Changes In Vertical Velocity Research Articles

Natural convection flows along a 16-storey high-rise building

The flow caused by natural convection adjacent to a heated vertical wall (wall flow) is an important mechanism in the creation of wind flows in a city when the background wind is weak. The wall flows along a 16-storey building were measured in Guangzhou, China. Fourteen three-dimensional ultrasonic anemometers were installed on three floors to study the boundary layer structure. Continuous measurements were taken during three test periods. The Rayleigh numbers were approximately 1013, 1013 and 1014 at the height of the 5th, 10th and 14th floors, respectively. The diurnal changes in the velocity of the wall flows, the wall surface temperature and the ambient air temperature were analysed.Our new experimental data support the theory that the natural convection boundary layer has a three-layer structure, i.e. an inner viscous layer, a transition layer and an outer turbulent layer, as first proposed theoretically by Wells and Worster. The outer turbulent layer is governed by the law of plumes with a Gaussian profile. The vertical velocity changes with g′4/9x1/3 along the vertical wall, where g′ is the buoyancy force and x is the coordinate along the vertical wall. It was noted that only the building's roof was significantly cooler than the ambient air at night, due to the sky radiation effect, so no downward flow adjacent to the wall caused by the cooling plate effect was found in our field measurements.

Reduced order system identification for UAVs

Abstract Reduced order models representing the dynamic behaviour of symmetric aircraft are well known and can be easily derived from the standard equations of motion. In flight testing, accurate measurements of the dependent variables which describe the linearised reduced order models for a particular flight condition are vital for successful system identification. However, not all the desired measurements such as the rate of change in vertical velocity (Ẇ) can be accurately measured in practice. In order to determine such variables two possible solutions exist: reconstruction or differentiation. This paper addresses the effect of both methods on the reliability of the parameter estimates. The methods are used in the estimation of the aerodynamic derivatives for the Aerosonde UAV from a recreated flight test scenario in Simulink. Subsequently, the methods are then applied and compared using real data obtained from flight tests of the Cranfield University Jetstream 31 (G-NFLA) research aircraft.

Analysis of time-lapse travel-time and amplitude changes to assess reservoir compartmentalization

Fluid depletion within a compacting reservoir can lead to significant stress and strain changes and potentially severe geomechanical issues, both inside and outside the reservoir. We extend previous research of time-lapse seismic interpretation by incorporating synthetic near-offset and full-offset common-midpoint reflection data using anisotropic ray tracing to investigate uncertainties in time-lapse seismic observations. The time-lapse seismic simulations use dynamic elasticity models built from hydro-geomechanical simulation output and a stress-dependent rock physics model. The reservoir model is a conceptual two-fault graben reservoir, where we allow the fault fluid-flow transmissibility to vary from high to low to simulate non-compartmentalized and compartmentalized reservoirs, respectively. The results indicate time-lapse seismic amplitude changes and travel-time shifts can be used to qualitatively identify reservoir compartmentalization. Due to the high repeatability and good quality of the time-lapse synthetic dataset, the estimated travel-time shifts and amplitude changes for near-offset data match the true model subsurface changes with minimal errors. A 1D velocity–strain relation was used to estimate the vertical velocity change for the reservoir bottom interface by applying zero-offset time shifts from both the near-offset and full-offset measurements. For near-offset data, the estimated P-wave velocity changes were within 10% of the true value. However, for full-offset data, time-lapse attributes are quantitatively reliable using standard time-lapse seismic methods when an updated velocity model is used rather than the baseline model.

A traceable physical calibration of the vertical advection‐diffusion equation for modeling ocean heat uptake

AbstractThe classic vertical advection‐diffusion (VAD) balance is a central concept in studying the ocean heat budget, in particular in simple climate models (SCMs). Here we present a new framework to calibrate the parameters of the VAD equation to the vertical ocean heat balance of two fully‐coupled climate models that is traceable to the models' circulation as well as to vertical mixing and diffusion processes. Based on temperature diagnostics, we derive an effective vertical velocity w∗ and turbulent diffusivity for each individual physical process. In steady state, we find that the residual vertical velocity and diffusivity change sign in middepth, highlighting the different regional contributions of isopycnal and diapycnal diffusion in balancing the models' residual advection and vertical mixing. We quantify the impacts of the time evolution of the effective quantities under a transient 1% CO2 simulation and make the link to the parameters of currently employed SCMs.

