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C. Donlon
,
I. Robinson
,
K. S. Casey
,
J. Vazquez-Cuervo
,
E. Armstrong
,
O. Arino
,
C. Gentemann
,
D. May
,
P. LeBorgne
,
J. Piollé
,
I. Barton
,
H. Beggs
,
D. J. S. Poulter
,
C. J. Merchant
,
A. Bingham
,
S. Heinz
,
A. Harris
,
G. Wick
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B. Emery
,
P. Minnett
,
R. Evans
,
D. Llewellyn-Jones
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C. Mutlow
,
R. W. Reynolds
,
H. Kawamura
, and
N. Rayner

A new generation of integrated sea surface temperature (SST) data products are being provided by the Global Ocean Data Assimilation Experiment (GODAE) High-Resolution SST Pilot Project (GHRSST-PP). These combine in near-real time various SST data products from several different satellite sensors and in situ observations and maintain the fine spatial and temporal resolution needed by SST inputs to operational models. The practical realization of such an approach is complicated by the characteristic differences that exist between measurements of SST obtained from subsurface in-water sensors, and satellite microwave and satellite infrared radiometer systems. Furthermore, diurnal variability of SST within a 24-h period, manifested as both warm-layer and cool-skin deviations, introduces additional uncertainty for direct intercomparison between data sources and the implementation of data-merging strategies. The GHRSST-PP has developed and now operates an internationally distributed system that provides operational feeds of regional and global coverage high-resolution SST data products (better than 10 km and ~6 h). A suite of online satellite SST diagnostic systems are also available within the project. All GHRSST-PP products have a standard format, include uncertainty estimates for each measurement, and are served to the international user community free of charge through a variety of data transport mechanisms and access points. They are being used for a number of operational applications. The approach will also be extended back to 1981 by a dedicated reanalysis project. This paper provides a summary overview of the GHRSST-PP structure, activities, and data products. For a complete discussion, and access to data products and services see the information online at www.ghrsst-pp.org.

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Peter Knippertz
,
Hugh Coe
,
J. Christine Chiu
,
Mat J. Evans
,
Andreas H. Fink
,
Norbert Kalthoff
,
Catherine Liousse
,
Celine Mari
,
Richard P. Allan
,
Barbara Brooks
,
Sylvester Danour
,
Cyrille Flamant
,
Oluwagbemiga O. Jegede
,
Fabienne Lohou
, and
John H. Marsham

Abstract

Massive economic and population growth, and urbanization are expected to lead to a tripling of anthropogenic emissions in southern West Africa (SWA) between 2000 and 2030. However, the impacts of this on human health, ecosystems, food security, and the regional climate are largely unknown. An integrated assessment is challenging due to (a) a superposition of regional effects with global climate change; (b) a strong dependence on the variable West African monsoon; (c) incomplete scientific understanding of interactions between emissions, clouds, radiation, precipitation, and regional circulations; and (d) a lack of observations. This article provides an overview of the DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) project. DACCIWA will conduct extensive fieldwork in SWA to collect high-quality observations, spanning the entire process chain from surface-based natural and anthropogenic emissions to impacts on health, ecosystems, and climate. Combining the resulting benchmark dataset with a wide range of modeling activities will allow (a) assessment of relevant physical, chemical, and biological processes; (b) improvement of the monitoring of climate and atmospheric composition from space; and (c) development of the next generation of weather and climate models capable of representing coupled cloud–aerosol interactions. The latter will ultimately contribute to reduce uncertainties in climate predictions. DACCIWA collaborates closely with operational centers, international programs, policymakers, and users to actively guide sustainable future planning for West Africa. It is hoped that some of DACCIWA’s scientific findings and technical developments will be applicable to other monsoon regions.

