Stratospheric ozone depletion during the 1995–1996 Arctic winter: 3-D simulations on the potential role of different PSC types

Abstract

Abstract. The sensitivity of modelled ozone depletion in the winter Arctic stratosphere to different assumptions of prevalent PSC types and PSC formation mechanisms is investigated. Three-dimensional simulations of the winter 1995/96 are performed with the COlogne Model of the Middle Atmosphere (COMMA) by applying different PSC microphysical schemes. Model runs are carried out considering either liquid or solid PSC particles or a combined microphysical scheme. These simulations are then compared to a model run which only takes into account binary sulfate aerosols. The results obtained with the three-dimensional model agree with trajectory-box simulations performed in previous studies. The simulations suggest that conditions appropriate for type Ia PSC existence (T < T NAT ) occur over longer periods and cover larger areas when compared to conditions of potential type Ib PSC existence. Significant differences in chlorine activation and ozone depletion occur between the simulations including only either liquid or solid PSC particles. The largest differences, occurring over large spatial scales and during prolonged time periods, are modelled first, when the stratospheric temperatures stay below T NAT , but above the threshold of effective liquid particle growth and second, in the case of the stratospheric temperatures remaining below this threshold, but not falling below the ice frost point. It can be generally concluded from the present study that differences in PSC microphysical schemes can cause significant fluctuations in ozone depletion modelled for the winter Arctic stratosphere.

Chemical state estimation for the middle atmosphere by four‐dimensional variational data assimilation: System configuration

“…The reaction scheme comprises 167 gas‐phase reactions (see Tables 1 and 2) and 10 heterogeneous reactions on surfaces of Polar Stratospheric Cloud (PSC) particles and in sulphate aerosol droplets (see Table 3). The mechanism follows partly Hendricks et al [2001], with extensions for the upper stratosphere and lower mesosphere. Reaction velocities follow recommendations from Sander et al [2006].…”

“…N sulf = 5 cm −3 was taken as a representative number density for stratospheric aerosols [ Deshler et al , 2003]. Following Hendricks et al [2001], PSC particle number densities are prescribed by N NAT = 1 cm −3 and N ice = 0.01 cm −3 .…”

Microphysical modeling of a midlatitude “polar stratospheric cloud” event: Comparisons against multiwavelength ground‐based and spaceborne lidar data

“…The region where PSC fields are the most difficult to model is the Arctic lower stratosphere [ Hendricks et al , 2001; Carslaw et al , 2002; Fueglistaler et al , 2003]. In contrast to the Southern Hemisphere, the Arctic temperatures are usually quite variable in space and time.…”

Heterogeneous Nucleation of Nitric Acid Trihydrate on Clay Minerals: Relevance to Type Ia Polar Stratospheric Clouds

“…In addition to chlorine activation, PSC particles may also promote polar ozone destruction by denitrifying the polar stratosphere. , The degree of denitrification and halogen activation on PSC particles is important for determining the severity of polar ozone loss and depends strongly on the formation mechanism and type of PSC. , Large NAT particles are more efficient at depleting nitric acid than either NAD or supercooled ternary solutions. ,, Severe denitrification occurs when NAT particles grow to sizes larger than 5 μm in radius. , Currently, there is no established nucleation mechanism that sufficiently explains the formation of these large NAT particles. ,, Homogeneous nucleation from supercooled ternary solutions is probably too slow to form large nitric acid-containing particles . Additionally, previous field studies have found that the presence of ice was not necessary for the formation of large NAT particles .…”

“…4,15 The degree of denitrification and halogen activation on PSC particles is important for determining the severity of polar ozone loss and depends strongly on the formation mechanism and type of PSC. 16,17 Large NAT particles are more efficient at depleting nitric acid than either NAD or supercooled ternary solutions. 12,18,19 Severe denitrification occurs when NAT particles grow to sizes larger than 5 µm in radius.…”