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1.
Sensitivity of physical parameterizations on prediction of tropical cyclone Nargis over the Bay of Bengal using WRF model 总被引：3，自引：1，他引：2
P. V. S. Raju Jayaraman Potty U. C. Mohanty 《Meteorology and Atmospheric Physics》2011,113(3-4):125-137
Comprehensive sensitivity analyses on physical parameterization schemes of Weather Research Forecast (WRF-ARW core) model have been carried out for the prediction of track and intensity of tropical cyclones by taking the example of cyclone Nargis, which formed over the Bay of Bengal and hit Myanmar on 02 May 2008, causing widespread damages in terms of human and economic losses. The model performances are also evaluated with different initial conditions of 12?h intervals starting from the cyclogenesis to the near landfall time. The initial and boundary conditions for all the model simulations are drawn from the global operational analysis and forecast products of National Center for Environmental Prediction (NCEP-GFS) available for the public at 1° lon/lat resolution. The results of the sensitivity analyses indicate that a combination of non-local parabolic type exchange coefficient PBL scheme of Yonsei University (YSU), deep and shallow convection scheme with mass flux approach for cumulus parameterization (Kain-Fritsch), and NCEP operational cloud microphysics scheme with diagnostic mixed phase processes (Ferrier), predicts better track and intensity as compared against the Joint Typhoon Warning Center (JTWC) estimates. Further, the final choice of the physical parameterization schemes selected from the above sensitivity experiments is used for model integration with different initial conditions. The results reveal that the cyclone track, intensity and time of landfall are well simulated by the model with an average intensity error of about 8?hPa, maximum wind error of 12?m?s?1and track error of 77?km. The simulations also show that the landfall time error and intensity error are decreasing with delayed initial condition, suggesting that the model forecast is more dependable when the cyclone approaches the coast. The distribution and intensity of rainfall are also well simulated by the model and comparable with the TRMM estimates. 相似文献
2.
Kunde Yang Yuanliang Ma Chao Sun Miller J.H. Potty G.R. 《Oceanic Engineering, IEEE Journal of》2004,29(4):964-972
This paper discusses the results of geoacoustic inversion carried out using explosive charge data from the Asian Seas International Acoustic Experiment (ASIAEX) East China Sea (ECS) Experiment. A multifrequency incoherent matched-field inversion processor and a genetic algorithm (GA) are used for the inversion. A multistep matched field inversion approach is presented, which makes use of the varying sensitivities of wave fields at various frequencies to reduce the inversion problem into a sequence of smaller inversions with fewer unknowns to estimate at each stage. Different parameters are estimated using data at different frequencies according to their sensitivities. Inversion results for different areas in the ECS region are summarized and compared with core data. 相似文献
3.
Abhijit Chatterjee Achutan Jayaraman T. Narayana Rao Sibaji Raha 《Journal of Atmospheric Chemistry》2010,66(1-2):27-40
The temporal variation in concentrations of major water soluble ionic species has been studied from several rain events occurred over Gadanki (13.5 °N, 79.2 °E), located in tropical semi arid region in southern India. The contribution from rain-out (in cloud) and wash-out (below cloud) processes to the total removal of ionic species by rain events is also estimated using the pattern of variations of ionic species within an individual event. A number of rain samples were collected from each rain event during June–November in 2006, 2007 and 2008. On average, nearly 20% of the total NH 4 + and non-sea SO 4 2? is removed by in-cloud scavenging, suggesting that their removal by “below cloud” washout is relatively dominant. In contrast Na+, Ca2+, Mg2+, NO 3 ? and sea-SO 4 2? are mainly removed by below-cloud scavenging or wash-out process. A significant variation in the acidity was observed within rain events with successive precipitation showing higher acidity at the final stage of the precipitation due to partial neutralization of non-sea SO 4 2? . Overall, greater influence of both terrestrial and anthropogenic sources is recorded in the rain events compared to that from marine sources. 相似文献
4.
