Henning Rodhe | Stockholm University (original) (raw)

Papers by Henning Rodhe

Tropospheric Modelling and Emission Estimation, 1997

Contributions to Atmospheric Physics, 1999

Nature Reports Climate Change, 2007

The challenge of climate change research is to develop confident predictive capability. Given pro... more The challenge of climate change research is to develop confident predictive capability. Given prospective future emissions of greenhouse gases and other climate influencing substances such as aerosols, what changes in global mean surface temperature and other climate ...

Acidification of the environment--caused by the emission of sulfur and nitrogen oxides into the a... more Acidification of the environment--caused by the emission of sulfur and nitrogen oxides into the atmosphere--is one of the most serious side effects of industrialization. This volume provides a thorough introduction to this global problem. A basic overview describes acidification ...

Epic3journal of Geophysical Research 107 No D24 4744 P, Aug 1, 2002

We present simulations of the dust cycle during present and glacial climate states, using a model... more We present simulations of the dust cycle during present and glacial climate states, using a model, which explicitly simulates the control of dust emissions as a function of seasonal and interannual changes in vegetation cover. The model produces lower absolute amounts of dust emissions and deposition than previous simulations of the Last Glacial Maximum (LGM) dust cycle. However, the simulated 2- to 3-fold increase in emissions and deposition at the LGM compared to today, is in agreement with marine- and ice-core observations, and consistent with previous simulations. The mean changes are accompanied by a prolongation of the length of the season of dust emissions in most source regions. The increase is most pronounced in Asia, where LGM dust emissions are high throughout the winter, spring and summer rather than occurring primarily in spring as they do today. Changes in the seasonality of dust emissions, and hence atmospheric loading, interact with changes in the seasonality of precipitation, and hence of the relative importance of wet and dry deposition processes at high northern latitudes. As a result, simulated dust deposition rates in the high northern latitudes show high interannual variability. Our results suggest that the high dust concentration variability shown by the Greenland ice core records during the LGM is a consequence of changes in atmospheric circulation and precipitation locally rather than a result of changes in the variability of dust emissions.

Journal of the Atmospheric Sciences, Jan 30, 1981

We address the problem of using climatological data to estimate residence times in the atmosphere... more We address the problem of using climatological data to estimate residence times in the atmosphere of particles subjected to precipitation scavenging. Basic parameters are the scavenging coefficient , the rainfall intensity R and the length of dry and precipitation periods d and p. Previous models used to estimate residence times are reviewed and compared with `real' data. It is found that some of the earlier models substantially underestimate the average residence times, particularly for particles with a high value of the scavenging coefficient. An approximate model valid for long-lived particles with a relatively small scavenging coefficient [(5 h)1 at R = 1 mm h1] is formulated and tested. Daily rainfall values are adequate as input in this model but several years of data are required in order to wore at reasonable estimates of the residence time. The fundamental difficulty associated with all the models discussed is that a proper application requires Lagrangian rainfall data, i.e., information about the weather experienced by the particle as it is carried along with the winds, whereas virtually all data available from meteorological observations are obtained at fixed locations (Eulerian data).

The albedo is a key parameter in the radiative budget of the Earth and a primary determinant of t... more The albedo is a key parameter in the radiative budget of the Earth and a primary determinant of the planetary temperature and is therefore also central to questions regarding climate stability, climate change and climate sensitivity. Global climate models are essential for studying the albedo, and the parameters determining it (specifically clouds), on large spatial and temporal scales. Although models (here represented by the CMIP3 models) are able to capture the large-scale characteristics of the albedo, a bias is found between modelled and observed global albedo estimates, and on a regional scale particularly problematic regions can be identified. Many cloud parameters are poorly constrained by observations, and vary widely among models. This freedom of variability can be used in tuning models to the better constrained radiative budget, which may influence the model climate sensitivity. The effect can be kept small, compared to the range of climate sensitivities estimated by different models. Despite their different parameterizations of clouds, aerosols etc., models do have fundamental features in common, which can further the understanding of the real climate system. For instance, sensitivity to volcanic forcing is related to climate sensitivity in an ensemble of CMIP3 models. If this relation is valid for the real climate as well, observations of the volcanic sensitivity can help restrict estimates of climate sensitivity. The range of climate sensitivity estimates in models can largely be attributed to variations in cloud response to external forcing. In models with high (low) climate sensitivity, changes in cloud cover and cloud reflectivity generally enhance (counteract) a positive radiative forcing due to increased CO2 concentrations, feeding back on (damping) the warming, with a more (less) negative albedo response to the forcing. Cloud albedo is important in this regard, yet not well known. Regional cloud albedo, particularly for low-level marine stratiform clouds, can be estimated based on the relation between cloud fraction and total albedo, and among the CMIP3 models there are examples of good as well as poorer agreement with satellite-based observational estimates.

