Sensitivity of aerosol concentrations and cloud properties to nucleation and secondary organic distribution in ECHAM5-HAM global circulation model

Abstract

Abstract. The global aerosol-climate model ECHAM5-HAM was modified to improve the representation of new particle formation in the boundary layer. Activation-type nucleation mechanism was introduced to produce observed nucleation rates in the lower troposphere. A simple and computationally efficient model for biogenic secondary organic aerosol (BSOA) formation was implemented. Here we study the sensitivity of the aerosol and cloud droplet number concentrations (CDNC) to these additions. Activationtype nucleation significantly increases aerosol number concentrations in the boundary layer. Increased particle number concentrations have a significant effect also on cloud droplet number concentrations and therefore on cloud properties. We performed calculations with activation nucleation coefficient values of 2×10 −7 s −1 , 2×10 −6 s −1 and 2×10 −5 s −1 to evaluate the sensitivity to this parameter. For BSOA we have used yields of 0.025, 0.07 and 0.15 to estimate the amount of monoterpene oxidation products available for condensation. The hybrid BSOA formation scheme induces large regional changes to size distribution of organic carbon, and therefore affects particle optical properties and cloud droplet number concentrations locally. Although activation-type nuCorrespondence to: R. Makkonen (risto.makkonen@helsinki.fi) cleation improves modeled aerosol number concentrations in the boundary layer, the use of a global activation coefficient generally leads to overestimation of aerosol number. Overestimation can also arise from underestimation of primary emissions.

General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales

“…The maps Annual zonal average concentrations (cm −3 STP (1013.25 hPa, 273.15 K)) of (a) nucleation mode aerosol number; (b) sum of Aitken mode number concentration: centre ones experiment A1 (using activation nucleation in addition to the standard binary nucleation) as predicted by the GCM ECHAM5-HAM; and right panels show the ratio of the yearly averages for experiments B (only binary nucleation) and A1. Notice the different color scales between figures (published in Makkonen et al, 2009). of average N 50 and N 100 concentration fields have in general similar features, while the spatial distribution of N 3 is quite different. The average ground concentrations over the whole modelling domain are predicted to be 6667, 1465, and 390 cm −3 for N 3 , N 50 , and N 100 , respectively.…”

Boundary layer nucleation as a source of new CCN in savannah environment

“…Lihavainen et al, 2003;Laaksonen et al, 2005;Kuang et al, 2009;Wiedensohler et al, 2009). The potential importance of atmospheric new particle formation for regional and global CCN budgets has been demonstrated also using global models (Spracklen et al, 2008;Makkonen et al, 2009Makkonen et al, , 2012Merikanto et al, 2009;Adams, 2007, 2009;Wang and Penner, 2009;Yu and Luo, 2009;Kazil et al, 2010;Luo and Yu, 2011), even though uncertainties related to these studies are still large .…”

A pathway analysis of global aerosol processes

“…ECHAM-HAM has been used to study non-linearities in aerosol response due to emission changes (Stier et al, 2006a), aerosol effects in a transient climate (Stier et al, 2006b), aerosol activation and cloudprocessing (Roelofs et al, 2006), aerosol indirect effects (Lohmann et al, 2007), the impact of pollution mitigation on climate forcing (Kloster et al, 2008), the impact of volcanic eruptions on climate (Niemeier et al, 2009;Timmreck et al, 2010), the impact of aerosol nucleation on radiative forcing (Makkonen et al, 2009;Kazil et al, 2010) and brightening of surface radiation due to aerosols (Folini and Wild, 2011), climate forcing due to secondary organic aerosols (O'Donnell et al, 2011) and aerosol indirect effects due to shipping emissions (Peters et al, 2012) to name but a few studies. The general circulation model ECHAM was developed at the Max Planck Institute for Meteorology and evolved from the model at the European Centre for Medium-Range Weather Forecasting.…”