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1.
C. V. Srinivas R. Venkatesan K. M. Somayaji A. Bagavath Singh 《Journal of Earth System Science》2006,115(5):557-574
A simulation study of the sea breeze circulation and thermal internal boundary layer (TIBL) characteristics has been carried
out at the tropical site Kalpakkam on the east coast of India, for operational atmospheric dispersion prediction. The community
based PSU/NCAR MM5 Meso-scale meteorological model is used for the study. Three cases on typical days in summer (24 May 2003),
southwest (SW) monsoon (1 July 2001) winter season (2 February 2003) with different large-scale flow pattern are studied.
The MM5 model is used with 3 nested domains with horizontal grid resolutions 18 km, 6 km and 2 km and 26 vertical levels.
The model is integrated for 24 hours in the above cases with initial and boundary conditions taken from NCEP-FNL analyses
data. Observations of 10 meteorological stations and coastal boundary layer experiments conducted at Kalpakkam are used for
comparison and validation of the simulation. The characteristics of simulated sea breeze and TIBL at Kalpakkam are seen to
vary in the above cases according to the prevailing large-scale winds and surface fluxes. The sea breeze circulation is seen
to develop early with larger strength and inland propagation in the summer case under the influence of moderate synoptic wind
and strong heating conditions than in the SW monsoon and winter cases. The horizontal and vertical extents of TIBL are found
to be larger in the summer case than in other cases. Although model parameters agree in general with observations, all the
fine features are not clearly captured and some slowness in model sea breeze development is also seen. The results indicate
the need to improve i) the initial conditions by assimilation of available surface/upper air observations to reduce model
bias and ii) surface net radiation parameterisation. The model could predict the essential features of the local circulation
and further improvement is expected with better initial condition data and incorporation of more realistic surface data. 相似文献
2.
Matthew Simpson Sethu Raman R. Suresh U. C. Mohanty 《Journal of Earth System Science》2008,117(6):897-909
Doppler radar derived wind speed and direction profiles showed a well developed sea breeze circulation over the Chennai, India
region on 28 June, 2003. Rainfall totals in excess of 100 mm resulted from convection along the sea breeze front. Inland propagation
of the sea breeze front was observed in radar reflectivity imagery. High-resolution MM5 simulations were used to investigate
the influence of Chennai urban land use on sea breeze initiated convection and precipitation. A comparison of observed and
simulated 10m wind speed and direction over Chennai showed that the model was able to simulate the timing and strength of
the sea breeze. Urban effects are shown to increase the near surface air temperature over Chennai by 3.0K during the early
morning hours. The larger surface temperature gradient along the coast due to urban effects increased onshore flow by 4.0m
s−1. Model sensitivity study revealed that precipitation totals were enhanced by 25mm over a large region 150 km west of Chennai
due to urban effects. Deficiency in model physics related to night-time forecasts are addressed. 相似文献
3.
Numerical simulation of sea breeze characteristics observed at tropical coastal site,Kalpakkam 总被引：1，自引：0，他引：1
Sea breeze characteristics around Kalpakkam tropical coastal site are studied using an Advanced Regional Prediction System
(ARPS) mesoscale model, which is non-hydrostatic, compressible atmospheric prediction model following the terrain coordinate
system. Various options such as surface physics, atmospheric radiation physics, Coriolis force, microphysics, cumulus parameterization
and 1.5 level TKE closure scheme for diffusion are included in the model.
A joint meteorological field experiment was carried out by IITM-Pune and IGCAR at Kalpakkam by deploying state-of-the-art
sensors and tether balloon systems for observing the height profiles of meteorological parameters. The data obtained from
the field experiment are used here to compare the results from numerical simulations. From the simulated results, it is seen
that duration of the sea breeze is 6 hours which agrees well with the observations. The height of the Thermal Internal Boundary
Layer (TIBL) is also simulated from the vertical profiles of potential temperature. Simulated wind speed and wind directions
are compared with the 50 m tower data and potential temperature profiles are compared with the kytoon data. Results are in
good agreement with the observed values except during night time wherein a small difference is seen in the wind speed. 相似文献
4.
