Vegetation-precipitation coupling in the tropics: challenges and opportunities

Transcription

1 Vegetation-precipitation coupling in the tropics: challenges and opportunities Dr. Benjamin R. Lintner (PI) Assistant Professor Department of Environmental Sciences Rutgers, The State University of New Jersey 14 College Farm Rd New Brunswick, NJ February 2014

2 II. PROJECT SUMMARY The behavior of the tropical terrestrial hydrologic cycle, especially precipitation and its coupling to vegetation, represents a key uncertainty limiting our ability to project the evolution of the coupled ecosystem-climate system in the 21 st century. The proposed working group will consider what we currently know, and what we still need to learn, about the two-way linkages between vegetation and precipitation, which are crucial for interpreting observed tropical ecosystem-climate interactions and embedding these interactions in state-of-the-art climate or earth system models. As a starting point in this challenging issue, our working group will focus on the following question, namely: To what extent does vegetation influence terrestrial tropical precipitation characteristics, including its initiation, frequency, intensity, spatial patterns, and temporal variations? By bringing together experts in biology and ecology the traditional core of OTS along with experts in atmospheric and climate science, earths system modeling, and ecohydrology, our working group will provide a solid foundation for developing capacity in an area of critical, 21st century need. During a 3-day workshop to be held at La Selva Biological Station in either late 2014 or early 2015, members of our working group will share relevant results from their own research and brainstorm about the current state of knowledge regarding vegetation-precipitation coupling in the tropics, the outstanding challenges for observing and modeling this coupling, and areas in which we might reasonably expect to make progress. We will evaluate how we can utilize the wealth of 50 years of data from the OTS community to inform modeling efforts and validate the output of models, and moving forward, how we might design experiments and employ instruments at one or more OTS research sites to assess vegetation-precipitation coupling processes. Expected outcomes of our working group include: (1) a synthesis paper, including recommendations for how OTS research and facilities could be used to elucidate vegetation-precipitation coupling; (2) the genesis of ideas for cross-cutting proposals and potential funding sources/programs; and (3) establishing connections with Costa Rican-based colleagues for developing joint research efforts. OTS Grant Competition Emerging Frontiers in Tropical Science 2

3 III. PROJECT DESCRIPTION 1. Problem statement and working group focus question How the terrestrial hydrologic cycle the supply of and demand for water may change in response to a warming climate represents one of the outstanding challenges in climate science in the early 21 st century. Within the tropics in particular, this issue has generated widespread concern about the vulnerability, resilience, and adaptive capacity of both natural and human systems. While recent decades have seen great advances in the development of computational tools for studying climate, projections of future hydroclimate over tropical land regions remain subject to great uncertainty, especially on the spatial scales (e.g., watersheds or river basins) on which decision-making and strategic planning for climate change need to occur. Arguably, one of the principal sources of uncertainty and thus a limit to our skill in projecting future climate change over tropical land regions in current-generation climate models is the representation of convection and precipitation. While the (mis)representation of terrestrial convective processes may be tied to a number of factors, our perspective is that we need to focus on the near-surface environment where the terrestrial biosphere meets the atmosphere. How the land surface ultimately couples to precipitation, especially across the diverse environments encountered in the tropics, requires detailed knowledge of the two-way interactions involving vegetation phenology and physiology, soil moisture and root zone processes, surface fluxes of heat, moisture, and momentum, and thermodynamic and dynamic profiles in the overlying atmospheric boundary layer. Embedded within this are a host of issues of cross-scale interactions and heterogeneity, e.g., quantitative formulations of coupled ecosystem-climate processes often rely on the specification of key parameters stomatal conductance, rooting depth, or leaf area index which in turn must be estimated through scalesensitive measurements conducted at a limited number of sites. Given this background, our proposed working group (hereafter, WG), comprising experts in tropical climate, biology, ecology, ecohydrology, and climate modeling, is guided by the following overarching question: To what extent does vegetation influence tropical terrestrial precipitation characteristics, including its initiation, frequency, intensity, spatial patterns, and temporal variations? In tackling this question, our WG will review and synthesize the current state of knowledge of vegetation-precipitation coupling. We will discuss how we can formulate, design, and optimize experimental observing systems and diagnostic frameworks to assess such coupling across a range of tropical hydroclimatic environments and ecosystem types: in this regard, we view access to OTS s 3 biological research facilities as especially valuable, not to mention that we can leverage on WG participants existing or planned research efforts in the Amazon and West Africa. Finally, we will address some of the unresolved issues in simulation of vegetation-precipitation coupling spanning a range of model types, from simple process-level models to global climate models, from daily to decadal time scales and site-level to regional or continental spatial scales. Part of this discussion will be directed toward what is needed to truth or validate models: a hoped for outcome is that our WG can suggest how the wealth of data from 50 years of OTS research in tropical biology and ecology can inform the development of next-generation climate models (especially given the efforts by William Michener and others to develop computational infrastructure for cataloging and accessing OTS data). 2. Participants The PI has identified the following WG participants. Participants from OTS-affiliated institutions are denoted with an asterisk (*). Areas of expertise relevant to the WG are indicated. OTS Grant Competition Emerging Frontiers in Tropical Science 3

