172,467 research outputs found
Midlatitude ClO during the maximum atmospheric chlorine burden : in situ balloon measurements and model simulations
No full textChlorine monoxide (ClO) plays a key role in stratospheric ozone loss processes at midlatitudes. We present two balloonborne in situ measurements of ClO conducted in northern hemisphere midlatitudes during the period of the maximum of total inorganic chlorine loading in the atmosphere. Both ClO measurements were conducted on board the TRIPLE balloon payload, launched in November 1996 in Le´on, Spain, and in May 1999 in Aire sur l’Adour, France. For both flights a ClO daylight and night time vertical profile could be derived over an altitude range of approximately 15–31 km. ClO mixing ratios are compared to model simulations performed with the photochemical box model version of the Chemical Lagrangian Model of the Stratosphere (CLaMS). Simulations along 24-h backward trajectories were performed to study the diurnal variation of ClO in the midlatitude lower stratosphere. Model simulations for the flight launched in Aire sur l’Adour 1999 show a good agreement with the ClO measurements. For the flight launched in Le´on 1996, a similar good agreement is found, except at around ~ 650 K potential temperature (~26km altitude). However, a tendency is found that for solar zenith angles greater than 86°–87° the simulated ClO mixing ratios substantially overestimate measured ClO by approximately a factor of 2.5 or more for both flights. Therefore we conclude that no indication can be deduced from the presented ClO measurements that substantial uncertainties exist in midlatitude chlorine chemistry of the stratosphere. An exception is the situation at solar zenith angles greater than 86°–87° where model simulations substantial overestimate ClO observations
HCl and ClO in activated Arctic air; first retrieved vertical profiles from TELIS submillimetre limb spectra
No full textThe first profile retrieval results of the Terahertz and submillimeter Limb Sounder (TELIS) balloon instrument
are presented. The spectra are recorded during a 13-h
balloon flight on 24 January 2010 from Kiruna, Sweden. The
TELIS instrument was mounted on the MIPAS-B2 gondola
and shared this platform with the Michelson Interferometer
for Passive Atmospheric Sounding (MIPAS) and the mini-
Differential Optical Absorption Spectroscopy (mini-DOAS)
instruments. The flight took place within the Arctic vortex
at an altitude of 34 km in chlorine activated air, and both active (ClO) and inactive chlorine (HCl) were measured
over an altitude range of respectively 16�32 km and 10�
32 km. In this altitude range, the increase of ClO concentration levels during sunrise has been recorded with a temporal resolution of one minute. During the daytime equilibrium, a maximum ClO level of 2.1�±0.3 ppbv has been observed at an altitude of 23.5 km. This equilibrium profile is validated against the ClO profile by the satellite instrument Microwave Limb Sounder (MLS) aboard EOS Aura. HCl profiles have been determined from two different isotopes â�� H35Cl and H37Cl â�� and are also validated against MLS. The precision of all profiles is well below 0.01 ppbv and the overall accuracy is therefore governed by systematic effects. The total uncertainty of these effects is estimated to be maximal 0.3 ppbv for ClO around its peak value at 23.5 km during the daytime equilibrium, and for HCl it ranges from 0.05 to 0.4 ppbv, depending on altitude. In both cases the main uncertainty stems from a largely unknown non-linear response in the detector
First remote sensing measurements of ClOOCl along with ClO and ClONO2 in activated and deactivated Arctic vortex conditions using new ClOOCl IR absorption cross sections
No full textAbstract. Active chlorine species play a dominant role in
the catalytic destruction of stratospheric ozone in the polar
vortices during the late winter and early spring seasons. Recently,
the correct understanding of the ClO dimer cycle was
challenged by the release of new laboratory absorption cross
sections (Pope et al., 2007) yielding significant model underestimates
of observed ClO and ozone loss (von Hobe et al.,
2007). Under this aspect, nocturnal Arctic stratospheric limb
emission measurements carried out by the balloon version
of the Michelson Interferometer for Passive Atmospheric
Sounding (MIPAS-B) from Kiruna (Sweden) on 11 January
2001 and 20/21 March 2003 have been reanalyzed with regard
to the chlorine reservoir species ClONO2 and the active
species, ClO and ClOOCl (Cl2O2). New laboratory measurements
of IR absorption cross sections of ClOOCl for various
temperatures and pressures allowed for the first time the retrieval
of ClOOCl mixing ratios from remote sensing measurements.
High values of active chlorine (ClOx) of roughly
2.3 ppbv at 20 km were observed by MIPAS-B in the cold
mid-winter Arctic vortex on 11 January 2001. While nighttime
ClOOCl shows enhanced values of nearly 1.1 ppbv at
20 km, ClONO2 mixing ratios are less than 0.1 ppbv at this
altitude. In contrast, high ClONO2 mixing ratios of nearly
2.4 ppbv at 20 km have been observed in the late winter Arctic
vortex on 20 March 2003. No significant ClOx amounts
are detectable on this date since most of the active chlorine
has already recovered to its main reservoir species ClONO2.
