Impact of UV-B, Heat and Chemicals on Ethylene-Production of Lichens

To assess the impact of UV-B radiation combined with NaHSO₃ in solution under laboratory conditions, we compared the amounts of stress-ethylene produced by two lichen species of the same genus. Ramalina lacera, an epiphytic Mediterranean lichen, was found to be rather sensitive to UV-B combined with NaHSO₃, relative to the epilithic desert lichen R. maciformis. The impact of high temperatures with FeCl₂ in solution, measured by amounts of stress ethylene accentuated the adaptability of R. maciformis to desert conditions, whereas R. lacera appeared to be rather sensitive to extreme temperatures especially in the case of chemical contamination. The adaptability of R. maciformis to UV-B appears to be related to the photoprotective capabilities of lichen substances.     

UV-B辐射增强对不同品种花生结荚期生理特性日变化的影响

以3个花生品种（开农49号、64号和69号）为材料,通过大田模拟试验,研究UV-B辐射增强对花生结荚期叶片的净光合速率（P_n）、气孔导度（G_s）、胞间CO₂浓度（C_i）、蒸腾速率（T_r）和水分利用效率（E_wu）日变化的影响,为筛选高产、抗旱、抗UV-B辐射花生品种提供依据.UV-B辐射设2个水平即自然光（CK,1.5 kJ·m^-2）和UV-B增强20%（T,1.8 kJ·m^-2）.结果表明,UV-B辐射增强明显抑制花生的光合作用和蒸腾作用,与对照相比,UV-B增强条件下,开农49号、64号和69号P_n日均值分别降低19.4%、27.8%、24.7%;G_s日均值降低26.7%、42.9%、28.6%;C_i日均值降低27.2%、20.4%、23.1%;T_r日均值降低17.8%、23.3%、25.1%;E_wu日均值降低16.6%、23.2%、23.9%.UV-B辐射增强对3个品种生长都具有抑制效应,但品种间存在一定的敏感性差异,其中开农49号最不敏感,因此,开农49号在抗UV-B辐射方面比其他2个品种具有更大的优势.     

Influence of low ozone episodes on erythemal UV-B radiation in Austria

This study investigates the influence of low ozone episodes on UV-B radiation in Austria during the period 1999 to 2015. To this aim observations of total column ozone (TCO) in the Greater Alpine Region (Arosa, Switzerland; Hohenpeissenberg, Germany; Hradec Kralove, Czech Republic; Sonnblick, Austria), and erythemal UV-B radiation, available from 12 sites of the Austrian UV-B monitoring network, are analyzed. As previous definitions for low ozone episodes are not particularly suited to investigate effects on UV radiation, a novel threshold approach—considering anomalies—is developed to provide a joint framework for the analysis of extremes. TCO and UV extremes are negatively correlated, although modulating effects of sunshine duration impact the robustness of the statistical relationship. Therefore, information on relative sunshine duration (SD_rel), available at (or nearby) UV-B monitoring sites, is included as explanatory variable in the analysis. The joint analysis of anomalies of both UV index (UVI) and total ozone (∆UVI, ∆TCO) and SD_rel across sites shows that more than 65% of observations with strongly negative ozone anomalies (∆TCO < −1) led to positive UVI anomalies. Considering only days with strongly positive UVI anomaly (∆UVI > 1), we find (across all sites) that about 90% correspond to negative ∆TCO. The remaining 10% of days occurred during fair weather conditions (SD_rel ≥ 80%) explaining the appearance of ∆UVI > 1 despite positive TCO anomalies. Further, we introduce an anomaly amplification factor (AAF), which quantifies the expected change of the ∆UVI for a given change in ∆TCO.

     

Influence of UV-B Radiation and Temperature on Photodegradation of PAHs: Preliminary Results

The joint impact of UV-B radiation and temperature on photodegradation of polycyclic aromatic hydrocarbons (PAHs) sorbed to an organic solvent was assessed in this study. This approach was experimentally performed in a laboratory investigation by means of comparison of two different environments: Atlantic (Lancaster, UK) and Mediterranean (Tarragona, Catalonia, Spain) climatic conditions. The concentration of 10 PAHs contained in a tetradecane solution was compared under two different temperatures (10 and 20°C) and UV-B doses (6.5 and 22.5 kJ m⁻² day⁻¹). No photodegradation was observed for the heaviest hydrocarbons (benzo(a)anthracene, chrysene, benzo(a)pyrene, dibenzo(g,h,i)perylene and coronene). In general terms, the half-life of PAHs was highly dependent on their molecular weight. Significant faster photodegradation rates were detected specially for light PAHs. It indicates that a synergistic effect occurred when both temperature and UV-B dose increased. This synergism might have a great implication on the long-range transport of environmental organic pollutants taking into account that low-latitude areas are the hottest and most irradiated of the planet.     

