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The relationship of trade-wind cumulus and its mesoscale organization to the larger-scale environment of the Northwest Tropical Atlantic (ATOMIC)

Principal Investigator(s): Paquita Zuidema (RSMAS)

Year Initially Funded: 2019

Program (s): Climate Variability & Predictability

Competition: Observing and Understanding Upper - Ocean Processes and Shallow Convection in the Tropical Atlantic Ocean

Award Number: NA19OAR4310379 | View Publications on Google Scholar


The trade-wind region is important to global climate because its governing large-scale circulation 1) evaporates water vapor off of the ocean surface that is then fed into the precipitating ITCZ, and 2) frequently exposes the low-altitude boundary layer clouds to space, allowing a mild cooling of the Earth’s climate through radiation over a large region. The low altitude cloud fraction can fluctuate dramatically despite minor synoptic variability, and organize into characteristic mesoscale patterns (e.g., popcorn cumuli, cloud streets, mesoscale arcs) that in part reflect the influence of precipitation. The cloud fraction and its relationship to these underlying processes is an important metric for models at a wide range of resolutions. The relationship to the free-troposphere mixing serves to motivate the EUREC4A project; the cloud fraction as a function of the cloud mesoscale organization is also still not well-known. These relationships are difficult to derive from modeling experiments, because of sensitivity to the microphysical and mixing parameterizations. This proposal seeks to improve our understanding of how the cloud fraction in the trade-wind regime relates to its organizing processes through involvement in and analysis of observations from ATOMIC: the Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign. As part of ATOMIC, three unique NOAA resources have been requested, namely the Research Vessel the Ronald H. Brown, along with the NOAA P-3 and G-4 planes. Zuidema will deploy several instruments providing cloud, precipitation, and air/sea temperatures upon the R/V Brown, namely a W-band Doppler zenith-pointing radar, a microwave radiometer, disdrometers, and a hyperspectral MAERI for SST, analyze these measurements and integrate them with other ship-board measurements, including aerosols. GOES-16 satellite data will be collected and analyzed for cloud mesoscale organization, with the analysis from other years providing context for the ATOMIC time period. Dropsonde and radar measurements from the research aircraft will provide spatial context for the ship-board measurements, and flight paths will also be designed to optimize opportunities for Lagrangian sampling. This includes developing daily forecast air mass trajectories based on the positions of the NOAA/EUREC4A research platforms. Aircraft microphysical measurements will aid assessments of aerosol-cloud interactions. The analysis will build on and contribute to collaborations with C. Fairall (NOAA ESRL) on deployment planning and data analysis, G. Feingold (NOAA ESRL) on integrating observations into modeling efforts, S. de Szoeke (OSU) on the radiosonde analysis and boundary layer energetics, E. Thompson/J. Thomson (UW APL) and C. Clayson (WHOI) on ocean-air interactions and connecting atmospheric behavior to ocean mesoscale variations, and T. Quinn (NOAA PMEL) on aerosol-cloud interactions. Collaboration with EUREC4A scientists is expected, including on developing a ‘best-estimate’ of large-scale forcing. Broader Impacts and Relevance to CVP program: The curated, analyzed data will form a long-term legacy dataset that will serve as a basis for subsequent process model studies and large-scale model evaluation. This research will enhance process-level understanding of the ocean-atmosphere interactions and atmospheric boundary layer processes governing the expansive trade-wind region. This region remains poorly modeled within climate models, to a large degree because the low clouds and their link to the troposphere have not been as comprehensively observed as will occur through the EUREC4A/ATOMIC programs.

Understanding the role of mesoscale organization in air-sea interactions

Principal Investigator(s): Julianna Dias (CU-CIRES / NOAA/ESRL/PSD); Robert Pincus (CU-CIRES / NOAA/ESRL/PSD ); Charlotte DeMott (Colorado State University), collaborator: Stefan Tulich (CIRES/CU and NOAA/ESRL/PSD)

Year Initially Funded: 2019

Program (s): Climate Variability & Predictability

Competition: Observing and Understanding Upper - Ocean Processes and Shallow Convection in the Tropical Atlantic Ocean

