Strong Inverse Temperature Research Articles

Modeling the Air Pollution and Aerosol‐PBL Interactions Over China Using a Variable‐Resolution Global Model

AbstractModeling air quality has always been a challenge in global models constrained by coarse grids. Here, the variable‐resolution Community Atmosphere Model with full chemistry based on the scalable spectral element (SE) dynamical core (MUSICAv0) is applied in simulating air pollution with a finer grid resolution of ∼0.25° over East Asia (SE_VR), in contrast to the same model with a uniform resolution of ∼1.0° (SE_UR). Two nudging experiments and four free‐running experiments are conducted to investigate the capabilities of SE_VR in modeling the air pollution and aerosol‐planetary boundary layer (PBL) interactions over China. Results show the regional refinement in SE_VR is essential for simulating haze events over complex terrain areas attributed to its better performance in representing the local vertical and horizontal dispersion conditions. SE_VR shows prominent advantages over SE_UR in simulating surface ozone because of better resolving spatial segregation of NOx and volatile organic compounds (VOC) chemical regimes and subsequently representing more detailed chemical processes related to ozone formation, although the model generally overestimates surface ozone over China. Further analysis of SE_VR shows the daytime radiative effect of black carbon (BC) aerosols lowers PBL height by 12.0% (17.9%), and leads to an increase of PM2.5 by 14.5% (10.8%) under the moderate (severe) air pollution conditions over Sichuan Basin. However, SE_UR has deficiencies in simulating BC‐PBL interactions due to its inability to reproduce the strong inverse temperature structure caused by BC aerosols in the lower atmosphere layer. Our results highlight the value of variable‐resolution global models for simulating air pollution and its interactions with climate.

Metabolomic Markers of Storage Temperature and Time in Pasteurized Milk.

The current date labeling system for pasteurized milk is based on the predicted growth of spoilage microorganisms, but inherent inaccuracies and the inability to account for environmental factors (e.g., temperature fluctuations) contribute to household and retail food waste. Improved shelf-life estimation can be achieved by monitoring milk quality in real-time. In this study, we identify and quantify metabolites changing over storage temperature and time, the main factors affecting milk stability. Pasteurized 2% fat milk was stored at 4, 10, 15, and 20 °C. Metabolite change was analyzed using untargeted and targeted nuclear magnetic resonance (NMR) metabolomics approaches. Several metabolites correlated significantly to storage time and temperature. Citric acid decreased linearly over time at a temperature-dependent rate. Ethanol, formic acid, acetic acid, lactic acid, and succinic acid increased non-linearly after an initial period of minimal increase. Butyric acid exhibited strong inverse temperature dependencies. This study provides the first analysis of the effect of time and temperature on the concentration of key metabolites during milk storage. Candidate molecules for shelf-life monitoring have been identified, and the results improve our understanding of molecular changes during milk storage. These results will inform the development of real-time shelf-life indicators for milk, helping to reduce milk waste.

Experimental study of the reaction of O− ions with CO2 molecules with different ternary gases at temperatures relevant to the martian ionosphere

The reaction of oxygen anions with carbon dioxide molecules is considered to be the main channel of CO3− ion formation in the Martian ionosphere. Comprehensive theoretical ion-chemical models of the Martian ionosphere require experimental data on the reactivity of negative ions with neutral gases under relevant ambient temperature and pressure conditions. The temperature dependence of the rate of the ternary reaction of O− with CO2 has been measured at temperatures relevant to the ionosphere of Mars using a VT-SIFT instrument using both helium and nitrogen as the carrier (ternary) gases. The ternary rate coefficient of the reaction was measured equal to (1.24 ± 0.06) × 10−28 (300/T)2.86±0.28 and (2.29 ± 0.05) × 10−28 (300/T)2.06±0.13 cm6s−1 for He and N2 carrier gas, respectively, in the temperature range of 230–340 K. The k3 is over two times higher in nitrogen than in helium and has a less strong inverse temperature dependence.

Diffusive Convection under Rapidly Varying Conditions

AbstractIn most observations of diffusive convection in the ocean and in lakes, the characteristic diffusive staircases evolve over long time scales under quasi-stationary background conditions. In the Baltic Sea, however, diffusive staircases develop inside the flanks of intermittent intrusions that induce strong inverse temperature gradients over a vertical range of a few meters, varying on time scales of hours to days. Here, results are discussed from an extensive field campaign conducted in summer 2016 in the southern Baltic Sea, including temperature microstructure data from ocean gliders and an autonomous profiling platform. We find conditions favorable for diffusive instability in the vicinity of warm and cold intrusions with density ratios as small as Rρ = 1.3. The staircases evolving under these conditions are characterized by a small number of steps (typically 1–4) with order 0.1–1-m thickness, temperature differences exceeding 1 K across individual diffusive interfaces, and exceptionally large diffusive heat fluxes of order 10 W m−2. The standard heat flux parameterization of Kelley agrees within a factor of 2 with the directly observed interfacial heat fluxes, except for large fluxes at low Rρ, which are strongly overestimated. The glider surveys reveal a surprisingly small lateral coherency of order 100 m of the staircase patterns, and a spreading of the diffusively unstable intrusions across isopycnals.

