Detailed Radiative Transfer Code Research Articles

Circumstellar water vapour in M-type AGB stars: constraints from H$_{\sf 2}$O(1$_{\sf 10}$–1$_{\sf 01}$) lines obtained with Odin

Context. A detailed radiative transfer code has been previously used to model circumstellar ortho-H2O line emission towards six M-type asymptotic giant branch stars using Infrared Space Observatory ...

Mesoscale model cloud scheme assessment using satellite observations

An exploratory evaluation of the explicit cloud scheme of the mesoscale nonhydrostatic (Meso‐NH) model has been conducted by comparing synthetic METEOSAT brightness temperatures (BT) to the observed ones. Three different meteorological situations are examined to illustrate the expected degree of accuracy in simulating realistic synthetic BTs in the midlatitude and in the subtropics, with a horizontal grid length ranging from 75 to 12 km. It is shown that the model to satellite approach, which combines the output from a bulk explicit cloud scheme routinely used in mesoscale simulations with a detailed radiative transfer code, offers the possibility of tuning a critical parameter. For instance, tests made with three different values of an ice to snow autoconversion threshold reveal a profound impact on the synthetic BT maps which results in unbiased differences with satellite observations when the appropriate value is selected. The main discrepancies that remain are partly due to errors in the vertical or horizontal placement of the cloud layer or in the amount of condensates, but also due to the lack of subgrid‐scale cloudiness in the model. A similar test conducted on the ice water and the liquid water paths confirms the fairly good agreement with retrievals from microwave observations. The paper concludes by discussing the need not only to extend the model to satellite approach to other well‐documented cases but also to derive diagnostics from deep convection scheme characteristics in order to include the radiative effect of the convective towers in the generation of synthetic BT maps.

An integrated air pollution modeling system for urban and regional scales: 1. Structure and performance

A new three‐dimensional air pollution modeling system is described for urban and regional air quality studies. The system includes four major components: a meteorological model, a tracer transport code, a chemical and aerosol microphysical model, and a radiative transfer code. The meteorological model solves the equations of fluid dynamics and thermodynamics over complex terrain and incorporates physical processes such as turbulent diffusion, water vapor condensation and precipitation, solar and infrared radiative transfer, and ground surface processes. The tracer transport code computes the dispersion of gases and aerosols throughout the atmosphere, including the effects of emission sources, and dry and wet deposition. The chemistry/aerosol model treats coupled gas‐phase photochemistry and aerosol microphysics and chemistry. Aerosol processes include nucleation, coagulation, condensational growth, evaporation, sedimentation, chemical equilibrium and aqueous chemistry. A detailed radiative transfer code is attached to the dynamical and chemical models. Absorption and scattering by gases and aerosols are explicitly treated to define photodissociation rates, heating and cooling profiles, and boundary layer visibilities. The integrated modeling system, which is referred to as the surface meteorology and ozone generation (SMOG) model, is shown to be a powerful tool for studying coupled dynamical, chemical, and microphysical processes on urban and regional scales.