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A. Slingo
,
J. A. Pamment
,
R. P. Allan
, and
P. S. Wilson

Abstract

Many studies have been made of the water vapor feedback, in both satellite data and climate model simulations. Most infer the magnitude of the feedback from the variability present in geographical distributions of the key variables, or from their seasonal variations, often using data only over the oceans. It is argued that a more direct measure of the feedback should come from the interannual variability of global mean quantities, because this timescale and space scale is more appropriate for such a global phenomenon. To investigate this suggestion, the feedback derived from the simulations of clear-sky longwave fluxes (CLERA), which used data from the 15-yr reanalysis project of the European Centre for Medium-Range Weather Forecasts, is compared with simulations by the latest version of the Hadley Centre climate model. Results are taken from an integration of the atmosphere-only version of the climate model with prescribed sea surface temperatures, as well as from a control and a global warming simulation by the coupled ocean–atmosphere version. There is broad consistency between the results from CLERA and the climate model as to the strength of the feedback, although there is considerable scatter in the CLERA results. The signal of changes in the well-mixed greenhouse gases is weak in CLERA but is dominant in the global warming simulation and has to be removed in order to diagnose the water vapor feedback. This result has implications for the exploitation of long time series of satellite and other data to study this and other feedbacks.

Full access
G. P. Können
,
P. D. Jones
,
M. H. Kaltofen
, and
R. J. Allan

Abstract

Pressure data from Indonesia and Tahiti for years before 1866 are used to extend the Southern Oscillation index (SOI) back to 1841, with a gap between 1861 and 1865. Further extension is possible using an index of Jakarta rainday counts back to 1829. Rainday counts correlate (r = −0.60) with average Jakarta pressure for the June–November dry season over the 1876–1944 period. Although low, this correlation is still better than the correlation of tree rings with pressure or SOI. After 1950 the rainday count–pressure relationship alters, and by the 1990s 18% more raindays (an increase of seven per dry season) occur than the pressure would indicate. The dramatic increase in the size and population of Jakarta since 1950 is considered the most likely reason.

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A. Stickler
,
A. N. Grant
,
T. Ewen
,
T. F. Ross
,
R. S. Vose
,
J. Comeaux
,
P. Bessemoulin
,
K. Jylhä
,
W. K. Adam
,
P. Jeannet
,
A. Nagurny
,
A. M. Sterin
,
R. Allan
,
G. P. Compo
,
T. Griesser
, and
S. Brönnimann

To better understand variability in weather and climate, it is vital to address past atmospheric circulation. This need requires meteorological information not just from the surface but also at upper levels. Current global upper-level datasets only reach back to the 1940s or 1950s and do not cover some important periods in the first half of the twentieth century. Extending the observational record is therefore considered important in order to analyze climate variability in the past and verify global climate models used to predict future climate change. Although earlier upper-air data from platforms such as radiosondes, aircraft, pilot balloons, registering balloons, and kites are available from various sources, no systematic compilation and quality assessment of upper-level data prior to the International Geophysical Year (1957/58) has ever been performed. Here we present the Comprehensive Historical Upper-Air Network (CHUAN). It is a consistent global historical upper-air dataset that has been derived from heterogeneous data available from various sources as well as from newly digitized data. This paper describes the CHUAN dataset, the metadata, the quality control procedures, and the relationship to existing datasets. Some examples are given of its usefulness for analyzing weather and climate during the first half of the twentieth century. The CHUAN dataset comprises 3987 station records worldwide or about 16.4 million profiles (of which 12.6 million are before 1958 and 5.3 million, primarily from pilot balloons, are before 1948). A monthly mean version can be downloaded from the World Wide Web (www.historicalupperair.org).

