Investigation of vertical profile of rain microstructure at Ahmedabad in Indian tropical region
TL;DR: In this article, the microstructure of rain has been studied with observations using a vertical looking Micro Rain Radar (MRR) at Ahmedabad (23.06°N, 72.62°E), a tropical location in the Indian region.
About: This article is published in Advances in Space Research.The article was published on 2010-05-17. It has received 61 citations till now. The article focuses on the topics: Disdrometer & Liquid water content.
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TL;DR: In this article, a simple and realistic approach has been demonstrated for better estimation of rain attenuation using Ku-band signal propagation data and ground rain rate measurements at Kolkata, India.
Abstract: Rain attenuation is an important aspect of signal propagation above 10GHz frequency. The attenuation time series generation from point rain rate measurement is crucial due to unavailability of actual signal measurements. In this paper, a simple and realistic approach has been demonstrated for better estimation of rain attenuation using Ku-band signal propagation data and ground rain rate measurements at Kolkata, India. The ITU-R model of rain attenuation has been modifled by incorporating an efiective slant path model. The efiective slant path has been estimated and modelled in terms of a power-law relationship of rain rate data of 2007{2008. The methodology has been validated with the measured data of 2006. Comparison with ITU-R and SAM clearly demonstrates the improved predictability of the proposed model at the present tropical location.
38 citations
Cites background from "Investigation of vertical profile o..."
...Furthermore, rain characteristics vary with the type of rain (namely, stratiform and convective) and with the climatic zones (namely, tropical and temperate) of the globe [11, 12]....
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TL;DR: In this paper, the average vertical structure is studied in terms of drop size distribution (DSD), fall velocity, rain rate, liquid water content and radar reflectivity profile using a Ka band Micro Rain Radar at three tropical locations in India.
31 citations
TL;DR: In this paper, a revised evaluation of the mean precipitation pathlength HP was performed and the dependence of HP on surface temperature, relative humidity, temperature lapse rate, and degree of condensation in the ascending air were investigated.
Abstract: Precipitation generates small-scale turbulent air flows—the energy of which ultimately dissipates to heat. The power of this process has previously been estimated to be around 2‐4Wm 22 in the tropics: a value comparable in magnitude to the dynamic power of global atmospheric circulation. Here it is suggested that the true value is approximately half the value of this previous estimate. The result reflects a revised evaluation of the mean precipitation pathlength HP. The dependence of HP on surface temperature, relative humidity, temperature lapse rate, and degree of condensation in the ascending air were investigated. These analyses indicate that the degree of condensation, defined as the relative change of the saturated water vapor mixing ratio in the region of condensation, is a major factor determining HP. From this theory the authors develop an estimate indicating that the mean large-scale rate of frictional dissipation associated with total precipitation in the tropics lies between 1 and 2Wm 22 and show empirical evidence in support of this estimate. Under terrestrial conditions frictional dissipation is found to constitute a minor fraction of the dynamic power of condensation-induced atmospheric circulation, which is estimated to be at least 2.5 times larger. However, because HP increases with increasing surface temperature Ts, the rate of frictional dissipation wouldexceedthepowerofcondensation-induceddynamics,andthusblockmajorcirculation,atTs*320Kin a moist adiabatic atmosphere.
28 citations
Cites background from "Investigation of vertical profile o..."
...Such a growth in real clouds in different regions of the world occurs over no more than several hundred meters beyond which there is a sharp decline of rcc (Das et al. 2010; Bennartz et al. 2010; Earle et al. 2011)....
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...than several hundred meters beyond which there is a sharp decline of rcc (Das et al. 2010; Bennartz et al. 2010; Earle et al. 2011)....
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TL;DR: In this paper, the variation of melting layer observed by a vertically looking Micro Rain Radar (MRR) for three years has been presented for two different climatic locations in Indian tropical region.
26 citations
TL;DR: In this article, the authors utilized 2.5 years of concurrent measurements of DSD using a ground-based disdrometer at five diverse climatic conditions in Indian subcontinent and explored the possibility of rain classification based on microphysical characteristics of precipitation.
Abstract: Characterization of precipitation is important for proper interpretation of rain information from remotely sensed data. Rain attenuation and radar reflectivity (Z) depend directly on the drop size distribution (DSD). The relation between radar reflectivity/rain attenuation and rain rate (R) varies widely depending upon the origin, topography, and drop evolution mechanism and needs further understanding of the precipitation characteristics. The present work utilizes 2 years of concurrent measurements of DSD using a ground-based disdrometer at five diverse climatic conditions in Indian subcontinent and explores the possibility of rain classification based on microphysical characteristics of precipitation. It is observed that both gamma and lognormal distributions are performing almost similar for Indian region with a marginally better performance by one model than other depending upon the locations. It has also been found that shape-slope relationship of gamma distribution can be a good indicator of rain type. The Z-R relation, Z = ARb, is found to vary widely for different precipitation systems, with convective rain that has higher values of A than the stratiform rain for two locations, whereas the reverse is observed for the rest of the three locations. Further, the results indicate that the majority of rainfall (>50%) in Indian region is due to the convective rain although the occurrence time of convective rain is low (<10%).
26 citations
References
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TL;DR: In this article, the terminal velocities for distilled water droplets falling through stagnant air are accurately determined using a new method employing electronic techniques, and the over-all accuracy of the massterminal-velocity measurements is better than 0.7 per cent.
