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Sort by: Title | Principal Investigator | Program | Year Initially Funded

Interaction of the Lower Atmosphere and Upper Ocean

Principal Investigator (s) James C. McWilliams (UCLA); Peter P. Sullivan (NCAR), Lionel Renault (UCLA)

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: NA19OAR4310377, NA19OAR4310378 | View Publications on Google Scholar

Abstract: The proposed research is a joint project between UCLA and NCAR. The research is for process modeling of fine-scale circulations in the lower atmosphere and upper ocean in the northwest Tropical Atlantic as part of the U.S. Atlantic Trade-wind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) and the European EUERC4A-OA Projects. It is in response to NOAA's Climate Variability and Predictability (CVP) Program: Competition 2: CVP-Observing and Understanding Upper-Ocean Processes and Shallow Convection in the Tropical Atlantic Ocean. The guiding hypothesis of the research is that surface heterogeneities in oceanic temperature (SST) and currents induce heterogeneities in the air-sea fluxes of heat, moisture, and momentum, which in turn modulate the mesoscale and submesoscale circulations in the oceanic surface layer and atmospheric boundary layer. The source of the heterogeneity is oceanic mesoscale eddies and submesoscale fronts. We will use two modeling approaches to elucidate the interaction between the lower atmosphere and the upper ocean: idealized flow configurations in a Large Eddy Simulations (LESs) that resolve the boundary-layer turbulence (led by NCAR) and “realistic” down-scaled coupled simulations using the Weather Research and Forecast (WRF) and the Regional Oceanic Modeling System (ROMS) with parameterized vertical fluxes due to boundary-layer turbulence (led by UCLA). The phenomena arising in these separate, different-scale simulations will be used to inform each other to develop, by bootstrapping, a better process understanding across the interacting range of scales from boundary-layer turbulence to the mesoscale winds and currents. We will design a sequence of studies that explore, in the context of Tropical Atlantic phenomena, how submeoscacle currents interact with the boundary layer turbulence in the ocean, how surface gradients in SST and currents interact with the boundary layer turbulence in the atmosphere, how the resulting secondary circulations extend vertically through the upper ocean and lower atmosphere, and how the Thermal and Current Feedbacks develop mesoscale and submesoscale correlations across the air-sea interface, even reaching into the shallow cloud layer above. The key methodologies are the massively parallel LES code developed over many years at NCAR, including surface wave dynamical influences in both the air and water, and the ROMS circulation model developed at UCLA that also includes surface wave interactions and allows multiple levels of grid nesting conveying larger scale influences down to finer scale circulations, in particular allowing very high resolution studies of submesoscale phenomena shaped by the encompassing mesoscale eddies and regional currents. Because of the extensive international field measurements planned, we would work closely with the observing groups, especially those that have fine-scale sampling in both time and at least one horizontal coordinate. The intent is to combine the relatively more complete information from model simulations with the measured reality, for the better interpretation of both, and to establish the importance of surface heterogeneity in climate outcomes. To this end we intend to work closely with both the European and American experimental teams. This research enhances our process-level understanding of the climate system through observation, modeling, analysis, and field studies. This vital knowledge is needed to improve climate models and predictions so that scientists and society can better anticipate the impacts of future climate variability and change.

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

Principal Investigator (s) Christopher Fairall (NOAA/ESRL/PSD); Gijs de Boer (CU-CIRES); Alan Brewer (NOAA/ESRL/CSD); Partner: Phillip Hall (NOAA/UAS)

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: GC19-302 | View Publications on Google Scholar

