; Huang, Yong; Wang, Yingjian

doi:10.1002/2017jd027291

Cited by 4 publications

(4 citation statements)

References 82 publications

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“…After removing these extreme data points, MODIS LWPs are still higher than AMSR‐E LWP measurements because other data points are also impacted by the 3D effect through at a lesser extent. This result is consistent with previous results showing a high bias in MODIS LWP in high latitudes when compared to in situ measurements (Noble & Hudson, ), surface‐based observations (AW13), and combined satellite lidar and infrared‐based observations (Luo et al, ). Figure e depicts the frequency distribution of solar zenith angle in these clouds, and it shows that significant fraction of observations are at solar zenith angles greater than 50°.…”

Section: Resultssupporting

confidence: 93%

“…MODIS measurements alone or lidar‐radar measurements alone do not provide enough information to constrain the properties in mixed‐phase clouds. Combining passive remote sensing measurements with CloudSat and CALIPSO can provide additional information to retrieve both liquid‐ and ice‐phase properties in stratiform mixed‐phase clouds (Luo et al, ). Based on the approach developed by AW13, stratiform mixed‐phase clouds can be modeled as a combination of two distinct adjoining layers: a liquid layer overlying an ice layer below, as shown in Figure a.…”

Section: Resultsmentioning

confidence: 99%

“…Miller et al () developed an approach to identify ice layer below the liquid‐topped layer in mixed‐phase clouds using multichannel SWIR satellite radiometer observations. Luo et al () describe a new algorithm to retrieve LWP in stratiform mixed‐phase clouds by combining Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar and infrared imaging radiometer measurements. They showed that the new algorithm provides improved cloud property retrievals over the Arctic region.…”

Section: Introductionmentioning

confidence: 99%

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Uncertainties in MODIS‐Based Cloud Liquid Water Path Retrievals at High Latitudes Due to Mixed‐Phase Clouds and Cloud Top Height Inhomogeneity

Khanal

Wang

2018

JGR Atmospheres

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Combined A-train remote sensing measurements from Moderate Resolution Imaging Spectroradiometer (MODIS), Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E), CloudSat, and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) are used to study MODIS liquid water path (LWP) uncertainties at high latitudes. The focus is on quantifying uncertainties due to mixed-phase clouds and solar zenith angle-dependent bias, both of which disproportionately affect the MODIS data set in the polar regions. Multisensor LWP retrievals in stratiform mixed-phase clouds show that treating mixed-phase clouds as liquid clouds result in LWP bias that is related to the ice water path (IWP) on average and reaches close to 15% at IWP of 150 g/m 2 and can reach 40% or higher when IWP is greater than 400 g/m 2 . Moreover, A-train measurements and radiative transfer modeling are used to further understand the well-known yet unresolved solar zenith angle-dependent high bias in MODIS LWP. It is shown that the cloud top height variation is one of the main factors that contribute to this bias due to three-dimensional radiative interactions with cloud top inhomogeneity. Excluding only 0.5% of data points that show significant three-dimensional errors reduces the bias by 25 g/m 2 at solar zenith angle of 80°and improves agreement with the AMSR-E LWP trends. Three-dimensional radiative transfer simulations confirm that cloud top inhomogeneity is primarily responsible for the solar zenith angle-dependent LWP bias as observed by the MODIS measurements. This study provides a framework to guide future improvements of MODIS LWP data set, which is a key data source to constrain climate models.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Uncertainties in MODIS‐Based Cloud Liquid Water Path Retrievals at High Latitudes Due to Mixed‐Phase Clouds and Cloud Top Height Inhomogeneity

Khanal

Wang

2018

JGR Atmospheres

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“…The new method developed in this study can provide a more complete and accurate global view of the ACA. Together with other satellite measurements such as MODIS [57] and CERES [58] and cloud property retrieval methods such as that described by Luo et al [59], the radiative effects of the ACA and its influences on the macro-and micro-physics of low clouds will be further studied in future work. These results not only help us better understand global aerosol transportation and aerosol-cloud interactions but also provide useful information for model evaluation and improvements.…”

Section: Discussionmentioning

confidence: 99%

New Global View of Above-Cloud Absorbing Aerosol Distribution Based on CALIPSO Measurements

et al. 2019

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Above-low-level-cloud aerosols (ACAs) have gradually gained more interest in recent years; however, the combined aerosol-cloud radiation effects are not well understood. The uncertainty about the radiative effects of aerosols above cloud mainly stems from the lack of comprehensive and accurate retrieval of aerosols and clouds for ACA scenes. In this study, an improved ACA identification and retrieval methodology was developed to provide a new global view of the ACA distribution by combining three-channel CALIOP (The Cloud-Aerosol Lidar with Orthogonal Polarization) observations. The new method can reliably identify and retrieve both thin and dense ACA layers, providing consistent results between the day-and night-time retrieval of ACAs. Then, new four-year (2007 to 2010) global ACA datasets were built, and new seasonal mean views of global ACA occurrence, optical depth, and geometrical thickness were presented and analyzed. Further discussion on the relative position of ACAs to low clouds showed that the mean distance between the ACA layer and the low cloud deck over the tropical Atlantic region is less than 0.2 km. This indicates that the ACAs over this region are more likely to be mixed with low-level clouds, thereby possibly influencing the cloud microphysics over this region, contrary to findings reported from previous studies. The results not only help us better understand global aerosol transportation and aerosol-cloud interactions but also provide useful information for model evaluation and improvements.A recent evaluation showed that most models cannot reproduce the observed large aerosol load episodes [13]. Therefore, improved observations are needed to better understand ACA-cloud interactions and to constrain the aerosol-cloud radiative processes in models.The ACA has gained increasing attention in recent years because of its important, but not well-understood, radiative and microphysical effects on clouds [14][15][16][17][18][19]. Different from clear-sky aerosols, which are usually associated with a negative (cooling) direct radiative effect [15,[19][20][21][22][23], the absorption effect of the ACA is significantly amplified due to the strong reflection light of low clouds, resulting in a less negative or even positive (warming) direct radiative effect. By warming the free troposphere and cooling the surface below, the ACA can increase the low cloud cover by enhancing atmospheric stability [24]. However, if the ACA mixes directly with the cloud layer, warming of the ACA could reduce the relative humidity, dissipating the cloud [24]. Therefore, the radiative and microphysical effects of ACAs on clouds depend on both their loadings and their positions relative to the clouds [25].Despite its importance, quantifying the effect of the ACA on the clouds from satellite observations is still challenging. For passive remote sensing, the ACA has usually been neglected, and only clear-sky aerosol concentrations can be derived from passive satellites [26,27]. This is because passive satellites employ the reflect...

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Improving middle and high latitude cloud liquid water path measurements from MODIS

Khanal

Wang

French

2020

Atmospheric Research

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Retrieving the Polar Mixed‐Phase Cloud Liquid Water Path by Combining CALIOP and IIR Measurements

Cited by 4 publications

References 82 publications

Uncertainties in MODIS‐Based Cloud Liquid Water Path Retrievals at High Latitudes Due to Mixed‐Phase Clouds and Cloud Top Height Inhomogeneity

Uncertainties in MODIS‐Based Cloud Liquid Water Path Retrievals at High Latitudes Due to Mixed‐Phase Clouds and Cloud Top Height Inhomogeneity

New Global View of Above-Cloud Absorbing Aerosol Distribution Based on CALIPSO Measurements

Improving middle and high latitude cloud liquid water path measurements from MODIS

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