Heat wave of 2015 over India, a natural disaster with 2500 human deaths, was studied to understand the characteristics, associated atmospheric circulation patterns and to evaluate its predictability. Although temperatures are highest in May over India, occurrence of heat wave conditions over southeast coastal parts of India in May 2015 had been unanticipated. Analyses revealed that isolated region of Andhra Pradesh (AP) had experienced severe heat wave conditions during May 23–27, 2015, with temperatures above 42 °C and the sudden escalation by 7–10 °C within a short span of 2–3 days. Short-range weather predictions with Advanced Research Weather Research and Forecasting model at 3-km resolution, up to 72-h lead time, have been found accurate with statistical metrics of small mean absolute error and root-mean-square error and high index of agreement confirming the predictability of the heat wave evolution. Analyses have indicated that regional atmospheric pressure disparities within the Eurasia region, i.e., increased pressure gradient between the Middle East and India, had been responsible for increased northwest wind flow over to northwest India and to southeast India which have advected higher temperatures. Estimates of warm air advection have shown heat accumulation over AP region, due to sea breeze effect. The study led to the conclusion that changing pressure gradients between Middle East and India, enhancement of northwest wind flow with warm air advection and sea breeze effect along southeast coast blocking the free flow have contributed to the observed heat wave episode over coastal Andhra Pradesh. 相似文献
5.
A two-dimensional numerical model is employed to study the effect of the coastal urban heat island on the sea breeze front
and the thermal internal boundary layer height. The temperature at the land surface is determined by solving an energy budget
equation. The effect of the urban heat island is studied by varying the width of the region and its intensity. During the
early afternoon, the presence of the urban heat island enhances the strength of convergence of the sea breeze front and also
reduces its inland penetration. The presence of the urban heat island causes increased thermal internal boundary layer height.
Larger urban width causes larger vertical velocity and higher thermal internal boundary layer. Stronger convergence and higher
thermal internal boundary layer are also obtained in case of larger heat island intensity. 相似文献
6.
在渤海,中尺度模式预报的风速通常比实际风速低得多.利用1990-2001年渤海不同观测站的风场、温度场资料,按季节、风向对海、陆风速统计分析,得到海陆风速的对比值,同时对造成海陆风速差异的原因进行动力、热力等分析.结果表明:海、陆风速在不同的天气系统以及动力和热力方面都存在明显差异.据此渤海风速场推算模式进行了改进,既考虑动力摩擦的作用,也考虑热力差异引起的海陆风增幅作用,改进的渤海风场推算模式有了很大的提高.因此,应用改进后的渤海风速场推算模式,对中尺度数值预报的风速场进行订正,使预报的风速明显提高,更加接近实际情况. 相似文献
7.
The coastal ocean model FVCOM is applied to quantify the changes in circulation, flushing, and exposure time in Great South Bay, New York, after Superstorm Sandy breached the barrier island in 2012. Since then, the lagoon system is connected to the Atlantic via five instead of four inlets. The model simulations are run on two high-resolution unstructured grids, one for the pre-breach configuration, one including the new inlet, with tidal-only forcing, and summer and winter forcing conditions. Despite its small cross-sectional size, the breach has a relatively large net inflow that leads to a strengthening of the along-bay through-flow in Great South Bay (GSB); the tidally driven volume transport in central GSB quadrupled. The seasonal forcing scenarios show that the southwesterly sea breeze in summer slows down the tidally driven flow, while the forcing conditions in winter are highly variable, and the circulation is dependent on wind direction and offshore sea level. Changes in flushing and exposure time associated with the modified transport patterns are evaluated using a Eulerian passive tracer technique. Results show that the new inlet produced a significant decrease in flushing time (approximately 35% reduction under summer wind conditions and 20% reduction under winter wind conditions). Maps of exposure time reflect the local changes in circulation and flushing. 相似文献
8.
Impact of sea breeze on wind-seas off Goa, west coast of India 总被引：1，自引：0，他引：1
After withdrawal of the Indian Summer Monsoon and until onset of the next monsoon, i.e., roughly during November–May, winds
in the coastal regions of India are dominated by sea breeze. It has an impact on the daily cycle of the sea state near the
coast. The impact is quite significant when large scale winds are weak. During one such event, 1–15 April 1997, a Datawell
directional waverider buoy was deployed in 23 m water depth off Goa, west coast of India. Twenty-minute averaged spectra,
collected once every three hours, show that the spectrum of sea-breeze-related ‘wind-seas’ peaked at 0.23 ±0.05 Hz. These
wind-seas were well separated from swells of frequencies less than 0.15 Hz. The TMA spectrum (Bouwset al 1985) matched the observed seas spectra very well when the sea-breeze was active and the fetch corresponding to equilibrium
spectrum was found to be 77±43 km during such occasions. We emphasize on the diurnal cycle of sea-breeze-related sea off the
coast of Goa and write an equation for the energy of the seas as a function of the local wind 相似文献
9.
