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Howard J. Diamond
,
Carl J. Schreck
,
Adam Allgood
,
Emily J. Becker
,
Eric S. Blake
,
Francis G. Bringas
,
Suzana J. Camargo
,
Lin Chen
,
Caio A.S. Coelho
,
Nicolas Fauchereau
,
Chris Fogarty
,
Stanley B. Goldenberg
,
Gustavo Goni
,
Daniel S. Harnos
,
Qiong He
,
Zeng-Zhen Hu
,
Philip J. Klotzbach
,
John A. Knaff
,
Arun Kumar
,
Michelle L’Heureux
,
Chris W. Landsea
,
I-I. Lin
,
Andrew M. Lorrey
,
Jing-Jia Luo
,
Andrew D. Magee
,
Richard J. Pasch
,
Alexandre B. Pezza
,
Matthew Rosencrans
,
Jozef Rozkošný
,
Blair C. Trewin
,
Ryan E. Truchelut
,
Bin Wang
,
Hui Wang
, and
Kimberly M. Wood
Open access
J. Ching
,
G. Mills
,
B. Bechtel
,
L. See
,
J. Feddema
,
X. Wang
,
C. Ren
,
O. Brousse
,
A. Martilli
,
M. Neophytou
,
P. Mouzourides
,
I. Stewart
,
A. Hanna
,
E. Ng
,
M. Foley
,
P. Alexander
,
D. Aliaga
,
D. Niyogi
,
A. Shreevastava
,
P. Bhalachandran
,
V. Masson
,
J. Hidalgo
,
J. Fung
,
M. Andrade
,
A. Baklanov
,
W. Dai
,
G. Milcinski
,
M. Demuzere
,
N. Brunsell
,
M. Pesaresi
,
S. Miao
,
Q. Mu
,
F. Chen
, and
N. Theeuwes

Abstract

The World Urban Database and Access Portal Tools (WUDAPT) is an international community-based initiative to acquire and disseminate climate relevant data on the physical geographies of cities for modeling and analysis purposes. The current lacuna of globally consistent information on cities is a major impediment to urban climate science toward informing and developing climate mitigation and adaptation strategies at urban scales. WUDAPT consists of a database and a portal system; its database is structured into a hierarchy representing different levels of detail, and the data are acquired using innovative protocols that utilize crowdsourcing approaches, Geowiki tools, freely accessible data, and building typology archetypes. The base level of information (L0) consists of local climate zone (LCZ) maps of cities; each LCZ category is associated with a range of values for model-relevant surface descriptors (roughness, impervious surface cover, roof area, building heights, etc.). Levels 1 (L1) and 2 (L2) will provide specific intra-urban values for other relevant descriptors at greater precision, such as data morphological forms, material composition data, and energy usage. This article describes the status of the WUDAPT project and demonstrates its potential value using observations and models. As a community-based project, other researchers are encouraged to participate to help create a global urban database of value to urban climate scientists.

Full access
Howard J. Diamond
,
Carl J. Schreck III
,
Emily J. Becker
,
Gerald D. Bell
,
Eric S. Blake
,
Stephanie Bond
,
Francis G. Bringas
,
Suzana J. Camargo
,
Lin Chen
,
Caio A. S. Coelho
,
Ricardo Domingues
,
Stanley B. Goldenberg
,
Gustavo Goni
,
Nicolas Fauchereau
,
Michael S. Halpert
,
Qiong He
,
Philip J. Klotzbach
,
John A. Knaff
,
Michelle L'Heureux
,
Chris W. Landsea
,
I.-I. Lin
,
Andrew M. Lorrey
,
Jing-Jia Luo
,
Kyle MacRitchie
,
Andrew D. Magee
,
Ben Noll
,
Richard J. Pasch
,
Alexandre B. Pezza
,
Matthew Rosencrans
,
Michael K. Tippet
,
Blair C. Trewin
,
Ryan E. Truchelut
,
Bin Wang
,
Hui Wang
,
Kimberly M. Wood
,
John-Mark Woolley
, and
Steven H. Young
Free access
Xiang-Yu Li
,
Hailong Wang
,
Jingyi Chen
,
Satoshi Endo
,
Geet George
,
Brian Cairns
,
Seethala Chellappan
,
Xubin Zeng
,
Simon Kirschler
,
Christiane Voigt
,
Armin Sorooshian
,
Ewan Crosbie
,
Gao Chen
,
Richard Anthony Ferrare
,
William I. Gustafson Jr.
,
Johnathan W. Hair
,
Mary M. Kleb
,
Hongyu Liu
,
Richard Moore
,
David Painemal
,
Claire Robinson
,
Amy Jo Scarino
,
Michael Shook
,
Taylor J. Shingler
,
Kenneth Lee Thornhill
,
Florian Tornow
,
Heng Xiao
,
Luke D. Ziemba
, and
Paquita Zuidema

