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  • Author or Editor: P. S. K. Liu x
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I. Gultepe
,
T. Kuhn
,
M. Pavolonis
,
C. Calvert
,
J. Gurka
,
A. J. Heymsfield
,
P. S. K. Liu
,
B. Zhou
,
R. Ware
,
B. Ferrier
,
J. Milbrandt
, and
B. Bernstein

Ice fog and frost occur commonly (at least 26% of the time) in the northern latitudes and Arctic regions during winter at temperatures usually less than about –15°C. Ice fog is strongly related to frost formation—a major aviation hazard in the northern latitudes. In fact, it may be considered a more dangerous event than snow because of the stronger aircraft surface adhesion compared to snow particles. In the winter of 2010/11, the Fog Remote Sensing and Modeling–Ice Fog (FRAM-IF) project was organized near Yellowknife International Airport, Northwest Territories, Canada, with the main goals of advancing understanding of ice fog microphysical and visibility characteristics, and improving its prediction using forecast models and remotesensing retrievals. Approximately 40 different sensors were used to measure visibility, precipitation, ice particle spectra, vertical thermodynamic profiles, and ceiling height. Fog coverage and visibility parameters were estimated using both Geostationary Operational Environmental Satellites (GOES) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations. During this project, the inversion layer usually was below a height of 1.5 km. High humidity typically was close to the ground, frequently producing ice fog, frost, and light snow precipitation. At low temperatures, snow crystals can be swept away by a very low wind speed (∼1 m s−1). Ice fog during the project was not predicted by any forecast model. These preliminary results in the northern latitudes suggest that ice fog and frost studies, over the Arctic regions, can help us to better understand ice microphysical processes such as ice nucleation, visibility, and parameterizations of ice fog.

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R. A Anthes
,
P. A Bernhardt
,
Y. Chen
,
L. Cucurull
,
K. F. Dymond
,
D. Ector
,
S. B. Healy
,
S.-P. Ho
,
D. C Hunt
,
Y.-H. Kuo
,
H. Liu
,
K. Manning
,
C. McCormick
,
T. K. Meehan
,
W J. Randel
,
C. Rocken
,
W S. Schreiner
,
S. V. Sokolovskiy
,
S. Syndergaard
,
D. C. Thompson
,
K. E. Trenberth
,
T.-K. Wee
,
N. L. Yen
, and
Z Zeng

The radio occultation (RO) technique, which makes use of radio signals transmitted by the global positioning system (GPS) satellites, has emerged as a powerful and relatively inexpensive approach for sounding the global atmosphere with high precision, accuracy, and vertical resolution in all weather and over both land and ocean. On 15 April 2006, the joint Taiwan-U.S. Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)/Formosa Satellite Mission 3 (COSMIC/FORMOSAT-3, hereafter COSMIC) mission, a constellation of six microsatellites, was launched into a 512-km orbit. After launch the satellites were gradually deployed to their final orbits at 800 km, a process that took about 17 months. During the early weeks of the deployment, the satellites were spaced closely, offering a unique opportunity to verify the high precision of RO measurements. As of September 2007, COSMIC is providing about 2000 RO soundings per day to support the research and operational communities. COSMIC RO data are of better quality than those from the previous missions and penetrate much farther down into the troposphere; 70%–90% of the soundings reach to within 1 km of the surface on a global basis. The data are having a positive impact on operational global weather forecast models.

With the ability to penetrate deep into the lower troposphere using an advanced open-loop tracking technique, the COSMIC RO instruments can observe the structure of the tropical atmospheric boundary layer. The value of RO for climate monitoring and research is demonstrated by the precise and consistent observations between different instruments, platforms, and missions. COSMIC observations are capable of intercalibrating microwave measurements from the Advanced Microwave Sounding Unit (AMSU) on different satellites. Finally, unique and useful observations of the ionosphere are being obtained using the RO receiver and two other instruments on the COSMIC satellites, the tiny ionosphere photometer (TIP) and the tri-band beacon.

