Vertical Structure Of Precipitation Research Articles

Complex interplay of sulfate aerosols and meteorology conditions on precipitation and latent heat vertical structure

An eight-year satellite observation dataset reveals that sulfate aerosols significantly influence the vertical structure of precipitation and latent heat (LH) in the Beijing-Tianjin-Hebei (BTH) region during summer. In this period, prevalent sulfate aerosols combine with warm, humid southerly winds and elevated convective available potential energy (CAPE), influencing precipitation dynamics. Under polluted conditions with specific CAPE and precipitation top temperature (PTT) ranges, precipitation particles experience accelerated growth within the mixed-phase layer, delineated by the −5 °C to 2 °C isotherms, compared to pristine environments. This results in a marked increase in both the intensity and height at which the maximum LH is released. Subsequent analysis reveals that hygroscopic sulfate aerosols, acting as cloud condensation nuclei (CCN), amplify the collision-coalescence process within the mixed layer amid high cloud water content, propelling rapid precipitation particle growth and elevating the PTT. This warming effect surpasses the cooling contribution from robust CAPE, culminating in a net elevation of PTT under polluted scenarios compared to pristine ones. Additionally, quantification of PTT sensitivity to both CAPE and aerosol optical depth (AOD) unveils a high consistency between satellite-detected PTT responses to CAPE and those predicted by cloud-resolving model simulations. The study deduces that the role of aerosols as CCN in either invigorating or diminishing the collision-coalescence process is contingent on the available cloud water.

Land-sea contrast of vertical structure of precipitation over Sumatra revealed by GPM DPR observations

This study examines the land-sea contrast in the vertical structure of precipitation over Sumatra and its surrounding ocean using eight years (2014–2021) of dual-frequency precipitation radar (DPR) data from the Global Precipitation Measurement (GPM) mission. The study area is segmented into Ocean, Coast I (west coast), Land I (west of Barisan Mountains), Land II (east of Barisan Mountains), and Coast II (east coast). The effective reflectivity factor (Ze), rainfall rate (R), and two raindrop size distribution (DSD) parameters, namely the mass-weighted mean diameter (Dm) and the normalized intercept (Nw), were analyzed. Stratiform and deep convective rainfall were the most frequent types in Coast I, followed by Ocean, Land I, Land II, and Coast II. In contrast, shallow convective rainfall was the most common type in Ocean, followed by Coast I, Land I, Land II, and Coast II. The average rain top height (RTH) was found to be higher in Land II and Coast II than in Ocean, Coast I, and Land I, in accordance with the surface rainfall intensity pattern previously reported by other studies. Furthermore, the data on heavy ice precipitation demonstrated an increase from the ocean to the coast and land, with a significant number of instances observed in Land I, Land II, and Coast II, in addition to Coast I. This contrast in heavy ice precipitation and RTH influences DSD. The land-sea contrast of DSD is more pronounced for deep convective rains. Deep convective exhibited a lower frequency of large raindrops over the ocean than over the coast and land, as reflected in the Dm profile. Conversely, raindrop concentration, particularly small drops, was higher at sea. The percentage of Dm > 2 mm at sea was approximately 2%, rising to 4–6% in Land II and Coast II. The land-sea contrast in the vertical structure of precipitation over Sumatra exhibited apparent diurnal variation. Larger Dm and smaller Nw were observed over Land I and Coast I, particularly in the afternoon and evening, correlating with peak rainfall. This pattern aligns with heavy ice precipitation profiles, vertical relative humidity (RH), and wind profiles. This study highlights the complexities and potential discrepancies between vertical precipitation profiles and surface precipitation data, underscoring the nuanced nature of land-sea precipitation migration.

Seasonal Variation in Vertical Structure for Stratiform Rain at Mêdog Site in Southeastern Tibetan Plateau