Abstract: Above most of the oceans, liquid clouds of a few thousand meters or less drive mixing in a process called shallow convection in the atmospheric boundary layer (ABL). The warm clouds dominate the ocean’s area coverage and may strongly influence weather on seasonal to sub-seasonal time scales. Shallow convection exerts an important influence on sea surface temperatures (SSTs) and salinity by moderating the air-sea exchanges of energy and moisture and represent a ‘major source of uncertainty in projections of future climate’. The interaction between shallow convection and the ocean’s surface layers is a two-way street: though shallow convection influences SSTs, shallow convection is itself controlled to a large extent by SST and air-sea fluxes, which are mediated by processes within the ocean, especially Oceanic Barrier Layers (OBL) and mesoscale ocean eddies. OBL are near-surface layers created by low salinity waters and embedded in the ocean mixed layer. OBLs tend to decouple the ocean mixed layer from surface momentum fluxes, which facilitates subsurface warming as short wave radiation penetrates to the base of the OBL. Both eddies and OBL can influence weather and climate patterns. In this project we propose to investigate the structure and dynamics of shallow convective boundary layers and their coupling to oceanic variability and mixing via ship-based surface flux and atmospheric boundary layer observations during the Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC). We propose continuous sampling aboard a research vessel that operates east of Barbados during the ATOMIC field program. The observing systems will be similar to those deployed in NOAA’s recent DYNAMO and PISTON studies. The ship will sample the atmosphere and ocean in the context of a larger array of ships and aircraft in cooperation with the Elucidating the role of cloud-circulation coupling in climate (EUREC4A) field program. Using in situ sensors, unmanned aircraft (UAS), and vertically-pointing Doppler remote sensing, we will measure and characterize mesoscale and synoptic variability in the surface fluxes, ABL and cloud turbulence as convective systems pass over the ship. The large-scale forcing will be determined by a combination of ship-launched balloon soundings and aircraft dropsondes associated with the larger ATOMIC/EUREC4A programs. We expect to work closely with P. Zuidema (U. Miami), S. de Szoeke (OSU), G. Feingold (NOAA/CSD) and P. Sullivan (NCAR) on LES modeling of the oceanic and atmospheric boundary layer and ABL-cloud interactions. The combination of LES and UAS plus radar-lidar velocity profiles will allow us to examine local gradient vs non-local (mass flux) boundary-layer flux profile parameterizations. We will coordinate with PMEL (Quinn) on UAS and aerosols observations. We will work with E. Thompson (APL-US) and J. edson (WHOI) on connecting atmospheric forcing with oceanic response. We will coordinate with the NOAA P-3 aircraft to set the mesoscale context of the ship observations. The P-3 will deploy dropsondes and AXBT (S. Chen NRL) and it will host the PSD Airborne Doppler W-band radar and the WSRA ocean surface wave radar.

Shallow cumulus convection in the Tropical Atlantic Ocean: Controls, responses, and mechanisms

Principal Investigator (s) Graham Feingold (NOAA/ESRL/CSD); Jan Kazil (CU-CIRES); Takanobu Yamaguchi (CU-CIRES)

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: GC19-303 | View Publications on Google Scholar

Abstract: Differences in the representation of shallow cumulus convection and cloudiness are a leading contribution to diversity in climate model sensitivity and climate projections. We propose to use numerical modeling of trade-wind cumulus from large eddy simulations to regional modeling, analysis of field observations, satellite data, and of reanalysis products to address the coupling between convective mixing, surface turbulent fluxes, and low-cloud radiative effects in largescale subsidence regimes. The modeling will be tightly integrated with the Atlantic Trade-wind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC, US) and the Elucidating the Role of Clouds-Circulation Coupling in Climate (EUREC4A, Europe) Ocean-Atmosphere field campaigns. We will examine the controls on the properties, statistics, and organization of shallow cumulus convection and cloudiness, and its response to ocean and atmosphere mean state and variability. Emphasis will be placed on processes that are unresolved or unrepresented in climate models and which contribute to diversity and biases in climate simulations and model-derived climate sensitivity. The objectives are: • Quantification of the mean state and statistical properties of shallow cumulus convection in response to atmospheric and oceanic mean state, and atmospheric and oceanic spatiotemporal variability • Quantification and characterization of mesoscale organization, its response to oceanic and atmospheric mean state and variability, and its role for the properties of trade cumulus convection and cloudiness • Characterization of feedback mechanisms between the atmosphere and the ocean that codetermine ocean-atmosphere interactions and the properties of trade cumulus convection and cloudiness Modeling will be carried out in close concert with the European and US assets to be brought to the field: aircraft observations (the NOAA P-3 and NOAA G-IV, the French ATR-42 and the German HALO), shipborne measurements (the NOAA R/V Ronald H. Brown and up to three European ships), and satellite remote sensing. The proposed work will further NOAA's long-term climate research goals and the goals of the NOAA CVP program by enhancing the understanding of the climate system and its predictability in a number of ways. First, it will elucidate our fundamental understanding of the trade-wind cumulus system by focusing on the meteorological/ocean surface factors that control cloud field properties (e.g. cloud fraction, condensate, and precipitation) through comprehensive modeling and observations at a broad range of scales (10s to 100s of km). Second, the extent to which variance in these factors at the sub GCM grid-scale affects these cloud field properties will reveal the model grid mesh required to adequately resolve them. Third, the model output and analysis of observations will together provide a wealth of data to inform development of GCM subgrid cloud and precipitation schemes for years to come.

Shipboard and Unmanned Aerial System (UAS) measurements of aerosol properties in the Coupled Ocean-Atmosphere System of the Northwest Tropical Atlantic

Principal Investigator (s) Patricia K. Quinn (NOAA/PMEL); Tim Bates (UW-JISAO; NOAA/PMEL); Partner: Phillip Hall (NOAA/UAS)

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: GC19-305 | View Publications on Google Scholar