Lichens as Biomonitors of Depleted Uranium in Kosovo

This paper reports the results of a study using lichens as biomonitors to investigate the environmental distribution of depleted uranium (DU) at selected Kosovo sites as a consequence of the use of DU ordnance during the conflict of 1999. The results suggested that the use of DU ammunitions did not cause a diffuse environmental contamination in such a way to have caused a detectable U enrichment in lichens. Also isotopic ²³⁵U/²³⁸U measurements did not indicate the presence of DU particles in lichens, except for some samples at a heavily shelled site, which resulted contaminated by DU.     

Lichens as bioindicators of atmospheric heavy metal deposition in Valencia, Spain

The lichens due to their symbiotic nature have unique characteristics that confer them a key role as bioindicators of the environmental contamination. Many investigations have been done using epiphytic lichens as bioindicators, but only a few of these studies have used epilithic-crustose lichens. Three different epilithic-crustose lichens species: Candelariella sp., Lecanora sp. and Caloplaca sp. were studied as bioindicators of V, Cr, Mn, Co, Ni, Cu, Zn, As, Rb, Sr, Mo, Cd, Sb, Ba, Pb, Bi and U trace elements. Inductively Coupled Plasma Mass Spectrometry routine procedure is used to determining these element concentrations. Two sites were selected for lichens sampling according to environmental contamination. The lichens were collected on the facade of the Santos Juanes church in an urban area of Valencia; and on the rural area of Albarracin. The main aim of this work is showing the efficacy of the epilithic-crustose lichens as bioindicators of the air pollution. This study shows that the city of Valencia, compared with the rural area has high levels of Cu and Pb as detected using lichens as bioindicators. Therefore on the basis of these results, it can be hypothesized that Candelariella sp., Lecanora sp. and Caloplaca sp. are good accumulators of air borne heavy metals.     

Metabolised Tritium and Radiocarbon in Lichens and Their Use as Biomonitors

Lichens are now well known for their potential as bio-indicators of environmental pollution, but less is known about their suitability as quantitative biomonitors for atmospheric emissions of tritium (mainly as tritiated water, HTO) and radiocarbon (as ¹⁴CO₂) from nuclear facilities, although both radionuclides could result in non-trivial individual or collective radiation doses due to their high environmental mobility and their long half-lives. ³H and ¹⁴C are fixed in lichens mainly by the photosynthesis of the algal partner and then stored in the organic molecules of both alga and fungus. They have the advantage of allowing the monitoring of atmospheric water vapour without interference of soil water or soil organic substances as long as soil-inhabiting species are avoided. Lichens were collected in the surroundings of (military and civil) nuclear facilities, in areas away from any direct source of contamination and some were transplanted from a contaminated area to a non-contaminated one. The influence of the nuclear facilities can be clearly traced, sometimes in a spectacular way and the first results of analyses after transplants give a base for estimating the effective half-life of ³H in lichens.     

Diversity of Epiphytic Lichens and Hg Contents of Xanthoria parietina Thalli as Monitors of Geothermal Air Pollution in the Mt. Amiata Area (Central Italy)

The diversity of epiphytic lichens and mercury concentrations in lichen samples were measured to monitor the release of airborne pollutants from the industrial exploitation of geothermal resources in the Mt. Amiata area (Italy). The lichen biodiversity showed a general condition of moderate environmental alteration around the geothermal power plants, contrasting with the low environmental alteration of the remaining sites investigated. According to the accumulated Hg in lichen thalli, it was possible to estimate mean Hg and H₂S concentrations in the air, which resulted in very good agreement with values measured instrumentally. Based on these data and the correlation between lichen diversity values and Hg concentrations in lichens, it was possible to calculate the threshold of 8 μg/m³ H₂S as responsible for the worsening from low to moderate environmental alteration according to the biodiversity of epiphytic lichens, and to infer that around geothermal power plants, although not toxic to humans, H₂S concentrations are such to alter the nasal quality of the air. Based on the growth rate of X. parietina, it was possible to convert Hg concentrations into estimates of average Hg deposition rates, which showed fluxes of the order of 65–100 mg/ha/y, indicating a dispersions factor of about 10⁴ for the Hg emitted from the geothermal power plants.     

