Understanding the Carbon and Water Budget at the Regional Scale
Using State-of-the-Art Observations, Satellites, and Numerical Models:
The Neuse River Basin Case Study
Over the past five years, we have expanded the well-known Regional Atmospheric Modeling System (RAMS) into a state-of-the-art Earth System Model (ESM). Unlike the current generation of global climate models (GCMs), OLAM solves a finite-volume analog of the full compressible Navier-Stokes equations in conservation form. Its grid configuration enables local mesh refinement to any degree without the need for special grid nesting algorithms. This capability is particularly advantageous for studying multiscale complex interactions between local, regional and global climate processes and to better understand the implications of local and/or regional change on the global climate and vice versa. While the dynamical core of OLAM is completely new, its physics are borrowed from RAMS, thus enjoying reliable and robust parameterizations, including land-surface processes, clouds, radiation and turbulence. Both RAMS and OLAM are coupled with ED2, the second generation of the Ecosystem Demography model. Modern satellites provide crucial initialization data for the coupled model.
Simultaneously with this modeling effort, we have developed the Helicopter Observation Platform (HOP), a new aircraft facility that can be used for in situ and remote measurements at very low altitude and very slow speed. The HOP is currently equipped with sensors for measuring fluxes of carbon dioxide, moisture and sensible heat at a resolution never achieved before by other research aircraft (see video clip at www.hop.cee.duke.edu).
The specific goal of the project proposed here is to better understand the exchange rate of water and carbon between the ground surface and the atmosphere at multiple temporal and spatial scales. This rate seems to be affected by multiple ecological factors and hydrological and atmospheric processes that remain to be elucidated. The ultimate goal of this project is to improve the parameterization of land-atmosphere interactions in OLAM, so that more accurate scenarios of carbon and water exchanges between the ground and the atmosphere can be made at the local, regional and global scales. This has a considerable impact on our capability to simulate (and, therefore, understand and predict) global change and should be a key issue to be investigated at the Center for Global Change.
For this purpose, we will first use in synergy HOP and ground-based measurements, regional and global reanalyses, and satellite observations, to evaluate our capability to simulate with OLAM/ED2 the balance of CO2, moisture and heat at the "basic" climate (modeling) scale (i.e., the smallest domain likely to be represented in a single grid element of a typical regional climate model and/or a next-generation global climate model, namely about 30 x 30 km), up to the basin scale. We assert that unless a fully coupled model can represent correctly these balances at this "basic" scale, it is unlikely that regional and/or global budgets will be obtained accurately. We also claim that such a task was not possible before HOP and OLAM/ED2 were developed and that the time is now ripe for achieving this new scientific milestone. We then intend to use the validated model to quantify the net CO2 and water balance of ecosystems and exchanges with the atmosphere at multi-scales, including their spatial and temporal variation with respect to vegetation type, phenology, changes in land use, management and disturbance history.
The working group is composed of:
Roni Avissar, Civil and Environmental Engineering, Duke University
Ram Oren, Environmental Sciences and Policy, Duke University
Amilcare Porporato, Civil and Environmental Engineering, Duke University
Gabriel Katul, Environmental Sciences and Policy, Duke University
Rob Jackson, Environmental Sciences and Policy, Duke University
