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This work aims to characterize a new class of automaton with input as multisets. First, we introduce two finite monoids through different congruence relations on multiset associated with lattice-valued multiset finite automata and show that they are isomorphic to each other. Next, we present the quotient structure of lattice-valued multiset finite automata by defining an admissible relation on the set of states of a given lattice-valued multiset finite automata. Then we show that there is an isomorphism between lattice-valued multiset finite automata and the quotient structure of another lattice-valued multiset finite automata. Finally, we introduce the concept of reachability, observability (coreachability), and response maps of lattice-valued multiset finite recognizer. Interestingly, we show that the lattice-valued response map of a lattice-valued multiset finite recognizer leads us to provide a characterization of a lattice-valued multiset regular language.

Temperatures and pressures from high explosive detonations far exceed atmospheric conditions in typical combustion reactions, and consequently, detonation soot forms with physiochemical properties distinct from soot formed by combustion. In this study, samples of detonation soot from two high explosives, PBX 9502 and Composition B‐3, were analyzed. Ice nucleation experiments on soot collected after controlled detonations were conducted in the laboratory to probe immersion and contact mode freezing. Samples nucleated ice at temperatures warmer than commercially available nanodiamonds, which has a mean nucleation temperature of −20.7°C. Ice nucleation rate coefficients increase rapidly by two to three orders of magnitude below −20°C for every sample. Size‐selected 137 μm diameter particles produced during detonation in an ambient air atmosphere yield bimodal distributions of freezing temperature with primary and secondary nucleation modes centered at −20°C and −13°C, respectively. The presence of a secondary mode allows for enhanced ice nucleation rate coefficients (one to two orders of magnitude greater than samples without a secondary mode) at temperatures outside the influence of the primary mode (>−17°C). Given the observed onset nucleation temperatures of −9.2°C, our results imply that detonation soot of the type studied here would only need to reach an altitude of approximately 4 km to facilitate ice formation. Tiny suspended particles can modify the earth's energy balance. Some of these particles influence cloud formation through a process called the indirect effect of aerosol. One aspect of the indirect effect involves a subset of aerosol known as ice nucleating particles (INPs) that enhance ice formation in cold regions of the atmosphere. Because of the impact of INPs on climate, it is important to identify the types of aerosols that efficiently form ice. One understudied aerosol is a unique soot with distinct properties that is formed by the extreme temperatures and pressures achieved within high explosive detonations. This detonation soot can be lofted high into the atmosphere where it could impact ice formation. The ice nucleation activity of detonation soot is examined here for the first time. Through experimentation, we measured the freezing temperature of detonation soot originating from two different high explosives, PBX‐9502 and Composition B‐3. Detonation soot does act as an INP with a small portion of efficient particles. Our results indicate that detonation soot lofted into the atmosphere could increase the number of INPs around the globe and promote ice nucleation at warmer temperatures and lower altitudes in regions lacking more efficient INPs. High explosive detonation soot particles act as ice nucleating particles with a small percentage activating as warm as −9.2°CDetonations in oxygen‐rich environments generate more effective ice nucleating particles than those generated in oxygen‐poor environmentsCuprous oxide and diamond are moderately effective ice nucleating particles but less effective than the detonation soot samples High explosive detonation soot particles act as ice nucleating particles with a small percentage activating as warm as −9.2°C Detonations in oxygen‐rich environments generate more effective ice nucleating particles than those generated in oxygen‐poor environments Cuprous oxide and diamond are moderately effective ice nucleating particles but less effective than the detonation soot samples