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J. E. Harries
,
J. E. Russell
,
J. A. Hanafin
,
H. Brindley
,
J. Futyan
,
J. Rufus
,
S. Kellock
,
G. Matthews
,
R. Wrigley
,
A. Last
,
J. Mueller
,
R. Mossavati
,
J. Ashmall
,
E. Sawyer
,
D. Parker
,
M. Caldwell
,
P M. Allan
,
A. Smith
,
M. J. Bates
,
B. Coan
,
B. C. Stewart
,
D. R. Lepine
,
L. A. Cornwall
,
D. R. Corney
,
M. J. Ricketts
,
D. Drummond
,
D. Smart
,
R. Cutler
,
S. Dewitte
,
N. Clerbaux
,
L. Gonzalez
,
A. Ipe
,
C. Bertrand
,
A. Joukoff
,
D. Crommelynck
,
N. Nelms
,
D. T. Llewellyn-Jones
,
G. Butcher
,
G. L. Smith
,
Z. P Szewczyk
,
P E. Mlynczak
,
A. Slingo
,
R. P. Allan
, and
M. A. Ringer

This paper reports on a new satellite sensor, the Geostationary Earth Radiation Budget (GERB) experiment. GERB is designed to make the first measurements of the Earth's radiation budget from geostationary orbit. Measurements at high absolute accuracy of the reflected sunlight from the Earth, and the thermal radiation emitted by the Earth are made every 15 min, with a spatial resolution at the subsatellite point of 44.6 km (north–south) by 39.3 km (east–west). With knowledge of the incoming solar constant, this gives the primary forcing and response components of the top-of-atmosphere radiation. The first GERB instrument is an instrument of opportunity on Meteosat-8, a new spin-stabilized spacecraft platform also carrying the Spinning Enhanced Visible and Infrared (SEVIRI) sensor, which is currently positioned over the equator at 3.5°W. This overview of the project includes a description of the instrument design and its preflight and in-flight calibration. An evaluation of the instrument performance after its first year in orbit, including comparisons with data from the Clouds and the Earth's Radiant Energy System (CERES) satellite sensors and with output from numerical models, are also presented. After a brief summary of the data processing system and data products, some of the scientific studies that are being undertaken using these early data are described. This marks the beginning of a decade or more of observations from GERB, as subsequent models will fly on each of the four Meteosat Second Generation satellites.

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D. W. Stahle
,
R. D. D'Arrigo
,
P. J. Krusic
,
M. K. Cleaveland
,
E. R. Cook
,
R. J. Allan
,
J. E. Cole
,
R. B. Dunbar
,
M. D. Therrell
,
D. A. Gay
,
M. D. Moore
,
M. A. Stokes
,
B. T. Burns
,
J. Villanueva-Diaz
, and
L. G. Thompson

Exactly dated tree-ring chronologies from ENSO-sensitive regions in subtropical North America and Indonesia together register the strongest ENSO signal yet detected in tree-ring data worldwide and have been used to reconstruct the winter Southern Oscillation index (SOI) from 1706 to 1977. This reconstruction explains 53% of the variance in the instrumental winter SOI during the boreal cool season (December–February) and was verified in the time, space, and frequency domains by comparisons with independent instrumental SOI and sea surface temperature (SST) data. The large-scale SST anomaly patterns associated with ENSO in the equatorial and North Pacific during the 1879–1977 calibration period are reproduced in detail by this reconstruction. Cross-spectral analyses indicate that the reconstruction reproduces over 70% of the instrumental winter SOI variance at periods between 3.5 and 5.6 yr, and over 88% in the 4-yr frequency band. Oscillatory modes of variance identified with singular spectrum analysis at ~3.5,4.0, and 5.8 yr in both the instrumental and reconstructed series exhibit regimelike behavior over the 272-yr reconstruction. The tree-ring estimates also suggest a statistically significant increase in the interannual variability of winter SOI, more frequent cold events, and a slightly stronger sea level pressure gradient across the equatorial Pacific from the mid–nineteenth to twentieth centuries. Some of the variability in this reconstruction must be associated with background climate influences affecting the ENSO teleconnection to subtropical North America and may not arise solely from equatorial ENSO forcing. However, there is some limited independent support for the nineteenth to twentieth century changes in tropical Pacific climate identified in this reconstruction and, if substantiated, it will have important implications to the low-frequency dynamics of ENSO.

