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1.
The surface parameters are being evaluated using a methodology which considers the vertical temperature structure of MONTBLEX
’90. For this 30 metre micrometeorological tower data are utilised. In this process, a concept of isolated layers has been
introduced. The parameters have been evaluated following two successive iterative processes to give a consistent value both
in the flux-profile relation and the related similarity relation.
The heat flux obtained using the present methodology, is then utilised to examine its interplay with the synoptic as well
as mesoscale features. The existence of such an interplay is observed. 相似文献
2.
The multi-institutional experiment MONTBLEX aimed at sensing and studying the atmospheric boundary layer over the monsoon trough region of the northern plains of India during the summer monsoon of 1990. Four core facilities consisting of micro-meteorological towers and state-of-the-art instrumentation were created along the trough axis. This overview emphasizes the key features of project planning, management and execution, and provides detail? of all the experimental observation sites. 相似文献
3.
In this paper, we have attempted a diagnostic study of the turbulence characteristics of the ABL by means of two one-dimensional models. The first model uses a first order non-local closure, based on the Transilient Turbulence Theory, for parameterizing turbulent fluxes. while the second model uses second order local closure for parameterizing these. The models have been applied to conduct case studies using the Kytoon data taken at Kharagpur, during 17th–21st June, 1990, as part of the MONTBLEX programme. Our findings bring out various interesting features regarding the non-local and local turbulent statistics such as kinematic fluxes, turbulence kinetic energy, vertical velocity variance, the contribution of the eddies of various sizes to the fluxes at different level and the mixing lengths. The one-dimensional anisotropy of the turbulent eddies has been revealed by the findings from the transilient model. The vertical variation of the turbulence kinetic energy, as computed directly by the second order model, is found to be strongly correlated with the vertical velocity variance. In particular, for stably stratified boundary layers, identification of two distinct zones of the turbulence kinetic energy and corresponding vertical velocity maxima is possible, which has been interpreted as positive evidence of patchy turbulence in the boundary layer. 相似文献
4.
Convection often produces severe weather which causes a great loss to human lives and properties. Precisely predicting the convection initiation process is crucial but challenging in operational convection nowcasting (0~2 h forecasting). Before the radar-defined CI occurring (e.g., the first occurrence of ≥35 dBZ echoes), observations at high spatial and temporal resolutions from weather radars and geostationary meteorological satellites can reveal precursor information such as the boundary-layer convergence lines and the rapid growth of newborn cumulus clouds. These radar- and satellite-observed precursor information are helpful for evaluating the pre-CI conditions and thus nowcasting the accurate CI timing and location. This paper reviewed the current status of radar- and satellite-based CI research and nowcasting techniques. The milestone works and the following studies in the last four decades were summarized to demonstrate how radar and satellite observations can be related to CI occurrence. The objectives and approaches of the CI research advance as the improvement in the capability of radars and were explained satellites. The research progress aids in the development of various CI nowcasting techniques. This paper introduced three well-established techniques that have been put into operational application, namely, ANC system, SATCAST algorithm, and UWCI algorithm. Some scientific issues with respect to radar- and satellite-based CI research and nowcasting were also presented. 相似文献
5.
Tower platforms, with instrumentation at six levels above the surface to a height of 30 m, were used to record various atmospheric
parameters in the surface layer. Sensors for measuring both mean and fluctuating quantities were used, with the majority of
them indigenously built. Soil temperature sensors up to a depth of 30 cm from the surface were among the variables connected
to the mean data logger. A PC-based data acquisition system built at the Centre for Atmospheric Sciences, IISc, was used to
acquire the data from fast response sensors. This paper reports the various components of a typical MONTBLEX tower observatory
and describes the actual experiments carried out in the surface layer at four sites over the monsoon trough region as a part
of the MONTBLEX programme. It also describes and discusses several checks made on randomly selected tower data sets acquired
during the experiment. Checks made include visual inspection of time traces from various sensors, comparative plots of sensors
measuring the same variable, wind and temperature profile plots, calculation of roughness lengths, statistical and stability
parameters, diurnal variation of stability parameters, and plots of probability density and energy spectrum for the different
sensors. Results from these checks are found to be very encouraging and reveal the potential for further detailed analysis
to understand more about surface layer characteristics. 相似文献
6.