Abstract

Large-eddy simulation (LES) is able to capture key boundary layer (BL) turbulence and cloud processes. Yet, large-scale forcing and surface turbulent fluxes of sensible and latent heat are often poorly prescribed for LESs. We derive these quantities from measurements and reanalysis obtained for two cold-air outbreak (CAO) events during Phase I of the Aerosol Cloud Meteorology Interactions over the Western Atlantic Experiment (ACTIVATE) in February–March 2020. We study the two contrasting CAO cases by performing LES and test the sensitivity of BL structure and clouds to large-scale forcings and turbulent heat fluxes. Profiles of atmospheric state and large-scale divergence and surface turbulent heat fluxes obtained from ERA5 data agree reasonably well with those derived from ACTIVATE field measurements for both cases at the sampling time and location. Therefore, we adopt the time-evolving heat fluxes, wind, and advective tendencies profiles from ERA5 data to drive the LES. We find that large-scale thermodynamic advective tendencies and wind relaxations are important for the LES to capture the evolving observed BL meteorological states characterized by the hourly ERA5 data and validated by the observations. We show that the divergence (or vertical velocity) is important in regulating the BL growth driven by surface heat fluxes in LESs. The evolution of liquid water path is largely affected by the evolution of surface heat fluxes. The liquid water path simulated in LES agrees reasonably well with the ACTIVATE measurements. This study paves the path to investigate aerosol–cloud–meteorology interactions using LES informed and evaluated by ACTIVATE field measurements.

Full access
Xiang-Yu Li
,
Hailong Wang
,
Jingyi Chen
,
Satoshi Endo
,
Simon Kirschler
,
Christiane Voigt
,
Ewan Crosbie
,
Luke D. Ziemba
,
David Painemal
,
Brian Cairns
,
Johnathan W. Hair
,
Andrea F. Corral
,
Claire Robinson
,
Hossein Dadashazar
,
Armin Sorooshian
,
Gao Chen
,
Richard Anthony Ferrare
,
Mary M. Kleb
,
Hongyu Liu
,
Richard Moore
,
Amy Jo Scarino
,
Michael A. Shook
,
Taylor J. Shingler
,
Kenneth Lee Thornhill
,
Florian Tornow
,
Heng Xiao
, and
Xubin Zeng

Abstract

Aerosol effects on micro/macrophysical properties of marine stratocumulus clouds over the western North Atlantic Ocean (WNAO) are investigated using in situ measurements and large-eddy simulations (LES) for two cold-air outbreak (CAO) cases (28 February and 1 March 2020) during the Aerosol Cloud Meteorology Interactions over the Western Atlantic Experiment (ACTIVATE). The LES is able to reproduce the vertical profiles of liquid water content (LWC), effective radius r eff and cloud droplet number concentration Nc from fast cloud droplet probe (FCDP) in situ measurements for both cases. Furthermore, we show that aerosols affect cloud properties (Nc , r eff, and LWC) via the prescribed bulk hygroscopicity of aerosols ( κ ¯ ) and aerosol size distribution characteristics. Nc , r eff, and liquid water path (LWP) are positively correlated to κ ¯ and aerosol number concentration (Na ) while cloud fractional cover (CFC) is insensitive to κ ¯ and aerosol size distributions for the two cases. The realistic changes to aerosol size distribution (number concentration, width, and the geometrical diameter) with the same meteorology state allow us to investigate aerosol effects on cloud properties without meteorological feedback. We also use the LES results to evaluate cloud properties from two reanalysis products, ERA5 and MERRA-2. Compared to LES, the ERA5 is able to capture the time evolution of LWP and total cloud coverage within the study domain during both CAO cases while MERRA-2 underestimates them.

