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1.
Wavelet analysis is used to study the interannual and interdecadal variations of rainfall in China and atmospheric circulation factors, including the key atmospheric oscillations, W, C, E patterns and subtropical high. Regression analysis and correlation analysis are both used to study the relationship of atmospheric circulation factors and China rainfall on different time scale and spatial scale. The results are as follows: (1) The variations of atmospheric circulation and rainfall in China are characterized by interannual and interdecadal scales. The variations of atmospheric circulation and rainfall are composed of interannual and interdecadal variations. It is necessary to separate those two time scales when climate changes and forecast are studied. (2) The variations of China rainfall are due to the interaction of multi-factors rather than single factors. The marked factors which influence the interannual and interdecadal variations are various. Subtropical high is one of the marked factors which influence interannual variations of rainfall, while AO, NAO, and NPO are one of the marked factors which influence interdecadal variations of rainfall. (3) The longer the time scale is, and the larger the spatial scale is, and the more remarkable the relationships between atmospheric circulation and rainfall are.  相似文献   

2.
This article reviews the advances in severe convection research and operation in China during the past several decades.The favorable synoptic situations for severe convective weather(SCW),the major organization modes of severe convective storms(SCSs),the favorable environmental conditions and characteristics of weather radar echoes and satellite images of SCW and SCSs,and the forecasting and nowcasting techniques of SCW,are emphasized.As a whole,Chinese scientists have achieved a profound understanding of the synoptic patterns,organization,and evolution characteristics of SCW from radar and satellite observations,and the mechanisms of different types of convective weather in China.Specifically,in-depth understanding of the multiple types of convection triggers,along with the environmental conditions,structures and organization modes,and maintenance mechanisms of supercell storms and squall lines,has been obtained.The organization modes and climatological distributions of mesoscale convective systems and different types of SCW,and the multiscale characteristics and formation mechanisms of large hail,tornadoes,downbursts,and damaging convective wind gusts based on radar,satellite,and lightning observations,as well as the related features from damage surveys,are elucidated.In terms of operational applications,different types of identification and mesoanalysis techniques,and various forecasting and nowcasting techniques using methods such as the"ingredients-based"and deep learning algorithms,have been developed.As a result,the performance of operational SCW forecasts in China has been significantly improved.  相似文献   

3.
Through simulation of summer and winter precipitation cases in China, the cloud precipitation schemes of model were examined. Results indicate that it is discrepant between convective precipitation simulated by the Kain-Fritsch (KF) scheme and Betts-Miller (BM) scheme in summer, the former scheme is better than the latter in this case. The ambient atmosphere may be varied by different convective schemes. The air is wetter and the updraft is stronger in the KF scheme than in the BM scheme, which can induce the more grid scale precipitation in the KF scheme, i.e., the different cumulus schemes may have the different and important effect on the grid scale precipitation. However, there is almost no convective rain in winter in northern China, so the effect of cumulus precipitation on the grid scale precipitation can be disregarded. Therefore, the gird scale precipitation is primary in the winter of northern China.  相似文献   

4.
A review is presented about the development and application of climate ocean models and oceanatmosphere coupled models developed in China as well as a review of climate variability and climate change studies performed with these models. While the history of model development is briefly reviewed, emphasis has been put on the achievements made in the last five years. Advances in model development are described along with a summary on scientific issues addressed by using these models. The focus of the review is the climate ocean models and the associated coupled models, including both global and regional models, developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences. The progress of either coupled model development made by other institutions or climate modeling using internationally developed models also is reviewed.  相似文献   

