pinecone/core-2020-05-10-deduplication huggingface dataset:
Agreement in late twentieth century Southern Hemisphere stratospheric temperature trends in observations and CCMVal-2, CMIP3, and CMIP5 models

We present a comparison of temperature trends using different satellite and radiosonde observations and climate (GCM) and chemistry-climate model (CCM) outputs, focusing on the role of photochemical ozone depletion in the Antarctic lower stratosphere during the second half of the twentieth century. Ozone-induced stratospheric cooling peaks during November at an altitude of approximately 100 hPa in radiosonde observations, with 1969 to 1998 trends in the range of -3.8 to -4.7 K/dec. This stratospheric cooling trend is more than 50% greater than the previously estimated value of -2.4 K/dec, which suggested that the CCMs were overestimating the stratospheric cooling, and that the less complex GCMs forced by prescribed ozone were matching observations better. Corresponding ensemble mean model trends are -3.8K/dec for the CCMs, -3.5K/dec for the CMIP5 GCMs, and -2.7K/dec for the CMIP3 GCMs. Accounting for various sources of uncertainty-including sampling uncertainty, measurement error, model spread, and trend confidence intervals-observations and CCM and GCM ensembles are consistent in this new analysis. This consistency does not apply to each individual that makes up the GCM and CCM ensembles, and some do not show significant ozone-induced cooling. Nonetheless, analysis of the joint ozone and temperature trends in the CCMs suggests that the modeled cooling/ozone-depletion relationship is within the range of observations. Overall, this study emphasizes the need to use a wide range of observations for model validation as well as sufficient accounting of uncertainty in both models and measurements
Global analysis of night marine air temperature and its uncertainty since 1880: the HadNMAT2 Dataset

An updated version of the Met Office Hadley Centre’s monthly night marine air temperature dataset is presented. It is available on a 5˚ latitude-longitude grid from 1880 as anomalies relative to 1961-1990 calendar-monthly climatological average night marine air temperature (NMAT). Adjustments are made for changes in observation height; these depend on estimates of the stability of the near surface atmospheric boundary layer. In previous versions of the dataset, ad hoc adjustments were also made for three periods and regions where poor observational practice was prevalent. These adjustments are re-examined.  Estimates of uncertainty are calculated for every grid box and result from: measurement errors; uncertainty in adjustments applied to the observations; uncertainty in the measurement height and under-sampling. The new dataset is a clear improvement over previous versions in terms of coverage because of the recent digitization of historical observations from ships' logbooks. However, the periods prior to about 1890 and around World War 2 remain particularly uncertain and sampling is still sparse in some regions in other periods. A further improvement is the availability of uncertainty estimates for every grid box and every month. Previous versions required adjustments that were dependent on contemporary measurements of sea surface temperature (SST); to avoid these, the new dataset starts in 1880 rather than 1856. Overall agreement with variations of SST is better for the updated dataset than for previous versions, maintaining existing estimates of global warming and increasing confidence in the global record of temperature variability and change
Assessment of surface winds over the Atlantic, Indian, and Pacific Ocean sectors of the Southern Ocean in CMIP5 models: historical bias, forcing response, and state dependence

An assessment of the fifth Coupled Models Intercomparison Project (CMIP5) models' simulation of the near-surface westerly wind jet position and strength over the Atlantic, Indian and Pacific sectors of the Southern Ocean is presented. Compared with reanalysis climatologies there is an equatorward bias of 3.3° (inter-model standard deviation of ± 1.9°) in the ensemble mean position of the zonal mean jet. The ensemble mean strength is biased slightly too weak, with the largest biases over the Pacific sector (−1.4 ± 1.2 m/s, −19%). An analysis of atmosphere-only (AMIP) experiments indicates that 28% of the zonal mean position bias comes from coupling of the ocean/ice models to the atmosphere. The response to future emissions scenarios (RCP4.5 and RCP8.5) is characterized by two phases: (i) the period of most rapid ozone recovery (2000–2049) during which there is insignificant change in summer; and (ii) the period 2050–2098 during which RCP4.5 simulations show no significant change but RCP8.5 simulations show poleward shifts (0.33, 0.18 and 0.27°/decade over the Atlantic, Indian and Pacific sectors, respectively), and increases in strength (0.07, 0.08 and 0.15 m/s/decade, respectively). The models with larger equatorward position biases generally show larger poleward shifts (i.e. state dependence). This inter-model relationship is strongest over the Pacific sector (r = −0.91) and weakest over the Atlantic sector (r = −0.39). An assessment of jet structure shows that over the Atlantic sector jet shift is not clearly linked to indices of jet structure whereas over the Pacific sector the distance between the sub-polar and sub-tropical westerly jets appears to be important
A climatology of frozen-in anticyclones in the spring arctic stratosphere over the period 1960-2011