Abstract: We propose to participate in the ATOMIC field campaign aboard the RV Ronald H. Brown in January/February 2020. Our objective is to improve the understanding of the effects of aerosol particles on clouds and radiation transfer over the Northwest Tropical Atlantic and the related impacts on the upper ocean. Aerosols in this region have both ocean-derived (sea spray and dimethylsulfide) and continental sources (European pollution, African dust, and biomass burning). Our hypothesis is that the temporal variability of atmospheric aerosols, through aerosol-cloud interactions and direct aerosol light scattering and absorption, influence the temporal variability in net radiation reaching the ocean surface and sea surface temperature. We will test this hypothesis with measurements of aerosol properties in the marine boundary layer on the ship and vertically and regionally with a UAS. This proposal directly addresses the call for proposals to study lower atmospheric boundary layer processes and their influence on the ocean. This work contributes to NOAA’s long term climate goal to strengthen scientific understanding of climate. We will be using the shipboard measurements that have been deployed on many field campaigns (VOCALS, DYNAMO, NEAQS, TexAQS, CalNex) and the UAS aerosol payload that has been deployed in Svalbard, Norway. The shipboard measurements will include aerosol number-size distributions, chemical analysis, cloud condensation nuclei (CCN) potential at supersaturations in the range of 0.1% to 2%, aerosol light scattering and absorption coefficients, and aerosol optical depth. The UAS measurements will include particle number concentration, aerosol absorption coefficient, filter collection for aerosol chemistry (Bates et al., 2013), aerosol size distributions from 130 to 3000 nm (Gao et al., 2016), optical depth measurements from a miniature scanning sun photometer (Murphy et al., 2016), cloud droplet number size distributions (CDP, DMT, Boulder, CO), temperature, and RH. The UAS will also be equipped with a flux measurement system (miniFLux) for the measurement of atmospheric thermodynamic state, turbulence, three dimensional winds, and surface and sky infra-red temperature (Fairall et al., in a separate proposal to this announcement). The measured aerosol and cloud properties will be regressed against net radiation and SST measured on the ship to test our hypothesis. The time series of these parameters will be analyzed in the context of the larger set of meteorological, oceanographic, and satellite data to investigate the processes and cause-effect relationships between aerosols, radiative transfer, cloud physics, precipitation, and surface ocean properties. Multivariate statistical analysis will be used to determine relationships between aerosol parameters (e.g., concentration, size distribution, composition) and cloud physics parameters, (e.g., thermodynamic profiles, cloud albedo and effective radius, vertical mixing, cloud base, cloud top, and precipitation rate). The products, time series of aerosol parameters and derived empirical relationships, will provide input to the ATOMIC/EUREC4A-OA and EUREC4A modeling communities. The final data sets will be archived on the PMEL Atmospheric Chemistry data server (http://saga.pmel.noaa.gov/data/) and NOAA PMEL’s ERDDAP Data Server.

Spatial structure of air-sea interaction in the tropical Atlantic Ocean

Principal Investigator (s) Elizabeth Thompson (U Wash/APL); Jim Thomson (UW/APL)

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: NA19OAR4310374 | View Publications on Google Scholar

Abstract: The proposed study will investigate the spatial structure of surface fluxes and waves due to organized patterns of low clouds along with ocean mesoscale eddies and fronts. These processes are known to coexist in all tropical oceans, but the details of their spatial variations have not been captured in any available datasets. Waves, trade winds, shallow clouds, and ocean eddies frequently coexist in the tropical northwestern Atlantic, where the ATOMIC field campaign has been planned. We propose an observation-based project as part of ATOMIC, in which we will investigate the spatial structure in the atmospheric and oceanic mixed layers when cloud patterns and ocean mesoscale eddies are present. We will use a distributed array of ten autonomous platforms called SWIFTs, a NOAA research vessel, and the NOAA P3 aircraft to make these observations. The Surface Wave Instrumented Floats with Tracking (SWIFTs) will offer a Lagrangian, distributed view of ocean features as they evolve and clouds as they develop overhead. The specific scientific questions raised about clouds and waves are: 1. How are surface energy fluxes influenced by organized cloud patterns within the trade winds and spatial gradients in SST across eddies? 2. How are surface waves, and in particular wave breaking, modified by ocean mesoscale variations in currents? 3. How are surface fluxes and turbulence in the oceanic and atmospheric mixed layers impacted by coinciding perturbations of cloud and wave conditions? 1-D air-sea interaction has been well-studied with decades of point-measurements collected from ships. That these measurements only cover a single point in space produces the largest gap in our understanding of air-sea interaction as well as the largest limitation of these datasets for use by numerical models. Research is needed on waves and air-sea fluxes, particularly in the tropics where ocean mesoscale features, persistent trade winds, and organized patterns of low-clouds coexist. The overarching theme of this work is to understand how fine-scale patterns in the oceanic and atmospheric mixed layers co-evolve so that, in the future, these processes can be represented in satellite data and predicted in numerical models with greater fidelity. Our project involves multiple observational datasets in the ocean, atmosphere, and at the sea surface. The project methodology systematically sifts through these data with objective analysis focused on physical processes. These steps will efficiently translate data into research results about coupled air-sea interaction that are actionable and relevant for operational environmental monitoring and numerical prediction.

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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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.

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