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1.
The present study examines the dynamics of mid-tropospheric vortex during cyclogenesis and quantifies the importance of such vortex developments in the intensification of tropical cyclone. The genesis of tropical cyclones are investigated based on two most widely accepted theories that explain the mechanism of cyclone formation namely ‘top-down’ and ‘bottom-up’ dynamics. The Weather Research and Forecast model is employed to generate high resolution dataset required for analysis. The development of the mid-level vortex was analyzed with regard to the evolution of potential vorticity (PV), relative vorticity (RV) and vertical wind shear. Two tropical cyclones which include the developing cyclone, Hudhud and the non-developing cyclone, Helen are considered. Further, Hudhud and Helen, is compared to a deep depression formed over Bay of Bengal to highlight the significance of the mid-level vortex in the genesis of a tropical cyclone. Major results obtained are as follows: stronger positive PV anomalies are noticed over upper and lower levels of troposphere near the storm center for Hudhud as compared to Helen and the depression; Constructive interference in upper and lower level positive PV anomaly maxima resulted in the intensification of Hudhud. For Hudhud, the evolution of RV follows ‘top-down’ dynamics, in which the growth starts from the middle troposphere and then progresses downwards. As for Helen, RV growth seems to follow ‘bottom-up’ mechanism initiating growth from the lower troposphere. Though, the growth of RV for the depression initiates from mid-troposphere, rapid dissipation of mid-level vortex destabilizes the system. It is found that the formation mid-level vortex in the genesis phase is significantly important for the intensification of the storm. 相似文献
2.
S D Kotal S K Bhattacharya S K Roy Bhowmik P K Kundu 《Journal of Earth System Science》2014,123(7):1619-1635
The tropical cyclone Viyaru maintained a unique quasi-uniform intensity during its life span. Despite being in contact with sea surface for >120 hr travelling about 2150 km, the cyclonic storm (CS) intensity, once attained, did not intensify further, hitherto not exhibited by any other system over the Bay of Bengal. On the contrary, the cyclone Phailin over the Bay of Bengal intensified into very severe cyclonic storm (VSCS) within about 48 hr from its formation as depression. The system also experienced rapid intensification phase (intensity increased by 30 kts or more during subsequent 24 hours) during its life time and maximum intensity reached up to 115 kts. In this paper, a comparative study is carried out to explore the evolution of the various thermodynamical parameters and possible reasons for such converse features of the two cyclones. Analysis of thermodynamical parameters shows that the development of the lower tropospheric and upper tropospheric potential vorticity (PV) was low and quasi-static during the lifecycle of the cyclone Viyaru. For the cyclone Phailin, there was continuous development of the lower tropospheric and upper tropospheric PV, which attained a very high value during its lifecycle. Also there was poor and fluctuating diabatic heating in the middle and upper troposphere and cooling in the lower troposphere for Viyaru. On the contrary, the diabatic heating was positive from lower to upper troposphere with continuous development and increase up to 6°C in the upper troposphere. The analyses of cross sections of diabatic heating, PV, and the 1000–500 hPa geopotential metre (gpm) thickness contours indicate that the cyclone Viyaru was vertically tilted (westward) and lacked axisymmetry in its structure and converse features (axisymmetric and vertical) that occurred for the cyclone Phailin. In addition, there was a penetration of dry air in the middle troposphere of Viyaru, whereas high moisture existed in the middle troposphere of Phailin. The vertical wind shear (5–10 ms?1) near the core of the storm region between 850 and 200 hPa was favourable for both the systems but was higher in the northern region of the cyclone Viyaru. The divergent development of these thermodynamic features conspired to produce converse characteristic of the two cyclones. 相似文献
3.
