VOCALS-Regional Experiment VOCALS-REx EXPERIMENTAL (VOCALS-REx) EXPERIMENTAL DESIGN OVERVIEW Robert

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  • VOCALS-Regional Experiment

    (VOCALS-REx)

    EXPERIMENTAL DESIGN OVERVIEW

    Robert Wood (University of Washington) and the VOCALS Scientific Working Group

    Contributions from Christopher Bretherton (University of Washington), Chris Fairall (NOAA ETL), Laura Gallardo Klenner (Universidad de Chile), Steve Esbensen (Oregon State University), Graham Feingold (NOAA ETL), Rene Garreaud (Universidad de Chile), Barry Huebert (University of Hawaii), Dave Leon (University of Wyoming), C.

    Roberto Mechoso (UCLA), Jim McWilliams (UCLA), Art Miller (Scripps Institution of Oceanography), Oscar Pizarro (Universidad de Concepcion, Chile), Jose Rutllant (Universidad de Chile), Jefferson Snider (University of

    Wyoming), Ken Takahashi (IGP, Lima and University of Washington), Robert Weller (WHOI), Hemantha Wijesekera (Oregon State University), Sandra Yuter (North Carolina State University), Sarah Doherty (University of

    Washington, IGAC)

    January 2006

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    Table of Contents

    EXECUTIVE SUMMARY .......................................................................................................... 3

    PROGRAM RATIONALE, HYPOTHESES, AND OBJECTIVES........................................ 5

    EXPERIMENTAL DESIGN AND OBSERVATIONAL REQUIREMENTS........................ 7

    VOCALS-REX STUDY REGION AND DATES ...............................................................................................................7 PLATFORMS AND INSTRUMENTATION.........................................................................................................................8

    C-130 Instruments.................................................................................................................................................8 NOAA R/V Ronald H Brown instruments............................................................................................................10 NOAA P3 Instruments.........................................................................................................................................13 Chilean coastal component platforms and instrumentation................................................................................14 Peruvian coastal component platforms and instrumentation..............................................................................14

    PLATFORM DEPLOYMENT AND SAMPLING STRATEGY ...............................................................................................15 C-130 sampling strategy .....................................................................................................................................15 RHB deployment strategy ...................................................................................................................................21 NOAA P3 sampling strategy ...............................................................................................................................22 VOCALS-REx Coastal component sampling ......................................................................................................22

    PROJECT MANAGEMENT INCLUDING MANAGEMENT IN THE FIELD................. 25

    DATA MANAGEMENT PLAN ................................................................................................ 26

    SECTION I OF THE SPO ......................................................................................................... 27

    SECTION J OF THE SPO......................................................................................................... 33

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    Executive Summary

    The VAMOS Ocean-Cloud-Atmosphere-Land Study - Regional Experiment (VOCALS-REx) is an international field experiment designed to better understand physical and chemical processes central to the climate system of the Southeast Pacific (SEP) region. The climate of the SEP region is a tightly coupled system involving poorly understood interactions between the ocean, the atmosphere, and the land (Fig. 1) VOCALS-REx will focus on interactions between clouds, aerosols, marine boundary layer (MBL) processes, upper ocean dynamics and thermodynamics, coastal currents and upwelling, large-scale subsidence, and regional diurnal circulations, to the west of the Andes mountain range. The field experiment is ultimately driven by a need for improved model simulations of the coupled climate system in both the SEP and over the wider tropics and subtropics.

    Figure 1: Key features and processes in the Southeast Pacific climate system.

    VOCALS-REx will provide detailed and targeted observations of those processes that impact the SEP climate system and are amenable to study with a month long program. The intensive field observations are a vital component of the broader VOCALS program and have been carefully designed to complement a suite of enhanced long-term observations. The long-term observations provide important context for the intensive observations. In addition, a major thrust of the VOCALS program is to provide coordination for modeling activities, which will benefit from the intensive observations in a poorly observed region where coupled ocean-atmosphere models exhibit strong biases in sea surface temperature. The coordination through VOCALS of observational and modeling efforts will lead to an improved pull-through for climate and regional forecasting agencies.

    Multi-disciplinary intensive observational datasets will be obtained during VOCALS-REx from several platforms including aircraft, research vessels, and a surface land site. These datasets will be used

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    to test a coordinated set of hypotheses that are organized into two broad themes: (1) improved understanding of aerosol-cloud-drizzle interactions in the marine boundary layer (MBL) and the physicochemical and spatiotemporal properties of aerosols; (2) improved understanding of the chemical and physical couplings between the upper ocean, the land, and the atmosphere. The intensive observational period will be a month long and will take place during October 2007, chosen because it is the month during which the coverage of stratocumulus over the SEP is at its greatest, the southeast trade winds are at their strongest, and the coupling between the upper ocean and the lower atmosphere is at its tightest.

    Intellectual merits:

    The proposed work involves making state of the art field measurements of the atmosphere and ocean in a climate regime that is poorly explored but that has important consequences for the regional and global climate system. Few previous observational programs have been designed with such a strong multidisciplinary focus, and the simultaneous and collocated ocean and atmosphere dataset will allow an unprecedented examination of how mesoscale ocean variability impacts the chemical and aerosol properties of the lower atmosphere. These measurements will have a broad impact upon current knowledge in the fields of atmospheric science and oceanography which will ultimately lead to improved predictions of future climate.

    Broader impacts:

    The field and subsequent analysis phases will involve and foster considerable international collaboration and provide important training for a number of scientists and graduate students. The datasets generated in the field will stimulate the development of a broad range of numerical process models, and provide invaluable constraints that will accelerate the improvement of regional and global climate models.

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    Program Rationale, Hypotheses, and Objectives

    A justification of the key scientific issues and a complete description of the objectives of VOCALS- REx are presented in the Scientific Program Overview (SPO) document. Here, we present a concise description of the scientific issues and hypotheses that will be tested with datasets obtained during the field program.

    The climate of the SEP is dependent upon important interactions and feedbacks between the upper ocean, the Andes mountains, and the lower troposphere. Marine boundary layer (MBL) clouds, which swathe a large fraction of the SEP, are essential for driving strong trade winds and producing the observed SST distribution. The Andes mountains increase the lower tropospheric static stability over the SEP, enhancing the cloud cover and encourage the formation of a near-coastal jet in the MBL that enhances the oceanic upwelling of cold, nutrient-rich water. The mountains also drive a stronger subtropical gyre which increases the evaporative cooling of the surface and further reduces SST. The coastal upwelling associated with the Humboldt Current system is not only important in the coastal zone, but also impacts the SST much further offshore through ocean transport processes that include mesoscale eddy transport. The climate of the SEP region is therefore a tightly coupled system involving interactions between

    the ocean, the atmosphere, and the land. The SEP climate system is unique in that its ocean current system is the only eastern boundary current directly connected with the tropical ocean and so is subject to strong ENSO variability. The SEP climate system is poorly explored observationally, yet our ability to make accurate predictions of the broader tropical climate is strongly sensitive to its representation in numerical models. These models, especially those which couple the ocean and atmosphere, exhibit strong biases in the SEP that stem directly from poorly represented processes occurring on scales smaller than the model resolution.

    Cloud optical properties over the SEP are influenced by