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1.
利用1997—2015年吉林省春夏期(4—7月)逐日气象站地面观测资料,以气温、气压、相对湿度、水汽压、风速为协变量,建立各站点逐日降水量的基于自组织映射神经网络(Self-Organizing Maps,SOM)的统计预测模型;分析吉林省春夏期的主要天气模态,研究逐日降水和天气模态之间的关系,并基于此关系提出逐日降水量的蒙特卡罗模拟方法。结果表明:SOM对天气模态的分型质量较好,邻近天气模态的累积概率分布较相似,距离较远的天气模态累计概率分布差异较大。各天气模态下无降水的概率与日降水量区间宽度的相关系数为-0. 94,显著性水平小于0. 01。基于降水量累积概率分布,20种天气模态被划分成4类,并与降水易发程度和逐日降水量完全对应。在此基础上,对吉林省24个站点逐日降水量进行蒙特卡罗模拟,并进行预测性能分析。平均绝对误差(Mean Absolute Error,MAE)和均方根误差(Root Mean Square Error,RM SE)的中位数分别为3. 12 mm和6. 13 mm,SBrier和Ssig分别为0. 06和0. 51,站点的逐日降水量预测性能整体较好。MAE和RMSE分布呈现东南大西北小,去除降水自然变异差异的影响,所有站点的误差都较小; SBrier和Ssig没有明显的空间分布特征。 相似文献
2.
Summary Seven synoptic patterns responsible for heavy precipitation in Austria were identified with a trajectory clustering method.
Back trajectories at different levels, at different times during each day, and from different locations in Austria were utilised
together with one potential vorticity value. In addition, seven regions within Austria with similar daily precipitation were
identified. The response of heavy precipitation in each of these regions to the synoptic patterns was studied. The results
correspond to the synoptic experience and reflect known meteorological situations, such as southerly and northerly Stau or
the Vb pattern. The analyses are based on the 15-year re-analysis of the ECMWF (1979–1993), used to calculate the back trajectories,
and daily precipitation sums of 131 climate stations in Austria. This paves the way to future applications in climate change
research, as the necessary input data are also available from global climate models. The clustering was performed with a promising
new procedure, a combination of hierarchical and iterative (K-means) clustering. 相似文献
3.
Summary A methodology developed for automatic classification of Objective Synoptic Processes (OSP) and its application to the study
of the mesoscale atmospheric circulatory patterns associated with them is described. The classification was based on the analysis
of the evolution of surface pressure and geopotencial height at 500 hPa during three days. An iterative procedure results
in an objective grouping of the main configurations describing different large-scale situations. This routine has been applied
over an appropriate domain covering the Iberian Peninsula to obtain OSPs in the region for the two month period July–August,
using daily synoptic maps for years 1990 to 1999 (a total of 7304 surface and 500 hPa synoptic maps have been used in the
analysis). Finally, for a characteristic day for two of the OSPs obtained, a mesoscale meteorological model (TAPM) has been
run at high resolution for the region of Catalonia, Northeastern Spain, in order to describe the local atmospheric circulatory
patterns associated with a given large-scale situation. Results show that the complex orography modifies the large-scale forcings
resulting in wind fields with a very important horizontal variability, significant daily cycle, and specific local features
related to orographic elements, which the model was able to incorporate due to the highly-resolved orography used. 相似文献
4.
P. Kassomenos H. A. Flocas S. Lykoudis M. Petrakis 《Theoretical and Applied Climatology》1998,59(3-4):215-229
Summary In this study day by day synoptic conditions are classified over the Attica peninsula for a period of sixteen years. Eight
synoptic categories which are demonstrated to be statistically distinct are selected with respect to the atmospheric circulation
in the lower troposphere. Furthermore, a methodology is proposed to classify the mesoscale patterns for the same period on
the basis of surface wind measurements, and this distinguishes eleven distinct mesoscale categories. In general, the frequency
analysis reveals that the anticyclonic circulation dominates while the weak mesoscale flows prevail, with preference in May
and June. A day by day cross tabulation of the synoptic flow patterns with the mesoscale categories is then performed in order
to identify the association of the synoptic conditions with the mesoscale flow regime. It was found that the synoptic conditions
at the level of 850 hPa are closely related to the observed surface local flows and therefore it is suggested that the synoptic
categories can be used for the identification of the most favourable mesoscale atmospheric circulation.
Received February 28, 1997 Revised May 22, 1997 相似文献
5.