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D. N. Whiteman
,
B. Demoz
,
G. Schwemmer
,
B. Gentry
,
P. Di Girolamo
,
D. Sabatino
,
J. Comer
,
I. Veselovskii
,
K. Evans
,
R-F. Lin
,
Z. Wang
,
A. Behrendt
,
V. Wulfmeyer
,
E. Browell
,
R. Ferrare
,
S. Ismail
, and
J. Wang

Abstract

The NASA GSFC Scanning Raman Lidar (SRL) participated in the International H2O Project (IHOP) that occurred in May and June 2002 in the midwestern part of the United States. The SRL system configuration and methods of data analysis were described in Part I of this paper. In this second part, comparisons of SRL water vapor measurements and those of Lidar Atmospheric Sensing Experiment (LASE) airborne water vapor lidar and chilled-mirror radiosonde are performed. Two case studies are then presented: one for daytime and one for nighttime. The daytime case study is of a convectively driven boundary layer event and is used to characterize the daytime SRL water vapor random error characteristics. The nighttime case study is of a thunderstorm-generated cirrus cloud case that is studied in its meteorological context. Upper-tropospheric humidification due to precipitation from the cirrus cloud is quantified as is the cirrus cloud optical depth, extinction-to-backscatter ratio, ice water content, cirrus particle size, and both particle and volume depolarization ratios. A stability and back-trajectory analysis is performed to study the origin of wave activity in one of the cloud layers. These unprecedented cirrus cloud measurements are being used in a cirrus cloud modeling study.

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C. A. McLinden
,
A. E. Bourassa
,
S. Brohede
,
M. Cooper
,
D. A. Degenstein
,
W. J. F. Evans
,
R. L. Gattinger
,
C. S. Haley
,
E. J. Llewellyn
,
N. D. Lloyd
,
P. Loewen
,
R. V. Martin
,
J. C. McConnell
,
I. C. McDade
,
D. Murtagh
,
L. Rieger
,
C. von Savigny
,
P. E. Sheese
,
C. E. Sioris
,
B. Solheim
, and
K. Strong

On 20 February 2001, a converted Russian ICBM delivered Odin, a small Swedish satellite, into low Earth orbit. One of the sensors onboard is a small Canadian spectrometer called OSIRIS. By measuring scattered sunlight from Earth's horizon, or limb, OSIRIS is able to deduce the abundance of trace gases and particles from the upper troposphere into the lower thermosphere. Designed and built on a modest budget, OSIRIS has exceeded not only its 2-yr lifetime but also all expectations. With more than a decade of continuous data, OSIRIS has recorded over 1.8 million limb scans. The complexities associated with unraveling scattered light in order to convert OSIRIS spectra into highquality geophysical profiles have forced the OSIRIS team to develop leading-edge algorithms and computer models. These profiles are being used to help address many science questions, including the coupling of atmospheric regions (e.g., stratosphere–troposphere exchange) and the budgets and trends in ozone, nitrogen, bromine, and other species. One specific example is the distribution and abundance of upper-tropospheric, lightning-produced reactive nitrogen and ozone. Arguably OSIRIS's most important contributions come from its aerosol measurements, including detection and characterization of subvisual cirrus and polar stratospheric and mesospheric clouds. OSIRIS also provides a unique view of the stratospheric aerosol layer, and it is able to identify and track perturbations from volcanic activity and biomass burning.

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C. Flamant
,
P. Knippertz
,
A. H. Fink
,
A. Akpo
,
B. Brooks
,
C. J. Chiu
,
H. Coe
,
S. Danuor
,
M. Evans
,
O. Jegede
,
N. Kalthoff
,
A. Konaré
,
C. Liousse
,
F. Lohou
,
C. Mari
,
H. Schlager
,
A. Schwarzenboeck
,
B. Adler
,
L. Amekudzi
,
J. Aryee
,
M. Ayoola
,
A. M. Batenburg
,
G. Bessardon
,
S. Borrmann
,
J. Brito
,
K. Bower
,
F. Burnet
,
V. Catoire
,
A. Colomb
,
C. Denjean
,
K. Fosu-Amankwah
,
P. G. Hill
,
J. Lee
,
M. Lothon
,
M. Maranan
,
J. Marsham
,
R. Meynadier
,
J.-B. Ngamini
,
P. Rosenberg
,
D. Sauer
,
V. Smith
,
G. Stratmann
,
J. W. Taylor
,
C. Voigt
, and
V. Yoboué

Abstract

The European Union (EU)-funded project Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa (DACCIWA) investigates the relationship between weather, climate, and air pollution in southern West Africa—an area with rapid population growth, urbanization, and an increase in anthropogenic aerosol emissions. The air over this region contains a unique mixture of natural and anthropogenic gases, liquid droplets, and particles, emitted in an environment in which multilayer clouds frequently form. These exert a large influence on the local weather and climate, mainly owing to their impact on radiation, the surface energy balance, and thus the diurnal cycle of the atmospheric boundary layer.

