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1.
The NCEP–NCAR reanalysis dataset and the Had ISST dataset(1959–2014) are used to analyze the impact of two types of El Nio events, i.e., eastern Pacific El Nio(EP-El Nio) and central Pacific El Nio(CP-El Nio) events, on the duration of major and minor sudden stratospheric warmings(SSWs) in Northern Hemisphere winter(November to February). Although the frequency of major and minor SSWs during different types of El Nio shows no distinct differences, the duration of both major and minor SSWs during CP-El Nio is shorter than that during EP-El Nio. The spatial distribution of geopotential height anomalies preceding major SSWs resembles the western Pacific(WP) teleconnection pattern, while the spatial distribution of geopotential height anomalies preceding minor SSWs bears similarity to the Pacific–North America(PNA)teleconnection pattern. An enhancement of the strength of both wavenumber 1 and wavenumber 2 is found before major SSWs. Before minor SSWs, wavenumber 1 is also strengthened, but wavenumber 2 is weakened. The analysis also reveals that EP-El Nio tends to induce positive phases of PNA and WP teleconnections, while CP-El Nio induces negative-phase WP teleconnection. As the positive phases of the PNA and WP teleconnections are related to the strengthening of wavenumber 1, EP-El Nio causes an enhancement of wavenumber 1 in the high-latitude upper troposphere and an enhancement of the upward wave flux in the high-latitude stratosphere, accompanied by a negative anomaly in Eliassen–Palm flux divergence in the subpolar stratosphere, which accounts for the longer SSW duration during EP-El Nio than during CP-El Nio. 相似文献
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The Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary-layer (PBL) scheme is a second-order turbulence closure model that is an improved version of the Mellor–Yamada scheme based on large-eddy simulation data. It simulates PBL structure and evolution well, particularly over the ocean surface. However, when used with various underlying surfaces in China, the scheme overestimates the turbulent momentum flux and the sensible heat flux. Based on observations of surface fluxes in China, we attempt to improve the MYNN model by modifying the parameters and representation of the turbulence scale. Closure constants and empirical expressions in the diagnostic equation are chosen first, and an additional component of the turbulent heat flux is considered in the potential temperature prognostic equation to improve the surface heat-flux modelling. The modified MYNN scheme is incorporated into a three-dimensional mesoscale model and is evaluated using various underlying surface observations. Amelioration of the surface turbulent fluxes is confirmed at five observational sites in China over different land-use types. 相似文献
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Bulk formulae for wind stress, sensible and latent heat flux are presented that are suitable for strong mesoscale events such as westerly wind bursts that contribute to the El Niño-Southern Oscillation (ENSO). Their exchange coefficients for heat and momentum have a simple polynomial dependence on wind speed and a linear dependence on air–sea temperature difference. The accuracy of these formulae are validated with respect to air–sea fluxes estimated using the standard algorithm adopted by the Tropical Ocean-Global AtmosphereCoupled-Ocean Atmosphere Response Experiment (TOGA COARE). The comparison ismade for observations from 96 Tropical Atmosphere Ocean (TAO) array and National Oceanographic Data Center (NODC) moorings in the equatorial and North Pacific Ocean spanning years 1990–1999. The bulk formulae are shown to have very small median root–mean-square differences with respect to the TOGA COARE estimates: 0.003 N m-2, 1.0 W m-2, and 10.0 W m-2 for the wind stress, sensible heat flux, and latent heat flux, respectively.The variability of air–sea fluxes during the 1997–1998 ENSO is also examined, along with a possible relationship between air–sea fluxes and surface ocean mixed layer depth (MLD). The wind stress and latent heat flux during the 1997 El Niño are found to be greater in the warm pool of the western Pacific than in the central Pacific where the ENSO is most clearly seen. These differences disappear upon the start of La Niña. The MLD in the equatorial Pacific is found to be moderately correlated to air–sea fluxes just before the start of the 1998 La Niña and poorly correlated otherwise. 相似文献
