scholarly journals Cirrus, Transport, and Mixing in the Tropical Upper Troposphere

2014 ◽  
Vol 71 (4) ◽  
pp. 1339-1352 ◽  
Author(s):  
Tra Dinh ◽  
Stephan Fueglistaler
Keyword(s):  
Radiative Heating ◽  
Transport Time ◽  
Adequate Model ◽  
Upper Troposphere ◽  
Advection Diffusion Equation ◽  
Free Region ◽  
The Mean ◽  
The Individual ◽  
The Impact ◽  
Tropical Upper Troposphere

Abstract The impact of cloud radiative heating on transport time scales from the tropical upper troposphere to the stratosphere is studied in two-dimensional numerical simulations. Clouds are idealized as sources of radiative heating and are stochastically distributed in space and time. A spatial probability function constrains clouds to occur in only part of the domain to depict heterogeneously distributed clouds in the atmosphere. The transport time from the lower to upper boundaries (age of air) is evaluated with trajectories. The spectra of age of air obtained in the simulations are bimodal, with the first mode composed of trajectories that remain in the cloudy part of the domain during their passages from the lower to upper boundaries, and the second mode composed of the remaining trajectories that visit the cloud-free regions. For the first group of trajectories only, the mean age scales inversely with the time-mean radiative heating in cloudy air, and the one-dimensional advection–diffusion equation provides an adequate model for transport. However, the exchange between the cloudy and cloud-free regions renders the mean age over all trajectories (including those that visit the cloud-free region) much longer than the time expected if all air parcels remain in cloudy air. In addition, the overall mean age is not inversely proportional to the time-mean heating rate in cloudy air. Sensitivity calculations further show that the sizes, durations, and amplitudes of the individual clouds are also important to the transport time. The results show that the frequently used decomposition of radiative heating into clear-sky and cloud radiative heating may give incorrect interpretations regarding the time scale of transport into the stratosphere.

scholarly journals The Role of Tropical, Midlatitude, and Polar Cloud-Radiative Changes for the Midlatitude Circulation Response to Global Warming

2020 ◽  
Vol 33 (18) ◽  
pp. 7927-7943 ◽  
Author(s):  
Nicole Albern ◽  
Aiko Voigt ◽  
David W. J. Thompson ◽  
Joaquim G. Pinto
Keyword(s):  
Global Warming ◽  
Storm Track ◽  
Radiative Heating ◽  
Sea Surface ◽  
Relative Importance ◽  
Upper Troposphere ◽  
The Mean ◽  
The Impact ◽  
Circulation Changes

AbstractPrevious studies showed that global cloud-radiative changes contribute half or more to the midlatitude atmospheric circulation response to global warming. Here, we investigate the relative importance of tropical, midlatitude, and polar cloud-radiative changes for the annual-mean, wintertime, and summertime circulation response across regions in AMIP-like simulations. To this end, we study global warming simulations from the ICON model run with the cloud-locking method and prescribed sea surface temperatures, which isolate the impact of changes in atmospheric cloud-radiative heating. Tropical cloud changes dominate the global cloud impact on the 850 hPa zonal wind, jet strength, and storm track responses across most seasons and regions. For the jet shift, a more diverse picture is found. In the annual mean and DJF, tropical and midlatitude cloud changes contribute substantially to the poleward jet shift in all regions. The poleward jet shift is further supported by polar cloud changes across the Northern Hemisphere but not in the Southern Hemisphere. In JJA, the impact of regional cloud changes on the jet position is small, consistent with an overall small jet shift during this season. The jet shift can be largely understood via the anomalous atmospheric cloud-radiative heating in the tropical and midlatitude upper troposphere. The circulation changes are broadly consistent with the influence of cloud-radiative changes on upper-tropospheric baroclinicity and thus the mean potential energy available for conversion into eddy kinetic energy. Our results help to explain the jet response to global warming and highlight the importance of tropical and midlatitude cloud-radiative changes for this response.

scholarly journals Association between stress and bilateral symmetrical alopecia in free-ranging Formosan macaques in Mt. Longevity, Taiwan

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chen-Chih Chen ◽  
Ai-Mei Chang ◽  
Ming-Shan Tsai ◽  
Yen-Hua Huang ◽  
Kurtis Jai-Chyi Pei ◽  
...  
Keyword(s):  
Total Population ◽  
Causative Factor ◽  
Population Status ◽  
Adrenocortical Activity ◽  
High Incidence ◽  
Normal Hair ◽  
The Mean ◽  
The Individual ◽  
Free Ranging ◽  
The Impact