江西省地质灾害-气象预警预报系统研究 总被引：4，自引：1，他引：3
论文采用了降雨特征（用降雨诱发指数表征）与地质环境条件（以地质灾害敏感性指数表征）进行叠加、分析,确定预警预报等级,建立地质灾害-预警预报模型的方法;提出了预警产品制作与发布、多普勒雷达跟踪、应急指导、反馈信息收集、灾情调查的地质灾害气象预警预报工作程序。对近几年江西省地质灾害-预警预报效果分析,总结了地质灾害-预警预报成功与失败的经验教训,提出今后的工作设想与建议。应用基于GIS的地质灾害预警预报系统已在近几年的地质灾害-气象预警预报中不断完善,预警预报精度得到提高,防灾减灾效果明显,对保护人民生命财产安全发挥了重要作用。 相似文献
7.
Micro-meteorological tower observations of MONTBLEX (Monsoon Trough Boundary Layer Experiment)-1990, combined with routine
surface observations at Jodhpur in the dry convective sector of Indian summer monsoon trough are used to examine the interrelationship
between total cloud cover (TCC) and surface sensible heat flux (SHF) during the summer monsoon of 1990. A significant inverse
relationship between TCC and SHF is found during various Intensive Observation Periods of the experiment. This relationship
holds for the various methods of estimation of SHF. 相似文献
8.
9.
A co-ordinated project Monsoon Trough Boundary Layer Experiment (MONTBLEX) to study the atmospheric boundary layer in the
monsoon trough region was taken up during 1990. 30-m high instrumented towers were erected at Kharagpur, Banaras, Delhi and
Jodhpur. Sophisticated equipment like Doppler sodar and Kytoon were used at Kharagpur. Sodars were exposed at Calcutta, Delhi
and Jodhpur. ORVSagarkanya cruises were arranged in the Bay of Bengal. The India Meteorological Department set up new surface and radiation observatories
and released special radio-sonde, pilot balloons. Using the above mentioned platforms, data were collected during April -
September 1990 and after proper editing the entire data were archived at the Indian Institute of Tropical Meteorology, Pune.
The DST-MONTBLEX data bank was started at IITM on 25th November 1991. The paper contains the details of this data. 相似文献
10.
The stochastic dynamic method of weather prediction (SDP) has been suggested recently for better understanding of the numerical weather prediction. The SDP is described using a simple one-dimensional advection equation. The salient features of the method, its scope and limitations, are discussed. 相似文献
11.
12.
Characteristic wavelengths for theu andv components of wind are studied using the Monsoon Trough Boundary Layer Experiment (MONTBLEX) data obtained from a Doppler
Sonic Detection and Ranging System (sodar) over the land station Kharagpur (near sea-coast). The principal stability parameter
(Z
i/Lo) is used to infer the behaviour of the non-dimensional form of the characteristic wavelength (L
H) within the entire stability range occurring during the sounding periods. This is compared with GATE - 1974 results (over
the sea surface) published by Fitzjarrald (1978). 相似文献
13.
S. K. Roy Bhowmik 《Journal of Earth System Science》2003,112(4):499-519
At the India Meteorological Department (IMD), New Delhi, a 12-level limited area model with 100 km horizontal resolution has
been in use for weather forecasting. The present study uses this model together with a higher horizontal resolution (50 km)
and vertical resolution (16-levels) model to examine the impact of increased resolution to simulate mesoscale features of
rainfall during monsoon disturbances. The model was run for 22 days in the month of August 1997 and one week in September
1997 during three monsoon depressions and one cyclonic storm in the Bay of Bengal. The model results are compared with observations.
The study shows that the model can capture mesoscale convective organization associated with monsoon depression. 相似文献
14.
南京市强降水天气长期动态及变异性规律 总被引：1，自引：0，他引：1
基于南京市1951～2016年汛期(6～9月)各月降水资料,分析研究区强降水天气的长期动态及变异性规律。长期动态结果表明,近66年来南京市强降水天气发生频率显著增加,平均每10年增加0.31次;不同规模强降水中,暴雨、大暴雨天气发生频率均呈增加趋势,其中暴雨天气呈显著增加。多年(7a、10a、15a)月际排序值滑动标准差均通过置信度99%显著性检验,强降水天气变异性呈显著下降趋势;强降水天气汛期盛行月份趋于集中(7月),月间格局趋于稳定,与多年的月际排序值滑动标准差得出强降水天气变异性呈下降趋势的结论相吻合。 相似文献
15.
新疆40a来气温、降水和沙尘天气变化 总被引：67，自引：10，他引：57
根据1961-2001年新疆代表北疆的8个气象站、天山山区的8个气象站、南疆的8个气象站的实测资料, 分析了40 a来新疆气温、降水、沙尘暴、扬沙、浮尘年代际变化特征.结果显示: 40 a来新疆气温呈明显上升趋势, 后10 a(1991-2000年)比前30 a平均气温升高, 北疆偏高0.8℃, 南疆和天山山区均偏高0.℃; 降水变化的总趋势是增湿明显, 后10 a与前30 a相比降水增加, 南疆偏多20.4%, 北疆偏多11.3%, 天山山区偏多9.8%; 南疆与北疆各类沙尘天气年际变化趋势基本相似, 80年代以来呈减少趋势; 南疆沙尘暴、扬沙、浮尘总日数之和与同期的温度、降水在春季有相对较好的线性相关关系. 相似文献
16.