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Wind speed variations are influenced by both natural climate and human activities. It is important to understand the spatial and temporal distributions of wind speed and to analyze the cause of its changes. In this study, data from 26 meteorological stations in the Jing–Jin–Ji region of North China from 1961 to 2017 are analyzed by using the Mann–Kendall(MK) test. Over the study period, wind speed first decreased by-0.028 m s-1 yr-1(p 0.01) in1961–1991, and then increased by 0.002 m s1-yr1-(p 0.05) in 1992–2017. Wind speed was the highest in spring(2.98 m s-1), followed by winter, summer, and autumn. The largest wind speed changes for 1961–1991 and1992–2017 occurred in winter(-0.0392 and 0.0065 m s-1 yr1-, respectively); these values represented 36% and 58%of the annual wind speed changes. More than 90.4% of the wind speed was concentrated in the range of 1–5 m s-1,according to the variation in the number of days with wind speed of different grades. Specifically, the decrease in wind speed in 1961–1991 was due to the decrease in days with wind speed of 3–5 m s-1, while the increase in wind speed in 1992–2017 was mainly due to the increase in days with wind speed of 2–4 m s-1. In terms of driving factors,variations in wind speed were closely correlated with temperature and atmospheric pressure, whereas elevation and underlying surface also influenced these changes. 相似文献
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M. M. Farinha Z. Šlejkovec J. T. van Elteren H. Th. Wolterbeek M. C. Freitas 《Journal of Atmospheric Chemistry》2004,49(1-3):343-353
A three-step sequential extraction procedure with Milli-Q, CaCl2 and H3PO4 was applied for extraction of arsenic species in lichen transplants and airborne particulate matter (fine and coarse fractions). The samples used in this work were collected in 1994–1995 near coal-fired power plants. Both transplant lichens and airborne particulate matter were submitted to the same environment simultaneously. Arsenic species identification and quantification was performed by HPLC–UV–HG–AFS. Inorganic forms of arsenic (arsenite and arsenate) were present in significant amounts in most of the samples. Only in lichens also organic forms of arsenic (monomethyl arsonic acid and dimethyl arsinic acid) were identified which may indicate biotransformation of inorganic arsenic. 相似文献
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Summary We analysed long-term temperature trends based on 12 homogenised series of monthly temperature data in Switzerland at elevations
between 316 m.a.s.l. and 2490 m.a.s.l for the 20th century (1901–2000) and for the last thirty years (1975–2004). Comparisons were made between these two periods, with changes
standardised to decadal trends. Our results show mean decadal trends of +0.135 °C during the 20th century and +0.57 °C based on the last three decades only. These trends are more than twice as high as the averaged temperature
trends in the Northern Hemisphere.
Most stations behave quite similarly, indicating that the increasing trends are linked to large-scale rather than local processes.
Seasonal analyses show that the greatest temperature increase in the 1975–2004 period occurred during spring and summer whereas
they were particularly weak in spring during the 20th century. Recent temperature increases are as much related to increases in maximum temperatures as to increases in minimum
temperature, a trend that was not apparent in the 1901–2000 period. The different seasonal warming rates may have important
consequences for vegetation, natural disasters, human health, and energy consumption, amongst others. The strong increase
in summer temperatures helps to explain the accelerated glacier retreat in the Alps since 1980.
Authors’ addresses: Martine Rebetez, WSL Swiss Federal Research Institute, 1015 Lausanne, Switzerland; Michael Reinhard, Laboratory
of Ecological Systems (ECOS), EPFL Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland. 相似文献
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本文基于通用地球系统模式框架,建立了一个非常高分辨率准全球的耦合模式,其分量为涡分辨率海洋模式和高分辨率大气模式。利用这个模式,在现代气候条件下成功进行6年的试验,并根据高分辨率观测和再分析资料评估了试验结果。这个模式能够模拟大尺度大气海洋结构,海表面温度(SST)锋面,海洋涡旋动能,和风的细致结构。据此,仔细研究了海洋中尺度结构引起的海气相互作用特征。通过对比观测,这个模式很好再现了由中尺度结构引起的SST和风应力的正相关。同时,正相关在强海洋锋面和涡旋区域特别明显。在模拟中,风对中尺度扰动引起的SST的响应偏弱,但不同区域响应量值略有不同。伴随着风的响应偏弱,表面感热的响应被低估,而潜热的响应则被高估,高估原因是因为模式的边界层偏干。风对SST中尺度异常响应主要来自动量垂直混合和气压调整的综合作用。本研究对于中尺度海气相互作用的模拟提供了一些新的线索及对模式的改进提供科学依据。 相似文献
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Pak-wai CHAN Wei HAN Betty MAK Xiaohao QIN Yongzhu LIU Ruoying YIN Jincheng WANG 《大气科学进展》2023,40(2):194-200
Forecasting tropical cyclone track and intensity is a great challenge for the meteorological community, and safeguarding the life and property of people living near the coast is an important issue. One major reason for challenging forecasts is the lack of observations over the vast oceans. During tropical cyclone Mulan between 8 and 10 August 2022over the northern part of the South China Sea, the meteorological authority and research institutes of Chinese mainland collaborated with the meteorolo... 相似文献
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Michael J. Newark 《大气与海洋》2013,51(3):343-353