International audienceDuring springtime, following the stratospheric final warming, intrusions from low latitudes can become trapped at polar latitudes in long-lived anticyclones. Such "frozen-in" anticyclones (FrIACs) have occasionally been observed to persist as late as August, advected by summer easterlies. In this study, the high-resolution advection contour model MIMOSA is used to advect a pseudo-potential vorticity tracer. The model is driven by ERA-40 and the ERA-Interim reanalyses over the period 1960-2011. We first identify a remarkable FrIAC event in spring 2011. In addition, we developed a method to detect the characteristic size of low-latitude intrusions into the polar region at the time of the spring transition, over the period 1960-2011. Years are classified as either Type-A when the intrusions are small, or as Type-B when intrusions are large, potentially evolving into FrIACs. For a FrIAC to occur, we require an additional criterion based on the in-phase character of the core of the intrusions and the anticyclone. During the 52 analysed years, 9 events have been identified: 1 in the 1960s, 1 in the 1980s, 2 in the 1990s and 5 from 2002. FrIAC are predominantly long-lived intrusions, which occur in association with abrupt and early reversal to summer easterlies with a large heat flux pulse around the date of this wind reversal. Finally, the results are discussed in a climatological context
Meteorological regimes and accumulation patterns at Utsteinen, Dronning Maud Land, East Antarctica: Analysis of two contrasting years

Since February 2009, an automatic weather station (AWS) has been operating near Utsteinen nunatak, north of the Sør Rondane mountains, in Dronning Maud Land at the ascent to the East Antarctic plateau. This paper gives an assessment of meteorological conditions, radiative fluxes, and snow accumulation for the first two years of operation, 2009-2010, analyzed in terms of meteorological regimes. Three major meteorological regimes - cold katabatic, warm synoptic and transitional synoptic - are identified using cluster analysis based on five parameters derived from the AWS measurements (wind speed, specific humidity, near-surface temperature inversion, surface pressure, and incoming longwave flux indicative of cloud forcing). For its location, the relatively mild climate at Utsteinen can be explained by the high frequency of synoptic events (observed 41-48% of the time), and a lack of drainage of cold air from the plateau due to mountain sheltering. During the cold katabatic regime a strong surface cooling leads to a strong near-surface temperature inversion build-up. A large difference in accumulation is recorded by the AWS for the two years: 235 mm water equivalent (w.e.) in 2009 and 27 mm w.e. in 2010. Several large accumulation events during the warm synoptic regime occurring mainly in winter were responsible for the majority of 2009 accumulation. Mostly small accumulation events occurred during 2010, frequently followed by snow removal. This interannual variability in snow accumulation at the site is related to the intensity of the local synoptic events as recorded by meteorological regime characteristics.status: publishe
Aviation-induced cirrus and radiation changes at diurnal timescales