A one-layer mesoscale model based on the shallow water equations has been developed to examine atmospheric flow patterns within a well mixed planetary boundary layer over the Swiss Middleland. The model incorporates frictional and synoptic forcing effects and has a realistic meso- scale representation of the Alpine and surrounding orography. Some model results are shown for one particular Case Study and also for several situations corresponding to different synoptic scale forcing. 相似文献
6.
Thermal interaction between near-water atmospheric layer and surface water layer is considered within long-term, seasonal, synoptic, and mesoscale variability ranges from long-term air and water temperature measurement data. It is established that long-term mean monthly values of water temperature within annual cycle are greater than corresponding values of air temperature. Equations of relationships are obtained for long-term mean annual, mean seasonal, and mean monthly air and water temperature values. 相似文献
7.
Synoptic classification is a methodology that represents diverse atmospheric variables and allows researchers to relate large-scale atmospheric circulation patterns to regional- and small-scale terrestrial processes. Synoptic classification has often been applied to questions concerning the surface environment. However, full applicability has been under-utilized to date, especially in disciplines such as hydroclimatology, which are intimately linked to atmospheric inputs. This paper aims to (1) outline the development of a daily synoptic calendar for the Mid-Atlantic (USA), (2) define seasonal synoptic patterns occurring in the region, and (3) provide hydroclimatological examples whereby the cascading response of precipitation characteristics, soil moisture, and streamflow are explained by synoptic classification. Together, achievement of these objectives serves as a guide for development and use of a synoptic calendar for hydroclimatological studies. In total 22 unique synoptic types were identified, derived from a combination of 12 types occurring in the winter (DJF), 13 in spring (MAM), 9 in summer (JJA), and 11 in autumn (SON). This includes six low pressure systems, four high pressure systems, one cold front, three north/northwest flow regimes, three south/southwest flow regimes, and five weakly defined regimes. Pairwise comparisons indicated that 84.3 % had significantly different rainfall magnitudes, 86.4 % had different rainfall durations, and 84.7 % had different rainfall intensities. The largest precipitation-producing classifications were not restricted to low pressure systems, but rather to patterns with access to moisture sources from the Atlantic Ocean and easterly (on-shore) winds, which transport moisture inland. These same classifications resulted in comparable rates of soil moisture recharge and streamflow discharge, illustrating the applicability of synoptic classification for a range of hydroclimatological research objectives. 相似文献
8.
Summary Based on the mean daily values of air temperature, air pressure, and precipitation totals at 13 climatological stations within
the territory of the Czech Republic in the period 1961–2002, a statistical analysis of “meteorological singularities” (i.e.,
calendar-dependent deviations from the mean annual variation for selected meteorological elements) was performed. At the 13
stations analysed, a total of 45 meteorological singularities (37 singularities in air temperature, 35 in air pressure, and
30 in precipitation) were found. The singularities detected correlate well with cases traditionally recognised in the Czech
Republic as well as with the results of analyses performed for Germany. Despite the considerable variability of singularities
in time and space, most of them are found across the entire territory of the Czech Republic and can be observed for the most
part in all three elements processed. The majority of the singularities detected may be explained on the basis of circulation
mechanisms, by relating them to a significantly higher occurrence of certain groups of synoptic situations characterised by
anomalous temperature or precipitation effects. Cases of “competition” between singularities, when different singularities
may occur on the same calendar day, were found. 相似文献
9.
M. Burlando 《Theoretical and Applied Climatology》2009,96(1-2):69-83
In 2008, Burlando et al. proposed a two-stage clustering technique for the classification of mesoscale wind regimes. The first stage of this classification scheme is based on a hierarchical cluster analysis, according to Ward’s minimum variance technique applied to an Euclidean distance, for a first-guess subdivision of the events into groups. In the second stage, a partitional k-means clustering for the optimal reassignment of the events among clusters is performed. Following this methodology, in the present paper, the synoptic-scale wind fields over the Mediterranean Sea have been analysed in order to check the suitability of this technique to a higher-dimensional phase space. The study is based on a 30-year-long data set of wind speed and direction at 10 m above sea level obtained from the reanalysis of the European Centre for Medium-range Weather Forecasts. The cluster analysis has been performed on wind speeds only, while wind directions have been used to show the existence, in the spatial structure of the wind climate regimes, of particular regions which correspond to the main topographic and/or thermal forcing of the Mediterranean. These regions are the peaks of the probability density function in the climatological phase space of wind speed patterns recognised by the clustering algorithm. The final classification has been able to identify, for instance, the surface circulation patterns corresponding to Mistral events in the western Mediterranean sub-basin and Etesian winds in the eastern sub-basin. 相似文献
10.