Integral assessment of air pollution dispersion regimes in the main industrialized and urban areas in Oman 总被引：1，自引：1，他引：0
This paper presents a rather complete picture of conditions of stagnation, recirculation and ventilation factors in the main industrialized and urban areas in Oman, developed along the coastal area. This study focuses on four sites; Sohar, Muscat, Sur, and Salalah. Each site has a local emission sources from transportation, industry and energy production activities. For the calculation of the integral quantities of the ability of the atmosphere dilution, hourly data of the wind velocity measured at a height of 10 m during 5 years (2000–2005) were used in the analysis. The results show that in the northern coast of Oman, along the bay of Sea of Oman, where 56% of the total population is concentrated and the main heavy industries of the country are amassed, the atmosphere is prone to stagnations in 74.4% of the time, while in the southern and east part of Oman, they occur only 23% and 51%, respectively. The bay of sea of Oman is high affected by land–sea breeze circulation that plays a substantial role in the simultaneous occurrence of recirculation equally to stagnation. This meso-scale effect is altered gradually during the passage of the synoptic-scale flow of the southeasterly summer monsoon that enhances the occurrence of the ventilation in Salalah (24.6% of time) and Sur (15.5%). In the northern coast of Oman, where the Hajir mountains suppressed the effect of the summer monsoon, a very weak tendency towards ventilation is observed (less than 6%). The southern summer monsoon over Oman is a source of life in this arid area and as well a source of clean air. 相似文献
10.
The characteristics of simulated air flow over Andaman Islands are studied with a two-dimensional version of the University
of Virginia meso scale model (UVMM). Using the observed synoptic data as initial conditions, 24 hr simulations are obtained
for a day each in April and November. These days are chosen to study the variations in the simulated flow pattern under different
synoptic conditions including precipitation effects. A large scale condensation scheme is employed to consider the effect
of latent heat release on the perturbations. The results show that the latent heat released by condensation strengthens the
intensity of perturbations and the topography accelerates the arrival of sea breeze by about an hour. The model-simulated
results, given in graphical form, are discussed and compared with available observations. 相似文献
11.
The objective of this study is to investigate the impact of a surface data assimilation (SDA) technique, together with the
traditional four-dimensional data assimilation (FDDA), on the simulation of a monsoon depression that formed over India during
the field phase of the 1999 Bay of Bengal Monsoon Experiment (BOBMEX). The SDA uses the analyzed surface data to continuously
assimilate the surface layer temperature as well as the water vapor mixing ratio in the mesoscale model. The depression for
the greater part of this study was offshore and since successful application of the SDA would require surface information,
a method of estimating surface temperature and surface humidity using NOAA-TOVS satellites was used. Three sets of numerical
experiments were performed using a coupled mesoscale model. The first set, called CONTROL, uses the NCEP (National Center
for Environmental Prediction) reanalysis for the initial and lateral boundary conditions in the MM5 simulation. The second
and the third sets implemented the SDA of temperature and moisture together with the traditional FDDA scheme available in
the MM5 model. The second set of MM5 simulation implemented the SDA scheme only over the land areas, and the third set extended
the SDA technique over land as well as sea. Both the second and third sets of the MM5 simulation used the NOAA-TOVS and QuikSCAT
satellite and conventional upper air and surface meteorological data to provide an improved analysis. The results of the three
sets of MM5 simulations are compared with one another and with the analysis and the BOBMEX 1999 buoy, ship, and radiosonde
observations. The predicted sea level pressure of both the model runs with assimilation resembles the analysis closely and
also captures the large-scale structure of the monsoon depression well. The central sea level pressures of the depression
for both the model runs with assimilation were 2–4 hPa lower than the CONTROL. The results of both the model runs with assimilation
indicate a larger spatial area as well as increased rainfall amounts over the coastal regions after landfall compared with
the CONTROL. The impact of FDDA and SDA, the latter over land, resulted in reduced errors of the following: 1.45 K in temperature,
0.39 m s−1 in wind speed, and 14° in wind direction compared with the BOBMEX buoy observation, and 1.43 m s−1 in wind speed, 43° in wind direction, and 0.75% in relative humidity compared with the CONTROL. The impact of SDA over land
and sea compared with SDA over land only showed a further marginal reduction of errors: 0.23 K in air temperature (BOBMEX
buoy) and 1.33 m s−1 in wind speed simulations. 相似文献
12.