Movement of seasonal eddies in the Bay of Bengal (BOB) and its relation with cyclonic heat potential (CHP) and cyclogenesis
points have been investigated in this study using 6 years (2002–2007) of global ocean monthly analysis datasets based on the
Simple Ocean Data Assimilation (SODA) package (SODA v2.0.4) of Carton et al. (2005) and Indian Meteorological Department cyclogenesis points. The region dominated by anticyclonic eddies with CHP greater than
70 × 107 J/m2 as well as good correlations (>0.9) with sea surface height (SSH) and 26°C isothermal depth (D
26) can be a potential region of cyclogenesis. The region dominated by cyclonic eddies with CHP greater than 50 × 107 J/m2 and good correlation (>0.9) with both SSH and D
26 can serve as a potential region of high-level depression. Potential cyclogenesis regions are the southern BOB (5°N–12°N)
for the post-monsoon season and the head of BOB (north of 15°N) during southwest monsoon. Seven potential regions are identified
for the eddy formation for different seasons, which are consistent with the cyclogenesis points. The CHP distributions alone
are able to explain the cyclone tracks for the pre-monsoon and post-monsoon seasons but not for the monsoon season. 相似文献
4.
The genesis potential parameter (GPP) consists of two dynamical variables low-level relative vorticity and vertical wind shear, and two thermodynamic variables middle tropospheric relative humidity and instability are analysed during pre-cyclone watch period over the Bay of Bengal. The pre-cyclone watch period is taken as the period prior to 72-h from the formation of a Depression. The GPP values for 30 tropical disturbances that formed over the Bay of Bengal during the period 2001–2010 are analysed. An independent evaluation of the parameter and possible applications to operational forecasting are presented using data from the year 1998 to 1999. The variables of GPP are calculated using the ECMWF interim reanalysis 1.5° × 1.5° resolution data, averaged within an area of 5° × 5° box on the centre of tropical disturbances and also over the 5° × 5° boxes over the adjacent surrounding areas. The results show that maximum value is observed over the genesis region at 48- and 24-h lead time for both the cases of cyclones and Depressions. The threshold value of GPP is found to be 9.3, 6.3 and 2.7 during pre-cyclone watch period at 24-, 48- and 72-h lead time, respectively. A distinction in GPP values above threshold value for cyclonic and a Depression system is also observed for the cyclogenesis region in 69, 75 and 75 % of cases at 72-, 48- and 24-h lead time, respectively. However, the individual case studies show that the GPP could indicate the genesis of a tropical cyclone with a 2-day lead time. The mean GPP values are 11.8, 8.5 and 3.8 for cyclonic systems and 6.9, 4.2 and 1.6 for Depression systems over an area of a box 5° × 5° on the systems at 24-, 48- and 72-h lead time, respectively, from the stage of Depression. The result of the study is found to be providing probable area of genesis and intensification of a tropical disturbance at a 2 day lead time from the stage Depression. 相似文献
5.
C. V. Srinivas V. Yesubabu K. B. R. R. Hariprasad S. S. V. Ramakrishna B. Venkatraman 《Natural Hazards》2013,65(1):331-357
Real-time predictions for the JAL severe cyclone formed in November 2010 over Bay of Bengal using a high-resolution Weather Research and Forecasting (WRF ARW) mesoscale model are presented. The predictions are evaluated with different initial conditions and assimilation of observations. The model is configured with two-way interactive nested domains and with fine resolution of 9?km for the region covering the Bay of Bengal. Simulations are performed with NCEP GFS 0.5° analysis and forecasts for initial/boundary conditions. To examine the impact of initial conditions on the forecasts, eleven real-time numerical experiments are conducted with model integration starting at 00, 06, 12, 18 UTC 4 Nov, 5?Nov and 00, 06, 12 UTC 6 Nov and all ending at 00 UTC 8 Nov. Results indicated that experiments starting prior to 18 UTC 04 Nov produced faster moving cyclones with higher intensity relative to the IMD estimates. The experiments with initial time at 18 UTC 04 Nov, 00 UTC 05 Nov and with integration length of 78?h and 72?h produced best prediction comparable with IMD estimates of the cyclone track and intensity parameters. To study the impact of observational assimilation on the model predictions FDDA, grid nudging is performed separately using (1) land-based automated weather stations (FDDAAWS), (2) MODIS temperature and humidity profiles (FDDAMODIS), and (3) ASCAT and OCEANSAT wind vectors (FDDAASCAT). These experiments reduced the pre-deepening period of the storm by 12?h and produced an early intensification. While the assimilation of AWS data has shown meagre impact on intensity, the assimilation of scatterometer winds produced an intermittent drop in intensity in the peak stage. The experiments FDDAMODIS and FDDAQSCAT produced minimum error in track and intensity estimates for a 90-h prediction of the storm. 相似文献
6.