G. A. Efstathiou C. J. Lolis N. M. Zoumakis P. Kassomenos D. Melas 《Theoretical and Applied Climatology》2014,115(1-2):259-279
Raingauge data from four meteorological stations in Chalkidiki peninsula (Greece) were used to identify the characteristics of the synoptic circulation patterns associated with cold-season heavy rainfall events and corresponding flooding over the area. Precipitation climatology over the complex topography of Chalkidiki is characterized by limited annual rainfall, but in the occurrence of heavy rainfall episodes daily accumulations are exceptionally high with increased precipitation rates, leading often to severe flooding. Fifty-five cases of high daily accumulations for the period of 1997 to 2010, mostly observed during December and October, were classified into eight clusters by applying S-Mode Factor Analysis and Cluster Analysis to the ERA-Interim grid point reanalysis data. The results revealed that, in most cases, intense rainfall and flooding is produced by synoptic scale disturbances that generate and sustain cyclonic activity over south Italy, the Ionian, and less frequently over the Aegean Sea. In particular, the atmospheric circulation patterns associated with heavy rainfall are characterized by the presence of a southeasterly–easterly low-level humid flow over Chalkidiki in conjunction with the potentially unstable lower troposphere influenced by mid-level cyclonic vorticity advection and enhanced low-level convergence over the complex terrain. 相似文献
11.
Summary A mesoscale convective system that affected Northeastern Spain on October 10, 1994, with rainfall amounts up to 400 mm, is simulated reasonably well by a nested 3-dimensional hydrostatic mesoscale model. Previous studies carried out in this region had already portrayed the main synoptic patterns that give rise to these devastating episodes. The present contribution takes a further step since it goes down to the mesoscale by means of a numerical model providing a more detailed representation not otherwise achieved by earlier analysis methods. Although the model was unable to forecast accurately the precipitation fields, it captured satisfactorily the framework in which the convective system originated and evolved.With 16 Figures 相似文献
12.
A. K. Guèye Serge Janicot A. Niang S. Sawadogo Benjamin Sultan A. Diongue-Niang S. Thiria 《Climate Dynamics》2012,39(9-10):2251-2272
The aim of this work is to define over the period 1979–2002 the main synoptic weather regimes relevant for understanding the daily variability of rainfall during the summer monsoon season over Senegal. “Interannual” synoptic weather regimes are defined by removing the influence of the mean 1979–2002 seasonal cycle. This is different from Part I where the seasonal evolution of each year was removed, then removing also the contribution of interannual variability. As in Part I, the self-organizing maps approach, a clustering methodology based on non-linear artificial neural network, is combined with a hierarchical ascendant classification to compute these regimes. Nine weather regimes are identified using the mean sea level pressure and 850?hPa wind field as variables. The composite circulation patterns of all these nine weather regimes are very consistent with the associated anomaly patterns of precipitable water, mid-troposphere vertical velocity and rainfall. They are also consistent with the distribution of rainfall extremes. These regimes have been then gathered into different groups. A first group of four regimes is included in an inner circuit and is characterized by a modulation of the semi-permanent trough located along the western coast of West Africa and an opposite modulation on the east. This circuit is important because it associates the two wettest and highly persistent weather regimes over Senegal with the driest and the most persistent one. One derivation of this circuit is highlighted, including the two driest regimes and the most persistent one, what can provide important dry sequences occurrence. An exit of this circuit is characterised by a filling of the Saharan heat low. An entry into the main circuit includes a southward location of the Saharan heat low followed by its deepening. The last weather regime is isolated from the other ones and it has no significant impact on Senegal. It is present in June and September, and missing in July and August, meaning that this is a weather regime more specific of the intermediate seasons than the summer. It is included in a large-scale pattern covering the northern latitudes of Europe. The correspondence between these “interannual” synoptic weather regimes and the “pure” synoptic regimes defined in Part I has been established. By selecting a high statistical significance level for these correspondences, each of five out of nine “interannual” weather regimes has a close correspondence with one “pure” synoptic weather regime, one out of them have links with two “pure” regimes, and the last three regimes have no significant correspondence in terms of “pure” regimes. However when considering more moderate links, two out of these three regimes show a connection with a “pure” regime, and the last one remains isolated. The ensemble of the weather regimes occurrences can explain a significant part of interannual variability of summer rainfall amount over Senegal, especially linked to the driest and the wettest weather regimes occurrences. It is also shown that Senegal rainfall state is very sensitive to a small displacement or deformation of the weather regime patterns. 相似文献
13.