Abstract Other than the ground‐breaking work of McKay and Lowe (1960), little has been known about the incidence of tornadoes and the risk of tornado damage in Canada. Data concerning tornadoes during the period 1950 to 1979 (and earlier) have been gathered from many sources and processed to arrive at a set of quantitative conclusions concerning some of their physical characteristics and climatology. The data indicate that tornado incidence (the number of tornadoes per unit area per unit time) in populated sections of Canada is compatible with the incidence values published for adjacent American States, and that the highest annual probability of tornado damage is in southwestern Ontario (0.05 to 0.1%) followed by southeastern Manitoba (0.05%). In terms of size, the Canadian tornado (regardless of intensity) has median damage dimensions of 6 km in length, 80 m in width, and 1 km2 in area. In southwestern Ontario, the return period of a strong or violent tornado is 5 years, and it is likely to have median damage dimensions of 57 km in length, 790 m in width, and 78 km2 in area. 相似文献
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In this analysis, the weather research and forecasting model coupled with a single-layer urban canopy model is used to simulate the climatic impacts of urbanization in the Beijing–Tianjin–Hebei metropolitan area, which has experienced significant expansion in its urban areas. Two cases examining current landscapes and the sensitivity test of urban areas replaced by cropland have been carried out to explore the changes in the surface air and atmospheric boundary structure. The impact of urbanization on annual mean surface air temperature has been found to be more than 1 °C in urban areas, and the maximum difference is almost 2 °C. The change in near-surface level temperature is most pronounced in winter, but the area influenced by urbanization is slightly larger in summer. The annual mean water vapor mixing ratio and wind speed are both reduced in the urban area. The effect of urbanization can only heat the temperature inside the urban boundary layer, below 850 hPa. The modeling results also indicate that the underlying surface thermal forces induced by the “urban heat island” effect enhance vertical air movement and engenders a convergence zone over urban areas. The convergence at low level together with the moisture increases in the layer between 850 and 700 hPa triggered the increase of convective precipitation. 相似文献
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《Climate Policy》2002,2(1):111-117
This article evaluates the environmental effectiveness and economic efficiency of the Kyoto Protocol after the Bonn Agreement and the Marrakesh Accords. The US withdrawal has by far the greatest impact in reducing the environmental effectiveness, lowering the price of traded emission permits and reducing Annex I abatement costs. The decisions on sinks imply that the Annex I CO2-equivalent emissions without the US will come out at about 1/2% below base-year level, instead of over 4% below base-year level. Without US participation, the emission permit price is estimated to be low. Therefore, banking hot air by Russia and the Ukraine is of absolute importance for the development of a viable emissions trading market, and would also enhance the environmental effectiveness of the Kyoto Protocol. 相似文献
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Thomas Nehrkorn Janusz Eluszkiewicz Steven C. Wofsy John C. Lin Christoph Gerbig Marcos Longo Saulo Freitas 《Meteorology and Atmospheric Physics》2010,107(1-2):51-64
This paper describes the coupling between a mesoscale numerical weather prediction model, the Weather Research and Forecasting (WRF) model, and a Lagrangian Particle Dispersion Model, the Stochastic Time-Inverted Lagrangian Transport (STILT) model. The primary motivation for developing this coupled model has been to reduce transport errors in continental-scale top–down estimates of terrestrial greenhouse gas fluxes. Examples of the model’s application are shown here for backward trajectory computations originating at CO2 measurement sites in North America. Owing to its unique features, including meteorological realism and large support base, good mass conservation properties, and a realistic treatment of convection within STILT, the WRF–STILT model offers an attractive tool for a wide range of applications, including inverse flux estimates, flight planning, satellite validation, emergency response and source attribution, air quality, and planetary exploration. 相似文献
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Time-dependent response of a zonally averaged ocean–atmosphere–sea ice model to Milankovitch forcing
An ocean–atmosphere–sea ice model is developed to explore the time-dependent response of climate to Milankovitch forcing for
the time interval 5–3 Myr BP. The ocean component is a zonally averaged model of the circulation in five basins (Arctic, Atlantic,
Indian, Pacific, and Southern Oceans). The atmospheric component is a one-dimensional (latitudinal) energy balance model,
and the sea-ice component is a thermodynamic model. Two numerical experiments are conducted. The first experiment does not
include sea ice and the Arctic Ocean; the second experiment does. Results from the two experiments are used to investigate