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L. C. Slivinski
,
G. P. Compo
,
P. D. Sardeshmukh
,
J. S. Whitaker
,
C. McColl
,
R. J. Allan
,
P. Brohan
,
X. Yin
,
C. A. Smith
,
L. J. Spencer
,
R. S. Vose
,
M. Rohrer
,
R. P. Conroy
,
D. C. Schuster
,
J. J. Kennedy
,
L. Ashcroft
,
S. Brönnimann
,
M. Brunet
,
D. Camuffo
,
R. Cornes
,
T. A. Cram
,
F. Domínguez-Castro
,
J. E. Freeman
,
J. Gergis
,
E. Hawkins
,
P. D. Jones
,
H. Kubota
,
T. C. Lee
,
A. M. Lorrey
,
J. Luterbacher
,
C. J. Mock
,
R. K. Przybylak
,
C. Pudmenzky
,
V. C. Slonosky
,
B. Tinz
,
B. Trewin
,
X. L. Wang
,
C. Wilkinson
,
K. Wood
, and
P. Wyszyński

Abstract

The performance of a new historical reanalysis, the NOAA–CIRES–DOE Twentieth Century Reanalysis version 3 (20CRv3), is evaluated via comparisons with other reanalyses and independent observations. This dataset provides global, 3-hourly estimates of the atmosphere from 1806 to 2015 by assimilating only surface pressure observations and prescribing sea surface temperature, sea ice concentration, and radiative forcings. Comparisons with independent observations, other reanalyses, and satellite products suggest that 20CRv3 can reliably produce atmospheric estimates on scales ranging from weather events to long-term climatic trends. Not only does 20CRv3 recreate a “best estimate” of the weather, including extreme events, it also provides an estimate of its confidence through the use of an ensemble. Surface pressure statistics suggest that these confidence estimates are reliable. Comparisons with independent upper-air observations in the Northern Hemisphere demonstrate that 20CRv3 has skill throughout the twentieth century. Upper-air fields from 20CRv3 in the late twentieth century and early twenty-first century correlate well with full-input reanalyses, and the correlation is predicted by the confidence fields from 20CRv3. The skill of analyzed 500-hPa geopotential heights from 20CRv3 for 1979–2015 is comparable to that of modern operational 3–4-day forecasts. Finally, 20CRv3 performs well on climate time scales. Long time series and multidecadal averages of mass, circulation, and precipitation fields agree well with modern reanalyses and station- and satellite-based products. 20CRv3 is also able to capture trends in tropospheric-layer temperatures that correlate well with independent products in the twentieth century, placing recent trends in a longer historical context.

Open 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
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
T. J. Ansell
,
P. D. Jones
,
R. J. Allan
,
D. Lister
,
D. E. Parker
,
M. Brunet
,
A. Moberg
,
J. Jacobeit
,
P. Brohan
,
N. A. Rayner
,
E. Aguilar
,
H. Alexandersson
,
M. Barriendos
,
T. Brandsma
,
N. J. Cox
,
P. M. Della-Marta
,
A. Drebs
,
D. Founda
,
F. Gerstengarbe
,
K. Hickey
,
T. Jónsson
,
J. Luterbacher
,
Ø. Nordli
,
H. Oesterle
,
M. Petrakis
,
A. Philipp
,
M. J. Rodwell
,
O. Saladie
,
J. Sigro
,
V. Slonosky
,
L. Srnec
,
V. Swail
,
A. M. García-Suárez
,
H. Tuomenvirta
,
X. Wang
,
H. Wanner
,
P. Werner
,
D. Wheeler
, and
E. Xoplaki

