Review of ``Investigating processes that control the vertical distribution of aerosol in five subtropical marine stratocumulus regions -- A sensitivity study using the climate model NorESM1-M`` by Lena Frey et al.

Abstract. The vertical distribution of aerosols plays an important role in determining the effective radiative forcing from aerosol–radiation and aerosol–cloud interactions. Here, a number of processes controlling the vertical distribution of aerosol in five subtropical marine stratocumulus regions in the climate model NorESM1-M are investigated, with a focus on the total aerosol extinction. A comparison with satellite lidar data (CALIOP, Cloud-Aerosol Lidar with Orthogonal Polarization) shows that the model underestimates aerosol extinction throughout the troposphere, especially elevated aerosol layers in the two regions where they are seen in observations. It is found that the shape of the vertical aerosol distribution is largely determined by the aerosol emissions and removal processes in the model, primarily through the injection height, emitted particle size, and wet scavenging. In addition, the representation of vertical transport related to shallow convection and entrainment are found to be important, whereas alterations in aerosol optical properties and cloud microphysics parameterizations have smaller effects on the vertical aerosol extinction distribution. However, none of the alterations made are sufficient for reproducing the observed vertical distribution of aerosol extinction, neither in magnitude nor in shape. Interpolating the vertical levels of CALIOP to the corresponding model levels, leads to a better agreement in the boundary layer and highlights the importance of the vertical resolution.

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Processes controlling the vertical aerosol distribution in marine stratocumulus regions – a sensitivity study using the climate model NorESM1-M

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-577-2021 ◽

2021 ◽

Vol 21 (1) ◽

pp. 577-595

Author(s):

Lena Frey ◽

Frida A.-M. Bender ◽

Gunilla Svensson

Keyword(s):

Vertical Distribution ◽

Radiative Forcing ◽

Climate Model ◽

Cloud Microphysics ◽

Aerosol Extinction ◽

Shallow Convection ◽

Marine Stratocumulus ◽

Aerosol Emission ◽

Aerosol Distribution ◽

The Vertical Distribution

Abstract. The vertical distribution of aerosols plays an important role in determining the effective radiative forcing from aerosol–radiation and aerosol–cloud interactions. Here, a number of processes controlling the vertical distribution of aerosol in five subtropical marine stratocumulus regions in the climate model NorESM1-M are investigated, with a focus on the total aerosol extinction. A comparison with satellite lidar data (CALIOP, Cloud–Aerosol Lidar with Orthogonal Polarization) shows that the model underestimates aerosol extinction throughout the troposphere, especially elevated aerosol layers in the two regions where they are seen in observations. It is found that the shape of the vertical aerosol distribution is largely determined by the aerosol emission and removal processes in the model, primarily through the injection height, emitted particle size, and wet scavenging. In addition, the representation of vertical transport related to shallow convection and entrainment is found to be important, whereas alterations in aerosol optical properties and cloud microphysics parameterizations have smaller effects on the vertical aerosol extinction distribution. However, none of the alterations made are sufficient for reproducing the observed vertical distribution of aerosol extinction, neither in magnitude nor in shape. Interpolating the vertical levels of CALIOP to the corresponding model levels leads to better agreement in the boundary layer and highlights the importance of the vertical resolution.

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In situ constraints on the vertical distribution of global aerosol

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-11765-2019 ◽

2019 ◽

Vol 19 (18) ◽

pp. 11765-11790 ◽

Cited By ~ 5

Author(s):

Duncan Watson-Parris ◽

Nick Schutgens ◽

Carly Reddington ◽

Kirsty J. Pringle ◽

Dantong Liu ◽

...

Keyword(s):

Vertical Distribution ◽

Climate Model ◽

Cloud Condensation Nuclei ◽

Upper Troposphere ◽

Aerosol Forcing ◽

Wide Range ◽

Vertical Distributions ◽

The Vertical Distribution ◽

Unique Dataset

Abstract. Despite ongoing efforts, the vertical distribution of aerosols globally is poorly understood. This in turn leads to large uncertainties in the contributions of the direct and indirect aerosol forcing on climate. Using the Global Aerosol Synthesis and Science Project (GASSP) database – the largest synthesised collection of in situ aircraft measurements currently available, with more than 1000 flights from 37 campaigns from around the world – we investigate the vertical structure of submicron aerosols across a wide range of regions and environments. The application of this unique dataset to assess the vertical distributions of number size distribution and cloud condensation nuclei (CCN) in the global aerosol–climate model ECHAM-HAM reveals that the model underestimates accumulation-mode particles in the upper troposphere, especially in remote regions. The processes underlying this discrepancy are explored using different aerosol microphysical schemes and a process sensitivity analysis. These show that the biases are predominantly related to aerosol ageing and removal rather than emissions.