Mêdog is located at the entrance of the water vapor channel of the Yarlung Tsangpo Great Canyon on the southeastern Tibetan Plateau (TP). In this study, the seasonal variation in the microphysical vertical structure of stratiform precipitation at the Mêdog site in 2022 was investigated using micro rain radar (MRR) observations, as there is a lack of similar studies in this region. The average melting layer height is the lowest in February, after which it gradually increases, reaches its peak in August, and then gradually decreases. For lower rain categories, the vertical distribution of small drops remains uniform in winter below the melting layer. The medium-sized drops show slight increases, leading to negative gradients in the microphysical profiles. Slight or evident decreases in concentrations of small drops are observed with decreasing height in the premonsoon, monsoon, and postmonsoon seasons, likely due to significant evaporation. The radar reflectivity, rain rate, and liquid water content profiles decrease with decreasing height according to the decrease in concentrations of small drops. With increasing rain rate, the drop size distribution (DSD) displays significant variations in winter, and the fall velocity decreases rapidly with decreasing height. In the premonsoon, monsoon, and postmonsoon seasons, the concentrations of large drops significantly decrease below the melting layer because of the breakup mechanism, leading to the decreases in the fall velocity profiles with decreasing height during these seasons. Raindrops with sizes ranging from 0.3–0.5 mm are predominant in terms of the total drop number concentration in all seasons. Precipitation in winter and postmonsoon seasons is mainly characterized by small raindrops, while that in premonsoon and monsoon seasons mainly comprises medium-sized raindrops. Understanding the seasonal variation in the vertical structure of precipitation in Mêdog will improve the radar quantitative estimation and the use of microphysical parameterization schemes in numerical weather forecast models over the TP.

Precipitation Vertical Structure Characterization: A Feature-Based Approach

Abstract The three-dimensional (3D) structure of precipitation systems is highly dependent on hydrometeor formation processes and microphysics. This study aims to characterize distinct vertical profiles of precipitation regimes by relying on the availability of a high-quality, spatially dense radar network and its capability to observe the 3D structure of the storms. A deep-learning-based framework, coupled with unsupervised clustering methods, is developed to identify types of precipitation structures irrespective of their physical properties. A 6-month period of 3D reflectivity profiles from the Multi-Radar Multi-Sensor (MRMS) network is used to identify different regimes and investigate their properties with respect to the underlying environmental conditions. Dominant features retrieved from radar reflectivity profiles using convolutional neural-network-based autoencoders are employed to identify similar-looking vertical structures using coupled k-means and agglomerative clustering algorithms. The k-means method identifies distinct groups, while the agglomerative clustering visualizes intercluster relationships. The framework identifies 18 clusters that can be broadly combined into five groups of varied echo-top heights. The 18 clusters demonstrate variability with respect to structural features and precipitation rate/type, implying that profiles in each group belong to a physically different precipitation regime. An independent analysis of the regime properties is conducted by matching the MRMS reflectivity profiles with environmental parameters derived from the High-Resolution Rapid Refresh model forecasts. The distribution of the environmental variables confirms cluster-specific feature properties, confirming the physics-based regime separation across the clusters and their dependence on the vertical structure. The identified precipitation regimes can assist in developing physics-guided retrievals and studying precipitation regimes. Significance Statement This study proposes a systematic model to identify precipitation profiles of distinct vertical structures and evaluate their dependence on environmental conditions. The model was developed using ground-based radar observations; however, there is potential to extend this model to reflectivity profiles from both ground- and satellite-based sensors. In addition, the identified precipitation regime clusters could be a proxy for the vertical structure of precipitation systems and assist in determining the structural variability within traditional precipitation type classification (e.g., convective versus stratiform). Moreover, identifying the precipitation regimes could also be used to improve satellite-based precipitation retrievals. Finally, a better understanding of precipitation structure would also help improve the initialization of climate models.

The impacts of dust aerosol and convective available potential energy on precipitation vertical structure in southeastern China as seen from multisource observations