(1) the response of annual mean surface air and ocean temperatures to Milankovitch forcing, and (2) the role of sea ice in
this response. In both experiments, the response of air temperature is dominated by obliquity cycles at most latitudes. On
the other hand, the response of ocean temperature varies with latitude and depth. Deep water formed between 45°N and 65°N
in the Atlantic Ocean mainly responds to precession. In contrast, deep water formed south of 60°S responds to obliquity when
sea ice is not included. Sea ice acts as a time-integrator of summer insolation changes such that annual mean sea-ice conditions
mainly respond to obliquity. Thus, in the presence of sea ice, air temperature changes over the sea ice are amplified, and
temperature changes in deep water of southern origin are suppressed since water below sea ice is kept near the freezing point. 相似文献
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Pan Yongjie Lyu Shihua Li Suosuo Gao Yanhong Meng Xianhong Ao Yinhuan Wang Shujin 《Theoretical and Applied Climatology》2017,127(3-4):1011-1022
Soils containing gravel (particle size ≥2 mm) are widely distributed over the Qinghai–Tibet Plateau (QTP). Soil mixed with gravel has different thermal and hydrological properties compared with fine soil (particle size <2 mm) and thus has marked impacts on soil water and heat transfer. However, the most commonly used land models do not consider the effects of gravel. This paper reports the development of a new scheme that simulates the thermal and hydrological processes in soil containing gravel and its application in the QTP. The new scheme was implemented in version 4 of the Community Land Model, and experiments were conducted for two typical sites in the QTP. The results showed that (1) soil with gravel tends to reduce the water holding capacity and enhance the hydraulic conductivity and drainage; (2) the thermal conductivity increases with soil gravel content, and the response of the temperature of soil mixed with gravel to air temperature change is rapid; (3) the new scheme performs well in simulating the soil temperature and moisture—the mean biases of soil moisture between the simulation and observation reduced by 25–48 %, and the mean biases of soil temperature reduced by 9–25 %. Therefore, this scheme can successfully simulate the thermal and hydrological processes in soil with different levels of gravel content and is potentially applicable in land surface models.
相似文献18.
The results of the analysis of statistical characteristics for wind speed are presented for the lower 2–km atmospheric layer over the Russian Arctic. The calculations are based on radiosonde data for the observation period of 1964–2016. The data passed the procedure of complex control of quality and the procedure of quality control specially developed for the atmospheric layer of 0–2 km. The Akima cubic spline interpolation is used for computing wind speed. The trends are estimated using the classic method. It is shown that the spatiotemporal distribution of the trends is not uniform. Wind speed and its standard deviations in the analyzed layer over the Arctic mainly increase in the layer of 400–800 m above the surface. 相似文献
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Atmospheric Circulation and Dynamic Mechanism for Persistent Haze Events in the Beijing–Tianjin–Hebei Region 总被引：16，自引：0，他引：16
In this study, regional persistent haze events(RPHEs) in the Beijing–Tianjin–Hebei(BTH) region were identified based on the Objective Identification Technique for Regional Extreme Events for the period 1980–2013. The formation mechanisms of the severe RPHEs were investigated with focus on the atmospheric circulation and dynamic mechanisms. Results indicated that:(1) 49 RPHEs occurred during the past 34 years.(2) The severe RPHEs could be categorized into two types according to the large-scale circulation, i.e. the zonal westerly airflow(ZWA) type and the high-pressure ridge(HPR) type. When the ZWA-type RPHEs occurred, the BTH region was controlled by near zonal westerly airflow in the mid–upper troposphere.Southwesterly winds prevailed in the lower troposphere, and near-surface wind speeds were only 1–2 ms~(-1). Warm and humid air originating from the northwestern Pacific was transported into the region, where the relative humidity was 70% to 80%, creating favorable moisture conditions. When the HPR-type RPHEs appeared, northwesterly airflow in the mid–upper troposphere controlled the region. Westerly winds prevailed in the lower troposphere and the moisture conditions were relatively weak.(3) Descending motion in the mid-lower troposphere caused by the above two circulation types provided a crucial dynamic mechanism for the formation of the two types of RPHEs. The descending motion contributed to a reduction in the height of the planetary boundary layer(PBL), which generated an inversion in the lower troposphere. This inversion trapped the abundant pollution and moisture in the lower PBL, leading to high concentrations of pollutants. 相似文献
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