Biomass burning emissions have substantially increased with continued warming and drying in the southwestern U.S., impacting air quality and atmospheric processes. To better quantify impacts of biomass burning aerosols, an extensive laboratory study of fresh smoke emissions was conducted at Los Alamos National Laboratory. Laboratory burn experiments with selected native and invasive southwestern U.S. fuels were used to elucidate the role of fuel type, chemical composition, and ignition method on the hygroscopicity of smoke. Here we focus on a custom controlled relative humidity (RH) nephelometry system using the direct measurement of aerosol light scattering with two nephelometers—one at dry conditions and one at a controlled high RH (RH ~ 85%). Aerosol hygroscopicity was highly variable with the enhancement in light scattering coefficient in the range of 1.02 < f(RH = 85%) < 2.1 and corresponding to the kappa parameter (κneph) ranging from ~0 to 0.18. Hygroscopicity is determined primarily by the fuel's inorganic ion content. For example, invasive halophytes with high inorganic salt content exhibit much greater water uptake than native coniferous species with low inorganic content. Combustion temperature and phase, flaming or smoldering, play a secondary role in the water uptake of smoke. High‐temperature ignition methods create flaming conditions that enhance hygroscopicity while lower‐temperature smoldering conditions diminish hygroscopicity. Our results construct an empirical relation between κnephand the inorganic content of the fuel and smoke to predict water uptake. Biomass smoke hygroscopic response is variable, with variability driven by fuel chemical composition and ignition methodConiferous evergreen species are weakly hygroscopic while salt‐tolerant species containing inorganic ions are strongly hygroscopicA framework for smoke hygroscopicity based on lab measurements shows consistent behavior when applied to ambient smoke measurements

We present a case study based on balloon‐borne ozone measurements during the SouthEast American Consortium for Intensive Ozonesonde Network Study in August–September 2013. Data from Socorro, NM (34°N, 107°W) show a layer of anomalously low ozone in the upper troposphere (UT) during 8–14 August. Back trajectories, UT jet analyses, and data from the Microwave Limb Sounder (MLS) on the Aura satellite indicate that this feature originated from the marine boundary layer in the eastern/central tropical Pacific, where several disturbances and one hurricane (Henriette) formed within an active region of the Intertropical Convergence Zone in early August 2013. The hurricane and nearby convection pumped boundary layer air with low ozone (20–30 ppbv) into the UT. This outflow was advected to North America 3–5 days later by a strong subtropical jet, forming a tongue of low ozone observed in MLS fields and a corresponding layer of low ozone in Socorro vertical profiles. Impacts of a tropical cyclone are seen in tropospheric ozone at midlatitudes

The reaction of OH with NO2 is central to atmospheric chemistry, and its dynamics can be constrained by studying the kinetics of isotopically labeled ¹⁸OH with NO2. This labeling opens an isotopic scrambling pathway in the reaction coordinate for nitric acid formation, providing experimental constraints on the high-pressure behavior of the reaction with data obtained at low pressures. This reaction, however, is complicated by the presence of a second product isomer, peroxynitrous acid (HOONO), which does not have a scrambling pathway. We present data for the reaction of ¹⁸OH with NO2 at room temperature between 4 and 200 Torr. The reaction is rapid and independent of pressure. We also locate the H-atom isomerization transition state and show that the isomerization rate constant is at least an order of magnitude faster than adduct dissociation. These results allow us to accurately constrain the formation rate constant of HONO2, which is a factor of 5 slower than the observed OH removal rate constant at high pressure. We conclude that the difference is due to HOONO formation. Our conclusion is consistent with recent theoretical predictions of this branching, and also provides the only self-consistent reconciliation of the high-pressure data with the remainder of the experimental data set.

Effects of recommended rate parameter changes in the NASA JPL-2000 evaluation from JPL-94 values on local ozone concentrations in a 2-D model are predicted using local sensitivity analysis results from the LLNL 2-D diurnally averaged model. Ozone decreases of 5% in the middle stratosphere and 10% increases near the tropopause and upper troposphere are indicated. Altered NOx kinetics are largely responsible for these changes, and increased model NOx levels and ozone depletion from stratospheric aircraft are also expected according to sensitivity analysis. Effects of specific changes, such as the nitric acid formation rate, are examined. New error bars on rate parameters in the evaluation are propagated by the sensitivity coefficients to derive revised kinetics uncertainties for the model ozone calculations at several altitudes, latitudes, and seasons. Middle-upper stratospheric ozone uncertainties of 12% from the catalytic photochemistry are indicated, increasing in the lower stratosphere.

