Convective Rain Events Research Articles

Micro Rain Radar and Radiometric Measurements to Unravel Contrasting Features of Rain Microstructure Below and Above the Boundary Layer

AbstractKa‐band Micro rain Doppler radar is an effective tool to investigate the profiles of precipitation microstructure in terms of the raindrop size distribution (DSD). The DSD parameters that vary appreciably with height are indicative of the associated atmospheric phenomena. Hence the present investigation endeavors to put light on the underlying physical processes responsible for the evolution of varied rain microstructure profiles using micro rain radar (MRR), and radiometric measurements complemented with re‐analysis outputs over an urban tropical location, Kolkata (22.57°N, 88.37°E), India. MRR unravels the prevalence of significant biases in the typical power law relationship (Dm = aRb) between rain rate (R) and mass‐weighted mean drop diameter (Dm) along the rain height, especially during intense convective rain events, above the atmospheric boundary layer (ABL). Consequently, an alternative empirical relation appropriate to account for the R‐Dm variability above the ABL is proposed. Further, radiometric measurements and re‐analysis outputs reveal that the presence of atmospheric instabilities coupled with wind shear impacts above the ABL contributes to the enhanced breakup of raindrops and the deviations in the usual R‐Dm relationship. Thus, the present study intends to highlight the applicability of ground‐based radar measurements over the tropics to devise quantitative precipitation algorithms for reliable rain estimates.

A new power-law model for μ–Λ relationships in convective and stratiform rainfall

Abstract. In this study, we take a closer look at the important issue of μ–Λ relationships in raindrop size distributions (DSDs) by conducting a systematic analysis of 20 months of data collected by disdrometers in the Netherlands. A new power-law model for representing μ–Λ relationships based on the double normalization framework is proposed and used to derive separate μ–Λ relationships for stratiform and convective rain events. The sensitivity of the obtained relationships to measurement uncertainty is studied by applying two different quality control filters based on the mass-weighted mean drop diameter (Dm) and liquid water content (LWC). Our results show that there are significant differences in μ–Λ relationships between convective and stratiform rainfall types. However, the retrieved relationships appear to be quite robust to measurement noise and there is good agreement with other reference relations for similar climatological conditions.

Calibrating radar wind profiler reflectivity factor using surface disdrometer observations

Abstract. This study uses surface disdrometer reflectivity factor estimates to calibrate the vertical and off-vertical pointing radar beams produced by an ultra high frequency (UHF) band radar wind profiler (RWP) deployed at the US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP) Central Facility in northern Oklahoma from April 2011 through July 2019. The methodology consists of five steps. First, the recorded Doppler velocity power spectra are adjusted to account for Nyquist velocity aliasing and coherent integration filtering effects. Second, the spectrum moments are calculated. The third step increases the signal-to-noise ratio (SNR) due to inflated noise power estimates during convective rain events that cause SNR to be biased low. The fourth step determines the RWP calibration constant for one radar beam (called the “reference” beam) by comparing uncalibrated RWP reflectivity factors at 500 m above the ground to 1 min resolution surface disdrometer reflectivity factors. The last step uses the calibrated reference beam reflectivity factor to calibrate the other radar beams during precipitation. There are two key findings. The RWP sensitivity decreased by approximately 3 to 4 dB yr−1 as the hardware aged. This drift was slow enough that the reference calibration constant can be estimated over 3-month intervals using episodic rain events. The calibrated moments are available on the DOE ARM data archive, and the Python processing code is available on public repositories.

Spatial Variation in the Synoptic Structure of Convective Systems over the Great Plains

Abstract During the summer, rainfall over the Rocky Mountains peaks in the afternoon. The diurnal time of maximum rain becomes progressively delayed in going eastward from the Rocky Mountains, such that over much of the Great Plains, maximum rain occurs near 0300 local time. We use Rapid Refresh (RAP) reanalysis data from July and August of 2009–19 to show that there is continuous spatial variation in the mean structure of the high-rain events that occur along this anomalous diurnally propagating rainfall feature. High-rain events that occur farther from the Rockies are more likely to be associated with a larger warm anomaly to the south of the rain event center, a smaller cold anomaly, a larger negative surface pressure anomaly, and increased low-level southerly meridional wind. We also use the Integrated Multi-Satellite Retrievals for GPM (IMERG) rainfall dataset to show that, on hourly time scales, afternoon rainfall that occurs over the Rocky Mountains propagates eastward onto the Great Plains but is rapidly attenuated and becomes negligible east of 100°W. This eastward rainfall propagation appears to be mediated in part by the formation of a low-level cold anomaly and increased surface pressure over the Rocky Mountains, a reversal of the upslope wind, and increased low-level zonal mass convergence over the adjacent near plains. Significance Statement Models have difficulty in simulating the diurnal time of nocturnal rainfall over the Great Plains. Deep convection in this region is often associated with severe weather. Rainfall variability over the Great Plains has a significant impact on soil moisture and agricultural productivity. This paper explores how the structure of deep convective rain events over the Great Plains varies with longitude. The results improve our understanding of deep convection development in the Great Plains and have the potential to contribute to improved forecasts of convective rainfall.