AbstractSince 2013, a high incidence of bilateral symmetrical alopecia has been observed in free-ranging Formosan macaques (Macaca cyclopis) in Mt. Longevity, Taiwan. We hypothesized that stress induces alopecia in this population. To verify our hypothesis, we evaluated the histopathological characteristics of skin biopsy and used a validated enzyme immunoassay (EIA) for fecal glucocorticoid metabolite (FGM) analysis, which act as an indicator of stress experienced by the individual. Follicular densities were lower (2.1–3.0 mm2) in individuals with symmetrical alopecia than in those with normal hair conditions (4.7 mm2). Furthermore, anagen to catagen/telogen ratios were lower in individuals with alopecia (0–1.4) than in those with normal hair (4.0). The histopathological characteristics of alopecia were similar to those of telogen effluvium, which indicates that stress is one of the possible etiologies. On the basis of the analytical and biological validation of EIAs for FGM analysis, 11β-hydroxyetiocholanolone was considered suitable for monitoring adrenocortical activity in both sexes of Formosan macaques. The mean concentrations (standard error; sample size) of 11β-hydroxyetiocholanolone were 2.02 (0.17; n = 10) and 1.41 (0.10; n = 31) μg/g for individuals with and without alopecia, respectively. Furthermore, the results of logistic regression analysis show that 11β-hydroxyetiocholanolone (p = 0.012) concentration was positively associated with alopecia. Thus, stress was the most likely to trigger symmetrical alopecia in Formosan macaques in Mt. Longevity. Although stress can decrease the fitness of an individual, considering the population status of Formosan macaques in Taiwan is stable and alopecia was only observed in our study area, which is isolated from other populations, the impact on the total population of Formosan macaque in Taiwan is limited. Nonetheless, stress-induced immunosuppression and alopecia might affect the local abundance and increase zoonosis risk due to frequent human–macaque contact in Mt. Longevity. Future studies are suggested to focus on the causative factor of stress and the effects of stress and alopecia on the health and welfare in the Formosan macaques.

scholarly journals Impact of a training program on the performance of graduating Canadian residents on a national urology exam: Results of the last 20 years

2018 ◽  
Vol 13 (2) ◽  
Author(s):  
Naji J. Touma ◽  
Darren T. Beiko ◽  
Andrew E. MacNeily ◽  
Michael J. Leveridge
Keyword(s):  
Training Program ◽  
Training Programs ◽  
Certification Exams ◽  
Certification Exam ◽  
Individual Program ◽  
The Mean ◽  
And Performance ◽  
The Individual ◽  
The Impact ◽  
Oral Component

Introduction: Many factors impact the performance of graduating residents on certification exams. It is thought that most factors are related to the individual candidate’s ability, motivation, and work ethic. Less understood, however, is whether a training program has any impact on the preparation and performance of its graduates on certification exams. We present 20 years of results of a national preparatory exam that all graduating residents complete about three months before the Royal College of Physicians and Surgeons of Canada (RCPSC) qualifying urology exam. This exam, known colloquially as QUEST, aims to simulate the RCPSC exam with written and oral components. We aimed to analyze the impact of a training program on the performance of its residents. Methods: A retrospective review of exam results from 1997–2016 was conducted. During that time, 495 candidates from all 12 Canadian urology training programs undertook the exam. The performance of graduating residents from each individual program was grouped together for any given year. The different programs were anonymized, as the aim of this study is to assess the impact of a training program and not to rate the different programs. Statistical analysis using one-way ANOVA was conducted. Results: All training programs fall within one standard deviation of the mean for the written component, the oral component, and the overall score. The residents of four training programs had statistically better scores than the overall mean of the written component. The residents of three out of these four training programs also had statistically better scores than the overall mean of the oral component and the overall results of the exam. Conclusions: Most Canadian training programs prepare their residents adequately for this simulated certification exam in urology. However, there are some training programs that consistently prepare graduating residents to outperform their peers.

scholarly journals Publications Trends in Major Anesthesiology Journals: A 20-Year Analysis of Five Top-Ranked Journals in the Field

2021 ◽  
Vol 2 (5) ◽  
pp. 418-424
Author(s):  
Stefan Koppert ◽  
Michael Weibenbacher ◽  
Andreas Wieser ◽  
Christoph Zelger ◽  
Markus Hermann ◽  
...  
Keyword(s):  
Case Reports ◽  
Absolute Number ◽  
Publication Trends ◽  
Microsoft Excel ◽  
Rating Instrument ◽  
The Mean ◽  
Number Of Publications ◽  
The Individual ◽  
The Impact ◽  
Number Of Authors

