scholarly journals Atmospheric ionization and cloud radiative forcing

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Henrik Svensmark ◽  
Jacob Svensmark ◽  
Martin Bødker Enghoff ◽  
Nir J. Shaviv
Keyword(s):  
Radiative Forcing ◽  
Cloud Condensation Nuclei ◽  
Short Wave ◽  
Satellite Observations ◽  
Cloud Formation ◽  
Wave Radiation ◽  
Substantial Impact ◽  
Radiative Balance ◽  
Cloud Radiative Forcing ◽  
Atmospheric Ionization

AbstractAtmospheric ionization produced by cosmic rays has been suspected to influence aerosols and clouds, but its actual importance has been questioned. If changes in atmospheric ionization have a substantial impact on clouds, one would expect to observe significant responses in Earth’s energy budget. Here it is shown that the average of the five strongest week-long decreases in atmospheric ionization coincides with changes in the average net radiative balance of 1.7 W/m$$^2$$ 2 (median value: 1.2 W/m$$^2$$ 2 ) using CERES satellite observations. Simultaneous satellite observations of clouds show that these variations are mainly caused by changes in the short-wave radiation of low liquid clouds along with small changes in the long-wave radiation, and are almost exclusively located over the pristine areas of the oceans. These observed radiation and cloud changes are consistent with a link in which atmospheric ionization modulates aerosol's formation and growth, which survive to cloud condensation nuclei and ultimately affect cloud formation and thereby temporarily the radiative balance of Earth.

scholarly journals Impact of mineral dust on cloud formation in a Saharan outflow region

2011 ◽  
Vol 11 (12) ◽  
pp. 32363-32390 ◽  
Author(s):  
L. Smoydzin ◽  
A. Teller ◽  
H. Tost ◽  
M. Fnais ◽  
J. Lelieveld
Keyword(s):  
Radiative Forcing ◽  
Mineral Dust ◽  
Eastern Mediterranean ◽  
Cloud Condensation Nuclei ◽  
Coupled Model ◽  
Cloud Formation ◽  
Dust Particles ◽  
Ice Nuclei ◽  
Outflow Region ◽  
The Impact

Abstract. We present a numerical modelling study investigating the impact of mineral dust on cloud formation over the Eastern Mediterranean for two case studies: (i) 25 September 2008 and (ii) 28/29 January 2003. On both days dust plumes crossed the Mediterranean and interacted with clouds forming along frontal systems. For our investigation we used the fully online coupled model WRF-chem. The results show that increased aerosol concentrations due to the presence of mineral dust can enhance the formation of ice crystals. This leads to slight shifts of the spatial and temporal precipitation patterns compared to scenarios where dust was not considered to act as ice nuclei. However, the total amount of precipitation did not change significantly. The only exception occurred when dust entered into an area of orographic ascent, causing glaciation of the clouds, leading to a local enhancement of rainfall. The impact of dust particles acting as giant cloud condensation nuclei on precipitation formation was found to be small. Based on our simulations the contribution of dust to the CCN population is potentially significant only for warm phase clouds. Nevertheless, the dust-induced differences in the microphysical structure of the clouds can contribute to a significant radiative forcing.

scholarly journals Unanticipated Side Effects of Stratospheric Albedo Modification Proposals Due to Aerosol Composition and Phase

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Daniel J. Cziczo ◽  
Martin J. Wolf ◽  
Blaž Gasparini ◽  
Steffen Münch ◽  
Ulrike Lohmann
Keyword(s):  
Greenhouse Gases ◽  
Radiative Forcing ◽  
Unintended Consequences ◽  
Cloud Formation ◽  
Aerosol Composition ◽  
Radiative Balance ◽  
Nucleation Sites ◽  
Polar Stratospheric Cloud ◽  
Reduction Of Emissions ◽  
Cloud Ice

AbstractThe Earth has now warmed ~1.0 °C since the period 1850–1900, due in large part to the anthropogenic addition of greenhouse gases to the atmosphere. Most strategies to address this warming have called for a reduction of emissions and, often, accompanying removal of greenhouse gases. Other proposals suggest masking the increased radiative forcing by an increase in particles and/or clouds to increase scattering of incoming solar radiation. Two related recent proposals have suggested addition of calcite particles to the stratosphere, which one model suggests may enhance ozone. Here we show that the interaction of calcite with acidic materials in the stratosphere results in a more complex aerosol than has been previously considered, including aqueous and hydrate phases that can lead to ozone loss. Our study suggests particle addition to the stratosphere could also perturb global radiative balance by affecting high altitude cloud formation and properties. Experimental and modeling results suggest particles will act as the nucleation sites for polar stratospheric cloud ice and, after sedimentation into the troposphere, impact cirrus clouds in the absence of other efficient ice nucleating particles. These results show that an overly simplistic set of assumptions regarding intentional particle emissions to the atmosphere can lead to incorrect estimates of the radiative effect and fail to identify unintended consequences.

