Surface Rain Research Articles

Effects of anthropogenic aerosols and sea salt aerosols during a summer precipitation event in the Yangtze River Delta

Currently, we know little about the effects of anthropogenic aerosols (AAs) and sea salt aerosols (SSAs) on heavy precipitation over the densely populated coastal areas. In this view, we developed a local aerosol activation parametrization scheme which conforms to the Yangtze River Delta (YRD) characteristics using cloud condensation nucleus (CCN) with supersaturation at 0.4 (CCN0.4) and aerosol optical depth (AOD) data at 550 nm (AOD550) to improve the model performance. Meanwhile, we simulated a heavy precipitation over the YRD during early summer using the WRF-Chem model (version 4.1) with the Morrison microphysics scheme. Increased AAs and SSAs presented opposite responses in droplets concentrations and precipitation intensity. The increased AAs increased the aerosol concentrations, leading to more but smaller droplets; and the cloud droplets mixing ratio Qc was slightly increased by 17.7% due to the weakened auto-conversion from droplets to raindrops, while the rain mixing ratio Qr was decreased by about 5.7%. On the contrary, presence of SSAs increased the effective (EFC) radius of cloud droplets because of the larger particles. Along with increased AAs, due to the influences of decreased Qr and smaller droplets, probability density function (PDF) of the hourly surface rain rates shifted to the smaller values (< 0.5 mm/h), which was caused by lowered latent heat release resulting from the enhanced rain evaporative cooling and weakened condensation rate, weakening the convective intensity and updrafts. Meanwhile, decreased updrafts resulted in fewer cloud droplets being transformed to the upper air, less accretion of droplets by ice crystal and snow, and reduced ice mixing ratio Qi and snow mixing ratio Qs. The averaged surface precipitation accumulated for 24 h decreased by about 7.2%, and the intensity of radar reflectivity was decreased by about 7.0%. In contrast, presence of SSAs enhanced the auto-conversion droplets and weakened the evaporation of raindrops, thus increasing the Qr. In this case, the 24-h accumulated averaged surface rainfall was increased by about 30.1% with the larger radar reflectivity and increased area of large reflectivity values (> 20 dbz). The latent heat release and related microphysical processes were enhanced due to the changes of conversion rate, which, together with the increased Qr and larger droplets, strengthened the precipitation, increased the incidence of heavier precipitation (> 2 mm/h), and enhanced the ice-phase microphysical processes.

Regional variability of precipitation characteristics in Tropical Cyclones over the North Indian Ocean from GPM-DPR measurements

Global Precipitation Measurement mission (GPM) satellite carries a dual-frequency precipitation radar (DPR) which provides the three-dimensional structure of precipitating systems with a coarser spatial resolution of 5 km. GPM measurements provide a unique opportunity to examine the microphysical properties of precipitating systems over the ocean, where direct precipitation measurements are extremely rare. The present study uses GPM-DPR products such as surface rainfall rate, radar reflectivity factor, storm top height, mass-weighted mean diameter (Dm), and normalized intercept parameter (Nw) to examine the regional variability of precipitation characteristics in Tropical Cyclones (TCs). The precipitation characteristics are investigated in the Eye Wall (EW), Inner Rain band (IR), and Outer Rain band (OR) regions of TCs over the North Indian Ocean using 8 years of GPM-DPR data (2014–2021). The variation in precipitation characteristics is quantified in the light of predominant precipitation regimes and microphysical processes in different regions of TCs over two oceanic basins Arabian Sea (AS) and the Bay of Bengal (BOB). Our results suggested that the storms are more intense (higher reflectivity), taller and characterized by higher surface rain intensity with bigger Dm and higher Nw in the EW region as compared to the IR and OR regions. The stratiform rain fraction dominates over convective rain fraction in IR and OR regions of TCs. However, stratiform rain fraction is comparable to convective rain fraction in EW region of TCs over BOB. The two dimensional frequency distribution (CFAD) exhibits highly concentrated (broadly distributed) reflectivity values in EW (OR), whereas IR region depicts intermediate characteristics of EW/OR regions. Raindrops encounter significant amount of growth in convective rainfall than stratiform in EW region. The coalescence/break up process is relatively more apparent in EW region of TCs over BOB. Though the bulk of precipitation features are commonly observed over AS and BOB, EW regions of TCs show distinct features over AS and BOB. The observed variations in the precipitation and DSD characteristics have implications for cloud modeling parameterization schemes over the NIO.