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J.-P. Vernier
,
T. D. Fairlie
,
T. Deshler
,
M. Venkat Ratnam
,
H. Gadhavi
,
B. S. Kumar
,
M. Natarajan
,
A. K. Pandit
,
S. T. Akhil Raj
,
A. Hemanth Kumar
,
A. Jayaraman
,
A. K. Singh
,
N. Rastogi
,
P. R. Sinha
,
S. Kumar
,
S. Tiwari
,
T. Wegner
,
N. Baker
,
D. Vignelles
,
G. Stenchikov
,
I. Shevchenko
,
J. Smith
,
K. Bedka
,
A. Kesarkar
,
V. Singh
,
J. Bhate
,
V. Ravikiran
,
M. Durga Rao
,
S. Ravindrababu
,
A. Patel
,
H. Vernier
,
F. G. Wienhold
,
H. Liu
,
T. N. Knepp
,
L. Thomason
,
J. Crawford
,
L. Ziemba
,
J. Moore
,
S. Crumeyrolle
,
M. Williamson
,
G. Berthet
,
F. Jégou
, and
J.-B. Renard

Abstract

We describe and show results from a series of field campaigns that used balloonborne instruments launched from India and Saudi Arabia during the summers 2014–17 to study the nature, formation, and impacts of the Asian Tropopause Aerosol Layer (ATAL). The campaign goals were to i) characterize the optical, physical, and chemical properties of the ATAL; ii) assess its impacts on water vapor and ozone; and iii) understand the role of convection in its formation. To address these objectives, we launched 68 balloons from four locations, one in Saudi Arabia and three in India, with payload weights ranging from 1.5 to 50 kg. We measured meteorological parameters; ozone; water vapor; and aerosol backscatter, concentration, volatility, and composition in the upper troposphere and lower stratosphere (UTLS) region. We found peaks in aerosol concentrations of up to 25 cm–3 for radii > 94 nm, associated with a scattering ratio at 940 nm of ∼1.9 near the cold-point tropopause. During medium-duration balloon flights near the tropopause, we collected aerosols and found, after offline ion chromatography analysis, the dominant presence of nitrate ions with a concentration of about 100 ng m–3. Deep convection was found to influence aerosol loadings 1 km above the cold-point tropopause. The Balloon Measurements of the Asian Tropopause Aerosol Layer (BATAL) project will continue for the next 3–4 years, and the results gathered will be used to formulate a future National Aeronautics and Space Administration–Indian Space Research Organisation (NASA–ISRO) airborne campaign with NASA high-altitude aircraft.

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D. A. Knopf
,
K. R. Barry
,
T. A. Brubaker
,
L. G. Jahl
,
K. A. Jankowski
,
J. Li
,
Y. Lu
,
L. W. Monroe
,
K. A. Moore
,
F. A. Rivera-Adorno
,
K. A. Sauceda
,
Y. Shi
,
J. M. Tomlin
,
H. S. K. Vepuri
,
P. Wang
,
N. N. Lata
,
E. J. T. Levin
,
J. M. Creamean
,
T. C. J. Hill
,
S. China
,
P. A. Alpert
,
R. C. Moffet
,
N. Hiranuma
,
R. C. Sullivan
,
A. M. Fridlind
,
M. West
,
N. Riemer
,
A. Laskin
,
P. J. DeMott
, and
X. Liu

Abstract

Prediction of ice formation in clouds presents one of the grand challenges in the atmospheric sciences. Immersion freezing initiated by ice-nucleating particles (INPs) is the dominant pathway of primary ice crystal formation in mixed-phase clouds, where supercooled water droplets and ice crystals coexist, with important implications for the hydrological cycle and climate. However, derivation of INP number concentrations from an ambient aerosol population in cloud-resolving and climate models remains highly uncertain. We conducted an aerosol–ice formation closure pilot study using a field-observational approach to evaluate the predictive capability of immersion freezing INPs. The closure study relies on collocated measurements of the ambient size-resolved and single-particle composition and INP number concentrations. The acquired particle data serve as input in several immersion freezing parameterizations, which are employed in cloud-resolving and climate models, for prediction of INP number concentrations. We discuss in detail one closure case study in which a front passed through the measurement site, resulting in a change of ambient particle and INP populations. We achieved closure in some circumstances within uncertainties, but we emphasize the need for freezing parameterization of potentially missing INP types and evaluation of the choice of parameterization to be employed. Overall, this closure pilot study aims to assess the level of parameter details and measurement strategies needed to achieve aerosol–ice formation closure. The closure approach is designed to accurately guide immersion freezing schemes in models, and ultimately identify the leading causes for climate model bias in INP predictions.