Aerosol-driven droplet concentrations dominate coverage and water of oceanic low-level clouds

Science ◽  
2019 ◽  
Vol 363 (6427) ◽  
pp. eaav0566 ◽  
Author(s):  
Daniel Rosenfeld ◽  
Yannian Zhu ◽  
Minghuai Wang ◽  
Youtong Zheng ◽  
Tom Goren ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Cloud Cover ◽  
Climate Models ◽  
Cloud Condensation Nuclei ◽  
Climate Forcing ◽  
Present Climate ◽  
Cloud Radiative Forcing ◽  
Cloud Properties ◽  
Aerosol Effects ◽  
Meteorological Effects

A lack of reliable estimates of cloud condensation nuclei (CCN) aerosols over oceans has severely limited our ability to quantify their effects on cloud properties and extent of cooling by reflecting solar radiation—a key uncertainty in anthropogenic climate forcing. We introduce a methodology for ascribing cloud properties to CCN and isolating the aerosol effects from meteorological effects. Its application showed that for a given meteorology, CCN explains three-fourths of the variability in the radiative cooling effect of clouds, mainly through affecting shallow cloud cover and water path. This reveals a much greater sensitivity of cloud radiative forcing to CCN than previously reported, which means too much cooling if incorporated into present climate models. This suggests the existence of compensating aerosol warming effects yet to be discovered, possibly through deep clouds.

Simulating mixed-phase cloud properties with ICON around the CAPRICORN field campaign at the kilometre scale

2020 ◽  
Author(s):  
Veeramanikandan Ramadoss ◽  
Alain Protat ◽  
Yi Huang ◽  
Steven Siems ◽  
Anna Possner
Keyword(s):  
Southern Ocean ◽  
Climate Models ◽  
Cold Front ◽  
Meteorological Data ◽  
Short Wave ◽  
Atmospheric Composition ◽  
Wave Radiation ◽  
Limited Area ◽  
Field Campaign ◽  
Radiative Balance

<p>Stratocumulus clouds are low-level boundary layer clouds that cover 23% of the ocean surface on a global average, with a mean coverage of 25% to 40% in the mid-latitude oceans. These clouds affect Earth's radiative balance due to their strong radiative cooling effect. Many climate models underestimate the reflection of short wave radiation over the Southern Ocean (SO) which results in a positive mean bias of 2K in the annual mean SST in the mid-latitudes of the southern hemisphere. The organization, cloud field properties and the cloud radiative effects of these clouds occur at the lee of cold front in the SO are analyzed in this study. At this conference, we will present preliminary results.<br>Real case simulations are performed in this study by using ICON - LAM (Icosahedral Nonhydrostatic - Limited Area Model) with two-way nesting domains of resolutions 4.9 km to 2.4 km to 1.2 km. The initial and lateral boundary conditions for the model are derived from IFS meteorological data. CAPRICORN (Clouds, Aerosols, Precipitation, Radiation, and Atmospheric Composition over the Southern Ocean) field campaign that took place during March and April 2016 has continuously observed the open-cell and stratocumuli using shipborne radars and lidars on 26 and 27 March 2016 at the lee of a cold front between 47ºS 144ºE and 45ºS 146ºE (South of Tasmania). The results are evaluated quantitatively and qualitatively with the shipborne observations and HIMAWARI satellite retrievals respectively.</p>

New evidence of soot particles affecting past and future cloud formation and climate

2020 ◽  
Author(s):  
Ulrike Lohmann ◽  
Franz Friebel ◽  
Zamin A. Kanji ◽  
Fabian Mahrt ◽  
Amewu A. Mensah ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Cloud Condensation Nuclei ◽  
Critical Role ◽  
Carbon Dioxide Concentration ◽  
Radiative Properties ◽  
Cloud Formation ◽  
Condensation Nuclei ◽  
Soot Particles

<p>Clouds play a critical role in the hydrological cycle and modulating the Earth’s climate via precipitation and radiative forcing. Aerosol particles acting as cloud condensation nuclei and ice nucleating particles aid in cloud formation, shaping their microphysical structure. Previously thought to be unimportant for cloud formation, soot particles that undergo oxidation by ozone and/or aging with aqueous sulfuric acid result in being both good centers for cloud droplets and ice crystals formation. However, the associated changes in cloud radiative properties and the consequences for Earth’s climate remain uncertain, because these processes have not been considered in global climate models. Here we present both past and future global climate simulations, which for the first time consider the effect of such aged soot particles as cloud condensation nuclei and ice nucleating particles. Our results constitute the first evidence that aging of soot particles produce a 0.2 to 0.25 Wm<sup>-2</sup> less negative shortwave indirect aerosol forcing compared to previous estimates. We also conducted equilibrium climate sensitivity simulations representing a future warmer climate in which the carbon dioxide concentration is doubled compared to pre-industrial levels. Accounting for these soot aging processes significantly exacerbates the global mean surface temperature increase by 0.4 to 0.5 K. Thus, reducing emissions of soot particles will be beneficial for many aspects including air pollution and future climate.</p><p> </p>

scholarly journals Why do the dark and light ogives of Forbes bands have similar surface mass balances?

