About Me

I study interactions between climate and terrestrial carbon and water cycling from canopy to global scales. I am mainly interested in how plants are affected by climate change, and in turn how large scale plant-atmosphere exchanges impact climate. My research interests are broadly classified as:

  • Regional-scale atmospheric modelling to quantify sources and sinks of CO2.
  • Canopy-scale meaurements of trace gases (OCS,13CO2), eddy covariance flux, and ecopshyiological data (sap-flow, high- frequency thermal imaging of canopies) to understand plant-atmospheric interactions of CO2, H2O at the ecosystem scale.
  • Using satellite imagery to quantify spatial and temporal patterns of low lying cloudcover.

Currently I am a postdoc in the Carbon Cycle Greenhouse Gases Division at NOAA's Global Monitoring Laboratory supoervised by Dr. Caroline Alden and Dr. John Miller.

Education:
  • PhD, Forest Ecosystems and Society, Oregon State University 2018
  • M.A., Geography, University of California Santa Barbara 2013
  • M.Sc., Environmental Sciences, University of East Anglia 2010
  • BSc. (H), Chemistry, University of Delhi 2009

Publications: Google Scholar

Research

Motivation:
The carbon balance (Net Ecosystem Exchange or NEE) of Earth’s ecosystems is a first order ecological property with wide-ranging implications for climate change, global food security, and biodiversity. Earth’s terrestrial ecosystems drive the interannual variability in the atmospheric growth rate of CO2. These ecosystems also act as a sink, removing ~ 25% of anthropogenic carbon, and this sink has so far kept pace with increasing anthropogenic emissions. Many hypotheses have been suggested for the increasing land sink, including CO2 fertilization and regrowth of northern latitude forests, but compelling evidence for any particular mechanism acting at large scales remains elusive. There are two main reasons for this. First, NEE represents the ecosystem state: a balance of ecosystem photosynthesis (gross primary productivity or GPP) and respiration, neither of which are measurable beyond the scale of a leaf cuvette or a soil chamber. This makes it challenging to measure and scale NEE from plot or site-level to large regions. Atmospheric CO2 measurement networks, allow us to infer current biome-scale (i.e., 104-106 km2) NEE using inverse models, but measurement networks are sparse and under-sample large parts of the world, including critical regions such as the Tropics and the Arctic. I use a combination of ecosystem scale (1 km2) measurements and biome-scale models to better characterize ecosystem-scale processes and constrain biome-wide trends.

Research area I: Constraining North American Carbon flux using satellite retreivals of XCO2

This is the focus of my current Postdoctoral work. Inverse models combine carefully calibrated measurements of CO2 mole fraction with models of atmsopheric transport to infer NEE at regional to global scales. However, measurement networks remain sparse in large parts of the world. Satellites such as NASA's OCO-2 can potentially provide unprecedneted spatial coverage information, but data need to be highly precise and accurate. I am using the CarbonTracker-Lagrange regional model. CarbonTracker-Lagrange is a regional atmospheric inverse model in which surface flux is optimized using surface-sensitivity arrays from high resolution simulations of atospheric transport and atmospheric measurements of CO2. Using a suite of inversions, we seek to understand at what spatial and temporal resolutions OCO-2 can provide robust estimates of NEE and quantify the magnitude of flux uncertainty reduction. As a first-step, we leveraged the dense network of NOAA GML in-situ measurements over North America to assess bias in XCO2. We found small biases that were similar to the signal of interest. The manuscript is available here. This work is supported by a NASA Carbon Monitoring System grant to P.I. Kaiyu Guan (UIUC), and Co-P.I. Caroline Alden (CIRES/NOAA-GML).