Open access
James D. Doyle
,
Jonathan R. Moskaitis
,
Joel W. Feldmeier
,
Ronald J. Ferek
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Mark Beaubien
,
Michael M. Bell
,
Daniel L. Cecil
,
Robert L. Creasey
,
Patrick Duran
,
Russell L. Elsberry
,
William A. Komaromi
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John Molinari
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David R. Ryglicki
,
Daniel P. Stern
,
Christopher S. Velden
,
Xuguang Wang
,
Todd Allen
,
Bradford S. Barrett
,
Peter G. Black
,
Jason P. Dunion
,
Kerry A. Emanuel
,
Patrick A. Harr
,
Lee Harrison
,
Eric A. Hendricks
,
Derrick Herndon
,
William Q. Jeffries
,
Sharanya J. Majumdar
,
James A. Moore
,
Zhaoxia Pu
,
Robert F. Rogers
,
Elizabeth R. Sanabia
,
Gregory J. Tripoli
, and
Da-Lin Zhang

Abstract

Tropical cyclone (TC) outflow and its relationship to TC intensity change and structure were investigated in the Office of Naval Research Tropical Cyclone Intensity (TCI) field program during 2015 using dropsondes deployed from the innovative new High-Definition Sounding System (HDSS) and remotely sensed observations from the Hurricane Imaging Radiometer (HIRAD), both on board the NASA WB-57 that flew in the lower stratosphere. Three noteworthy hurricanes were intensively observed with unprecedented horizontal resolution: Joaquin in the Atlantic and Marty and Patricia in the eastern North Pacific. Nearly 800 dropsondes were deployed from the WB-57 flight level of ∼60,000 ft (∼18 km), recording atmospheric conditions from the lower stratosphere to the surface, while HIRAD measured the surface winds in a 50-km-wide swath with a horizontal resolution of 2 km. Dropsonde transects with 4–10-km spacing through the inner cores of Hurricanes Patricia, Joaquin, and Marty depict the large horizontal and vertical gradients in winds and thermodynamic properties. An innovative technique utilizing GPS positions of the HDSS reveals the vortex tilt in detail not possible before. In four TCI flights over Joaquin, systematic measurements of a major hurricane’s outflow layer were made at high spatial resolution for the first time. Dropsondes deployed at 4-km intervals as the WB-57 flew over the center of Hurricane Patricia reveal in unprecedented detail the inner-core structure and upper-tropospheric outflow associated with this historic hurricane. Analyses and numerical modeling studies are in progress to understand and predict the complex factors that influenced Joaquin’s and Patricia’s unusual intensity changes.

Open access
D. A. Knopf
,
K. R. Barry
,
T. A. Brubaker
,
L. G. Jahl
,
K. A. Jankowski
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J. Li
,
Y. Lu
,
L. W. Monroe
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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
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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.

Full access
Bart Geerts
,
Scott E. Giangrande
,
Greg M. McFarquhar
,
Lulin Xue
,
Steven J. Abel
,
Jennifer M. Comstock
,
Susanne Crewell
,
Paul J. DeMott
,
Kerstin Ebell
,
Paul Field
,
Thomas C. J. Hill
,
Alexis Hunzinger
,
Michael P. Jensen
,
Karen L. Johnson
,
Timothy W. Juliano
,
Pavlos Kollias
,
Branko Kosovic
,
Christian Lackner
,
Ed Luke
,
Christof Lüpkes
,
Alyssa A. Matthews
,
Roel Neggers
,
Mikhail Ovchinnikov
,
Heath Powers
,
Matthew D. Shupe
,
Thomas Spengler
,
Benjamin E. Swanson
,
Michael Tjernström
,
Adam K. Theisen
,
Nathan A. Wales
,
Yonggang Wang
,
Manfred Wendisch
, and
Peng Wu

Abstract

One of the most intense air mass transformations on Earth happens when cold air flows from frozen surfaces to much warmer open water in cold-air outbreaks (CAOs), a process captured beautifully in satellite imagery. Despite the ubiquity of the CAO cloud regime over high-latitude oceans, we have a rather poor understanding of its properties, its role in energy and water cycles, and its treatment in weather and climate models. The Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) was conducted to better understand this regime and its representation in models. COMBLE aimed to examine the relations between surface fluxes, boundary layer structure, aerosol, cloud, and precipitation properties, and mesoscale circulations in marine CAOs. Processes affecting these properties largely fall in a range of scales where boundary layer processes, convection, and precipitation are tightly coupled, which makes accurate representation of the CAO cloud regime in numerical weather prediction and global climate models most challenging. COMBLE deployed an Atmospheric Radiation Measurement Mobile Facility at a coastal site in northern Scandinavia (69°N), with additional instruments on Bear Island (75°N), from December 2019 to May 2020. CAO conditions were experienced 19% (21%) of the time at the main site (on Bear Island). A comprehensive suite of continuous in situ and remote sensing observations of atmospheric conditions, clouds, precipitation, and aerosol were collected. Because of the clouds’ well-defined origin, their shallow depth, and the broad range of observed temperature and aerosol concentrations, the COMBLE dataset provides a powerful modeling testbed for improving the representation of mixed-phase cloud processes in large-eddy simulations and large-scale models.