Impact of prevailing atmospheric conditions on diurnal variability of the pre-monsoon rainfall over a tropical location, Kolkata

The annual rainfall amount over Gangetic West Bengal is predominantly determined by monsoon (June to September) and pre-monsoon (March to May) rain events. Consequently, such seasonal precipitation is directly linked to the socio-economic advancement of the area. In this paper, some characteristics of pre-monsoon rainfall over a tropical urban location, Kolkata have been explored utilizing ground-based observations. Pre-monsoon rainfall over Kolkata is characterized by convective rain events and thunderstorms, mostly occurring from afternoon to night (15:30 IST − 21:30 IST) span. Emphasis has been given to the set-in time of pre-monsoon rain events, based upon which they are classified as expected (14:30 IST − 18:30 IST) and delayed (after 18:30 IST). Efforts have been made to assess the sustaining atmospheric conditions (in terms of temperature, water vapour, liquid water content and instability parameter) associated with such rain events prevailing over two non-overlapping time spans of pre-monsoon season. The mean diurnal variations of integrated water vapour (IWV), liquid water path (LWP), and instability parameter, namely, convective available potential energy (CAPE) during the expected and delayed rain event dates show distinct intensity in the increasing trends prior to the respective rainfall peaks. It has been observed that for the delayed events, the temperature difference between ground and 2000 m altitude begins to fall at a later part of the evening in comparison with the expected ones. Overall the investigated parameters exhibited distinguishable nature of variations for the two classes of rain events over the study location.

Links between aerosol radiative forcing and rain characteristics: Stratiform and convective precipitation

The radiative forcing before and after rain events was studied between 12 February 2016 and 14 March 2017 in León, Spain. For this purpose, the radiative forcing fluxes were calculated using the Radiative Transfer Model Global Atmospheric ModEl (RTM GAME). After the application of a set of selection criteria (based on the availability of AERONET data, rain characteristics and lightning maps), 16 stratiform rain events were identified, concentrated in spring and winter, and 15 convective rain events were found concentrated in spring and summer. Rainfall events were grouped according to the atmospheric forcing (ΔFATM) before rain: “low” or “high” (lower or higher than 30 W m−2). The threshold has been set at this value because it is the mean ΔFATM of all the selected events before rain. There were significant statistical differences between stratiform and convective events in rain duration, mean raindrop diameter and parameters a and b of radar reflectivity Z and rainfall intensity R relationship (Z = a Rb). When comparing “low” and “high” groups, raindrop diameter was similar in stratiform (0.51 ± 0.08 vs 0.48 ± 0.12 mm) and convective events (0.96 ± 0.98 vs 0.83 ± 0.63 mm), registering higher values for the latter. In stratiform events, the rain scavenging effect on aerosol particles is clearly observed in the “high” group with a decrease of radiative forcing of −27.0 ± 25.3%, and to a lesser extent, in the “low” group, probably because of a lower aerosol load in the atmosphere. In stratiform events, the mode of the raindrop size gamma distribution presented statistical differences between “low” (0.25 ± 0.13 mm) and “high” (0.35 ± 0.05 mm) groups. We claim that this points towards a relationship between radiative forcing before rain and the specific characteristics of rainfall measured at ground level. This study increases our knowledge on the important role of rainwater as a clean agent of the atmosphere and its impact on climate (through radiative forcing).