5.
Daily and monthly total precipitation of 155 synoptic stations with relatively regular distribution over Iran, covering the 1990–2014 period, were used to investigate the spatial pattern of precipitation seasonality and regimes over Iran, using a set of precipitation seasonality indices. The results suggest a strong agreement between the indices computed at monthly time scale. The result also shows a latitudinal decreasing gradient from the lower index values in the north to the highest values in the south of Iran, suggesting a strong negative relationship between the latitude and the indices. A weak but statistically significant association was also found between the indices and the longitude, showing a gradual west-east contrast between the mountainous western Iran and the central-eastern lowlands and deserts of the country. The spatial patterns of the indices well agree in revealing different precipitation regimes in Iran, in spite of the observed discrepancies in their areal extent of the regions identified. All the indices characterized northern Iran by a precipitation regime having a moderate seasonality, while the mountainous areas of the western and northern Iran are featured by a marked precipitation regime possessing a longer dry season. However, the most seasonal precipitation regime with the longest dry period describes the southern country and some spot areas of the central-eastern Iran. The spatial distribution of the seasonal precipitation regimes and the month and season of maximum precipitation amounts across Iran was also identified, suggesting that from the 24 possible precipitation regimes over the globe, eight were found in Iran, from which a precipitation regime with the highest precipitation amount in winter, followed by autumn, spring, and summer characterized most parts of the country. January and JFM were also found as the month and season of maximum precipitation in a majority of stations distributed over Iran, respectively. The precipitation concentration index (DPCI) computed using daily precipitation data ranges between 0.56 and 0.76 across the country; nonetheless, the values between 0.64 and 0.70 characterized a majority of stations distributed over most parts of Iran. Contrarily to the indices computed at monthly time scale, the DPCI does not show a clear latitudinal pattern over the country. The Mann–Kendal trend test and the Sen slope estimator were applied to the computed indices relative to 16 stations with the longest and complete precipitation records during 1951–2014 time period. The indices time series showed no significant trend in the majority of the stations, indicating that the precipitation regimes of the studied stations did not change over 1951–2014 period.  相似文献   

6.
The United Nations Environment Programme (UNEP) performed field surveys at 15 sites in Bosnia–Herzegovina where depleted uranium (DU) ammunition was used by the North Atlantic Treaty Organization (NATO) during the Balkans conflict (1994–1995). During the field missions, the Italian Environmental Protection Agency (APAT) evaluated airborne contamination due to DU dusts or aerosol particles, generated at the time of the conflict by the impact of DU ammunition on hard targets, using lichens and tree barks as biomonitors. Each sample was analyzed by alpha-spectrometry for DU determination. The 234U/238U activity concentration ratios were used to distinguish natural from anthropogenic uranium. This paper reports the data obtained by the UNEP investigation, including (non-radioactive) metal and other element concentrations in lichen and tree bark samples measured by instrumental neutron activation analysis (INAA). The results indicated: (i) lichens and tree barks are sensitive bio-accumulators of past airborne contamination by depleted uranium dusts; (ii) 8 years after the conflict, environmental DU contamination is still present at some of the target sites; and (iii) the highest concentrations of most non-radioactive elements were found at sites used for ammunition destruction.  相似文献   

7.
In this paper, Indian monsoon of 1980 and 1981 is analysed based on the seasonal and half-month averaged data of 850 hPa of ECMWF analysis. The results show that Indian monsoon is related to Somali jet, the low-latitude easterlies and the mid-latitude westerlies over southern Indian Ocean, which are associated with the stationary wave of Southern Hemisphere. The forces affecting on the low-level flow are diagnosed, which display the relationship between Indian monsoon and the associated low-level flow.  相似文献   

8.
1 Physical and Chemical Structural Characteristics of Urban ABLObtained preliminarily the atmospheric dynamic structure of the urban ABL: Urban heat island and urban wind, the zero-plane displacement and roughness of urban building blocks, the distribution and dynamic and thermal impacts of urban fog. In the aspect of city-scale simulation research, the effect of the topography around the outskirts of Beijing on the urban wind field and the effect of buildings on the urban atmospheric circulation are studied. The possible influencing mechanisms of the U-shaped mountains to the west and north of Beijing on the daily variation of the urban wind field, and the formation, transport and cumulation of urban pollutants are analyzed and some distribution charts are obtained.  相似文献   

9.
From joint wavelet analysis of long-wavelength baroclinic Rossby waves and SST anomalies in the 5–10?yr band in the North and tropical Atlantic, and Reduced Rainfall Height (RRH) in Western Europe and Eastern North America, some key mechanisms involved in the interannual rainfall variability are highlighted. Systematic work has been undertaken to highlight the resonance of long planetary waves in the tropical oceans. Quasi-stationary Waves (QSWs) are produced resulting from the combination of gravitational forces and trade wind stress or ENSO events to compensate for energy lost in the resonator and, above all, to produce a strong modulated output current at the open end, contributing to the western boundary currents. Gravitational forces are resulting from the topography of the surface of the ocean at the antinodes, the dimension of the basin and the wavelength of planetary waves involved in the resonance being of the same order of magnitude. Remote resonances occur at critical latitudes, nearly 40°N and 40°S, forming QSWs the role of which is crucial in the functioning of sub-tropical gyres. In the North Atlantic subtropical gyre, an 8-yr period QSW appears to have a decisive role in the interannual rainfall variability. The pattern of SST anomalies depends on buoyancy of the advected layer associated with this QSW, which is controlled by the amplitude and the phase of long-period sub-harmonics. Rainfall oscillation in Western Europe has occurred for some decades and extended as the dipole formed by SST anomalies on both antinodes became unbalanced, due to the emergence of the advected layer further north. Since then cyclonic or anticyclonic conditions are prevailing at midlatitudes, depending on the polarity. Strengthening of RRH anomalies in Eastern North America is attributed to the buoyancy of the advected layer that re-circulates along the sub-tropical gyre, which evidences the excitation of long-period sub-harmonics, too. Frequency of exceptional events increased in areas heavily exposed to RRH anomalies, subject to oceanic influences even during extreme events, as this occurs in the north of France. Changes in rainfall patterns is attributed to global warming, i.e. the resonance of long-period sub-harmonics associated with solar magnetic cycles whose amplitude has increased drastically at the end of the second millennium, not including the possible contribution of greenhouse gas emissions whose impact on climate is non-resonant.  相似文献   