The "Akopian" vault performed by elite male gymnasts: Which biomechanical variables are related to a judge's score?

Background: A vaulting performance takes a short time and it is influenced by and affects the quantity of mechanical variables. The significant relationships between the vaulting score and specific aspects of the gymnast's vault should conduct coaches to monitor these variables as a part of training or routine testing. Objective: The aim of the current study was to determine the biomechanical variables that are related to a successful performance of the Akopian vaults performed by top level male gymnasts during the World Cup competition. Methods: Fifteen top-level male gymnasts participated in this study. For the 3D analysis, two digital camcorders with a frame rate of 50 Hz were used. The data were digitized by the Simi motion software. The Hay and Reid method was used to identify the biomechanical variables that determine the linear and angular motions of the handspring and front somersault vaults. A correlation analysis was used to establish the relationship between the biomechanical variables and the judges' scores. The level of statistical significance was determined at the value of p < .05. Results: In the Akopian vaults, in five out of 24 variables arising from the deterministic model showed a significant relationship to the score. A significant correlation was found in the maximum height of the body center of mass in the second flight phase, in the height of the body center of mass at the mat touchdown, in the change of the vertical velocity during the take-off from the vaulting table, and in the duration of the second flight phase. Conclusions: The results of the study suggest that a successful execution of Akopian vaults and the achievement of a higher score required: to maximize the change in vertical velocity in the table contact phase and maximize vertical velocity in the table take-off phase; to maximize the amplitude of the second flight phase, which is determined by the duration of the second flight phase, by the maximum height of the body center of mass in the second flight phase and by the distance of the vaulting table during landing; and to maximize the height of the body center of mass in the mat contact phase.

Global versus local effects on climate change in Asia

Regional climate change arises from two processes which, in the real climate system, cannot be separated from each other: local radiative forcing and advection of air masses from regions which themselves have been subject to climate change. In this study, we present an experimental design based on a regional climate model allowing for the assessment of global and local effects on future climate change in Asia. We carry out two runs which are characterized by increasing greenhouse gas concentrations within the model domain, but one (the control run) is one-way nested into a global control run at the lateral and oceanic boundaries while the other (the forced run) is one-way nested into a consistently forced global simulation. The aim is to improve our understanding of the mechanisms of climate change in a regional context. It turns out that temperature and precipitation changes in Asia are indeed mostly related to changes in the advected air masses which enter along the lateral boundaries. Regionally confined greenhouse forcing only affects the atmospheric heating rate while precipitation and atmospheric circulation features remain more or less unchanged. Temperature changes in the forced experiment are partly governed by warmer air masses penetrating the lateral boundaries and partly by a modification of atmospheric circulation processes, including a tendency towards a double-trough structure over Central Asia and changing temperature advection. The trend pattern of precipitation is much more heterogeneous in space but can partly be attributed to changes in horizontal wind divergence and vertical velocity.

Effect of Offshore Wind farm Design on the Vertical Motion of the Ocean

In this study the vertical motion of the ocean is studied numerically. A wake model that includes details of the wind farm design, such as the location of the turbines, diameter of rotors and hub height, is used to calculate the change in surface wind speed resulting from potential wind farms in the Havsul area. Using the calculated wind velocities to force a three dimensional ocean model (Regional Ocean Modeling System), the ocean response to two different wind farm designs is estimated. It is found that the wind farm design has a significant effect on the upwelling and downwelling near the wind farm, as the difference in maximum upwelling velocity after 1 day of simulation exceeds 30 m/day. The pronounced changes in vertical velocities are attributed to changes in the horizontal flow over varying topography due to wind stress modifications by the wind farms.

In situ observations of velocity changes in response to tidal deformation from analysis of the high‐frequency ambient wavefield