Award Number: NA20OAR4310374, GC20-398 | View Publications on Google Scholar


The population of clouds over the subtropical oceans is dominated by trade wind cumulus which often organize in a variety of mesoscale shapes and sizes. The subtropical ocean, too, exhibits much fine-scale variability, in the form of sea surface temperature (SST) anomalies and ocean mesoscale eddies. Because observed patches of aggregated shallow cumulus, SST variations, ocean eddies, and associated mesoscale circulations exist in the “grey zone” for current global models, our ability to model these phenomena and understand their relevance to the climate system is crude. Here we propose a process modeling study to investigate the role of mesoscale spatial organization in air-sea interactions. Our main objectives are: (i) to assess how mesoscale spatial organization of shallow cumulus may affect atmosphere-ocean coupling by modulating wind speeds and cloudiness, and (ii) to investigate how mesoscale organization of shallow clouds and the circulations in which they are embedded are affected by transient SST perturbations driven by surface fluxes and persistent SST structures maintained by oceanic mesoscale eddies. We will address these questions with large eddy simulations (LES) with resolutions fine enough to resolve cloud-scale circulations but large enough to admit the organizing mesoscale circulations. We will diagnose how mesoscale organization affects the net surface energy budget and how SST perturbations in turn affect mesoscale organization. By using LES to interpolate the data from ATOMIC/EUREC4A-OA, our primary focus is to examine how mesoscale structures in the lower atmosphere and the upper ocean might interact and regulate air-sea coupling. This goal is directly aligned with this CVP target competition aim of better understanding air-sea interactions within the ATOMIC/EUREC4A-OA field campaigns region, with focus on lower atmospheric boundary layer processes and their influence on the ocean. This knowledge will then be used to inform physical parametrizations, and ultimately, to improve climate predictions. Therefore, the proposal also contributes to NOAA’s goal of providing high quality environmental information.

Upper-ocean salinity variability in the northwestern tropical Atlantic and its interactions with SST and winds

Principal Investigator(s): Gregory Foltz (NOAA/AOML), Denis Volkov (NOAA/AOML); Christophersen (NOAA/AOML) Collaborators: Rick Lumpkin (NOAA/AOML), Renellys Perez (NOAA/AOML), Shenfu Dong (NOAA/AOML), Gustavo Goni (NOAA/AOML)

Year Initially Funded: 2019

Program (s): Climate Variability & Predictability

Competition: Observing and Understanding Upper - Ocean Processes and Shallow Convection in the Tropical Atlantic Ocean

Award Number: GC19-304 | View Publications on Google Scholar


Two important topics in need of further research are (1) the impact of upper-ocean salinity on stratification, mixing, and sea surface temperature (SST), and (2) interactions between ocean mesoscale eddies and the atmosphere. The northwestern tropical Atlantic (NTA) is an advantageous place to address these questions because it experiences strong eddy activity and pronounced surface freshening from Amazon River outflow. Furthermore, during boreal winter, shallow cumulus clouds are prevalent in the NTA and are affected by the underlying SST. The details of how these clouds form and interact with the ocean are not well known, contributing to significant uncertainty in climate models’ radiation budgets. Previous research has shown that, on average, six large anticyclonic rings translate northward in the NTA each year after separating from the North Brazil Current (NBC) retroflection. Though the volume transport associated with the rings has been quantified, the upper-ocean temperature and salinity structures are not well known. It is also unclear how the rings affect near-surface winds and heat fluxes. It has been established that salinity contributes significantly to upper-ocean stratification in the NTA during boreal winter, but there is debate on the impact of salinity on SST in this region. The uncertainties are compounded by strong mesoscale salinity variability from NBC rings. These gaps in knowledge limit our understanding of ocean-atmosphere coupling and cloud variability in the NTA. This proposal aims to improve our understanding of eddy variability and ocean atmosphere interactions in the NTA through the deployment of a set of unique surface drifting buoys, combined with analysis of historical in situ and satellite data and one-dimensional ocean model experiments. The drifting buoys will provide new and valuable information on the temperature and salinity structure in the upper 10 m of the ocean, including the diurnal cycle and the conditions within and outside of rings and eddies. Wind velocity measurements from the drifters will be used to diagnose changes in upper-ocean temperature and salinity structure and potential eddy-atmosphere coupling. Ocean model experiments will provide deeper process oriented insight into the impacts of salinity, winds, and surface heat fluxes on upper-ocean mixing and SST. The proposed work is directly related to Competition 2 of NOAA/CPO’s CVP announcement, which seeks studies focused on observing, understanding, and/or process modeling of upper ocean processes and air-sea interactions in the Northwest Tropical Atlantic as part of the ATOMIC/EUREC4A-OA field campaigns. The proposed measurements and analysis will also advance our understanding of upper ocean processes (diurnal cycle and evolution of upper-ocean temperature and salinity structure), ocean boundary layers, and mesoscale ocean eddies, which is a specific goal of the proposal call. More broadly, our proposed work aligns well with the mission of the CVP program, which is to support research that enhances our process level understanding of the climate system through observation, modeling, analysis, and field studies.

