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1.
The effects of doubled carbon dioxide on rainfall responses to radiative processes of water clouds are investigated in this study.Two groups of two-dimensional cloud-resolving model sensitivity experiments with regard to pre-summer heavy rainfall around the summer solstice and tropical rainfall around the winter solstice are conducted and their five-day averages over the model domain are analyzed.In the presence of radiative effects of ice clouds,doubled carbon dioxide changes pre-summer rainfall from the decrease associated with the enhanced atmospheric cooling to the increase associated with the enhanced infrared cooling as a result of the exclusion of radiative effects of water clouds.Doubled carbon dioxide leads to the reduction in tropical rainfall,caused by the removal of radiative effects of water clouds through the suppressed infrared cooling.In the absence of radiative effects of ice clouds,doubled carbon dioxide changes pre-summer rainfall from the increase associated with the strengthened atmospheric warming to the decrease associated with the weakened release of latent heat caused by the elimination of radiative effects of water clouds.The exclusion of radiative effects of water clouds increases tropical rainfall through the strengthened infrared cooling,which is insensitive to the change in carbon dioxide.  相似文献   

2.
ABSTRACT Rainfall responses to doubled atmospheric carbon dioxide concentration were investigated through the analysis of two pairs of two-dimensional cloud-resolving model sensitivity experiments. One pair of experiments simulated pre-summer heavy rainfall over southern China around the summer solstice, whereas the other pair of experiments simulated tropical rainfall around the winter solstice. The analysis of the time and model domain mean heat budget revealed that the enhanced local atmospheric warming was associated with doubled carbon dioxide through the weakened infrared radiative cooling during the summer solstice. The weakened mean pre-summer rainfall corresponded to the weakened mean infrared radiative cooling. Doubled carbon dioxide increased the mean tropical atmospheric warming via the enhanced mean latent heat in correspondence with the strengthened mean infrared radiative cooling during the winter solstice. The enhanced mean tropical rainfall was associated with the increased mean latent heat.  相似文献   

3.
The precipitation responses to the radiative effects of ice clouds are investigated through analysis of five-day and horizontally averaged data from 2D cumulus ensemble model experiments of a pre-summer torrential precipitation event. The exclusion of the radiative effects of ice clouds lowered the precipitation rate through a substantial reduction in the decrease of hydrometeors when the radiative effects of water clouds were switched on, whereas it increased the precipitation rate through hydrometeor change from an increase to a decrease when the radiative effects of ice clouds were turned off. The weakened hydrometeor decrease was associated with the enhanced longwave radiative cooling mainly through the decreases in the melting of non-precipitating ice to non-precipitating water. The hydrometeor change from an increase to a decrease corresponded to the strengthened longwave radiative cooling in the upper troposphere through the weakened collection of non-precipitating water by precipitation water.  相似文献   

4.
Cloud microphysical and rainfall responses to radiative processes are examined through analysis of cloud-resolving model sensitivity experiments of Typhoon Fitow(2013) during landfall.The budget analysis shows that the increase in the mean rainfall caused by the exclusion of radiative effects of water clouds corresponds to the decrease in accretion of raindrops by cloud ice in the presence of radiative effects of ice clouds,but the rainfall is insensitive to radiative effects of water clouds in the absence of radiative effects of ice clouds.The increases in the mean rainfall resulting from the removal of radiative effects of ice clouds correspond to the enhanced net condensation.The increases(decreases) in maximum rainfall caused by the exclusion of radiative effects of water clouds in the presence(absence) of radiative effects of ice clouds,or the removal of radiative effects of ice clouds in the presence(absence) of radiative effects of water clouds,correspond mainly to the enhancements(reductions) in net condensation.The mean rain rate is a product of rain intensity and fractional rainfall coverage.The radiation-induced difference in the mean rain rate is related to the difference in rain intensity.The radiation-induced difference in the maximum rain rate is associated with the difference in the fractional coverage of maximum rainfall.  相似文献   

