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1.
Prakki Satyamurty Claudia Priscila Wanzeler da Costa Antonio Ocimar Manzi 《Theoretical and Applied Climatology》2013,111(1-2):195-209
The regions where the divergence of vertically integrated water vapor flux, averaged over a season or a year, is positive (negative) are sources (sinks) of moisture for the atmosphere. An aerial river is defined as a stream of strong water vapor flux connecting a source and a sink. Moisture flux, its divergence, and sources and sinks over the tropics of South and Central America and the adjoining Atlantic Ocean are obtained for dry years and for wet years in the Amazon Basin. Results show that the Amazon Basin is a sink region for atmospheric moisture in all seasons and that there are two source regions for the moisture in the basin, one situated in the South Atlantic and the other in the North Atlantic, both located equator-ward of the respective subtropical high-pressure centers. The convergence of moisture increases over the Amazon Basin in austral summer, and at the same time it decreases in the Pacific and Atlantic ITCZs. Box model calculations reveal that the wet years, on the average, present about 55 % more moisture convergence than the dry years in the Amazon Basin. A reduction in the moisture inflow across the eastern and northern boundaries of the basin (at 45°W and at the Equator, respectively) and an increase in the outflow across the southern boundary (at 15°S) lead to dry conditions. The annual mean contribution of moisture convergence to the precipitation over the Amazon Basin is estimated to be 70 %. In the dry years, it lowers to around 50 %. The net convergence of water vapor flux over the basin is a good indicator of the wet or dry condition. 相似文献
2.
Prakki Satyamurty Aline Anderson de Castro Julio Tota Lucia Eliane da Silva Gularte Antonio Ocimar Manzi 《Theoretical and Applied Climatology》2010,99(1-2):139-148
Rainfall series at 18 stations along the major rivers of the Brazilian Amazon Basin, having data since 1920s or 1930s, are analyzed to verify if there are appreciable long-term trends. Annual, rainy-season, and dry-season rainfalls are individually analyzed for each station and for the region as a whole. Some stations showed positive trends and some negative trends. The trends in the annual rainfall are significant at only six stations, five of which reporting increasing trends (Barcelos, Belem, Manaus, Rio Branco, and Soure stations) and just one (Itaituba station) reporting decreasing trend. The climatological values of rainfall before and after 1970 show significant differences at six stations (Barcelos, Belem, Benjamin Constant, Iaurete, Itaituba, and Soure). The region as a whole shows an insignificant and weak downward trend; therefore, we cannot affirm that the rainfall in the Brazilian Amazon basin is experiencing a significant change, except at a few individual stations. Subregions with upward and downward trends are interspersed in space from the far eastern Amazon to western Amazon. Most of the seasonal trends follow the annual trends, thus, indicating a certain consistency in the datasets and analysis. 相似文献
3.
Prantik Mandal R. K. Chadha N. Kumar I. P. Raju C. Satyamurty 《Pure and Applied Geophysics》2007,164(10):1963-1983
During the last six years, National Geophysical Research Institute, Hyderabad has established a semi-permanent seismological
network of 5–8 broadband seismographs and 10–20 accelerographs in the Kachchh seismic zone, Gujarat with a prime objective
to monitor the continued aftershock activity of the 2001 Mw 7.7 Bhuj mainshock. The reliable and accurate broadband data for the 8 October Mw 7.6 2005 Kashmir earthquake and its aftershocks from this network as well as Hyderabad Geoscope station enabled us to estimate
the group velocity dispersion characteristics and one-dimensional regional shear velocity structure of the Peninsular India.
Firstly, we measure Rayleigh-and Love-wave group velocity dispersion curves in the period range of 8 to 35 sec and invert
these curves to estimate the crustal and upper mantle structure below the western part of Peninsular India. Our best model
suggests a two-layered crust: The upper crust is 13.8 km thick with a shear velocity (Vs) of 3.2 km/s; the corresponding values
for the lower crust are 24.9 km and 3.7 km/sec. The shear velocity for the upper mantle is found to be 4.65 km/sec. Based
on this structure, we perform a moment tensor (MT) inversion of the bandpass (0.05–0.02 Hz) filtered seismograms of the Kashmir
earthquake. The best fit is obtained for a source located at a depth of 30 km, with a seismic moment, Mo, of 1.6 × 1027 dyne-cm, and a focal mechanism with strike 19.5°, dip 42°, and rake 167°. The long-period magnitude (MA ~ Mw) of this earthquake is estimated to be 7.31. An analysis of well-developed sPn and sSn regional crustal phases from the bandpassed
(0.02–0.25 Hz) seismograms of this earthquake at four stations in Kachchh suggests a focal depth of 30.8 km. 相似文献
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5.