Background: With the intention to quantify the importance of a medical journal, the Impact Factor (IF) was introduced. It has become a de facto fictive rating instrument of the importance of medical journals. Also, it is often used to assess the value of the individual publications within the specific journal. The aim of the present study was to analyze publication trends over 20 years in five high-ranked anesthesiology journals. Methods: The Medline (NCBI) database PubMed was used for analysis which was restricted to the following journals: 1. Anesthesiology; 2. British Journal of Anaesthesia; 3. Journal of Neurosurgical Anesthesiology; 4. Anesthesia & Analgesia; and 5. Anaesthesia. Specific publication parameters (IFs, number of pages and authors, etc.) were retrieved using the PubMed download function and imported into Microsoft Excel for further analysis. Results: The mean IF of the five journals analyzed increased significantly within the study period (1991 vs. 2010; +61.81%). However, the absolute number of case reports decreased significantly by 54.7% since 1991. The journals Br J Anaesth (12.2%), J Neurosurg Anesthesiol (51.9%), and Anesth Analg (57.2%) showed significant increases in the number of publications per year. The mean number of authors increased significantly in all the journals from 1991 to 2010 (3.0 vs. 4.3; +43.3%). Conclusions: The IF, as well as the number of articles per year and the number of authors per article, increased significantly. In contrast, the number of pages per article remained comparable during the period analyzed.

scholarly journals Species Diversity of Oak Stands and Its Significance for Drought Resistance

2018 ◽  
Author(s):  
Jan Kotlarz ◽  
Sylwia Nasiłowska ◽  
Karol Rotchimmel ◽  
Katarzyna Kubiak
Keyword(s):  
Species Diversity ◽  
Satellite Images ◽  
Aerial Images ◽  
Summer Drought ◽  
Different Types ◽  
The Mean ◽  
The Individual ◽  
Pca Algorithm ◽  
The Impact ◽  
Remote Sensing Indices

Drought periods have an adverse impact on the condition of oak stands. Research on different types of ecosystems has confirmed a correlation between plant species diversity and the adverse effects of droughts. The purpose of this study was to investigate the changes which occurred in an oak stand (Krotoszyn Plateau, Poland) under the impact of the summer drought in 2015. We used a method based on remote sensing indices from satellite images in order to detect changes in the vegetation in 2014 and 2015. A positive difference was interpreted as an improvement, whereas a negative one was treated as a deterioration of the stand condition. The Shannon-Wiener species diversity was estimated using an iterative PCA algorithm based on aerial images. We observed a relationship between the species indices of the individual forest divisions and their response to drought. The highest correlation between the index differences and the Shannon-Wiener indices was found for the GNDVI index (+0.74). In addition, correlations were observed between the mean index difference and the percentage shares in the forest divisions of species such as Pinus sylvestris (+0.67 ± 0.08) and Quercus robur (-0.65 ± 0.10). Our results lead us to infer that forest management based on highly diverse habitats is more suitable to meet the challenges in the context of global climatic changes, characterized by increasingly frequent droughts.

scholarly journals Radiative forcing and climate metrics for ozone precursor emissions: the impact of multi-model averaging

2014 ◽  
Vol 14 (19) ◽  
pp. 27195-27231
Author(s):  
C. R. MacIntosh ◽  
K. P. Shine ◽  
W. J. Collins
Keyword(s):  
Radiative Forcing ◽  
Transport Model ◽  
Task Force ◽  
Mean Field ◽  
Model Averaging ◽  
Chemical Transport Model ◽  
Ensemble Mean ◽  
The Mean ◽  
The Individual ◽  
The Impact

