Retrieval of Vertical Profiles of Cirrus Cloud Microphysical Parameters from Doppler Radar and Infrared Radiometer Measurements

Matrosov, Sergey Y.; Orr, Brad W.; Kropfli, R. A.; Snider, J. B.

doi:10.1175/1520-0450(1994)033<0617:rovpoc>2.0.co;2

Cited by 67 publications

(55 citation statements)

References 10 publications

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“…An important reason for choosing this case study was that these cloud properties were already analysed (by G. G. Mace, Utah) and available for this study (Mace, 1998). The retrieval is based on algorithms using radar reflectivity and downwelling infrared radiances to evaluate the cirrus cloud microphysical properties (Matrosov et al, 1992;Matrosov et al, 1994). The layer-averaged properties of optically thin cirrus is applied, which is calculated by using the observational platforms at the ARM sites.…”

Section: Remote Sensingmentioning

confidence: 99%

GEWEX Cloud System Study (GCSS) cirrus cloud working group: development of an observation-based case study for model evaluation

et al. 2012

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Abstract. The GCSS working group on cirrus focuses on an inter-comparison of model simulations ranging from very detailed microphysical and dynamical models through to general circulation models (GCMs). The past GCSS cirrus cloud inter-comparison highlighted the wide range in modelling results that was a surprise to the modelling community. That inter-comparison was idealised and, therefore, a key issue was that it did not benefit from observations to help distinguish between model performances.In this work, we aim to address this key issue by developing an observationally based case study to be used for the GCSS cirrus modelling inter-comparison study. We focused on developing a case that had sufficient observations with which to evaluate models, to help identify which models in the inter-comparison are performing well and highlight areas for model development. Furthermore, it will provide a base case for future model comparisons or testing of new or updated models. This paper outlines the modelling case development and the inter-comparison results will be presented in a follow-on paper.The case was based on the 9 March 2000 Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) during an intensive observation period (IOP). The case was developed utilising various observations including ARM SGP remote sensing including the MilliMeter Cloud Radar (MMCR), radiometers, radiosondes, aircraft observations, satellite observations, objective analysis and complemented with results from the Rapid Update Cycle (RUC) model as well as bespoke gravity wave simulations used to provide the best estimate for large scale forcing. The retrievals of ice water content, ice number concentration and fall velocity provide several constraints to evaluate model performances. Initial testing of the case has been reported using the UK Met Office Large Eddy Simulation Model (LEM) which suggests the case is appropriate for the model inter-comparison study. To our knowledge, this case offers the most detailed case study for cirrus comparison available and we anticipate this will offer significant benefits over past comparisons which have mostly been loosely based on observations.

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Section: Remote Sensingmentioning

confidence: 99%

GEWEX Cloud System Study (GCSS) cirrus cloud working group: development of an observation-based case study for model evaluation

et al. 2012

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“…Matrosov et al, 1994;Evans and Stephens, 1995) or a bimodal distribution (e.g. Mitchell et al, 1996;Platt, 1997;McFarquhar and Heymsfield, 1997), neither of which takes into account the effect of aerosol on r e (i.e.…”

Section: Introductionmentioning

confidence: 99%

Influence of convection and aerosol pollution on ice cloud particle effective radius

Jiang

Zhai

et al. 2011

Atmos. Chem. Phys.

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Abstract. Satellite observations show that ice cloud effective radius (r e ) increases with ice water content (IWC) but decreases with aerosol optical thickness (AOT). Using leastsquares fitting to the observed data, we obtain an analytical formula to describe the variations of r e with IWC and AOT for several regions with distinct characteristics of r e -IWC-AOT relationships. As IWC directly relates to convective strength and AOT represents aerosol loading, our empirical formula provides a means to quantify the relative roles of dynamics and aerosols in controlling r e in different geographical regions, and to establish a framework for parameterization of aerosol effects on r e in climate models.

