This article presents the Size-Composition Resolved Aerosol Model (SCRAM) for simulating the dynamics of externally mixed atmospheric particles. The model is first validated by comparison with a reference solution and with results of simulations using internally mixed particles. Then, the importance of representing the mixing state when modelling atmospheric aerosol concentrations is investigated in a box model simulation using data representative of air pollution in Greater Paris.

We describe and test a parallel 2-D subglacial hydrology model. Such a hydrology model describes the motion of liquid water, and its pressure, underneath ice sheets and glaciers. Model goals include conserving the mass of water and generating an estimate of the ice basal shear stress. This hydrology model describes the subglacier as a layer of till and linked cavities, but it does not include conduits.

We describe a spectral nudging technique to constrain the large spatial structures of an atmospheric general circulation model (ACCESS1.3) towards an observational product (ERA-Interim). This has a number of applications for model development and scientific studies. This paper shows potential benefits of using the spectral nudging over the traditional Newtonian relaxation method.

This paper introduces a free and open-source C++ library of algorithms for representing cloud microphysics in numerical models. In the current release, the library covers three warm-rain schemes: the single- and double-moment bulk schemes, and the particle-based scheme with Monte Carlo coalescence. The three schemes are intended for modelling frameworks of different dimensionalities and complexities ranging from parcel models to multi-dimensional cloud-resolving (e.g. large-eddy) simulations.

We present a new approach to assess karstic groundwater recharge over Europe and the Mediterranean. Cluster analysis is used to subdivide all karst regions into four typical karst landscapes and to simulate karst recharge with a process-based karst model. We estimate its parameters by a combination of a priori information and observations of soil moisture and evapotranspiration. Independent observations of recharge that present large-scale models significantly under-estimate karstic recharge.

Unstructured meshes allow multi-resolution modeling of ocean dynamics. Sea ice models formulated on unstructured meshes are a necessary component of ocean models intended for climate studies. This work presents a description of a finite-element sea ice model which is used as a component of a finite-element sea ice ocean circulation model. The principles underlying its design can be of interest to other groups pursuing ocean modelling on unstructured meshes.

A new method is presented for allocating the anthropogenic part of a pollutant concentration to the sources responsible. The method requires integrating sensitivity coefficients over a range of emissions defined by an emission-control strategy. A simplified photochemical model is used to evaluate options for the numerical integration and the dependence of the source contributions on the control strategy. Results are presented for ozone, formaldehyde, nitrogen dioxide, and nitric acid.

We present and demonstrate Version 2.0 of the Emission Scenario Projection (ESP) method. This method produces multi-decadal air pollutant emission projections suitable for air quality modeling. The method focuses on energy-related emissions, including those from the electric sector, buildings, industry and transportation. ESP v2.0 enhances ESP v1.0 by taking population growth, migration and land use change into consideration.

Projecting biogeochemical responses to environmental change requires multi-scaled perspectives. However, microbes, the drivers of soil organic matter decomposition and stabilization, remain notably absent from models used to project carbon cycle–climate feedbacks. Here, we apply and evaluate representations of microbial functional diversity across scales and find that such representations may be critical to accurately project soil carbon dynamics in a changing world.

We performed high-resolution numerical simulations of nonlinear acoustic-gravity waves (AGWs) at altitudes 0–500km and compared them with analytical polarization relations of linear AGW theory. After some transition time, t > te, the numbers of numerically simulated and analytical pairs of AGW parameters, which are equal to confidence 95%, are larger at altitudes 30-60km and are smaller at t < te. The differences reveal circumstances where numerical simulations of waves are required.

An extended vertical grid, which reaches the lower stratosphere, for the regional atmospheric model COSMO was developed. This extended vertical grid was used in model runs simulating almost a full year. The model output was then validated using temperature and relative humidity measurements taken from synoptic radiosondes. Using this extended vertical grid, the model was found to run stably and produce realistic values.

WRFPLUS-Chem is a coupled meteorology-chemistry adjoint and tangent linear model, with applications in sensitivity analysis and four-dimensional variational data assimilation. The linearized models are verified against finite difference approximations from the nonlinear forward model, WRF-Chem. A new checkpointing scheme enables data assimilation beyond 6h. New capabilities are demonstrated in an emission sensitivity study.

Here we present a concise interface to the NetCDF library designed to simplify reading and writing tasks of up to 6-D arrays in Fortran programs.

We have showed that a coupled modelling system is beneficial in the sense that more complex processes can be included to better represent the aerosol processes starting from their formation, their interactions with clouds and provide better estimate of radiative forcing. Using this model set up, we estimated an annual mean 'indirect' radiative forcing of -0.64W/m2. This means that aerosols, solely by their capability of altering the microphysical properties of clouds can cool the Earth system.