Climatic Change, 1990

The Gaia hypothesis proposed by Lovelock and Margulis presumes the existence of an unspecified bi... more The Gaia hypothesis proposed by Lovelock and Margulis presumes the existence of an unspecified biological means of ameliorating climate that has operated since the emergence of life 3500 Myr ago: Recently it was suggested that the mechanism of thermostasis may involve biospheric cycling of atmospheric carbon dioxide.

Unknown, Jun 1, 1989

The zonal average cloud distribution for the lower (approximately six km) troposphere is studied.... more The zonal average cloud distribution for the lower (approximately six km) troposphere is studied. It is derived from surface observations of cloud occurrence and the average vertical extent of clouds. Assessments of updraft velocities through convective clouds and lifetime estimates of stratiform clouds are used to calculate the average time that air spends in clouds and the time between successive cloud encounters, as a function of latitude and altitude. The inferred cloud data and satellite observations are compared. Data derived from calculations with a general circulation model and satellite observations do not show a good fit. The results lead to the conclusion that for such models an effort must be devoted to develop cloud parameterizations in order to produce cloud distributions as needed for global atmospheric chemistry modeling.

2009. Planetary boundaries:exploring the safe operating space for humanity. Ecology and Society 1... more 2009. Planetary boundaries:exploring the safe operating space for humanity. Ecology and Society 14(2): 32. [online]

Nature International Weekly Journal of Science, 1999

The climate in terms of global mean temperature has remained remarkably stable over the Holocene.... more The climate in terms of global mean temperature has remained remarkably stable over the Holocene. Given the major role that the planetary albedo plays in the global energy balance, it seems reasonable to beleive that the albedo too has remained stable. The albedo is determined by surface properties, as well as atmospheric factors, in particular clouds and their radiative properties. Before addressing questions of what processes and feedbacks may cause the stability in albedo and/or in climate, we need to have a clear picture of the albedo itself, and its spatial and temporal variability. The main source of global TOA radiative flux data is satellite measurements. As a complement to observations (that are sparse and can not be used for prediciton) models of the climate system can be a powerful tool. Naturally, since consistency is the simplest indicator of their accuracy, agreement between models and measurements is desired. In this study we consider measurements made by ERBE (Earth Radiation Budget Exepriment) and CERES (Clouds and the Earth's Radiant Energy System), as well as output from coordinated simulations with 20 different GCMs, performed in support of the IPCC 4th assessment report, and evaluate their different views of the albedo. In an attempt to bridge the gap between models and measurements, we carry out a systematic comparison between the albedo output from the 20 GCMs and the data from the ERBE and CERES satellite campaigns. Studying absolute levels, seasonal cycles, temporal trends and spatial distribution of albedo, we find that models and observations differ in many aspects. We hope that by pointing out and quantifying differences we can inspire both modellers and experimentalists to refine their products.

Data sets on horizontal and vertical distributions of sulfur and nitrogen species in the North At... more Data sets on horizontal and vertical distributions of sulfur and nitrogen species in the North Atlantic Ocean's atmosphere and their rates of deposition were compared with estimates produced by several climatological and event models for five case studies: (1) sulfate surface distributions and deposition, (2) nitrate surface distribution and deposition, (3) vertical and horizontal distributions of reactive nitrogen species (NOy), (4) spatial and temporal trends in DMS emissions, and (5) advections of sulfur and nitrogen into the North Atlantic Ocean's atmosphere. Highlights of the conclusions of the case studies were: (1) few data existed to resolve seasonal and latitudinal variations in DMS flux to the North Atlantic Ocean's atmosphere, (2) measured concentrations and model results of nitrate and nss-sulfate deposition appeared to agree well for some locations but poorly for some months at other locations, (3) current models generally predicted NOy concentrations that agreed with the measurements, and (4) estimates of the sulfur and nitrogen advection fluxes by even specific models agreed generally with estimates made by the synthesis of existing data.

Atmospheric Environment, 1986

The authors of tbis paper report measurements of dry deposition on a pine plantation using the fh... more The authors of tbis paper report measurements of dry deposition on a pine plantation using the fhnt gradient approach The relatively low SO1 concentrations at the experimental site and the use of an SOs analyxer with bigb temporaI rcsoIm.ion make this study potentirdly interesting Very few similar studii Iuive been pub&shed so far.