Climate studies

Ori Adam

Ori Adam

Senior Lecturer
Head of the academic committee of the Hebrew University Climate Science Center (HUCS)
Academic head of the Hebrew University Research Computing Service
Room 307 North
972-2-6586514

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In my group we study the large-scale dynamics of the atmosphere and oceans and the interactions between them, with emphasis on tropical climate dynamics. We aim to improve our understanding of variations in the present and past climates, and the governing dynamic and thermodynamic mechanisms that drive them. We also strive to mediate between theoretical and applied geophysical practices, by developing tools and methods for applications such as bias reduction in climate models, interpretation of paleo records, and quantification of variations of the tropical rain belt.
 

The theoretical tools we use include idealized models of the atmosphere and oceans which are amenable to mathematical analysis, an idealized general circulation model (FMS), as well as the analysis of comprehensive climate models (e.g., CMIP and PMIP models). We also aim to anchor the research in observations. To handle the large variety of observational and modeling datasets, we use a software tool called GOAT (Geophysical Observation Analysis Tool).

Current research projects include:

  • Idealised coupled cloud-ocean-atmosphere models
  • The effect of continent distribution on tropical climate
  • The relation of the atmospheric energy budget and tropical precipitation
  • Origin and nature of the double ITCZ bias
  • Variations of the tropical rain belt in the present and past climates
  • Relating the Hadley cell strength to the atmospheric energy budget
 
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Carynelisa Haspel

Carynelisa Haspel

Associate Professor
Head of the Undergraduate Specialization in Climate, Atmospheric Sciences, and Oceanography (CAO)
Room 302 North
+972-2-658-4974; +972-54-2122328

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Research

Scattering of Electromagnetic Radiation by Irregular Particles in the Atmosphere and Ocean

I work with models that describe the interaction of solar radiation with particles in Earth's atmosphere and oceans. I am particularly interested in how best (both accurately and efficiently) to model the effects of irregular particles, such as non-spherical particles, porous particles, and particles comprised of disorded/amorphous materials. Similarly, I am interested in how best to model mixtures of different components in the same particle. What are the differing effects of insoluble vs. soluble, solid vs. liquid, and absorbing vs. nonabsorbing components?

 

Underwater Polarization

While human beings only detect the intensity and wavelength of light, some species, both terrestrial and marine, are able to sense light's third attribute, polarization. Such species use polarization (the direction of the electric field) for different tasks such as orientation, navigation, prey detection, and communication. Under water, where the intensity signal is distorted by refraction and weakened by absorption, the ability to utilize polarization can be even more important than on land. For many years, theoretical models of polarized light under water were based on the theory of single scattering of the direct solar beam by small particles (Rayleigh scattering). Models accounting for scattering by larger particles (Mie scattering) have been approximate, and the most sophisticated models to date do not separate the effects of Mie scattering from effects of non-sphericity and multiple scattering. Furthermore, recent measurements under water reveal deviations from the polarization patterns predicted by models, in clear as well as semi-turbid waters. We are using a step-by-step approach to analyze the separate effects of particle size, particle size distribution, particle composition, particle shape, and varying orders of scattering on the underwater polarization pattern, with the goal of identifying the processes at play in different water types.

 

Light Pollution and the Light Environment Within Caves

My group has collaborated with scientists from Bar Ilan University and Beit Berl College in conducting the first in situ measurements ever of artificial nighttime light under water in a coral reef ecosystem. We found that the artificial light can penetrate to a depth of 30 m under the water, which could influence such biological processes as the tuning of circadian clocks, the synchronization of coral spawning, recruitment and competition, vertical migration of demersal plankton, feeding patterns, and prey/predator visual interactions. Similarly, we have collaborated in conducting the first in situ measurements ever of the state of light polarization within a mid-littoral cave. We found a relatively high degree of linear polarization of the light and a nearly constant orientation of the electric field of the light in winter months, which would improve the ability of the photosynthetic organisms there (cyanobacteria, microalgae, and macroalgae) to harvest light by orienting their light-harvesting receptors to the direction of the electric field.