Climatology and characteristics of rapidly intensifying tropical cyclones over the North Indian Ocean

AbstractRapid intensification (RI) of a tropical cyclone (TC) is defined as an increase in the wind speed by 30 knots within 24 hours. It is a less understood process, particularly for TCs over the North Indian Ocean. We considered data for the past 39 years (1982–2020) from the JTWC and studied the climatology of TCs. We found that, out of 197 cases, 44 TCs (22%) experienced RI. There is a significant increasing trend in RI TCs frequency and duration over the Arabian Sea (AS). Lifetime maximum intensity (LMI) is significantly higher, and genesis to LMI duration is also significantly longer for TCs undergoing RI over the AS. LMI is double for RI TC than for non‐RI (NRI) TC. The longer duration to achieve the higher maximum intensity resulted in a longer total lifespan for RI TCs. All TCs reaching a super cyclonic storm category underwent RI and generally, RI onset happens in the depression stage. The composites are prepared to understand the characteristics of RI TCs in contrast to NRI TCs. For the RI TC composite, the period includes 12 hours before and 24 hours after the RI onset. For the NRI TC, we considered 36 hours starting from the initial intensification stage. The analysis shows the RI TCs are embedded in the warm water regions with ocean heat content of 90–100 kJ · cm−2 and strong latent heat flux transport. RI TCs also have higher positive low‐level relative vorticity, higher upper‐level divergence, and higher mid‐level relative humidity, with higher moisture content around the TC centre. Deep clouds with 208 K &lt; IRBT &lt;240 K dominate in RI TCs. The total surface rainfall for RI cases is symmetric around the centre. RI TCs have higher rainfall fractions with intense surface rain rates for stratiform and convective rainfall during the pre‐monsoon.

Climatologies of Mesoscale Convective Systems over China Observed by Spaceborne Radars

Abstract This study investigates the characteristics of mesoscale convective systems (MCSs) as a function of MCS organizational mode over China, using long-term precipitation radar observations from the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement Mission (GPM). The spaceborne radar-based MCS climatology shows maximum population over low-elevation regions, marked decrease over the foothills, and minimum frequency over the Tibetan Plateau. Linear and nonlinear MCSs account for 17% and 83% of the MCSs over China, respectively. Linear MCSs have much stronger convective intensity and heavier precipitation than nonlinear MCSs, as indicated by TRMM convective proxies. Interestingly, though broad-stratiform MCSs have the weakest convection, they produce the heaviest (maximum) rain rate and the largest amount of heavy rainfall among nonlinear MCSs. Among various types of linear MCSs, bow echoes (BEs) and no-stratiform (NS) systems exhibit the strongest convective intensity, embedded lines exhibit the weakest, and convective lines with trailing/leading stratiform in between. BEs and NSs share the most vertically extended structure, strongest microwave ice scattering, and highest lightning flash rates, but NS systems have a much lower surface rain rate likely due to a drier environment. Vertical radar reflectivity profiles suggest that both ice-based and warm-rain processes play an important role in the precipitation processes of linear MCSs over China, including the most intense BE storms. In short, this study helps to better understand the convective organization, precipitation structure, and ensemble microphysical properties of MCSs over China, and potentially provides guidelines for evaluating high-resolution model simulations and satellite rainfall retrievals for monsoonal MCSs.