Sorption Characteristics of Inorganic, Methyl and Elemental Mercury on Lichens and Mosses: Implication in Biogeochemical Cycling of Mercury

The sorption studies of Hg²⁺, CH₃Hg⁺ and elemental mercury (Hg⁰) were carried out on lichen (Parmelia sulcata) and moss (Funaria hygrometrica) samples under laboratory conditions. Desorption studies with HCl indicate that inorganic mercury (Hg⁺²) and methyl mercury could be completely desorbed with 1 M HCl and 0.5 M HCl, respectively. Samples loaded with elemental mercury, however, needed 4–5 M HCl concentration for complete desorption of the adsorbed elemental mercury. When similar desorption studies were carried out with field samples collected around a thermometer factory with elevated levels of mercury (8 mg/kg), it was found that only about 10–15% of total mercury was desorbed with 1M HCl, while 4–5 M acid was required for complete desorption. We have tried to correlate this information to understand the transformations of mercury species that may occur either in the atmosphere or on the biomonitors. The results indicated that the elemental mercury, the principal form of mercury contamination around the thermometer factory, is converted into a strongly held form by some chemical binding agents on the surface of lichen/moss, or elemental mercury could diffuse into the cells of the lichen/moss, which then needs the stronger acid to release it. Sorption capacity studies suggest that the lichens and mosses can also be used as sorbent material for the decontamination of inorganic and methyl mercury from aqueous solutions.     

The Influence of Hilly Terrain on Canopy-Atmosphere Carbon Dioxide Exchange

Topography influences many aspects of forest-atmosphere carbon exchange; yet only a small number of studies have considered the role of topography on the structure of turbulence within and above vegetation and its effect on canopy photosynthesis and the measurement of net ecosystem exchange of CO₂ (N_ee) using flux towers. Here, we focus on the interplay between radiative transfer, flow dynamics for neutral stratification, and ecophysiological controls on CO₂ sources and sinks within a canopy on a gentle cosine hill. We examine how topography alters the forest-atmosphere CO₂ exchange rate when compared to uniform flat terrain using a newly developed first-order closure model that explicitly accounts for the flow dynamics, radiative transfer, and nonlinear eco physiological processes within a plant canopy. We show that variation in radiation and airflow due to topography causes only a minor departure in horizontally averaged and vertically integrated photosynthesis from their flat terrain values. However, topography perturbs the airflow and concentration fields in and above plant canopies, leading to significant horizontal and vertical advection of CO₂. Advection terms in the conservation equation may be neglected in flow over homogeneous, flat terrain, and then N_ee = F_c, the vertical turbulent flux of CO₂. Model results suggest that vertical and horizontal advection terms are generally of opposite sign and of the same order as the biological sources and sinks. We show that, close to the hilltop, F_c departs by a factor of three compared to its flat terrain counterpart and that the horizontally averaged F_c-at canopy top differs by more than 20% compared to the flat-terrain case.     

A Model to Estimate Global Radiation in Complex Terrain

Global radiation is an important parameter necessary for most ecological models. However, in situ data barely meets the needs of modelling mountainous ecosystems since most field stations are located in flat areas. Consequently, it is usually necessary to extrapolate radiation measurements obtained from an adjacent flat area to the complex terrain of concern. The distribution of radiation in complex terrain depends upon two factors: the local atmospheric conditions, which determine the radiation potentially available to a supposed flat surface in a given location, and the topographic effects on this possible radiation. The latter have been included in detail in most radiation models for complex terrain, but the former are often only simply treated as constant or estimated by over-simplified empirical algorithms. In this paper we propose a novel model that uses a parametric atmospheric model to calculate the potential radiation for a supposed flat surface in a given location, and then account for topographic effects. Direct radiation, diffuse radiation and reflected radiation are calculated separately in the model due to the distinctive characteristics of and the effects by topography. Based on the parametric model, this paper has investigated the relationship between radiation transmittance, clearness indices and altitude under a series of water vapour content and turbidity conditions. This combines three ratios, R _b, R _d, and R _r, defined as the direct radiation, diffuse radiation and reflected radiation received by the arbitrary surface, respectively, to their counterparts in the horizontal surface, to estimate the global radiation for any given location. The model has been validated with data from measurements in National Park Berchtesgaden, Germany, where six measurement sites with various altitudes and topographic characteristics have been deployed. The r ² of modelled and measured hourly global radiation are greater than 0.90 in all six sites, with RMSE varies from 16 to 100 W m⁻². Sensitivity analysis revealed that the model was not sensitive to change in water vapour content, which suggests the possibility to use an exponential algorithm of water vapour content when there is no in situ water vapour content information in complex terrains. The NRMSE was only reduced by 0.04, on average, in five of the six sites when water vapour content information was calculated from the in situ air temperature and relative humidity measurements.     