J. A. Marengo I. F. A. Cavalcanti P. Satyamurty I. Trosnikov C. A. Nobre J. P. Bonatti H. Camargo G. Sampaio M. B. Sanches A. O. Manzi C. A. C. Castro C. D'Almeida L. P. Pezzi L. Candido 《Climate Dynamics》2003,21(5-6):459-475
This is a study of the annual and interannual variability of regional rainfall produced by the Center for Weather Forecasts and Climate Studies/Center for Ocean, Land and Atmospheric Studies (CPTEC/COLA) atmospheric global climate model. An evaluation is made of a 9-member ensemble run of the model forced by observed global sea surface temperature (SST) anomalies for the 10-year period 1982–1991. The Brier skill score and, Relative Operating Characteristics (ROC) are used to assess the predictability of rainfall and to validate rainfall simulations, in several regions world wide. In general, the annual cycle of precipitation is well simulated by the model for several continental and oceanic regions in the tropics and mid latitudes. Interannual variability of rainfall during the peak rainy season is realistically simulated in Northeast Brazil, Amazonia, central Chile, and southern Argentina–Uruguay, Eastern Africa, and tropical Pacific regions, where the model shows good skill. Some regions, such as northwest Peru–Ecuador, and southern Brazil exhibit a realistic simulation of rainfall anomalies associated with extreme El Niño warming conditions, while in years with neutral or La Niña conditions, the agreement between observed and simulated rainfall anomalies is not always present. In the monsoon regions of the world and in southern Africa, even though the model reproduces the annual cycle of rainfall, the skill of the model is low for the simulation of the interannual variability. This is indicative of mechanisms other than the external SST forcing, such as the effect of land–surface moisture and snow feedbacks or the representation of sub-grid scale processes, indicating the important role of factors other than external boundary forcing. The model captures the well-known signatures of rainfall anomalies of El Niño in 1982–83 and 1986–87, indicating its sensitivity to strong external forcing. In normal years, internal climate variability can affect the predictability of climate in some regions, especially in monsoon areas of the world. 相似文献
6.
Prantik Mandal R K Chadha C Satyamurty I P Raju N Kumar 《Pure and Applied Geophysics》2005,162(12):2479-2504
Site response in the aftershock zone of 2001 Bhuj Mw 7.7 earthquake has been studied using the H/V spectral ratio method using 454 aftershocks (Mw 2.5–4.7) recorded at twelve three-component digital strong motion and eight three-component digital seismograph sites. The
mean amplification factor obtained for soft sediment sites (Quaternary/Tertiary) varies from 0.75–6.03 times for 1–3 Hz and
0.49–3.27 times for 3–10 Hz. The mean amplification factors obtained for hard sediment sites (hard Jurassic/Mesozoic sediments)
range from 0.32–3.24 times for 1–3 Hz and 0.37–2.18 times for 310 Hz. The upper bounds of the larger mean amplification factors
for 1–3 Hz are found to be of the order of 3.13–6.03 at Chopadwa, Vadawa, Kavada, Vondh, Adhoi, Jahwarnagar and Gadhada, whereas,
the upper bounds of the higher mean amplification factors at 3–10 Hz are estimated to be of the order of 2.00–3.27° at Tapar,
Chopadwa, Adhoi, Jahwarnagar, Gandhidham and Khingarpur. The site response estimated at Bhuj suggests a typical hard-rock
site behavior. Preliminary site response maps for 1–3 Hz and 310 Hz frequency ranges have been prepared for the area extending
from 23–23.85 °N and 69.65–70.85°E. These frequency ranges are considered on the basis of the fact that the natural frequencies
of multi-story buildings (3 to 10 floor) range between 1–3 Hz, while the natural frequencies for 1 to 3 story buildings vary
from 3–10 Hz. The 1–3 Hz map delineates two distinct zones of maximum site amplification (>3 times): one lying in the NW quadrant
of the study area covering Jahwarnagar, Kavada and Gadadha and the other in the SE quadrant of the study area with a peak
of 6.03 at Chopadwa covering an area of 70 km × 50 km. While the 3–10 Hz map shows more than 2 times site amplification value
over the entire study area except, NE quadrant, two patches in the southwest corner covering Bhuj and Anjar, and one patch
at the center covering Vondh, Manfara and Sikara. The zones for large site amplification values (∼3 times) are found at Tapar,
Chopadwa, Adhoi and Chobari. The estimated site response values show a good correlation with the distribution of geological
formations as well as observed ground deformation in the epicentral zone. 相似文献
7.
