Nadav Bendavid's Qualifying Exam

Nadav Bendavid will stand for the Qualifying Examination for acceptance into candidacy for the Ph.D. degree on Monday, May 20 at 9:00 am in the Marsh Hall classroom. All faculty are welcome and invited to attend. Copies of Nadav’s dissertation prospectus and qualifying exam questions and answers can be obtained from the Doctoral Program Office (contact: elisabeth.barsa@yale.edu).
Committee members:
• Prof. Paulo Brando (Chair)
• Prof. Mark Bradford
• Dr. Marcia Macedo (Woodwell Climate Research Center)
• Dr. Susan Trumbore (Max Planck Inst.)

Question 1:
The Amazon rainforest plays a key role in regional and global climate regulation, influencing rainfall and temperature. Large-scale deforestation (e.g. for pastures or croplands) trigger important changes in these processes, but the specific impacts can vary markedly across different regions of the Amazon.
Part A: Forest Controls on Climate. Critically analyze, compare, and contrast the expected climate feedbacks associated with forest clearing in the southeast Amazon (e.g., Mato Grosso) and the northwest Amazon (e.g., Roraima). Consider both immediate and long-term effects on key climate variables such as total rainfall, rainfall seasonality, air temperature, and air dryness. Summarize the current research on the trends in (observed) rainfall data in these two regions over the past few decades. How have rainfall patterns changed as agropastoral land uses expanded? What are the local vs. regional impacts? Support your analysis with relevant theories, empirical research, or modeling.
Part B: Climate Consequences. Using CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data) and the tool of your choice (e.g., Google Earth Engine, Climate Engine, R), calculate the following climatic metrics to evaluate shifts in climate over Mato Grosso and Roraima since over the last two decades: (1) mean annual rainfall; (2) standard deviation of (monthly) rainfall; (3) annual rainfall anomaly index (deviation from the long-term average); (4) maximum consecutive dry days; (5) maximum climatological water deficit (MCWD).
Provide detailed methods for your calculations, including a justification of your choice of tools, datasets, and any preprocessing steps. Discuss how these metrics could be used to support or refute the hypotheses presented in Part A regarding the impacts of forest clearing for agriculture on climate.
* Your response should include a comprehensive analysis supported by peer-reviewed literature, data visualizations, and methodological explanations. Please provide any code or datasets used in your analysis to ensure the reproducibility of your results.
Question 2:
Part A: Compare the Evapotranspiration (ET) from the tower flux data (ET) for croplands and forests available to you at the Tanguro site with ET estimates from MODIS products accessed via Climate Engine or Google Earth Engine (or any other online tool available to you). Provide a mechanistic explanation for the similarities and differences observed between the ET estimates from tower data and MODIS products. In your discussion outline the fundamental principles of the eddy covariance method used at the Tanguro site and the algorithm behind the MODIS ET product (MOD16); and explain how these methods estimate evapotranspiration (ET) and the theoretical basis for each.
Part B: Using MODIS products, analyze the seasonal and interannual variability in ET. Discuss the potential mechanisms responsible for these variations. Provide specific examples or case studies to support your analysis, referencing the temporal coverage and spatial resolution of MODIS data as applicable.
Part C: Discuss how elevated atmospheric CO2 (eCO2), particularly its effects on water-use efficiency (WUE), might directly influence ET and energy balance. Explore potential feedback mechanisms to the climate system resulting from changes in ET and energy balance under varying eCO2 scenarios. Link the mechanistic insights from Parts A and B to theorize how these processes might interact under different environmental scenarios.
Question 3:

Describe and explain how you would design a verification system for the climate mitigation effects of land management interventions. In doing so, compare and contrast the specifics, pros, and cons of the system you propose with existing forest and cropland protocols produced for voluntary and regulatory carbon markets (e.g., by entities such as Verra). Make sure you justify why you chose the specific protocols you chose for comparison.

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