Abstract. The potential impacts of dust aerosols and atmospheric convective available potential energy (CAPE) on the vertical development of precipitating clouds in southeastern China (20–30∘ N, 110–125∘ E) in June, July, and August from 2000 to 2013 were studied using multisource observations. In southeastern China, heavy-dust conditions are coupled with strong northerly winds that transport air masses containing high concentrations of mineral dust particles, with cold temperatures, and with strong wind shear. This leads to weaker CAPE on dusty days compared with that on pristine days. Based on satellite observations, precipitating drops under dusty conditions grow faster in the middle atmospheric layers (with a temperature of between −5 and +2 ∘C) but slower in the upper and lower layers compared with their pristine counterparts. For a given precipitation top height (PTH), the precipitation rate under dusty conditions is lower in the upper layer but higher in the middle and lower layers. Moreover, the associated latent heating rate released by precipitation in the middle layer is higher. The precipitation top temperature (PTT) shows a fairly good linear relationship with the near-surface rain rate (NSRR): the linear regression slope between the PTT and NSRR is stable under dusty and pristine conditions. However, the PTT0 (the PTT related to rain onset) at the onset of precipitation is highly affected by both the CAPE and aerosol conditions. On pristine days, a stronger CAPE facilitates the vertical development of precipitation and leads to a decrease in PTT0, at a rate of −0.65 ∘C per 100 J kg−1 of CAPE for deep convective precipitation (with a variation of 15 %) and at a rate of −0.41 ∘C per 100 J kg−1 of CAPE for stratiform precipitation (with variation of 12 %). After removing the impacts of CAPE on PTT, dust aerosols led to an increase in PTT0, at a rate of +4.19 ∘C per unit aerosol optical depth (AOD) for deep convective precipitation and at a rate of +0.35 ∘C per unit AOD for stratiform precipitation. This study showed clear evidence that meteorological conditions and aerosol conditions combine to impact the vertical development of precipitation clouds. A quantitative estimation of the sensitivity of PTT to CAPE and dust was also provided.

Observed Vertical Structure of Precipitation over the Southeastern Tibetan Plateau in Summer 2021

Observed Vertical Structure of Precipitation over the Southeastern Tibetan Plateau in Summer 2021

Vertical Dependency of Aerosol Impacts on Local Scale Convective Precipitation

AbstractAerosol effects on convective precipitation is critical for understanding human impacts on extreme weather and the hydrological cycle. However, even their signs and magnitude remain debatable. In particular, aerosol effects on vertical structure of precipitation have not been systematically examined yet. Combining 6‐year space‐borne and ground‐based observations over the North China Plain, we show a boomerang‐shape aerosol effect on the top height of convective precipitation, from invigoration to suppression. Further analyses reveal that the aerosols play distinct effects on precipitation rate at different layers. Particularly, near surface precipitation rate shows no significant responses to aerosol and precipitation‐top height due to strong evaporation. The competition of energy between released from condensation and freezing and absorbed by evaporation contributes to different responses of precipitation‐top height to aerosol and can explain the boomerang‐shape aerosol effect.

Vertical Structures Associated with Orographic Precipitation during Warm Season in the Sichuan Basin and Its Surrounding Areas at Different Altitudes from 8-Year GPM DPR Observations

Global precipitation measurement (GPM) is one of the effective means employed to observe orographic precipitation, and its inversed GPM DPR data can be used to study the microphysical structure of precipitation particles. This study considers statistics on convective precipitation (CP) and stratiform precipitation (SP) events over three types of terrain (plains, mountains, and high mountains) using the DPR onboard the GPM Core Observatory from May to September of 2014–2021 to analyze the vertical structure of heavy CP and SP. In mountain areas and high mountain areas, the updraft rendered by topography or seeder-feeder mechanism is not only conducive to the collision and merger of raindrops into large raindrops, but also increases the concentration of small drops, which is the main reason why the occurrence probability of not only large but also small raindrops increases and the horizontal distribution domain of mass weighted average raindrop diameter (Dm) widens. For heavy SP, the occurrence probability of medium-diameter precipitation particles below the freezing height (FzH) over high mountains is greater than those over plains. The precipitation particles above 10 km altitude of high mountains have characteristics, such as lower droplet number concentration and larger diameter, compared with those over plains. Furthermore, the study also analyzed the correlation between storm top altitude (STA) and Dm, water vapor and STA respectively. This study is helpful to further understand the effect of topography on heavy precipitation through cloud microphysical processes and the vertical structure of precipitation.

Aerosol effects on the vertical structure of precipitation in East China

In this paper, we examine the aerosol effects on the vertical structure of precipitation in East China by matching GPM DPR (Global Precipitation Measurement Dual-frequency Precipitation Radar) and MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, Versions2) datasets. It was found that the increase of aerosol will obviously increase the precipitation frequency when AOD (Aerosol Optical Depth) ≤ 0.5, but the excessive aerosol suppresses the precipitation frequency when AOD > 0.5 in some regions. The AOD obviously enhances the radar echo intensity of precipitation and has a stronger impact on convective precipitation. The correlation between AOD and rain rate, and that between AOD and STH (storm top height) are different in different regions of East China. The aerosol reduces the mean droplet concentration in most regions except NC (Northeast China). In most cases, aerosol increases the effective radius of precipitation and has a higher impact on convective precipitation.