Understanding the role of the diurnal cycle and the mean state on the propagation of the intraseasonal variability over the Maritime Continent

Principal Investigator(s): Daehyun Kim (University of Washington); Eric Maloney (Colorado State University), Chidong Zhang (NOAA/PMEL), Arif Munandar (BMKG)

Year Initially Funded: 2018

Program (s): Climate Variability & Predictability

Competition: Observing and Understanding Processes Affecting the Propagation of Intraseasonal Oscillations in the Maritime Continent Region

Award Number: NA18OAR4310300, NA18OAR4310299 | View Publications on Google Scholar


The Madden-Julian oscillation (MJO) and the boreal summer intraseasonal oscillation (BSISO) are the dominant modes of tropical intraseasonal variability (ISV), providing a primary source of predictability on intraseasonal timescales. Many global climate models (GCMs) suffer from poor representations of the MJO and BSISO, especially their propagation over the Maritime Continent (MC). The role of the strong MC diurnal cycle on the propagation of the ISV has remained poorly understood due the lack of in-situ observations. The Years of Maritime Continent (YMC) and Propagation of Intra-Seasonal Tropical Oscillations (PISTON) field campaigns will collect in-situ observations of the diurnal variation of the atmospheric state, among many other things, which will provide a unique opportunity to enhance our understanding of the interactions among the diurnal cycle, the mean state, and the propagation of ISV over the MC. The proposed work is organized around the following two hypotheses: 1) The diurnal cycle of convection in the MC islands and over the adjacent water destructively interferes with convection of the MJO and BSISO, weakening their intraseasonal convective envelopes, and disrupting their MJO/BSISO; and 2) The diurnal cycle over the MC plays a key role in determining/shaping the seasonal mean basic state. Biases in the MC diurnal cycle in GCMs deteriorate the basic state, which in turn prevents the model from simulating a realistic propagation of intraseasonal variability over the broader MC area. To test these hypotheses, the proposed research aims to use YMC and PISTON field campaign observations together with global and regional models to enhance our understanding of the role of the MC on the propagation of the MJO and BSISO. High resolution cloud system resolving simulations with a regional climate model will be conducted targeting observed ISV events. A series of long uncoupled and coupled simulations will be made with a GCM that exhibits superior skill in simulating the ISV. The YMC and PISTON observations together with the satellite observations will be used to evaluate the MC diurnal cycle in the model simulations. The model simulations will be repeated with the MC diurnal cycle suppressed to examine the direct and indirect effect of the MC diurnal cycle on ISV propagation. Short-term hindcast experiments will be conducted with the GCM after the YMC and PISTON field campaigns to examine the role of the diurnal cycle on ISV propagation in the context of events that occurred during the field campaigns. Lastly, the NCEP operational model hindcast dataset will be analyzed, to understand the relationship among the biases in the diurnal cycle, the mean state, and the ISV propagation. Relevance to the competition and NOAA’s long-term climate goal: The proposed research strongly addresses the objective of the competition: “CVP - Observing and Understanding Processes Affecting the Propagation of Intraseasonal Oscillations in the Maritime Continent Region” as it focuses on the propagation of the tropical ISV through the MC using a combination of in situ and remote observations, modeling, and data analysis. The expected outcome of the proposed research will advance understanding of MJO dynamics and will provide key information for improving ISV prediction. By contributing to advancing our ability to predict the tropical ISV, which affects high-impact weather events over the US, our proposed project is also relevant to NOAA’s long-term climate goal of “providing the essential and highest quality environmental information vital to our Nation’s safety, prosperity and resilience.”