Summary The horizontal and vertical structures of an upper air cold core vortex over the subtropical latitudes of South America in
the winter of 1999 reveal many features that are different from tropical upper tropospheric cold core vortices. The vortex
in the present study is observed poleward of the subtropical jetstreak. In the middle troposphere, the center of the vortex
is cooler than the periphery by 6 °C. The relative vorticity is greatest just below the tropopause and the vortex presents
a slight eastward tilt in the vertical. The CPTEC Eta regional model simulation dataset has been used to study the life cycle
of the vortex. Intensification and movement of the system are well simulated by the combined effect of divergence and vorticity
advection at 500 hPa. The Lifted Index and CAPE values at the mature stage of the system are not sufficiently high to explain
the precipitation associated with the vortex. However, Q-vector analysis of the model simulation datasets support the observed
precipitation. The precipitation pattern closely follows the 700 hPa vertical velocity. These results indicate that the rain
associated with the vortex has been forced by dynamical lifting rather than by thermodynamic processes. Upper tropospheric
stable conditions are responsible for the shallowness of convection. The vortex presented here is different from subtropical
cyclones, which develop over oceans and have higher intensities. The present vortex development somewhat resembles lee development. 相似文献
8.
Prantik Mandal R. K. Chadha N. Kumar I. P. Raju C. Satyamurty 《Pure and Applied Geophysics》2007,164(11):2235-2254
During the last six years, the National Geophysical Research Institute, Hyderabad has established a semi-permanent seismological
network of 5 broadband seismographs and 10 accelerographs in the Kachchh seismic zone, Gujarat, with the prime objective to
monitor the continued aftershock activity of the 2001 Mw7.7 Bhuj mainshock. The reliable and accurate broadband data for the Mw 7.6 (8 Oct., 2005) Kashmir earthquake and its aftershocks from this network, as well as from the Hyderabad Geoscope station,
enabled us to estimate the group velocity dispersion characteristics and the one-dimensional regional shear-velocity structure
of peninsular India. Firstly, we measure Rayleigh- and Love-wave group velocity dispersion curves in the range of 8 to 35
sec and invert these curves to estimate the crustal and upper mantle structure below the western part of peninsular India.
Our best model suggests a two-layered crust: The upper crust is 13.8-km thick with a shear velocity (Vs) of 3.2 km/s; the
corresponding values for the lower crust are 24.9 km and 3.7 km/sec. The shear velocity for the upper mantle is found to be
4.65 km/sec. Based on this structure, we perform a moment tensor (MT) inversion of the bandpass (0.05–0.02 Hz) filtered seismograms
of the Kashmir earthquake. The best fit is obtained for a source located at a depth of 30 km, with a seismic moment, Mo, of
1.6 × 1027 dyne-cm, and a focal mechanism with strike 19.5°, dip 42°, and rake 167°. The long-period magnitude (MA ~ Mw) of this earthquake is estimated to be 7.31. An analysis of well-developed sPn and sSn regional crustal phases from the bandpassed
(0.02–0.25 Hz) seismograms of this earthquake at four stations in Kachchh suggests a focal depth of 30.8 km. 相似文献
9.
B.K. Rastogi H.K. Gupta Prantik Mandal H.V.S. Satyanarayana M. Kousalya R. Raghavan Richa Jain A.N.S. Sarma N. Kumar C. Satyamurty 《Journal of Seismology》2001,5(4):609-615
A large destructive earthquake occurred on 26 January 2001 in the region of Kutch, Gujarat, in Western India, with magnitude Mw 7.7. The earthquake caused very heavy damage and a large number of casualties with more than 20,000 deaths. A preliminary study of ground deformation, damage pattern and aftershock distribution is presented. 相似文献
10.
A. B. Nunes H. F. Campos Velho P. Satyamurty G. Degrazia A. Goulart U. Rizza 《Boundary-Layer Meteorology》2010,134(1):23-39
A major factor that influences the diurnal variation of turbulent kinetic energy (TKE) is the sensible heat flux at the surface.
Here, the TKE variations are analysed during the morning transition phase because subsequent to the neutral or stable stratification
during the night, peaks of concentration of scalars develop. The characteristics of the TKE during the growth phase of convection
are analysed with the help of two analytical models. For this purpose, a three-dimensional spectral model of the growth of
convection, starting from a neutral layer, and other formulations of micrometeorological parameters such as the convective
and neutral spectra, velocity variance and dissipation rates are utilised. The peak values in the TKE spectra in the lower,
middle and upper levels of the convective boundary layer showed a migration to higher wavelengths as the convection increased
with time. The TKE evolutions generated by the analytical models agree fairly well with the results of large-eddy simulation
for three vertical levels. 相似文献