10.
Dust sediments collected from 1995 to 1998 in Beijing, Dunhuang, Inner Mongolia, Kashi, the Kunlun Mountains, Lanzhou, Ningxia, the Taklimakan Desert, and Xi‘an, China, were characterized in terms of their physical, chemical, and mineralogical properties. Most aerosols and dust analysed ranged in texture from silty clay to clay loam. Their median particle diameters (Mds) generally ranged between 5 to 63μm,coinciding with those of loess from central China and the finest sand from northwestern China. The dust sediments were characterized by a predominance of SiO2 and Al2O3, followed by K2O. Their SiO2/Al2O3and K2O/SiO2 molar ratios ranged from 5.17 to 8.43 and from 0.009 to 0.0368, respectively. The mass concentration spectrum during a dust storm showed a single peak, rather than the triple peak generally observed under clear sky conditions. The dominant minerals were chlorite, illite, calcite, and dolomite.These physical, chemical, and mineralogical properties were consistent with those of aeolian soils and loess in western and central China. The results suggest that aerosols and fine-gained fractions of dust sediments collected in northern China are mainly composed of soil material transported from the arid and semiarid regions of China and Mongolia by prevailing winds. The rate of deposition and properties of dust falling on eastern China were strongly influenced by meteorological conditions, season, latitude, longitude, and altitude of the sampling sites.  相似文献   

11.
In this paper the differences between Meiyu and Baiu front in 1983 have firstly been analysed, the trajectories of air on and to the north side of Meiyu and Baiu fronts during the Meiyu period have then been traced, and the forecasting and simulating of 4 sets of Meiyu onset of the year have finally been run utilizing the global model at UK Me-leorological Office. The results show: 1) Meiyu fronts are different from Baiu ones in temperature, humidity and stratification fields in lower atmosphere; and the possibly reasons for it are explained. 2) The Bay of Bengal is the main moisture source for Meiyu front, the South China Sea and the Pacific, for Baiu ones; and some existed arguments on it are also discussed. 3) The onset of Meiyu and its rainfall and rain belts are sensitive to the Tibetan Plateau, and the water vapour conditions over the Bay of Bengal and the South China Sea, but not sensitive to the SST over the equatorial area or to the East of Japan.  相似文献   

12.
In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a meridional overturning wave-like pattern extending to midlatitudes.Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning circulation along the subtropical jet stream, exhibiting the east–west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the Hadley cell, the Bonin high anomaly ultimately triggers a meridional overturning, establishing the Pacific–Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly meridionally oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.  相似文献   

13.
China has been experiencing widespread air pollution due to rapid industrialization and urbanization in recent decades.The two major concerns of ambient air quality in China are particulate matter(PM) and tropospheric ozone(O_3). With the implementation of air pollution prevention and control actions in the last five years, the PM pollution in China has been substantially reduced. In contrast, under the conditions of the urban air pollution complex, the elevated O_3 levels in city clusters of eastern China, especially in warm seasons, have drawn increasing attention. Emissions of air pollutants and their precursors not only contribute to regional air quality, but also alter climate. Climate change in turn can change chemical processes, long-range transport, and local meteorology that influence air pollution. Compared to PM, less is known about O_3 pollution and its climate effects over China. Here, we present a review of the main findings from the literature over the period 2011–18 with regard to the characteristics of O_3 concentrations in China and the mechanisms that drive its interannual to decadal variations, aiming to identify robust conclusions that may guide decision-making for emissions control and to highlight critical knowledge gaps. We also review regional and global modeling studies that have investigated the impacts of tropospheric O_3 on climate, as well as the projections of future tropospheric O_3 owing to climate and/or emission changes.  相似文献   

