NSC projects May 2019 - April 2020

Multi-platform, multi-species ensemble data assimilation for the quantification and prediction of the chemical impacts of fires

Benjamin Gaubert, ACOM
Cheyenne allocation: 5 million core-hours

Fires caused by both human activities and natural processes have significant impacts on air quality, climate, ecosystem, and agriculture at both regional and global scales. The biomass burning (BB) emissions lead to a diverse mixture of trace gases and aerosol that includes short-lived and chemically reactive constituents that degrade air quality. In this project we will perform a series of data assimilation experiments using the atmospheric chemistry component (CAM-Chem) of the NCAR Community Earth System Model (CESM) and the NCAR Data Assimilation Research Testbed (DART).

CESM2 Large Ensemble

Gokhan Danabasoglu, CGD
Cheyenne allocation: 24.5 million core-hours

A team composed of researchers in the Climate and Global Dynamics (CGD) Laboratory at the National Center for Atmospheric Research (NCAR) proposes to conduct a set of large-ensemble (LE) simulations with the Community Earth System Model version 2 (CESM2). We propose a 40-member ensemble of historical and future climate change simulations, spanning the 1850-2100 period. A previous LE project using the CESM version1 (CESM1-LE, Kay et al. 2015) has proven to be one of the most used data sets produced by the CESM project with more than 570 citations and approximately 350,000 downloads from the Earth System Grid (ESG) since the publication of the data began in late 2013. Such a large number of ensemble members enables more rigorous studies of model uncertainty, the possibilities for future climate states, investigation into how extreme, or out of the ordinary, observed climate events of the past have been (i.e., determining when climate change has pushed an event beyond the range of natural variability), and a robust representation of the climate change signal. Due to the usefulness of these data sets, the CESM project would like to conduct another set of large ensemble simulations with the current CESM model version, CESM2. CESM2 has many updates compared to its predecessor, and it is the code base for most of the simulations that are being submitted to the Coupled Model Intercomparison Project phase 6 (CMIP6) by CESM.

Data assimilation for TNO simulation and prediction

Mausumi Dikpati, HAO
Cheyenne allocation: 6.2 million core-hours

We will investigate, using our recently developed TNO (Tachocline Nonlinear Oscillation) model, the following science questions:

  1. Right after the onset of a new solar cycle at a certain latitude-longitude, how do the solar activity bursts manifest at several longitude locations (called “active longitudes”)? Or, in other words, how does longitudinal wavenumber suddenly increase from m=1 to m=3 or 4? 
  2. What are the characteristics of TNOs during peak solar activity compared to that during onset? Or, in other words, can TNO properties evaluate the implication in space weather events?

Climate and air quality impacts including an interactive fire model for future climate scenarios with and without geoengineering, Part 2

Simone Tilmes, ACOM
Cheyenne allocation: 16.9 million core-hours

Changes in climate are expected to impact soil moisture and precipitation, and therefore the occurrence and strength of fires. Interactive fire emissions are included in the standard CMIP6 versions of CESM2(CAM6) and CESM2(WACCM6), but are currently not used for operational simulations. Recently performed CMIP6 coupled historical simulations including interactive fires show that the amount of biomass burning emissions between 1900 and 1950 is much larger than during later periods, which compare well to observations. Achieving a reasonable representation of fire emissions during the entire historical period is essential for reproducing realistic historical temperature trends and is required for running future climate simulations. The first part of this project will therefore focus on tuning the land model, and then performing coupled CESM2 CAM6 and WACCM6 simulations, in order to produce more reasonable fire emissions and to reproduce observed temperatures, chemistry, and aerosol distributions when compared with satellite and in-situ observations. The second part of the project will continue the work on future climate simulations with and without the application of stratospheric aerosol geoengineering.

At this point, no future simulations with interactive fires have been performed yet. With the availability of a newly tuned fire model and the interactive crop model, we will be the first to have the opportunity to explore the interactions between changes in fire emissions, air-quality, and agriculture in future scenarios with and without proposed solar geoengineering approaches. In addition, we will explore regional impacts of geoengineering based on these simulations for limited future periods, while employing the available regional refinement option over the Continental United States (CONUS). Our previous NSC proposal on the same topic was partially funded and has produced important test simulations, as well as future baseline simulations. The new allocations are expected to move this work significantly forward toward reaching the described science goals.

Subseasonal variability and climate sensitivity of tropical weather phenomena

Rosimar Rios-Berrios, SUNY at Albany
Cheyenne allocation: 9.4 million core-hours

High-impact and life-threatening weather events happen in the tropical atmosphere all year round. Many aspects of those events are not well understood, including (1) how multi-scale interactions between equatorial waves, midlatitude systems, and tropical disturbances influence the chances of tropical cyclogenesis, (2) which kinematic and thermodynamic structures favor extreme precipitation events in the moisture-rich tropical atmosphere, and (3) how tropical weather events may change in light of a warming climate. This project will tackle some aspects of those questions through a series of Earth-like aquaplanet simulations with the Model for Prediction Across Scales (MPAS). Three 128-day simulations are proposed using different sea-surface temperature profiles to examine subseasonal variability and climate sensitivity of tropical cyclones, equatorial waves, and extreme precipitation. Importantly, a novel configuration will be employed to resolve the convective nature of tropical weather while capturing planetary- and synoptic-scale phenomena. We expect that these first-of-its-kind simulations will allow us to gain a fundamental understanding of tropical weather phenomena across multiple spatiotemporal scales.

An ensemble reanalysis with the Data Assimilation Research Testbed and CAM6: A data set for making predictions, improving models, and understanding observations

Jeffrey Anderson, CISL
Cheyenne allocation: 17.1 million core-hours

An ensemble reanalysis using NCAR’s CAM6 global atmospheric model and the Data Assimilation Research Testbed will be produced for the period from mid-2010 to the end of 2019. This data set is the best estimate of the state of the atmosphere over that period and combines information from CAM6 forecasts with measurements of the atmosphere. The process of making the reanalysis requires comparing CAM6 forecasts to millions of measurements every day. This allows researchers to identify problems with the model and measurements so that both can be improved. An ensemble reanalysis provides a set of equally-likely atmospheric states (80 for this project) that allows researchers to include estimates of uncertainty for all results. The atmospheric reanalysis is needed as an input to produce similar reanalyses for land, ocean, and sea ice models so that these models can also be improved.