Upscale Feedback of Higher-Frequency Modes to MJO over Maritime Continent

Principal Investigator(s): Tim Li (University of HI); Ming Zhao (NOAA GFDL); Tomoe Nasuno (JAMSTEC)

Year Initially Funded: 2018

Program (s): Climate Variability & Predictability

Competition: Observing and Understanding Processes Affecting the Propagation of Intraseasonal Oscillations in the Maritime Continent Region

Award Number: NA18OAR4310298 | View Publications on Google Scholar


This proposal articulates an endeavor in responding to NOAA CPO Competition 4: Climate Variability and Predictability Program (CVP) - Observing and Understanding Processes Affecting the Propagation of Intraseasonal Oscillations in Maritime Continent Regions. MJO is the most important sub-seasonal variability that bridges weather and climate scales. Current models, however, have difficulty to simulates its evolution and in particular its interaction with higher-frequency (HF) motions. This proposal consists of three major research thrusts to advance our current understanding of MJO multi-scale interaction. The first thrust is to investigate the impact of MJO on HF modes including diurnal cycles, synoptic perturbations, and convectively coupled equatorial waves such as Kelvin waves, westward-moving inertia-gravity waves, Rossby waves and mixed Rossby-gravity waves. The structure and evolution characteristics of the HF modes at various phases of MJO near the Maritime Continent will be examined. In addition to the observational data analysis, we will conduct sensitivity numerical model experiments to understand mechanisms through which MJO modulate the HF modes. The second thrust is to reveal the role of upscale feedback of the HF modes in modulating MJO intensity, structure and propagation. Various diagnostic tools developed by the PI will be used. These diagnoses are from different dynamic and thermodynamic perspectives, including eddy momentum transport, barotropic energy conversion, nonlinear rectification of diabatic heating and surface latent heat flux, and eddy kinetic energy and moist static energy budgets. The upscale feedback of selected HF modes such as dry Rossby waves from tropical central Pacific will be examined through idealized numerical experiments. The third research thrust is to examine the two-way interactions in 27 start-of-art general circulation models (GCMs) that participated in MJO Task Force (MJOTF) and GEWEX Atmospheric System Study (GASS) multi-model intercomparison project. Column integrated moist static energy (MSE) budget will be investigated to unveil the fundamental processes that control propagating and non-propagating MJOs across the Maritime Continent. A special attention will be paid to the HF mode – MJO interaction and the MJO – mean flow interaction in modulating anomalous vertical and horizontal MSE advection terms. We will also examine how the MJO-HF mode interactions depend on model physics, air-sea coupling, mean state bias, and ENSO. Merit and impact: The proposed project, once successfully completed, would not only advance our current understanding of MJO dynamics but also help identify key problems in the current state-of-the-art GCMs. This in turn may provide guidance to improve global model representations of MJO and its interactions with extreme weather events, and to help advance NOAA long-term goal to provide reliable, trusted, transparent, and timely weather/climate information needed to sustain all sectors of our economy and environment.

A Pre-Field Modeling Study of Scales, Variability and Processes in the Near Surface Eastern Equatorial Pacific Ocean in Support of TPOS

Principal Investigator(s): Frank Bryan (NCAR), LuAnne Thompson (Univ. of Washington), William Kessler (NOAA/PMEL)

Year Initially Funded: 2018

Program (s): Climate Variability & Predictability

Competition: Pre-Field Modeling Studies in Support of TPOS Process Studies, a Component of TPOS 2020

Award Number: NA18OAR4310399, NA18OAR4310400, GC18-908 | View Publications on Google Scholar