Uranium Isotopes, Metals and Other Elements in Lichens and Tree Barks Collected in Bosnia–Herzegovina

The United Nations Environment Programme (UNEP) performed field surveys at 15 sites in Bosnia–Herzegovina where depleted uranium (DU) ammunition was used by the North Atlantic Treaty Organization (NATO) during the Balkans conflict (1994–1995). During the field missions, the Italian Environmental Protection Agency (APAT) evaluated airborne contamination due to DU dusts or aerosol particles, generated at the time of the conflict by the impact of DU ammunition on hard targets, using lichens and tree barks as biomonitors. Each sample was analyzed by alpha-spectrometry for DU determination. The ²³⁴U/²³⁸U activity concentration ratios were used to distinguish natural from anthropogenic uranium. This paper reports the data obtained by the UNEP investigation, including (non-radioactive) metal and other element concentrations in lichen and tree bark samples measured by instrumental neutron activation analysis (INAA). The results indicated: (i) lichens and tree barks are sensitive bio-accumulators of past airborne contamination by depleted uranium dusts; (ii) 8 years after the conflict, environmental DU contamination is still present at some of the target sites; and (iii) the highest concentrations of most non-radioactive elements were found at sites used for ammunition destruction.     

Radiation balance over low-lying and mountainous areas in south-west Germany

Summary  Surface radiative fluxes play a major role in the energy exchange process between the atmosphere and earth surface and are thus very crucial to climatic processes within the atmospheric boundary layer. Based on four years REKLIP (REgio-KLIma-Project) data set of measured radiative fluxes and additional supporting meteorological variables, the surface radiation regime for selected lowland site (Bremgarten 212 m a.s.l.) and mountain sites (Geiersnest at 870 m a.s.l.; Feldberg 1489 m a.s.l.) in the southern Upper Rhine valley region (south-west Germany) has been reported. Time series of radiative fluxes and surface albedo showed significant inter-site differences. Possible reasons for the observed differences have been made. Downward atmospheric radiation A _l at the study sites was parameterised in terms of air temperature, vapour pressure and cloud amount, all of which strongly govern the variation of A _l . Effective terrestrial radiation amounted to about 50% of absorbed shortwave radiation at the study sites annually. During clear sky conditions, global solar irradiance G _s constituted about 76.0% of the incident extraterrestrial solar irradiance at Feldberg mountain site but only 68.5% of that at Bremgarten lowland site. Annual cumulative of net radiative flux R _n amounted to 1722 MJm⁻² yr⁻¹ at the lowland site, while that at Geiersnest and Feldberg mountain sites constituted 84% and 73% respectively of the corresponding magnitude for the lowland site. In the same vein, annual mean of radiation efficiency (defined here as R _n /G _s ) amounted to 0.32 in Feldberg, 0.37 in Geiersnest and 0.41 in Bremgarten. Consequently the annual available energy, of which net radiative flux is representative, was smaller at the mountain ous sites relative to the lowland site during the study period. Inter-annual variability of net radiative flux, its constituent variables and derivatives at the study sites were generally below 10%, with longwave fluxes showing the lowest fluctuation. This renders the measured data quite suitable for modelling purposes. In winter, mean daily sums of R _n showed a slow rise with cloud amount N at the lowland site but a sharp rise with N at Feldberg mountain site. In summer however, mean daily sums of R _n declined significantly with N as well as Linke turbidity factor at the study sites. Received June 24, 1999 Revised November 2, 2000     

Internal tide generation at a continental shelf/slope junction: A comparison between theory and a laboratory experiment

