scholarly journals Vertical air motions derived from a descending radiosonde using a lightweight hard ball as the parachute

2013 ◽  
Vol 6 (5) ◽  
pp. 8107-8127 ◽  
Author(s):  
H. Chen ◽  
Y. Zhu ◽  
J. Zhang ◽  
Y. Xuan
Keyword(s):  
Northern China ◽  
Lower Atmosphere ◽  
Radiosonde Data ◽  
Small Magnitude ◽  
Abstract Knowledge ◽  
Launch Site ◽  
Wind Profiler Radar ◽  
Vertical Wind Speed ◽  
The Difference ◽  
Hard Ball

Abstract. Knowledge of vertical air motions in the atmosphere is important for meteorological and climate studies due to its impact on clouds, precipitation and the vertical transport of air masses, heat, momentum, and composition. It is among the most difficult quantities to measure because of its small magnitude. In this study, a descending radiosonde technique has been developed to detect the vertical wind speed (VW) in the atmosphere. The system is composed of a radiosonde and a 0.5-m diameter hard ball made of plastic foam that acts as a parachute. The radiosonde hangs under the hard ball by a string which is then cut when the instrument is elevated into the upper troposphere by a balloon. The VW is derived from the difference between the observed radiosonde descent rate and the calculated radiosonde descent rate in still air based on fluid dynamics. Deduction of the appropriate drag coefficient for the radiosonde is facilitated by the symmetrical shape of the parachute. An intensive radiosonde launch experiment was held in northern China during the summer seasons of 2010 to 2012. This study uses radiosonde data collected during the campaign to retrieve the vertical air velocity within the radiosonde altitude-detecting range. In general, the VW ranges from −1 to 1 m s−1. Strong vertical air motion (~2 m s−1) is seen in a few radiosonde measurements. Although considerable uncertainties exist in measuring weak vertical air motions, a case study shows that there is reasonable agreement between retrievals of VW in the lower atmosphere from the radiosonde and a wind profiler radar located at the launch site.

scholarly journals Spatial and seasonal variability of medium- and high-frequency gravity waves in the lower atmosphere revealed by US radiosonde data

2014 ◽  
Vol 32 (9) ◽  
pp. 1129-1143 ◽  
Author(s):  
S. D. Zhang ◽  
C. M. Huang ◽  
K. M. Huang ◽  
F. Yi ◽  
Y. H. Zhang ◽  
...  
Keyword(s):  
Energy Density ◽  
Gravity Waves ◽  
Seasonal Variability ◽  
High Frequency ◽  
Lower Atmosphere ◽  
Radiosonde Data ◽  
High Latitudes ◽  
Middle Latitudes ◽  
Momentum Fluxes ◽  
Horizontal Momentum

Abstract. We extended the broad spectral method proposed by Zhang et al. (2013) for the extraction of medium- and high-frequency gravity waves (MHGWs). This method was applied to 11 years (1998–2008) of radiosonde data from 92 stations in the Northern Hemisphere to investigate latitudinal, continuous vertical and seasonal variability of MHGW parameters in the lower atmosphere (2–25 km). The latitudinal and vertical distributions of the wave energy density and horizontal momentum fluxes as well as their seasonal variations exhibit considerable consistency with those of inertial gravity waves. Despite the consistency, the MHGWs have much larger energy density, horizontal momentum fluxes and wave force, indicating the more important role of MHGWs in energy and momentum transportation and acceleration of the background. For the observed MHGWs, the vertical wavelengths are usually larger than 8 km; the horizontal wavelengths peak in the middle troposphere at middle–high latitudes. These characteristics are obviously different from inertial gravity waves. The energy density and horizontal momentum fluxes have similar latitude-dependent seasonality: both of them are dominated by a semiannual variation at low latitudes and an annual variation at middle latitudes; however at high latitudes, they often exhibit more than two peaks per year in the troposphere. Compared with the inertial GWs, the derived intrinsic frequencies are more sensitive to the spatiotemporal variation of the buoyancy frequency, and at all latitudinal regions they are higher in summer. The wavelengths have a weaker seasonal variation; an evident annual cycle can be observed only at middle latitudes.

scholarly journals Urban heat island: Aerodynamics or imperviousness?