4 1. Benjamin Lintner* [PI; Rutgers; Assistant Professor; large-scale tropical dynamics, land-atmosphere interactions, and climate modeling 2. Robert Colwell* [U. Connecticut; Professor; biodiversity; biostatistics and informatics; community ecology 3. Paolo D Odorico* [U. Virginia; Professor; paolo@virginia.edu]: vegetation coupling to soil moisture; water stress in plants 4. Ana María Durán-Quesada* [University of Costa Rica; Research Scientist; ana.duranquesada@ucr.ac.cr]: climate variability in Central America 5. Pierre Gentine [Columbia; Assistant Professor; pg2328@columbia.edu]: boundary layer processes, land-atmosphere interactions; remote sensing and data assimilation 6. Marceau Guerin [Columbia; Graduate Student; mg3237@columbia.edu]: vegetation resilience to drought 7. Jung-Eun Lee [Brown; Assistant Professor; leeje@brown.edu]: climate model development; implementation of processes coupling the terrestrial water cycle to ecosystems in global climate models 8. Guido Salvucci* [Boston U.; Professor; gdsalvuc@bu.edu]: soil moisture dynamics and relationships to surface fluxes; groundwater hydrology 9. Abigail Swann* [U. Washington+; Assistant Professor; aswann@u.washington.edu]: biosphere-climate feedbacks and modeling; carbon-climate interactions 10. Maria Uriarte [Columbia; Associate Professor; mu2126@columbia.edu]: tropical forest ecology, cross-scale impacts of climate change on forest biodiversity One member of the WG is a graduate student and 5 (including the PI) are pre-tenure faculty or research scientists. We also note that many in the WG are conducting funded research activities synergistic with the theme of the WG. For example, three of us (Lee, Gentine, and Lintner) were recently awarded funding under the Department of Energy s GoAmazon program to investigate how plant physiological processes, as assessed by state-of-the-art fluorescence and sap flow measurements, influence climate variability and precipitation over Amazonian rainforests, with a particular focus on the physiological control on deep convection triggering along a geographical water stress gradient from the seasonally dry to everwet Amazon. 3. Session activities and expected outcomes A 3-day meeting is envisioned, to take place during either late 2014 or early 2015 at La Selva Biological Station. To open the meeting, the PI will provide a brief overview of the WG, its intended purpose, and expected outcomes. Thereafter, WG participants will each be invited to share 20-minute presentations of their research as it relates to the theme of the WG. During the afternoon of Day 1 and throughout Day 2, the members of the WG will take turns facilitating brainstorming sessions regarding the current state of vegetation-precipitation coupling in the tropics, the outstanding challenges for observing and modeling this coupling, and areas in which we might reasonably expect to make progress. (We will have plenty of white boards!) This exercise is also intended to encourage consideration of cross-cutting proposals that members of the WG could submit to NSF or relevant programs at the National Oceanic and Atmospheric Administration (NOAA), such as the Earth System Science program, or NASA, such as the Research Opportunities in Space and Earth Sciences (ROSES) program. To facilitate the brainstorming, prior to the meeting, participants will be asked to consider the issue of vegetation-precipitation coupling from their own research perspective, and, more importantly, to formulate questions to guide and stimulate discussion during the meeting. The PI will compile OTS Grant Competition Emerging Frontiers in Tropical Science 4