Full access
Russell S. Vose
,
Scott Applequist
,
Mark A. Bourassa
,
Sara C. Pryor
,
Rebecca J. Barthelmie
,
Brian Blanton
,
Peter D. Bromirski
,
Harold E. Brooks
,
Arthur T. DeGaetano
,
Randall M. Dole
,
David R. Easterling
,
Robert E. Jensen
,
Thomas R. Karl
,
Richard W. Katz
,
Katherine Klink
,
Michael C. Kruk
,
Kenneth E. Kunkel
,
Michael C. MacCracken
,
Thomas C. Peterson
,
Karsten Shein
,
Bridget R. Thomas
,
John E. Walsh
,
Xiaolan L. Wang
,
Michael F. Wehner
,
Donald J. Wuebbles
, and
Robert S. Young

This scientific assessment examines changes in three climate extremes—extratropical storms, winds, and waves—with an emphasis on U.S. coastal regions during the cold season. There is moderate evidence of an increase in both extratropical storm frequency and intensity during the cold season in the Northern Hemisphere since 1950, with suggestive evidence of geographic shifts resulting in slight upward trends in offshore/coastal regions. There is also suggestive evidence of an increase in extreme winds (at least annually) over parts of the ocean since the early to mid-1980s, but the evidence over the U.S. land surface is inconclusive. Finally, there is moderate evidence of an increase in extreme waves in winter along the Pacific coast since the 1950s, but along other U.S. shorelines any tendencies are of modest magnitude compared with historical variability. The data for extratropical cyclones are considered to be of relatively high quality for trend detection, whereas the data for extreme winds and waves are judged to be of intermediate quality. In terms of physical causes leading to multidecadal changes, the level of understanding for both extratropical storms and extreme winds is considered to be relatively low, while that for extreme waves is judged to be intermediate. Since the ability to measure these changes with some confidence is relatively recent, understanding is expected to improve in the future for a variety of reasons, including increased periods of record and the development of “climate reanalysis” projects.

Full access
P. W. Thorne
,
R. J. Allan
,
L. Ashcroft
,
P. Brohan
,
R. J. H Dunn
,
M. J. Menne
,
P. R. Pearce
,
J. Picas
,
K. M. Willett
,
M. Benoy
,
S. Bronnimann
,
P. O. Canziani
,
J. Coll
,
R. Crouthamel
,
G. P. Compo
,
D. Cuppett
,
M. Curley
,
C. Duffy
,
I. Gillespie
,
J. Guijarro
,
S. Jourdain
,
E. C. Kent
,
H. Kubota
,
T. P. Legg
,
Q. Li
,
J. Matsumoto
,
C. Murphy
,
N. A. Rayner
,
J. J. Rennie
,
E. Rustemeier
,
L. C. Slivinski
,
V. Slonosky
,
A. Squintu
,
B. Tinz
,
M. A. Valente
,
S. Walsh
,
X. L. Wang
,
N. Westcott
,
K. Wood
,
S. D. Woodruff
, and
S. J. Worley

Abstract

Observations are the foundation for understanding the climate system. Yet, currently available land meteorological data are highly fractured into various global, regional, and national holdings for different variables and time scales, from a variety of sources, and in a mixture of formats. Added to this, many data are still inaccessible for analysis and usage. To meet modern scientific and societal demands as well as emerging needs such as the provision of climate services, it is essential that we improve the management and curation of available land-based meteorological holdings. We need a comprehensive global set of data holdings, of known provenance, that is truly integrated both across essential climate variables (ECVs) and across time scales to meet the broad range of stakeholder needs. These holdings must be easily discoverable, made available in accessible formats, and backed up by multitiered user support. The present paper provides a high-level overview, based upon broad community input, of the steps that are required to bring about this integration. The significant challenge is to find a sustained means to realize this vision. This requires a long-term international program. The database that results will transform our collective ability to provide societally relevant research, analysis, and predictions in many weather- and climate-related application areas across much of the globe.

Open access