Joint retrievals of cloud and drizzle in marine boundary layer clouds using ground-based radar, lidar and zenith radiances

Fielding, Mark R.; Chiu, J. Christine; Hogan, Robin J.; Feingold, Graham; Eloranta, E. W.; O’Connor, Ewan; Cadeddu, Maria

doi:10.5194/amt-8-2663-2015

Cited by 38 publications

(44 citation statements)

References 79 publications

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“…The averages of the LWC cld and LWC dzl maximum values are 1.9 × 10 −1 and 1.2 × 10 −3 g m −3 , respectively. The temporal variations in the cloud and drizzle LWP are positively correlated in time, as was also found by Fielding et al (2015).…”

Section: Application To Ground-based Observationssupporting

confidence: 61%

“…Observations of these clouds to characterize the microphysical and radiative processes are therefore needed for climate studies. One important aspect of such observations is the presence of drizzle, which is found to be a common occurrence in stratocumulus clouds (Fox and Illingworth, 1997). Drizzle alters the cloud droplet spectra and thus the microphysical structure and radiative properties of the clouds vanZanten et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

“…Since the observed reflectivity contains contributions from both cloud and drizzle droplets, its interpretation is not straightforward. Fielding et al (2015) set a precedent by jointly retrieving cloud and drizzle properties using ground-based radar, lidar, and Sun-photometer observations. Their retrieval departs from the assumption that drizzle is present only when the maximum observed reflectivity in a given column exceeds a single threshold value.…”

Section: Introductionmentioning

confidence: 99%

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Simultaneous and synergistic profiling of cloud and drizzle properties using ground-based observations

2017

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Abstract. Despite the importance of radar reflectivity (Z) measurements in the retrieval of liquid water cloud properties, it remains nontrivial to interpret Z due to the possible presence of drizzle droplets within the clouds. So far, there has been no published work that utilizes Z to identify the presence of drizzle above the cloud base in an optimized and a physically consistent manner. In this work, we develop a retrieval technique that exploits the synergy of different remote sensing systems to carry out this task and to subsequently profile the microphysical properties of the cloud and drizzle in a unified framework. This is accomplished by using ground-based measurements of Z, lidar attenuated backscatter below as well as above the cloud base, and microwave brightness temperatures. Fast physical forward models coupled to cloud and drizzle structure parameterization are used in an optimal-estimation-type framework in order to retrieve the best estimate for the cloud and drizzle property profiles. The cloud retrieval is first evaluated using synthetic signals generated from large-eddy simulation (LES) output to verify the forward models used in the retrieval procedure and the vertical parameterization of the liquid water content (LWC). From this exercise it is found that, on average, the cloud properties can be retrieved within 5 % of the mean truth. The full cloud-drizzle retrieval method is then applied to a selected ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) campaign dataset collected in Cabauw, the Netherlands. An assessment of the retrieval products is performed using three independent methods from the literature; each was specifically developed to retrieve only the cloud properties, the drizzle properties below the cloud base, or the drizzle fraction within the cloud. One-to-one comparisons, taking into account the uncertainties or limitations of each retrieval, show that our results are consistent with what is derived using the three independent methods.

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Section: Application To Ground-based Observationssupporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simultaneous and synergistic profiling of cloud and drizzle properties using ground-based observations

2017

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“…After identifying the virga and rain drizzle, we adopt the method of O'Connor et al (2005) to retrieve the drizzle microphysical properties using both radar reflectivity and laser-ceilometer-attenuated backscatter coefficient. The cloud base heights used in this study were determined using a threshold of 10 −4 Sr −1 m −1 in attenuated backscatter coefficient (similar to O'Connor et al, 2004 andFielding et al, 2015). The liquid water path (LWP) is derived from the microwave radiometer with an uncertainty of 20 g m −2 for LWP < 200 g m −2 , and 10 % for LWP > 200 g m −2 (Liljegren et al, 2001;.…”

Section: Methodsmentioning

confidence: 99%

Marine boundary layer drizzle properties and their impact on cloud property retrieval

Dong

2015

Atmos. Meas. Tech.

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Abstract. In this study, we retrieve and document drizzle properties, and investigate the impact of drizzle on cloud property retrieval in Dong et al. The annual mean differences in cloud-droplet effective radius with and without drizzle are 0.75 and 2.35 %, respectively, for the virga and rain samples. Therefore, we conclude that the impact of drizzle below the cloud base on cloud property retrieval is insignificant for a solar-transmission-based method, but significant for any retrievals using radar reflectivity.

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“…Painemal et al () draw on the surface‐based three‐channel MWR from the MAGIC campaign as a third independent source of information and find that the MAGIC observations agree reasonably well with the CERES‐MODIS SSF retrieval, but both provide lower LWP estimates than those from satellite MWR in trade cumulus. While the three‐channel MWR retrieval is arguably the most accurate for nonprecipitating conditions with an uncertainty of about 5–8 g/m 2 (Fielding et al, ), a wet radome prevents accurate retrievals and will produce erroneously high LWP values. Thus, scenes where precipitation reaches the surface (which are likely to contain clouds with larger water path) must be removed, which will lead to a systematic underestimate of the all‐sky average.…”

Section: Comparison With Observationsmentioning

confidence: 99%

Understanding Global Model Systematic Shortwave Radiation Errors in Subtropical Marine Boundary Layer Cloud Regimes

Ahlgrimm

Forbes

Hogan

et al. 2018

J Adv Model Earth Syst

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Global numerical weather prediction and climate models are subject to long-standing systematic shortwave radiation errors due to deficiencies in the representation of boundary layer clouds over the ocean. In the subtropics, clouds are typically too reflective in the cumulus regime and not reflective enough in the stratocumulus regime. Potential sources of error include cloud cover, liquid water path, effective radius, and subgrid heterogeneity, but diagnosing the absolute contributions of each to the radiation bias is hampered by uncertainties and sometimes contradictory information from different observational products. This paper draws on a set of ship-based observations of boundary layer clouds obtained during the ARM MAGIC campaign along a northeast Pacific Ocean transect, crossing both stratocumulus and shallow cumulus cloud regimes. The surface-based observations of cloud properties are compared with various satellite products, taking account of the diurnal cycle, to provide an improved quantitative assessment of the deficiencies in the European Centre for Medium-Range Weather Forecasts global numerical weather prediction model. A series of off-line radiation calculations are then performed to assess the impact on the shortwave radiation bias of correcting each of the model's deficiencies in cloud characteristics along the transect. A reduction in the bias is achieved by improving the agreement between modeled and observed in-cloud liquid water path frequency distributions. In the cumulus regime, this is accomplished primarily by reducing the all-sky water path, while for the stratocumulus regime, an underestimate of cloud cover and liquid water and an overestimate in effective radius and subgrid heterogeneity all contribute to a lack of reflected shortwave radiation.

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Joint retrievals of cloud and drizzle in marine boundary layer clouds using ground-based radar, lidar and zenith radiances

Cited by 38 publications

References 79 publications

Simultaneous and synergistic profiling of cloud and drizzle properties using ground-based observations

Simultaneous and synergistic profiling of cloud and drizzle properties using ground-based observations

Marine boundary layer drizzle properties and their impact on cloud property retrieval

Understanding Global Model Systematic Shortwave Radiation Errors in Subtropical Marine Boundary Layer Cloud Regimes

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