Impacts of Sub-grid Ice Cloud Physics in a Turbulence Scheme on High Clouds and their Response to Global Warming

Abstract Data from global high-resolution, nonhydrostatic simulations, covering a 1-yr period and with horizontal grid sizes of 7 and 14 km, were analyzed to evaluate the response of high cloud to global warming. The results indicate that, in a warmer atmosphere, high-cloud cover increases robustly and associated longwave (LW) cloud radiative forcing (CRF) increases on average. To develop a better understanding of high-cloud responses to climate change, the geographical distribution of high-cloud size obtained from the model was analyzed and compared with observations. In warmer atmospheres, the contribution per cloud to CRF decreases for both the LW and shortwave (SW) components. However, because of significant increases in the numbers of high clouds in almost all cloud size categories, the magnitude of both LW and SW CRF increases in the simulations. In particular, the contribution from an increase in the number of smaller clouds has more effect on the CRF change. It was also found that the ice and liquid water paths decrease in smaller clouds and that particularly the former contributes to reduced LW CRF per high cloud.

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The importance of interstitial particle scavenging by cloud droplets in shaping the remote aerosol size distribution and global aerosol-climate effects

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-6147-2015 ◽

2015 ◽

Vol 15 (11) ◽

pp. 6147-6158 ◽

Cited By ~ 16

Author(s):

J. R. Pierce ◽

B. Croft ◽

J. K. Kodros ◽

S. D. D'Andrea ◽

R. V. Martin

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Indirect Effect ◽

Cloud Droplet ◽

Aerosol Size Distribution ◽

Cloud Physics ◽

Cloud Droplets ◽

Aerosol Indirect Effect ◽

Ice Cloud ◽

Coagulation Process

Abstract. In this paper, we investigate the coagulation of interstitial aerosol particles (particles too small to activate to cloud droplets) with cloud drops, a process often ignored in aerosol-climate models. We use the GEOS-Chem-TOMAS (Goddard Earth Observing System-Chemistry TwO-Moment Aerosol Sectional) global chemical transport model with aerosol microphysics to calculate the changes in the aerosol size distribution, cloud-albedo aerosol indirect effect, and direct aerosol effect due to the interstitial coagulation process. We find that inclusion of interstitial coagulation in clouds lowers total particle number concentrations by 15–21% globally, where the range is due to varying assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The interstitial coagulation process lowers the concentration of particles with dry diameters larger than 80 nm (a proxy for larger CCN) by 10–12%. These 80 nm particles are not directly removed by the interstitial coagulation but are reduced in concentration because fewer smaller particles grow to diameters larger than 80 nm. The global aerosol indirect effect of adding interstitial coagulation varies from +0.4 to +1.3 W m−2 where again the range depends on our cloud assumptions. Thus, the aerosol indirect effect of this process is significant, but the magnitude depends greatly on assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The aerosol direct effect of the interstitial coagulation process is minor (< 0.01 W m−2) due to the shift in the aerosol size distribution at sizes where scattering is most effective being small. We recommend that this interstitial scavenging process be considered in aerosol models when the size distribution and aerosol indirect effects are important.

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The importance of interstitial particle scavenging by cloud droplets in shaping the remote aerosol size distribution and global aerosol-climate effects

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-5589-2015 ◽

2015 ◽

Vol 15 (4) ◽

pp. 5589-5618

Author(s):

J. R. Pierce ◽

B. Croft ◽

J. K. Kodros ◽

S. D. D'Andrea ◽

R. V. Martin

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Indirect Effect ◽

Cloud Droplet ◽

Aerosol Size Distribution ◽

Cloud Physics ◽

Cloud Droplets ◽

Aerosol Indirect Effect ◽

Ice Cloud ◽

Coagulation Process

Abstract. In this paper, we investigate the coagulation of interstitial aerosol particles (particles too small to activate to cloud droplets) with cloud drops, a process often ignored in aerosol-climate models. We use the GEOS-Chem-TOMAS global chemical transport model with aerosol microphysics to calculate the changes in the aerosol size distribution, cloud-albedo aerosol indirect effect, and direct aerosol effect due to the interstitial coagulation process. We find that inclusion of interstitial coagulation in clouds lowers total particle number concentrations by 15–21% globally, where the range is due to varying assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The interstitial coagulation process lowers the concentration of particles with dry diameters larger than 80 nm (a proxy for larger CCN) by 10–12%. These 80 nm particles are not directly removed by the interstitial coagulation, but are reduced in concentration because fewer smaller particles grow to diameters larger than 80 nm. The global aerosol indirect effect of adding interstitial coagulation varies from +0.4 to +1.3 W m−2 where again the range depends on our cloud assumptions. Thus, the aerosol indirect effect of this process is significant, but the magnitude depends greatly on assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The aerosol direct effect of interstitial coagulation process is minor (<0.01 W m−2) due to the shift in the aerosol size distribution at sizes where scattering is most effective being small. We recommend that this interstitial scavenging process be considered in aerosol models when the size distribution and aerosol indirect effects are important.