AbstractWe report systematic seismic velocity variations in response to tidal deformation. Measurements are made on correlation functions of the ambient seismic wavefield at 2–8 Hz recorded by a dense array at the site of the Piñon Flat Observatory, Southern California. The key observation is the dependence of the response on the component of wave motion and coda lapse time τ. Measurements on the vertical correlation component indicate reduced wave speeds during periods of volumetric compression, whereas data from horizontal components show the opposite behavior, compatible with previous observations. These effects are amplified by the directional sensitivities of the different surface wave types constituting the early coda of vertical and horizontal correlation components to the anisotropic behavior of the compliant layer. The decrease of the velocity (volumetric) strain sensitivity Sθ with τ indicates that this response is constrained to shallow depths. The observed velocity dependence on strain implies nonlinear behavior, but conclusions regarding elasticity are more ambiguous. The anisotropic response is possibly associated with inelastic dilatancy of the unconsolidated, low‐velocity material above the granitic basement. However, equal polarity of vertical component velocity changes and deformation in the vertical direction indicate that a nonlinear Poisson effect is similarly compatible with the observed response pattern. Peak relative velocity changes at small τ are 0.03%, which translates into an absolute velocity strain sensitivity of Sθ≈5 × 103 and a stress sensitivity of 0.5 MPa−1. The potentially evolving velocity strain sensitivity of crustal and fault zone materials can be studied with the method introduced here.

The use of ground penetrating radar for mapping rock stratigraphy and tectonics: Implications for geotechnical engineering

This paper presents results from ground penetrating radar surveys using the SIR-10B GPR instrument (manufactured by Geophysical Survey System Inc., USA), with 400 MHz monostatic antenna (model 5 103). Survey was made over 3 excavation levels along the highway section at the Ras en Naqab escarpment area, Southwest Jordan. A total of 217 m along 4 profiles were covered in the winter of 2012. The objectives of the study are (i) to evaluate the resolution of the GPR technique in the field for detecting and locating anomalies caused by subsurface structures like cavities, fractures and faults, and (ii) to describe stratigraphic nomenclature of the subsurface rocks of the area. 2D interpre- tation of the obtained data and the geological information demonstrate a strong correlation between the GPR anomalies and the subsurface geology. Based upon the lateral and vertical velocity changes with depth, the thickness and orientation of the subsurface layers are outlined. Analysis of the exposed sec- tion shows good agreement between the estimated thicknesses of lithostratigraphic units and the quan- titative assessment of the radar waves velocity inferred from GPR data.

Automatic Isolated-Word Arabic Sign Language Recognition System Based on Time Delay Neural Networks

There have been a little number of attempts to develop an Arabic sign recognition system that can be used as a communication means between hearing-impaired and other people. This study introduces the first automatic isolated-word Arabic Sign Language (ArSL) recognition system based on Time Delay Neural Networks (TDNN). The proposed vision-based recognition system that the user wears two simple but different colors gloves when performing the signs in the data sets within this study. The two colored regions are recognized and highlighted within each frame in the video to help in recognizing the signs. This research uses the multivariate Gaussian Mixture Model (GMM) based on the characteristics of the well known Hue Saturation Lightness Model (HIS) in determining the colors within the video frames. In this research the mean and covariance of the three colored region within the frames are determined and used to help us in segmenting each frame (picture) into two colored regions and outlier region. Finally we propose, create and use the following four features as an input to the TDNN; the centroid position for each hand using the center of the upper area for each frame as references, the change in horizontal velocity of both hands across the frames, the change in vertical velocity of both hands across the frames and the area change for each hand across the frames. A large set of samples has been used to recognize 40 isolated words coded by 10 different signers from the Standard Arabic sign language signs. Our proposed system obtains a word recognition rate of 70.0% in testing set.

Regional simulation of aerosol impacts on precipitation during the East Asian summer monsoon

AbstractThe Weather Research and Forecasting model with Chemistry is used to examine aerosol impacts on precipitation over China during the East Asian summer monsoon (EASM). In the first EASM phase (6 May to 13 June), monsoonal rainband is located to the south of high aerosol areas. The surface cooling by the aerosol radiative effect induces an anticyclonic circulation in northern China, causing a precipitation decrease over southern China. The aerosol microphysical effect tends to broaden the precipitation region. In the second EASM phase (14 June to 5 August), the precipitation band jumps to northern China, where heavy pollution locates. By serving as cloud condensation nuclei, the aerosol microphysical effect causes a reduction of local cloudiness and induces ascent to the north and descent to the south, leading to a precipitation shift from south to north. The aerosol radiative effect strengthens such a meridional asymmetry. Moisture budget analysis shows that the aerosol‐induced anomalies of precipitation in both phases are mainly contributed by the changes in vertical velocity associated with convection, while the horizontal advection of moisture plays a nonnegligible role. Our study highlights that aerosol effects on EASM precipitation depend on the location of monsoon precipitation band and its relative location to aerosols, which may be the main factor that contributed to the discrepancy in literature regarding the aerosol impacts on the so‐called “southern flood and northern flood” over China.