We propose a re-examination of the design of a Pacific Upwelling and Mixing Physics (PUMP) process study in light of available observing technologies, by characterizing the space and time scales and dynamics of upwelling and the process-level connection to mixing. We will develop analysis frameworks around testable hypotheses, and determine the sampling requirements for an efficient and robust observational implementation. We will address this objective by exploiting a combination of output from high-resolution ocean and climate model simulations, and existing long-term observations. To frame our investigation of observing strategies for PUMP, we will address the following scientific questions: 1. What are the dynamics controlling divergence and upwelling? 2. How is upwelling partitioned into adiabatic and diabatic motions? 3. How do the three dimensional meridional circulation cells and their role in the heat budget respond to changes in surface forcing across a range of time scales from synoptic to inter-annual and in different locations within the tropical Pacific? The proposed effort directly responds to the guiding questions in the solicitation by addressing the following experimental design considerations: What zonal and meridional resolution is needed to adequately measure divergence of mass and the exchange of mass and heat between the thermocline and surface ocean? How long of a deployment of initial observations is needed to adequately represent the statistics of the important processes at play? What regions (e.g. 140ï‚°W or 110ï‚°W) of the eastern tropical Pacific should be most intensively measured? What locations would be most representative of the broader context of the eastern Pacific? Are there locations where available observing technologies are better suited to sample the natural scales of the problem? How far north and south of the equator should the observations extend to capture the key dynamics of the meridional cells? What sustained observations are needed to monitor the state of the vertical exchange in the eastern equatorial Pacific? A concurrent assessment of the model solutions against currently available long-term observations and select historical process studies will provide an up-to-date understanding of model biases and elucidate the limitations of our recommendations for observing system design. We view the proposed effort as the beginning of an iterative and sustained integration of talents, experience and resources to advance our ability to observe and simulate the tropical Pacific and its impacts on the global climate system, thereby directly aligning with the overall goals of NOAA CVP.

Assessing the observational requirements to capture and quantify key ocean processes in the tropical Pacific through focused modeling studies

Principal Investigator(s): Kelvin Richards, Hariharasubramanian Annamalai (University of Hawai'i)

Year Initially Funded: 2018

Program (s): Climate Variability & Predictability

Competition: Pre-Field Modeling Studies in Support of TPOS Process Studies, a Component of TPOS 2020

Award Number: NA18OAR4310404 | View Publications on Google Scholar


The Tropical Pacific Observing System 2020 (TPOS 2020) effort has at its core the goal to enhance and redesign observations of the tropical Pacific. As part of the design strategy a number of process studies have been identified that will help in the design of the TPOS Backbone, which will monitor the state of the Pacific system, as well as aid understanding and model improvement related to sub-seasonal to interannual variability of the system and its prediction (e.g. MJO, ENSO). The two process studies given highest priority are "Air-sea interaction at the eastern edge of the warm pool" and "Pacific Upwelling and Mixing Physics (PUMP)". This proposal is directed towards providing modeling support in the pre-field phase of both of these studies. The use of models to assess observational strategies requires the model to capture the relevant processes. A major focus of our studies will be the effect of vertical resolution on observational estimates and model physics, an often overlooked aspect in studies. We have demonstrated the need for high vertical resolution in both observations and models to capture important physics in the tropics, in not only the surface layer but throughout the thermocline. Our approach is to utilize an existing model setup that allows downscaling through a series of nested grids. The model is demonstrated to have a high fidelity in capturing a number of important aspects of the tropical Pacific. Our modeling strategy will provide insights into the role of upper-ocean stratification and fine-scale shear in impacting the SST. SST is an important property in the tropical Pacific. It influences the life-cycle of the MJO and ENSO. Its amplitude and spatial distribution impacts various interactive processes determining precipitation and atmospheric diabatic heating on sub-seasonal to seasonal (S2S), and interannual timescales. We will apply the model system to both the eastern edge of the western warm pool and the eastern upwelling region (PUMP). Model experiments will be used to address a number of the guiding questions of the TPOS process studies that include: what aspects need to be observed, what sampling strategies best provide quantitative estimates of processes, how representative are the time and space restricted studies, and how best to provide guidance on improving models. The model runs and analysis are designed to help in the assessment of the design of the observational component of the process studies. We propose a number of assessments using the model, but note that specific assessment studies will be done in strong collaboration with observational and other modeling groups.