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Comparison of High-Cloud Characteristics as Estimated by Selected Spaceborne Observations and Ground-Based Lidar Datasets

Journal of Applied Meteorology and Climatology ◽

10.1175/2009jamc1964.1 ◽

2009 ◽

Vol 48 (6) ◽

pp. 1142-1160 ◽

Cited By ~ 4

Author(s):

Artemio Plana-Fattori ◽

Gérard Brogniez ◽

Patrick Chervet ◽

Martial Haeffelin ◽

Olga Lado-Bordowsky ◽

...

Keyword(s):

Laser Altimeter ◽

Infrared Observation ◽

High Cloud ◽

Ice Cloud ◽

Cloud Characteristics ◽

Ground Based Lidar ◽

Observation Strategies ◽

High Clouds ◽

Lidar Observations

Abstract The characterization of high clouds as performed from selected spaceborne observations is assessed in this article by employing a number of worldwide ground-based lidar multiyear datasets as reference. Among the latter, the ground lidar observations conducted at Lannion, Bretagne (48.7°N, 3.5°W), and Palaiseau, near Paris [the Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA) observatory: 48.7°N, 2.2°E], both in France, are discussed in detail. High-cloud altitude statistics at these two sites were found to be similar. Optical thicknesses disagree, and possible reasons were analyzed. Despite the variety of instruments, observation strategies, and methods of analysis employed by different lidar groups, high-cloud optical thicknesses from the Geoscience Laser Altimeter System (GLAS) on board the Ice, Cloud and land Elevation Satellite (ICESat) were found to be consistent on the latitude band 40°–60°N. Respective high-cloud altitudes agree within 1 km with respect to those from ground lidars at Lannion and Palaiseau; such a finding remains to be verified under other synoptic regimes. Mean altitudes of high clouds from Lannion and Palaiseau ground lidars were compared with altitudes of thin cirrus from the Television and Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) Path-B 8-yr climatology for a common range of optical thicknesses (0.1–1.4). Over both sites, the annual altitude distribution of thin high clouds from TOVS Path-B is asymmetric, with a peak around 8–9.5 km, whereas the distribution of high clouds retrieved from ground lidars seems symmetric with a peak around 9.5–11.5 km. Additional efforts in standardizing ground lidar observation and processing methods, and in merging high-cloud statistics from complementary measuring platforms, are recommended.

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Modelling ecosystem adaptation and dangerous rates of global warming

Emerging Topics in Life Sciences ◽

10.1042/etls20180113 ◽

2019 ◽

Vol 3 (2) ◽

pp. 221-231 ◽

Cited By ~ 4

Author(s):

Rebecca Millington ◽

Peter M. Cox ◽

Jonathan R. Moore ◽

Gabriel Yvon-Durocher

Keyword(s):

Climate Change ◽

Global Warming ◽

Diffusion Rate ◽

Individual Species ◽

Genetic Evolution ◽

Rates Of Change ◽

Rapid Climate Change ◽

Warming Climate ◽

Intraspecies Competition ◽

High Trait

Abstract We are in a period of relatively rapid climate change. This poses challenges for individual species and threatens the ecosystem services that humanity relies upon. Temperature is a key stressor. In a warming climate, individual organisms may be able to shift their thermal optima through phenotypic plasticity. However, such plasticity is unlikely to be sufficient over the coming centuries. Resilience to warming will also depend on how fast the distribution of traits that define a species can adapt through other methods, in particular through redistribution of the abundance of variants within the population and through genetic evolution. In this paper, we use a simple theoretical ‘trait diffusion’ model to explore how the resilience of a given species to climate change depends on the initial trait diversity (biodiversity), the trait diffusion rate (mutation rate), and the lifetime of the organism. We estimate theoretical dangerous rates of continuous global warming that would exceed the ability of a species to adapt through trait diffusion, and therefore lead to a collapse in the overall productivity of the species. As the rate of adaptation through intraspecies competition and genetic evolution decreases with species lifetime, we find critical rates of change that also depend fundamentally on lifetime. Dangerous rates of warming vary from 1°C per lifetime (at low trait diffusion rate) to 8°C per lifetime (at high trait diffusion rate). We conclude that rapid climate change is liable to favour short-lived organisms (e.g. microbes) rather than longer-lived organisms (e.g. trees).

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