14.
Errors and Correction of Precipitation Measurements in China   总被引：2，自引：0，他引：2  
In order to discover the range of various errors in Chinese precipitation measurements and seek a correction method, 30 precipitation evaluation stations were set up countrywide before 1993. All the stations are reference stations in China. To seek a correction method for wind-induced error, a precipitation correction instrument called the ＂horizontal precipitation gauge＂ was devised beforehand. Field intercomparison observations regarding 29,000 precipitation events have been conducted using one pit gauge, two elevated operational gauges and one horizontal gauge at the above 30 stations. The range of precipitation measurement errors in China is obtained by analysis of intercomparison measurement results. The distribution of random errors and systematic errors in precipitation measurements are studied in this paper. A correction method, especially for wind-induced errors, is developed. The results prove that a correlation of power function exists between the precipitation amount caught by the horizontal gauge and the absolute difference of observations implemented by the operational gauge and pit gauge. The correlation coefficient is 0.99. For operational observations, precipitation correction can be carried out only by parallel observation with a horizontal precipitation gauge. The precipitation accuracy after correction approaches that of the pit gauge. The correction method developed is simple and feasible.  相似文献   

15.
Extreme weather events and their consequential impacts have been a key feature of the climate in recent years in many parts of the world, with many partly attributed to ongoing global-scale warming. The past year, 2022, has been no exception,with further records being broken. The year was marked by unprecedented heatwaves and droughts with highly unusual spatial extent, duration and intensity, with one measure indicating an aggregated and overall intensity of extreme heat events worldwide not se...  相似文献   

16.
In this study numerical simulations and water tank experiments were used to investigate the flow and pollutant dispersion in an urban street canyon. Two types of canyon geometry were tested. The studies indicate that in a step-up notch canyon （higher buildings on the downstream side of the canyon）, the height and shape of the upstream lower buildings plays an important role in flow pattern and pollutant dispersion, while in a step-down notch canyon （lower buildings on the downstream side）, the downstream lower buildings have little influence. The studies also show that the substitution of tall towers for parailelepiped buildings on one side of the canyon may enhance the street ventilation and decrease the pollutant concentration emitted by motor vehicles.  相似文献   

17.
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18.
Many studies have shown evidence for significant changes in surface climate in different regions of the world and during different seasons over the past 100 years. Based on daily temperature and precipitation data from 720 climate stations in China, cluster analysis was used to identify regions in China that have experienced similar changes in the seasonal cycle of temperature and precipitation during the 1971-2000 climate normal period. Differences in 11-day averages of daily mean temperature and total precipitation between the first （1971-1985） and second （1986-2000） halves of the record were analyzed using the Mann- Whitney U test and the global κ-means clustering algorithm. Results show that most parts of China experienced significant increases in temperature between the two periods, especially in winter, although some of this warming may be attributable to the urban heat island effect in large cities. Most of western China experienced more precipitation in 1986-2000, while precipitation decreased in the Yellow River valley. Changes in the summer monsoon were also evident, with decreases in precipitation during the onset and decay phases, and increases during the wettest period.  相似文献   

19.
Recent trends in seasonal cycles in China are analyzed, based on a homogenized dataset of daily temperatures at 541 stations during the period 1960–2008. Several indices are defined for describing the key features of a seasonal cycle, including local winter/summer (LW/LS) periods and local spring/autumn phase (LSP/LAP). The Ensemble Empirical Mode Decomposition method is applied to determine the indices for each year. The LW period was found to have shortened by 2–6 d (10 yr)-1, mainly due to an earlier end to winter conditions, with the LW mean temperature having increased by 0.2°C–0.4°C (10 yr)?1, over almost all of China. Records of the most severe climate extremes changed less than more typical winter conditions did. The LS period was found to have lengthened by 2–4 d (10 yr)?1, due to progressively earlier onsets and delayed end dates of the locally defined hot period. The LS mean temperature increased by 0.1°C–0.2°C (10 yr)-1 in most of China, except for a region in southern China centered on the mid-lower reaches of the Yangtze River. In contrast to the winter cases, the warming trend in summer was more prominent in the most extreme records than in those of more typical summer conditions. The LSP was found to have advanced significantly by about 2 d (10 yr)-1 in most of China. Changes in the autumn phase were less prominent. Relatively rapid changes happened in the 1980s for most of the regional mean indices dealing with winter and in the 1990s for those dealing with summer.  相似文献   

20.
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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