About

Professor Elie Bou-Zeid is a faculty member in the Department of Civil and Environmental Engineering at Princeton University. His research focuses on the integration of theory, numerical simulations, and experimental observations to study flow and transport in the Atmospheric Boundary Layer, the lowest layer of the atmosphere where humans live and have a direct impact on the planet. His work extends from the fundamentals of turbulent flow and heat transfer in that layer to various applications including the built environment and its environmental quality, energy efficiency in buildings, urban sensor networks and their design, wind farm design and wind energy forecasting, and surface-atmosphere exchanges over fractured polar sea ice. Professor Bou-Zeid holds a PhD in Environmental Engineering from Johns Hopkins University, along with a master's degree in Mechanical Engineering from the same institution, and degrees from the American University of Beirut. He has received numerous honors and awards, including the Helmut E. Landsberg Award from the American Meteorological Society in 2026, the Atmospheric Sciences Ascent Award from the American Geophysical Union in 2025, and the Beyond Bauhaus - Prototyping the Future Award in 2019. He is involved in multiple associated faculty roles across departments and institutes, including Mechanical and Aerospace Engineering, Atmospheric and Oceanic Sciences, the High Meadows Environmental Institute, the Princeton Program in Urban Studies, the Andlinger Center for Energy and the Environment, and the Center for Information Technology and Policy. His courses include Environmental Fluid Mechanics, Science and Solutions for Cities on a Changing Planet, Boundary-Layer Meteorology, and Flow and Turbulence in Geophysical Systems.

Selected publications

• Daily evapotranspiration changes during heatwaves at 32 NEON sites, 2019-2021

  Open MIND · 2026-02-17

  datasetOpen access

  This dataset provides partitioned evapotranspiration (ET, the combined loss of water from soil and plant surfaces) anomalies during heatwave events—soil evaporation (E) and transpiration (T)—for 268 heatwave events across 32 National Ecological Observatory Network (NEON) flux sites in the contiguous United States from 2019–2021. Using an ensemble of four high-frequency turbulence methods (Flux-variance Similarity, Conditional Eddy Covariance [CEC], CEC with Water-Use Efficiency, and Conditional Eddy Accumulation; see Zahn and Bou-Zeid 2024), half-hourly transpiration-to-evapotranspiration (T/ET) ratios were derived from 20 hertz (Hz, cycles per second) eddy covariance measurements of carbon dioxide (CO₂) and water vapor (H₂O) concentrations. The dataset spans six vegetation types including evergreen and deciduous forests, grasslands, cultivated crops, shrublands, and emergent herbaceous wetlands. Data Package Contents: The dataset includes a single CSV (comma-separated values) file containing daily anomalies (deviations from baseline conditions) for transpiration (Delta_T), evaporation (Delta_E), total evapotranspiration (Delta_ET), and T/ET ratio (Delta_T_ET) during each day of identified heatwave events. The file also includes site codes, dates, heatwave event identifiers, and day-of-heatwave indicators. The CSV file can be opened with spreadsheet software (Microsoft Excel, Google Sheets) or programming environments (Python, R, MATLAB). This resource enables researchers to investigate ecosystem-specific responses to thermal extremes, validate land surface model partitioning of ET fluxes, and examine feedbacks between water cycling and surface energy balance during heatwaves. The dataset is particularly valuable for studies linking vegetation hydraulic strategies to climate resilience, as it captures the divergent responses of shallow-rooted versus deep-rooted ecosystems. Potential applications include improving drought early warning systems, informing irrigation management strategies, and advancing our mechanistic understanding of land-atmosphere interactions under extreme heat conditions.

  OA PDFDOI

• Quantifying the economic costs of urban heat islands in the USA

  2025-05-21

  preprintOpen accessCorresponding

  The combination of global warming and urban heat islands (UHI) leads to a range of socio-economic problems, including labor productivity reduction, health burdens, and increased energy demand. While heat mitigation strategies can substantially alleviate local heat stress, practical climate mitigation policies require a careful evaluation of the benefits and costs of different heat mitigation solutions. The baseline cost of UHI without intervention is of critical importance since it serves as a reference for comparing different mitigation options and informs the unquantified economic losses that cities endure due to their UHIs. Previous economic studies have focused on the economic effects of climate change and greenhouse gas mitigations, yet a quantitative assessment of this baseline cost of UHI remains lacking due to an almost universal lack of urban representation in climate datasets. This gap limits policymakers’ ability to develop economically rational action plans to reduce urban heat stress.This study aims to: (1) quantify the economic implications of UHI in the contiguous United States, and (2) perform a cost-benefit analysis of various mitigation strategies to develop cost-efficient heat mitigation portfolios. Using high-resolution climate data with urban climate representation and sectoral impact models, we have quantified the UHI-induced additional mortality rate, energy consumption, and labor loss. By incorporating monetization methods in econometric models, our preliminary assessment shows that UHI significantly amplifies the economic costs associated with regional heat stress. Our ongoing analyses aim to estimate the cost of implementing various urban adaptation strategies, including urban green, radiative cooling, and blue infrastructure, and provide a cost-benefit assessment to guide policymakers in designing effective urban climate adaptation plans.

