Quantifying uncertainties in radar forward models through a comparison between CloudSat and SPartICus reflectivity factors

Mascio, Jeana; Mace, Gerald G.

doi:10.1002/2016jd025183

Cited by 8 publications

(4 citation statements)

References 40 publications

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“…The statistical characteristics of W and RHi from the observations could also be reproduced by the REF experiment (not shown). Because the ICs could be shattered during measurement, it is possible for Ni to be overestimated [13,44,58]. Under the same qi, NiRi is decreased with decreasing Ni.…”

Section: Discussionmentioning

confidence: 99%

A Study on the Wide Range of Relative Humidity in Cirrus Clouds Using Large-Ensemble Parcel Model Simulations

Zhao¹,

Shi²

2023

Preprint

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This study investigates the possible mechanisms related to the wide range of relative humidity in cirrus clouds (RHi). Under the closed adiabatic assumption, the impacts of vertical motion and ice crystal deposition/sublimation on RHi are investigated through in situ observations and parcel model simulations. Vertical motion is an active external force that changes the RHi, and ice crystal deposition/sublimation plays a role in mitigating the change in RHi. They are the two most important mechanisms involved in controlling the RHi fluctuation during cirrus evolution and could well explain the wide range of RHi in wave-related cirrus clouds. Furthermore, a comparison of cloud statistical characteristics from both observations and simulations shows that a very low value (e.g., 0.001) for the water vapor ice deposition coefficient is highly unlikely.

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Section: Discussionmentioning

confidence: 99%

A Study on the Wide Range of Relative Humidity in Cirrus Clouds Using Large-Ensemble Parcel Model Simulations

Zhao¹,

Shi²

2023

Preprint

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“…However, it is becoming increasingly apparent from work presented here and elsewhere (SH10; H10; H13; H16) that choosing specific power law parameters tends to drive uncertainty in both modeling and retrieval algorithm applications (Hammonds et al, ; Maahn et al, ; Mace & Benson, ; Wood et al, ; Wood et al, ). Xu and Mace () and Mascio and Mace () show that ice crystal properties are best represented by a continuum whose statistics covary with conditions. Here in situ data collected during TC4 are analyzed in two different optimal estimation approaches (MZ algorithm and XIWC algorithm) to retrieve optimal m‐D relationships based on minimizing differences between radar reflectivity (MZ algorithm) or IWC (XIWC algorithm).…”

Section: Discussionmentioning

confidence: 99%

“…Also, it is becoming increasingly apparent that choosing specific power law parameters tend to drive uncertainty in both modeling and retrieval algorithm applications (Hammonds, Mace, & Matrosov, 2014;Heymsfield, Matrosov, & Wood, 2016;Mace & Benson, 2017). Instead of discrete shapes assumed to exist under specific conditions, ice crystal properties seem to be best represented by a continuum whose statistics covary with conditions (Mascio & Mace, 2017;Xu & Mace, 2017;hereafter M17 and X17, respectively).…”

Section: Introductionmentioning

confidence: 99%

The Mass‐Dimensional Properties of Cirrus Clouds During TC4

Mascio

Mace

2017

JGR Atmospheres

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Remote sensing retrievals and ice microphysical parameterizations in global climate models typically use assumptions about the distribution of ice mass as a function of particle size using mass‐dimensional (m‐D) relationships. This study investigates the ice crystal m‐D properties of tropical anvil cirrus during the Tropical Composition, Cloud and Climate Coupling Experiment (TC4) to better document the distribution of ice mass with size in this particular class of tropical ice clouds. Two optimal estimation algorithms (XIWC and MZ) are used to estimate the m‐D relationship for each particle size distribution (PSD) collected in situ. The XIWC algorithm minimizes the difference between measured ice water content (IWC) and PSD calculated IWC, while the MZ algorithm minimizes the difference between measured radar reflectivity factors and those calculated from the in situ PSDs. Results from these algorithms are compared to previous studies to establish consistency of the methodologies. The XIWC results show that both parameters in the m‐D relationship increase with temperature. Changes in m‐D with temperature have substantial implications for remote sensing retrievals. With the prefactor varying by a factor of 5 and the exponent varying by some 16% over a typical range of ice cloud temperatures, forward modeling errors in radar reflectivity could be typically in excess of 5 dB, further suggesting that retrievals of IWC and precipitation rates from radar measurements in ice clouds be in error by factors easily exceeding 3.

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“…Posselt et al (2015) examined uncertainties and information content for radar observations of mixed-and icephase regions of a convective storm, but targeted radar systems with more advanced capabilities. Mascio and Mace (2017) used CloudSat and aircraft observations to assess how uncertainties in the ice particle mass-dimension relationship contribute to radar reflectivity forward model uncertainties, but used known, observed particle size distributions and did not examine the influence of the mass-dimension uncertainties on snowfall retrieval performance.…”

Section: Introductionmentioning

confidence: 99%

What millimeter-wavelength radar reflectivity reveals about snowfall: an information-centric analysis

Wood

L’Ecuyer

2021

Atmos. Meas. Tech.

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Abstract. The ability of single-frequency, millimeter-wavelength radar reflectivity observations to provide useful constraints for retrieval of snow particle size distribution (PSD) parameters, snowfall rates, and snowfall accumulations is examined. An optimal estimation snowfall retrieval that allows analyses of retrieval uncertainties and information content is applied to observations of near-surface W-band reflectivities from multiple snowfall events during the 2006–2007 winter season in southern Ontario. Retrieved instantaneous snowfall rates generally have uncertainties greater than 100 %, but single-event and seasonal snow accumulations from the retrieval results match well with collocated measurements of accumulations. Absolute fractional differences are mainly below 30 % for individual events that have more substantial accumulations and, for the season, 12.6 %. Uncertainties in retrieved snowfall rates are driven mainly by uncertainties in the retrieved PSD parameters, followed by uncertainties in particle model parameters and, to a lesser extent, the uncertainties in the fall-speed model. Uncertainties attributable to assuming an exponential distribution are negligible. The results indicate that improvements to PSD and particle model a priori constraints provide the most impactful path forward for reducing uncertainties in retrieved snowfall rates. Information content analyses reveal that PSD slope is well-constrained by the retrieval. Given the sensitivity of PSD slope to microphysical transformations, the results show that such retrievals, when applied to radar reflectivity profiles, could provide information about microphysical transformations in the snowing column. The PSD intercept is less well-constrained by the retrieval. While applied to near-surface radar observations in this study, the retrieval is applicable as well to radar observations aloft, such as those provided by profiling ground-based, airborne, and satellite-borne radars under lighter snowfall conditions when attenuation and multiple scattering can be neglected.

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Quantifying uncertainties in radar forward models through a comparison between CloudSat and SPartICus reflectivity factors

Cited by 8 publications

References 40 publications

A Study on the Wide Range of Relative Humidity in Cirrus Clouds Using Large-Ensemble Parcel Model Simulations

A Study on the Wide Range of Relative Humidity in Cirrus Clouds Using Large-Ensemble Parcel Model Simulations

The Mass‐Dimensional Properties of Cirrus Clouds During TC4

What millimeter-wavelength radar reflectivity reveals about snowfall: an information-centric analysis

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