A cyclone genesis parameter, termed the genesis potential parameter (GPP), for the Indian Sea is proposed. The parameter is
defined as the product of four variables, namely vorticity at 850 hPa, middle tropospheric relative humidity, middle tropospheric
instability, and the inverse of vertical wind shear. The variables are calculated using the National Centers for Environmental
Prediction (NCEP), USA, reanalysis data, averaged within a circle of 2.5° radius around the centre of cyclonic system. The
parameter is tested with a sample dataset of 35 nondeveloping and developing low-pressure systems that formed over the Indian
Sea during the period 1995–2005. The result shows that there is a distinction between GPP values for nondeveloping and developing
systems in more than 85% cases. The composite GPP value is found to be around three to five times greater for developing systems
than for nondeveloping systems. The analysis of the parameter at early development stage of a cyclonic storm appears to provide
a useful predictive signal for intensification of the system. 相似文献
7.
We use acceleration data from the Observatorio Vulcanologico y Sismologico, Universidad Nacional de Costa Rica (OVSICORI-UNA) and Laboratorio de Ingenieria Sismica, Universidad de Costa Rica (LIS-UCR) seismic network for the relocation and moment-tensor solution of the September 5, 2012, 14:42:03.35 UTC, Nicoya, Costa Rica earthquake (Mw 7.6 GCMT). Using different relocation methods we found a stable earthquake hypocenter, near the original OVSICORI-UNA location in the Nicoya Peninsula, NW Costa Rica at Lat 9.6943°N, Lon 85.5689°W, depth 15.3 km, associated with the subduction of the Cocos plate under Caribbean plate. Acceleration records at OVSICORI-UNA and LIS-UCR stations (94–171 km), at 0.03 < f < 0.06 Hz were used in the waveform inversion for a single-point centroid moment tensor (CMT). Using spatial grid search the centroid position was found at the depth of 30 km, situated at Lat 10.0559°N, Lon 85.4778°W, i.e. of about 41 km NNE from the epicenter. The centroid time is 14:42:18.89 UTC, i.e. 15.54 s later relative to the location-based origin time. The nodal plane (strike 318°, dip 27° and rake 115°) is the fault plane that agrees with the geometry of the subducted slab at Nicoya, NNW Costa Rica. Increasing the maximum studied frequency from 0.06 to 0.15 Hz, the multiple point source inversion model leads to two subevents. The first one was located near the centroid and the second subevent was situated 20 km along strike and 10 km down dip from the first subevent and 6 s later. The uncertainty of the source model was carefully examined using complementary inversion methods, viz the iterative deconvolution and non-negative least squares. 相似文献
8.
The cyclones over Bay of Bengal (BoB) have varied socio-economic impacts and meteorological importance. There are considerable uncertainties in predicting the track and intensity of cyclonic systems in the BoB. The present study examines the cyclogenesis characteristics over the BoB and addresses the regional impacts and their importance in terms of intensification of cyclones. An analysis of cyclone track data from 1971–2013 reveals that the cyclones generated in Andaman Sea (a regional sea of BoB) and propagating through central BoB sustain maximum life time. Furthermore, within the BoB, the cyclones originated from Andaman Sea are the most intensified and characterized by highest cyclogenesis potential index. Interestingly, we have found that higher value of mid-tropospheric relative humidity over Andaman Sea during the cyclone period is enhancing the cyclone’s intensity. Climatologically also the Andaman Sea is dominated by higher values of mid-tropospheric relative humidity compared to other regions of BoB. There is no significant distinction between Andaman Sea and rest of the BoB for other meteorological and oceanic parameters that supports cyclogenesis. Climatologically dominant east–west asymmetry in mid-tropospheric relative humidity is enhancing the intensity of cyclones from Andaman Sea. The results will be helpful in understanding the processes of cyclone intensification and useful in the statistical and dynamical prediction of cyclones. 相似文献
9.
