Hasil untuk "Meteorology. Climatology"

William A. Gough

Abstract Nine urban areas in China are examined using a peri-urban thermal variability metric. Of the nine, four showed some evidence of a peri-urban climate that is linked to the location of the climate station within the urban area. A series of metrics that exploit the subtle variation of temperature variability experienced day to day are used to identify the climate station urbanization characteristics from 1951 to 2023. Metrics that identified the local environment as rural, urban, or peri-urban were used. This peri-urban analysis was employed in this work for the first time using Chinese climate data by examining nine urban areas: Harbin, Shenyang, Shijiazhuang, Jinan, Zhengzhou, Hefei, Wuhan, Nanchang, and Changsha. Harbin, Shenyang, Jinan, and Zhengzhou had distinct peri-urban thermal signatures. Harbin, Heilongjiang, a large city in the northeast of China illustrated most clearly the changing thermal variability characteristics as the local climate station experienced the expanding urban reach of the growing city. The location of its climate station at the fringe of the city in 1951 led to a rural classification for many years. This changed dramatically to peri-urban beginning in the 1980s and to urban in the 2010s and into the 2020s, consistent with the expanding urban sprawl. This research provided some initial insight into the interplay of the various metrics used as the site transitioned from rural to peri-urban to urban.

Guo-Qing Chen, Jian-Sheng Hao, Lan-Hai Li et al.

Climate change has increased temperatures and altered snowpack properties, which in turn affect avalanche activity. The extent to which climate change affects avalanche activity and how avalanche activity responds to climate change remains poorly understood, which hinders avalanche risk assessments under future climate change. In this study, we applied tree-ring evidence from trees affected by avalanches to reproduce historical avalanche events and then combined the observed meteorological and snowpack data to reveal the response mechanism of avalanche activity to climate change in the Tianshan Mountains. The study found that snow seasons with large-scale avalanche events have increased since 1943, which is contrary to the assumption that less snow under a warming climate reduces the risk of avalanches. Snow seasons in which large-scale avalanches occur are characterised by high snow depth in November (>44.4 cm) and April (>60.9 cm), together with low December temperatures (<−1.9 °C) under heavy snowfall (≥34.4 cm). Under climate change, the study area experienced a marked increase in snow-season temperatures along with rising trends in snow depth and heavy snowfall, leading to elevated avalanche risk in the middle altitudes of the western Tianshan Mountains, where human activities are intensive. This study provides a clear understanding of avalanche risk changes in the region under climate change and helps people propose climate-change adaptation strategies for avalanche risk.

Xiang Ji, Yao Fu, Jiaxuan Shi et al.

Serving as the direct interface for interaction between the waterfront and urban dwellers, the street space environment significantly influences people’s living experiences and social interactions. Despite progress in the renovation and development of waterfront streets, these areas remain underutilized and lack the vitality expected of such locations. Using the Hunhe Waterfront Streets in Shenyang as a case study, this research employed Baidu heatmap data and the Semantic Differential method to assess both the behavioral and perceived vitality of the area. Subsequently, the study explored the main factors influencing behavioral vitality in waterfront streets from three aspects: street accessibility, facility configuration and environmental construction. It also examined the key environmental features of waterfront streets that affect perceived vitality under visual perception. Additionally, the study performed a coupling analysis to explore the relationship between behavioral and perceived vitality within the waterfront streets. The results indicated that the density of infrastructure and commercial facilities, as well as the continuity of pedestrian paths, were key environmental features influencing behavioral vitality. The degree of motorization, green visual index and building enclosure ratio were the main environmental features affecting perceived vitality. Moreover, the vitality coordination of the Hunhe Waterfront Streets was relatively poor, leaving considerable room for improvement. By integrating behavior and their perceptions of the environment, the study explored the coordination of waterfront street vitality and its intrinsic connection with street environmental features. This work aids in developing more effective and user-centric design strategies for waterfront streets, offering practical guidance for their revitalization and redevelopment.

Ann-Lise Norman, Sunita LeGallou, Erin E. Caldwell et al.

