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CLOUD RADIATIVE AND MICROPHYSICAL EFFECTS ON THE RELATION BETWEEN SPATIAL MEAN rain rate, rain INTENSITY AND FRACTIONAL rainFALL COVERAGE

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Journal of Tropical Meteorology 2018年第3期24卷 346-355页

作者：张晓怡张子涵李小凡 Department of Atmospheric Sciences School of Earth Sciences Zhejiang University Hangzhou 310027 China Airlines Operations Center Xiamen Air Hangzhou 311207 China Zhejiang Province Meteorological Observatory Hangzhou 310017 China

Cloud radiative and microphysical effects on the relation between spatial mean rain rate, rain intensity and fractional rainfall coverage are investigated in this study by conducting and analyzing a series of two-dimensional cloud resolving model sensitivity experiments of pre-summer torrential rainfall in June 2008. The analysis of time-mean data shows that the exclusion of radiative effects of liquid clouds reduces domain mean rain rate by decreasing convective rain rate mainly through the reduced convective-rainfall area associated with the strengthened hydrometeor gain in the presence of radiative effects of ice clouds, whereas it increases domain mean rain rate by enhancing convective rain rate mainly via the intensified convective rain intensity associated with the enhanced net condensation in the absence of radiative effects of ice clouds. The removal of radiative effects of ice clouds decreases domain mean rain rate by reducing stratiform rain rate through the suppressed stratiform rain intensity related to the suppressed net condensation in the presence of radiative effects of liquid clouds, whereas it increases domain mean rain rate by strengthening convective rain rate mainly via the enhanced convective rain intensity in response to the enhanced net condensation in the absence of radiative effects of liquid clouds. The elimination of microphysical effects of ice clouds suppresses domain mean rain rate by reducing stratiform rain rate through the reduced stratiform-rainfall area associated with severely reduced hydrometeor loss.

关键词： pre-summer torrential rainfall radiative effects of liquid and ice clouds rain rate rain intensity fractional rainfall coverage

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Effects of sea surface temperature,cloud radiative and microphysical processes,and diurnal variations on rainfall in equilibrium cloud-resolving model simulations

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Chinese Physics B 2012年第5期21卷 308-315页

作者：蒋哲李小凡周玉淑高守亭 Institute of Remoting Sensing Applications Chinese Academy of Sciences NOAA/NESDIS/Center for Satellite Applications and Research Camp Springs Maryland 21029USA Laboratory of Cloud-Precipitation Physics and Severe Storms(LACS) Institute of Atmospheric PhysicsChinese Academy of Sciences

The effects of sea surface temperature（SST）,cloud radiative and microphysical processes,and diurnal variations on rainfall statistics are documented with grid data from the two-dimensional equilibrium cloud-resolving model simulations.For a rain rate of higher than 3 mm.h 1,water vapor convergence prevails.The rainfall amount decreases with the decrease of SST from 29℃ to 27℃,the inclusion of diurnal variation of SST,or the exclusion of microphysical effects of ice clouds and radiative effects of water clouds,which are primarily associated with the decreases in water vapor convergence.However,the amount of rainfall increases with the increase of SST from 29℃ to 31℃,the exclusion of diurnal variation of solar zenith angle,and the exclusion of the radiative effects of ice clouds,which are primarily related to increases in water vapor convergence.For a rain rate of less than 3 mm.h 1,water vapor divergence prevails.Unlike rainfall statistics for rain rates of higher than 3 mm.h 1,the decrease of SST from 29℃ to 27℃ and the exclusion of radiative effects of water clouds in the presence of radiative effects of ice clouds increase the rainfall amount,which corresponds to the suppression in water vapor divergence.The exclusion of microphysical effects of ice clouds decreases the amount of rainfall,which corresponds to the enhancement in water vapor divergence.The amount of rainfall is less sensitive to the increase of SST from 29℃ to 31℃ and to the radiative effects of water clouds in the absence of the radiative effects of ice clouds.

关键词： rain rate sea surface temperature radiative and microphysical effects of ice and water clouds diurnal variation

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A Study of Air/Space-borne Dual-Wavelength Radar for Estimation of rain Profiles

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Advances in Atmospheric Sciences 2005年第6期22卷 841-851页

作者： Liang LIAO Robert MENEGHINI Goddard Earth Sciences ＆ Technology Center/Caelum Greenbelt MD 20771 Code 614.6 NASA/GSFC Greenbelt MD 20771

In this study, a framework is given by which air/space-borne dual-wavelength radar data can be used to estimate the characteristic parameters of hydrometeors. The focus of the study is on the Global Precipitation Measurement （GPM） precipitation radar, a dual-wavelength radar that will operate in the Ku （13.6 GHz） and Ka （35 GHz） bands. A key aspect of the retrievals is the relationship between the differential frequency ratio （DFR） and the median volume diameter, Do, and its dependence on the phase state of the hydrometeors. It is shown that parametric plots of Do and particle concentration in the plane of the DFR and the radar reflectivity factor in the Ku band can be used to reduce the ambiguities in deriving Do from DFR. A self-consistent iterative algorithm, which does not require the use of an independent pathattenuation constraint, is examined by applying it to the apparent radar reflectivity profiles simulated from a drop size distribution （DSD） model. For light to moderate rain, the self-consistent rain profiling approach converges to the correct solution only if the same shape factor of the Gamma distributions is used both to generate and retrieve the rain profiles. On the other hand, if the shape factors differ, the iteration generally converges but not to the correct solution. To further examine the dual-wavelength techniques, the selfconsistent iterative algorithm, along with forward and backward rain profiling algorithms, are applied to measurements taken from the 2nd generation Precipitation Radar （PR-2） built by the Jet Propulsion Laboratory. Consistent with the model results, it is found that the estimated rain profiles are sensitive to the shape factor of the size distribution when the iterative, self-consistent approach is used but relatively insensitive to this parameter when the forward- and backward-constrained approaches are used.