5.
Ice clouds are an important component in precipitation systems. The radiative processes of ice clouds directly impact radiation in heat budget and the microphysical processes of ice clouds directly affect latent heat and net condensation through deposition processes, which may eventually change surface rainfall. Thus, torrential rainfall responses to radiative and microphysical processes of ice clouds during a landfall of severe tropical storm Bilis (2006) are investigated with the analysis of sensitivity experiments. The two-dimensional cloud-resolving model is integrated for 3 days with imposed zonally uniform vertical velocity, zonal wind, horizontal temperature and vapor advection from NCEP/GDAS data. One sensitivity experiment excludes the radiative effects of ice clouds and the other sensitivity experiment excludes ice microphysics and associated radiative and microphysical processes. Model domain mean surface rain rate is barely changed by the exclusion of radiative effects of ice clouds due to the small decrease in net condensation associated with the small reduction in latent heat as a result of the offset between the increase in radiative cooling and the decrease in heat divergence. The exclusion of microphysical effects of ice clouds decreases the mean rain rate simply through the suppression of latent heat as a result of the removal of deposition processes. The total exclusion of ice microphysics decreases the mean rain rate mainly through the exclusion of microphysical effects of ice clouds.  相似文献   

6.
Regional dependence of microphysical and radiative effects of ice clouds on vertical structure of tropical tropospheric temperature is examined by analyzing thermodynamic budgets over clear sky, raining stratiform, convective, and non-raining stratiform regions with three two-dimensional sensitivity equilibrium cloud-resolving model simulation data. The decrease in the mean tropospheric cooling caused by radiative effects of ice clouds results from the decreases in local atmospheric cooling over clear sky regions around 12?C16?km through the decrease in heat divergence and below 7.5?km through the decrease in radiative cooling and over non-raining stratiform regions around 6?C13?km through the increase in latent heat. The increase in the mean tropospheric cooling caused by microphysical effects of ice clouds results from the increases in local atmospheric cooling over clear sky regions through the decrease in heat convergence below 4?km the increase in radiative cooling around 4?C8?km and over non-raining stratiform regions through the increase in radiative cooling around 7?C10?km. The raining regions do not show any significant thermal changes due to the cancellation between heat convergence and latent heat.  相似文献   

7.
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.  相似文献   

8.
Effects of vertical wind shear, radiation, and ice clouds on cloud microphysical budget associated with torrential rainfall during landfall of severe tropical storm Bilis (2006) are investigated by using a series of analysis of two-day grid-scale sensitivity experiment data. When upper-tropospheric upward motions and lower-tropospheric downward motions occur on 15 July 2006, the removal of vertical wind shear and ice clouds increases rainfall contributions from the rainfall type (CM) associated with positive net condensation and hydrometeor loss/convergence, whereas the exclusion of cloud radiative effects and cloud-radiation interaction reduces rainfall contribution from CM. The elimination of vertical wind shear and cloud-radiation interaction increases rainfall contribution from the rainfall type (Cm) associated with positive net condensation and hydrometeor gain/divergence, but the removal of cloud radiative effects and ice clouds decreases rainfall contribution from Cm. The enhancements in rainfall contribution from the rainfall type (cM) associated with negative net condensation and hydrometeor loss/convergence are caused by the exclusion of cloud radiative effects, cloud-radiation interaction and ice clouds, whereas the reduction in rainfall contribution from cM results from the removal of vertical wind shear. When upward motions appear throughout the troposphere on 16 July, the exclusion of all these effects increases rainfall contribution from CM, but generally decreases rainfall contributions from Cm and cM.  相似文献   

9.
The radiative and microphysical effects of ice clouds on a torrential rainfall event over Hunan,China in June 2004 are investigated by analyzing the sensitivity of cloud-resolving model simulations.The model is initialized by zonally-uniform vertical velocity,zonal wind,horizontal temperature and vapor advection from National Centers for Environmental Prediction(NCEP) /National Center for Atmospheric Research(NCAR) reanalysis data.The exclusion of radiative effects of ice clouds increases model domain mean surface rain rates through the increase in the mean net condensation associated with the increase in the mean radiative cooling during the onset phase and the increases in the mean net condensation and the mean hydrometeor loss during the mature phase.The decrease in the mean rain rate corresponds to the decreased mean net condensation and associated mean latent heat release as the enhanced mean radiative cooling by the removal of radiative effects of ice clouds cools the mean local atmosphere during the decay phase.The removal of microphysical effects of ice clouds decreases the mean rain rates through the decrease in the mean net condensation during the onset phase,while the evolution of mean net condensation and the mean hydrometeor changes from decrease to increase during the mature phase.The reduction in the mean rain rate is primarily associated with the mean hydrometeor change in the absence of microphysical effects of ice clouds during the decay phase.  相似文献   