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“…Time-averaging Doppler radar velocities is intended to remove the time-varying contribution of the vertical winds, allowing retrieval of mass-squared-weighted fallspeeds (e.g. Matrosov et al 1994;Matrosov and Heymsfield 2000). However, the simulated radar data did not allow the accuracy of the time-averaging method to be evaluated for this cloud since, as noted in section 5(b), time-smoothing the modelled vertical winds showed that these did not average to zero because of waves in the LEM.…”

Section: (D) Time-smoothing Doppler Velocities To Retrieve Fallspeedsmentioning

confidence: 99%

“…The radiative balance of global models has also been shown to be very sensitive to the specification of fallspeeds (Heymsfield and Iaquinta 2000). Time-averaging of Doppler radar data is one method that has been used to retrieve fallspeeds (Matrosov et al 1994;Matrosov and Heymsfield 2000), and in this paper this technique is applied to both real and simulated data and is used to evaluate the fallspeeds in the model. Section 2 briefly describes the quantities retrieved from the 94 GHz radar and the 905 nm lidar at Chilbolton, UK.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of a large-eddy model simulation of a mixed-phase altocumulus cloud using microwave radiometer, lidar and Doppler radar data

Marsham

Dobbie

Hogan

2006

Q. J. R. Meteorol. Soc.

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SUMMARYUsing the Met Office large-eddy model (LEM) we simulate a mixed-phase altocumulus cloud that was observed from Chilbolton in southern England by a 94 GHz Doppler radar, a 905 nm lidar, a dual-wavelength microwave radiometer and also by four radiosondes. It is important to test and evaluate such simulations with observations, since there are significant differences between results from different cloud-resolving models for ice clouds. Simulating the Doppler radar and lidar data within the LEM allows us to compare observed and modelled quantities directly, and allows us to explore the relationships between observed and unobserved variables. For general-circulation models, which currently tend to give poor representations of mixed-phase clouds, the case shows the importance of using: (i) separate prognostic ice and liquid water, (ii) a vertical resolution that captures the thin layers of liquid water, and (iii) an accurate representation the subgrid vertical velocities that allow liquid water to form.It is shown that large-scale ascents and descents are significant for this case, and so the horizontally averaged LEM profiles are relaxed towards observed profiles to account for these. The LEM simulation then gives a reasonable cloud, with an ice-water path approximately two thirds of that observed, with liquid water at the cloud top, as observed. However, the liquid-water cells that form in the updraughts at cloud top in the LEM have liquid-water paths (LWPs) up to half those observed, and there are too few cells, giving a mean LWP five to ten times smaller than observed. In reality, ice nucleation and fallout may deplete ice-nuclei concentrations at the cloud top, allowing more liquid water to form there, but this process is not represented in the model. Decreasing the heterogeneous nucleation rate in the LEM increased the LWP, which supports this hypothesis.The LEM captures the increase in the standard deviation in Doppler velocities (and so vertical winds) with height, but values are 1.5 to 4 times smaller than observed (although values are larger in an unforced model run, this only increases the modelled LWP by a factor of approximately two). The LEM data show that, for values larger than approximately 12 cm s −1 , the standard deviation in Doppler velocities provides an almost unbiased estimate of the standard deviation in vertical winds, but provides an overestimate for smaller values. Time-smoothing the observed Doppler velocities and modelled mass-squared-weighted fallspeeds shows that observed fallspeeds are approximately two-thirds of the modelled values. Decreasing the modelled fallspeeds to those observed increases the modelled IWC, giving an IWP 1.6 times that observed.

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Retrieval of Vertical Profiles of Cirrus Cloud Microphysical Parameters from Doppler Radar and Infrared Radiometer Measurements

Cited by 67 publications

References 10 publications

GEWEX Cloud System Study (GCSS) cirrus cloud working group: development of an observation-based case study for model evaluation

GEWEX Cloud System Study (GCSS) cirrus cloud working group: development of an observation-based case study for model evaluation

Influence of convection and aerosol pollution on ice cloud particle effective radius

Evaluation of a large-eddy model simulation of a mixed-phase altocumulus cloud using microwave radiometer, lidar and Doppler radar data

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