Tree rings, tree needles, and moss can be used as biomonitors to evaluate atmospheric pollutant concentrations and deposition patterns spanning different timescales. This study compares output from air quality modeling and measurements to patterns observed using a combination of sulfur concentration and isotope composition in moss (using moss bags and controls) as biomonitors in a region of southern Alberta, Canada influenced by industrial emissions. Tree rings allow comparisons of historical to current sulfur deposition patterns. Moss, which integrates atmospheric nutrients during growth, allows for concurrent comparisons. The contrast of inorganic and organic sulfur within conifer tree needles provides a measure of pollutant uptake over their short lifespans. Sulfur uptake within biomonitors in a southern Alberta ecosystem allow assessment of the presence (in moss, needles) and effects (on conifer growth) of atmospheric sulfur deposition from industrial emissions. These data were examined relative to California Puff (CALPuff) model projections and traditional active and passive air quality sampling. Patterns in sulfur isotope abundance (δ³⁴S) from moss bags placed throughout the eastern slopes of the southern Alberta foothills of the Rocky Mountains implicate local industry as the dominant atmospheric sulfur source over winter, with the tissues of conifers (needles and cores) and moss decreasing with distance from industrial emissions. This was consistent with apportionment calculations based on active and passive sampling, which also showed a surprising trend of sulfur deposition upwind of the industrial stack in the mountains to the west. δ³⁴S values for pine needles and tree rings were consistent with greater sulfur stress and reductions in tree growth associated with increased industrial sulfur concentrations and deposition. We conclude that plant biomonitors are effective short-term (tree needles and moss) and long-term (tree cores) indicators of sulfur pollution in a complex, mountainous landscape.

Jiawei Ding, Dan Mei, Bowen Liu et al.

Vehicle acceleration typically occurs at traffic lights, intersections, or congested sections within urban streets, where high densities of pedestrians and vehicles pose a direct threat to respiratory health due to PM_2.5 dispersion. Computational Fluid Dynamics (CFD) simulations, combined with the Dynamic Mode Decomposition (DMD) method, are used to analyze the dynamic characteristics of PM_2.5 dispersion during vehicle acceleration. The DMD method can effectively analyze the dynamic change in pollutant concentration in an unsteady flow field and clarify the influence mechanism of vehicle acceleration on pollutant dispersion. The results indicate that PM_2.5 dispersion during the initial stage of acceleration is primarily influenced by low-frequency and large-scale flows, such as exhaust emissions, natural wind, and trailing vortices. In the middle stage, PM_2.5 dispersion tends to stabilize, while in the final stage, high-frequency modes dominate, and intense flow field fluctuations significantly enhance PM_2.5 dispersion. Furthermore, the analysis reveals the critical role of upward and downward airflow phenomena around the vehicle in driving PM_2.5 dispersion. This study offers a new perspective on the dispersion characteristics of PM_2.5 under unsteady flow conditions in urban streets and provides a scientific basis for developing speed management strategies to mitigate the impact of pollutant dispersion.

Chongzhi Zhong, Jiaxing Sun, Jing Zhang et al.

With the implementation of strict emission regulations and the use of cleaner fuels, there has been a considerable reduction in exhaust emissions. However, the relative contribution of tire wear particles (TWPs) to particulate matters is expected to gradually increase. This study conducted laboratory wear experiments on tires equipped on domestically popular vehicle models, testing the factors and particle size distribution of TWPs. The results showed that the content of tire wear particle emission was mainly ultrafine particles, accounting for 94.80% of particles ranging from 6 nm to 10 μm. There were at least two concentration peaks for each test condition and sample, at 10~13 nm and 23~41 nm, respectively. The mass of TWP emission was mainly composed of fine particles and coarse particles, with concentration peaks at 0.5 μm and 1.3–2.5 μm, respectively. Both the number and mass of TWPs exhibited a bimodal distribution, with significant differences in emission intensity among different tire samples. However, there was a good exponential relationship between PM₁₀ mass emissions from tire wear and tire camber angle. The orthogonal experimental results showed that the slip angle showed the greatest impact on TWP emission, followed by speed and load, with the smallest impact from inclination angle.

