Carbon, oxygen, and sulfur chemistry on venus in three dimensions: time, altitude, and latitude the goal of the proposed research is to understand quantitatively the combined effects of atmospheric…

This federal contract award, valued at $305,055.00, was granted by the National Aeronautics and Space Administration (NASA) to the Space Science Institute (SSI), a nonprofit research organization based in Boulder, Colorado. The award supports a three-year research project aimed at understanding the combined effects of atmospheric chemistry and transport on Venus. The goal is to develop a quantitative understanding of how global-scale transport impacts the chemistry in Venus' upper troposphere and lower mesosphere, and how this coupling is expressed in the planet's sulfur cycle. The project will leverage state-of-the-art atmospheric general circulation models and a fully interactive two-dimensional chemical transport model to simulate temporal variations in Venus' atmospheric chemistry and dynamics. This research aligns with NASA's Solar System Workings program objectives to characterize planetary atmospheres and understand the chemical processes that control their evolution. The contract does not have a set-aside designation, as SSI competes for awards based on scientific and technical merit.

Carbon, oxygen, and sulfur chemistry on venus in three dimensions: time, altitude, and latitude the goal of the proposed research is to understand quantitatively the combined effects of atmospheric chemistry and transport on venus. At its conclusion, we will have achieved a quantitative understanding of the impact of global-scale transport on the chemistry in the upper troposphere and lower mesosphere, characterized how their coupled effects result in the observed tropospheric distributions of CO and OCS, and determined how this global-scale coupling is expressed in the sulfur cycle. Most previous efforts to address these questions used models that were limited: either one spatial dimension (1D) with interactive chemistry [e.g., krasnopolsky 2013] or two spatial dimensions (2D) without interactive chemistry only one prior study, which we conducted using a simplified 2D model [yung ET AL 2009], looked at the 2D interaction of chemistry and transport. No study to date has looked at temporal variations of this 2D interaction in the upper troposphere and lower mesosphere. Not surprisingly, quantitative agreement between model results and observations has not been achieved, as we showed [cotton ET AL 2012]. We propose to revisit the 2D interaction of chemistry and transport with significantly enhanced models and new observations. We will extract wind fields from three state-of-the-art atmospheric general circulation models (agcms) that have differing strengths/ weaknesses and unique approaches. All have been upgraded significantly since our 2009 study, and preliminary results with the upgraded agcms raise the prospects of significant revisions in our understanding of the vertical structure of the troposphere, the maintenance of the cloud-top superrotation, and episodic variations in circulation. Use of multiple agcms will help US quantify the uncertainties and sensitivities of the wind fields. We will use the method of jiang ET AL [2004] to transform the 3D meridional circulation from the agcms into 2D wind fields for use in our enhanced, fullyinteractive 2D chemical transport model (CTM). Global circulation will be extracted from the agcm simulations at multiple epochs, simulating temporal variations in global circulation. Based on the improvements in our agcms and CTM, we expect significantly greater accuracy in our simulations of the coupled effects of transport and chemistry, temporal variations in these coupled effects, and their uncertainties. Enabling and supporting the proposed research are significant advances we have made (a) simulating the interaction between condensed and gaseous phases, (b) understanding mesospheric chemistry, (c) identifying the potential for bifurcation in the SO2-H2O-sulfuric acid cloud system, and (d) quantifying the sensitivity of CO observations to its vertical distribution. The proposed research links these theoretical and observational efforts in an iterative manner that has not previously been done. Achieving a detailed understanding of venus' current atmospheric chemistry and transport will (a) enable more accurate simulations of venus' evolution, past and future, and (b) improve interpretation of chemical signatures detected in venus-class extrasolar planets in terms of their physical and chemical state and planetary habitability. The proposed three year project addresses key objectives of the solar system workings (SSW) program, notably "characterize the chemical composition of planetary atmospheres" and "understand the ... Chemical processes that control the stability of, the losses from, and the evolution of planetary atmospheres" [SEC. C.3.1 of roses--2015]. Thus, the proposed research is relevant to NASA and the SSW program element. The proposal team has extensive experience in venus atmospheric chemistry, dynamics, radiative transfer, and observations.