2018 ◽  
Vol 64 (244) ◽  
pp. 236-246 ◽  
Author(s):  
C. VINCENT ◽  
M. DUMONT ◽  
D. SIX ◽  
F. BRUN ◽  
G. PICARD ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Short Wave ◽  
Wave Radiation ◽  
Mass Balances ◽  
Surface Mass ◽  
Significant Difference ◽  
Radiative Impacts ◽  
The Difference ◽  
Glacier Flow

ABSTRACTBand ogives are a striking and enigmatic feature of Mer de Glace glacier flow. The surface mass balances (SMBs) of these ogives have been thoroughly investigated over a period of 12 years. We find similar cumulative SMBs over this period, ranging between −64.1 and −66.2 m w.e., on the dark and light ogives even though the dark ogive albedo is ~40% lower than that of the light ogives. We, therefore, looked for another process that could compensate for the large difference of absorbed short-wave radiation between dark and light ogives. Based on in situ roughness measurements, our numerical modeling experiments demonstrate that a significant difference in turbulent flux over the dark and light ogives due to different surface roughnesses could compensate for the difference in radiative forcing. Our results discard theories for the genesis of band ogives that are based on the assumption of a strong ice ablation contrast between dark and light ogives. More generally, our study demonstrates that future roughness changes are as important to analyze as the radiative impacts of a potential increase of aerosols or debris at the surface of glaciers.

scholarly journals Aerosol nucleation and its role for clouds and Earth's radiative forcing in the aerosol-climate model ECHAM5-HAM

2010 ◽  
Vol 10 (22) ◽  
pp. 10733-10752 ◽  
Author(s):  
J. Kazil ◽  
P. Stier ◽  
K. Zhang ◽  
J. Quaas ◽  
S. Kinne ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Radiative Forcing ◽  
Climate Model ◽  
Laboratory Data ◽  
Short Wave ◽  
Wave Radiation ◽  
Short Wave Radiation ◽  
Model Aerosol ◽  
The Individual ◽  
Lifetime Effects

Abstract. Nucleation from the gas phase is an important source of aerosol particles in the Earth's atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosol-climate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms for clouds and the Earth's radiative forcing. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual nucleation processes to total absorbed solar short-wave radiation via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are −1.15 W/m2 for charged H2SO4/H2O nucleation, −0.235 W/m2 for cluster activation, and −0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is −2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks and interactions in the model. Aerosol nucleation contributes over the oceans with −2.18 W/m2 to total absorbed solar short-wave radiation, compared to −0.37 W/m2 over land. We explain the higher effect of aerosol nucleation on Earth's radiative forcing over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local measurements: over southern Finland, where cluster activation proceeds efficiently, we find that charged nucleation of sulfuric acid and water contributes on average less than 10% to ultrafine aerosol concentrations, in good agreement with observations.

scholarly journals Analysis of polarimetric satellite measurements suggests stronger cooling due to aerosol-cloud interactions

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Otto P. Hasekamp ◽  
Edward Gryspeerdt ◽  
Johannes Quaas
Keyword(s):  
Radiative Forcing ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Cloud Formation ◽  
Anthropogenic Aerosol ◽  
Intergovernmental Panel ◽  
Aerosol Cloud ◽  
Cloud Properties ◽  
Aerosol Cloud Interactions ◽  
Aerosol Emissions

AbstractAnthropogenic aerosol emissions lead to an increase in the amount of cloud condensation nuclei and consequently an increase in cloud droplet number concentration and cloud albedo. The corresponding negative radiative forcing due to aerosol cloud interactions (RF$${}_{{\rm{aci}}}$$aci) is one of the most uncertain radiative forcing terms as reported in the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Here we show that previous observation-based studies underestimate aerosol-cloud interactions because they used measurements of aerosol optical properties that are not directly related to cloud formation and are hampered by measurement uncertainties. We have overcome this problem by the use of new polarimetric satellite retrievals of the relevant aerosol properties (aerosol number, size, shape). The resulting estimate of RF$${}_{{\rm{aci}}}$$aci = −1.14 Wm$${}^{{\rm{-2}}}$$-2 (range between −0.84 and −1.72 Wm$${}^{{\rm{-2}}}$$-2) is more than a factor 2 stronger than the IPCC estimate that includes also other aerosol induced changes in cloud properties.

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