Progress in Researches on Ensemble Forecasting of Extreme Weather Based on Numerical Models 总被引：1，自引：1，他引：0
Under the background of climate change, extreme weather events (e.g., heavy rainfall, heat wave, and cold damage) in China have been occurring more frequently with an increasing trend of induced meteorological disasters. Therefore, it is of great importance to carry out research on forecasting of extreme weather. This paper systematically reviewed the primary methodology of extreme weather forecast, current status in development of ensemble weather forecasting based on numerical models and their applications to forecast of extreme weather, as well as progress in approaches for correcting ensemble probabilistic forecast. Nowadays, the forecasting of extreme weather has been generally dominated by methodology using dynamical models. That is to say, the dynamical forecasting methods based on ensemble probabilistic forecast information have become prevailing in current operational extreme weather forecast worldwide. It can be clearly found that the current major directions of research and development in this field are the application of ensemble forecasts based on numerical models to forecasting of extreme weather, and its improvement through bias correction of ensemble probabilistic forecast. Based on a relatively comprehensive review in this paper, some suggestions with respect to development of extreme weather forecast in future were further given in terms of the issues of how to propose effective approaches on improving level of identification and forecasting of extreme events. 相似文献
17.
Data obtained from the 30m high MONTBLEX tower installed at the Indian Institute of Technology, Kharagpur are described. Data
on wind speed and direction, temperature and humidity were recorded during the first week of July 1989 at six levels on the
tower. They indicate some of the atmospheric surface layer characteristics. Using two levels of tower data involving wind
speed and temperature a profile method was used for computing the surface fluxes of heat and momentum. A method for calculating
the surface roughness length using the data was also used to obtain the vertical windspeed profile. The computed wind profile
was compared with observations, while the surface roughness length was compared with values obtained by a least square fit.
The computed surface fluxes were compared with theoretical values obtained by an energy budget method which uses only wind
data at one level. The agreement was reasonably good. 相似文献
18.
日地空间环境是人类生存发展的重要场所,太阳剧烈活动引起日地空间短时间尺度的变化,对人类社会带来严重影响和危害。本文简要介绍了空间天气学产生的背景和迅速发展的社会需求,当今国际合作研究的重大计划和进展,以及空间天气学研究的未来和展望。 相似文献
19.
《翁心存日记》是迄今为止发现的记录天气现象最为详细的历史天气日记,保留了难得的19世纪中叶北京的沙尘天气记录。归纳了对历史文献记录中的沙尘天气进行分类的方法,通过《翁心存日记》,重建了19世纪中叶北京沙尘天气情况。分析发现当时北京年平均沙尘日多达31.36天,高于近60年来北京沙尘天气的平均水平。而19世纪中叶的北京沙尘天气中扬沙、浮尘和沙尘暴天气的构成和现代基本相似,年内分布特征也较相似。但19世纪中叶夏季沙尘比例较现代明显偏多46％,而冬季沙尘比例仅为现代比例的75％,这说明古今间沙尘天气的季节分布可能存在较大差异。另外,19世纪的沙尘天气同样存在明显的年际变化,且本地降水是影响年际变化的因素之一。 相似文献
20.
Identifying environmental impacts of underground construction 总被引：2，自引：0，他引：2
Dewatering of the groundwater resource and associated reduced flow of surface water features are potential negative impacts when constructing underground facilities. Little work has been done to develop methods for the early detection of environmental impacts on water resources where major underground construction is being undertaken. Recognizing this, prior to construction of two rock tunnels in the southwestern USA, a 3-year preconstruction program was implemented to monitor over 100 wells, springs, and streams in the project area that might be affected. This preconstruction monitoring phase has established data for a hydrologic reference which indicates a high degree of spatial and temporal variability. This variability must be accounted for when trying to identify construction-related impacts. The project area was subdivided into areas of similar characteristics based on geologic and hydrologic features. Measurements from features within each unit were then normalized and aggregated to derive a single representative flow parameter. This representative flow was then correlated to precipitation and major stream flow records to allow for a method of estimating unimpacted flow and groundwater levels during and after construction. Application of this method proved useful in determining and enabling a quick response to construction-related impacts. 相似文献