The GPM-DPR Blind Zone Effect on Satellite-Based Radar Estimation of Precipitation over the Andes from a Ground-Based Ka-band Profiler Perspective

Abstract A vertically pointing Ka-band radar (Metek MIRA-35C) installed at the Instituto Geofísico del Perú, Atmospheric Microphysics and Radiation Laboratory (LAMAR) Huancayo Observatory, which is located at an elevation of 3.3 km MSL in the Andes Mountains of Peru, is used to investigate the effects of terrain on satellite-based precipitation measurement in the Andes. We compare the vertical structure of precipitation observed by the MIRA-35C with Ka-band radar measurements from the Dual-Frequency Precipitation Radar (DPR) on board the Global Precipitation Measurement (GPM) mission core satellite using an approach based on Taylor’s hypothesis of frozen turbulence that attempts to reduce the impact of spatiotemporal offsets between these two radar measurements. From 3 April 2014 to 20 May 2018, the DPR measured precipitation near LAMAR during 15 of its 157 coincident overpasses. There were six simultaneous observations with MIRA-35C. We found that the average of the DPR’s lowest clutter-free bin is 1.62 km AGL, but the presence of precipitation worsens the situation, causing a 0.4-km-deeper algorithm-detected blind zone for the DPR at the Huancayo Observatory. In the study area, the depth of the clutter layer observed with DPR often extends above the melting layer but can be highly variable, extending even as high as 5 km AGL. These results suggest that DPR estimates of stratiform precipitation over the Andes Mountains are likely underestimated because of the terrain effects on the satellite measurements and problems in its blind zone detection algorithms, highlighting the difficulty in estimating precipitation in mountainous terrain from spaceborne radar.

Measured and modeled vertical structure of precipitation during mixed-phase event near the West Coast of the Antarctic Peninsula

Precipitation structures are easy to detect, however, the mesoscale atmospheric processes which they reflect are challenging to understand in Polar Regions and hard to model numerically. Currently, the spatial distribution of precipitation can be tracked at the resolution of minutes and seconds. For this purpose, the researchers at the Ukrainian Antarctic Akademik Vernadsky station employ several near-ground measurement systems and the Micro Rain Radar for remote vertical measurements. Measurements show stochastic precipitation variability caused by turbulence, precipitation bands related to the atmospheric processes of its formation, phase transition (melting) zones, and wind shears. The time scale of bands in the stratiform precipitation typically varied in the range of 5—15 minutes and corresponded to the 2—15 km spatial scale of atmospheric circulations according to the modeled parameters of the atmosphere. The Polar Weather Research and Forecast (Polar WRF) model was used to reveal the general atmospheric conditions. We also tested and evaluated its ability to reproduce small structures. A simple method based on typical model variables is proposed to identify the precipitation melting layer in the simulation data, similar to that determined by radars. The results were satisfyingly consistent with the position of the 0 °C isotherm in the model and with the radar measurements. In addition, the method highlighted supercooled mixed-phase precipitation. Modeling showed good results for large-scale processes like atmospheric fronts and general air mass features in the case study. However, even at the 1 km resolution the simulation reproduced thin mesoscale precipitation features smoothly, which sometimes looks unrealistic. As for other precipitation peculiarities, like band inclination, melting layer position, and mixed-phase zones, the Polar WRF model demonstrates high consistency with observations. The model can describe the atmospheric conditions except for the investigation of precipitation-initiating mechanisms, which still is a challenge for modeling at a small scale.

Impact of wind pattern and complex topography on snow microphysics during International Collaborative Experiment for PyeongChang 2018 Olympic and Paralympic winter games (ICE-POP 2018)

