Analytical studies of the cloud droplet spectral dispersion influence on the first indirect aerosol effect

Xie, Xiaoning; Liu, Xiaodong

doi:10.1007/s00376-012-2141-5

Cited by 12 publications

(7 citation statements)

References 27 publications

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“…The change reduces the aerosol‐cloud albedo forcing and weakens the net aerosol ERF by +0.64 W/m 2 . There is an increasing body of literature (Liu & Daum, ; Liu et al, ; Lohmann & Feichter, ; Peng & Lohmann, ; Rotstayn & Liu, ; Xie & Liu, ) highlighting the potentially important role of this process in ACIs and its ability to explain the lack of significant hemispheric differences in cloud brightness (Liu et al, ; Schwartz, ). Indeed, here we find significant improvement in the asymmetric hemispheric biases in GA7 when this process is included.…”

Section: Discussionmentioning

confidence: 98%

Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1

Mulcahy

Jones

Sellar

et al. 2018

J Adv Model Earth Syst

166

212

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Aerosol processes and, in particular, aerosol‐cloud interactions cut across the traditional physical‐Earth system boundary of coupled Earth system models and remain one of the key uncertainties in estimating anthropogenic radiative forcing of climate. Here we calculate the historical aerosol effective radiative forcing (ERF) in the HadGEM3‐GA7 climate model in order to assess the suitability of this model for inclusion in the UK Earth system model, UKESM1. The aerosol ERF, calculated for the year 2000 relative to 1850, is large and negative in the standard GA7 model leading to an unrealistic negative total anthropogenic forcing over the twentieth century. We show how underlying assumptions and missing processes in both the physical model and aerosol parameterizations lead to this large aerosol ERF. A number of model improvements are investigated to assess their impact on the aerosol ERF. These include an improved representation of cloud droplet spectral dispersion, updates to the aerosol activation scheme, and black carbon optical properties. One of the largest contributors to the aerosol forcing uncertainty is insufficient knowledge of the preindustrial aerosol climate. We evaluate the contribution of uncertainties in the natural marine emissions of dimethyl sulfide and organic aerosol to the ERF. The combination of model improvements derived from these studies weakens the aerosol ERF by up to 50% of the original value and leads to a total anthropogenic historical forcing more in line with assessed values.

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Section: Discussionmentioning

confidence: 98%

Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1

Mulcahy

Jones

Sellar

et al. 2018

J Adv Model Earth Syst

166

212

View full text Add to dashboard Cite

show abstract

“…Liu and Daum [9] found that the radiative cooling, in consideration of the dispersion effect changing R e , was only 10-80% of the Twomey effect, when N c was increased by 15% (based on 100 cm −3 of N c ). Xie and Liu [13] showed that the cloud radiative forcing induced by aerosols for different ε−N c relationships varied from the case without dispersion effect (ε = 0) by −29.1-25.2%. Other earlier studies [14][15][16] pointed out that models overestimate the indirect radiative forcing by 15-35% due to calculations without the dispersion effect.…”

Section: Introductionmentioning

confidence: 99%

An Observational Study on Cloud Spectral Width in North China

Wang

Niu

et al. 2019

Atmosphere

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Cloud droplet size distribution (CDSD) is a critical characteristic for a number of processes related to clouds, considering that cloud droplets are formed in different sizes above the cloud-base. This paper analyzes the in-situ aircraft measurements of CDSDs and aerosol concentration ( N a ) performed in stratiform clouds in Hebei, China, in 2015 to reveal the characteristics of cloud spectral width, commonly known as relative dispersion ( ε , ratio of standard deviation (σ) to mean radius (r) of the CDSD). A new algorithm is developed to calculate the contributions of droplets of different sizes to ε . It is found that small droplets with the size range of 1 to 5.5 μm and medium droplets with the size range of 5.5 to 10 μm are the major contributors to ε, and the medium droplets generally dominate the change of ε. The variation of ε with N a can be well explained by comparing the normalized changes of σ and r ( k σ / σ and k r / r ), rather than k σ and k r only ( k σ is Δσ/Δ N a and k r is Δr/Δ N a ). From the perspective of external factors affecting ε change, the effects of N a and condensation are examined. It is found that ε increases initially and decreases afterward as N a increases, and “condensational broadening” occurs up to 1 km above cloud-base, potentially providing observational evidence for recent numerical simulations in the literature.

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“…As a result of increased cloud droplet activation and water vapor competition, condensation growth of cloud droplet become complicated, resulting in a decrease in the particle size of cloud droplets. More and smaller cloud droplets induced by aerosols can hinder the auto-conversion process of clouds from raining (Xie et al, 2013). The auto-conversion intensities of both schemes decades with increasing concentrations of CCN, as shown in Figure 11.…”

Section: Differences In Convection Developmentmentioning

confidence: 95%

The numerical study on the sensitivity of different auto-conversion parameterization to CCN concentration

Liu²,

Yuan³

2023

Front. Environ. Sci.

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The auto-conversion from cloud droplet to raindrop is a process whereby rain drops formed by collision-coalescence of cloud droplets. As an essential link connecting aerosol-cloud interaction, it significantly influences the changes in cloud morphology and precipitation. In order to explore the sensitivity of auto-conversion schemes to cloud condensation nuclei (CCN) concentration, using the auto-conversion scheme in the Thompson scheme (TH-AU) and Milbrandt-Yau scheme (MY-AU), we set four groups of CCN concentrations to simulate a strong convection process in Ningxia region of China. The results show that: The sensitivity of different auto-conversion schemes to changes in CCN concentrations varies significantly, and the aerosol-induced changes in precipitation and convection strongly depend on the auto-conversion scheme. With the increase of CCN concentration, the mixing ratio of cloud droplets increases, and the particle size decreases, resulting in a decrease in the auto-conversion intensity for the two schemes, which makes more supercooled water participate in the ice phase process. Compared with the TH-AU, the MY-AU has lower auto-conversion intensity at the same CCN concentration, the proportion of supercooled cloud droplets participating in the ice phase process is higher than that in the TH-AU, which leads to the raindrop mixing ratio of 4000–6000 m in MY-AU is lower than that in TH-AU at the same CCN concentration, and the mixing ratio of ice phase particles in MY-AU scheme is higher in the convective mature stage, especially snow and graupel particles, and the graupel particle generation height of MY-AU is lower than that of TH-AU. In terms of dynamic structure, with the increase of CCN concentration, more cloud droplets are activated and frozen which makes the enhancement of updraft mainly occur in the upper layer in both schemes, but the stronger gravitational drag caused by graupel particles in MY-AU may enhance the downdraft in the middle and lower layers, which makes the convection of MY-AU decay early at higher CCN concentration. In addition, changes in microphysical processes also lead to differences in cumulative precipitation and accumulated ground graupel-fall of the two schemes. The cumulative precipitation and the accumulated ground graupel-fall of the MY-AU decrease strongly with the increase of CCN concentration because the warm rain process of MY-AU is strongly inhibited. Compared with MY-AU, the warm rain process of TH-AU is not significantly inhibited, which leads to the cumulative precipitation and the accumulated ground graupel-fall of the TH-AU scheme increases when the CCN concentration is 50–200 cm−3 and slightly decreases when the CCN concentration is 200–10000 cm−3.

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Analytical studies of the cloud droplet spectral dispersion influence on the first indirect aerosol effect

Cited by 12 publications

References 27 publications

Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1

Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1

An Observational Study on Cloud Spectral Width in North China

The numerical study on the sensitivity of different auto-conversion parameterization to CCN concentration

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