Monsoon Intra-seasonal Oscillations: Sensitivity and Improvement of Coupled Model Representations
Abstract
This project consists of an evaluation~using the Community Earth System Model (CESM), itsboundary layer mixing package (CVMix), and Large Eddy Simulations (LES)~of the degree towhich modeled Monsoon Intra-Seasonal Oscillations (MISO) in the Tropical Indian Ocean andBay of Bengal (BoB) depend on ocean boundary layer physics. These medium-timescale eventsare challenging to both climate models and weather forecasts, as they rely on both atmospheric andoceanic processes working in conjunction.The proposed approach uses the CESM to evaluate sensitivity and compare large-scale modelstatistics to large-scale routine observations, while comparisons between CVMix, LES, and processobservations from the Air-Sea Interactions in the Northern Indian Ocean Research Initiative(ASIRI) and Oceanic Control of Monsoon Intra-seasonal Oscillations in the Tropical IndianOcean and the Bay of Bengal Research Initiative (MISO-BoB). Thus, high-resolution simulationsand ASIRI and MISO-BoB data will ground the parameterization choices and development. It isexpected that through this process both the level of large-scale model sensitivity to physical parameterizationsand the optimal parameterization combinations can be identified for CESM behaviorin this region.The CESM already has parameterizations of boundary layer turbulence, added mixing due toLangmuir (wave-driven) turbulence, and mixed layer (submesoscale) eddy restratification. Someparameters in each of these parameterizations could be adjusted to improve simulations of MISO.More interestingly, there are phenomena that were observed in the ASIRI project, and undoubtedlyothers that will be observed during MISO-BoB, that have not yet been incorporated into a useableparameterization form. Gravity wave bores and shallow haloclines from runoff are two examplesthat suggest revisiting the present parameterizations. The former can be addressed through an extensionof the mixed layer eddy scheme, and the latter can be addressed by changing the new runoffand estuary parameterization. Our group will examine these data, and build or extend existing parameterizationsto approximate the effects of the novel phenomena. At the end of this process, anoverall CESM optimization to reproduce the MISO will optimize a combination of old and newparameterizations. Throughout, LES will be used evaluate consistency of new parameterizationsand observations.The CESM2 is already similar to other models through its use of the CVMix package. Thus,improvements to the CESM version of CVMix are rapidly shared among a group of models. Thefuture CESM3, which will be released during the course of this project, will be even more similarto the NOAA climate model and the NOAA CFS coupled forecast system, because CESM3 willshare the same ocean model code. Thus, improvements to the CESM ocean model that are notincluded in CVMix (e.g., mesoscale or submesoscale eddy parameterizations) will be immediatelyavailable to these NOAA models as well as CESM3.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712393
Entities
People
- Baylor Fox-Kemper
Organizations
- Brown University
- Office of Naval Research
- United States Navy