2019 ◽  
Vol 5 (4) ◽  
pp. eaau4299 ◽  
Author(s):  
Dan Li ◽  
Weilin Liao ◽  
Angela J. Rigden ◽  
Xiaoping Liu ◽  
Dagang Wang ◽  
...  
Keyword(s):  
Green Infrastructure ◽  
Rural Areas ◽  
Land Surface ◽  
Urban Heat Islands ◽  
Lower Atmosphere ◽  
Geographic Variations ◽  
Heat Islands ◽  
Urban Heat ◽  
The Difference ◽  
Urban And Rural Areas

More than half of the world’s population now live in cities, which are known to be heat islands. While daytime urban heat islands (UHIs) are traditionally thought to be the consequence of less evaporative cooling in cities, recent work sparks new debate, showing that geographic variations of daytime UHI intensity were largely explained by variations in the efficiency with which urban and rural areas convect heat from the land surface to the lower atmosphere. Here, we reconcile this debate by demonstrating that the difference between the recent finding and the traditional paradigm can be explained by the difference in the attribution methods. Using a new attribution method, we find that spatial variations of daytime UHI intensity are more controlled by variations in the capacity of urban and rural areas to evaporate water, suggesting that strategies enhancing the evaporation capability such as green infrastructure are effective ways to mitigate urban heat.

scholarly journals Wave Modeling—Missing the Peaks

2009 ◽  
Vol 39 (11) ◽  
pp. 2757-2778 ◽  
Author(s):  
Luigi Cavaleri
Keyword(s):  
Wave Model ◽  
Sensitivity Study ◽  
New Physics ◽  
Lower Atmosphere ◽  
Physical Interaction ◽  
Extreme Conditions ◽  
Wind Variability ◽  
Nonlinear Energy Transfer ◽  
The Difference ◽  
Wave Models

Abstract The paper analyzes the capability of the present wave models of properly reproducing the conditions during and at the peak of severe and extreme storms. After providing evidence that this is often not the case, the reasons for it are explored. First, the physics of waves considered in wave models is analyzed. Although much improved with respect to the past, the wind accuracy is still a relevant factor at the peak of the storms. Other factors such as wind variability and air density are considered. The classical theory of wave generation by J. W. Miles’s mechanism, with subsequent modifications, is deemed not sufficiently representative of extreme conditions. The presently used formulations for nonlinear energy transfer are found to lead to too wide distributions in frequency and direction, hence reducing the input by wind. Notwithstanding some recent improvements, the white-capping formulation still depends on parameters fitted to the bulk of the data. Hence, it is not obvious how they will perform in extreme conditions when the physics is likely to be different. Albeit at different levels in different models, the advection still implies the spreading of energy, hence a spatial smoothing of the peaks. The lack of proper knowledge of the ocean currents is found to substantially affect the identification of how much energy can—in some cases—be concentrated at a given time and location. The implementation of the available theories and know-how in the present wave models are often found inconsistent from model to model. It follows that in this case, it is not possible to exchange corresponding pieces of software between two models without substantially affecting the quality of the results. After analyzing various aspects of a wave model, the paper makes some general considerations. Because wave growth is the difference between processes (input and output) involving large amounts of energy, it is very sensitive to small modifications of one or more processes. Together with the strong, but effective, tuning present in a wave model, this makes the introduction of new physics more complicated. It is suggested that for long-term improvements, operational and experimental applications need to proceed along parallel routes, with the latter looking more to the physics without the necessity of an immediately improved overall performance. In view of the forthcoming increase of computer power, a sensitivity study is suggested to identify the most critical areas in a wave model to determine where to invest for further improvements. The limits on the description of the physics of the processes when using the spectral approach, particularly in extreme conditions, are considered. For further insights and as a way to validate the present theories in these conditions, the use is suggested of numerical experiments simulating in great detail the physical interaction between the lower atmosphere and the single waves.

Aerosol pH and regime transition of sulfate formation in aerosol water during winter haze events in northern China

2020 ◽  
Author(s):  
Wei Tao ◽  
Hang Su ◽  
Guangjie Zheng ◽  
Jiandong Wang ◽  
Lixia Liu ◽  
...  
Keyword(s):  
Northern China ◽  
Chem Phys ◽  
Heterogeneous Reactions ◽  
Lower Atmosphere ◽  
Spatial And Temporal Variability ◽  
Oh Radicals ◽  
Night Time ◽  
Sulfate Formation ◽  
Iron Manganese ◽  
The Impact