The MSG Technique: Improving Commercial Microwave Link Rainfall Intensity by Using Rain Area Detection from Meteosat Second Generation

Commercial microwave link (MWL) used by mobile telecom operators for data transmission can provide hydro-meteorologically valid rainfall estimates according to studies in the past decade. For the first time, this study investigated a new method, the MSG technique, that uses Meteosat Second Generation (MSG) satellite data to improve MWL rainfall estimates. The investigation, conducted during daytime, used MSG optical (VIS0.6) and near IR (NIR1.6) data to estimate rain areas along a 15 GHz, 9.88 km MWL for classifying the MWL signal into wet–dry periods and estimate the baseline level. Additionally, the MSG technique estimated a new parameter, wet path length, representing the length of the MWL that was wet during wet periods. Finally, MWL rainfall intensity estimates from this new MSG and conventional techniques were compared to rain gauge estimates. The results show that the MSG technique is robust and can estimate gauge comparable rainfall estimates. The evaluation scores every three hours of RMSD, relative bias, and r2 based on the entire evaluation period results of the MSG technique were 2.61 mm h−1, 0.47, and 0.81, compared to 2.09 mm h−1, 0.04, and 0.84 of the conventional technique, respectively. For convective rain events with high intensity spatially varying rainfall, the results show that the MSG technique may approximate the actual mean rainfall estimates better than the conventional technique.

Seasonal and diurnal variations of observed convective rain events in Metro Manila, Philippines

The seasonal and diurnal characteristics of localized convective rain events in Metro Manila, Philippines were examined using observations from 16 automated weather stations in the city during the years 2013–2014. After partitioning total rainfall to determine the proportion that is mainly due to localized convection, the diurnal patterns of frequency and intensity of convective rain were then investigated during the northeast monsoon (from November to March), summer (from April to May), and southwest monsoon (from June to October) seasons. Maximum changes in meteorological variables were used to further verify and characterize localized convective rain events over the city. Results show higher rainfall (by ~500 mm) over northern Metro Manila compared to the southern area throughout the period of study. Although total rainfall was highest during the southwest monsoon season, it was during the summer season, when the total rainfall was least, that the largest proportion of rainfall, i.e. 55%, was attributed to convective rain. Almost 45% of the total convective rain events were identified as localized rain events. During the summer season, localized convective rain events in Metro Manila were prominent and vigorous (i.e. greater change in meteorological variables) in the afternoon, and were noted to move along the direction of the prevailing wind, i.e. from the northeastern side of the city towards the west. Increased understanding of the meteorological characteristics of these localized rain events can help improve rainfall forecasting over Metro Manila, leading to better disaster risk reduction and resilience in the city.

Enhancement of the Synthetic Storm Technique for the Prediction of Rain Attenuation Time Series at EHF

A physically based rain attenuation prediction model for Earth-space links, namely the enhanced synthetic storm technique (E-SST), is presented. Different from the original SST, the E-SST receives as input detailed information on the rain height and on the storm velocity, and it discriminates between stratiform and convective rain events having a different impact on the link. The rain attenuation prediction accuracy of E-SST, both as applied directly and as embedded into a more accurate frequency scaling technique, is evaluated against a full year of propagation data collected by the NASA equipment installed at Politecnico di Milano in the frame of the Alphasat Aldo Paraboni propagation experiment. To this aim, a novel methodology to isolate the contribution of rain attenuation from the received beacon power is devised and presented. Results indicate that E-SST represents an accurate and reliable tool for the prediction of rain attenuation at EHF, both on a statistical basis (direct application) and on an event basis (frequency scaling).

Characteristics of the Z–R Relationships Observed Using Micro Rain Radar (MRR-2) over Darjeeling (27.05° N, 88.26° E): A Complex Terrain Region in the Eastern Himalayas

The relationship ( $$\varvec{Z} = \varvec{AR}^{\varvec{b}}$$ ) between radar reflectivity factor, $$\varvec{ Z }$$ and rainfall rate, $$\varvec{R }$$ is studied using the micro rain radar (MRR) observation located over Darjeeling (27.05° N, 88.26° E, 2194 m above the msl) in the foothills of the eastern Himalayan Mountains during Indian summer monsoon and post monsoon seasons (June–October) 2013. Observations from MRR are classified mainly into two types, stratiform and convective, based on the bright band and non-bright band signatures in the radar reflectivity, respectively. We have observed 12 and 7 cases for the stratiform convective rain events, respectively. In the present study MRR is operated mostly during low intensity rainfall rate (0.02–20 mm/h). During southwest monsoon season $$\varvec{Z} {-} \varvec{R }$$ relation for the stratiform and convective rainfall types are found to be $$\varvec{Z} = 272\varvec{R}^{1.78}$$ and $$\varvec{Z} = 192\varvec{R}^{1.54}$$ respectively. $$\varvec{Z} {-} \varvec{R }$$ relation for both stratiform and convective rain shows high temporal variation during different months of monsoon and post monsoon seasons. The coefficient $$\varvec{A}$$ varies between 225 and 289 for stratiform rain and between 153 and 235 for convective rain. The exponent $$\varvec{b}$$ varies between 1.4 and 2.1 for stratiform rain while between 1.2 and 1.8 for convective rain. Interestingly, we observed a distinct relation with smaller values of $$\varvec{A}$$ and $$\varvec{b}$$ for convective rain than stratiform rain over Darjeeling. The height dependence of $$\varvec{A}$$ and $$\varvec{b}$$ are also studied which is found to be very small up to ~ 1.5 km above the surface for both types of the precipitating systems.