10.
Recent studies demonstrate that the Antarctic Ozone Hole has important influences on Antarctic sea ice.While most of these works have focused on effects associated with atmospheric and oceanic dynamic processes caused by stratospheric ozone changes,here we show that stratospheric ozone-induced cloud radiative effects also play important roles in causing changes in Antarctic sea ice.Our simulations demonstrate that the recovery of the Antarctic Ozone Hole causes decreases in clouds over Southern Hemisphere(SH)high latitudes and increases in clouds over the SH extratropics.The decrease in clouds leads to a reduction in downward infrared radiation,especially in austral autumn.This results in cooling of the Southern Ocean surface and increasing Antarctic sea ice.Surface cooling also involves ice-albedo feedback.Increasing sea ice reflects solar radiation and causes further cooling and more increases in Antarctic sea ice.  相似文献   

11.
An infrared radiation parameterization has been applied to a detailed three-dimensional mesoscale model in order to determine whether radiative forcing significantly affects mesoscale atmospheric processes. By taking into account water vapor, liquid water, and carbon dioxide absorption, the scheme differentiates between cloud and clear air regions. The parametric model is presented, along with an overview of the associated mesoscale model.Comparisons between a control run in which only a uniform cooling rate of l K day–1 is specified, and runs with the infrared scheme are made for 12-hr simulations. The major feature of the radiative forcing is seen to be strong cloud-top cooling. This leads to enhanced destabilization of the upper cloud layer, which in turn results in faster growth of clouds (and which extend to higher levels) than in the control experiment. The deeper clouds force a more vigorous secondary circulation, in which thermodynamic feedbacks between clouds and their environment are substantially stronger than in the case with only a constant cooling rate. This confirms findings made in previous studies undertaken in small-scale numerical models. The discussion also focuses upon a simulation in which the cloud-top infrared cooling has been smoothed out over neighboring vertical levels, in order to represent a cloud-top height distribution crudely. The results indicate that although the absolute values of cloud-top cooling are reduced with respect to the unfiltered case, the fact that cooling extends even higher than previously predicted leads to the formation of thicker, more vigorous clouds. These clouds interact more intensely with their environment than in the unfiltered situation, thereby considerably modifying the mesoscale atmosphere.  相似文献   

12.
一维辐射对流模式对云-辐射强迫的数值模拟研究   总被引：1，自引：9，他引：1  
利用一维辐射－对流气候模式, 详细研究了云量、云光学厚度以及云高等要素的变化对大气顶和地面太阳短波辐射和红外长波辐射通量以及云的辐射强迫的影响, 给出了计算这些物理量的经验拟合公式。结果表明, 云具有极为重要的辐射－气候效应。云量、云光学厚度以及云高即使只有百分之几的变化, 所带来的辐射强迫也可以与大气二氧化碳浓度加倍所产生的辐射强迫（3.75 W/m2）相比拟。例如, 当分别给它们+3%的扰动时, 即取云量变化0.015, 云光学厚度变化0.27, 以及云高变化0.15 km时（在实际的地球大气中, 这种尺度的变化是完全可能发生的）, 那么,可以得到地气系统的太阳短波辐射强迫-3.10 W/m2以及红外长波辐射强迫-1.77 W/m2, 二者之和为-4.78 W/m2, 已经完全可以抵消大气二氧化碳浓度加倍所产生的辐射强迫。但是, 当云量、云光学厚度以及云高向相反方向产生类似扰动时, 所产生的辐射强迫可能极大地放大二氧化碳浓度增加所产生的增强温室效应。因此, 研究结果揭示出, 不管是为了解释过去的气候变化, 还是预测未来的气候变化, 亟待加强在一个变化了的气候环境（例如地面温度升高）下, 云将发生何种变化的研究。  相似文献   