The focus of the present study is the assessment of the impact of wind forcing on the spectral wave model MIKE 21 SW in the Indian Ocean region. Three different wind fields, namely the ECMWF analyzed winds, the ECMWF blended winds, and the NCEP blended winds have been used to drive the model. The wave model results have been compared with in-situ observations and satellite altimeter data. This study also evaluated the performance of the wind products during local phenomenon like sea breeze, since it has a significant impact on the wave prediction in the Indian coastal region. Hence we explored the possibility of studying the impact of diurnal variation of winds on coastal waves using different wind fields. An analysis of the model performance has also been made during high wind conditions with the inference that blended winds generate more realistic wave fields in the high wind conditions and are able to produce the growth and decay of waves more realistically. 相似文献
13.
The development and propagation of a pollution gradient in the marine boundary layer over the Arabian Sea during the Intensive
Field Phase of the Indian Ocean Experiment (1999) is investigated. A hypothesis for the generation of the pollution gradient
is presented. Infrared satellite images show the formation of the pollution gradient as the leading edge of a polluted air
mass in the marine boundary layer and also its propagation over the Arabian Sea and the northern Indian Ocean. Aerosol data
measured from two research vessels over the Arabian Sea show a variation in the concentrations caused by the passage of this
pollution gradient. Depth of the pollution gradient was found to be about 800 m. A numerical model was used to simulate the
development of this gradient and its propagation over the ocean. Results show that its formation and structure are significantly
influenced by the diurnal cycle of coastal sea-land breeze circulations along India’s west coast. Transport of aerosols and
gases over the Arabian Sea in the lower troposphere from land sources appears to be through this mechanism with the other
being the elevated land plume. 相似文献
14.
The Indian subcontinent is characterized by complex topography and heterogeneous land use-land cover. The Himalayas and the Tibetan Plateau are spread across the northern part of the continent. Due to its highly variable topography, understanding of the prevailing synoptic weather systems is complex over the region. The present study analyzes the energetics of Indian winter monsoon (IWM) over the Indian subcontinent using outputs of mesoscale model (MM5) forced with National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), US, initial and boundary conditions. MM5 modeling framework, designed to simulate or predict mesoscale atmospheric circulations, is having a limited-area, non-hydrostatic and terrain following 12 sigma levels. The IWM energetics is studied using MM5 model outputs. Prior to this model’s validity and deviation from the corresponding observations (NCEP/NCAR) is assessed. The model’s overestimation/underestimation of wind, temperature and specific humidity at upper troposphere proves that the model has difficulty in picking up corresponding fields at all the model grid points because of terrain complexity over the Himalayas and Tibetan Plateau. Hence, the model fields deviate from the corresponding observations. However, model results match well with the winter global energy budget calculated using reanalysis dataset by Peixoto and Oort (1992). It suggests MM5 model’s fitness in simulating large scale synoptic weather systems. And, thus the model outputs are used for calculation of energetics associated with IWM. It is observed that beyond \(15^{{\circ }}\hbox {N}\) lower as well as upper level convergence of diabatic heating, which represents continental cooling and sinking of heat from atmosphere to land mass (i.e., surface is cooler than surrounding atmosphere) dominates. The diabatic heating divergence (cooling of continents) is found over ocean/sea and whole of the China region, Tibetan and central Himalayas (because of excess condensation than evaporation). The adiabatic generation of kinetic energy depends on the cross isobaric flow (north to south in winter, i.e., the present study shows strong circulation during IWM). It is found that wind divergence of model concludes lower level convergence over study region (i.e., strong winter circulation in the model fields). 相似文献
15.
S. R. Kalsi 《Journal of Earth System Science》2000,109(2):211-220
BOBMEX-Pilot was organised from 23rd October–11th November, 1998 when the seasonal trough had already shifted to south Bay
of Bengal. The activity during this period was marked by the development of a monsoon depression from 26th–29th October that
weakened over the sea; onset of northeast monsoon along the east coast of India on 29th October; a low pressure area that
formed on 2nd November over southwest Bay off Sri Lanka — southTamilnadu coast; and another cyclonic circulation that formed
towards the end of the BOBMEX-Pilot period. This paper describes the development of these synoptic systems through synoptic
charts and satellite data. 相似文献
16.