<p>Understanding the formation mechanism of severe haze is crucial for the development of efficient pollution control strategy. Recently, multiphase reactions in aerosol water has been suggested as an important source of sulfate aerosol during severe haze (Zheng et al., 2015;Cheng et al., 2016). Though several oxidation mechanisms have been recognized, the dominant oxidation pathway is still under debate reflecting a missing consensus. Based on a model survey with Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), we have investigated the variability of aerosol pH and regimes of sulfate formation through multiphase oxidation during the haze episodes in January of 2013. Our results show a large spatial and temporal variability in the aerosol pH and sulfate formation regimes. Surface aerosol pH shows a clear diurnal variation with low pH during daytime and high pH during night-time for most cases. Aerosol pH tends to decrease with increasing altitude in the lower atmosphere. For the scenario best reproduces the observations in Beijing, NO<sub>2</sub>, TMI+O<sub>2</sub>, O<sub>3</sub> and H<sub>2</sub>O<sub>2</sub> pathways can all dominate the production of sulfate in specific areas of the Beijing-Tianjin-Hebei (BTH) region. With the increasing height, O<sub>3</sub> pathway and gas phase oxidation by OH radicals become more important. Moreover, sensitivity tests also suggest that, emissions of crustal particles, NH<sub>3</sub> and soluble iron/manganese have great impacts on aqueous phase chemistry, and should be better constrained in future studies.</p><p>References:</p><p>Zheng, G. J., Duan, F. K., Su, H., Ma, Y. L., Cheng, Y., Zheng, B., Zhang, Q., Huang, T., Kimoto, T., Chang, D., Poschl, U., Cheng, Y. F., and He, K. B.: Exploring the severe winter haze in Beijing: the impact of synoptic weather, regional transport and heterogeneous reactions, Atmos. Chem. Phys., 15, 2969-2983, 10.5194/acp-15-2969-2015, 2015.</p><p>Cheng, Y. F., Zheng, G. J., Wei, C., Mu, Q., Zheng, B., Wang, Z. B., Gao, M., Zhang, Q., He, K. B., Carmichael, G., Poschl, U., and Su, H.: Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China, Sci Adv, 2, e1601530, UNSP e1601530,10.1126/sciadv.1601530, 2016.</p>

Gamma rays in the MeV region at balloon altitude

1968 ◽  
Vol 46 (10) ◽  
pp. S494-S497 ◽  
Author(s):  
K. Okudaira ◽  
Y. Hirasima
Keyword(s):  
Gamma Rays ◽  
Main Part ◽  
Counting Rate ◽  
Gamma Ray ◽  
Plastic Scintillator ◽  
Scintillation Counter ◽  
Lower Atmosphere ◽  
Upper Limit ◽  
Extraterrestrial Origin ◽  
The Difference

Gamma rays in the MeV region were observed from balloons at λ = 26 °N on September 29, 1966. A scintillation counter constructed with two NaI ⅓ in. × 2 in. [Formula: see text] crystals separated by 1 cm × 2 in. [Formula: see text] lead was used to measure the directional distribution of the gamma-ray flux. This counter was flown at an atmospheric depth of 14.2 g cm−2. As the response of each crystal of this counter depends on the direction of incidence of the gamma rays, an anisotropic distribution of gamma rays gives rise to a difference between the counting rates of two crystals. It was ascertained from the observation that albedo gamma rays from the lower atmosphere are predominant at this high altitude. The deviation from the calculated values of the difference in counting rate assuming only atmospheric gamma rays may be due to an extraterrestrial origin of part of the gamma-ray flux. For the measurement of the gamma-ray spectrum, a phoswich counter (1 in. × 1 in. [Formula: see text] NaI crystal surrounded by ¼-in.-thick plastic scintillator) was flown to 10 g cm−2. Though the main part of the gamma-ray flux is probably due to atmospheric gamma rays, an upper limit for the isotropic cosmic gamma-ray flux is deduced to be (1.25 ± 0.05) × 10−2 counts cm−2 s−1 sr−1 MeV−1 in the energy range 1.2–3.1 MeV.