Isaiah Kingsberry, Jason Naylor

Abstract This study examines ground-based precipitation observations recorded by a high-density gauge network located within approximately 40 km of the urban center of Louisville, Kentucky. An analysis of April–October events reveals that precipitation is significantly greater on the downwind side of Louisville than on the upwind side, particularly when precipitation systems have a westerly component to their motion. The mean difference between downwind and upwind precipitation across all events is 20%. This value is smaller for widespread precipitation events (i.e., most or all gauges detect precipitation) and is larger for isolated events (i.e., rain detected by one-half of the gauges or fewer). The largest and most significant differences between upwind and downwind precipitation amounts occur in association with moist moderate, moist tropical, and transitional air masses.

Effie Kostopoulou

Zhijian Liu, Hongwei Cao, Chenxing Hu et al.

Abstract Mounting interest in modeling outdoor diffusion and transmission of bioaerosols due to the prevalence of COVID-19 in the urban environment has led to better knowledge of the issues concerning exposure risk and evacuation planning. In this study, the dispersion and deposition dynamics of bioaerosols around a vaccine factory were numerically investigated under various thermal conditions and leakage rates. To assess infection risk at the pedestrian level, the improved Wells-Riley equation was used. To predict the evacuation path, Dijkstra’s algorithm, a derived greedy algorithm based on the improved Wells-Riley equation, was applied. The results show that, driven by buoyancy force, the deposition of bioaerosols can reach 80 m on the windward sidewall of high-rise buildings. Compared with stable thermal stratification, the infection risk of unstable thermal stratification in the upstream portion of the study area can increase by 5.53% and 9.92% under a low and high leakage rate, respectively. A greater leakage rate leads to higher infection risk but a similar distribution of high-risk regions. The present work provides a promising approach for infection risk assessment and evacuation planning for the emergency response to urban bioaerosol leakage.

Jinhu YANG, Qiang ZHANG, Bocheng YANG et al.

The upper Yellow River are located at the intersection of the Qinghai-Xizang Plateau， the Loess Plateau， and the Mongolian Plateau， it is sensitive to climate change and the ecological environment is fragile， it is the main flow-producing area and water conservation area in the Yellow River Basin， the ecological location is very important for the water resources and ecological security of the Yellow River Basin.The upper Yellow River have shown significant warming and humidification characteristics since the beginning of this century， but they are unclear that the multi-time scale characteristics， causes and effects on ecological vegetation of warming and humidification.So， based on various data such as observation， reanalysis， satellite remote sensing and future scenario prediction， using EOF， EEMD and other statistical methods， this paper systematically analyzed the warming and dry-wet characteristics of the upper Yellow River for more than half a century， and discussed the causes of current warming and humidification and its impact on ecological vegetation.It is found that the upper reaches of the Yellow River average temperature have increased at a rate of 0.37 °C·（10a）-1 since 1961， which is more obvious than that of the whole world， the whole country and even the whole northwest.Precipitation shows obvious interdecadal changes， which has increased significantly at a rate of 32 mm·（10a）-1 since 1997.Therefore， the upper reaches of the Yellow River have shown an obvious warming-wetting trend since 1997.From the perspective of spatial anomaly distribution characteristics， temperature and precipitation are mainly dominated by regional consistent modal changes.From the point of view of multi-time scale changes， the average temperature is mainly dominated by long-term trend changes， followed by inter-annual changes， and precipitation is mainly dominated by inter-annual changes， followed by multi-decadal changes.The reason for the continuous warming since 1961 is mainly the result of an increase of the average temperature trend component.The obvious humidification trend since 1997 is mainly due to the humidifying channel at the multi-decadal weight of precipitation over 30 years.From the perspective of spatial dynamic changes， the upper reaches of the Yellow River in each climatic period from 1961 to 2010 showed overall warming and drying， but the drying trend slowed down by climatic period， and the region showed consistent warming and drying from 1991 to 2020.The variation of precipitation in the upper reaches of the Yellow River is mainly affected by the westerly， East Asian summer monsoon and South Asian summer monsoon.However， the circulation factors affected are quite different at multi time scales.The interannual scale is mainly affected by the single circulation factor of the South Asian summer monsoon， the interdecadal scale is mainly affected by the westerly and South Asian summer monsoon， and the multi-decadal scale is mainly affected by the westerly and South Asian summer monsoon circulation.The wetting trend since 1997 is mainly the result of the enhancement of the westerly and South Asian summer monsoon circulation.It is expected that the upper reaches of the Yellow River will continue to show a warming and wetting trend in the next 80 years， and the warming trend is basically the same as that at present， while the wetting trend is significantly weaker than that at present.Water and heat conditions is insufficient in the upper reaches of the Yellow River， and ecological vegetation has a certain dependence on the average temperature and precipitation in the past three months， and the stronger dependence on precipitation in the same period.In addition， the average temperature has a longer lag effect on ecological vegetation than precipitation， Average temperature and precipitation have a synergistic effect on ecological vegetation.A warm and wet climate is the most conducive to vegetation growth， while a cold and dry climate is not.The warming and wetting climate makes the ecological vegetation in the upper reaches of the Yellow River tend to be good in the recent 20 years， and warming and wetting trend may make ecological vegetation continue to improve in the next years.