Research Area II: Inferrering ecosytem-scale photosynthesis and biosphere-atmosphere interactions from Carbonyl Sulfide

This was the focus of the PhD dissertation, Under the supervision of Prof. Christopher Still. Carbonyl Sulfide (OCS) has recently been proposed as a proxy for estimating photosynthesis from ecosystem to global scales. I installed a profiling system to measure drawdown of OCS, H2O, CO2, and CO at an old-growth Douglas Fir/ Western Hemlock forest site (Wind River, WA: US-wrc). With the help of co-located eddy flux data, I quantified OCS uptake by the forest, and related it to photosyntheis and transpiration. We found significant nocturnal uptake of OCS by epiphytes (e.g, lichen, mosses) at the site. We found that during the day, OCS uptake was sensitive to diffuse radiation, and also quantified dynamics of ecosystem OCS exchange during heatwaves. These findings were published here and here. I am currenty working on two other manuscripts. In the first one we estimate a large nocturnal sink of OCS in the canopy, that is not related to uptake by leaf stomata but related to uptake by epiphyes. This is the first study to quanitfy epiphyte uptake of this gas at the ecosystem scale. In the second manuscript (in review) we use our published estimates of daytime OCS uptake to help explain the response of the old-growth forest to wildfire smoke.

Research Area III: Measuring and modeling canopy temperatures

Fig. 1 from Still, Rastogi et al., (2021)

Temperature is a fundamental component of all aspects of plant function. The temperature of leaves in particular is important in determining plant metabolism and therefore the exchange of CO2, water, energy with the environment. Controls of leaf temprature therefore has been a subject of extensive study by plant physiologists, ecologists, and atmospheric scientists. On the global scale, satellite-based thermal imaging of leaf temperature (now available for almost 5 decades) has been used to infer large scale land-atmsopheric water fluxes. While there are numerous studies at the leaf and global scales, temperature at the canopy scale is less well understood. I am interested in using high- frequency thermal imaging to learn what canopy temperature can tell us about ecophysiology of vegetated systems as well as plant-atmosphere interactions. Recently, we published a review highlighting some results from in-situ thermal imaging of forest canopies here.

Research area IV: Using remote sensing observations and ground based observations to quantify trends in coastal low-lying clouds and fog.

Fog on Santa Cruz Island in California.

Low lying cloud-cover and fog are important components of the water budget in many semi-arid/arid ecosystems. In these systems, plants rely of low cloud and fog to alleviate drought stress. While cloudcover reduces ambient air temperature and the atmospheric demand of moisture from the leaf surface (VPD), fog droplets can coalesce on leaf surfaces and provide moisture for plant function. Using multi-scale remote sensing data, weather ballons, and local airport observations I quantified spatio-temporal patterns of cloud and fog over the Channel Islands of California. A key component of this work was to discrimate regions that experienced low-cloudiness from those that were inundated by fog. Cloud and fog maps (fogscapes!) I produced have been used by the Nature Conservancy in conserving and restoring these landscapes. More recently, using similar methods, colleagues and I investigated spatio-temporal patterns of low-lying clouds over the Pacific Northwestern US. We detected a decreasing trend in 22 years of satellite observations of summer time cloud cover in the areas bounded by the coast range and the Cascade mountains.

Community

Teaching:

My overarching goal in teaching is to prepare students to be effective professionals and citizens in their future careers. There are a few components to this: fostering critical thinking and independent thinking, equipping students with necessary research tools, and training them to be excellent communicators. I believe that these are a necessary subset of skills for environmental professionals in a variety of disciplines.

In graduate school I was a teaching assistant (TA) for courses at various undergraduate levels in two different departments: Geography, and Forest Ecosystems and Society. My TA experiences relied heavily on active learning practices and promoting student engagement through collaboration and hands- on learning. The courses ranged from introductory Earth and atmospheric sciences to a multidisciplinary upper-division course that combined geology with history and ecology, and a quantitative research methods course, also for senior undergraduate students. These experiences taught me about communicating course material to different audiences. At the University of California, Santa Barbara I was a TA for introductory courses titled ‘Oceans and the atmosphere’ and ‘Land, water and life’ respectively. In these courses, we helped students understand broad and fundamental concepts relating to Earth’s properties at local to global scales. We used simple measurements in a campus setting to understand complex earth-system phenomena, e.g., measuring the temperature of various collocated objects to learn about albedo and its effect on surface temperature, and measuring sky- temperatures on clear and cloudy days to help understand the greenhouse effect. For an upper division course at Oregon State University, I was a TA for ‘Scientific methods for analyzing natural resource problems. In this course, we asked students to first identify a natural resource problem and then throughout the course helped them to understand it in a quantitative framework. This involved thinking independently, identifying and reading relevant scientific literature, and quantitative modeling. Student topics ranged from modeling the impact of wolf reintroduction on elk population in Yellowstone National Park, to modeling plastic waste in the Pacific Ocean. We used open-access, easy to use educational software, and students gave presentations and a written final project at the end of the class. In these classes, I also occasionally gave guest lectures. More recently in October 2020, I was invited to talk to undergraduate students at the City University of New York to give a guest lecture on the COVID-19 pandemic and the carbon cycle. Here, I explained the basics of climate change and the carbon cycle and synthesized recent research on the impact of lockdowns on the global CO2 growth rate.