The present study is carried out to examine the performance of a regional atmospheric model in forecasting tropical cyclones
over the Bay of Bengal and its sensitivity to horizontal resolution. Two cyclones, which formed over the Bay of Bengal during
the years 1995 and 1997, are simulated using a regional weather prediction model with two horizontal resolutions of 165 km
and 55 km. The model is found to perform reasonably well towards simulation of the storms. The structure, intensity and track
of the cyclones are found to be better simulated by finer resolution of the model as compared to the coarse resolution. Rainfall
amount and its distribution are also found to be sensitive to the model horizontal resolution. Other important fields, viz.,
vertical velocity, horizontal divergence and horizontal moisture flux are also found to be sensitive to model horizontal resolution
and are better simulated by the model with finer horizontal grids. 相似文献
5.
Stable nitrogen isotope ratios were used to study the incorporation of anthropogenically-derived nitrogen into the food webs of salt marsh systems along a contamination gradient in Narragansett Bay. Nitrogen isotope ratios (delta(15)N) were measured in six estuarine species collected from three marshes along this gradient, monthly from June to October between 1997 and 1999. A significant decrease in delta(15)N was found with distance along the estuary for four of the six species. Significant differences were found among monthly isotope ratios for some species. Nitrogen isotope ratios in sea lettuce (Ulva lactuca) increased during the summer season with highest delta(15)N values measured during September and October. This trend was most pronounced at the station receiving the highest nutrient inputs. Elevated delta(15)N values at this station appeared to correlate with seawater ammonia/nitrate concentration ratios. The temporal variations in delta(15)N suggest that care should be taken in species selection and the design of sampling schemes of studies using delta(15)N for monitoring anthropogenic nutrients in aquatic systems. Sampling programs designed to determine long-term trends should consider species that do not show rapid fluctuations in isotope ratios. The mud snail, Nassarius obsoletus, responded this way in the present study. Studies designed to measure short-term changes should include species such as U. lactuca, which rapidly respond to isotope changes. The results from this study also help to establish a baseline for nitrogen isotope values in Narragansett Bay. This information can be used to monitor future trends in nitrogen inputs to this estuary. 相似文献
6.
Rocket-borne ultraviolet photometers operating at =0.31 m have been used at Thumba (8°33N, 76°52E) to make measurements of atmospheric scattering at tropospheric and lower stratospheric altitudes. Measurements could be made of the amplitude of the scattered fluxes and the angular distribution up to an altitude of about 24 km on three rocket flights conducted as part of the 16 February 1980 solar eclipse campaign. These measurements have been used to study the size distribution as well as the number densities of aerosols in the troposphere and lower stratosphere over Thumba. 相似文献
7.
Ulrike?WackerEmail author K.?V.?Jayaraman?Potty Christof?Lüpkes J?rg?Hartmann Matthias?Raschendorfer 《Boundary-Layer Meteorology》2005,117(2):301-336
The mesoscale weather prediction model ’Lokal-Modell’ (LM) of the Deutscher Wetterdienst is applied to the situation of an
Arctic cold air outbreak in the Fram Strait region in April 1998. Observations are available from a flight along 50E carried out during the ARTIST campaign. Initial and time-dependent boundary data for the simulation are taken from a larger
scale operational model system.
Using the standard configuration of LM, the simulation reproduced the propagation of cold air and the characteristic structure
of the atmospheric boundary layer (ABL) in fair agreement with the observations. However, a detailed comparison revealed three
basic problems. Firstly, there is evidence that the available data on sea-ice conditions were insufficient approximations
to the true state for several reasons. A modification of the sea-ice data towards observations revealed that parts of the
discrepancies were due to the original sea-ice data. Secondly, a control run with the model in its standard configuration
shows an insufficient warming of the ABL downstream of the ice edge due to underestimation of surface heat fluxes. A simple
modification of the approach for the scalar roughness length resulted in the strongest benefit, while comparative studies
showed only a slight sensitivity to different types of parametrisation of turbulent mixing or the inclusion of an additional
moist convection parametrisation. Thirdly, in all the simulations the deepening of the convective ABL downstream of the ice
edge is weaker than observed. This may be partly due to the thermal stratification above the ABL in the analysis data, which
is more stable than observed; but it may also be a hint to the fact that processes near the inversion are insufficiently parametrised
in mesoscale models with resolutions as used in LM. The simulated cloud layer in the convective ABL is similar to that observed
with respect to condensate content, a sharply defined cloud top, a diffuse lower bound, and continuous light precipitation. 相似文献
8.