Abstract. Multi-model ensembles are frequently used to assess understanding of the response of ozone and methane lifetime to changes in emissions of ozone precursors such as NOx, VOC and CO. When these ozone changes are used to calculate radiative forcing (RF) (and climate metrics such as the global warming potential (GWP) and global temperature potential (GTP)) there is a methodological choice, determined partly by the available computing resources, as to whether the mean ozone (and methane lifetime) changes are input to the radiation code, or whether each model's ozone and methane changes are used as input, with the average RF computed from the individual model RFs. We use data from the Task Force on Hemispheric Transport of Air Pollution Source-Receptor global chemical transport model ensemble to assess the impact of this choice for emission changes in 4 regions (East Asia, Europe, North America and South Asia). We conclude that using the multi-model mean ozone and methane responses is accurate for calculating the mean RF, with differences up to 0.6% for CO, 0.7% for VOC and 2% for NOx. Differences of up to 60% for NOx 7% for VOC and 3% for CO are introduced into the 20 year GWP as a result of the exponential decay terms, with similar values for the 20 years GTP. However, estimates of the SD calculated from the ensemble-mean input fields (where the SD at each point on the model grid is added to or subtracted from the mean field) are almost always substantially larger in RF, GWP and GTP metrics than the true SD, and can be larger than the model range for short-lived ozone RF, and for the 20 and 100 year GWP and 100 year GTP. We find that the effect is generally most marked for the case of NOx emissions, where the net effect is a smaller residual of terms of opposing signs. For example, the SD for the 20 year GWP is two to three times larger using the ensemble-mean fields than using the individual models to calculate the RF. Hence, while the average of multi-model fields are appropriate for calculating mean RF, GWP and GTP, they are not a reliable method for calculating the uncertainty in these fields, and in general overestimate the uncertainty.

scholarly journals The impact of lightning on tropospheric ozone chemistry using a new global parametrisation

2016 ◽  
Author(s):  
D. L. Finney ◽  
R. M. Doherty ◽  
O. Wild ◽  
N. L. Abraham
Keyword(s):  
Frequency Distribution ◽  
Tropospheric Ozone ◽  
Climate Model ◽  
Upper Troposphere ◽  
Temporal Correlations ◽  
The Uk ◽  
Cloud Ice ◽  
The Impact ◽  
No Emissions ◽  
Tropical Upper Troposphere

Abstract. A lightning parametrisation based on upward cloud ice flux is implemented in a chemistry-climate model (CCM) for the first time. The UK Chemistry and Aerosols model is used to study the impact of these lightning nitric oxide (NO) emissions on ozone. Comparisons are then made between the new ice flux parametrisation and the commonly-used, cloud-top height parametrisation. The ice flux approach improves the simulation of lightning and the temporal correlations with ozone sonde measurements in the middle and upper troposphere. Peak values of ozone in these regions are attributed to high lightning NO emissions. The ice flux approach reduces the overestimation of tropical lightning apparent in this CCM when using the cloud-top approach. This results in less emission in the tropical upper troposphere and more in the extratropics when using the ice flux scheme. In the tropical upper troposphere the reduction in ozone concentration is around 5–10 %. Surprisingly, there is only a small reduction in tropospheric ozone burden when using the ice flux approach. The greatest absolute change in ozone burden is found in the lower stratosphere suggesting that much of the ozone produced in the upper troposphere is transported to higher altitudes. Major differences in the frequency distribution of flash rates for the two approaches are found. The cloud-top height scheme has lower maximum flash rates and more mid-range flash rates than the ice flux scheme. The initial Ox (odd oxygen species) production associated with the frequency distribution of continental lightning is analysed to show that higher flash rates are less efficient at producing Ox – low flash rates produce around 10 times more Ox per flash than high-end flash rates. We find that the newly implemented lightning scheme performs favourably compared to the cloud-top scheme with respect to simulation of lightning and tropospheric ozone. This alternative lightning scheme shows spatial and temporal differences in ozone chemistry which may have implications for comparison on models and observations and for simulation of future changes in tropospheric ozone.

Multimodel Analysis of the Water Vapor Feedback in the Tropical Upper Troposphere

2006 ◽  
Vol 19 (20) ◽  
pp. 5455-5464 ◽  
Author(s):  
Ken Minschwaner ◽  
Andrew E. Dessler ◽  
Parnchai Sawaengphokhai
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Sea Surface ◽  
Specific Humidity ◽  
Upper Troposphere ◽  
The Mean ◽  
Tropical Upper Troposphere

Abstract Relationships between the mean humidity in the tropical upper troposphere and tropical sea surface temperatures in 17 coupled ocean–atmosphere global climate models were investigated. This analysis builds on a prior study of humidity and surface temperature measurements that suggested an overall positive climate feedback by water vapor in the tropical upper troposphere whereby the mean specific humidity increases with warmer sea surface temperature (SST). The model results for present-day simulations show a large range in mean humidity, mean air temperature, and mean SST, but they consistently show increases in upper-tropospheric specific humidity with warmer SST. The model average increase in water vapor at 250 mb with convective mean SST is 44 ppmv K−1, with a standard deviation of 14 ppmv K−1. Furthermore, the implied feedback in the models is not as strong as would be the case if relative humidity remained constant in the upper troposphere. The model mean decrease in relative humidity is −2.3% ± 1.0% K−1 at 250 mb, whereas observations indicate decreases of −4.8% ± 1.7% K−1 near 215 mb. These two values agree within the respective ranges of uncertainty, indicating that current global climate models are simulating the observed behavior of water vapor in the tropical upper troposphere with reasonable accuracy.