Impact of the Window Length of Four-Dimensional Local Ensemble Transform Kalman Filter: A Case of Convective Rain Event

Impact of the Window Length of Four-Dimensional Local Ensemble Transform Kalman Filter: A Case of Convective Rain Event

Rainfall Estimation from Tropospheric Attenuation Affecting Satellite Links

A novel methodology for estimating rainfall rate from satellite signals is presented. The proposed inversion algorithm yields rain rate estimates by making opportunistic use of the downlink signal and exploiting local ancillary meteorological information (0 °C isotherm height and monthly convectivity index), which can be extracted on a Global basis from Numerical Weather Prediction (NWP) products. The methodology includes different expressions to take the different impact of stratiform and convective rain events on the link into due account. The model accuracy in predicting the rain rate is assessed (and compared to the one of other models), both on a statistical and on an instantaneous basis, by exploiting a full year of data collected in Milan, in the framework of the Alphasat Aldo Paraboni propagation experiment.

Validation of the Hurricane Imaging Radiometer Forward Radiative Transfer Model for a Convective Rain Event

The airborne Hurricane Imaging Radiometer (HIRAD) was developed to remotely sense hurricane surface wind speed (WS) and rain rate (RR) from a high-altitude aircraft. The approach was to obtain simultaneous brightness temperature measurements over a wide frequency range to independently retrieve the WS and RR. In the absence of rain, the WS retrieval has been robust; however, for moderate to high rain rates, the joint WS/RR retrieval has not been successful. The objective of this paper was to resolve this issue by developing an improved forward radiative transfer model (RTM) for the HIRAD cross-track viewing geometry, with separated upwelling and specularly reflected downwelling atmospheric paths. Furthermore, this paper presents empirical results from an unplanned opportunity that occurred when HIRAD measured brightness temperatures over an intense tropical squall line, which was simultaneously observed by a ground based NEXRAD (Next Generation Weather Radar) radar. The independently derived NEXRAD RR created the simultaneous 3D rain field “surface truth”, which was used as an input to the RTM to generate HIRAD modeled brightness temperatures. This paper presents favorable results of comparisons of theoretical and the simultaneous, collocated HIRAD brightness temperature measurements that validate the accuracy of this new HIRAD RTM.

Impacts of Local Convective Processes on Rain on the Caribbean Island of Puerto Rico

AbstractThis study aims to determine the impacts of tropical island processes on local convective storms. An analysis of rain events on the island of Puerto Rico between 1 June 2015 and 31 July 2016 showed that local island‐enhanced western storms accounted for 89 of 322 storms. This period is of particular importance for the Caribbean as 2015 was one of the driest years on record. While large‐scale influences such as the El Niño–Southern Oscillation, the North Atlantic Oscillation, African easterly waves, and Saharan dust transport modulate moisture conditions in the region, correlations between precipitation and El Niño–Southern Oscillation (−0.14), North Atlantic Oscillation (−0.42), and Saharan dust (0.1) for 1980–2016 ranged from weak to moderate. Local data for the island of Puerto Rico from weather stations, the Convection, Aerosol, and Synoptic‐Effects in the Tropics field campaign, and the North American Mesoscale model support the initiation or enhancement of convective rain events due to local island processes. In particular, analysis of surface wind speed/direction, convective available potential energy, lifted index, and the bulk Richardson number substantiate local instability due to surface heating, orographic uplift, and sea breeze trade‐wind convergence. These convective forcings along with available precipitable water in excess of 50 mm ultimately led to intense storms despite severe rainfall‐mitigating dust episodes for which aerosol optical thickness exceeded 0.4. These results may have major implications for considering the impacts of local air‐sea‐land interactions on rainfall over other tropical islands.