In June and July 2016, DACCIWA organized a major international field campaign in Ivory Coast, Ghana, Togo, Benin, and Nigeria. Three supersites in Kumasi, Savè, and Ile-Ife conducted permanent measurements and 15 intensive observation periods. Three European aircraft together flew 50 research flights between 27 June and 16 July 2016, for a total of 155 h. DACCIWA scientists launched weather balloons several times a day across the region (772 in total), measured urban emissions, and evaluated health data. The main objective was to build robust statistics of atmospheric composition, dynamics, and low-level cloud properties in various chemical landscapes to investigate their mutual interactions.

This article presents an overview of the DACCIWA field campaign activities as well as some first research highlights. The rich data obtained during the campaign will be made available to the scientific community and help to advance scientific understanding, modeling, and monitoring of the atmosphere over southern West Africa.

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P. Joe
,
S. Belair
,
N.B. Bernier
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V. Bouchet
,
J. R. Brook
,
D. Brunet
,
W. Burrows
,
J.-P. Charland
,
A. Dehghan
,
N. Driedger
,
C. Duhaime
,
G. Evans
,
A.-B. Filion
,
R. Frenette
,
J. de Grandpré
,
I. Gultepe
,
D. Henderson
,
A. Herdt
,
N. Hilker
,
L. Huang
,
E. Hung
,
G. Isaac
,
C.-H. Jeong
,
D. Johnston
,
J. Klaassen
,
S. Leroyer
,
H. Lin
,
M. MacDonald
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J. MacPhee
,
Z. Mariani
,
T. Munoz
,
J. Reid
,
A. Robichaud
,
Y. Rochon
,
K. Shairsingh
,
D. Sills
,
L. Spacek
,
C. Stroud
,
Y. Su
,
N. Taylor
,
J. Vanos
,
J. Voogt
,
J. M. Wang
,
T. Wiechers
,
S. Wren
,
H. Yang
, and
T. Yip

Abstract

The Pan and Parapan American Games (PA15) are the third largest sporting event in the world and were held in Toronto in the summer of 2015 (10–26 July and 7–15 August). This was used as an opportunity to coordinate and showcase existing innovative research and development activities related to weather, air quality (AQ), and health at Environment and Climate Change Canada. New observational technologies included weather stations based on compact sensors that were augmented with black globe thermometers, two Doppler lidars, two wave buoys, a 3D lightning mapping array, two new AQ stations, and low-cost AQ and ultraviolet sensors. These were supplemented by observations from other agencies, four mobile vehicles, two mobile AQ laboratories, and two supersites with enhanced vertical profiling. High-resolution modeling for weather (250 m and 1 km), AQ (2.5 km), lake circulation (2 km), and wave models (250-m, 1-km, and 2.5-km ensembles) were run. The focus of the science, which guided the design of the observation network, was to characterize and investigate the lake breeze, which affects thunderstorm initiation, air pollutant transport, and heat stress. Experimental forecasts and nowcasts were provided by research support desks. Web portals provided access to the experimental products for other government departments, public health authorities, and PA15 decision-makers. The data have been released through the government of Canada’s Open Data Portal and as a World Meteorological Organization’s Global Atmospheric Watch Urban Research Meteorology and Environment dataset.