Large‐eddy simulations of drizzling shallow cumuli using a turbulence‐aware autoconversion parametrization

AbstractTurbulence in clouds enhances collision between cloud droplets, which is critical to drizzle formation in shallow cumulus clouds. In this study, we develop an autoconversion parametrization that considers the turbulence‐induced collision enhancement (TICE) obtained from a particle trajectory model. We implement the developed parametrization to a large‐eddy simulation model and simulate the Rain In Cumulus over the Ocean (RICO) case to investigate the effects of TICE on shallow cumulus clouds and their sensitivities to the cloud droplet number concentration and horizontal grid resolution. TICE significantly increases the autoconversion rate, leading to large increases in the accretion rate, rainwater path and surface rain rate. The simulations of shallow cumulus clouds are highly sensitive to the cloud droplet number concentration and horizontal grid resolution, and the inclusion of TICE overall reduces the sensitivities. For example, the large rainwater path and surface rain rate that appear when cloud droplet number concentration is relatively low are reduced by TICE, whereas the very small rainwater path and surface rain rate that appear when cloud droplet number concentration is relatively high are increased by TICE. Comparisons with two other TICE‐aware parametrizations based on direct numerical simulation results of droplet collisions in turbulence show that there are substantial differences in TICE effects for different parametrizations, which implies a large uncertainty in simulating turbulent clouds. Among the three parametrizations, the parametrization developed in this study shows intermediate TICE‐induced increases in rainwater path and surface rain rate.

Investigating the feasibility of using precipitation measurements from weather RaDAR to estimate potential recharge in regional aquifers: the Majella massif case study in Central Italy

Rain gauge spatial sparsity and temporal discontinuity of data represent one of the major issues for reliable recharge estimations. In the past decades, the use of ground-based microwave weather RaDAR has dramatically improved quantitative rainfall estimation by providing spatially continuous estimates of rainfall over an area of more than 400 km2 every 10 minutes. Furthermore, weather RaDAR data have also proved relatively reliable in mountainous areas. These paramount features of RaDAR-derived precipitation data could improve the estimation of potential recharge of aquifers, which rely on geospatializations (e.g., Thiessen polygons) of rainfall data collected by a sparse rain gauge network which often shows lacking at high altitude (i.e., recharge areas), introducing additional uncertainty in the inflow volumes. Weather RaDAR rainfall estimation is also affected by various sources of error, which can be reduced by proper post-processing; however, uncertainties remain, especially for surface rain rate estimations. Despite the currently necessary complex numerical processing, the purpose of the study is to evaluate the use of the weather RaDAR data as an alternative or in addition to meteorological data. Based on the above considerations, the feasibility of using RaDAR-based precipitation data to estimate aquifer potential recharge and calculate a detailed water budget in the areas characterized by high elevations, such as the Majella massif in the central Apennines, has been evaluated. To address this objective, the water budget has been calculated in the 2017-2018 period using both RaDAR-based precipitation data and rain gauge data, as well as adopting different methods (i.e., Turc and Thornthwaite). Although intrinsically uncertain, the RaDAR-based precipitation data provided solid results, pointed out by comparing it with water budget obtained by rain gauge data, and especially with experimental literature data. This interdisciplinary work may pave the way for continuous monitoring of aquifer potential recharge at extremely high temporal and spatial resolution.

An Algorithm for Retrieving the 2-D Distribution of Moderate Rain by X-SAR

Synthetic aperture radar (SAR) can detect ground information with high precision, which provides another opportunity for the retrieval of rain. Rainfall intensities in East Asia are mainly moderate. The current retrieval algorithms have high accuracy in rainstorms, but they overestimate the rainfall intensity greatly in moderate rain. Therefore, it is very important to reduce the retrieval error of SAR in moderate rain. After analyzing the scattering model of precipitation, this paper proposes an algorithm for retrieving 2-D moderate rain distribution (MRA). Since the 2-D distribution of rain is related to the vertical and horizontal distributions, MRA combines the empirical regression equation with the directional model of rain rates at different levels to retrieve the vertical distribution of precipitation. Compared with the model-oriented statistical (MOS) algorithm, MRA reduces the root mean square error when retrieving the surface rain rate from 2.6 to 0.1. In addition, based on the high-precision rain parameters retrieved by MRA, the horizontal distribution is retrieved through the likelihood distance. This horizontal distribution retrieval method not only has less amount of calculation but also avoids the difficulties of mathematical analysis.