Abstract. Snowfall in the northeastern part of South Korea is the result of complex snowfall mechanisms due to a highly contrasting terrain combined with nearby warm waters and three synoptic pressure patterns. All these factors together create unique combinations, whose disentangling can provide new insights into the microphysics of snow on the planet. This study focuses on the impact of wind flow and topography on the microphysics drawing of 20 snowfall events during the ICE-POP 2018 (International Collaborative Experiment for PyeongChang 2018 Olympic and Paralympic winter games) field campaign in the Gangwon region. The vertical structure of precipitation and size distribution characteristics are investigated with collocated MRR (micro rain radar) and PARSIVEL (particle size velocity) disdrometers installed across the mountain range. The results indicate that wind shear and embedded turbulence were the cause of the riming process dominating the mountainous region. As the strength of these processes weakens from the mountainous region to the coastal region, riming became less significant and gave way to aggregation. This study specifically analyzes the microphysical characteristics under three major synoptic patterns: air–sea interaction, cold low, and warm low. Air–sea interaction pattern is characterized by more frequent snowfall and vertically deeper precipitation systems on the windward side, resulting in significant aggregation in the coastal region, with riming featuring as a primary growth mechanism in both mountainous and coastal regions. The cold-low pattern is characterized by a higher snowfall rate and vertically deep systems in the mountainous region, with the precipitation system becoming shallower in the coastal region and strong turbulence being found in the layer below 2 km in the mountainous upstream region (linked with dominant aggregation). The warm-low pattern features the deepest system: precipitation here is enhanced by the seeder–feeder mechanism with two different precipitation systems divided by the transition zone (easterly below and westerly above). Overall, it is found that strong shear and turbulence in the transition zone is a likely reason for the dominant riming process in the mountainous region, with aggregation being important in both mountainous and coastal regions.

Enhancement of ice-phase precipitation caused by thermal forcing produces ghost echoes over the Tibetan Plateau

Whether tall storms produce heavy precipitation is currently a controversial topic. Here, we used seven years of observations from the dual-frequency precipitation radar and found that there is a rare but unique vertical precipitation structure over the Tibetan Plateau. The radar echo peaks above the freezing height, which we refer to as a “ghost echo”. The existence of a ghost echo increases the echo-top height but suppresses the increase in droplet size below it, and therefore weakens the near-surface precipitation. Compared with normal echoes, ghost echoes appear more often in the afternoon. The potentially unstable environment produced by thermal forcing is the main cause of ghost echoes, rather than the dynamic factor of wind shear. The ghost echo, which is essentially a mechanism of ice-phase precipitation enhancement, represents a type of tall but weak precipitation. Its existence adds to our current perception of the nature of precipitation.

Tropical TGF Paradox: A Perspective From TRMM Precipitation Radar

AbstractThe Terrestrial Gamma‐ray Flash (TGF) to lightning ratio, computed over the three tropical chimneys, presents a paradox: African thunderstorms produce the most lightning but yield the lowest fraction of TGFs when compared to American and Southeast Asian thunderstorms. To understand the physical insights into this asymmetry, Tropical Rainfall Measuring Mission Precipitation Radar measurements are used to depict the vertical precipitation structure and infer the vertical electrical charge fraction distribution of the observed thunderstorms in the three regions and the thunderstorms during TGF occurrences detected by the AGILE, Fermi‐GBM, and RHESSI sensors. Regional differences show that African thunderstorms are taller, smaller, and have a higher concentration of denser ice particles (graupel and or hail) above the freezing level in addition to having more lightning flashes per thunderstorm. The overall TGF‐related thunderstorms are taller, more intense (0.5–1.5 dBZ) and present similar radar reflectivity decay with height independent of the region. The two dimensional precipitation vertical distribution diagrams indicate that TGF thunderstorms develop to a mature stage. Independent of the region, thunderstorms show a midlevel negative charge center varying from 4.6 to 8.1 km in height and an upper level positive charge center ranging from 7.4 to 14.6 km. TGF thunderstorms have thicker positive inferred charge layer and present larger vertical distances between the opposite charging layers in comparison with the overall thunderstorm population, here defined as Climatology. African TGF thunderstorms have higher fraction of positive charges near the negative layer, helping to produce more and shorter lightning discharges.

Evaluation of coastal Antarctic precipitation in LMDz6 global atmospheric model using ground-based radar observations

In the current context of climate change in the poles, one of the objectives of the APRES3 (Antarctic Precipitation Remote Sensing from Surface and Space) project was to characterize the vertical structure of precipitation in order to better simulate it. Precipitation simulated by models in Antarctica is currently very widespread and it overestimates the data. Sensitivity studies have been conducted using a global climate model and compared to the observations obtained at the Dumont d’Urville coast station, obtained by a Micro Rain Radar (MRR). The LMDz/IPSL general circulation model, with zoomed configuration over Dumont d’Urville, has been considered for this study. A sensitivity study was conducted on the physical and numerical parameters of the LMDz model with the aim of estimating their contribution to the precipitation simulation. Sensitivity experiments revealed that changes in the sedimentation and sublimation parameters do not significantly impact precipitation rate. However, dissipation of the LMDz model, which is a numerical process that dissipates spatially excessive energy and keeps the model stable, impacts precipitation indirectly but very strongly. A suitable adjustment of the dissipation reduces significantly precipitation over Antarctic peripheral area, thus providing a simulated profile in better agreement with the MRR observations.