The time evolution of stratospheric aerosol layer formed after a volcanic eruption is studied taking into account the aerosol
microphysical processes of growth, coagulation and sedimentation. Using a simple model we could explain the observed evolution
of the Pinatubo volcanic layer which decayed in about 3 years. The experimental data obtained by Nd:YAG backscatter lidar
over Ahmedabad further supports this finding. The data obtained after the El Chichon volcanic eruption also showed that the
El Chichon aerosol layer decayed in about 3 years time. Thus, though the amount of SO2 injected has been higher, in the case of Pinatubo, about two to three times more than El Chichon, it has resulted in the
production of larger aerosol particles due to faster growth and coagulation processes, and subsequently a faster removal rate,
to give more or less a similar background aerosol amount at the stratosphere in about 3 years time. 相似文献
9.
S. Kumari G. Jayaraman C. Ghosh 《International Journal of Environmental Science and Technology》2013,10(6):1325-1336
Present study deals with the statistical analysis of long-term ground level ozone (O3) trend and the influence of meteorological variables on its variation over Delhi, India. Daily mean and maximum of O3 and meteorological data, obtained from India Meteorological Department, were arranged for the period of 9 years (1998–2006). Based on the preliminary correlation study of all the data with O3, six variables viz. daily maximum temperature, daily average relative humidity, dew point, wind speed, visibility, and total sunshine were selected. Classical additive time series decomposition technique was used to obtain seasonally adjusted long-term trend. To analyze the masking effect of meteorology, adjustment was made using Kolmogorov–Zurbenko filters followed by stepwise regression analysis to the smoothed series of O3 maximum and meteorological variables, which showed that long-term trend was independent of sunshine duration. Results indicate a significant increasing trend with annual increase of 1.13 % for O3 mean and 3 % for O3 maximum. Annual deseasonalized trend for seasonal cycle shows bimodal oscillations. About 43 % of O3 variation was explained by the selected meteorological factors and rest of variation attributed to factors like emission of precursor gases, pollutant transport, policy changes, etc. Among the three tested regression models, performance of Model 2 with variable temperature, wind speed, and visibility was found to be best that resulted in lowering of O3 trend. Large variability (23 %) was explained by the variable visibility depicted that the emission of primary pollutants not only provides the precursor gases but also control the local photochemical reactions. 相似文献
10.
In this study, we describe remarkable intraspecific variation in sensitivity to the broadly distributed pollutants, polychlorinated biphenyls (PCBs), among wild populations of the nonmigratory estuarine Atlantic killifish (Fundulus heteroclitus). Variation among killifish populations was characterized in 28-day laboratory challenges using embryonic and larval life stages and the highly toxic, dioxin-like PCB congener, 3,3′4,4′,5-hexachlorobiphenyl (PCB126). In summarizing results for 24 populations, we show that killifish populations vary over four orders of magnitude in their sensitivity to PCB126 and that this variation is adaptive to the magnitude of contamination at their residence site. The four least-sensitive killifish populations reside in US Atlantic coast urban harbors >100 km apart from one another: New Bedford, MA, Bridgeport, CT, Newark, NJ, and Norfolk, VA, USA. Prior studies examining all but the CT population have shown that these killifish are relatively insensitive to local contaminants, with mixed evidence concerning the heritability of this trait. We show here that tolerance to PCB126 is extreme, with some mechanistic similarities among these four killifish populations. However, these populations do not respond identically to each other, and in at least one population, tolerance appears to degrade over the F1 and F2 generations tested. Complementary ongoing studies using molecular approaches provide opportunity to identify unique and shared mechanisms of tolerance in these independently evolving populations and explore the adaptive benefits and costs of contemporary evolutionary responses in the wild. 相似文献