A. K. Gu��ye Serge Janicot A. Niang S. Sawadogo Benjamin Sultan A. Diongue-Niang S. Thiria 《Climate Dynamics》2011,36(1-2):1-18
The aim of this work is to define over the period 1979?C2002 the main synoptic weather regimes relevant for understanding the daily variability of rainfall during the summer monsoon season over Senegal. ??Pure?? synoptic weather regimes are defined by removing the influence of seasonal and interannual time scales, in order to highlight the day by day variability of the atmospheric circulation. The Self-Organizing Maps (SOM) approach, a clustering methodology based on non-linear artificial neural network, is combined with a Hierarchical Ascendant Classification to compute these regimes. Nine weather regimes are identified using the mean sea level pressure and 850?hPa wind field as variables, and gathered into three classes. Two of these weather regimes represent the classical 3?C5-day African easterly waves with a mean wavelength of about 3,000?km. Three others are characterized by a modulation of the semi-permanent trough located along the western coast of West Africa and might be interpreted in terms of the 6?C9-day easterly waves. The last four weather regimes are characterized by a more or less strong north?Csouth dipole of circulation. They can be interpreted as a northward/southward displacement of the Saharan Heat Low for two of them, and a filling/deepening of this depression for the other two. The circulation patterns of all these nine weather regimes are very consistent with the associated anomaly patterns of precipitable water, mid-troposphere vertical velocity, outgoing longwave radiation, and finally rainfall. Rainfall distribution is also highlighted over the southwestern area of Senegal. 相似文献
14.
15.
A numerical mesoscale model has been applied to make a preliminary evaluation of the mesoscale climatic changes due to a deliberate flooding of the Qattara depression in Egypt. Simulation of a typical summer synoptic situation has indicated noticeable effects on the horizontal and vertical wind fields, and for the temperature and moisture patterns. 相似文献
16.
Summary The temporal and spatial precipitation regime of Iran was analysed using multivariate analyses of monthly mean precipitation
records for 71 stations. A Principal Component Analysis was applied to the correlation matrix in order to describe the intra-annual
variations of precipitation. The Principal Component scores were mapped to visualize the spatial structure of the three derived
precipitation regimes. By applying an agglomerative clustering (WARD) of the three Principal Component scores, five homogeneous
spatial clusters, representing five precipitation regions, were developed. The intra-annual types of precipitation distribution,
shown by the five clusters, are described and discussed.
Received November 24, 1997 Revised July 17, 1998 相似文献
17.
C. Michailidou P. Maheras A. Arseni-Papadimititriou F. Kolyva-Machera C. Anagnostopoulou 《Theoretical and Applied Climatology》2009,97(1-2):163-177
This paper presents a method for grouping weather types that occur over an area, which combines meteorological parameters, reflecting air mass characteristics at the surface, with synoptic conditions prevailing over an area. Five quantitative meteorological parameters are used in the procedure: temperature, precipitation, relative humidity, wind velocity and sunshine duration. In addition, two qualitative variables related to the prevailing circulation type and whether it is cyclonic or anticyclonic are also included. The study period is 43 years (1958–2000) and is restricted to the cold and wet sub-period of the year, December–March. Weather types are defined using a relatively new method of cluster analysis, two-step cluster analysis, which allows the simultaneous use of both quantitative and qualitative variables. The aim of the present study is to distinguish primary weather patterns so that the investigation into the relationship between weather patterns and circulation types will be more effective. For Athens, six weather types are created, whereas for Thessaloniki five are produced. For both stations, only two weather types are related to anticyclonic situations. The majority of the identified weather types correspond to a distinctive and well-defined synoptic situation. Each weather type differs from the others, not only in terms of the circulation conditions referring to it, but also with reference to meteorological variables such as temperature and precipitation. The results of the evaluation of the aforementioned procedure are considered to be highly satisfactory. 相似文献
18.