As I develop and teach classes, I intend to learn more about effective teaching techniques. I am particularly interested in the concept of the ‘flipped classroom’ where students watch asynchronous recorded lectures at home, and class time is used to solve homework problems and discussions. I think this breaks the imposed linearity of class time, and helps more students develop a relationship with the instructor by having a longer amount of active engagement with the students. I will also strive to create an inclusive classroom, where students from diverse backgrounds feel safe, empowered and respectful of each other. I would also like to develop courses focusing on biosphere-atmosphere interactions and environmental change, applications for Bayesian estimation in carbon cycle science, and scaling of ecophysiological processes from leaf to global scales.

Diversity, Equity & Inclusion:

Contemporary carbon cycle science and the fate of terrestrial ecosystems are crucial to study, in part due to anthropogenic influence on Earth’s carbon cycle and climate. All terrestrial ecosystems are both directly (e.g., deforestation) and indirectly (e.g., global climate change) impacted by the actions of humans. While these actions have global consequences, the decisions behind these actions have been made by a select group of people. For example, over 70% of all anthropogenic emissions can be traced to a small number of fossil fuel corporations, who have worked to create global economies based on fossil fuels and exploitation of natural resources. At the other end of the spectrum, movements by Indigenous peoples across the world have resisted such actions. These movements are often against colonial or neo-colonial practices of land grabbing, but also have broader consequences. For instance, a recent report estimated that Indigenous resistance movements have averted 25% of all U.S. and Canadian emissions. This is a rare example of research that offers an Indigenous perspective on carbon emissions, underscoring the need for diversifying the earth sciences. It is also not peer-reviewed, which excludes it from earth science scholarship. Earth sciences, which includes contemporary carbon cycle science, continues to exclude large parts of society through its systems and biases.

The lack of diversity in Earth Sciences is attributed to the hostile environments , racism, and the lack of mentors. As I develop my scholarship and teaching on contemporary carbon cycle science, I want to be conscious about my own positionality, and work on creating a safe, welcoming and inclusive environment. I am a dominant caste South Asian male residing in the U.S., which brings a set of privileges as well as a range of experiences of being othered. As an international student, I often felt a sense of exoticism, often by well-intentioned people and colleagues. I had to quickly formulate strategies to assimilate, relying on perceptions and occasional pieces of advice. I also realized that I was not alone, that many international colleagues were also doing the same. We also felt underrepresented, even in conversations about diversity, inclusion and equity (DEI). During my PhD, I was part of a student-led initiative called the “Diverse Perspectives in Forestry Group” where we held discussions on DEI, invited speakers and organized events. By supporting each other through this group and informally, we were in-fact doing a lot of the “DEI- work”, even as the DEI infrastructure around us was often oblivious. Kuheli Dutt notes “Diversity and inclusion cannot exist without a sense of belonging”, and I will strive to create a sense of belonging for students and colleagues in my lab, and in the department.

I will work towards creating an anti-racist, (see also here), anti-ableist and anti-queer/transphobic research group. I also plan to organize graduate seminars on these topics, or join one that exists. Some examples of focused reading are recent work by Robin Wall Kimmerer on incorporating Indigenous perspective in ecological research, and by Max Liboiron on conducting research with anti-colonial values. Lastly, I think this is an important and exciting time as conversations on and beyond DEI are gaining momentum and including people who can actually offer diverse perspectives. I aim to sustain these in my research group.

Contact

bharat.rastogi@noaa.gov

bharat.rastogi@colorado.edu

Address: 2D-126 David Skaggs Research Center, Boulder CO: 80305

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