Tutorial: the seismic response to strong vertical velocity change

Conventional seismic data processing, whether pre-stack data conditioning or migration, is designed with the theory of P-wave reflected energy in mind for travel paths involving only a single reflection. Hence, any energy propagating with other modes or travel paths is not dealt with appropriately during conventional processing. It is primarily for this reason that we spend so much time pre-conditioning seismic data to meet the assumptions of the subsequent processes such as migration. Here I consider a typical North Sea environment where there are both strong vertical compaction gradients and high velocity contrasts in the layered Chalk Formation. I assess the behaviour of refracted and mode-converted seismic arrivals when subjected to conventional processing in order to explain how they give rise to anomalous events that contaminate migrated common reflection point gathers and images.

Upper-Troposphere MM5 and WRF Temperature Error and Vertical Velocity Coupling

AbstractThe fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) and the Weather Research and Forecasting Model (WRF) have been employed to predict troposphere temperatures for atmospheric study and operational decision making with positive results. Temperature bias in MM5 and WRF has been noted in previous troposphere studies through radiosonde vertical profile comparison; however, long-range horizontal in situ temperature observations have never been utilized to assess MM5 and WRF upper-troposphere temperature prediction. This study investigates upper-troposphere temperature forecasting of MM5 and WRF utilizing long-range in situ observations linking temperature error to forecast vertical velocity within the upper troposphere over surface elevation changes and different surface types. Temperature observations were taken during flights over North America, Europe, and southwest Asia between 6000 and 7600 m above sea level and compared with MM5 and WRF upper-troposphere forecasts. Regression analysis indicated MM5 and WRF upper-troposphere temperature forecast errors were related to changes in forecast vertical velocities within 100 km laterally of the modeled flight tracks between 39° and 59°N latitude. Temperature error and forecast vertical velocity coupling occurred in MM5 and WRF forecasts over land, while no evidence of temperature error and forecast vertical velocity coupling in MM5 or WRF forecasts was found over water. Evaluation of MM5 and WRF forecasts displayed varying results of temperature error and forecast vertical velocity coupling between specific surface elevations above sea level, vegetative cover, and urban influences.

Effects of temperature on larval swimming patterns regulate vertical distribution relative to thermoclines in Asterias rubens

Asteroid larvae rely mainly on currents for dispersal, predator avoidance, and the location of resources. At small scales, larvae can regulate their vertical positions in the water column by swimming, and consequently, can affect their horizontal displacement. In this study, we examined the effect of water temperature on the survival of larval Asterias rubens, as well as on larval swimming patterns around thermal gradients of various strengths. A response to thermal gradients can be a result of physiological and/or physical processes to improve long-term survival and consequently, facilitate dispersal. We induced spawning of A. rubens in the laboratory, and reared larvae for 5 and 10days. Percent larval survival in temperatures ranging from 6 to 32°C was determined over 48h. Temperatures between 6 and 24°C did not affect survival of 5- or 10-d larvae. For 10-day larvae, low mortality (21.5%) was observed in 28°C, and 100% mortality at 32°C within 6h, suggesting a threshold in survival between the two temperatures. Ten-day old larvae were placed in rectangular plexiglass chambers with homogeneous (6, 12, 18, and 24°C) or thermally-structured water columns that were generated in the laboratory, in which the temperature in the surface and bottom layers was 24 and 12, 18 and 12, 18 and 6, and 12 and 6°C, respectively. Larval swimming patterns were videotaped for 30min and footage was analyzed at 5-min intervals to measure speeds and vertical velocities of all visible larvae using pairs of consecutive frames. Swimming paths were examined by following 21 randomly selected (every 81s) larvae in each treatment for as long as possible. In the absence of a thermal gradient, larval vertical velocity showed a parabolic relationship with temperature, unlike larval speed, which increased linearly, regardless of thermal structure. Net to gross displacement rate was measured for each larval path, and showed a decrease over time, but did not vary with temperature. We concluded that vertical patterns in larval distribution with respect to thermoclines reflect changes in vertical velocity rather than an enhancement of short-term survival. Larval swimming behavior influences vertical distribution, and ultimately, dispersal, settlement and adult populations.