Eastern Gotland Basin case study of thermal variability in the wake of deep water intrusions

The warm and saline deep inflow into the Eastern Gotland Basin (EGB), which lasted from the end of November 1997 until the beginning of May 1998, was the first of a series of warm deep water inflows. Temporal fluctuations of the deep circulation were monitored at 170 m depth by two current meter moorings deployed at the north-eastern and south-western rim. The three-dimensional structure of stratification parameters was inferred from the comparison of two high-resolution hydrographic surveys carried out before and during the end of the 1997/1998 inflow event. The results indicate that near-bottom isopycnals were lifted more than 50 m during the inflow up to a depth of 170–180 m. Since the basin is enclosed at 170 m depth this implies a complete deep water renewal. Detected warm-water intrusions are shown to enhance the temperature variability on isopycnal surfaces at intermediate depth, creating strong inverse temperature gradients below the halocline in an environment with stable stratification due to salinity. Corresponding Turner angles suggest that diffusive convection may significantly contribute to diapycnal mixing in this region. In contrast, for the deepest near-bottom layers only marginally affected by intrusions, basin-scale budgets of heat and salinity suggest comparable diffusivities ( κ s = 1.3–2.1 × 10 − 5 m 2/s for salt and κ s = 1.6–2.8 × 10 − 5 m 2/s for potential temperature), implying that double-diffusion does not play a major role in mixing there. For the intermediate layer between 90 and 170 m, where the budget method could not be adopted, we applied an idealized model for the decay of temperature variance associated with the intrusions. The results indicated that the intrusions decay within a few weeks, corresponding to vertical diffusivities of a few times 10 − 5 m 2/s.

Temperature-Dependent Kinetic Isotope Effects in the Gas-Phase Reaction: OH + HBr

The temperature dependence of the hydrogen transfer rate coefficients for the reactions: OH + HBr (Reaction 1), OD + HBr (Reaction 2), OH + DBr (Reaction 3), and OD + DBr (Reaction 4) have been investigated at temperatures between 120 and 224 K using a pulsed uniform supersonic flow monitoring hydroxyl reactive loss. The lack of observed isotopic scrambling indicates the reaction occurs by H/D atom transfer from HBr/DBr at all temperatures. The rate coefficients demonstrate little temperature dependence above 200 K, but strong inverse temperature behavior below 200 K. The current work provides unequivocal experimental evidence of temperature dependent and inverse primary and secondary kinetic isotope effects (kH/ kD < 1) at low temperatures. The observed kinetic isotope ratios, kH/kD, at 120 K are for primary substitution on HBr; k1/k3 = 1.00 (±0.17) and k2/k4 = 0.46 (±0.08), while for secondary substitution on OH; k1/k2 = 0.94 (±0.20) and k3/k4 = 0.43 (±0.05). At the lowest temperature employed (120 K), deuterated reactants react as fast or faster than their natural hydrogen isotopomer and there is no significant difference between the primary and secondary kinetic isotope effect. The results are discussed within the framework of recent theoretical models.

Temperature dependence of fast neutral–neutral reactions: a triatomic model study

Some neutral–neutral reactions are known to proceed rapidly at low temperatures as a consequence of strong inverse temperature power-law dependences of the rate constants. Previous calculations, based on capture approximations, failed to account for these experimental data. In this article, short-range effects (subsequent to capture) are investigated using a simple planar atom–diatom toy model based on pairwise atomic interactions. Reaction rate constants have been estimated in the temperature range of 25–300 K using a quasi-classical trajectory Monte Carlo approach. It is shown that a small short-range barrier in the entrance valley may significantly influence the reactivity. In particular, our crude triatomic model can reproduce a strong inverse temperature dependence of the rate constant in good agreement with experimental evidence for more complex systems. These predictions are interpreted using a 3-D representation of the effective potential surfaces, illustrating the crucial importance of vector correlations between partial angular momenta. Thus, the strong inverse power-law temperature dependence of the rate constant may be attributed to the population of higher rotational states of the reactants with increasing temperature.