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C. L. Reddington
,
K. S. Carslaw
,
P. Stier
,
N. Schutgens
,
H. Coe
,
D. Liu
,
J. Allan
,
J. Browse
,
K. J. Pringle
,
L. A. Lee
,
M. Yoshioka
,
J. S. Johnson
,
L. A. Regayre
,
D. V. Spracklen
,
G. W. Mann
,
A. Clarke
,
M. Hermann
,
S. Henning
,
H. Wex
,
T. B. Kristensen
,
W. R. Leaitch
,
U. Pöschl
,
D. Rose
,
M. O. Andreae
,
J. Schmale
,
Y. Kondo
,
N. Oshima
,
J. P. Schwarz
,
A. Nenes
,
B. Anderson
,
G. C. Roberts
,
J. R. Snider
,
C. Leck
,
P. K. Quinn
,
X. Chi
,
A. Ding
,
J. L. Jimenez
, and
Q. Zhang

Abstract

The largest uncertainty in the historical radiative forcing of climate is caused by changes in aerosol particles due to anthropogenic activity. Sophisticated aerosol microphysics processes have been included in many climate models in an effort to reduce the uncertainty. However, the models are very challenging to evaluate and constrain because they require extensive in situ measurements of the particle size distribution, number concentration, and chemical composition that are not available from global satellite observations. The Global Aerosol Synthesis and Science Project (GASSP) aims to improve the robustness of global aerosol models by combining new methodologies for quantifying model uncertainty, to create an extensive global dataset of aerosol in situ microphysical and chemical measurements, and to develop new ways to assess the uncertainty associated with comparing sparse point measurements with low-resolution models. GASSP has assembled over 45,000 hours of measurements from ships and aircraft as well as data from over 350 ground stations. The measurements have been harmonized into a standardized format that is easily used by modelers and nonspecialist users. Available measurements are extensive, but they are biased to polluted regions of the Northern Hemisphere, leaving large pristine regions and many continental areas poorly sampled. The aerosol radiative forcing uncertainty can be reduced using a rigorous model–data synthesis approach. Nevertheless, our research highlights significant remaining challenges because of the difficulty of constraining many interwoven model uncertainties simultaneously. Although the physical realism of global aerosol models still needs to be improved, the uncertainty in aerosol radiative forcing will be reduced most effectively by systematically and rigorously constraining the models using extensive syntheses of measurements.

Open access
Bruce A. Wielicki
,
D. F. Young
,
M. G. Mlynczak
,
K. J. Thome
,
S. Leroy
,
J. Corliss
,
J. G. Anderson
,
C. O. Ao
,
R. Bantges
,
F. Best
,
K. Bowman
,
H. Brindley
,
J. J. Butler
,
W. Collins
,
J. A. Dykema
,
D. R. Doelling
,
D. R. Feldman
,
N. Fox
,
X. Huang
,
R. Holz
,
Y. Huang
,
Z. Jin
,
D. Jennings
,
D. G. Johnson
,
K. Jucks
,
S. Kato
,
D. B. Kirk-Davidoff
,
R. Knuteson
,
G. Kopp
,
D. P. Kratz
,
X. Liu
,
C. Lukashin
,
A. J. Mannucci
,
N. Phojanamongkolkij
,
P. Pilewskie
,
V. Ramaswamy
,
H. Revercomb
,
J. Rice
,
Y. Roberts
,
C. M. Roithmayr
,
F. Rose
,
S. Sandford
,
E. L. Shirley
,
Sr. W. L. Smith
,
B. Soden
,
P. W. Speth
,
W. Sun
,
P. C. Taylor
,
D. Tobin
, and
X. Xiong

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5–50 μm), the spectrum of solar radiation reflected by the Earth and its atmosphere (320–2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a “NIST [National Institute of Standards and Technology] in orbit.” CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