Compared to measurements, atmospheric models have overestimated [ClO]/[HCl] and [ClONO2]/[HCl] in the upper and middle stratosphere, respectively, and consequently have predicted lower [O3] than observed. It is believed that a minor branch that produces HCl from the OH + ClO reaction can account for these discrepancies. Recent laboratory studies have indicated a 5 ± 2% yield for this channel.¹ By performing box model sensitivity analysis calculations using the output from the LLNL-2D diurnally averaged stratospheric model, we quantitatively confirm that this reaction is the most prominent contributor to the model [ClO]/[HCl] and [ClONO2]/[HCl] uncertainties in the upper stratosphere and that it is most effective in increasing [O3] at higher latitudes during winter. Using theoretical methods, we examine the OH + ClO reaction mechanism, in which an initially energized HOOCl* complex is formed that can dissociate to HO2 + Cl (major) or HCl + O2(¹Δ) (minor) products, redissociate to reactants, or be collisionally stabilized. Multichannel RRKM calculations guided by ab initio electronic structure calculations and the available kinetic data are presented. We show that the four-center transition state (TS3) for HCl production must lie at least 2 kcal/mol below the reactants for the HCl yield to exceed 5%. Our ab initio relative energy of −2.3 ± 3 kcal/mol for TS3 demonstrates that this minor HCl channel is mechanistically feasible. We also predict small pressure, temperature, and H/D isotopic dependencies for the minor channel yield and insignificant rates of complex stabilization under atmospheric conditions.

Gas-phase hydrogen (H) abstractions from molecules by free radicals have been studied extensively. They form the simplest class of elementary reactions and also play a key role in atmospheric chemistry and so are the centerpiece of models of reactivity. Despite intense scrutiny, two fundamental mechanistic issues remain unresolved:  (1) Do H abstractions proceed directly or indirectly? (2) Do thermodynamic or electronic interactions determine their reaction barrier? The thermoneutral identity reaction, OH + H2O → H2O + OH, provides an excellent opportunity to answer these questions. Several theoretically predicted H2O−HO complexes raise the possibility of an indirect mechanism, while no thermodynamic forcing influences the reaction barrier. To examine the various reactivity models, the isotopic scrambling reactions¹⁸OH + H2¹⁶O → H2¹⁸O +¹⁶OH and ¹⁶OD + H2¹⁶O → H¹⁶OD +¹⁶OH are studied in a high-pressure flow reactor. The measured rate constants are (2.3 ± 1.0) × 10^-13 exp[−(2100 ± 250)/T] cm³ molecule^-1 s^-1 over the range 300−420 K ((2.2 ± 1.0) × 10^-16 at 300 K) and (3 ± 1.0) × 10^-16 cm³ molecule^-1 s^-1 at 300 K, respectively. The similarity between the room temperature rates indicates a small secondary isotope effect. While the strong temperature dependence reveals that the predicted complexes do not stabilize the isotope exchange transition state sufficiently to bring its energy below the reactants, the small preexponential factor indicates that the complexes pose entropic constraints. Therefore, the reaction mechanism appears to be indirect. This is clarified by tracing the evolution of reagent electronic interactions and geometrical transformations along the reaction path. Activation energies of isotope exchange reactions are used to constrain the thermoneutral intercept for themodynamically based reactivity models. These thermochemical models are shown to be unreliable. However, a correlation between theoretical (ab initio) and experimental reaction barriers does capture gross reactivity trends. These measurements also exclude kinetic fractionation by OH as an important contributor to the isotopic fractionation of water in the earth's atmosphere.

We provide an analysis of Greenland temperature records to compare the current (1995–2005) warming period with the previous (1920–1930) Greenland warming. We find that the current Greenland warming is not unprecedented in recent Greenland history. Temperature increases in the two warming periods are of a similar magnitude, however, the rate of warming in 1920–1930 was about 50% higher than that in 1995–2005.