Research efforts focused on assessing the potential for changes in tropical cyclone activity in the greenhouse-warmed climate
have progressed since the IPCC assessment in 1996. Vulnerability to tropical cyclones becoming more pronounced due to the
fastest population growth in tropical coastal regions makes it practically important to explore possible changes in tropical
cyclone activity due to global warming. This paper investigates the tropical cyclone activity over whole globe and also individually
over six different ocean basins. The parameters like storm frequency, storm duration, maximum intensity attained and location
of formation of storm have been examined over the past 30-year period from 1977 to 2006. Of all, the north Atlantic Ocean
shows a significant increasing trend in storm frequency and storm days, especially for intense cyclones. Lifetime of intense
tropical cyclones over south Indian Ocean has been increased. The intense cyclonic activity over north Atlantic, south-west
Pacific, north and south Indian Ocean has been increased in recent 15 years as compared to previous 15 years, whereas in the
east and west-north Pacific it is decreased, instead weak cyclone activity has been increased there. Examination of maximum
intensity shows that cyclones are becoming more and more intense over the south Indian Ocean with the highest rate. The study
of the change in the cyclogenesis events in the recent 15 years shows more increase in the north Atlantic. The Arabian Sea
experiences increase in the cyclogenesis in general, whereas Bay of Bengal witnesses decrease in these events. Shrinking of
cyclogenesis region occurs in the east-north Pacific and south-west Pacific, whereas expansion occurs in west-north Pacific.
The change in cyclogenesis events and their spatial distribution in association with the meteorological parameters like sea
surface temperature (SST), vertical wind shear has been studied for Indian Ocean. The increase in SST and decrease in wind
shear correspond to increase in the cyclogenesis events and vice versa for north Indian Ocean; however, for south Indian Ocean,
it is not one to one. 相似文献
10.
The Todagin Creek landslide is located at 57.61° N 129.98° W in Northwest British Columbia. A seismic station 90 km north
of the landslide recorded the event at 1643 hours coordinated universal time (UTC; 0943 hours Pacific daylight time (PDT))
on October 3, 2006. The signal verifies the discovery and relative time bounds provided by a hunting party in the valley.
The landslide initiated as a translational rock slide on sedimentary rock dipping down slope at 34° and striking parallel
to the valley. The landslide transformed into a debris avalanche and had a total volume estimated at 4 Mm3. An elevation drop of 771 m along a planar length of 1,885 m resulted in a travel angle (fahrb?schung) of 21.3°. The narrowest
part of the landslide through the transport zone is 345 m. The widest part of the divergent toe of the landslide reaches a
width of 1,010 m. Landslide debris impounded a lake of approximately 32 ha and destroyed an additional 67 ha of forest. The
impoundment took 7 to 10 days to fill, with muddied waters observed downstream on October 13. No clear linkage exists with
precipitation and temperature records preceding the landslide, but strong diurnal temperature cycles occurred in the days
prior to the event. The Todagin Creek area appears to have an affinity for large landslides with the deposits of three other
landslides >5 Mm3 observed in the valley. 相似文献
11.