Limnological Studies of Water Column Properties of Kuntbhoyag Lake, Mandi District Himachal Pradesh India

Lakes play important role in the biochemical and hydrological cycle. The water in lakes is the valuablesource for hydropower, domestic, industrial purpose, drinking water and irrigation etc. The water columnquality properties are monitored during December 2020. To find out the suitable water column propertiesin different locations is an intricate task. The potential of water column properties from different locationsto achieve maximum desirability for different properties of water with the help of the desirability functionhas been reported in this article. However, the level of water quality parameters was found to be more thanthe criteria level in all the intake points. This is due to contaminated surface rain runoff enter into the lake.

Sensitivity study of the impact of CCN size on simulated ground precipitation for deep convection case

A sensitivity study investigated the impact of the mean radius of the aerosol spectrum on surface precipitation using the two-moment bulk microphysical scheme. The numerical model solved the mixing ratios and corresponding number concentrations of the following seven hydrometeors: cloud droplets, raindrops, ice crystals, snow, graupel, frozen raindrops, and hail. Aerosol particles act as cloud condensation nuclei (CCN). The values of the mean radius of CCN varied from 0.01 μm to 1 μm, forming six sensitivity experiments. The mass production of various hydrometeors in the model domain and the amounts of surface rain and hail precipitation were analysed. Increasing the mean radius of the aerosol spectrum leads to an ever-widening of the precipitation area and a consequent increase in the amounts of rain and hail on the ground. The clouds that form in an environment characterized by a larger mean radius move faster and consist of multiple convective cells. In an environment with the smallest mean radius, there is a higher cloud droplet number concentration, which slows the transfer to rain via the autoconversion process. The higher amounts of frozen raindrops in the environment with larger aerosol particles lead to a pronounced source for hailstones, which further grows by accretion of cloud droplets. In such an atmosphere, a stronger melting of frozen raindrops and hail leads to faster conversion to the rain category compared to the cases with smaller aerosol particles.

The Influence of the Diurnal Cycle in Wind Shear and Thermodynamics on Squall Lines in the West African Monsoon

Abstract The West African monsoon has a clear diurnal cycle in boundary layer properties, synoptic flow, and moist convection. A nocturnal low-level jet (LLJ) brings cool, moist air into the continent and we hypothesize that it may support storms by providing vertical wind shear and a source of moisture. We use idealized simulations to investigate how the mean diurnal cycle in temperature and humidity compared with that of the wind shear impacts on mature squall lines. Thermodynamic diurnal changes dominate those of the winds, although when isolated the LLJ wind is favorable for more intense systems. Bulk characteristics of the storms, including in-cloud upward mass flux and—if precipitation evaporation is accounted for—total surface rain rates, correlate well with the system-relative inflow of convectively unstable air and moisture into the storms. Mean updraft speeds and mean rainfall rates over the storms do not correlate as well with system-relative inflows due to variations in storm morphology such as cold pool intensity. We note that storms tend to move near the speed of the African easterly jet and so maximize the inflow of convectively unstable air. Our results explain the observed diurnal cycle in organized moist convection, with the hours from 1800 to 0000 UTC being the most favorable. Storms are more likely to die after this, despite the LLJ supporting them, with the environment becoming more favorable again by midday. Significance Statement Large organized storms dominate rainfall in the West African Sahel, but models struggle to predict them at the correct time of day and the underlying mechanisms that control their timings are not well understood. Using idealized simulations, we show that the temperature and humidity of the late evening are favorable for such storms whereas inflow from the low-level jet supports storms overnight. Storm inflows of available energy and moisture predict upward mass transport and total rainfall rates, whereas the strength of the storm’s cold pool is important for storm structure and intensity. Our results demonstrate how the environmental wind profile (which varies throughout the day) interacts with internal storm dynamics, posing a major challenge to parameterized models.