scholarly journals Large differences in reanalyses of diabatic heating in the tropical upper troposphere and lower stratosphere

2013 ◽  
Vol 13 (18) ◽  
pp. 9565-9576 ◽  
Author(s):  
J. S. Wright ◽  
S. Fueglistaler
Keyword(s):  
Turbulent Mixing ◽  
Lower Stratosphere ◽  
Heat Budget ◽  
Radiative Heating ◽  
Japan Meteorological Agency ◽  
Latent Heating ◽  
Moist Convection ◽  
Climate Data ◽  
Upper Troposphere ◽  
Tropical Upper Troposphere

Abstract. We present the time mean heat budgets of the tropical upper troposphere (UT) and lower stratosphere (LS) as simulated by five reanalysis models: the Modern-Era Retrospective Analysis for Research and Applications (MERRA), European Reanalysis (ERA-Interim), Climate Forecast System Reanalysis (CFSR), Japanese 25-yr Reanalysis and Japan Meteorological Agency Climate Data Assimilation System (JRA-25/JCDAS), and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis 1. The simulated diabatic heat budget in the tropical UTLS differs significantly from model to model, with substantial implications for representations of transport and mixing. Large differences are apparent both in the net heat budget and in all comparable individual components, including latent heating, heating due to radiative transfer, and heating due to parameterised vertical mixing. We describe and discuss the most pronounced differences. Discrepancies in latent heating reflect continuing difficulties in representing moist convection in models. Although these discrepancies may be expected, their magnitude is still disturbing. We pay particular attention to discrepancies in radiative heating (which may be surprising given the strength of observational constraints on temperature and tropospheric water vapour) and discrepancies in heating due to turbulent mixing (which have received comparatively little attention). The largest differences in radiative heating in the tropical UTLS are attributable to differences in cloud radiative heating, but important systematic differences are present even in the absence of clouds. Local maxima in heating and cooling due to parameterised turbulent mixing occur in the vicinity of the tropical tropopause.

scholarly journals Impact of the new HNO<sub>3</sub>-forming channel of the HO<sub>2</sub>+NO reaction on tropospheric HNO<sub>3</sub>, NO<sub>x</sub>, HO<sub>x</sub> and ozone

2008 ◽  
Vol 8 (14) ◽  
pp. 4061-4068 ◽  
Author(s):  
D. Cariolle ◽  
M. J. Evans ◽  
M. P. Chipperfield ◽  
N. Butkovskaya ◽  
A. Kukui ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Chemical Transport Model ◽  
Temperature Dependent ◽  
Upper Troposphere ◽  
The Mean ◽  
The Tropics ◽  
The Impact

Abstract. We have studied the impact of the recently observed reaction NO+HO2→HNO3 on atmospheric chemistry. A pressure and temperature-dependent parameterisation of this minor channel of the NO+HO2→NO2+OH reaction has been included in both a 2-D stratosphere-troposphere model and a 3-D tropospheric chemical transport model (CTM). Significant effects on the nitrogen species and hydroxyl radical concentrations are found throughout the troposphere, with the largest percentage changes occurring in the tropical upper troposphere (UT). Including the reaction leads to a reduction in NOx everywhere in the troposphere, with the largest decrease of 25% in the tropical and Southern Hemisphere UT. The tropical UT also has a corresponding large increase in HNO3 of 25%. OH decreases throughout the troposphere with the largest reduction of over 20% in the tropical UT. The mean global decrease in OH is around 13%, which is very large compared to the impact that typical photochemical revisions have on this modelled quantity. This OH decrease leads to an increase in CH4 lifetime of 5%. Due to the impact of decreased NOx on the OH:HO2 partitioning, modelled HO2 actually increases in the tropical UT on including the new reaction. The impact on tropospheric ozone is a decrease in the range 5 to 12%, with the largest impact in the tropics and Southern Hemisphere. Comparison with observations shows that in the region of largest changes, i.e. the tropical UT, the inclusion of the new reaction tends to degrade the model agreement. Elsewhere the model comparisons are not able to critically assess the impact of including this reaction. Only small changes are calculated in the minor species distributions in the stratosphere.

Sign in / Sign up

Export Citation Format

Share Document