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Natural Hazards - Rainfall is the key climatic variable, on which water availability, food security and livelihood depend, especially in an agrarian society like the northeast region of India. It... 相似文献
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C. Prabhakara G. Dalu R. Suhasini J. J. Nucciarone G. L. Liberti 《Meteorology and Atmospheric Physics》1992,47(2-4):177-199
Summary Microwave radiometer brightness temperature (T
b) measurements obtained from satellites over the oceans in dual polarization, at frequencies ranging from 6.6 to 85 GHz, reveal information about the rain and precipitation sized ice. These multifrequency measurements are composited from observations made by the Scanning Multichannel Microwave Radiometer (SMMR) and the Special Sensor Microwave/Imager (SSM/I). TheT
b measurements at 37 GHz, having a field of view (fov) of about 30 km, show relatively strong emissions due to rain, reaching values as large as 260 K over the tropical and mid-latitude rainbelts. Only marginal effects due to scattering by ice above the rain clouds are revealed. At frequencies below 37 GHz, where the fov is much larger than 30 km and the extinction is weaker,T
b is significantly smaller than 260 K. Additional information content about rain, at these low frequencies, is not appreciable. On the other hand, at 85 GHz (fov 15 km), where the extinction is very strong, the sea surface below the clouds is often masked and scattering due to ice above the rain clouds is vividly noticed. However, these high frequency measurements do not yield direct information about rain below the clouds.Recognizing the above merits inherent in the 37 GHz observations the SMMR and SSM/I data at this frequency are utilized to develop and empirical method to retrieve rain rate over oceans. In this method it is assumed that over an oceanic area, the statistics of the observedT
b must be derivable from the statistics of the corresponding rain rates. Furthermore, the underestimation of rain rate, arising from the inability of the radiometer to respond sensitively to rain above a given threshold is empirically rectified with the help of two parameters that depend on the total water vapor content in the atmosphere. Rain rates deduced over the oceans around Japan using the SSM/I data, when compared with those measured by radars that are calibrated against rain gauges, show a good correlation; there is, however, a systematic overestimation. Seasonal mean maps of the rainfall over the global oceans based on SMMR data compare favorably with climatological rain maps over the Atlantic and Pacific Oceans developed by Dorman and Bourke (1979, 1981).With 16 Figures 相似文献
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R. Raghavarao R. Suhasini R. Sridharan B. V. Krishnamurthy O. P. Nagpal 《Journal of Earth System Science》1990,99(3):413-423
The equatorial wave campaign-II which formed a part of the Indian Middle Atmosphere Programme (IMAP), was conducted from SHAR
(13.7°N, 80.2°E) from 15 January to 28 February 1986. Winds were measured from ground to 60 km by means of high altitude balloon
and a meteorological rocket (RH-200), once everyday, for 45 days. The frequencies of the oscillations in the deviations of
the east-west component of the winds from its mean at each height with one kilometer interval were obtained by the maximum
entropy (ME) method and phases/amplitudes of these frequencies were determined by the least squares technique on the wind
variation time series. The ME method has the inherent advantage of providing periodicities up to 1.5 times the data length.
The height structure of the long period waves of > 23 day periodicities that have larger amplitudes nearly by a factor of
2 as compared to the medium (9 to 22 day) or shorter period (4 to 8 day) ones, reveal two height regions of enhanced amplitudes,
one in the troposphere and another in the upper stratosphere/lower mesosphere, that too, mostly in the regions of positive
(westerly increasing or easterly decreasing with height) wind shears. The waves are seen to be inhibited in the negative wind
shear regions. From the abrupt changes in the altitude variation of phase, the possible source region has been identified.
The vertical wavelengths have been estimated to be 34 km and 19 km in the troposphere and lower stratosphere respectively
and 8 km in the upper stratosphere and lower mesosphere. Around 56 km the wave amplitude is reduced to 1/4 of its value below,
while the vertical shear strength in the mean wind doubled up. The tropospheric waves are suggested to be Rossby waves of
extratropical origin penetrating to tropical latitudes. The stratospheric/mesospheric waves however appear to emanate from
a source around the stratopause. 相似文献
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Decisions under uncertainty: a computational framework for quantification of policies addressing infectious disease epidemics 总被引：1，自引：0，他引：1
Armin R. Mikler Sangeeta Venkatachalam Suhasini Ramisetty-Mikler 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(5):533-543
Emerging infectious diseases continue to place a strain on the welfare of the population by decreasing the population’s general
health and increasing the burden on public health infrastructure. This paper addresses these issues through the development
of a computational framework for modeling and simulating infectious disease outbreaks in a specific geographic region facilitating
the quantification of public health policy decisions. Effectively modeling and simulating past epidemics to project current
or future disease outbreaks will lead to improved control and intervention policies and disaster preparedness. In this paper,
we introduce a computational framework that brings together spatio–temporal geography and population demographics with specific
disease pathology in a novel simulation paradigm termed, global stochastic field simulation (GSFS). The primary aim of this
simulation paradigm is to facilitate intelligent what-if-analysis in the event of health crisis, such as an influenza pandemic.
The dynamics of any epidemic are intrinsically related to a region’s spatio–temporal characteristics and demographic composition
and as such, must be considered when developing infectious disease control and intervention strategies. Similarly, comparison
of past and current epidemics must include demographic changes into any effective public health policy for control and intervention
strategies. GSFS is a hybrid approach to modeling, implicitly combining agent-based modeling with the cellular automata paradigm.
Specifically, GSFS is a computational framework that will facilitate the effective identification of risk groups in the population
and determine adequate points of control, leading to more effective surveillance and control of infectious diseases epidemics.
The analysis of past disease outbreaks in a given population and the projection of current or future epidemics constitutes
a significant challenge to Public Health. The corresponding design of computational models and the simulation that facilitates
epidemiologists’ understanding of the manifestation of diseases represents a challenge to computer and mathematical sciences. 相似文献
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