We reconstructed the paleoenvironmental history of surface and deep water over the last 130 kyr from oxygen and carbon isotope ratios of planktonic and benthic foraminifera in two cores (MD179-3312 and MD179-3304) from the Joetsu Basin, eastern margin of the Japan Sea. Our data showed that paleoceanographic changes such as influx of surface currents and vertical circulation were associated with global glacial–interglacial sea level change. Surface water conditions were influenced by the influx of Tsushima Current, East China Sea coastal or off-shore waters through the Tsushima Strait during interglacial or interstadial stages, and strongly affected by freshwater input during the glacial maximum. During interglacial maximums such as Marine Isotope Stages 1 and 5e, development of well-oxygenated bottom water was indicated. A density-stratified ocean with weak ventilation was inferred from the isotopic records of benthic foraminifera during the Last Glacial Maximum. Local negative excursions in carbon isotopes during deglacial or interglacial periods may suggest the dissolution of gas hydrates or methane seep activities. 相似文献
17.
A century of land subsidence in Ravenna, Italy 总被引：4，自引：2，他引：4
P. Teatini M. Ferronato G. Gambolati W. Bertoni M. Gonella 《Environmental Geology》2005,47(6):831-846
Over the last century the Ravenna area has been affected by a widespread land subsidence process of both natural and anthropogenic origin which has become a matter of increasingly great concern. Land settlement, initially of the order of a few mm/year, dramatically increased up to 110 mm/year after World War II primarily due to groundwater pumping and, subordinately, gas production from a number of deep on-shore and off-shore reservoirs. Spirit leveling was carried out in the area of the Ravenna Municipality by various authorities and agencies ever since the end of the nineteenth century using an increasingly refined network of benchmarks. The available information, spanning the time interval from 1897 to 2002, has been implemented and homogenized into a Geographic Information System (GIS). Measurements processed by kriging provide the pattern of the subsidence rates over the municipal territory during eight sub-periods. The reliability of data processing is discussed for both magnitude and areal distribution of the occurrence, showing a pronounced nonlinear behavior in time, as related to the major responsible factors. Cumulative land subsidence approaches almost 1 m over more than one third of the municipality area including the city and a significant fraction of the coastland, with peaks larger than 1.5 m over a 10 km2 zone located between the historical center and the coastline. Most recent records show that at present the mainland appears to be substantially stable, whereas some coastal areas are still subsiding at a rate of about 10 mm/year with a significant threat to the environment and the infrastructures as well, although to a lesser extent than in the past decades. 相似文献
18.
The impact of the air pollution generated by any industrial activities may be further aggravated if the location of the industrial area is exposed to certain atmospheric characteristics. Under such conditions, the likelihood of accumulation of local air pollution is high. This paper uses two approaches (statistical and numerical simulation) to investigate the contribution of atmospheric processes towards degradation of air quality. A case study of the two approaches was conducted over Sohar Industrial Area in the Sultanate of Oman. Measured wind data were used to account for specific atmospheric characteristics such as stagnation, ventilation, and recirculation using the statistical approach. In the second approach, numerical weather prediction model was used to simulate mesoscale circulation phenomena such as sea breeze and its contribution to the processes affecting the air quality. The study demonstrates that the atmospheric processes appear to contribute substantially to the degradation of air quality in the Sohar Industrial Area. The statistical analysis shows that the atmospheric dilution potential of Sohar Industrial Area is prone to stagnation and recirculation, rather than ventilation. Moreover, model simulation shows that there is a seasonal variation in the contribution of atmospheric processes to the degradation of the air quality at Sohar Industrial Area. 相似文献
19.
基于19个人工气象站1961—2017年风速风向实测数据对南极冰盖近地面风速时空变化和风向进行了分析。结果表明：近50年来,南极冰盖近地面各季节平均风速和年平均风速变化的空间模式基本一致。东南极0°~120° E沿海地区风速呈显著上升趋势;南极半岛气象站风速变化趋势各异,且变化速率相差甚大,但从区域平均结果来看,南极半岛年和季节平均风速均呈上升趋势。这与近几十来局地气温、气压变化及南半球环状模趋向于正位相发展有关。东南极受下降风和绕极东风影响,大部分地区盛行偏南风或偏东风,且频率较高风向稳定;而受天气活动影响,南极半岛风向复杂,主风向频率低,风向多变。 相似文献
20.
Doppler sodar wind data for the boundary layer over Kharagpur obtained during MONTBLEX-1990 at a height interval of 30 m from
surface up to 1500 m have been analysed for the periods when intense synoptic scale disturbances from north Bay of Bengal
moved along the eastern end of the monsoon trough. The variation in the vertical wind profile in the lower boundary layer
over Kharagpur during the passage of synoptic scale disturbances has been discussed in the paper. The analysis indicates that
the mean winds over Kharagpur veered with height in the lower boundary layer near the surface suggesting divergence over Kharagpur
when the system lay south/southwest of the station. No such veering has been noticed when the centre of the system lay very
close to the station. 相似文献