13.
邢书强  李小凡 《气象科学》2021,41(4):427-440
以2010年6月19日发生在浙闽赣地区的一次强降水过程为例,利用中尺度WRF模式进行模拟,用模拟资料对该地区降水收支特征和冰云热力作用进行分析。依据局地水汽/热量变化项、水汽/热量辐合辐散项和云凝物辐合辐散项这3个因子可将降水分为8类,其中局地水汽变干和大气变暖、水汽辐合和热量辐散以及云凝物辐合时,降水强度(雨强)最强,而局地水汽变湿和大气变冷、水汽辐合和热量辐散以及云凝物辐合时,降水覆盖率最大。冰云热力效应包括辐射和潜热两部分。基准试验与敏感性试验对比分析表明冰云辐射减弱降水,而冰云潜热增强降水。热量收支对比分析发现冰云辐射造成辐射冷却的减弱在对流层中低层随高度增加,减弱大气不稳定和降水;而冰云潜热造成潜热增强在对流层中高层随高度减小,增强大气不稳定和降水。  相似文献   

14.
Yafei YAN  Yimin LIU 《大气科学进展》2019,36(10):1089-1102
Cloud is essential in the atmosphere, condensing water vapor and generating strong convective or large-scale persistent precipitation. In this work, the relationships between cloud vertical macro- or microphysical properties, radiative heating rate, and precipitation for convective and stratiform clouds in boreal summer over the Tibetan Plateau (TP) are analyzed and compared with its neighboring land and tropical oceans based on CloudSat/CALIPSO satellite measurements and TRMM precipitation data. The precipitation intensity caused by convective clouds is twofold stronger than that by stratiform clouds. The vertical macrophysics of both cloud types show similar features over the TP, with the region weakening the precipitation intensity and compressing the cloud vertical expansion and variation in cloud top height, but having an uplift effect on the average cloud top height. The vertical microphysics of both cloud types under conditions of no rain over the TP are characterized by lower-level ice water, ice particles with a relatively larger range of sizes, and a relatively lower occurrence of denser ice particles. The features are similar to other regions when precipitation enhances, but convective clouds gather denser and larger ice particles than stratiform clouds over the TP. The atmospheric shortwave (longwave) heating (cooling) rate strengthens with increased precipitation for both cloud types. The longwave cooling layer is thicker when the rainfall rate is less than 100 mm d?1, but the net heating layer is typically compressed for the profiles of both cloud types over the TP. This study provides insights into the associations between clouds and precipitation, and an observational basis for improving the simulation of convective and stratiform clouds over the TP in climate models.  相似文献   

15.
The effects of sea surface temperature (SST), radiation, cloud microphysics, and diurnal variations on the vertical structure of tropical tropospheric temperature are investigated by analyzing 10 two-dimensional equilibrium cloud-resolving model simulation data. The increase of SST, exclusion of diurnal variation of SST, and inclusion of diurnal variation of solar zenith angle, radiative effects of ice clouds, and ice microphysics could lead to tropical tropospheric warming and increase of tropopause height. The increase of SST and the suppression of its diurnal variation enhance the warming in the lower and upper troposphere, respectively, through increasing latent heat and decreasing IR cooling. The inclusion of diurnal variation of solar zenith angle increases the tropospheric warming through increasing solar heating. The inclusion of cloud radiative effects increases tropospheric warming through suppressing IR cooling in the mid and lower troposphere and enhancing solar heating in the upper troposphere. The inclusion of ice microphysics barely increases warming in the mid and lower troposphere because the warming from ice radiative effects is nearly offset by the cooling from ice microphysical effects, whereas it causes the large warming enhancement in the upper troposphere due to the dominance of ice radiative effects. The tropopause height is increased mainly through the large enhancement of IR cooling.  相似文献   

16.
Microphysical and radiative effects of ice clouds on diurnal variations of tropical convective and stratiform rainfall are examined with the equilibrium simulation data from three experiments conducted with a two-dimensional cloud resolving model with imposed temporally and zonally invariant winds and sea surface temperature and zero mean vertical velocity. The experiment without ice radiative effects is compared with the control experiment with ice microphysics (both the ice radiative and microphysical effects) to study effects of ice radiative effects on diurnal rainfall variations whereas it is compared with the experiment without ice microphysics to examine ice microphysical effects on the diurnal rainfall variations. The ice radiative processes mainly affect diurnal cycle of convective rainfall whereas the ice microphysical processes have important impacts on the diurnal cycles of both convective and stratiform rainfall. Turning off the ice radiative effects generally enhances convective rainfall during the morning and evening and suppresses convective rainfall in the afternoon whereas turning off the ice microphysical effects generally suppresses convective and stratiform rainfall during the morning and enhances convective and stratiform rainfall in the afternoon and evening. The ice radiative and microphysical effects on the diurnal cycle of surface rainfall are mainly associated with that of vapor condensation and deposition, which is controlled by air temperature through saturation specific humidity. The ice effects on the diurnal cycle of local temperature tendency are largely explained by that of latent heating since the diurnal cycle of radiation is insensitive to the ice effects.  相似文献   