Improved Understanding of air-sea interaction processes and biases in the Tropical Western Pacific using observation sensitivity experiments and global forecast models

Principal Investigator(s): Aneesh Subramanian (CU Boulder/Formerly Scripps); Co-PIs: Matthew Mazloff (Scripps), Kris Karnauskas (CU Boulder), Charlotte DeMott (Colorado State University)

Year Initially Funded: 2018

Program (s): Climate Variability & Predictability

Competition: Pre-Field Modeling Studies in Support of TPOS Process Studies, a Component of TPOS 2020

Award Number: NA18OAR4310405, NA18OAR4310406, NA18OAR4310407 | View Publications on Google Scholar


We propose to determine physical mechanisms governing air-sea interactions in the tropical west Pacific at the eastern edge of the warm pool by isolating coupled feedback processes through analyses of short-term coupled and uncoupled forecasts. Climate model forecasts of the Madden–Julian Oscillation (MJO) and El Niño–Southern Oscillation (ENSO) experience a systematic climate drift resulting in biases of the modeled tropical western Pacific climatology. Global models tend to have an excess rainfall in the warm pool region and a deficiency in rainfall at the eastern edge of the warm pool. We propose to increase understanding of the dynamics and thermodynamics in the region by utilizing the Community Earth System Model (CESM) global runs as well as high-resolution Massachusetts Institute of Technology general circulation model (MITgcm) regional uncoupled simulations. Studying coupled vs uncoupled forecasts initialized with different ocean reanalysis products reveals the impact of ocean data assimilation on forecast error growth in the Tropical West Pacific region. The European Centre for Medium-Range Weather Forecasts (ECMWF) has recently completed several observation sensitivity experiments (OSE) ocean analyses by individually assimilating different ocean observation platforms (Argo, moorings, satellite, and others) into ocean analyses state estimates. Initializing our coupled forecasts from these OSE experiments will show the impact of different ocean observations on forecasts in the Tropical Pacific region. The PI (Subramanian) collaborates closely with Dr. Magdalena Balmaseda (ECMWF) who has given permission to use these OSE solutions. The proposed work will inform the role of forecast sensitivity to ocean state and air-sea feedbacks in the warm pool eastern edge region. Also the experiments with different ocean initializations will show the impact of various ocean observation platforms in constraining regional biases. The proposed analyses will help prioritize process study field campaigns and ocean observation platforms to best constrain modeling and parameterization development efforts. Analyzing air-sea interactions and the oceanic mixed layer heat and salt budgets in the model forecasts and in the reanalyses fields will reveal discrepancies in components of the budgets. This budget and flux analysis will yield a process-based understanding of the regional mixed layer, barrier layer, and MJO dynamics, feedbacks, and sensitivities. This research will identify the physical processes that lead to the mean and intraseasonal variability biases in the Tropical West Pacific and, more specifically, the key biases controlling MJO and ENSO background states. This understanding prioritizes process studies and observational field campaigns in the region as a part of TPOS 2020 on which processes to prioritize for observations. The work will also inform parameterization improvements for use in CESM for real-time forecasts of the climate-scale processes in the tropical Pacific.

Multi-timescale near-surface salinity variability at the eastern edge of the warm pool: A Modeling and an OSSE study in support of TPOS 2020

Principal Investigator(s): Arun Kumar (NOAA/NCEP), Avichal Mehra (NOAA/NCEP), Meghan Cronin (NOAA/PMEL); Collaborators: Jieshun Zhu (UMD), Dongxiao Zhang (NOAA/PMEL)

Year Initially Funded: 2018

Program (s): Climate Variability & Predictability

Competition: Pre-Field Modeling Studies in Support of TPOS Process Studies, a Component of TPOS 2020