A Radiative–Convective Equilibrium Perspective of Weakening of the Tropical Walker Circulation in Response to Global Warming

Abstract Both observational analysis and GCM simulations indicate that the tropical Walker circulation is becoming weaker and may continue to weaken as a consequence of climate change. Here, the authors use a conceptual radiative–convective equilibrium (RCE) framework to interpret the weakening of the Walker circulation as simulated by the GFDL coupled GCM. Based on the modeled lapse rate and clear-sky cooling rate profiles, the RCE framework can directly compute the change of vertical velocity in the descending branch of the Walker circulation, which agrees with the counterpart simulated by the GFDL model. The results show that the vertical structure of clear-sky radiative cooling rate QR will change in response to the increased water vapor as the globe warms. The authors explain why the change of QR is positive in the uppermost part of the troposphere (&amp;lt;300 hPa) and is negative for the rest of the troposphere. As a result, both the change of clear-sky cooling rate and the change of tropospheric lapse rate contribute to the weakening of circulation. The vertical velocity changes due to the two factors are comparable to each other from the top of the planetary boundary layer to 600 hPa. From 600 to 300 hPa lapse rate changes are the dominant cause of the weakening circulation. Above 300 hPa, the change due to QR is opposite to the change due to lapse rate, which forces a slight increase in vertical velocity that is seen in the model simulation.

The impact of greenhouse gases on past changes in tropospheric ozone

The impact of changes in the abundance of greenhouse gases (GHGs) on the evolution of tropospheric ozone (O3) between 1960 and 2005 is examined using a version of the Goddard Earth Observing System chemistry‐climate model (GEOS CCM) with a combined troposphere‐stratosphere chemical mechanism. Simulations are performed to isolate the relative role of increases in methane (CH4) and stratospheric ozone depleting substances (ODSs) on tropospheric O3. The 1960 to 2005 increases in GHGs (CO2, N2O, CH4, and ODSs) cause increases of around 1–8% in zonal‐mean tropospheric O3 in the tropics and northern extratropics, but decreases of 2–4% in most of the southern extratropics. These O3 changes are due primarily to increases in CH4 and ODSs, which cause changes of comparable magnitude but opposite sign. The CH4‐related increases in O3are similar in each hemisphere (∼6%), but the ODS‐related decreases in the southern extratropics are much larger than in northern extratropics (10% compared to 2%). This results in an interhemispheric difference in the sign of past O3 change. Increases in the other GHGs (CO2 and N2O) and SSTs have only a small impact on the total burden over this period, but do cause zonal variations in the sign of changes in tropical O3 that are coupled to changes in vertical velocities and water vapor.

Intensification of Precipitation Extremes with Warming in a Cloud-Resolving Model

Abstract A cloud-resolving model is used to investigate the effect of warming on high percentiles of precipitation (precipitation extremes) in the idealized setting of radiative-convective equilibrium. While this idealized setting does not allow for several factors that influence precipitation in the tropics, it does allow for an evaluation of the response of precipitation extremes to warming in simulations with resolved rather than parameterized convection. The methodology developed should also be applicable to less idealized simulations. Modeled precipitation extremes are found to increase in magnitude in response to an increase in sea surface temperature. A dry static energy budget is used to relate the changes in precipitation extremes to changes in atmospheric temperature, vertical velocity, and precipitation efficiency. To first order, the changes in precipitation extremes are captured by changes in the mean temperature structure of the atmosphere. Changes in vertical velocities play a secondary role and tend to weaken the strength of precipitation extremes, despite an intensification of updraft velocities in the upper troposphere. The influence of changes in condensate transports on precipitation extremes is quantified in terms of a precipitation efficiency; it does not change greatly with warming. Tropical precipitation extremes have previously been found to increase at a greater fractional rate than the amount of atmospheric water vapor in observations of present-day variability and in some climate model simulations with parameterized convection. But the fractional increases in precipitation extremes in the cloud-resolving simulations are comparable in magnitude to those in surface water vapor concentrations (owing to a partial cancellation between dynamical and thermodynamical changes), and are substantially less than the fractional increases in column water vapor.