Study of the effect of cutting modes on output parameters under high-speed steel turn-milling

Introduction. The article elucidates increasing the efficiency of turn-milling of powdered metal high-speed steel products. Turn-milling can be used as an alternative to the traditional turning method. The article describes advantages of the turn-milling method. A review of studies devoted to improving the surface quality of parts when turning by milling is given. The work aims at determining the effect of cutting modes on the surface roughness by the orthogonal turning method through milling powdered high-speed steel with a monolithic cutter.Materials and Methods. Statistical analysis methods based on the creation of a mathematical model for predicting microgeometric deviations of the treated surface were used. An experimental research method was applied to verify the adequacy of the mathematical model. The experiment was planned according to the non-composite design proposed by Box and Behnken. The experiment was carried out on a turning machining center with a driving tool. Powdered highspeed steel BÖHLER S390 MICROCLEAN was used as sample material for the experiment. A monolithic carbide milling cutter served as a cutting tool. During the experiment, the cutting speed, milling width, and feed per tooth varied. The roughness of the treated surface was measured by a contact profilometer.Results. A mathematical model of the formation of surface roughness depending on the processing modes was developed. During the experiments, the effect of cutting speed, tool feed, and radial cutting depth on the roughness of the treated surface was determined. It was established that the dependence of roughness on feed had a linear character over the entire investigated range of cutting modes. In turn, the dependence of roughness on the cutting speed and cutting width had a parabolic character. The results obtained allowed us to achieve the roughness of the treated surface Ra = 1.85 without reducing the processing performance. Discussion andConclusions. The developed mathematical model reflects the impact of cutting modes on the surface roughness when turning high-speed steel with a monolithic cutter. The results of the conducted research can be used to determine the optimal cutting modes that provide a given surface quality in the manufacture of real parts under the production conditions. It is recommended to continue the research with the control of additional output parameters, such as temperature and vibration. Reducing the effect of regenerative self-oscillations on the roughness of the treated surface can be reached through assigning the cutting modes based on the results of a modal analysis of the process system.

Investigation of aerosol effects on a deep convection case in Southeast China with budget analysis of hydrometeor mass and latent heat

It remains an open question which microphysical processes determine the sign of aerosol effects on deep convective rain. This lack of knowledge prevents us from understanding the uncertainties of the aerosol effects on deep convection. We try to answer this question through a cloud-resolving model (CRM) simulation on a summer storm that occurred in Southeast China, by analyzing both column hydrometeor mass and latent heat budget and quantifying the contribution of each microphysical process to the rain variations with aerosol. Our results show that warm-phase microphysical processes have stronger contributions (52% −99%) to the rain variations than ice-phase microphysical processes (1%−48%) when gradually increasing cloud condensation nuclei (CCN) concentration from 125 cm−3 (clean environment) to 16,000 cm−3 (highly polluted environment). Condensation and evaporation of cloud droplets are identified as two crucial microphysical processes, both of which are enhanced with increased aerosol loading. The competition between them (i.e., net condensation) essentially determines the sign of aerosol effects on surface rain. We also explore aerosol effects on updraft velocity from the perspective of buoyancy and latent heat budget, it reveals that the largely enhanced convective updrafts below 7 km are attributed to the increase of condensation heating. While the competition between enhanced condensation heating and suppressed deposition heating restricts the aerosol-induced convective invigoration above 7 km. This study highlights the dominant role of net condensation in the aerosol-imposed invigoration of deep convection under highly polluted environments, suggesting that an explicit treatment of vapor diffusion processes is necessary to simulate aerosol effects on deep convection more accurately.

Multiscale Interactions Contributing to Enhanced Orographic Precipitation in Landfalling Frontal Systems over the Olympic Peninsula

Abstract Orographic precipitation results from complex interactions between terrain, large-scale flow, turbulent motions, and microphysical processes. This study appeals to polarimetric radar data in conjunction with surface-based disdrometer observations, airborne particle probes, and reanalysis data to study these processes and their interactions as observed during the Olympic Mountain Experiment (OLYMPEX). Radar and disdrometer observations from OLYMPEX, which was conducted over the Olympic Peninsula in the winter of 2015, revealed 3 times as much rain fell over elevated sites compared to those along the ocean and coast. Several events were marked by significant water vapor transport and strong onshore flow. Detailed analysis of four cases demonstrated that the warm sector, which previous authors noted to be a period of strong orographic enhancement over the terrain, is associated not only with deeper warm cloud regions, but also deeper cold cloud regions, with the latter supporting the growth of dendritic ice crystals between 4 and 6 km. This dendritic growth promotes enhanced aggregation just above the melting layer, which then seeds the warm cloud layer below, allowing additional drop growth via coalescence. Periods of subsynoptic variability associated with mesoscale boundaries and low-level jets are shown to locally modify both the ice microphysics as well as surface drop-size distributions. This study explores the spatial and temporal variability of precipitation, cloud microphysics, and their relationship over the complex terrain of the Olympic Peninsula. Significance Statement This study appeals to polarimetric radar, aircraft particle probes, disdrometer data, and reanalysis to investigate the complex interactions between large frontal systems, terrain, and microphysical processes contributing to precipitation characteristics at the surface over the Olympic Peninsula. The study finds that the precipitation is a complex function of the synoptic regime, distance inland, and terrain height. Ice microphysical processes aloft act to modulate the surface rain drop size distributions, and are more important in contributing to higher rain accumulations inland during the later phases of the warm sector, particularly over the middle terrain heights (100–500 m).

