The Radiative‐Convective Equilibrium Model Intercomparison Project (RCEMIP) is an intercomparison of multiple types of numerical models configured in radiative‐convective equilibrium (RCE). RCE is an idealization of the tropical atmosphere that has long been used to study basic questions in climate science. Here, we employ RCE to investigate the role that clouds and convective activity play in determining cloud feedbacks, climate sensitivity, the state of convective aggregation, and the equilibrium climate. RCEMIP is unique among intercomparisons in its inclusion of a wide range of model types, including atmospheric general circulation models (GCMs), single column models (SCMs), cloud‐resolving models (CRMs), large eddy simulations (LES), and global cloud‐resolving models (GCRMs). The first results are presented from the RCEMIP ensemble of more than 30 models. While there are large differences across the RCEMIP ensemble in the representation of mean profiles of temperature, humidity, and cloudiness, in a majority of models anvil clouds rise, warm, and decrease in area coverage in response to an increase in sea surface temperature (SST). Nearly all models exhibit self‐aggregation in large domains and agree that self‐aggregation acts to dry and warm the troposphere, reduce high cloudiness, and increase cooling to space. The degree of self‐aggregation exhibits no clear tendency with warming. There is a wide range of climate sensitivities, but models with parameterized convection tend to have lower climate sensitivities than models with explicit convection. In models with parameterized convection, aggregated simulations have lower climate sensitivities than unaggregated simulations.

Prior studies of the linear response to asymmetric heating of a balanced vortex showed that the resulting intensity change could be very closely approximated by computing the purely symmetric response to the azimuthally averaged heating. The symmetric response to the purely asymmetric part of the heating was found to have a very small and most often negative impact on the intensity of the vortex. This result stands in contrast to many previous studies that used asymmetric vorticity perturbations, which suggested that purely asymmetric forcing could lead to vortex intensification.The issue is revisited with an improved model and some new methods of analysis. The model equations have been changed to be more consistent with the anelastic approximation, but valid for a radially varying reference state. Expressions for kinetic and available potential energies are presented for both asymmetric and symmetric motions, and these are used to quantify the flow of energy from localized, asymmetric heat sources to kinetic energy of the wind field of the symmetric vortex.Previous conclusions were based on simulations that used instantaneous temperature perturbations to represent rapid heat release in cumulus updrafts. Purely asymmetric heat sources that evolve over time and move with the local mean wind are shown to also cause vortex weakening. Weakening of the symmetric vortex is due to extraction of energy by the evolving asymmetries that undergo significant transient growth due to downgradient transport of momentum across the radial and vertical shears of the symmetric wind field. While much of this energy is returned during the axisymmetrization of the resulting potential vorticity anomalies, there is typically a net loss of energy for the symmetric vortex. Some variations on the rotation rate and duration of the heat sources can lead to intensification rather than weakening, as does a deeper (more barotropic) vertical structure of the symmetric vortex. However, it is reaffirmed that these asymmetrically forced changes are small compared to the response to the azimuthally averaged heating of an isolated heat source.Following the work of Hack and Schubert, the efficiency of the intensification process, defined as the ratio of injected heat energy to the kinetic energy change of the symmetric vortex, is computed for vortices of different sizes and strengths. In the limit of small perturbations, the efficiency does not depend on the temporal distribution of the heating. The efficiency is shown to increase with the intensity of the vortex and with the Coriolis parameter, with substantial efficiency increases for weak vortices. Potential applications of these results for predicting tropical cyclone formation and rapid development are discussed.

Background and Purpose-Several factors predict functional status after stroke, but most studies have included hospitalized patients with limited follow-up. We hypothesized that patients with ischemic stroke experience functional decline over 5 years independent of recurrent stroke and other risk factors. Methods-In the population-based Northern Manhattan Study, patients Ն40 years of age with incident ischemic stroke were prospectively followed using the Barthel Index at 6 months and annually to 5 years. Baseline stroke severity was categorized as mild (National Institutes of Health Stroke Scale Ͻ6), moderate (6 to 13), and severe (Ն14

Background and Purpose Diabetes increases stroke risk, but whether diabetes status immediately prior to stroke improves prediction, and whether duration is important, are less clear. We hypothesized that diabetes duration independently predicts ischemic stroke. Methods Among 3,298 stroke-free participants in the Northern Manhattan Study (NOMAS), baseline diabetes and age at diagnosis were determined. Incident diabetes was assessed annually (median=9 years). Cox proportional hazard models were used to estimate hazard ratios and 95% confidence intervals (HR, 95% CI) for incident ischemic stroke using baseline diabetes, diabetes as a time-dependent covariate, and duration of diabetes as a time-varying covariate; models were adjusted for demographic and cardiovascular risk factors. Results Mean age was 69±10 years (52% Hispanic, 21% white, and 24% black); 22% were diabetic at baseline and 10% developed diabetes. There were 244 ischemic strokes, and both baseline diabetes (HR 2.5, 95% CI 1.9-3.3) and diabetes considered as a time-dependent covariate (HR 2.4, 95% CI 1.8-3.2) were similarly associated with stroke risk. Duration of diabetes was associated with ischemic stroke (adjusted HR=1.03 per year with diabetes, 95% CI=1.02-1.04). Compared to non-diabetic participants, those with diabetes for 0-5 years (adjusted HR=1.7, 95% CI=1.1-2.7), 5-10 years (adjusted HR=1.8, 95% CI=1.1-3.0), and ≥10 years (adjusted HR=3.2, 95% CI=2.4-4.5) were at increased risk. Conclusion Duration of diabetes is independently associated with ischemic stroke risk adjusting for risk factors. The risk increases 3% each year, and triples with diabetes ≥10 years.