Mario J. Molina

Universidad Católica Silva Henríquez

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L. T. Molina

Molina Center for Energy and the Environment

174

Rainer Volkamer

Cooperative Institute for Research in Environmental Sciences

C. E. Kolb

Aerodyne Research

Renyi Zhang

Texas A&M University

B. de Foy

UCLouvain Saint-Louis Brussels

Anatoli Bogdan

University of Helsinki

S. C. Herndon

Aerodyne Research

J. L. Jiménez

Cooperative Institute for Research in Environmental Sciences

John T. Jayne

Aerodyne Research

M. Zavala

San Diego State University, Imperial Valley Campus

Cooperative Institutions

Massachusetts Institute of Technology

101

Texas A&M University

Chinese Academy of Sciences

University of California, San Diego

University of Colorado Boulder

Cooperative Institute for Research in Environmental Sciences

Universidad Nacional Autónoma de México

Pacific Northwest National Laboratory

Aerodyne Research

California Institute of Technology

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Different freezing behavior of millimeter- and micrometer-scaled (NH₄)₂SO₄/H₂O droplets

Journal of Physics Condensed Matter (2010)

Anatoli Bogdan Mario J. Molina Heikki Tenhu E. Mayer E. Bertel

Although the freezing of aqueous solutions is important for nature and different branches of science and freeze-applications, our understanding of the freezing process is not complete. For example, numerous measurements of micrometer-scaled (NH(4))(2)SO(4)/H(2)O droplets report one freezing event below the eutectic point. However, measurements of larger millimeter-scaled droplets reveal two freezing events: the freezing out of ice and subsequent freezing of a residual freeze-concentrated solution. To resolve this apparent contradiction we performed numerous calorimetric measurements which indicate that the freezing of a residual solution of millimeter-scaled 5-38 wt% (NH(4))(2)SO(4) droplets occurs mainly between ∼ 210 and 225 K. We also find that micrometer-scaled droplets produce one freezing event which is within or in the vicinity of the ∼ 210-225 K region. This fact and the analysis of thermograms suggest that the residual solution of micrometer-scaled droplets may partly crystallize simultaneously with ice and partly transform to glass at T(g)≈172 K. Our results suggest for the first time that the size of (NH(4))(2)SO(4)/H(2)O droplets may affect the number of freezing events below the eutectic point.

Micrometer

Supercooling

Freezing behavior

Ice formation

10.1088/0953-8984/23/3/035103

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Citations (7)

Chemical kinetics and photochemical data for use in stratospheric modeling: Evaluation number 11

Stanley P. Sander Randall R. Friedl W. B. DeMore D. M. Golden Michael J. Kurylo

This is the eleventh in a series of evaluated sets of rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation. The primary application of the data is in the modeling of stratospheric processes, with special emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena.

Atmospheric chemistry

Eleventh

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Citations (384)

LA QUÍMICA ESTÁ EN TODO, NUEVA SALA INTERACTIVA

Gaceta UNAM (2010-2015) (2011)

Gustavo Ayala Mario J. Molina Eduardo Bárzana

LAS SUSTANCIAS QUIMICAS, SUS PROPIEDADES E INTERACCIONES SON RESPONSABLES DE LOS OBJETOS QUE COMUNMENTE USAMOS. EN CUALQUIER SITUACION LA QUIMICA ESTA PRESENTE, DESDE EL INSTRUMENTO MAS AVANZADO DE UNA NAVE ESPACIAL HASTA LA FUNCION MAS BASICA DEL CUERPO HUMANO; EN LOS MEDICAMENTOS QUE AYUDAN A PREVENIR Y CURAR ENFERMEDADES, ALIMENTOS, PINTURA DE LA ESCUELA, APARATOS EN CASA O LA ROPA.

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Nucleation rates of nitric acid dihydrate in 1∶2 HNO₃/H₂O solutions at stratospheric temperatures

Geophysical Research Letters (2000)

D. Salcedo L. T. Molina Mario J. Molina

Nucleation rates of nitric acid dihydrate (NAD) in 1∶2 HNO 3 /H 2 O solutions between 194 and 183 K were measured by observing the freezing behavior of liquid drops with 7 – 33 µm diameter and with concentration of 64 weight percent HNO 3 using an optical microscopy technique. The nucleation rate increases from 3.1×10 5 cm −3 s −1 at 194 K to 1.3x10 9 cm −3 s −1 at 183 K. These results suggest that NAD might not nucleate homogeneously in binary or quasi‐binary nitric acid stratospheric aerosols in relevant time scales.

Nitric acid

10.1029/1999gl010991

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Assessing the effects of anthropogenic aerosols on Pacific storm track using a multiscale global climate model

Proceedings of the National Academy of Sciences (2014)

Yuan Wang Minghuai Wang Renyi Zhang S. J. Ghan Yun Lin

Significance Increasing levels of air pollutants in Asia have recently drawn considerable attention, but the effects of Asian pollution outflows on regional climate and global atmospheric circulation remain to be quantified. Using a multiscale global aerosol–climate model (GCM), we demonstrate long-range transport of the Asian pollution, large resulting variations in the aerosol optical depth, cloud droplet number concentration, and cloud and ice water paths; enhanced shortwave and longwave cloud radiative forcings; and increased precipitation and poleward heat transport. Our work provides, for the first time to the authors’ knowledge, a global multiscale perspective of the climatic effects of pollution outflows from Asia. The results reveal that the multiscale modeling framework is essential in simulating the aerosol invigoration effect of deep convective cloud systems by a GCM.