Observed Vertical Structure of Precipitation Influenced by Dry Air for Landfalling Tropical Cyclones Over China

AbstractThe vertical structure of precipitation and its evolution during midlevel dry‐air intrusion (DAI) for landfalling tropical cyclones (LTCs) over China in the past 10 years were examined using several observed Tropical Rainfall Measuring Mission (TRMM) PR products and a reanalysis data set. We show that in the outer region where the environmental midlevel dry air intrudes more easily, the process of environmental DAI has an important effect on the vertical structure and precipitation of LTCs through promoting substantially stratiform precipitation, while inhibiting infrequent intense convective precipitation. Although the total mean rain rate does not change much during the DAI period, both the mean rain rate and area of stratiform precipitation are almost doubled, while the convective precipitation halves compared to the situation prior to the DAI period. Also, the vertical structure of precipitation relative to the vertical wind shear (VWS) is modulated by the dry air, with a clear stratiform precipitation structure in the DAI region, though the dry‐air distribution of LTCs does not depend on the direction of the VWS but rather on the synoptic environmental collocation. Further analysis shows that the mid‐level DAI is favorable to the generation of stratiform precipitation through producing moderate midlevel convergence and less intense low‐level subsidence, which contribute to the mid‐level spin‐up without spinning down the low‐level circulation. At the same time, it helps in maintaining the uniform stratiform precipitation above the melting layer and homogenizing the low‐level circulation, and thus boosts the development of stratiform precipitation in intensity and area in the outer region.

Diurnal Variations of Precipitation over the Steep Slopes of the Himalayas Observed by TRMM PR and VIRS

This study investigates diurnal variations of precipitation during May–August, 1998–2012, over the steep slopes of the Himalayas and adjacent regions (flat Gangetic Plains–FGP, foothills of the Himalayas–FHH, the steep slope of the southern Himalayas–SSSH, and the Himalayas-Tibetan Plateau tableland–HTPT). Diurnal variations are analyzed at the pixel level utilizing collocated TRMM precipitation radar and visible infrared data. The results indicate that rain parameters (including rain frequency, rain rate, and storm top altitude) are predominantly characterized by afternoon maxima and morning minima at HTPT and FGP, whereas, maximum rain parameters at FHH typically occur in the early morning. Rain parameters at SSSH are characterized by double peaks; one in the afternoon and one at midnight. Over HTPT and FGP, convective activity is strongest in the afternoon with the thickest crystallization layer. Over FHH, the vertical structure of precipitation develops most vigorously in the early morning when the most intense collision and growth of precipitation particles occurs. Over SSSH, moist convection is stronger in the afternoon and at midnight with strong mixing of ice and water particles. The results of harmonic analysis show that rain bands move southward from lower elevation of SSSH to FHH with apparent southward propagation of the harmonic phase from midnight to early morning. Moreover, the strongest diurnal harmonic is located at HTPT, having a diurnal harmonic percentage variance of up to 90%. Large-scale atmospheric circulation patterns exhibit obvious diurnal variability and correspond well to the distribution of precipitation.

Precipitation structure during various phases the life cycle of precipitating cloud systems using geostationary satellite and space-based precipitation radar over Peru