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Sensitivity of the Ocean State to the Vertical Distribution of Internal-Tide-Driven Mixing

Journal of Physical Oceanography ◽

10.1175/jpo-d-12-055.1 ◽

2013 ◽

Vol 43 (3) ◽

pp. 602-615 ◽

Cited By ~ 85

Author(s):

Angelique Melet ◽

Robert Hallberg ◽

Sonya Legg ◽

Kurt Polzin

Keyword(s):

Vertical Distribution ◽

Vertical Profile ◽

Energy Input ◽

Climate Model ◽

Internal Tide ◽

Meridional Overturning Circulation ◽

Internal Tides ◽

Diapycnal Mixing ◽

Recent Climate ◽

The Vertical Distribution

Abstract The ocean interior stratification and meridional overturning circulation are largely sustained by diapycnal mixing. The breaking of internal tides is a major source of diapycnal mixing. Many recent climate models parameterize internal-tide breaking using the scheme of St. Laurent et al. While this parameterization dynamically accounts for internal-tide generation, the vertical distribution of the resultant mixing is ad hoc, prescribing energy dissipation to decay exponentially above the ocean bottom with a fixed-length scale. Recently, Polzin formulated a dynamically based parameterization, in which the vertical profile of dissipation decays algebraically with a varying decay scale, accounting for variable stratification using Wentzel–Kramers–Brillouin (WKB) stretching. This study compares two simulations using the St. Laurent and Polzin formulations in the Climate Model, version 2G (CM2G), ocean–ice–atmosphere coupled model, with the same formulation for internal-tide energy input. Focusing mainly on the Pacific Ocean, where the deep low-frequency variability is relatively small, the authors show that the ocean state shows modest but robust and significant sensitivity to the vertical profile of internal-tide-driven mixing. Therefore, not only the energy input to the internal tides matters, but also where in the vertical it is dissipated.

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Assessment of upper tropospheric and stratospheric water vapour and ozone in reanalyses as part of S-RIP

10.5194/acp-2017-377 ◽

2017 ◽

Cited By ~ 3

Author(s):

Sean M. Davis ◽

Michaela I. Hegglin ◽

Masatomo Fujiwara ◽

Rossana Dragani ◽

Yayoi Harada ◽

...

Keyword(s):

Vertical Distribution ◽

Water Vapour ◽

Climate Model ◽

Reanalysis Data ◽

Future Research ◽

Total Column Ozone ◽

Tropical Tropopause Layer ◽

Tropical Tropopause ◽

Weak Constraints ◽

The Vertical Distribution

Abstract. Reanalysis data sets are widely used to understand atmospheric processes and past variability, and are often used to stand in as “observations” for comparisons with climate model output. Because of the central role of water vapour (WV) and ozone (O3) in climate change, it is important to understand how accurately and consistently these species are represented in existing global reanalyses. In this paper, we present the results of WV and O3 intercomparisons that have been performed as part of the SPARC (Stratosphere-troposphere Processes and their Role in Climate) Reanalysis Intercomparison Project (S-RIP). The comparisons cover a range of timescales and evaluate both inter-reanalysis and observation-reanalysis differences. We also provide a systematic documentation of the treatment of WV and O3 in current reanalyses to aid future research and guide the interpretation of differences amongst reanalysis fields. The assimilation of total column ozone (TCO) observations in newer reanalyses results in realistic representations of TCO in reanalyses except when data coverage is lacking, such as during polar night. The vertical distribution of ozone is also relatively well represented in the stratosphere in reanalyses, particularly given the relatively weak constraints on ozone vertical structure provided by most assimilated observations and the simplistic representations of ozone photochemical processes in most of the reanalysis forecast models. However, significant biases in the vertical distribution of ozone are found in the upper troposphere and lower stratosphere in all reanalyses. In contrast to O3, reanalysis estimates of stratospheric WV are not directly constrained by assimilated data. Observations of atmospheric humidity are typically used only in the troposphere, below a specified vertical level at or near the tropopause. The fidelity of reanalysis stratospheric WV products is therefore mainly dependent on the reanalyses' representation of the physical drivers that influence stratospheric WV, such as temperatures in the tropical tropopause layer, methane oxidation, and the stratospheric overturning circulation. The lack of assimilated observations and known deficiencies in the representation of stratospheric transport in reanalyses result in much poorer agreement amongst observational and reanalysis estimates of stratospheric WV. Hence, stratospheric WV products from the current generation of reanalyses should generally not be used in scientific studies.