Characterization of S-Band Dual-Polarized Radar Data for the Convective Rain Melting Layer Detection in A Tropical Region

In the tropical region, convective rain is a dominant rain event. However, very little information is known about the convective rain melting layer. In this paper, S-band dual-polarized radar data is studied in order to identify both the stratiform and convective rain melting layers in the tropical region, with a focus on the convective events. By studying and analyzing the above-mentioned two types of rain events, amongst three radar measurements of reflectivity ( Z ), differential reflectivity ( Z DR ), and cross correlation coefficient ( ρ HV ), the latter one is the best indicator for convective rain melting layer detection. From two years (2014 and 2015) of radar and radiosonde observations, 13 convective rain melting layers are identified with available 0 °C isothermal heights which are derived from radiosonde vertical profiles. By comparing the melting layer top heights with the corresponding 0 °C isothermal heights, it is found that for convective rain events, the threshold to detect melting layer should be modified to ρ HV = 0.95 for the tropical region. The melting layer top and bottom heights are then estimated using the proposed threshold, and it is observed from this study that the thickness of convective rain melting layer is around 2 times that of stratiform rain melting layer which is detected by using the conventional ρ HV = 0.97 .

Anomalies in relative humidity profile in the boundary layer during convective rain

Radiometric observations of relative humidity profile at Kolkata show a significant fall at around 1 to 2km height during convective rain events. An extensive investigation shows that the fall of relative humidity is not seen during calm conditions but is strongly related to the characteristics of temperature lapse rate profiles. Moreover, the phenomenon may have strong association with boundary layer structure. The reason for such anomalies in the planetary boundary layer humidity profile might be due to the release of latent heat at the mentioned altitude. The abundance of pollutant aerosols in urban regions has also been found to contribute to this relative humidity anomaly. It has also been reported that this boundary layer relative humidity is accompanied by high latent heat release and condensation of vapour to liquid which is not much prominent in other rain types as observed in stratiform rain. Hence, convective rain produces some unique boundary layer characteristics which have also been partially supported with allied satellite and multi-station observations.

Informal uncertainty analysis (GLUE) of continuous flow simulation in a hybrid sewer system with infiltration inflow – consistency of containment ratios in calibration and validation?

Abstract. Monitoring of flows in sewer systems is increasingly applied to calibrate urban drainage models used for long-term simulation. However, most often models are calibrated without considering the uncertainties. The generalized likelihood uncertainty estimation (GLUE) methodology is here applied to assess parameter and flow simulation uncertainty using a simplified lumped sewer model that accounts for three separate flow contributions: wastewater, fast runoff from paved areas, and slow infiltrating water from permeable areas. Recently GLUE methodology has been critisised for generating prediction limits without statistical coherence and consistency and for the subjectivity in the choice of a threshold value to distinguish "behavioural" from "non-behavioural" parameter sets. In this paper we examine how well the GLUE methodology performs when the behavioural parameter sets deduced from a calibration period are applied to generate prediction bounds in validation periods. By retaining an increasing number of parameter sets we aim at obtaining consistency between the GLUE generated 90% prediction limits and the actual containment ratio (CR) in calibration. Due to the large uncertainties related to spatio-temporal rain variability during heavy convective rain events, flow measurement errors, possible model deficiencies as well as epistemic uncertainties, it was not possible to obtain an overall CR of more than 80%. However, the GLUE generated prediction limits still proved rather consistent, since the overall CRs obtained in calibration corresponded well with the overall CRs obtained in validation periods for all proportions of retained parameter sets evaluated. When focusing on wet and dry weather periods separately, some inconsistencies were however found between calibration and validation and we address here some of the reasons why we should not expect the coverage of the prediction limits to be identical in calibration and validation periods in real-world applications. The large uncertainties result in wide posterior parameter limits, that cannot be used for interpretation of, for example, the relative size of paved area vs. the size of infiltrating area. We should therefore try to learn from the significant discrepancies between model and observations from this study, possibly by using some form of non-stationary error correction procedure, but it seems crucial to obtain more representative rain inputs and more accurate flow observations to reduce parameter and model simulation uncertainty.