17.
In this study,the effects of key ice microphysical processes on the pre-summer heavy rainfall over southern China during 3-8 June 2008 were investigated.A series of two-dimensional sensitivity cloud-resolving model simulations were forced with zonally uniform vertical velocity,zonal wind,horizontal temperature,and water vapor advection data from the National Centers for Environmental Prediction(NCEP)/Global Data Assimilation System(GDAS).The effects of key ice microphysical processes on the responses of rainfall to large-scale forcing were analyzed by comparing two sensitivity experiments with a control experiment.In one sensitivity experiment,ice crystal radius,associated with depositional growth of snow from cloud ice,was reduced from 100 μm in the control experiment to 50 μm,and in the other sensitivity experiment the efficiency of the growth of graupel from the accretion of snow was reduced to 50% from 100% in the control experiment.The results show that the domain-mean rainfall responses to these ice microphysical processes are stronger during the decay phase than during the onset and mature phases.During the decay phase,the increased mean rain rate resulting from the decrease in ice crystal radius is associated with the enhanced mean local atmospheric drying,the increased mean local hydrometeor loss,and the suppressed mean water vapor divergence.The increased mean rain rate caused by the reduction in accretion efficiency is related to the reduced mean water vapor divergence and the enhanced mean local hydrometeor loss.  相似文献   

18.
The effects of ice microphysics on tropical atmospheric and oceanic variability are investigated with a two-dimensional coupled ocean-cloud resolving atmosphere model forced by the large-scale vertical velocity and zonal wind derived from Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE). The experiment without ice microphysics is compared to a control experiment with ice microphysics. Compared to the control experiment, the experiment without ice microphysics generates a more humid and colder atmosphere by suppressing stratiform clouds and rainfall and associated latent heating; the experiment without ice microphysics produces a saltier mixed layer by a larger saline forcing associated with a weaker stratiform rainfall. Ocean mixed-layer temperature is insensitive to the atmospheric variability associated with ice microphysics.  相似文献   

19.
The surface rainfall processes and diurnal variations associated with tropical oceanic convection are examined by analyzing a surface rainfall equation and thermal budget based on hourly zonal-mean data from a series of two-dimensional cloud-resolving simulations. The model is integrated for 21 days with imposed large-scale vertical velocity, zonal wind, and horizontal advection obtained from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) in the control experiment. Diurnal analysis shows that the infrared radiative cooling after sunset, as well as the advective cooling associated with imposed large-scale ascending motion, destabilize the atmosphere and release convective available potential energy to energize nocturnal convective development. Substantial local atmospheric drying is associated with the nocturnal rainfall peak in early morning, which is a result of the large condensation and deposition rates in the vapor budget. Sensitivity experiments show that diurnal variations of radiation and large-scale forcing can produce a nocturnal rainfall peak through infrared and advective cooling, respectively.  相似文献   

20.
In this study,two convective-stratiform rainfall partitioning schemes are evaluated using precipitation and cloud statistics for different rainfall types categorized by applying surface rainfall equation on grid-scale data from a two-dimensional cloud-resolving model simulation.One scheme is based on surface rainfall intensity whereas the other is based on cloud content information.The model is largely forced by the large-scale vertical velocity derived from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment(TOGA COARE).The results reveal that over 40% of convective rainfall is associated with water vapor divergence,which primarily comes from the rainfall type with local atmospheric drying and water hydrometeor loss/convergence,caused by precipitation and evaporation of rain.More than 40% of stratiform rainfall is related to water vapor convergence,which largely comes from the rainfall type with local atmospheric moistening and hydrometeor loss/convergence attributable to water clouds through precipitation and the evaporation of rain and ice clouds through the conversion from ice hydrometeor to water hydrometeor.This implies that the separation methods based on surface rainfall and cloud content may not clearly separate convective and stratiform rainfall.  相似文献   

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