The observed values of ClOx and ClONO2 are in line with
the established polar chlorine chemistry. The thermal equilibrium
constants between the dimer formation and its dissociation,
as derived from the balloon measurements, are
on the lower side of reported data and in good agreement
with values recommended by von Hobe et al. (2007). Calculations
with the ECHAM/MESSy Atmospheric Chemistry
model (EMAC) using established kinetics show similar chlorine
activation and deactivation, compared to the measurements
in January 2001 and March 2003, respectively
Polar processing and development of the 2004 Antarctic ozone hole: First results from MLS on Aura
No full textThe Microwave Limb Sounder (MLS) on Aura is providing an extensive data set on stratospheric winter polar processing, including the first daily global observations of HCl, together with simultaneous measurements of ClO, HNO3, H2O, O3, N2O, and temperature (among others). We present first results charting the evolution of these quantities during the 2004 Antarctic late winter. MLS observations of chlorine deactivation and ozone loss during this period are shown to be consistent with results from the SLIMCAT chemical transport model
Theoretical study on the ClO/ClO- system electron-transfer reactivity by the golden-rule
No full textThe structures, properties and electron transfer reactivity of the ClO/ClO- coupling system are studied in this paper at ab initio (UHF and UMP2) levels and the Density Functional Theory (DFT: UB3LYP, UB3P86, UB3PW91) levels employing 6311 + G(3df) basis set and on the basis of the Golden-rule of the time-dependent perturbation theory. Investigations indicate that the results obtained using the UB3LYP method employing 6-311 + G(3df) basis set is in excellent agreement with the experiment. For this coupling system, six stable coupling modes have been found which correspond to six different encounter complexes and denote six different electron transfer mechanism: four O-O directly linked structures (one collinear: D-h, one anti-parallel: C-s, two twist: C-2) and two Cl-O linked structures (cis- and anti- C-s structures). The activation energies, the stabilization energies and the electronic coupling matrix elements have also been calculated for the electron transfer reactions via these six different mechanism at the UB3LYP/6-311 + G(3df) level, and then the electron transfer rates are determined at the same level. The most favorable coupling mode to the electron transfer is the anti-parallel mechanism. The averaged electron transfer rate is about 5.58 X 10(11) M-1 s(-1). It is also implied that the B3LYP method can give more reasonable results for the electron transfer reactivity of this system. (C) 2003 Elsevier B.V. All rights reserved
Golden-rule treatment on the ClO/ClO+ electron-transfer system
No full textThe structures, properties and electron transfer reactivity of the ClO/ClO+ coupling system are studied in this paper at ab initio (HF and MP2) levels and the density functional theory (DFT: B3LYP, B3P86, B3PW91) levels employing 6311 + G(3df) basis set and on the basis of the golden-rule of the time-dependent perturbation theory. Investigations indicate that the results got from the B3LYP method employing 6-311 + G(3df) basis set is in excellent agreement with the experiment. The activation energies, the stabilization energies and the electronic coupling matrix elements have also been calculated by using the B3LYP/6-311 + G(3df) method, and then the electron transfer rates are determined at this level. The electronic coupling matrix element of EC.6 is very small, only 0.03 kcal/mol, while that of EC.7 is the biggest, being 12.41 kcal/mol, the corresponding electron transfer rate is also the fastest among these seven encounter complexes. The averaged electron transfer rate is about 1.672 X 10(11) M-1 s(-1). It is indicated that the structures optimized by B3LYP method are more reliable than the results got from the other four methods. It also testified that the electronic coupling matrix element is the vital factor that significantly affects the electron transfer rate. (C) 2003 Elsevier B.V. All rights reserved
BRAIN id: NER135 – pollen dataset
No full textPoviglio - PVG C-S1 (RE, N Italy).
Dataset including pollen counts from sediment samples collected from the near-site core (44°52′32′′ N, 10°34′42′′ E, 21 m asl; chronology: about 15000 years from the present - chronology under validation) within the SUCCESSO-TERRA Project (PRIN-20158KBLNB). The dataset was created as part of the National Biodiversity Future Center (NBFC, Palermo, Italy). The site is included in the BRAIN database (https://brainplants.successoterra.net/; site id: NER135)
Data for: THE EFFECT OF PRICE REGULATION ON ENERGY IMBALANCES: A DID DESIGN
No full textData and do files to replicate the tables and results of the paper-Regressions have been elaborated using the program Stata.-The main file that runs the results is named “do_file_replicate_tables.do”.-The data used in the paper are reported in the files named “dataset_EE_1.dta” (time-series), “dataset_EE_2.dta” (panel for DiD with TSOFE and market imbalance for the Macrozone South) and “dataset_EE_3.dta” (panel for DiD with TSOFE and market imbalance for the Macrozones South and North)-Code to generate results is organized in order to replicate the tables of the paper. The do file reports the number and the title of the tables reported in the manuscriptHOW TO RUN / SETUP: 1.Save data (.dta) and do files (.do) in a folder in your pc (C:).2.Open “do_file_replicate_tables.do” using the programme stata.3.put your directory (main folder where all files are stored) in the do_file “do_file_replicate_tables.do” within the quotations marks (cd "C:")Notes: - Code is commented to run main analysis given cleaned data sets.- The directory of the pc where files are stored needs to be defined
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