B. M. Swiger, M. W. Liemohn, N. Y. Ganushkina et al.

Abstract Suprathermal electrons in the near‐Earth plasma sheet are important for inner magnetosphere considerations. They are the source population for outer radiation belt electrons and they pose risks to geosynchronous satellites through their contribution to surface charging. We use empirical modeling to address relationships between solar driving parameters and plasma sheet electron flux. Using Time History of Events and Macroscale Interactions during Substorms, OMNI, and Flare Irradiance Spectral Model Version 2 data, we develop a neural network model to predict differential electron flux from 0.08 to 93 keV in the plasma sheet, at distances from 6 to 12 RE. Driving parameters include solar wind (SW) density and speed, interplanetary magnetic field (IMF) BZ and BY, solar extreme ultraviolet flux, IMF BZ ultra‐low frequency (ULF) wave power, SW‐magnetosphere coupling functions Pα1 and NXCF, and the 4‐hr time history of these parameters. Our model predicts overall plasma sheet electron flux variations with correlation coefficients of between 0.59 and 0.77, and median symmetric accuracy in the 41%–140% range (depending on energy). We find that short time‐scale electron flux variations are not reproduced using short time‐scale inputs. Using a recently published technique to extract information from neural networks, we determine the most important drivers impacting model prediction are VSW, VBS, and IMF BZ. SW‐magnetosphere coupling functions that include IMF clock angle, IMF BZ ULF wave power, and IMF BY have little impact in our model of electron flux in the near‐Earth plasma sheet. The new model, built directly on differential flux, outperforms an existing model that derives fluxes from plasma moments, with the performance improvement increasing with increasing energy.

Melanie Schroers, Elinor Martin

Abstract Long periods of extreme precipitation can cause costly damages to a region’s infrastructure while also creating a higher risk for the region’s population. Planning for these periods would ideally begin at the subseasonal-to-seasonal time scale, yet prediction of precipitation at this time scale has low skill. In this study, we will use Jennrich et al.’s database of 14-day extreme precipitation events to understand more about the synoptic connections and impacts of these extended extreme events. The synoptic connections of events were examined using the composites of event-day 500-hPa geopotential height and precipitable water anomalies. The combination of these two drivers leads to higher skill in the West Coast and Great Lakes than other regions, with an equitable threat score of 0.137 and 0.084, respectively, and higher conditional probabilities of event occurrence. Therefore, the synoptic patterns associated with events, although significant, are not unique, which poses prediction challenges. Historical impacts of these events, using NCEI storm reports, were assessed to benefit decision-makers in future risk mitigation. A variety of reports were found during events, from winter weather reports in West Coast events to tropical storm reports in Southeast events. Every region has significantly more flooding reports during events than in nonextreme 14-day periods, demonstrating the impacts of such extended events. Although there is still much to learn about extreme precipitation events, this study contributes to the foundational knowledge of synoptic drivers and impacts of events.

Karthik Balaguru, L. Ruby Leung, Samson M. Hagos et al.