ABSTRACT The life cycle of clouds consists of mainly into three phases, namely developing, mature, and dissipating phases. The information about the vertical structure of the precipitation during different phases of development will improve their representation in the cloud models. Whether specific regimes over Peru favor the formation or decay of the cloud systems and how their intensity varies during different phases of development will provide the insight into the precipitation structure over Peru. We used two satellite-based data, namely from Global Precipitation Measurement dual Precipitation Radar (GPM-DPR) and GOES (Geostationary Operational Environmental Satellite) to expose the vertical structure of precipitation during different phases of the precipitating cloud systems (PCSs). A PCS is defined using the GPM based near surface rainfall data and then GOES-based brightness temperature (BT) is used to identify a specific phase of PCS. In particular 9 hours of BT (e.g., time series of BT) data for a GPM DPR overpass is used to a specific phase of PCS. Once, all the PCSs are identified into a specific phase, their statistical properties are studied. The highest convective fraction area (~26%) and near surface rain rate (RR; 4.97 mm hr−1) are observed in developing phase of PCSs. Also, the convective fraction area and near surface RR decreases as cloud matures, and, least convective fraction area and RR (~4.11 mm hr−1) are observed in dissipating phase PCSs. The vertical structure of precipitation consists of more complex relation among different phases of PCSs. The vertical distributors of hydrometeors (e.g., radar reflectivity, RR, and DSD parameters) during various phases have different characteristics above and below the freezing height (~5 km). For example, convective precipitation has small concentration of higher sized hydrometeors below the freezing height, whereas mature has PCSs show different behavior. The total amount of water analysis shows that liquid and ice water amount varies during different phases and affect the rainfall characteristics. It is observed that precipitation characteristics during different phases are influenced by the Andes Mountain and developing phase PCSs have higher sized of hydrometeors with higher near surface RR at the north-eastern continent of Peru.

Conversion of the Vertical Profile of Reflectivity From Ku-Band to C-Band Based on the Drop Size Distribution Measurements of the Global Precipitation Measurement Mission Dual-Frequency Precipitation Radar

The ground-based radar quantitative precipitation estimation (QPE) faces various challenges including the overestimation caused by the bright band (BB) in the stratiform region and the underestimation in mountainous areas when the terrain-enhanced precipitation occurs at the levels below ground-based radar measurements. The vertical precipitation structure provided by spaceborne radars, i.e., the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and the Global Precipitation Measurement mission (GPM) Dual-frequency PR (DPR), is valuable for mitigating the above problems. Since the spaceborne radars and ground-based radars usually operate in different frequencies, e.g., the TRMM PR and the KuPR of GPM DPR work in Ku-band (13.8 and 13.6 GHz, respectively) and the ground-based radars in western China work in C-band (5.4 GHz), the reflectivity conversion from Ku-band to C-band is necessary before the vertical profile of reflectivity (VPR) measured by spaceborne radars can be utilized to improve the ground-based radar QPE in western China. This study presents a conversion method using GPM DPR measurements, i.e., the drop size distribution (DSD) for different precipitation types (the stratiform with/without BB and the convective cases) and particle phases (the solid, melting, and liquid). Using the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T}$ </tex-math></inline-formula> -matrix method, the reflectivity difference between Ku-band and C-band is found and the Ku-band to C-band conversion relations are derived with the linear regression. These conversion relations have been validated by matching and comparing the converted C-band reflectivity with the C-band ground-based radar measurements. The results demonstrate the effectiveness and reliability of the conversion. This method can be extended for the reflectivity conversion in other frequencies and can facilitate the incorporation of reflectivity measurements from various instruments.

Learning about the vertical structure of radar reflectivity using hydrometeor classes and neural networks in the Swiss Alps

Abstract. The use of radar for precipitation measurement in mountainous regions is complicated by many factors, especially beam shielding by terrain features, which, for example, reduces the visibility of the shallow precipitation systems during the cold season. When extrapolating the radar measurements aloft for quantitative precipitation estimation (QPE) at the ground, these must be corrected for the vertical change of the radar echo caused by the growth and transformation of precipitation. Building on the availability of polarimetric data and a hydrometeor classification algorithm, this work explores the potential of machine learning methods to study the vertical structure of precipitation in Switzerland and to propose a more localised vertical profile correction. It first establishes the ground work for the use of machine learning methods in this context: from volumetric data of 30 precipitation events, vertical cones with 500 m vertical resolution are extracted. It is shown that these cones can well represent the vertical structure of different types of precipitation events (stratiform, convective, snowfall). The reflectivity data and the hydrometeor proportions from the extracted cones constitute the input for the training of artificial neural networks (ANNs), which are used to predict the vertical change in reflectivity. Lower height levels are gradually removed in order to test the ANN's ability to extrapolate the radar measurements to the ground level. It is found that ANN models using the information on hydrometeor proportions can predict from altitudes between 500 and 1000 m higher than the ANN based on only reflectivity data. In comparison to more traditional vertical profile correction techniques, the ANNs show less prediction errors made from all height levels up to 4000 m a.s.l., above which the ANNs lose predictive skill and the performance levels off to a constant value.