Krishna K. Osuri U. C. Mohanty A. Routray Makarand A. Kulkarni M. Mohapatra 《Natural Hazards》2012,63(3):1337-1359
The convection and planetary boundary layer (PBL) processes play significant role in the genesis and intensification of tropical cyclones (TCs). Several convection and PBL parameterization schemes incorporate these processes in the numerical weather prediction models. Therefore, a systematic intercomparison of performance of parameterization schemes is essential to customize a model. In this context, six combinations of physical parameterization schemes (2 PBL Schemes, YSU and MYJ, and 3 convection schemes, KF, BM, and GD) of WRF-ARW model are employed to obtain the optimum combination for the prediction of TCs over North Indian Ocean. Five cyclones are studied for sensitivity experiments and the out-coming combination is tested on real-time prediction of TCs during 2008. The tracks are also compared with those provided by the operational centers like NCEP, ECMWF, UKMO, NCMRWF, and IMD. It is found that the combination of YSU PBL scheme with KF convection scheme (YKF) provides a better prediction of intensity, track, and rainfall consistently. The average RMSE of intensity (13?hPa in CSLP and 11?m?s?1 in 10-m wind), mean track, and landfall errors is found to be least with YKF combination. The equitable threat score (ETS) of YKF combination is more than 0.2 for the prediction of 24-h accumulated rainfall up to 125?mm. The vertical structural characteristics of cyclone inner core also recommend the YKF combination for Indian seas cyclones. In the real-time prediction of 2008 TCs, the 72-, 48-, and 24-h mean track errors are 172, 129, and 155?km and the mean landfall errors are 125, 73, and 66?km, respectively. Compared with the track of leading operational agencies, the WRF model is competing in 24?h (116?km error) and 72?h (166?km) but superior in 48-h (119?km) track forecast. 相似文献
12.
In this paper, the performance of a high-resolution mesoscale model for the prediction of severe tropical cyclones over the Bay of Bengal during 2007?C2010 (Sidr, Nargis, Aila, and Laila) is discussed. The advanced Weather Research Forecast (WRF) modeling system (ARW core) is used with a combination of Yonsei University PBL schemes, Kain-Fritsch cumulus parameterization, and Ferrier cloud microphysics schemes for the simulations. The initial and boundary conditions for the simulations are derived from global operational analysis and forecast products of the National Center for Environmental Prediction-Global Forecast System (NCEP-GFS) available at 1°lon/lat resolution. The simulation results of the extreme weather parameters such as heavy rainfall, strong wind and track of those four severe cyclones, are critically evaluated and discussed by comparing with the Joint Typhoon Warning Center (JTWC) estimated values. The simulations of the cyclones reveal that the cyclone track, intensity, and time of landfall are reasonably well simulated by the model. The mean track error at the time of landfall of the cyclone is 98?km, in which the minimum error was found to be for the cyclone Nargis (22?km) and maximum error for the cyclone Laila (304?km). The landfall time of all the cyclones is also fairly simulated by the model. The distribution and intensity of rainfall are well simulated by the model as well and were comparable with the TRMM estimates. 相似文献
13.
14.
In this paper, impact of Indian Doppler Weather Radar (DWR) data, i.e., reflectivity (Z), radial velocity (Vr) data individually and in combination has been examined for simulation of mesoscale features of a land-falling
cyclone with Advance Regional Prediction System (ARPS) Model at 9-km horizontal resolution. The radial velocity and reflectivity
observations from DWR station, Chennai (lat. 13.0°N and long. 80.0°E), are assimilated using the ARPS Data Assimilation System
(ADAS) and cloud analysis scheme of the model. The case selected for this study is the Bay of Bengal tropical cyclone NISHA
of 27–28 November 2008. The study shows that the ARPS model with the assimilation of radial wind and reflectivity observations
of DWR, Chennai, could simulate mesoscale characteristics, such as number of cells, spiral rain band structure, location of
the center and strengthening of the lower tropospheric winds associated with the land-falling cyclone NISHA. The evolution
of 850 hPa wind field super-imposed vorticity reveals that the forecast is improved in terms of the magnitude and direction
of lower tropospheric wind, time, and location of cyclone in the experiment when both radial wind and reflectivity observations
are used. With the assimilation of both radial wind and reflectivity observations, model could reproduce the rainfall pattern
in a more realistic way. The results of this study are found to be very promising toward improving the short-range mesoscale
forecasts. 相似文献
15.
《Comptes Rendus Geoscience》2019,351(8):525-539
We examined magma storage conditions and eruptive dynamics for the trachyandesite (~58 wt% SiO2, 9–10 wt% alkalis) of the Pavin monogenetic volcano, a maar-like explosive crater belonging to a small group of youngest volcanoes in the Massif Central. By confronting the natural samples to experimental products, we constrained pre-eruptive conditions around 950–975 °C, 150–200 MPa (~5.5–7.0 km in depth), NNO+1.5, and 4.5–5.5 wt% melt H2O. There is petrological evidence of magma crystallization in the conduit up to shallow levels (~50 MPa; 2 km in depth) before fragmentation into pumice clasts in the last kilometre of ascent. The experiments highlight the role of biotite and of crystallization pressure in defining separate compositional trends of residual liquids, i.e. alkaline (trachytes) versus sub-alkaline (dacite-rhyolite). 相似文献
16.