  PublisherDOI

• Investigating the Interaction of Tropical Cyclone-Heatwave Compound Hazards in Urban Environments

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Stratification, turbulence organization, and pressure-strain effects on surface-layer turbulence anisotropy

  ArXiv.org · 2025-12-03

  preprintOpen access

  At large scales, the Reynolds stress tensor exhibits notable anisotropy, a key feature of all wall-bounded turbulent flows. Yet, how the drivers of this anisotropy evolve with shearing and thermal stratification in the atmospheric surface layer (ASL) remains a daunting challenge for theory and models alike. Here, the velocity variance budgets are used to explore the evolution of anisotropy in the daytime ASL close to the surface, region known to be problematic for large eddy simulations. A special focus is placed on the importance of slow and rapid pressure-strain correlations and the role of transport on partitioning the turbulent kinetic energy among the velocity components. Results obtained from near-surface observations of four datasets over flat and horizontally homogeneous terrain show persistent anisotropy over a wide range of flux Richardson numbers $R_{if}$ and wall-normal distances, and highlight the importance of different processes in three distinct flow regimes, roughly related to dynamic ($|R_{if}|\ll1$), dynamic-convective ($|R_{if}|\sim1$) and convective ($|R_{if}|\gg1$) regimes of the ASL. In particular, close to the surface in the dynamic-convective regime, a drop in wall-normal velocity variance and a substantial increase of spanwise velocity variance are shown to result from the increasing role of pressure transport and rapid distortion, related to turbulence organization. This behaviour is not captured by the classic Rotta closure but requires the inclusion of both rapid pressure-strain and transport terms. In all regimes wall blocking is found to influence turbulence close to the surface, thus requiring the adoption of an anisotropic Rotta model to accommodate its effects.

  PublisherOA PDFDOI

• From Standard to Bayesian: Revisiting Ocean Color Model Evaluation

  2025-06-25

  preprintOpen accessSenior author

  • We develop Bayesian ocean color algorithms that provide robust uncertainty estimates for chlorophyll-a predictions. • Bayesian model selection using BIC outperforms traditional metrics for evaluating ocean color algorithm performance. • Our results show that simpler models may perform better than standard models, depending on the dataset and sensor.

  PublisherOA PDFDOI

• Indoor, Outdoor, and Power Implications of Rooftop Photovoltaic Panels Deployment

  2025-05-21

  preprintOpen accessCorresponding

  A swift transition to renewable energy is essential for meeting global demand and mitigating climate change, yet land scarcity presents a challenge. Installing photovoltaic panels on urban surfaces, such as roofs and walls, offers a promising solution but may alter energy flows and urban microclimates. Before deploying building-integrated photovoltaics, it is crucial to consider:How do different layouts affect energy transfer from roofs? What are the implications for the magnitude and timing of building energy demand and sensible heat emissions to the urban boundary layer? How sensitive are roof responses and heat transfer to variations in meteorological drivers such as shortwave radiation, air temperature, and wind speed? To address these questions, we developed a multi-element energy budget model to simulate solar roof configurations. Our results show that, in cold climates, solar roofs reduce conduction into the building almost as much as cool roofs, while also generating energy to offset heating demand. In hot climates, inclined panels are preferable in reducing indoor heat gains, outperforming cool roofs while producing clean energy for cooling.These benefits are not free. Solar roofs increase sensible heating of the UBL relative to a cool roof, exacerbating the urban heat island effect during peak insolation. However, the peaks in sensible heat occur before the peaks in air temperature (moderating the impact on daytime thermal comfort), and notably, solar roofs mitigate nighttime UHI which is critical for reducing heat-related health risks.An elasticity analysis of heat fluxes reveals that, under intense solar radiation, solar roofs shift more of the excess heat to sensible heat. In warmer climates with higher air temperatures that reduce sensible heat losses, the conduction of heat into the indoor building increases. Although wind generally has a moderate impact on fluxes, its variability modulates heat partitioning, favoring greater sensible heat flux and reduced conduction into the building.

  PublisherDOI

• Open questions in atmospheric turbulence: A synthesis from the centenary workshop “100 years of turbulence: Innsbruck 1922 -2022”

  Journal of the European Meteorological Society. · 2025-11-19 · 3 citations

  articleOpen access

  In this contribution, we summarize salient findings, discussion points, and community recommendations resulting from the workshop “100 Years of Turbulence: Innsbruck 1922 –2022”, held as a centenary celebration of the First meeting on “Hydro- and Aero-dynamics” that took place in Innsbruck in 1922. Participants from numerous countries and continents discussed the significant achievements and major remaining challenges related to atmospheric turbulence over different types of complex surfaces (inhomogeneous terrain, impact of orography, and large roughness elements such as trees or buildings), as well as stratified and non-stationary turbulence. For each of these contexts, directions for future research were proposed, recognizing that current numerical weather and climate models treat turbulence as an unresolved process at the grid-cell scale.