Abstract While the Madden–Julian Oscillation (MJO) has been shown to affect tropical cyclones (TCs) worldwide through its modulation of large-scale circulation in the atmosphere, little or no role for the ocean has been identified to date in this influence of MJO on TCs. Using observations and numerical model simulations, we demonstrate that MJO events substantially impact TCs over the Maritime Continent (MC) region through an oceanic pathway. While propagating across the MC region, MJO events cause significant sea surface cooling with an area-averaged value of about 0.35 ± 0.12 °C. Hence, TCs over the MC region immediately following the passage of MJO events encounter considerably cooler sea surface temperatures. Consequently, the enthalpy fluxes under the storms are reduced and the intensification rates decrease by more than 50% on average. These results highlight an important role played by the ocean in facilitating MJO-induced sub-seasonal variability in TC activity over the MC region.

Anna A. Shestakova, Stanislav A. Myslenkov, Alexandra M. Kuznetsova

This paper investigates for the first time sea waves during Novaya Zemlya bora—a downslope windstorm on the western coast of the archipelago during eastern winds—using a statistical and case-study approach. Statistical analysis of altimeter data off the western coast of Novaya Zemlya during bora shows that, despite strong wind forcing, the frequency of hazard wave heights was low due to the limited fetch. This result was confirmed by the high-resolution numerical simulations of two severe bora episodes. However, the influence of bora on sea waves in some cases was significant: bora increased wave height at a distance from shore greater than 200 km and wave height anomaly was up to 2–3 m. The influence of the wind input parametrization choice during bora is great in the coastal region; however, parametrizations with fetch-limited modifications and strong-wind adopted aerodynamic drag coefficient do not improve the modeling results in the open sea where altimeter data are available.

Bainian Ren, Jiping Zhu, Lijiang Tian et al.

Intermediate volatile organic compounds (IVOCs) have attracted much attention due to their contributions to the formation of secondary organic aerosol (SOA) in ambient air. Determination of total IVOCs in ambient air is therefore important for assessing their roles in air pollution. Currently, concentrations of IVOCs are estimated using a previously published semi-quantitative method. In this paper we propose an alternative method for the determination of IVOCs concentrations, in which speciated IVOCs of n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and phthalates are treated as speciated IVOCs and quantified using their respective standards. The ion signal attributed to the speciated IVOCs is then subtracted from the total ion chromatogram (TIC) and the remaining peak area is used to semi-quantitatively estimate the remaining mass regarded as unspeciated complex mixture (UCM) IVOCs. The TIC peak area of speciated IVOCs in ambient air samples is reconstructed based on the peak area ratio of extracted ion chromatogram (EIC) of the quantifying ion and the TIC from their respective standards. The total IVOCs is then calculated as the sum of the speciated IVOCs and the UCM IVOCs. Twenty-one ambient air samples, collected from November 7 to December 12, 2018 in the urban area of Shanghai, were used to compare our method with the previously published method. Although the overall differences in UCM IVOCs and total IVOCs values were small between the two methods, different values of UCM IVOCs and total IVOCs in several sections of the chromatogram that contain phthalates were observed. Analysis of the ambient air samples also revealed that levels of IVOCs were significantly correlated with atmospheric PM2.5. Our method has the advantage that more accurate results in the determination of total IVOCs can be achieved when more compounds are identified and added to the list of speciated IVOCs.

Judah Detzer, Paul C. Loikith, Luana Albertani Pampuch et al.

AbstractKey spatiotemporal patterns of monthly scale temperature variability are characterized over southern South America using k‐means clustering. The resulting clusters reveal patterns of temperature variability, referred to as temperature variability states. Analysis is performed over summer and winter months separately using data covering the period 1980–2015. Results for both seasons show four primary temperature variability states. In both seasons, one state is primarily characterized by warm temperature anomalies across the domain while another is characterized by cold anomalies. The other two patterns tend to be characterized by a warm north–cold south and cold north–warm south feature. This suggests two primary modes of temperature variability over the region. Composites of synoptic‐scale meteorological patterns (wind, geopotential height, and moisture fields) are computed for months assigned to each cluster to diagnose the driving meteorology associated with these variability states. Results suggest that low‐level temperature advection promoted by anomalies in atmospheric circulation patterns is a key process for driving these variability states. Moisture‐related processes also are shown to play a role, especially in summer. The El Niño–Southern Oscillation and the Southern Annular Mode exhibit some relationship with temperature variability state frequency, with some states more common during amplified phases of these two modes than others. However, the climate modes are not a primary driver of the temperature variability states.