Abstract

The development of a daily historical European–North Atlantic mean sea level pressure dataset (EMSLP) for 1850–2003 on a 5° latitude by longitude grid is described. This product was produced using 86 continental and island stations distributed over the region 25°–70°N, 70°W–50°E blended with marine data from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS). The EMSLP fields for 1850–80 are based purely on the land station data and ship observations. From 1881, the blended land and marine fields are combined with already available daily Northern Hemisphere fields. Complete coverage is obtained by employing reduced space optimal interpolation. Squared correlations (r2) indicate that EMSLP generally captures 80%–90% of daily variability represented in an existing historical mean sea level pressure product and over 90% in modern 40-yr European Centre for Medium-Range Weather Forecasts Re-Analyses (ERA-40) over most of the region. A lack of sufficient observations over Greenland and the Middle East, however, has resulted in poorer reconstructions there. Error estimates, produced as part of the reconstruction technique, flag these as regions of low confidence. It is shown that the EMSLP daily fields and associated error estimates provide a unique opportunity to examine the circulation patterns associated with extreme events across the European–North Atlantic region, such as the 2003 heat wave, in the context of historical events.

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S. I. Bohnenstengel
,
S. E. Belcher
,
A. Aiken
,
J. D. Allan
,
G. Allen
,
A. Bacak
,
T. J. Bannan
,
J. F. Barlow
,
D. C. S. Beddows
,
W. J. Bloss
,
A. M. Booth
,
C. Chemel
,
O. Coceal
,
C. F. Di Marco
,
M. K. Dubey
,
K. H. Faloon
,
Z. L. Fleming
,
M. Furger
,
J. K. Gietl
,
R. R. Graves
,
D. C. Green
,
C. S. B. Grimmond
,
C. H. Halios
,
J. F. Hamilton
,
R. M. Harrison
,
M. R. Heal
,
D. E. Heard
,
C. Helfter
,
S. C. Herndon
,
R. E. Holmes
,
J. R. Hopkins
,
A. M. Jones
,
F. J. Kelly
,
S. Kotthaus
,
B. Langford
,
J. D. Lee
,
R. J. Leigh
,
A. C. Lewis
,
R. T. Lidster
,
F. D. Lopez-Hilfiker
,
J. B. McQuaid
,
C. Mohr
,
P. S. Monks
,
E. Nemitz
,
N. L. Ng
,
C. J. Percival
,
A. S. H. Prévôt
,
H. M. A. Ricketts
,
R. Sokhi
,
D. Stone
,
J. A. Thornton
,
A. H. Tremper
,
A. C. Valach
,
S. Visser
,
L. K. Whalley
,
L. R. Williams
,
L. Xu
,
D. E. Young
, and
P. Zotter

Abstract

Air quality and heat are strong health drivers, and their accurate assessment and forecast are important in densely populated urban areas. However, the sources and processes leading to high concentrations of main pollutants, such as ozone, nitrogen dioxide, and fine and coarse particulate matter, in complex urban areas are not fully understood, limiting our ability to forecast air quality accurately. This paper introduces the Clean Air for London (ClearfLo; www.clearflo.ac.uk) project’s interdisciplinary approach to investigate the processes leading to poor air quality and elevated temperatures.

Within ClearfLo, a large multi-institutional project funded by the U.K. Natural Environment Research Council (NERC), integrated measurements of meteorology and gaseous, and particulate composition/loading within the atmosphere of London, United Kingdom, were undertaken to understand the processes underlying poor air quality. Long-term measurement infrastructure installed at multiple levels (street and elevated), and at urban background, curbside, and rural locations were complemented with high-resolution numerical atmospheric simulations. Combining these (measurement–modeling) enhances understanding of seasonal variations in meteorology and composition together with the controlling processes. Two intensive observation periods (winter 2012 and the Summer Olympics of 2012) focus upon the vertical structure and evolution of the urban boundary layer; chemical controls on nitrogen dioxide and ozone production—in particular, the role of volatile organic compounds; and processes controlling the evolution, size, distribution, and composition of particulate matter. The paper shows that mixing heights are deeper over London than in the rural surroundings and that the seasonality of the urban boundary layer evolution controls when concentrations peak. The composition also reflects the seasonality of sources such as domestic burning and biogenic emissions.

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