Numerical Models of Wind Effects on Temperature Loaded Object

2017 ◽  
Vol 738 ◽  
pp. 69-78
Author(s):  
Vladimira Michalcova ◽  
Lenka Lausova ◽  
Iveta Skotnicova ◽  
Sergej Kuznetsov
Keyword(s):  
Transport Model ◽  
Numerical Models ◽  
Simulation Models ◽  
Lower Atmosphere ◽  
Small Scale ◽  
Ansys Fluent ◽  
Eddy Simulation ◽  
Wide Range ◽  
Shear Stress Transport Model ◽  
The Difference

Wind climate influencing wind loads on buildings and other structures, as well as the dispersion of pollutants from various surfaces is essentially determined by small-scale motions and processes occurring in the atmospheric boundary layer (ABL). The physical and thermal properties of the underlying surface, in conjunction with the dynamics and thermodynamics of the lower atmosphere influence the distribution of wind velocity in thermally stratified ABL. Atmospheric turbulence is characterized by a high degree of irregularity, three-dimensionality, diffusivity, dissipation, and a wide range of motion scales. This article describes a change of selected turbulent variables in the surroundings of flow around a thermally loaded object. The problem is solved numerically in Ansys Fluent 13.0 software using LES (Large eddy simulation) models as well as the Transition SST (Shear Stress Transport) model that is able to take into account the difference between high and low turbulence at the interface between the wake behind an obstacle and the free stream. The results are mutually compared and verified with experimental measurements in the wind tunnel.

Trends in Tropospheric Humidity from 1970 to 2008 over China from a Homogenized Radiosonde Dataset

2012 ◽  
Vol 25 (13) ◽  
pp. 4549-4567 ◽  
Author(s):  
Tianbao Zhao ◽  
Aiguo Dai ◽  
Junhong Wang
Keyword(s):  
Spatial Coherence ◽  
Vertical Motion ◽  
Precipitable Water ◽  
Northern China ◽  
Northwest China ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Clapeyron Equation ◽  
Dipole Pattern ◽  
Highly Correlated

Abstract Radiosonde humidity data provide the longest record for assessing changes in atmospheric water vapor, but they often contain large discontinuities because of changes in instrumentation and observational practices. In this study, the variations and trends in tropospheric humidity (up to 300 hPa) over China are analyzed using a newly homogenized radiosonde dataset. It is shown that the homogenization removes the large shifts in the original records of dewpoint depression (DPD) resulting from sonde changes in recent years in China, and it improves the DPD’s correlation with precipitation and the spatial coherence of the DPD trend from 1970 to 2008. The homogenized DPD data, together with homogenized temperature, are used to compute the precipitable water (PW), whose correlation with the PW from ground-based global positioning system (GPS) measurements at three collocated stations is also improved after the homogenization. During 1970–2008 when the record is relatively complete, tropospheric specific humidity after the homogenization shows upward trends, with surface–300-hPa PW increasing by about 2%–5% decade−1 over most of China and by more than 5% decade−1 over northern China in winter. The PW variations and changes are highly correlated with those in lower–midtropospheric mean temperature (r = 0.83), with a dPW/dT slope of ~7.6% K−1, which is slightly higher than the 7% K−1 implied by Clausius–Clapeyron equation with a constant relative humidity (RH). The radiosonde data show only small variations and weak trends in tropospheric RH over China. An empirical orthogonal function (EOF) analysis of the PW reveals several types of variability over China, with the first EOF (31.4% variance) representing an upward PW trend over most of China (mainly since 1987). The second EOF (12.0% variance) shows a dipole pattern between Southeast and Northwest China and it is associated with a similar dipole pattern in atmospheric vertical motion. This mode exhibits mostly multiyear variations that are significantly correlated with Pacific decadal oscillation (PDO) and ENSO indices.

scholarly journals Chinese University Students’ Experience of WeChat-Based English-Language Vocabulary Learning

2021 ◽  
Vol 11 (9) ◽  
pp. 554
Author(s):  
Fan Li ◽  
Si Fan ◽  
Yanjun Wang ◽  
Jinjin Lu
Keyword(s):  
University Students ◽  
Language Proficiency ◽  
Test Scores ◽  
Online Teaching ◽  
English Language ◽  
Northern China ◽  
Chinese University ◽  
Chinese University Students ◽  
The Difference ◽  
The Many

The outbreak of COVID-19 worldwide in 2020 has posed tremendous challenges to higher education globally. Teaching English as a foreign language (TEFL) is among the many areas affected by the pandemic. The unexpected transition to online teaching has increased challenges for improving and/or retaining students’ language proficiency. WeChat, a popular social application in China, was widely used for TEFL at Chinese universities before COVID-19. However, it remains unclear whether the use of WeChat can facilitate Chinese university students’ English-language lexical proficiency during the pandemic. To fill this gap, the aim of the present study was two-fold: (1) it initially explored the relationship between the variables including students’ academic years, genders, and academic faculties/disciplines, and their lexical proficiency; and (2) it evaluated the effectiveness of a WeChat-assisted lexical learning (WALL) program in facilitating learning outcomes of English-language vocabulary. One hundred and thirty-three students at a university in Northern China participated in the WALL program for three weeks. As the results indicated, the independent variables had no correlation with the students’ lexical proficiency. More importantly, the students had a decline in the test scores after using the program, compared to their initial test scores. Moreover, the difference was reported to be medium. The findings further proposed questions on applying WeChat to vocabulary teaching in a large-scaled transition. The study is expected to provide insights for tertiary institutions, language practitioners, and student stakeholders to troubleshoot the potential problems regarding implementing WeChat-based TEFL pedagogies.