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Assessment of upper tropospheric and stratospheric water vapor and ozone in reanalyses as part of S-RIP

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-12743-2017 ◽

2017 ◽

Vol 17 (20) ◽

pp. 12743-12778 ◽

Cited By ~ 20

Author(s):

Sean M. Davis ◽

Michaela I. Hegglin ◽

Masatomo Fujiwara ◽

Rossana Dragani ◽

Yayoi Harada ◽

...

Keyword(s):

Water Vapor ◽

Vertical Distribution ◽

Climate Model ◽

Reanalysis Data ◽

Future Research ◽

Total Column Ozone ◽

Stratospheric Water Vapor ◽

Tropical Tropopause ◽

Weak Constraints ◽

The Vertical Distribution

Abstract. Reanalysis data sets are widely used to understand atmospheric processes and past variability, and are often used to stand in as "observations" for comparisons with climate model output. Because of the central role of water vapor (WV) and ozone (O3) in climate change, it is important to understand how accurately and consistently these species are represented in existing global reanalyses. In this paper, we present the results of WV and O3 intercomparisons that have been performed as part of the SPARC (Stratosphere–troposphere Processes and their Role in Climate) Reanalysis Intercomparison Project (S-RIP). The comparisons cover a range of timescales and evaluate both inter-reanalysis and observation-reanalysis differences. We also provide a systematic documentation of the treatment of WV and O3 in current reanalyses to aid future research and guide the interpretation of differences amongst reanalysis fields.The assimilation of total column ozone (TCO) observations in newer reanalyses results in realistic representations of TCO in reanalyses except when data coverage is lacking, such as during polar night. The vertical distribution of ozone is also relatively well represented in the stratosphere in reanalyses, particularly given the relatively weak constraints on ozone vertical structure provided by most assimilated observations and the simplistic representations of ozone photochemical processes in most of the reanalysis forecast models. However, significant biases in the vertical distribution of ozone are found in the upper troposphere and lower stratosphere in all reanalyses.In contrast to O3, reanalysis estimates of stratospheric WV are not directly constrained by assimilated data. Observations of atmospheric humidity are typically used only in the troposphere, below a specified vertical level at or near the tropopause. The fidelity of reanalysis stratospheric WV products is therefore mainly dependent on the reanalyses' representation of the physical drivers that influence stratospheric WV, such as temperatures in the tropical tropopause layer, methane oxidation, and the stratospheric overturning circulation. The lack of assimilated observations and known deficiencies in the representation of stratospheric transport in reanalyses result in much poorer agreement amongst observational and reanalysis estimates of stratospheric WV. Hence, stratospheric WV products from the current generation of reanalyses should generally not be used in scientific studies.

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In-situ constraints on the vertical distribution of global aerosol

10.5194/acp-2018-1337 ◽

2019 ◽

Author(s):

Duncan Watson-Parris ◽

Nick Schutgens ◽

Carly Reddington ◽

Kirsty J. Pringle ◽

Dantong Liu ◽

...

Keyword(s):

Vertical Distribution ◽

Climate Model ◽

Cloud Condensation Nuclei ◽

Upper Troposphere ◽

Aerosol Forcing ◽

Wide Range ◽

Vertical Distributions ◽

The Vertical Distribution ◽

Unique Dataset

Abstract. Despite ongoing efforts, the vertical distribution of aerosols globally is poorly understood. This in turn leads to large uncertainties in the contributions of the direct and indirect aerosol forcing on climate. Using the Global Aerosol Synthesis and Science Project (GASSP) database – the largest synthesised collection of in-situ aircraft measurements currently available, with more than 1000 flights from 37 campaigns from around the world – we investigate the vertical structure of sub-micron aerosols across a wide range of regions and environments. The application of this unique dataset to assess the vertical distributions of number size distribution and Cloud Condensation Nuclei (CCN) in the global aerosol-climate model ECHAM-HAM reveals that the model underestimates accumulation mode particles in the upper troposphere, especially in remote regions. The processes underlying this discrepancy are explored using different aerosol microphysical schemes and a process sensitivity analysis. These show that the biases are predominantly related to aerosol ageing and removal rather than emissions.

Download Full-text