Abstract: The terminal velocities for distilled water droplets falling through stagnant air are accurately determined. More than 1500 droplets of mass from 0.2 to 100,000 micrograms, embracing droplets so small that Stokes' law is obeyed up to and including droplets so large that they are mechanically unstable, were measured by a new method employing electronic techniques. An apparatus for the production of electrically charged artificial water droplets at a controllable rate is described. The over-all accuracy of the mass-terminal-velocity measurements is better than 0.7 per cent.
1,465 citations
"Investigation of vertical profile o..." refers methods in this paper
...Using the Gunn and Kinzer (1949) relation, drop diameter is estimated from the terminal velocity....
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TL;DR: In this article, three algorithms extract information on precipitation type, structure, and amount from operational radar and rain gauge data, and statistically summarize the vertical structure of the radar echoes, and determine precipitation rates and amounts on high spatial resolution.
Abstract: Three algorithms extract information on precipitation type, structure, and amount from operational radar and rain gauge data. Tests on one month of data from one site show that the algorithms perform accurately and provide products that characterize the essential features of the precipitation climatology. Input to the algorithms are the operationally executed volume scans of a radar and the data from a surrounding rain gauge network. The algorithms separate the radar echoes into convective and stratiform regions, statistically summarize the vertical structure of the radar echoes, and determine precipitation rates and amounts on high spatial resolution. The convective and stratiform regions are separated on the basis of the intensity and sharpness of the peaks of echo intensity. The peaks indicate the centers of the convective region. Precipitation not identified as convective is stratiform. This method avoids the problem of underestimating the stratiform precipitation. The separation criteria are...
953 citations
TL;DR: In this article, an empirical stratiform-convective classification method based on N 0 and R (rainfall rate) is presented. But, the occurrence of precipitation was found to be 74% (stratiform) and 26% (convection) but total rainfall, on the other hand, was...
Abstract: An analysis of temporal variations in gamma parameters of raindrop spectra is presented utilizing surface-based observations from the Tropical Ocean Global Atmosphere Couple Ocean-Atmosphere Experiment. An observed dramatic change in the N0 parameter, found to occur during rainfall events with little change in rainfall rate, is suggestive of a transition from rain of convective origin to rain originating from the stratiform portion of tropical systems. An empirical stratiform-convective classification method based on N0 and R (rainfall rate) is presented. Properties of the drop size spectra from the stratiform classification are consistent with micro-physical processes occurring within an aggregation/melting layer aloft, which produces more large raindrops and fewer small to medium size raindrops than rain from the convective classification, at the same rainfall rate. The occurrence of precipitation was found to be 74% (stratiform) and 26% (convective), but total rainfall, on the other hand, was ...
685 citations
"Investigation of vertical profile o..." refers background or methods in this paper
...Similar methodology of using drop size distribution is also reported by Tokay and Short (1996)....
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...But, the effects of these smaller drops are less on rain attenuation and are within 5% error limit (Tokay and Short, 1996)....
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TL;DR: In this paper, the authors analyzed 600 h of vertically pointing X-band radar data and 50 h of UHF boundary layer wind profiler data to characterize quantitatively the structure and the causes of the radar signature from melting precipitation.
Abstract: In this study, 600 h of vertically pointing X-band radar data and 50 h of UHF boundary layer wind profiler data were processed and analyzed to characterize quantitatively the structure and the causes of the radar signature from melting precipitation. Five classes of vertical profiles of reflectivity in rain were identified, with three of them having precipitation undergoing a transition between the solid and liquid phase. Only one of them, albeit the most common, showed a radar brightband signature. In-depth study of the bright band and its dependence on precipitation intensity reveals that the ratio of the brightband peak reflectivity to the rainfall reflectivity is constant at 8 dB below 0.5 mm h−1 and then increases to reach 13 dB at 2.5 mm h−1 and 16 dB at 5 mm h−1. The equivalent reflectivity factor of snow just above the melting layer is on average 1–2 dB below the reflectivity of rain just below the melting layer, independent of precipitation intensity. The classical brightband explanation...
456 citations
"Investigation of vertical profile o..." refers background in this paper
...The existence of melting layer is a definite signature of stratiform type of rain (Fabry and Zawadzki, 1995)....
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...The existence of melting layer is a definite signature of stratiform type of rain (Fabry and Zawadzki, 1995)....
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TL;DR: In this article, the authors measured raindrop spectra by two parameters, N0 and A, the intercept and slope respectively of an exponential distribution having the same water content and radar reflectivity factor as the observed sample.
Abstract: Raindrop spectra are measured with an electromechanical raindrop spectrometer, responding to drops >0.3 mm in diameter. The radar reflectivity profile is measured simultaneously with a 5-cm vertically pointing radar. Measured raindrop spectra are described by two parameters, N0 and A, the intercept and slope respectively of an exponential distribution having the same water content and radar reflectivity factor as the observed sample. Sudden variations in the raindrop spectra and in the reflectivity profile during widespread rain situations were observed. Due to the parameterization used, these sudden variations of the spectra can be recognized easily as N0 jumps. It seems that the N0 jumps indicate the transition from one mesoscale area within the precipitation field to another. The characteristics of the N0 jumps and the related cloud physics are discussed. An empirical model is proposed for the relation between the type of raindrop spectra and the convective activity of the precipitating air mass.
317 citations
"Investigation of vertical profile o..." refers background in this paper
...Waldvogel (1974), based on his observation of N0 jump of the exponential drop size distribution, proposed rain classification based on drop size distribution....
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