The radiative forcing from aviation-induced cirrus is derived from observations and models. \ud
The annual-mean diurnal cycle of airtraffic in the North Atlantic region (NAR) exhibits two peaks in early morning and afternoon with different peak times in the western and eastern parts of the NAR. The same "aviation fingerprint" is found in eight years (2004-2011) of Meteosat observations of cirrus cover and outgoing longwave radiation (OLR). The observations are related to airtraffic data with linear response models assuming the background atmosphere without aviation to be similar to that observed in the South Atlantic. \ud
The change in OLR is interpreted as aviation-induced longwave radiative forcing (LW RF). \ud
The data analysis suggests a LW RF of about 600—900 mW m-2 regionally. \ud
A detailed contrail-cirrus model for given global meteorology and airtraffic in 2006 gives similar results. The global RF is estimated from the ratio of global and regional RF as derived from three models. The extrapolation implies about 100--160 mW m-2 global LW RF. The models show large differences in the shortwave/longwave RF-magnitude ratio. \ud
One model computes a ratio of 0.6, implying an estimate of global net RF of about 50 (40-80) mW m-2.  Other models suggest smaller ratios, with less cooling during day, which would imply considerably larger net effects. The sensitivity of the results to the accuracy of the observations, traffic data, models and the estimated background is discussed
Atmospheric P deposition to the subtropical North Atlantic: sources, properties, and relationship to N deposition

Biogeochemical studies show that the surface waters of the subtropical North Atlantic are highly phosphorus (P) stressed. Human activity may exacerbate phosphorus stress by enhancing atmospheric nitrogen (N) deposition and raising N/P ratios in deposition. However, the magnitude of this effect is unclear, in part, because atmospherically deposited phosphorus sources are not well known, particularly the contribution from organic phosphorus. Here we report measurements of phosphorus in aerosols and wet deposition at Miami and Barbados. African dust is the major aerosol P source at both Miami and Barbados, containing ~880 ppm total phosphorus and ~70 ppm soluble reactive phosphorus (SRP). Organic compounds contribute, on average, 28%–44% of soluble phosphorus in precipitation. Because of dust transport seasonality, phosphorus inputs to the North Atlantic are expected to be highly variable with 2–10 times more P deposition during summer than winter. Pollution is also an important contributor to total and soluble phosphorus in Miami aerosols and deposition. Estimated SRP deposition in Barbados and Miami is 0.21 and 0.13 µmol m−2 d−1 phosphorus, respectively. Inorganic nitrogen in excess of Redfield ratio expectations in deposition was very different between the sites, totaling 21–30 and 127–132 µmol m−2 d−1 nitrogen in Barbados and Miami, respectively; the high deposition rates at Miami are linked to pollutants. Including soluble organic nitrogen and phosphorus halved the estimates of excess nitrogen in Barbados wet deposition. Thus, the organic phosphorus fraction is important in the assessment of the magnitude of biogeochemical change of the North Atlantic caused by atmospheric deposition
BLUE-based NO2 data assimilation at urban scale

International audienceWe aim at optimally combining air quality computations, from the Gaussian model ADMS Urban, and ground observations at urban scale. An ADMS simulation generated NO2 concentration fields across Clermont-Ferrand (France) down to street level, every 3 h for the full year 2008. A monitoring network composed of nine fixed stations provided hourly observations to be assimilated. Every 3 h, we compute the so-called BLUE (best linear unbiased estimator), which is a concentration field merging ADMS outputs and ground observations. Its error variance is supposed to be minimal under given assumptions regarding the errors on observations and model simulations. A key step lies in the modeling of error covariances between the computed NO2 concentrations across the city. We introduce a parameterized covariance which heavily relies on the road network. The covariance between two locations depends on the distance of each location to the road network and on the distance between the locations along the road network. Efficient parameters for the covariances are primarily chosen according to prior assumptions, χ2 diagnosis and leave-one-out cross-validations. According to the cross-validations, the improvements due to the assimilation seem moderately far from the observation network, but the root mean square error roughly decreases by 30-50% in the main city where the station density is high. The method is computationally tractable for the generation of improved concentration fields over a long period, or for day-to-day forecasts
Geomagnetic activity signatures in wintertime stratosphere wind, temperature, and wave response