5 the responses and disseminate these to the WG. Also, at some point during the meeting (ideally, following Day 1 discussions), the WG will tour the flux tower and meteorological measurement facilities at La Selva, hopefully in coordination with OTS researchers or staff. Day 3 will consist of outlining a synthesis paper of the WG discussion, including recommendations for how OTS research and facilities can be brought to bear on vegetationprecipitation coupling, e.g., the types of data that would be useful for validating model simulation. WG members will be assigned sections of the paper, which will be written and edited within 3 months of the meeting. We will then share the draft of the WG synthesis paper with the broader OTS community for comment and feedback. The WG will further aim to publish this synthesis paper (or parts thereof) in Eos, the weekly journal of the American Geophysical Union, or a similar community publication. 4. Why should OTS support this WG? During the March 2012 Assembly of Delegates meeting at La Selva, participants were charged with identifying OTS s research priorities in the 21 st century. Recognizing that the climate science community is moving toward ever more complex and comprehensive earth system models (ESMs) models that encompass climate, biology, and human systems the PI and OTS colleagues Rob Colwell, Bette Loiselle, and Elizabeth Losos considered the question of How do we incorporate tropical biology into ESMs? One clear challenge we identified is the need for channels of communication among the various participants in this undertaking biologists, ecologists, and climate scientists, and modelers in order to appreciate one another s needs and current state of knowledge. The proposed WG responds to this challenge by bringing together a diverse group of scientists, including participants outside the traditional research core of OTS. Moreover, we believe this WG will ultimately lead to the broadening of OTS s research and educational capacity. Our WG members possess expertise that OTS can tap for guidance in or development of courses in topics such as tropical climate dynamics, land-atmosphere interactions, hydrometeorology, and ecosystem process modeling. For example, as part of a planned Fall 2014 survey course in climate-ecosystem interactions at Rutgers, the PI will be constructing a course web page with reference materials and readings (and, in future iterations, products from our WG). During the WG meeting, we invite all OTS researchers, especially students, who may be present to join us for stimulating lunch, dinner, and late night conversations! This WG also capitalizes on the opportunity to engage with colleagues at the U. of Costa Rica (UCR). In November 2013, the PI hosted a 5-day visit to Rutgers by Dr. Ana María Durán- Quesada of the School of Physics at UCR. During this time, we identified several areas of need (and intellectual interest) for climate research in Costa Rica, including in situ measurement of soil moisture, vegetation phenology, and vertical atmospheric profiles. Apart from building the foundation for understanding climate system processes affecting Costa Rica, these areas are clearly relevant to the WG. One possibility that was discussed and which could readily lead to funded research with US-based collaborators involves UCR s plans to deploy a flux tower and meteorological instrumentation in the southeast of Costa Rica. 5. Management of participant information, evaluation and assessment, and final report The PI will collect participant demographics and evaluation and assessment questionnaires. The PI will prepare and submit a report of the WG within two weeks of the meeting. OTS Grant Competition Emerging Frontiers in Tropical Science 5

6 IV. PROJECT BUDGET The timeframe for the WG is late 2014 or early 2015, with precise dates to be determined subject to participant availability. The proposed 3-day meeting (with two additional days for travel to/from the US) will take place at La Selva Biological Station. Airfare for US-based participants is likely to be based on travel from the following cities/regions: Northern New Jersey/New York/Connecticut (5 participants); Providence/Boston (2 participants); Charlottesville, VA (1 participant); and Seattle (1 participant). OTS Grant Competition Emerging Frontiers in Tropical Science 6