Vertical velocity observed by Doppler lidar during cops - A case study with a convective rain event

Convective and Orographically-Induced Precipitation Study (COPS), conducted in the Black Forest region in Southern Germany and Eastern France during the summer of 2007. From the 13 June to the 16 August 2007, the National Centre for Atmospheric Science (NCAS), Facility for Ground-based Atmospheric Measurement (FGAM) 1.5 lm scanning Doppler lidar was deployed at Super Site R, Achern, in the Rhine Valley, in order to contribute to the extensive COPS observation campaign. The FGAM Doppler lidar system provides measurements of radial wind and aerosol backscatter in the layer 100–1500 m. Profiles of horizontal wind velocity are presented, these being derived from performing azimuth scans. Profiles of vertical velocity, its variance and skewness derived from the vertical scans are also presented and discussed in the paper. Knowledge of vertical velocity skewness is important for the understanding of the structure and origin of turbulent convection in the atmospheric boundary layer (ABL). The skewness of vertical velocity can provide a measure of the asymmetry in the distribution of vertical velocity perturbations within the ABL and can be estimated using the Doppler lidar. In addition, we investigate the behaviour of the boundary layer using data from the FGAM Doppler lidar and Automatic Weather Station (AWS), the University of Basilicata Raman lidar (BASIL) and the DLR’s Poldirad C-band radar. A case study event on the 6 th August 2007 is selected and investigations of possible causes of layers with positive and negative skewness are presented, along with comparisons with output from the National Center for Atmospheric Research (NCAR) Weather Research and Forecasting (WRF) model to assess the accuracy of the model output, including location and timing of rainfall onset.

Modeling Land Surface Processes and Heavy Rainfall in Urban Environments: Sensitivity to Urban Surface Representations

Abstract High-resolution simulations with the Weather Research and Forecasting Model (WRF) are used in conjunction with observational analyses to investigate land surface processes and heavy rainfall over the Baltimore–Washington metropolitan area. Analyses focus on a 6-day period, 21–26 July 2008, which includes a major convective rain event (23–24 July), a prestorm period (21–22 July), and a dry-down period (25–26 July). The performance of WRF in capturing land–atmosphere interactions, the bulk structure of the atmospheric boundary layer, and the rainfall pattern in urban environments is explored. Results indicate that WRF captures the incoming radiative fluxes and surface meteorological conditions. Mean profiles of potential temperature and humidity in the atmosphere are also relatively well reproduced, both preceding and following the heavy rainfall period. However, wind features in the lower atmosphere, including low-level jets, are not accurately reproduced by WRF. The biases in the wind fields play a central role in determining errors in WRF-simulated rainfall fields. The study also investigates the sensitivity of WRF simulations to different urban surface representations. It is found that urban surface representations have a significant impact on the surface energy balance and the rainfall distribution. As the impervious fraction increases, the sensible heat flux and the ground heat flux increase, while the latent heat flux decreases. The impact of urban surface representations on precipitation is as significant as that of microphysical parameterizations. The fact that changing urban surface representations can significantly alter the rainfall field suggests that urbanization plays an important role in modifying the regional precipitation pattern.

TRMM 위성의 강수레이더에서 관측된 동아시아 여름 강수의 특성

The characteristics and vertical structure of the rainfall are examined in terms of rain types using TRMM (Tropical Rainfall Measuring Mission) PR (Precipitation Radar) data during the JJA period of 2002-2006 over three different regions; midlatitude region around the Korean Peninsula (EA1), subtropical East Asia (EA2), and tropical East Asia (EA3). The convective rain fraction in the EA1 region is 12.2%, which is smaller by 6% than those in the EA2 and EA3 regions. EA1 shows less frequent convective rain events, which are about 0.5 times as many as those in EA3. EA1 produces the mean convective rain rate of 10.4 mm/h that is about 40% larger than EA2 and EA3 while all regions have similar mean stratiform rain rate. The relationships between storm height and rain rate indicate that the rain rate is proportional to the storm height. Based on the vertical structure of radar reflectivity, EA1 produces deeper and stronger convective clouds with higher rain rate compared to the other regions. In EA3, radar reflectivity increases distinctly toward the land surface at altitude below 5 km, indicating more dominant coalescence-collision processes than the other regions. Furthermore, the bright band of stratiform rain clouds in EA3 is very distinct. In convective rain clouds, the first EOFs of radar reflectivity profiles are similar among the three regions, while the second EOFs are slightly different. The larger variability exists at upper layers for EA1 while it exits at lower levels for EA3.