We analyzed ERA-40 and ERA Interim meteorological re-analysis data for signatures of geomagnetic activity in zonal mean zonal wind, temperature, and Eliassen-Palm flux in the Northern Hemisphere extended winter (November–March). We found that for high geomagnetic activity levels, the stratospheric polar vortex becomes stronger in late winter, with more planetary waves being refracted equatorward. The statistically significant signals first appear in December and continue until March, with poleward propagation of the signals with time, even though some uncertainty remains due to the limited amount of data available ( ∼ 50 years). Our results also indicated that the geomagnetic effect on planetary wave propagation has a tendency to take place when the stratosphere background flow is relatively stable or when the polar vortex is stronger and less disturbed in early winter. These conditions typically occur during high solar irradiance cycle conditions or westerly quasi-biennial oscillation conditions
A new statistical approach to downscale wind speed distributions at a site in northern Europe

This paper explores a statistical regression approach to downscale large-scale global circulation model output to the wind speed distribution at the hub-height of tall wind turbines. The methodology is developed for Cabauw, using observational, ERA-Interim and ECHAM5 data. The regression analysis is based on the parameters of the probability distribution functions (pdfs) and includes a variable evaluation prior to the development of the statistical models. During winter ECHAM5 performs very well in representing the ERA-Interim wind speed pdf at hub-height. However, during summer, the hub-height wind speed pdf is not well represented by ECHAM5. A regression analysis shows that during summer-day the hub-height wind speed is strongly linked to the wind speed at higher, skillfully represented levels. The summer-day hub-height wind speed can therefore be skillfully predicted using wind speed pdf parameters of higher levels (R2 of the model using 500 m wind speed scale parameter as a predictor is 0.84). During the summer-night, the stable boundary layer is much shallower and the statistical model shows that solely the higher level wind speed is not able to skillfully predict the hub-height wind speed pdf (R2 of 0.59). Including temperature information in the downscaling model substantially improves the prediction of the summer-night hub-height wind speed pdf (R2 adjusted of 0.68).status: publishe
Testing the robustness of the anthropogenic climate change detection statements using different empirical models

This paper aims to test the robustness of the detection and attribution of anthropogenic climate change using four different empirical models that were previously developed to explain the observed global mean temperature changes over the last few decades. These studies postulated that the main drivers of these changes included not only the usual natural forcings, such as solar and volcanic, and anthropogenic forcings, such as greenhouse gases and sulfates, but also other known Earth system oscillations such as El Niño Southern Oscillation (ENSO) or the Atlantic Multidecadal Oscillation (AMO). In this paper, we consider these signals, or forced responses, and test whether or not the anthropogenic signal can be robustly detected under different assumptions for the internal variability of the climate system. We assume that the internal variability of the global mean surface temperature can be described by simple stochastic models that explore a wide range of plausible temporal autocorrelations, ranging from short memory processes exemplified by an AR(1) model to long memory processes, represented by a fractional differenced model. In all instances, we conclude that human-induced changes to atmospheric gas composition is affecting global mean surface temperature changes
Obtaining diverse behaviors in a climate model without the use of flux adjustments

A number of studies have set out to obtain a range of atmosphere and ocean model behavior by perturbing parameters in a single climate model (perturbed physics ensemble: PPE). Early studies used shallow layer slab ocean or flux-adjusted coupled ocean-atmosphere models to obtain a broad range of behavior as characterized by climate sensitivity. A recent study reports a relatively narrow range of sensitivities (2.2–3.2°C) in a PPE of 35 coupled models without flux adjustment, raising the question whether previous broad ranges were an artifact of the use of models that were not in top-of-atmosphere (TOA) energy balance. Moreover, no PPE experiment has reported a large spread of behavior of the ocean compared to that exhibited in a multi-model ensemble (MME) such as Coupled Model Intercomparison Project phase 3 (CMIP3). In this work, we randomly perturb model parameters of a coupled ocean-atmosphere general circulation model using a space-filling design containing 10,000 combinations. The ensemble is run over the distributed computing platform of climateprediction.net under fixed pre-industrial forcing without flux adjustment. We resample a second, 20,000-member, ensemble with perturbations conditioned on the TOA fluxes from the first ensemble to not drift significantly from a realistic base state while targeting a range of behavior. Models within the targeted ensemble show realistic regional control climates when compared to the CMIP3 ensemble, although there is a bias in global mean surface temperature. The range of predicted equilibrium climate sensitivities of the targeted ensemble is substantially smaller than that obtained with flux adjustment, but larger than the range in the CMIP3 ensemble or in the 35-model un-flux-adjusted PPE in a recent study mentioned above. The Atlantic meridional overturning circulation in the targeted ensemble exhibits a spread in strength as wide as that found in the CMIP3 ensemble. We conclude that flux adjustment is not a pre-requisite for obtaining a broad spread of behavior in a perturbed physics ensemble
Composition and hygroscopicity of the Los Angeles Aerosol: CalNex

