\documentclass[10pt]{article}

\usepackage{fullpage}
\usepackage{setspace}
\usepackage{parskip}
\usepackage{titlesec}
\usepackage[section]{placeins}
\usepackage{xcolor}
\usepackage{breakcites}
\usepackage{lineno}
\usepackage{hyphenat}





\PassOptionsToPackage{hyphens}{url}
\usepackage[colorlinks = true,
            linkcolor = blue,
            urlcolor  = blue,
            citecolor = blue,
            anchorcolor = blue]{hyperref}
\usepackage{etoolbox}
\makeatletter
\patchcmd\@combinedblfloats{\box\@outputbox}{\unvbox\@outputbox}{}{%
  \errmessage{\noexpand\@combinedblfloats could not be patched}%
}%
\makeatother


\usepackage{natbib}




\renewenvironment{abstract}
  {{\bfseries\noindent{\abstractname}\par\nobreak}\footnotesize}
  {\bigskip}

\titlespacing{\section}{0pt}{*3}{*1}
\titlespacing{\subsection}{0pt}{*2}{*0.5}
\titlespacing{\subsubsection}{0pt}{*1.5}{0pt}


\usepackage{authblk}


\usepackage{graphicx}
\usepackage[space]{grffile}
\usepackage{latexsym}
\usepackage{textcomp}
\usepackage{longtable}
\usepackage{tabulary}
\usepackage{booktabs,array,multirow}
\usepackage{amsfonts,amsmath,amssymb}
\providecommand\citet{\cite}
\providecommand\citep{\cite}
\providecommand\citealt{\cite}
% You can conditionalize code for latexml or normal latex using this.
\newif\iflatexml\latexmlfalse
\providecommand{\tightlist}{\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}%

\AtBeginDocument{\DeclareGraphicsExtensions{.pdf,.PDF,.eps,.EPS,.png,.PNG,.tif,.TIF,.jpg,.JPG,.jpeg,.JPEG}}

\usepackage[utf8]{inputenc}
\usepackage[english]{babel}



\usepackage{float}








\begin{document}

\title{NASA GEOS Composition Forecast Modeling System GEOS-CF v1.0:
Stratospheric composition}



\author[1]{K. Emma Knowland}%
\author[1]{Christoph A. Keller}%
\author[2]{Pamela A Wales}%
\author[3]{Krzysztof Wargan}%
\author[4]{Lawrence Coy}%
\author[5]{Matthew S Johnson}%
\author[1]{Junhua Liu}%
\author[6]{Robert A Lucchesi}%
\author[7]{Sebastian David Eastham}%
\author[8]{Eric L. Fleming}%
\author[9]{Qing Liang}%
\author[10]{Thierry Leblanc}%
\author[10]{Nathaniel J Livesey}%
\author[11]{Kaley A. Walker}%
\author[12]{Lesley E. Ott}%
\author[12]{Steven Pawson}%
\affil[1]{Universities Space Research Association}%
\affil[2]{University of Maryland, College Park}%
\affil[3]{Science Systems and Applications, Inc.}%
\affil[4]{SSAI}%
\affil[5]{NASA Ames Research Center}%
\affil[6]{Science Systems and Applications, Inc}%
\affil[7]{Massachusetts Institute of Technology}%
\affil[8]{NASA/Goddard Space Flight Center, Science Systems and Applications, Inc.}%
\affil[9]{NASA GSFC}%
\affil[10]{Jet Propulsion Laboratory}%
\affil[11]{University of Toronto}%
\affil[12]{NASA Goddard Space Flight Center}%


\vspace{-1em}



  
  \date{May 25, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
The NASA Goddard Earth Observing System (GEOS) Composition Forecast
(GEOS-CF) provides recent estimates and five-day forecasts of
atmospheric composition to the public in near-real time. To do this, the
GEOS Earth system model is coupled with the GEOS-Chem
tropospheric-stratospheric unified chemistry extension (UCX) to
represent composition from the surface to the top of the GEOS atmosphere
(0.01 hPa). The GEOS-CF system is described, including updates made to
the GEOS-Chem UCX mechanism within GEOS-CF for improved representation
of stratospheric chemistry. Comparisons are made against balloon, lidar
and satellite observations for stratospheric composition, including
measurements of ozone (O\textsubscript{3}) and important nitrogen and
chlorine species related to stratospheric O\textsubscript{3} recovery.
The GEOS-CF nudges the stratospheric O\textsubscript{3} towards the GEOS
Forward Processing (GEOS FP) assimilated O3 product; as a result the
stratospheric O\textsubscript{3} in the GEOS-CF historical estimate
agrees well with observations. During abnormal dynamical and chemical
environments such as the 2020 polar vortexes, the GEOS-CF
O\textsubscript{3} forecasts are more realistic than GEOS FP
O\textsubscript{3} forecasts because of the inclusion of the complex
GEOS-Chem UCX chemistry. Overall, the spatial pattern of the GEOS-CF
simulated concentrations of stratospheric composition agrees well with
satellite observations. However, there are notable biases -- such as low
NO\textsubscript{x} and HNO\textsubscript{3} in the polar regions and
generally low HCl throughout the stratosphere -- and future improvements
to the chemistry mechanism and emissions are discussed. GEOS-CF is a new
tool for the research community and instrument teams observing trace
gases in the stratosphere and troposphere, providing near-real-time
three-dimensional gridded information on atmospheric composition.%
\end{abstract}%



\sloppy




\selectlanguage{english}
\FloatBarrier
\end{document}