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H. W. Barker
,
G. L. Stephens
,
P. T. Partain
,
J. W. Bergman
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B. Bonnel
,
K. Campana
,
E. E. Clothiaux
,
S. Clough
,
S. Cusack
,
J. Delamere
,
J. Edwards
,
K. F. Evans
,
Y. Fouquart
,
S. Freidenreich
,
V. Galin
,
Y. Hou
,
S. Kato
,
J. Li
,
E. Mlawer
,
J.-J. Morcrette
,
W. O'Hirok
,
P. Räisänen
,
V. Ramaswamy
,
B. Ritter
,
E. Rozanov
,
M. Schlesinger
,
K. Shibata
,
P. Sporyshev
,
Z. Sun
,
M. Wendisch
,
N. Wood
, and
F. Yang

Abstract

The primary purpose of this study is to assess the performance of 1D solar radiative transfer codes that are used currently both for research and in weather and climate models. Emphasis is on interpretation and handling of unresolved clouds. Answers are sought to the following questions: (i) How well do 1D solar codes interpret and handle columns of information pertaining to partly cloudy atmospheres? (ii) Regardless of the adequacy of their assumptions about unresolved clouds, do 1D solar codes perform as intended?

One clear-sky and two plane-parallel, homogeneous (PPH) overcast cloud cases serve to elucidate 1D model differences due to varying treatments of gaseous transmittances, cloud optical properties, and basic radiative transfer. The remaining four cases involve 3D distributions of cloud water and water vapor as simulated by cloud-resolving models. Results for 25 1D codes, which included two line-by-line (LBL) models (clear and overcast only) and four 3D Monte Carlo (MC) photon transport algorithms, were submitted by 22 groups. Benchmark, domain-averaged irradiance profiles were computed by the MC codes. For the clear and overcast cases, all MC estimates of top-of-atmosphere albedo, atmospheric absorptance, and surface absorptance agree with one of the LBL codes to within ±2%. Most 1D codes underestimate atmospheric absorptance by typically 15–25 W m–2 at overhead sun for the standard tropical atmosphere regardless of clouds.

Depending on assumptions about unresolved clouds, the 1D codes were partitioned into four genres: (i) horizontal variability, (ii) exact overlap of PPH clouds, (iii) maximum/random overlap of PPH clouds, and (iv) random overlap of PPH clouds. A single MC code was used to establish conditional benchmarks applicable to each genre, and all MC codes were used to establish the full 3D benchmarks. There is a tendency for 1D codes to cluster near their respective conditional benchmarks, though intragenre variances typically exceed those for the clear and overcast cases. The majority of 1D codes fall into the extreme category of maximum/random overlap of PPH clouds and thus generally disagree with full 3D benchmark values. Given the fairly limited scope of these tests and the inability of any one code to perform extremely well for all cases begs the question that a paradigm shift is due for modeling 1D solar fluxes for cloudy atmospheres.

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D. N. Whiteman
,
B. Demoz
,
K. Rush
,
G. Schwemmer
,
B. Gentry
,
P. Di Girolamo
,
J. Comer
,
I. Veselovskii
,
K. Evans
,
S. H. Melfi
,
Z. Wang
,
M. Cadirola
,
B. Mielke
,
D. Venable
, and
T. Van Hove

Abstract

The NASA Goddard Space Flight Center (GSFC) Scanning Raman Lidar (SRL) participated in the International H2O Project (IHOP), which occurred in May and June 2002 in the midwestern part of the United States. The SRL received extensive optical modifications prior to and during the IHOP campaign that added new measurement capabilities and enabled unprecedented daytime water vapor measurements by a Raman lidar system. Improvements were also realized in nighttime upper-tropospheric water vapor measurements. The other new measurements that were added to the SRL for the IHOP deployment included rotational Raman temperature, depolarization, cloud liquid water, and cirrus cloud ice water content. In this first of two parts, the details of the operational configuration of the SRL during IHOP are provided along with a description of the analysis and calibration procedures for water vapor mixing ratio, aerosol depolarization, and cirrus cloud extinction-to-backscatter ratio. For the first time, a Raman water vapor lidar calibration is performed, taking full account of the temperature sensitivity of water vapor and nitrogen Raman scattering. Part II presents case studies that permit the daytime and nighttime error statistics to be quantified.