关键词： rain rate dual-wavelength radar raindrop size distribution and GPM

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A MODELING STUDY OF PARAMETERIZATION SCHEMES FOR DEPOSITIONAL GROWTH OF ICE CRYSTAL:FOUR rainFALL CASES OVER TROPICS AND MIDLATITUDES

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Journal of Tropical Meteorology 2017年第3期23卷 259-268页

作者：辛进李小凡 School of Earth Sciences Zhejiang UniversityHangzhou 310027 China

Depositional growth of ice crystal is one of the major processes for development of precipitation systems and can be represented by depositional growth of cloud ice from cloud water(P_(IDW)) and depositional growth of snow from cloud ice(P_(SFI)) in cloud-resolving model. Four parameterization schemes are analyzed in the cloud-resolving model simulations of four rainfall cases over the tropics and midlatitudes. The comparison of time and model domain mean data shows that Shen's scheme produces the closest rainfall simulation to the observation. Compared to Zeng's scheme,Shen's scheme improves the mean rain-rate simulation significantly through the dramatic decrease in depositional growth of cloud ice from cloud water. Compared to other schemes, Shen's scheme produces the better rainfall simulation via the reduction in the mean rain rate associated with the enhanced gain of cloud water and ice.

关键词： depositional growth of ice crystal rainfall simulation rain rate cloud-resolving-model simulation

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Understanding the Variability of Z-R Relationships Caused by Natural Variations in raindrop Size Distributions(DSD):Implication of Drop Size and Number

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Atmospheric and Climate Sciences 2011年第3期1卷 147-164页

作者： Abe D.Ochou Eric-Pascal Zahiri Bakary Bamba Manlandon Koffi Laboratoire de Physique de l’Atmosphere et Mecanique des fluides(LAPA-MF) Universite de Cocody-AbidjanAbidjanCote d’Ivoire Institut National Polytechnique Houphouet-Boigny YamoussoukroCote d’Ivoire

In the issue of rainfall estimation by radar through the necessary relationship between radar reflectivity Z and rain rate R (Z-R), the main limitation is attributed to the variability of this relationship. Indeed, several pre-vious studies have shown the great variability of this relationship in space and time, from a rainfall event to another and even within a single rainfall event. Recent studies have shown that the variability of raindrop size distributions and thereby Z-R relationships is therefore, more the result of complex dynamic, thermody-namic and microphysical processes within rainfall systems than a convective/stratiform classification of the ground rainfall signature. The raindrop number and size at ground being the resultant of various processes mentioned above, a suitable approach would be to analyze their variability in relation to that of Z-R relation-ship. In this study, we investigated the total raindrop concentration number NT and the median volume di-ameter D0 used in numerous studies, and have shown that the combination of these two ‘observed’ parame-ters appears to be an interesting approach to better understand the variability of the Z-R relationships in the rainfall events, without assuming a certain analytical raindrop size distribution model (exponential, gamma, or log-normal). The present study is based on the analysis of disdrometer data collected at different seasons and places in Africa, and aims to show the degree of the raindrop size and number implication in regard to the Z-R relationships variability.

关键词： raindrop Size Distribution Radar Reflectivity Factor rain rate Median Volume Diameter Total Number of Drops Per Unit Volume Z-R Relationship Convective rain Stratiform rain Squall Lines Thunderstorm

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Analysis of the Effects of rainfall Intensity into the Performance of Video Conferencing

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World Journal of Engineering and Technology 2016年第1期4卷 71-81页

作者： Charles Duhujamahoro Celestin Twizere Patrick Mazimpaka Thierry Ony Shema Nkurunziza Pascal Electrical and Electronics Engineering Department University of Rwanda Butare Rwanda

Attenuation due to rain is an important limitation in the designing of the microwave communication links operating at frequencies above 10 GHz. Video conferencing performs over high-speed link via high-speed satellite (WINDS satellite) transmission in the Ka-band which is vulnerable to attenuation due to rain. Using the ITU-R proposed models for the prediction of rain attenuation gives a good estimation for the microwave propagation loss caused by rain for the temperate regions, but it underestimates the rain attenuation prediction for the monthly variation of rain rate by averaging annual rain rate for particular region. This study was carried out at the University of Rwanda/Huye Campus. The rain rates were predicted for 0.01 percentage of time from rainfall data measured during two months of July and August using the RD-80 Joss and Waldvogel Disdrometer. From the data collected and analyzed, compared with ITU-R model, we can see that where Rwanda region is situated in region K, what is different from the obtained results because the data are collected during months that coincide with a dry season.

关键词： Attenuation rain rate Video Conferencing ITU-R Model

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