13 research outputs found
Machine-learned climate model corrections from a global storm-resolving model
Due to computational constraints, running global climate models (GCMs) for
many years requires a lower spatial grid resolution ( km) than is
optimal for accurately resolving important physical processes. Such processes
are approximated in GCMs via subgrid parameterizations, which contribute
significantly to the uncertainty in GCM predictions. One approach to improving
the accuracy of a coarse-grid global climate model is to add machine-learned
state-dependent corrections at each simulation timestep, such that the climate
model evolves more like a high-resolution global storm-resolving model (GSRM).
We train neural networks to learn the state-dependent temperature, humidity,
and radiative flux corrections needed to nudge a 200 km coarse-grid climate
model to the evolution of a 3~km fine-grid GSRM. When these corrective ML
models are coupled to a year-long coarse-grid climate simulation, the time-mean
spatial pattern errors are reduced by 6-25% for land surface temperature and
9-25% for land surface precipitation with respect to a no-ML baseline
simulation. The ML-corrected simulations develop other biases in climate and
circulation that differ from, but have comparable amplitude to, the baseline
simulation
Neural Network Parameterization of SubgridâScale Physics From a Realistic Geography Global StormâResolving Simulation
Abstract Parameterization of subgridâscale processes is a major source of uncertainty in global atmospheric model simulations. Global stormâresolving simulations use a finer grid (less than 5Â km) to reduce this uncertainty by explicitly resolving deep convection and details of orography. This study uses machine learning to replace the physical parameterizations of heating and moistening rates, but not wind tendencies, in a coarseâgrid (200Â km) global atmosphere model, using training data obtained by spatially coarseâgraining a 40âday realistic geography global stormâresolving simulation. The training targets are the threeâdimensional fields of effective heating and moistening rates, including the effect of gridâscale motions that are resolved but imperfectly simulated by the coarse model. A neural network is trained to predict the timeâdependent heating and moistening rates in each grid column using the coarseâgrained temperature, specific humidity, surface turbulent heat fluxes, cosine of solar zenith angle, landâsea mask and surface geopotential of that grid column as inputs. The coefficient of determination R2 for offline prediction ranges from 0.4 to 0.8 at most vertical levels and latitudes. Online, we achieve stable 35âday simulations, with metrics of skill such as the timeâmean pattern of nearâsurface temperature and precipitation comparable or slightly better than a baseline simulation with conventional physical parameterizations. However, the structure of tropical circulation and relative humidity in the upper troposphere are unrealistic. Overall, this study shows potential for the replacement of humanâdesigned parameterizations with dataâdriven ones in a realistic setting
MachineâLearned Climate Model Corrections From a Global StormâResolving Model: Performance Across the Annual Cycle
Abstract One approach to improving the accuracy of a coarseâgrid global climate model is to add machineâlearned (ML) stateâdependent corrections to the prognosed model tendencies, such that the climate model evolves more like a reference fineâgrid global stormâresolving model (GSRM). Our past work demonstrating this approach was trained with short (40âday) simulations of GFDL's XâSHiELD GSRM with 3Â km global horizontal grid spacing. Here, we extend this approach to span the full annual cycle by training and testing our ML using a new yearâlong GSRM simulation. Our corrective ML models are trained by learning the stateâdependent tendencies of temperature and humidity and surface radiative fluxes needed to nudge a closely related 200Â km grid coarse model, FV3GFS, to the GSRM evolution. Coarseâgrid simulations adding these learned ML corrections run stably for multiple years. Compared to a noâML baseline, the timeâmean spatial pattern errors with respect to the fineâgrid target are reduced by 6%â26% for land surface temperature and 9%â25% for land surface precipitation. The MLâcorrected simulations develop other biases in climate and circulation that differ from, but have comparable amplitude to, the noâML baseline simulation
Delayed Mortality and Attenuated Thrombocytopenia Associated with Severe Malaria in Urokinase- and Urokinase Receptor-Deficient Mice
We explored the role of urokinase and tissue-type plasminogen activators (uPA and tPA), as well as the uPA receptor (uPAR; CD87) in mouse severe malaria (SM), using genetically deficient (â/â) mice. The mortality resulting from Plasmodium berghei ANKA infection was delayed in uPA(â/â) and uPAR(â/â) mice but was similar to that of the wild type (+/+) in tPA(â/â) mice. Parasitemia levels were similar in uPA(â/â), uPAR(â/â), and +/+ mice. Production of tumor necrosis factor, as judged from the plasma level and the mRNA levels in brain and lung, was markedly increased by infection in both +/+ and uPAR(â/â) mice. Breakdown of the blood-brain barrier, as evidenced by the leakage of Evans Blue, was similar in +/+ and uPAR(â/â) mice. SM was associated with a profound thrombocytopenia, which was attenuated in uPA(â/â) and uPAR(â/â) mice. Administration of aprotinin, a plasmin antagonist, also delayed mortality and attenuated thrombocytopenia. Platelet trapping in cerebral venules or alveolar capillaries was evident in +/+ mice but absent in uPAR(â/â) mice. In contrast, macrophage sequestration in cerebral venules or alveolar capillaries was evident in both +/+ and uPAR(â/â) mice. Polymorphonuclear leukocyte sequestration in alveolar capillaries was similar in +/+ and uPAR(â/â) mice. These results demonstrate that the uPAR deficiency attenuates the severity of SM, probably by its important role in platelet kinetics and trapping. These results therefore suggest that platelet sequestration contributes to the pathogenesis of SM
NA62 electronics barracks access 2017
Access to the cavern was required during a break in the 2017 data taking. Pictures from 18-07-17, focusing on the electronics barracks and some safety equipment