Vertical structures of abrupt heavy rainfall events over southwest China with complex topography detected by dual‐frequency precipitation radar of global precipitation measurement satellite

AbstractSouthwest China is with complex topography including basins, mountains, hills and plains, where abrupt heavy rainfall events (AHREs) occur frequently and are difficult to quantitatively estimate due to limited ground‐based observations. Using the data of ground rain gauges and GPM dual‐frequency precipitation radar during April to September in 2014–2020, this study investigates vertical structures of AHREs over southwest China. Both mass‐weighted mean diameter (Dm) and reflectivity (Ze) of AHREs increase rapidly in ice‐phase process but slowly in liquid‐phase process. For convective rainfall of AHREs, abundant water vapour and strong atmospheric convective motion cause higher Dm and Ze but lower generalized intercept parameter (dBNw) than those for stratiform rainfall. Moreover, ice‐phase process is active while liquid‐phase process is weak in the mountains, but the situation is opposite in the plains, which results in large‐size and low‐concentration raindrops in the mountains while small‐size and high‐concentration raindrops in the plains. Furthermore, statistical models of vertical profile of reflectivity (VPR) indicate that VPR patterns are affected by surface rain intensity and present different trends around the 0°C level between stratiform and convective rainfalls. In addition, higher rain top height in the mountains is conducive to ice‐phase process while lower terrain height in the plains is favourable for liquid‐phase process. Therefore, the VPR pattern depends on rain type, terrain and rainfall intensity, and its fine model is beneficial for understanding microphysical process of AHREs and improving quantitative precipitation estimation by ground‐based radars.

Characteristics of clouds, precipitation, and latent heat in midlatitude frontal system mixed with dust storm from GPM satellite observations and WRF simulations

A heavy dust storm originating in Mongolia and Inner Mongolia traveled to Northeast China and met a midlatitude frontal system on May 3, 2017. The potential ice nuclei (IN) effects of mineral dust aerosols on the vertical structure of clouds, precipitation, and latent heat (LH) were studied using Global Precipitation Mission (GPM) satellite observations and Weather Research and Forecasting (WRF) model simulations. The WRF simulations correctly captured the main features of the system, and the surface rain rate distribution was positively correlated with data retrieved from the GPM Microwave Imager. Moreover, the correlation coefficient increased from 0.31 to 0.54 with increasing moving average window size. The WRF-simulated rainfall vertical profiles are generally comparable to the GPM Dual-Frequency Precipitation Radar (DPR) observations, particularly in low layers. The joint probability distribution functions of the rain rate at different altitudes from the WRF simulation and GPM observations show high positive correlation coefficients of ~0.80, indicating that the assumptions regarding the raindrop size distribution in the WRF model and DPR retrieval were consistent. Atmospheric circulation analysis and aerosol optical depth observations from the Himawari-8 satellite indicated that the dust storm entered only a narrow strip of the northwest edge of the frontal precipitation system. The WRF simulations showed that in carefully selected areas of heavy dust, dust can enhance the heterogeneous ice nucleation process and increase the cloud ice, snowfall, high-altitude precipitation rate, and LH rate in the upper layers. This effect is significant at temperatures of −15 °C to −38 °C and requires dust number concentrations exceeding 10&lt;sup&gt;6&lt;/sup&gt; m&lt;sup&gt;−&lt;/sup&gt;&lt;sup&gt;3&lt;/sup&gt;. It is important to accurately classify the dusty region in this type of case study. In the selected vertical cross section, the WRF-simulated and DPR-retrieved LH have comparable vertical shapes and amplitudes. Both results reflect the structure of the tilted frontal surface, with positive LH above it and negative LH below it. The simulated area-averaged LH profiles show positive heating in the entire column, which is a convective-dominated region, and this feature is not significantly affected by dust. DPR-based LH profiles show stratiform-dominated or convective-dominated shapes, depending on the DPR retrieval product.