Observations of internal tide generation over continental slopes in a laboratory experiment have been carried out, with the objectives of making comparisons with linear generation theory and investigating its limitations. Both continuous and layered stratification have been considered. A measure of the amplitude of the barotropic tidal forcing (and hence of non-linearity) is given by the Froude Number F = u_sb/c_w, where u_sb is the maximum barotropic tidal velocity at the shelf break, and c_w is the long-wave speed of the lowest internal mode.For continuous stratification, good agreement was obtained for “steep” slopes (α/c > 1), where α is the slope at the continental slope and c is the slope of the internal wave rays of tidal frequency), even for quite large amplitude motions (F < 1.6), and the upper limit of its quantitative usefulness was not reached. For “flat” slopes (α/c < 1) reasonable agreement was also obtained, even up to quite amplitudes (F < 3.1), although some departure from linear theory was apparent.For two-layer flows the applicability of linear theory was much more restricted. For F 0.5 there was only qualitative agreement and for larger F (>1) significant differences were observed. The latter were due to the substantial advection and associated hydraulic jumps which occured seaward of the shelf-break during the ebb-phase of the barotropic tide. Shelf-break values of F > 1 are common in the ocean.     

Stratospheric ozone reduction,solar UV-B radiation and terrestrial ecosystems

Stratospheric ozone reduction is occurring and will continue to increase in magnitude into the next century. Yet, the consequences for terrestrial ecosystems of the increased solar UV-B (280–320 nm) radiation resulting from total column ozone reduction are not understood. Based on studies of higher plant response to UV-B, several possible consequences for ecosystems include decreased primary production, altered plant species composition, and altered secondary chemistry with implications for herbivory, litter decomposition and biogeochemical cycles. However, like the assessment of increased atmospheric CO₂, extrapolation from studies with isolated plants to ecosystem function is very tenuous at best. Very few UV-B studies have dealt with multispecies systems. Most of the UV-B research in the past two decades (since the first suggestions of ozone reduction) has been conducted as short-term experiments in growth chambers and greenhouses where the unnatural spectral balance of radiation can lead to unrealistic conclusions. Technical difficulties in suitable measurement and manipulation of UV-B radiation also complicate the conduct of reliable experiments. This essay surveys and categorizes some 300 papers from the past 20 years on this subject, draws general conclusions from the research and offers some recommendations with respect to ecosystem consequences.     

Lichen as quantitative biomonitors of atmospheric heavy metals deposition in Central India

Three different growth forms of lichens belonging to six species; Phaeophyscia hispidula, Parmotrema praesorediosum (foliose); Caloplaca subsoluta, Diploschistes candidissmus (crustose) and Peltula euploca, Phylliscum indicum (squamulose) were studied comparatively for the biomonitoring of Al, Cd, Cr, Cu, Fe, Ni and Zn in Mandav city in central India. Based on the anthropogenic activities three sites were selected for lichen collection. To identify the sources of heavy metal pollution, their concentration was analyzed in thallus as well as in their respective substrates. The thallus of studied lichens showed higher concentration of metals such as Cd, Cr, Ni and Zn, while most of the metals were absent or present in negligible amount in substrates (Fe, Al, Cu), which proves that the accumulated metals were air borne. The foliose lichens (P. hispidula and P. praesorediosum) found highly significant in metal accumulation at each sites followed by crustose and squamulose forms. Lichen samples collected from site 2, adjacent to road side accumulated maximum quantities of Zn, Ni, Cd and Cr whereas the city centre (Site 1) had maximum concentrations of Fe, Cu and Al. The site 3 situated away from the city had lowest amount of all the metals. The analysis of variance and LSD indicated that the metal concentrations among lichen species as well as between substratum is significant at p < 0.05% and P < 0.01% level respectively.     

Potential effects of global climatic change on the phenology and yield of maize in venezuela