Robinson Zachary D., Adams James H., Xapsos Michael A. et al.

A new database of proton episode-integrated fluences is described. This database contains data from two different instruments on multiple satellites. The data are from instruments on the Interplanetary Monitoring Platform-8 (IMP8) and the Geostationary Operational Environmental Satellites (GOES) series. A method to normalize one set of data to one another is presented to create a seamless database spanning 1973 to 2016. A discussion of some of the characteristics that episodes exhibit is presented, including episode duration and number of peaks. As an example of what can be understood about episodes, the July 4, 2012 episode is examined in detail. The coronal mass ejections and solar flares that caused many of the fluctuations of the proton flux seen at Earth are associated with peaks in the proton flux during this episode. The reasoning for each choice is laid out to provide a reference for how CME and solar flares associations are made.

Nicola Golding, Chris Hewitt, Peiqun Zhang et al.

The needs of decision makers in China are being used to develop climate science and climate services through the Climate Science for Services Partnership. Focusing on examples of work for the energy and urban sectors, this paper outlines the approach taken and gives case studies of climate service development. We find that there is great opportunity for climate service development within the existing China Framework for Climate Services, and for enhancing the science that underpins such services. We also find challenges unique to the socio-economic and cultural environment in China, which must be taken into account when developing climate services here, as well as challenges common to all climate service development.

M. Maturilli, A. Herber, G. König-Langlo

Abstract. A consistent meteorological dataset of the Arctic site Ny-Ålesund (11.9° E, 78.9° N) spanning the 18 yr-period 1 August 1993 to 31 July 2011 is presented. Instrumentation and data handling of temperature, humidity, wind and pressure measurements are described in detail. Monthly mean values are shown for all years to illustrate the interannual variability of the different parameters. Climatological mean values are given for temperature, humidity and pressure. From the climatological dataset, we also present the time series of annual mean temperature and humidity, revealing a temperature increase of +1.35 K per decade and an increase in water vapor mixing ratio of +0.22 g kg−1 per decade for the given time period, respectively. With the continuation of the presented measurements, the Ny-Ålesund high resolution time series will provide a reliable source to monitor Arctic change and retrieve trends in the future. The relevant data are provided in high temporal resolution as averages over 5 (1) min before (after) 14 July 1998, respectively, placed on the PANGAEA repository (doi:10.1594/PANGAEA.793046). While 6 hourly synoptic observations in Ny-Ålesund by the Norwegian Meteorological Institute reach back to 1974 (Førland et al., 2011), the meteorological data presented here cover a shorter time period, but their high temporal resolution will be of value for atmospheric process studies on shorter time scales.

Suzana J. Camargo, Adam H. Sobel, Anthony D. Delgenio et al.

The authors describe the characteristics of tropical cyclone (TC) activity in the GISS general circulation ModelE2 with a horizontal resolution 1°×1°. Four model simulations are analysed. In the first, the model is forced with sea surface temperature (SST) from the recent historical climatology. The other three have different idealised climate change simulations, namely (1) a uniform increase of SST by 2 degrees, (2) doubling of the CO2 concentration and (3) a combination of the two. These simulations were performed as part of the US Climate Variability and Predictability Program Hurricane Working Group. Diagnostics of standard measures of TC activity are computed from the recent historical climatological SST simulation and compared with the same measures computed from observations. The changes in TC activity in the three idealised climate change simulations, by comparison with that in the historical climatological SST simulation, are also described. Similar to previous results in the literature, the changes in TC frequency in the simulation with a doubling CO2 and an increase in SST are approximately the linear sum of the TC frequency in the other two simulations. However, in contrast with previous results, in these simulations the effects of CO2 and SST on TC frequency oppose each other. Large-scale environmental variables associated with TC activity are then analysed for the present and future simulations. Model biases in the large-scale fields are identified through a comparison with ERA-Interim reanalysis. Changes in the environmental fields in the future climate simulations are shown and their association with changes in TC activity discussed.