The article of record as published may be found at http://dx.doi.org/10.1002/jgrd.50307Journal of Geophysical Research-Atmospheres, Vol. 118, pp. 3016-3036Aircraft-based measurements of aerosol composition, either bulk or single-particle,
and both subsaturated and supersaturated hygroscopicity were made in the Los Angeles
Basin and its outflows during May 2010 during the CalNex field study. Aerosol
composition evolves from source-rich areas in the western Basin to downwind sites in the
eastern Basin, evidenced by transition from an external to internal mixture, as well as
enhancements in organic O: C ratio, the amount of organics and nitrate internally mixed on
almost all particle types, and coating thickness on refractory black carbon (rBC). Transport
into hot, dilute outflow regions leads to significant volatilization of semivolatile material,
resulting in a unimodal aerosol comprising primarily oxygenated, low-volatility,
water-soluble organics and sulfate. The fraction of particles with rBC or soot cores is
between 27 and 51% based on data from a Single Particle Soot Photometer (SP2) and
Aerosol Time of Flight Mass Spectrometer (ATOFMS). Secondary organics appear to
inhibit subsaturated water uptake in aged particles, while CCN activity is enhanced with
photochemical age. A biomass-burning event resulted in suppression of subsaturated
hygroscopicity but enhancement in CCN activity, suggesting that BB particles may be
nonhygroscopic at subsaturated RH but are important sources of CCN. Aerosol aging and
biomass burning can lead to discrepancies between subsaturated and supersaturated
hygroscopicity that may be related to mixing state. In the cases of biomass burning aerosol
and aged particles coated with secondary material, more than a single parameter
representation of subsaturated hygroscopicity and CCN activity is needed
Vertical structure of aerosols, temperature, and moisture associated with an intense African dust event observed over the eastern Caribbean

The article of record as published may be located at http://dx.doi.org/10.1002/jgrd.50352An unusually intense African dust event affected a large area of the western Atlantic and
eastern Caribbean in early April 2010. Measurements made east of Barbados from the Center
for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter research aircraft
are used to characterize particle size distributions; vertical distributions of aerosols,
temperature, and moisture; and processes leading to the observed stratification in the
boundary layer. The vertical profiles of various aerosol characterizations were similar on
both days and show three layers with distinct aerosol and thermodynamic characteristics:
the Saharan Air Layer (SAL; ~2.2 km 500 m), a subcloud layer (SCL; surface to ~500m),
and an intermediate layer extending between them. The SAL and SCL display well-mixed
aerosol and thermodynamic characteristics; but the most significant horizontal and vertical
variations in aerosols and thermodynamics occur in the intermediate layer. The aerosol
variability observed in the intermediate layer is likely associated withmodification by shallow
cumulus convection occurring sometime in the prior history of the air mass as it is advected
across the Atlantic. A comparison of the thermodynamic structure observed in the event from
its origin over Africa with that when it reached Barbados indicates that the lower part of
the SAL was moistened by surface fluxes as the air mass was advected across the Atlantic.
Mixing diagrams using aerosol concentrations and water vapor mixing ratios as conserved
parameters provide insight into the vertical transports and mixing processes that may explain
the observed aerosol and thermodynamic variability in each layer