Shortwave

Longwave

Shortwave radiation

Diurnal cycle

10.1073/pnas.1403364111

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Citations (174)

Secondary organic aerosol formation from acetylene (C<sub>2</sub>H<sub>2</sub>): seed effect on SOA yields due to organic photochemistry in the aerosol aqueous phase

Rainer Volkamer Paul J. Ziemann Mario J. Molina

Abstract. The lightest Non Methane HydroCarbon (NMHC), i.e. acetylene (C2H2) is found to form secondary organic aerosol (SOA). Contrary to current belief, the number of carbon atoms, n, for a NMHC to act as SOA precursor is lowered to n=2 here. The OH-radical initiated oxidation of C2H2 forms glyoxal (CHOCHO) as the highest yield product, and >99% of the SOA from C2H2 is attributed to CHOCHO. SOA formation from C2H2 and CHOCHO was studied in a photochemical and a dark simulation chamber. Further, the experimental conditions were varied with respect to the chemical composition of the seed aerosol, mild acidification with sulphuric acid (SA, 3<pH<4), and relative humidity (10<RH<90%). The rate of SOA formation is found enhanced by several orders of magnitude in the photochemical system. The SOA yields (YSOA) ranged from 1% to 20% and did not correlate with the organic mass portion of the seed, but increased linearly with liquid water content (LWC) of the seed. For fixed LWC, YSOA varied by more than a factor of five. Water soluble organic carbon (WSOC) photochemistry in the liquid water associated with internally mixed inorganic/WSOC seed aerosols is found responsible for this seed effect. WSOC photochemistry enhances the SOA source from CHOCHO, while seeds containing amino acids (AA) and/or SA showed among the lowest of all YSOA values, and largely suppress the photochemical enhancement on the rate of CHOCHO uptake. Our results give first evidence for the importance of heterogeneous photochemistry of CHOCHO in SOA formation, and identify a potential bias in the currently available YSOA data for other SOA precursor NMHCs. We demonstrate that SOA formation via the aqueous phase is not limited to cloud droplets, but proceeds also in the absence of clouds, i.e. does not stop once a cloud droplet evaporates. Atmospheric models need to be expanded to include SOA formation from WSOC photochemistry of CHOCHO, and possibly other α-dicarbonyls, in aqueous aerosols.

Acetylene

Glyoxal

Isoprene

10.5194/acpd-8-14841-2008

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Citations (11)

Temperature dependence of OH diffusion in air and He

Geophysical Research Letters (2009)

Yong Liu А. В. Иванов Mario J. Molina

Although accurate knowledge of OH diffusion under atmospheric conditions is important, only one experimental study has been carried out at room temperature. Here, we report laboratory measurements of the OH diffusion coefficient in He and in a mixture of He and air over the range 218–318 K, using a temperature‐controlled flow tube coupled to a low‐pressure chemical ionization mass spectrometer. The results, which show a strong, almost square dependence of the diffusion coefficient on temperature in He and air, are consistent with predictions obtained from our theoretical calculations for diffusion of its polar diffusive analogue, H 2 O, using the 6–12 Lennard‐Jones potential model with the collision parameters of water. This supports our hypothesis that the diffusion of OH can be accurately represented in the atmosphere by water, its polar diffusive analogue.

Atmospheric temperature range

10.1029/2008gl036170

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Citations (20)

Stratospheric Ozone Chemistry

Springer eBooks (1998)

Mario J. Molina

Montreal Protocol

Ozone Depletion

10.1007/978-1-4615-5585-8_2

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Citations (3)

Flow Tube Studies of Gas Phase Chemical Processes of Atmospheric Importance

Mario J. Molina

The objective of this project is to conduct measurements of elementary reaction rate constants and photochemical parameters for processes of importance in the atmosphere. These measurements are being carried out under temperature and pressure conditions covering those applicable to the stratosphere and upper troposphere, using the chemical ionization mass spectrometry turbulent flow technique developed in our laboratory. The next section summarizes our research activities during the first year of the project, and the section that follows consists of the statement of work for the third year. Additional details concerning the projects listed in the statement of work were described in our original proposal.

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Atmospheric chemistry

Section (typography)

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Satellite-derived land surface parameters for mesoscale modelling of the Mexico City basin

Atmospheric chemistry and physics (2006)

B. de Foy L. T. Molina Mario J. Molina

Abstract. Mesoscale meteorological modelling is an important tool to help understand air pollution and heat island effects in urban areas. Accurate wind simulations are difficult to obtain in areas of weak synoptic forcing. Local factors have a dominant role in the circulation and include land surface parameters and their interaction with the atmosphere. This paper examines an episode during the MCMA-2003 field campaign held in the Mexico City Metropolitan Area (MCMA) in April of 2003. Because the episode has weak synoptic forcing, there is the potential for the surface heat budget to influence the local meteorology. High resolution satellite observations are used to specify the land use, vegetation fraction, albedo and surface temperature in the MM5 model. Making use of these readily available data leads to improved meteorological simulations in the MCMA, both for the wind circulation patterns and the urban heat island. Replacing values previously obtained from land-use tables with actual measurements removes the number of unknowns in the model and increases the accuracy of the energy budget. In addition to improving the understanding of local meteorology, this sets the stage for the use of advanced urban modules.

Albedo (alchemy)

Forcing (mathematics)

MM5

Urban Heat Island

10.5194/acp-6-1315-2006

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Citations (56)