Simulated impacts of global and regional climate change, induced by an enhanced greenhouse effect and by Amazonian deforestation, on the phenology and yield of two grain corn cultivars in Venezuela (CENIAP PB-8 and OBREGON) are reported. Three sites were selected:Turén, Barinas andYaritagua, representing two important agricultural regions in the country. The CERES-Maize model, a mechanistic process-based model, in theDecision Support System for Agrotechnology Transfer (DSSAT) was used for the crop simulations. These simulations assume non-limiting nutrients, no pest damage and no damage from excess water; therefore, the results indicate only the difference between baseline and perturbed climatic conditions, when other conditions remain the same. Four greenhouse-induced global climate change scenarios, covering different sensitivity levels, and one deforestation-induced regional climate change scenario were used. The greenhouse scenarios assume increased air temperature, increased rainfall and decreased incoming solar radiation, as derived from atmospheric GCMs for doubled CO₂ conditions. The deforestation scenarios assume increased air temperature, increased incoming solar radiation and decreased rainfall, as predicted by coupled atmosphere-biosphere models for extensive deforestation of a portion of the Amazon basin. Two baseline climate years for each site were selected, one year with average precipitation and another with lower than average rainfall. Scenarios associated with the greenhouse effect cause a decrease in yield of both cultivars at all three sites, while the deforestation scenarios produce small changes. Sensitivity tests revealed the reasons for these responses. Increasing temperatures, especially daily maximum temperatures, reduce yield by reducing the duration of the phenological phases of both cultivars, as expected from CERES-Maize. The reduction of the duration of the kernel filling phase has the largest effect on yield. Increases of precipitation associated with greenhouse warming have no effects on yield, because these sites already have adequate precipitation; however, the crop model used here does not simulate potential negative effects of excess water, which could have important consequences in terms of soil erosion and nutrient leaching. Increases in solar radiation increased yields, according to the non-saturating light response of the photosynthesis rate of a C₄ plant like corn, compensating for reduced yields from increased temperatures in deforestation scenarios. In the greenhouse scenarios, reduced insolation (due to increased cloud cover) and increased temperatures combine to reduce yields; a combination of temperature increase with a reduction in solar radiation produces fewer and lighter kernels.A report of thePAN-EARTH Project, Venezuela Case Study.     

Arsenic Speciation in Transplanted Lichens and Tree Bark in the Framework of a Biomonitoring Scenario

Arsenic and its chemical species were determined in transplanted lichens (Parmelia caperata) and tree bark (Platanus hybrida), in order to get a better understanding of their atmospheric cycling and the suitability of these materials for biomonitoring purposes. Various strategies were used (discontinuous and cumulative exposure of transplants) to biomonitor two locations in Portugal, viz. the northern Lisbon area and Sines, both highly industrialised areas.Analytical techniques comprised instrumental nuclear activation analysis (INAA), inductively coupled plasma-mass spectrometry (ICP-MS) and high performance liquid chromatography-hydride generation atomic fluorescence spectrometry (HPLC-HGAFS) for determination of total arsenic in solid materials, total arsenic in extracts of solid materials and arsenic species in extracts of solid materials, respectively.Only a fraction (up to 50%) of the extracted arsenic species could be identified and quantified in the transplanted lichens, being mainly inorganic arsenic and some methylated arsenic species. Since in a previous study these methylated arsenic species were not found in aerosols collected in the same area, it is probable that the lichen transplants studied (Parmelia caperata) do not behave as genuine passive biomonitors but are able to actively methylate inorganic arsenic to methylated arsenic species. Furthermore, this lichen-induced methylation occurs with some delay, possibly as a reaction to the transplantation of the lichen itself, and therefore transplanted lichens are only suitable for long-term biomonitoring studies. For tree bark only total arsenic concentration data could be generated since speciation analysis failed due to too low an initial total arsenic concentrations.     

An Empirical Tropical Instability Wave-induced Wind Stress Model in the Equatorial Pacific and its Incorporation into the Ocean Model

Abstract

Satellite observations revealed that there is a close relationship between perturbations of sea surface temperature (SST) and wind stress (τ) induced by tropical instability waves (TIWs; SST_TIW and τ _TIW). Using the empirical relationship observed between TIW-induced wind stress divergence (curl) and downwind (crosswind) SST gradients, this study establishes a TIW-induced wind stress field perturbation model τ _TIW?=?F(SST). This empirical model solves τ _TIW from the TIW-induced wind stress divergence and curl, which are estimated from the downwind and crosswind SST gradients. This empirical τ _TIW?=?F(SST) model can be incorporated into the ocean model to take into account the effect of τ _TIW. By comparing two experiments with and without the τ _TIW effect, this study demonstrates that τ _TIW has a substantial effect on the equatorial Pacific heat budget and induces the long-term mean SST to exhibit a 0.2°C difference, which is consistent with previous studies.     

Statistics of Scalar Fields in the Atmospheric Boundary Layer Based on Large-eddy Simulations. Part 1: Free Convection

Convection in a quasi-steady, cloud-free, shear-free atmospheric boundary layer is investigated based on a large-eddy simulation model. The performed tests indicate that the characteristic (peak) values of statistical moments at the top of the mixed layer are proportional to the interfacial scales (from gradients of scalars in the interfacial layer). Based on this finding a parameterization is proposed for profiles of scalar variances. The parameterization employs two, semi-empirical similarity functions F_m(z/z_i) andF_i(z/z_i), multiplied by a combination of the mixed-layer scales and the interfacial scales.