  PublisherDOI

• On the performance of human thermal stress models in the outdoors against observations

  Energy and Buildings · 2025-05-06 · 1 citations

  articleOpen access

  • Observed and modeled skin temperatures were compared for thermal stress assessment. • JOS-3 performed better than the LHEB model within the PUCM framework. • LHEB overestimates skin temperature likely due to lacking human thermoregulation. • JOS-3 can reliably link with validated UCMs for urban thermal stress evaluation. Urban overheating significantly impacts human well-being, requiring outdoor thermal comfort assessments. This research aims to assess the performance of models to calculate mean skin temperature in outdoor environments against measurements. The study compares a Lumped Human Energy Budget (LHEB) model, which is a simplified representation of the human body thermal state developed in an Urban Canopy Model (UCM), and the more sophisticated thermoregulation model JOS-3. Skin temperatures computed with the LHEB one-node model were significantly higher than observed values (RMSE: 1.71 – 2.76 °C). This variation, however, cannot be attributed to differences between simulated and monitored environmental data. It probably results from simplifications assumed in the human energy balance, such as disregarding dynamic thermoregulation processes, which considerably impact outdoor human comfort. The JOS-3 model, more advanced in terms of heat exchange and thermoregulation processes, performed better (RMSE: 0.21 – 1.62 °C, considering sessions when sensors were stabilized). Since all JOS-3 meteorological inputs can be provided by a UCM, the model can be directly integrated into UCMs for investigating the effects of urban overheating and mitigation strategies on human thermal stress. Therefore, it can serve as the human thermal comfort module for UCMs. The collected dataset is the first to combine measurements of the biophysical energy model outputs and the required UCM inputs, and to evaluate the reliability of the LHEB and the JOS-3 models outdoors, contributing to improve thermal stress modeling in inter-building urban contexts, which is an important approach for cities livability improvement and designing effective human-centric heat reduction measures.

  PublisherDOI

• The diverging predictions of extreme heat risk indicators

  2025-05-21

  preprintOpen accessSenior authorCorresponding

  About two hundred thermal indicators exist and yield divergent assessments of heat stress impacts and mitigation. Thus, examining how these indicators respond to various meteorological variables and exploring the implications for their practical use is imperative. Using a correlation analysis, we cluster common indicators into three types: 1) human energy budget models, 2) integrated weather indices, and 3) thermal perception indicators. Distinct extreme hot conditions are identified differently by the various clusters of indicators: human energy budget models are more responsive to micro-scale variation in wind and radiation; while integrated weather indices mainly capture synoptic moist heat extremes. These biophysical indicators also do not concur with a metamodel of thermal perception, developed here using a meta-analysis of coefficients in existing thermal sensation vote equations. The developed thermal perception metamodel is more sensitive to radiation fluxes than other thermal stress indicators. It implies that humans’ thermal sensation may underestimate humid heat stress at nighttime, which can pose a significant risk to human health in hot, humid cities such as Chennai (India) and Dakar (Senegal) and across the Global South. These findings deepen our understanding of heat stress variability on humans and provide a framework for selecting suitable indicators in future applications.

  PublisherDOI

• Global urbanization indirectly ‘enhances’ the carbon sequestration capacity of urban vegetation

  Geography and sustainability · 2025-01-18 · 22 citations

  articleOpen accessSenior author

  • Globally, urbanization’s direct impact on NEP is universally negative. • Globally, urbanization’s indirect impact on NEP is positive in 88 % of cities. • Urbanization’s indirect impact is strongest in hydrothermally constrained areas. • Anthropogenic factors dominate the indirect impacts of urbanization on NEP. • Urbanization’s indirect impact on NEP is related to the level of urban development. Urbanization radically alters the climatic environment and landscape patterns of urban areas, but its impact on the carbon sequestration capacity of vegetation remains uncertain. Given the limitations of current small-scale ground-based in situ experiments, the response of vegetation carbon sequestration capacity to urbanization and the factors influencing it remain unclear at the global scale. Using multisource remote sensing data, we quantified and differentiated the direct and indirect impacts of urbanization on the carbon sequestration capacity of vegetation in 508 large urban areas globally from 2000 to 2020. The results revealed that the direct impacts of urbanization were generally negative. However, 446 cities experienced an indirect enhancement in vegetation carbon sequestration capacity during urbanization, averaging 19.6 % globally and offsetting 14.7 % of the direct loss due to urbanization. These positive indirect effects were most pronounced in environments with limited hydrothermal conditions and increased most in densely populated temperate and cold regions. Furthermore, indirect impacts were closely related to urbanization intensity, human footprint, and level of urban development. Our study enhances the understanding of how the carbon sequestration capacity of vegetation dynamically responds to changes in the urban environment, which is crucial for improving future urban vegetation management and building sustainable cities.

  PublisherDOI

Labs

• Elie Bou-Zeid LabPI

Awards & honors

• The Helmut E. Landsberg Award, American Meteorological Socie…
• The Atmospheric Sciences Ascent Award, American Geophysical…
• ‘STAC Distinguished Scientific/Technological Accomplishment…
• Beyond Bauhaus - Prototyping the Future Award for our CityRe…
• Faculty Advancement Award (E. Lawrence Keyes Jr. / Emerson E…