Structure of AGCM-Simulated Convectively Coupled Kelvin Waves and Sensitivity to Convective Parameterization

Abstract A study of the convectively coupled Kelvin wave (CCKW) properties from a series of atmospheric general circulation model experiments over observed sea surface temperatures is presented. The simulations are performed with two different convection schemes (a mass flux scheme and a moisture convergence scheme) using a range of convective triggers, which inhibit convection in different ways. Increasing the strength of the convective trigger leads to significantly slower and more intense CCKW activity in both convection schemes. With the most stringent trigger in the mass flux scheme, the waves have realistic speed and variance and also exhibit clear shallow-to-deep-to-stratiform phase tilts in the vertical, as in observations. While adding a moisture trigger results in vertical phase tilts in the mass flux scheme, the moisture convergence scheme CCKWs show no such phase tilts even with a stringent convective trigger. The changes in phase speed in the simulations are interpreted using the concept of “gross moist stability” (GMS). Inhibition of convection results in a more unstable tropical atmosphere in the time mean, and convection is shallower on average as well. Both of these effects lead to a smaller GMS, which leads to slower propagation of the waves, as expected from theoretical studies. Effects such as changes in radiative heating, atmospheric humidity, and vertical velocity following the wave have a relatively small effect on the GMS as compared with the time mean state determined by the convection scheme.

Large-Eddy Simulation of Post-Cold-Frontal Continental Stratocumulus

Abstract Previous large-eddy simulations (LES) of stratocumulus-topped boundary layers have been exclusively set in marine environments. Boundary layer stratocumulus clouds are also prevalent over the continent but have not been simulated previously. A suite of LES runs was performed for a case of continental post-cold-frontal stratocumulus observed by the Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF), located in northern Oklahoma. Comparison with fixed, ground-based sensors necessitated an Eulerian approach in which it was necessary to supply to the model estimates of synoptic-scale advection and vertical motion, particularly given the quickly evolving, baroclinic nature of the synoptic environment. Initial analyses from the Rapid Update Cycle model supplied estimates for these forcing terms. Turbulent statistics calculated from the LES results are consistent with large-eddy observations obtained from millimeter-wave cloud radar. The magnitude of turbulence is weaker than in typical marine stratocumulus, a result attributed to highly decoupled cloud and subcloud circulations associated with a deep layer of negative buoyancy flux arising from the entrainment of warm, free-tropospheric air. Model results are highly sensitive to variations in advection of temperature and moisture and much less sensitive to changes in synoptic-scale vertical velocity and surface fluxes. For this case, moisture and temperature advection, rather than entrainment, tend to be the governing factors in the analyzed cloud system maintenance and decay. Typical boundary layer entrainment scalings applied to this case do not perform very well, a result attributed to the highly decoupled nature of the circulation. Shear production is an important part of the turbulent kinetic energy budget. The dominance of advection provides an optimistic outlook for mesoscale, numerical weather prediction, and climate models because these classes of models represent these grid-scale processes better than they do subgrid-scale processes such as entrainment.

Roles of large-scale forcing, thermodynamics, and cloud microphysics in tropical precipitation processes

Roles of large-scale forcing, thermodynamics, and cloud microphysics in tropical precipitation processes are investigated by analyzing data from a two-dimensional cloud-resolving model simulation. The model is forced by large-scale vertical velocity, zonal wind, horizontal advection, and sea surface temperature observed and derived from TOGA COARE and is integrated from 22 December 1992 to 8 January 1993. The composite analyses of imposed large-scale vertical velocity and water vapor mass flux, and surface rainfall, heat, and cloud microphysical budgets are carried out in eight cases that are categorized by water vapor convergence associated with imposed large-scale vertical velocity and local changes of water vapor and hydrometeor concentration. The analysis of model domain mean surface rainfall budgets shows that the local changes in water vapor and cloud hydrometeor concentration could be as important as the water vapor convergence in producing precipitation. The accurate estimates of these precipitation processes are needed in the climate models to avoid climate biases. The regional analysis shows that the imposed large-scale tropospheric upward motions enhance water vapor convergence and heat divergence and convective rainfall whereas imposed lower-tropospheric downward motions enhance water vapor divergence over stratiform regions and suppress stratiform rainfall. The local atmospheric drying over raining regions is associated with the strengthening of surface rainfall in the cases with mean local atmospheric drying. The local atmospheric moistening is associated with the strengthening of the water vapor convergence over non-raining regions and the convective rainfall is reduced by the weakening of the water vapor convergence over convective regions in the cases with mean local atmospheric moistening. The decrease and increase of mean local hydrometeor concentration are mainly from raining stratiform and convective regions, respectively. The enhancement and reduction of stratiform and convective rainfall are associated with the decrease and increase of local hydrometeor concentration, respectively, in the cases with decrease and increase of mean local hydrometeor concentration.