scholarly journals Bias Correction of the Ratio of Total Column CH4 to CO2 Retrieved from GOSAT Spectra

2020 ◽  
Vol 12 (19) ◽  
pp. 3155
Author(s):  
Haruki Oshio ◽  
Yukio Yoshida ◽  
Tsuneo Matsunaga ◽  
Nicholas M. Deutscher ◽  
Manvendra Dubey ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Mole Fraction ◽  
Bias Correction ◽  
Lower Atmosphere ◽  
Total Carbon ◽  
Dry Air ◽  
Scattering Effects ◽  
The Mean ◽  
The Difference ◽  
Total Column

The proxy method, using the ratio of total column CH4 to CO2 to reduce the effects of common biases, has been used to retrieve column-averaged dry-air mole fraction of CH4 from satellite data. The present study characterizes the remaining scattering effects in the CH4/CO2 ratio component of the Greenhouse gases Observing SATellite (GOSAT) retrieval and uses them for bias correction. The variation of bias between the GOSAT and Total Carbon Column Observing Network (TCCON) ratio component with GOSAT data-derived variables was investigated. Then, it was revealed that the variability of the bias could be reduced by using four variables for the bias correction—namely, airmass, 2 μm band radiance normalized with its noise level, the ratio between the partial column-averaged dry-air mole fraction of CH4 for the lower atmosphere and that for the upper atmosphere, and the difference in surface albedo between the CH4 and CO2 bands. The ratio of partial column CH4 reduced the dependence of bias on the cloud fraction and the difference between hemispheres. In addition to the reduction of bias (from 0.43% to 0%), the precision (standard deviation of the difference between GOSAT and TCCON) was reduced from 0.61% to 0.55% by the correction. The bias and its temporal variation were reduced for each site: the mean and standard deviation of the mean bias for individual seasons were within 0.2% for most of the sites.

scholarly journals Characteristics and Source of Dissolved Organic Matter in Lake Hulun, A Large Shallow Eutrophic Steppe Lake in Northern China

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 953
Author(s):  
Wenwen Wang ◽  
Binghui Zheng ◽  
Xia Jiang ◽  
Junyi Chen ◽  
Shuhang Wang
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Temporal Distribution ◽  
Northern China ◽  
High Concentration ◽  
Excitation Emission Matrix ◽  
Occurrence Characteristics ◽  
Parallel Factor ◽  
The Difference ◽  
High Degree

Lake Hulun, the fifth largest lake in China, is a typical eutrophic steppe lake located in the Hulun Buir Prairie. The dissolved organic matter (DOM) in the water of Lake Hulun has a high concentration. However, little is known about the occurrence characteristics and source of the DOM in Lake Hulun. The spatial and temporal distribution characteristics of DOM concentration in Lake Hulun were thoroughly surveyed, and the optical characteristics, fluorescence components and sources of DOM were analyzed by excitation emission matrix (EMM) and parallel factor analysis (PARAFAC) technology. The DOM concentration was 6.46–42.87 mg C/L, and was highest in summer and lowest in winter. The difference in the spatial distribution of DOM in winter was significant due to the ice over, and showed a trend where the concentration near the shore was higher than that in the center of the lake. Three humic-like components and one component consisting of a mixture of humic-like and protein-like substances of DOM were identified, with the former being prevalent. The humification index of DOM was 2.22–9.92, indicating that the DOM has a high degree of humification. The DOM is mainly derived from terrestrial sources, with the highest proportion (91.0% ± 8.1%) found in winter and the lowest (66.2% ± 7.7%) in summer. Given that the DOM in Lake Hulun is mainly dominated by humic-like components with a high degree humification, the DOM may have low bioactivity. However, this is just a preliminary analysis and judgment, and it is necessary to conduct other experiments such as biodegradation experiments to further study the bioavailability of DOM in Lake Hulun.

Sign in / Sign up

Export Citation Format

Share Document