Trajectories of surface cyclones and anticyclones were constructed using an automated scheme by tracking local minima and maxima of mean daily sea level pressure data in the NCEP-NCAR reanalysis and the Centre National de Recherches Météorologiques coupled global climate Model (CNRM-CM3) SRES A2 integration. Mid-latitude lows and highs traveling in the North Pacific were tracked and daily frequencies were gridded. Transient activity in the CNRM-CM3 historical simulation (1950–1999) was validated against reanalysis. The GCM correctly reproduces winter trajectories as well as mean geographical distributions of cyclones and anticyclones over the North Pacific in spite of a general under-estimation of cyclones’ frequency. On inter-annual time scales, frequencies of cyclones and anticyclones vary in accordance with the Aleutian Low (AL) strength. When the AL is stronger (weaker), cyclones are more (less) numerous over the central and eastern North Pacific, while anticyclones are significantly less (more) numerous over this region. The action of transient cyclones and anticyclones over the central and eastern North Pacific determines seasonal climate over the West Coast of North America, and specifically, winter weather over California. Relationships between winter cyclone/anticyclone behavior and daily precipitation/cold temperature extremes over Western North America (the West) were examined and yielded two simple indices summarizing North Pacific transient activity relevant to regional climates. These indices are strongly related to the observed inter-annual variability of daily precipitation and cold temperature extremes over the West as well as to large scale seasonally averaged near surface climate conditions (e.g., air temperature at 2 m and wind at 10 m). In fact, they represent the synoptic links that accomplish the teleconnections. Comparison of patterns derived from NCEP-NCAR and CNRM-CM3 revealed that the model reproduces links between cyclone/anticyclone frequencies over the Northeastern Pacific and extra-tropical climate conditions but is deficient in relation to tropical climate variability. The connections between these synoptic indices and Western weather are well reproduced by the model. Under advanced global warming conditions, that is, the last half of the century, the model predicts a significant reduction of cyclonic transients throughout the mid-latitude North Pacific with the exception of the far northern and northeastern domains. Anticyclonic transients respond somewhat more regionally but consistently to strong greenhouse forcing, with notably fewer anticyclones over the Okhotsk/Kamchatka sector and generally more anticyclones in the Northeastern Pacific. These modifications of synoptic weather result in regional feedbacks, that is, regional synoptic alterations of the anthropogenic warming signal around the North Pacific. In the eastern Pacific, for example, synoptic feedbacks, having to do especially with the northward shift of the eastern Pacific storm-track (responding, in turn, to a weaker equator-to-pole temperature gradient), are favorable to more anticyclonic conditions off the American mid-latitude west coast and more cyclonic conditions at higher latitudes. These circulation feedbacks further reduce the equator-to-pole temperature gradient by favoring high-latitude mean winter warming especially over a broad wedge of the Arctic north of the Bering Sea and moderating the warming along the mid-latitude west coast of north America while also reducing precipitation frequencies from California to Northern Mexico. 相似文献
19.
Anthropogenic aerosols (AA) have significantly caused anomalous winter mean atmospheric circulation over the Northern Hemisphere, but the main daily patterns of winter large-scale circulation change are not well understood. Here a self-organizing map analysis is applied to identify the leading patterns in AA-induced winter daily geopotential height (Z) anomaly fields simulated by three atmospheric general circulation models, with a focus on fast adjustments. Two winter daily circulation response patterns with a synoptic time scale are found: one pattern shows concurring Z anomalies over North America and North Asia with the same sign and the Bering Sea seeing the opposite, resembling the Asia–Bering–North American teleconnection; while the other is the Arctic Oscillation-like pattern with similar Z anomalies over North Pacific and North Atlantic and the opposite over the Arctic region. The AA-induced anomalous precipitation over the tropics and anomalous synoptic eddy activities over the extratropical oceans concur to support and maintain these circulation anomaly patterns. The winter-mean climate responses to AA can be understood as a result of these daily anomaly patterns, especially over the higher latitudes. Specifically, the associated changes in surface air temperature (SAT) over the mid-high latitudes are caused by the AA-driven meridional movements of polar (cold and dry) airmass and midlatitude (warm and moist) airmass in the regions, mainly through the relevant surface downward longwave radiation. This study highlights the role of AA in altering daily weather patterns, which is not sufficiently captured by seasonal mean responses. 相似文献
20.
Summary A set of mesoscale numerical simulations using the Emanuel and Kain-Fritsch deep convection schemes has been performed in order to determine the sensitivity of the forecast-especially, the rainfall-to the scheme used. The study is carried out for two cases of heavy precipitation in the coastal zone of the Western Mediterranean, where the topographic forcing is of primary influence. The first one, characterized by an almost stationary synoptic situation, is dominated by warm, moist advection at low levels; the second one, of frontal type, presents a much stronger dynamic forcing at upper levels. Although the comparison attempt is conditioned by the limited number of considered cases, the numerical results provide at least some preliminary conclusions. The inclusion of a convective scheme improves the forecast precipitation, through two actions: directly, producing more realistic rainfall patterns in areas of convection; indirectly, avoiding excessive precipitation in areas with orographic or dynamical upward forcing by drying and stabilizing the atmosphere upstream. In particular, the Kain-Fritsch scheme seems to be more sensitive to the orographic forcing, in agreement with observations.With 21 Figures 相似文献