Observation of a strong inverse temperature dependence for the opacity of atmospheric water vapor in the MM continuum near 280 GHz

Using atmospheric opacity measurements made at 278 GHz (9.3 cm−1) at McMurdo Station, Antarctica during the austral springs of 1986 and 1987, combined with measurements of water vapor profile and total column density from near-simultaneous balloon flights, we have determined the attenuation per mm of precipitable water vapor (pwv) at this frequency. Our data were taken at significantly lower temperatures than other measurements in the literature for which accompanying water vapor pressure and temperature data are available. The results show a strong inverse dependence with temperature: measured opacity per mm of pwv is roughly a factor of two times greater at −35°C than at −10°C and three times greater than measurements at the same wavelength at +25°C reported by Zammit and Ade. We briefly review various theories proposed to explain excess absorption in continuum regions. Our lowtemperature measurements demonstrate a significantly greater inverse temperature dependence than embodied in several formulations, theoretical or empirical, proposed to represent mm-wave attenuation as a function of temperature and water vapor. The present results are qualitatively similar to observations of strong inverse temperature dependence in the near IR, but if attributed to water vapor dimer formation, imply a greater binding energy for the dimer than generally proposed by others. There is some independent evidence for a local anomaly in temperature dependence as a function of frequency near 280 GHz. It remains to be established whether our own results are strongly frequency dependent or apply generally to the mm-wave continuum.

Vibrational relaxation of O3 by H2O and D2O

The vibrational relaxation of laser excited O3(001) by H2O and D2O has been studied over the temperature range 295–473 °K. The CO2 laser-induced chemiluminescent reaction of NO+O3(001) was utilized to monitor the decay rate of vibrationally excited ozone. The relaxation probability for both water isotopes has a strong inverse temperature dependence, with D2O being four times more efficient than H2O. The results are discussed in terms of a metastable complex model for energy transfer.

Vibrational energy transfer in HF–HCN, DF–HCN, and H2–HCN mixtures

Measurements of probabilities for vibrational energy transfer are presented for the temperature range 240–450 °K for HF–HCN and DF–HCN gas mixtures. Energy transfer probabilities in these mixtures exhibit a strong inverse temperature dependence over this temperature range. Rate measurements are also given for vibrational energy transfer in H2–HCN mixtures at 298 °K. The present results suggest the feasibility of cw chemical laser operation in HF–H2–HCN mixtures on the 3.85 μ HCN(001) →HCN(010) band.

Proton spin-lattice relaxation in some paramagnetically adulterated hydrocarbon gases

An experimental study of proton spin-lattice relaxation has been made in the gas mixtures C 2H 4−O 2, C 2H 6−O 2, CH 2CF 2-0 2, C 2H 4-NO, and C 2H 6-NO. Nitric oxide is found to be very much less effective than oxygen in paramagnetic relaxation of ethane and ethylene mixtures. The proton spin-lattice relaxation rate in oxygen adulterated ethylene exceeds that in oxygen adulterated methane, or ethane, and exhibits a strong inverse temperature dependence. Nitric oxide, on the other hand, is very much less effective in ethylene than in methane. Proton and fluorine spin-lattice relaxation time measurements in CH2CF2-02 mixtures indicate that the formation of a short-lived charge transfer complex in the C 2H 4−O 2 interaction is very unlikely. The striking contrast in the paramagnetic behavior of oxygen and nitric oxide in these hydrocarbon gases may be understood when the paramagnetic moment is considered “in the short time limit” of an intermolecular interaction and due account is taken of the relative strengths of the anisotropic part of the intermolecular potential in the different gas mixtures. We show that on this basis the enhanced paramagnetic relaxation rate in C 2H 4-O 2 gas mixtures and its strong temperature dependence, as well as the greatly reduced relaxation in C 2H 4-NO mixtures, are compatible with a reduced distance of closest approach in C 2H 4-0 2 and C 2H 4-NO interactions.

Temperature Dependence of the Three-Body Recombination Coefficient in a Highly Ionized Potassium Plasma

Measurements of the volume recombination coefficient of a highly ionized potassium plasma demonstrate the strong inverse temperature dependence predicted theoretically, and provide further confirmation of the three-body nature of the recombination process.

LAG PERIOD CHARACTERIZING THE ENTRY OF TRANSFORMING DEOXYRIBONUCLEIC ACID INTO BACILLUS SUBTILIS.

Levine, James S. (Yale University, New Haven, Conn.), and Norman Strauss. Lag period characterizing the entry of transforming deoxyribonucleic acid into Bacillus subtilis. J. Bacteriol. 89:281-287. 1965.-The kinetics of appearance of transformants as a function of time of exposure to deoxyribonucleic acid (DNA) has been studied in Bacillus subtilis. A short lag period of approximately 1 min at 37 C is evident when the transformation is terminated with deoxyribonuclease. The length of this lag is independent of the genetic trait transferred. Moreover, the lag is unaffected by transforming DNA concentration, by the presence of homologous unmarked DNA, and by shearing and cross-linking of the transforming DNA. The lag shows a strong inverse temperature dependence. The energy of activation is 13.9 kcal. The lag is abolished when the transformation is terminated by washing instead of by addition of deoxyribonuclease. These results are taken to indicate an immediate adsorption of DNA to cells, followed by a deoxyribonuclease-sensitive period of 1 min, during which time the genetic trait is entering the cell. These results make feasible an investigation of the configuration assumed by the DNA molecule during entry into the cell.