The roles of vortex initialization and model spin-up in tropical cyclone (TC) prediction using Advanced Research Weather Research and Forecasting (ARW) Model are studied through a case study of NARGIS (2008) cyclone over Bay of Bengal. ARW model is designed to have three two-way interactive nested domains, and a suite of 36 numerical experiments are performed with three values of maximum wind (MW), four of radius of maximum wind (RMW), and three of α and one experiment without vortex initialization. The results indicate that vortex initialization is important toward realistic representation of initial structure and location of cyclone vortex. Model spin-up during the first 18–24 h of model integration lead to faster intensification than of the real atmosphere, thus a weaker initial vortex evolved more realistically. Three experiments from vortex initialization produced MW and RMW nearer to the observations, but none of these produced a good prediction due to unrealistic intensification during model spin-up. A weaker vortex with intensity less than 50 % than observations produced the best forecast in terms of intensity, track, and landfall. The results suggest that slightly larger (~30 %) RMW than observations with α as ?0.5 (for 81 km model resolution) that produces weaker vortex is to be implemented in the design of bogus vortex. This study assesses the merits of TC bogus scheme in ARW model, illustrates the need for vortex initialization, and analyzes the spin-up problem in cold-start model simulations of TC prediction. 相似文献
17.
Continuous measurements of aerosol size distributions in the mid-point diameter range 20.5–500 nm were made from October 2005
to March 2006 at Pune (18°32′N, 73°51′E), India using Scanning Mobility Particle Sizer (SMPS). Volatilities of atmospheric
aerosols were also measured at 40°, 125°, 175°, 300° and 350°C temperatures with Thermodenuder–SMPS coupled system to determine
aerosol volatile fractions. Aerosols in nucleated, CCN and accumulated modes are characterized from the measured percentage
of particles volatized at 40°, 125°, 175°, 300° and 350°C temperatures. Averaged monthly aerosol concentration is at its maximum
in November and gradually decreases to its minimum at the end of March. The diurnal variations of aerosol concentrations gradually
decrease in the night and in early morning hours (0400–0800 hr). However, concentration attains minimum in its variations
in the noon (1400–1600 hr) due to higher ventilation factor (product of mixing height and wind speed). The half an hour averaged
diurnal variation of aerosol number concentration shows about 5 to 10-fold increase despite the ventilation factor at higher
side before 1200 hr. This sudden increase in aerosol concentrations is linked with prevailing conditions for nucleation bursts.
The measurement of volatile fraction of ambient aerosols reveals that there are large number of highly volatile particles
in the Aitken mode in the morning hours and these volatile fractions of aerosols at temperatures <150°C are of ammonium chloride
and ammonium sulfate, acetic and formic acids. 相似文献
18.
During 23–30 September 1997, a rare cyclonic storm has developed close to the Andhra coast, and it has later travelled parallel to coastline northward and finally crossed the land at Chittagong (22°N, 91°E) on 27 September. While translating along the east coast of India, it has produced heavy to very heavy rainfall on the coastal stations causing devastating floods. In this study, we made an attempt to understand the salient causes of this unique cyclone movement. We have analyzed daily fields of wind and relative humidity for 850, 700, 500 hPa and mean daily OLR data to understand the plausible reasons for its movement. The buoy data deployed by National Institute of Ocean Technology, Chennai, Viz. DS5 (15°N, 81°E), DS4 (19°N, 88°E) and SW7 (20°N, 86°E) were analyzed to understand the ocean–atmosphere interaction processes in the west Bay of Bengal during formation of the system. Analysis of OLR over the cyclonic storm region has revealed that the heavy rainfall areas coincide with low OLR (120–180 W m?2). The persistent southward movement of 500 hPa ridge on the eastern wedge of the system along with the steering current at 200 hPa has helped in maintaining the movement of the system parallel to the east coast of India during its life cycle. 相似文献
19.