Award Number: GC18-907 | View Publications on Google Scholar


As part of the Tropical Pacific Observing System 2020 (TPOS 2020) first report, several process studies were identified that would guide development of the observing system and lead to improved understanding and predictability of the Pacific climate system. Here we focus on prefield phase needs of the process study “Air-sea interaction at the eastern edge of the western Pacific warm pool (WPWP)”. This study builds upon previous studies in the WPWP (e.g., TOGA COARE) by focusing on the interactions at the front at the eastern edge of the WPWP. Towards the implementation of the process study to understand air-sea interaction at the eastern edge of the WPWP, this proposal is primarily a model-based study to provide some necessary insights for the design of the field phase of the experiment. Our objectives are to (a) explore the multi-timescale near-surface salinity variations at the Warm Pool eastern edge (WPEE), and (b) To identify possible sampling requirements (and strategies) that may be essential to capture this variability. To achieve the objectives, the following tasks are proposed: 1) A coupled simulation using the modified Coupled Forecast System version 2 (CFSv2) with 1-m vertical resolution in the upper ocean will be conducted. Diagnostics related to the sea surface salinity (SSS) front at the WPEE and multi-timescale SSS variability will be made to enhance our understanding of air-sea interaction in the presence of barrier layer over this region; 2) Mimicking a realistic combination of sampling variables, sampling locations/frequencies and sampling technologies that may be viable for observing the variability associated WPEE, a set of “synthetic observations” will be constructed based on the above coupled model simulation; and 3) Observing system simulation experiments (OSSEs) will be performed by assimilating the “synthetic observations” into an ocean data assimilation to obtain an ocean analysis. Comparisons with the original coupled simulation will be made to ascertain if the proposed observational strategies will be adequate to capture essential features of WPEE. We anticipate that the proposed research will enhance our understanding of processes associated with multi-timescale near-surface salinity at the warm pool eastern edge and identify possible sampling requirements (and strategies) essential to capture them. The outcomes from the project will not only improve our understanding of air-sea interaction at the eastern edge of the warm pool, but will also help guide the pre-cruise planning and field campaign development for TPOS 2020, and further, in the design of the sustained observing system.

Simulations and analysis of mesoscale to turbulence scale process models to facilitate observational process deployments in the Equatorial Pacific Cold Tongue

Principal Investigator(s): Daniel Whitt (NCAR), Scott Bachman (NCAR), Ren-Chieh Lien (University of Washington); Co-Investigators: Ryan Holmes (The University of New South Wales), William Large (NCAR)

Year Initially Funded: 2018

Program (s): Climate Variability & Predictability

Competition: Pre-Field Modeling Studies in Support of TPOS Process Studies, a Component of TPOS 2020

Award Number: NA18OAR4310408, NA18OAR4310409 | View Publications on Google Scholar


Due to the far-reaching societal impacts, developing models and observing systems that enable reliable forecasts of the tropical Pacific Ocean in general and the Equatorial Cold Tongue (ECT) in particular are a high priority. However, global numerical models used for this purpose have significant deficiencies. Several of these deficiencies may result from poorly-constrained parameterizations in the ocean model and/or coarse grid resolution (usually 10-100 km in the horizontal and 10 m in the vertical). For example, upwelling and vertical mixing are two processes that are crucial components of the heat budget of the ECT, but these processes have traditionally been difficult to observe and depend significantly on physics that occurs at scales much smaller than a typical model grid cell. In addition, previous studies have demonstrated that these processes are sensitive to model resolution and parameterization scheme. This proposal is to support a team of modelers and observationalists in conducting process-oriented numerical experiments designed to reveal how small-scale (< 500 km, subannual) processes contribute to upwelling, mixing and thereby the heat budget of the ECT. The ECT is a “pacemaker” of global climate, and therefore obtaining improved forecasts and observations of the ECT is a high priority for NOAA. The proposed work contributes to this broader objective, and more specifically aids the scientific community and the broader public by addressing the goals of this competition: ● New state-of-the-art high-resolution simulations of the ECT will be shared with the scientific community, which will facilitate scientific discovery via future analysis. ● By quantifying the contribution of different small-scale processes in the models to upwelling and vertical heat fluxes, the proposed work will clarify the benefits associated with observing various processes and scales, so that observational process studies can focus on the spatial and temporal scales and processes that are most important. ● By identifying aspects of regional model solutions of the ECT that are most biased in their representation of vertical mixing and accompanying heat fluxes, the results of the proposed work will be used to help design a sampling plan for observational process studies that will constrain later parameterization and model development efforts and more efficiently improve model solutions and forecasts. ● By conducting observing system simulation experiments, the proposed effort will identify optimal observational tools for future process studies. ● By supporting the career development of early career scientists (Whitt, Bachman, and a to-be-named postdoc), the proposal supports the development of a globally-competitive STEM workforce.



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