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L. L. Pan
,
E. L. Atlas
,
R. J. Salawitch
,
S. B. Honomichl
,
J. F. Bresch
,
W. J. Randel
,
E. C. Apel
,
R. S. Hornbrook
,
A. J. Weinheimer
,
D. C. Anderson
,
S. J. Andrews
,
S. Baidar
,
S. P. Beaton
,
T. L. Campos
,
L. J. Carpenter
,
D. Chen
,
B. Dix
,
V. Donets
,
S. R. Hall
,
T. F. Hanisco
,
C. R. Homeyer
,
L. G. Huey
,
J. B. Jensen
,
L. Kaser
,
D. E. Kinnison
,
T. K. Koenig
,
J.-F. Lamarque
,
C. Liu
,
J. Luo
,
Z. J. Luo
,
D. D. Montzka
,
J. M. Nicely
,
R. B. Pierce
,
D. D. Riemer
,
T. Robinson
,
P. Romashkin
,
A. Saiz-Lopez
,
S. Schauffler
,
O. Shieh
,
M. H. Stell
,
K. Ullmann
,
G. Vaughan
,
R. Volkamer
, and
G. Wolfe

Abstract

The Convective Transport of Active Species in the Tropics (CONTRAST) experiment was conducted from Guam (13.5°N, 144.8°E) during January–February 2014. Using the NSF/NCAR Gulfstream V research aircraft, the experiment investigated the photochemical environment over the tropical western Pacific (TWP) warm pool, a region of massive deep convection and the major pathway for air to enter the stratosphere during Northern Hemisphere (NH) winter. The new observations provide a wealth of information for quantifying the influence of convection on the vertical distributions of active species. The airborne in situ measurements up to 15-km altitude fill a significant gap by characterizing the abundance and altitude variation of a wide suite of trace gases. These measurements, together with observations of dynamical and microphysical parameters, provide significant new data for constraining and evaluating global chemistry–climate models. Measurements include precursor and product gas species of reactive halogen compounds that impact ozone in the upper troposphere/lower stratosphere. High-accuracy, in situ measurements of ozone obtained during CONTRAST quantify ozone concentration profiles in the upper troposphere, where previous observations from balloonborne ozonesondes were often near or below the limit of detection. CONTRAST was one of the three coordinated experiments to observe the TWP during January–February 2014. Together, CONTRAST, Airborne Tropical Tropopause Experiment (ATTREX), and Coordinated Airborne Studies in the Tropics (CAST), using complementary capabilities of the three aircraft platforms as well as ground-based instrumentation, provide a comprehensive quantification of the regional distribution and vertical structure of natural and pollutant trace gases in the TWP during NH winter, from the oceanic boundary to the lower stratosphere.

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Gerhard Theurich
,
C. DeLuca
,
T. Campbell
,
F. Liu
,
K. Saint
,
M. Vertenstein
,
J. Chen
,
R. Oehmke
,
J. Doyle
,
T. Whitcomb
,
A. Wallcraft
,
M. Iredell
,
T. Black
,
A. M. Da Silva
,
T. Clune
,
R. Ferraro
,
P. Li
,
M. Kelley
,
I. Aleinov
,
V. Balaji
,
N. Zadeh
,
R. Jacob
,
B. Kirtman
,
F. Giraldo
,
D. McCarren
,
S. Sandgathe
,
S. Peckham
, and
R. Dunlap IV

Abstract

The Earth System Prediction Suite (ESPS) is a collection of flagship U.S. weather and climate models and model components that are being instrumented to conform to interoperability conventions, documented to follow metadata standards, and made available either under open-source terms or to credentialed users.

The ESPS represents a culmination of efforts to create a common Earth system model architecture, and the advent of increasingly coordinated model development activities in the United States. ESPS component interfaces are based on the Earth System Modeling Framework (ESMF), community-developed software for building and coupling models, and the National Unified Operational Prediction Capability (NUOPC) Layer, a set of ESMF-based component templates and interoperability conventions. This shared infrastructure simplifies the process of model coupling by guaranteeing that components conform to a set of technical and semantic behaviors. The ESPS encourages distributed, multiagency development of coupled modeling systems; controlled experimentation and testing; and exploration of novel model configurations, such as those motivated by research involving managed and interactive ensembles. ESPS codes include the Navy Global Environmental Model (NAVGEM), the Hybrid Coordinate Ocean Model (HYCOM), and the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS); the NOAA Environmental Modeling System (NEMS) and the Modular Ocean Model (MOM); the Community Earth System Model (CESM); and the NASA ModelE climate model and the Goddard Earth Observing System Model, version 5 (GEOS-5), atmospheric general circulation model.