Track prediction of very severe cyclone ‘Nargis’ using high resolution weather research forecasting (WRF) model 总被引：1，自引：0，他引：1
The recent very severe cyclonic storm (VSCS) ‘Nargis’ over the Bay of Bengal caused widespread destruction over Myanmar after
hitting the coast on 2 May 2008. The real time forecasting of the VSCS ‘Nargis’ was a very difficult task as it did not follow
the normal westerly/northwesterly track. In the present study, a detailed diagnostic analysis of the system ‘Nargis’ is carried
out initially to investigate the features associated with this unusual movement and subsequently the real time forecast of
VSCS ‘Nargis’ using high resolution advanced version weather research forecasting (WRF) model is presented. The advanced research
WRF model was run for 72 h at 27 km and 20 km resolutions with 28, 29, 30 April and 1 May as the initial conditions. The diagnostic
study indicates that the recurvature of the system ‘Nargis’ was mainly associated with:
The real time track forecast using the WRF model run at 27 km and 20 km resolution based on the initial conditions of 28 April
(when the system was only 550 km away from the Indian coast) indicated that the system had a northeasterly forecast track
and was not expected to cross the Indian coast. Similarly, based on 29 April initial condition the system showed east/east-northeasterly
movement towards the Myanmar coast. The east/east-northeasterly movement of the ‘Nargis’ was persisting in the forecast based
on 30 April and 1 May initial conditions with respective landfall errors of 85 km and 50 km with 27 km resolution, which reduces
to 30 km and 40 km respectively with 20 km resolution, however, with a landfall time delay of about 10 h. Improvement of mean
forecast errors at different forecast hours is noticed in WRF model run at higher resolution compared to that run at lower
resolution. Thus, it is very clear that the advanced version WRF model had captured movement of the system reasonably well
almost 3 days in advance. Consistence with the diagnostic analysis the WRF model forecast also indicates southerly/southwesterly
strong steering wind at 200 hPa level and maximum pressure fall to the east of the system. 相似文献
| • | upper level southerly/southwesterly steering wind at 200 hPa level associated with anticyclonic circulation over southeastern sector of the centre of the system |
| • | higher SST (29°C or more) with higher positive anomalies over the region to the northeast of the cyclone centre, and |
| • | large negative 24 h pressure changes and large vorticity maximum to the east of the system. |
20.
Satellite detection of thermal precursors of Yamnotri,Ravar and Dalbandin earthquakes 总被引：2，自引：1，他引：1
Saraf Arun K. Rawat Vineeta Das Josodhir Zia Mohammed Sharma Kanika 《Natural Hazards》2012,61(2):861-872
Prior to the occurrence of an earthquake, the region undergoes intensive physiochemical changes. Such changes trigger degassing
charge generation leading to positive change in the thermal regime and consequently creation of an earthquake preparation
zone. These changes in thermal regime can be detected by the thermal sensors onboard various polar orbiting satellites. Recent
researches have demonstrated that thermal infrared sensors onboard satellites (e.g., NOAA-AVHRR and Terra/Aqua-MODIS) can
detect temporal transient thermal infrared anomalies prior to an earthquake. The paper presents satellite-based thermal observations
associated with Yamnotri (July 22, 2007, India), Ravar (October 14, 2004, Iran) and Dalbandin (January 19, 2011, Pakistan)
earthquakes. In the case of Yamnotri earthquake, the region attained around 5–8°C higher than the normal temperature on July
21, 2007 in the area, just 1 day before the earthquake. Whereas, in the case of Ravar earthquake, the region has shown 5–7°C
higher temperature on October 06, 2004 about 6 days before the occurrence of the main earthquake event. Dalbandin earthquake
showed a maxima on January 17, 2011, just 2 days before the main shock with the raised temperature of around 8–10°C. Another
common observation in all these earthquakes is the disappearance of short-term transient thermal anomaly just before the main
shock. 相似文献