 

Atmospheric Electricity

At Hebrew University, we have an ongoing collaboration with Tel Aviv University, The Open University, and the IDC Herzliya to study transient luminous events (TLEs), such as sprites, blue starters, jets, and elves, which occur above thunderstorm clouds. We have conducted our own observations of sprites and have constructed simple theoretical models to help explain some observed phenomena, such as the circular configuration of simultaneous sprites and the shift in the location of sprites from their parent lightning event.

 

Radiative Forcing of Climate

We look at how the presence of various types of particles affects the Earth's radiative-convective balance. Which particles cause a warming and which cause a cooling, and how does this change with their horizontal distribution? What is the most accurate way of representing subgrid scale features, such as inhomogeneous aerosol and cloud layers, in global models?

 

Curriculum Vitae

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photo credit:  Moti Milrod

Assaf Hochman

Senior Lecturer
309 North

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Lab name: Predictability of Extreme Weather (PredEx).

Interests:  Dynamics and predictability of extreme weather; Climate change; Paleoclimate modelling; Large-Scale circulation; Exoplanet climate dynamics; Public health adaptation to climate change

Research Interests 

The predictability of weather and climate is the estimation of uncertainty in model predictions. Atmospheric predictability is strongly dependent on the accuracy of initial conditions, on the representation of sub grid-scale processes and on climate change scenarios. The main purpose of my research is in reducing extreme climate and weather prediction uncertainties across spatial and temporal scales, especially over vulnerable populated regions. My work addresses the issue of weather and climate predictability from different perspectives including physical observations, computer modelling and mathematical/statistical theory.

 

Ongoing and future projects

  • Sub-seasonal Predictability of Hydrological Extremes in the Eastern Mediterranean (SPredHex).
  • Towards Implementing Dynamical Systems Tools for Extreme Weather Prediction over the Middle East and Israel (EMedPredEx).
  • Understanding Dynamics and Predictability of Extreme Mediterranean Cyclones (PredCEx).
  • Understanding Extreme Climate Characteristics in the Levant from a Regional Modelling Perspective (PredExClim).
  • Developing a dynamical systems framework for the broad range of terrestrial exoplanet climates (ExoClimDyn).
  • The Influence of Extreme Weather on Public Health in the Eastern Mediterranean (ExHealth).

Opportunities: Exciting, funded opportunities in these areas for M.Sc and PhD students as well as postdoctoral research associates.

For more information, please contact me: assaf.hochman@mail.huji.ac.il

 

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Dorita Rostkier-Edelstein

Associate Professor (Adjunct)
Room 304 South
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M3 Lab, Mesoscale Meteorology and Modeling
 
Research Interests 
 
My research focuses on mesoscale meteorology and modeling and pursues to improve numerical weather and climate prediction at high spatial resolution, with special attention to planetary boundary layer (PBL) phenomena. I have put special emphasis on developing data assimilation (DA) approaches that can optimally improve model initial conditions in the PBL by assimilation of observations into the model. Moreover, much of my efforts have been devoted to developing and improving dynamical downscaling methods to efficiently achieve computationally expensive high resolution climatographies (model calculated climatology). In addition, I have developed analogues and weather-regimes based downscaling methods and applied them in seasonal forecasts and future climate predictions of precipitation. The use of observations and models provide me the tools to better understand the physical and dynamical processes responsible for the mesoscale phenomena of interest such as sea-land breeze, foehn and hydraulic jumps, among others. I have dedicated efforts to study meteorological phenomena beyond the PBL including transport of mineral dust. 
 
Ongoing and future projects:
  • Data assimilation of opportunistic observations to improve convection scale precipitation forecasts using WRF model and DART ensemble Kalman filter DA.
  • Mesosocale modeling over urban areas for air pollution applications using WRF model with mesoscale urban parameterizations
  • Analysis of Mediterranean cyclones in present and future global and regional climate models and their connection to precipitation using analogues downscaling methods.
  • Improvement of atmospheric dust-aerosol model by incorporation of a turbulent thermal diffusion parameterization and improved dust-soil emission parameters using WRF-Chem model, laboratory and field measurements.
Curriculum Vitae
 
 
 
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