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J. Fishman
,
L. T. Iraci
,
J. Al-Saadi
,
K. Chance
,
F. Chavez
,
M. Chin
,
P. Coble
,
C. Davis
,
P. M. DiGiacomo
,
D. Edwards
,
A. Eldering
,
J. Goes
,
J. Herman
,
C. Hu
,
D. J. Jacob
,
C. Jordan
,
S. R. Kawa
,
R. Key
,
X. Liu
,
S. Lohrenz
,
A. Mannino
,
V. Natraj
,
D. Neil
,
J. Neu
,
M. Newchurch
,
K. Pickering
,
J. Salisbury
,
H. Sosik
,
A. Subramaniam
,
M. Tzortziou
,
J. Wang
, and
M. Wang

The Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission was recommended by the National Research Council's (NRC's) Earth Science Decadal Survey to measure tropospheric trace gases and aerosols and coastal ocean phytoplankton, water quality, and biogeochemistry from geostationary orbit, providing continuous observations within the field of view. To fulfill the mandate and address the challenge put forth by the NRC, two GEO-CAPE Science Working Groups (SWGs), representing the atmospheric composition and ocean color disciplines, have developed realistic science objectives using input drawn from several community workshops. The GEO-CAPE mission will take advantage of this revolutionary advance in temporal frequency for both of these disciplines. Multiple observations per day are required to explore the physical, chemical, and dynamical processes that determine tropospheric composition and air quality over spatial scales ranging from urban to continental, and over temporal scales ranging from diurnal to seasonal. Likewise, high-frequency satellite observations are critical to studying and quantifying biological, chemical, and physical processes within the coastal ocean. These observations are to be achieved from a vantage point near 95°–100°W, providing a complete view of North America as well as the adjacent oceans. The SWGs have also endorsed the concept of phased implementation using commercial satellites to reduce mission risk and cost. GEO-CAPE will join the global constellation of geostationary atmospheric chemistry and coastal ocean color sensors planned to be in orbit in the 2020 time frame.

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H. J. S. Fernando
,
E. R. Pardyjak
,
S. Di Sabatino
,
F. K. Chow
,
S. F. J. De Wekker
,
S. W. Hoch
,
J. Hacker
,
J. C. Pace
,
T. Pratt
,
Z. Pu
,
W. J. Steenburgh
,
C. D. Whiteman
,
Y. Wang
,
D. Zajic
,
B. Balsley
,
R. Dimitrova
,
G. D. Emmitt
,
C. W. Higgins
,
J. C. R. Hunt
,
J. C. Knievel
,
D. Lawrence
,
Y. Liu
,
D. F. Nadeau
,
E. Kit
,
B. W. Blomquist
,
P. Conry
,
R. S. Coppersmith
,
E. Creegan
,
M. Felton
,
A. Grachev
,
N. Gunawardena
,
C. Hang
,
C. M. Hocut
,
G. Huynh
,
M. E. Jeglum
,
D. Jensen
,
V. Kulandaivelu
,
M. Lehner
,
L. S. Leo
,
D. Liberzon
,
J. D. Massey
,
K. McEnerney
,
S. Pal
,
T. Price
,
M. Sghiatti
,
Z. Silver
,
M. Thompson
,
H. Zhang
, and
T. Zsedrovits

Abstract

Emerging application areas such as air pollution in megacities, wind energy, urban security, and operation of unmanned aerial vehicles have intensified scientific and societal interest in mountain meteorology. To address scientific needs and help improve the prediction of mountain weather, the U.S. Department of Defense has funded a research effort—the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program—that draws the expertise of a multidisciplinary, multi-institutional, and multinational group of researchers. The program has four principal thrusts, encompassing modeling, experimental, technology, and parameterization components, directed at diagnosing model deficiencies and critical knowledge gaps, conducting experimental studies, and developing tools for model improvements. The access to the Granite Mountain Atmospheric Sciences Testbed of the U.S. Army Dugway Proving Ground, as well as to a suite of conventional and novel high-end airborne and surface measurement platforms, has provided an unprecedented opportunity to investigate phenomena of time scales from a few seconds to a few days, covering spatial extents of tens of kilometers down to millimeters. This article provides an overview of the MATERHORN and a glimpse at its initial findings. Orographic forcing creates a multitude of time-dependent submesoscale phenomena that contribute to the variability of mountain weather at mesoscale. The nexus of predictions by mesoscale model ensembles and observations are described, identifying opportunities for further improvements in mountain weather forecasting.

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