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Robert F. Cahalan
,
Lazaros Oreopoulos
,
Alexander Marshak
,
K. Franklin Evans
,
Anthony B. Davis
,
Robert Pincus
,
Ken H. Yetzer
,
Bernhard Mayer
,
Roger Davies
,
Thomas P. Ackerman
,
Howard W. Barker
,
Eugene E. Clothiaux
,
Robert G. Ellingson
,
Michael J. Garay
,
Evgueni Kassianov
,
Stefan Kinne
,
Andreas Macke
,
William O'hirok
,
Philip T. Partain
,
Sergei M. Prigarin
,
Alexei N. Rublev
,
Graeme L. Stephens
,
Frederic Szczap
,
Ezra E. Takara
,
Tamas Várnai
,
Guoyong Wen
, and
Tatiana B. Zhuravleva

The interaction of clouds with solar and terrestrial radiation is one of the most important topics of climate research. In recent years it has been recognized that only a full three-dimensional (3D) treatment of this interaction can provide answers to many climate and remote sensing problems, leading to the worldwide development of numerous 3D radiative transfer (RT) codes. The international Intercomparison of 3D Radiation Codes (I3RC), described in this paper, sprung from the natural need to compare the performance of these 3D RT codes used in a variety of current scientific work in the atmospheric sciences. I3RC supports intercomparison and development of both exact and approximate 3D methods in its effort to 1) understand and document the errors/limits of 3D algorithms and their sources; 2) provide “baseline” cases for future code development for 3D radiation; 3) promote sharing and production of 3D radiative tools; 4) derive guidelines for 3D radiative tool selection; and 5) improve atmospheric science education in 3D RT. Results from the two completed phases of I3RC have been presented in two workshops and are expected to guide improvements in both remote sensing and radiative energy budget calculations in cloudy atmospheres.

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Dennis Baldocchi
,
Eva Falge
,
Lianhong Gu
,
Richard Olson
,
David Hollinger
,
Steve Running
,
Peter Anthoni
,
Ch. Bernhofer
,
Kenneth Davis
,
Robert Evans
,
Jose Fuentes
,
Allen Goldstein
,
Gabriel Katul
,
Beverly Law
,
Xuhui Lee
,
Yadvinder Malhi
,
Tilden Meyers
,
William Munger
,
Walt Oechel
,
K. T. Paw U
,
Kim Pilegaard
,
H. P. Schmid
,
Riccardo Valentini
,
Shashi Verma
,
Timo Vesala
,
Kell Wilson
, and
Steve Wofsy

FLUXNET is a global network of micrometeorological flux measurement sites that measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere. At present over 140 sites are operating on a long-term and continuous basis. Vegetation under study includes temperate conifer and broadleaved (deciduous and evergreen) forests, tropical and boreal forests, crops, grasslands, chaparral, wetlands, and tundra. Sites exist on five continents and their latitudinal distribution ranges from 70°N to 30°S.

FLUXNET has several primary functions. First, it provides infrastructure for compiling, archiving, and distributing carbon, water, and energy flux measurement, and meteorological, plant, and soil data to the science community. (Data and site information are available online at the FLUXNET Web site, http://www-eosdis.ornl.gov/FLUXNET/.) Second, the project supports calibration and flux intercomparison activities. This activity ensures that data from the regional networks are intercomparable. And third, FLUXNET supports the synthesis, discussion, and communication of ideas and data by supporting project scientists, workshops, and visiting scientists. The overarching goal is to provide information for validating computations of net primary productivity, evaporation, and energy absorption that are being generated by sensors mounted on the NASA Terra satellite.

Data being compiled by FLUXNET are being used to quantify and compare magnitudes and dynamics of annual ecosystem carbon and water balances, to quantify the response of stand-scale carbon dioxide and water vapor flux densities to controlling biotic and abiotic factors, and to validate a hierarchy of soil–plant–atmosphere trace gas exchange models. Findings so far include 1) net CO2 exchange of temperate broadleaved forests increases by about 5.7 g C m−2 day−1 for each additional day that the growing season is extended; 2) the sensitivity of net ecosystem CO2 exchange to sunlight doubles if the sky is cloudy rather than clear; 3) the spectrum of CO2 flux density exhibits peaks at timescales of days, weeks, and years, and a spectral gap exists at the month timescale; 4) the optimal temperature of net CO2 exchange varies with mean summer temperature; and 5) stand age affects carbon dioxide and water vapor flux densities.

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