A Study of Sea Surface Rain Identification Based on HY-2A Scatterometer

Rain affects the wind measurement accuracy of the Ku-band spaceborne scatterometer. In order to improve the quality of the retrieved wind field, it is necessary to identify and flag rain-contaminated data. In this study, an HY-2A scatterometer is used to study rain identification. In addition to the conventional parameters, such as the retrieved wind speed, the wind direction relative to the along-track direction, and the normalized beam difference, the experiment expands the mean deviation of the backscattering coefficient, the beam difference between fore and aft, and the node number of the wind vector cell (WVC) as the sensitive parameters according to the microwave scattering characteristics of rain and the actual measurement situation of the HY-2A. Furthermore, a rain identification model for HY2 (HY2RRM) with the K-Nearest Neighborhood (KNN) algorithm was built. After several tests, the accuracy of the selected HY2RRM approach is found to about 88%, and about 70% of rain-contaminated data can be accurately identified. The research results are helpful for better understanding the characteristics of microwave backscattering and provide a possible way to further improve the wind field retrieval accuracy of the HY-2A scatterometer and other Ku-band scatterometers.

Use of PET Granules for Improving a Surface Runoff Treatment

Pollution of surface and ground waters by surface (rain and melt) waste water is a big problem for many countries of the world. In addition to anthropogenic factors leading to the pollution of surface runoff, one should add runoff, which is formed after extinguishing fires of various scales and territories. As a result of extinguishing fires, a large amount of pollutants enters surface wastewater, which creates an additional load on soils, groundwater aquifers and water bodies. The paper proposes a wastewater treatment method using PET granules and polyurethane foam granules as a filtering layer. The use of PET packaging waste for the purification of rain and melt wastewater allows to reduce the anthropogenic load on the environment and to increase the use of plastic waste.

Water Absorbing Pavement by Using Porous Concrete

Water Absorbing pavement is a technique in Pavement construction. This technique we can find a solution for the low ground water level, effective management of rain water runoff, Agricultural problems, etc. Porous concrete can be introduced in low traffic volume areas, walk ways, sub base for concrete pavements, inter locking material etc. Porous concrete material have the ability to allow water to flow through itself to recharge ground water level and minimize surface rain water runoff. This property of porous concrete reviews its applications and engineering properties, including environmental benefits, strength. By replacing a part of cement with conplast SP430, then it results the more strength to the concrete. Hence it take acts as an eco-friendly paving material. Porous concrete is a special type of concrete, which consists of cement, coarse aggregates, water and if required, mixtures and other cement materials. As there are no fine aggregates used in the concrete matrix, the void content is more which allows the rain water to flow through its body. So the porous concrete is also called as Permeable concrete and Previous concrete.

A New Data Fusion Neural Network Scheme for Rainfall Retrieval Using Passive Microwave and Visible/Infrared Satellite Data

A new data fusion technique based on Artificial Neural Networks (ANN) for the design of a rainfall retrieval algorithm is presented. The use of both VIS/IR (VISible and InfraRed) data from GEO (Geostationary Earth Orbit) satellite and of passive microwave data from LEO (Low Earth Orbit) satellite can take advantage of both types of sensors reducing their limitations. The technique can reconstruct the surface rain field with the MSG-SEVIRI (Meteosat Second Generation–Spinning Enhanced Visible Infrared Imager) spatial and temporal resolution, which means 3 km at the sub satellite point and 5 km at mid-latitudes, every 15 min, respectively. Rainfall estimations are also compared with H-SAF (Hydrology Satellite Application Facility) PR-OBS3A operational product showing better performance both on the identification of rainy areas and on the retrieval of the amount of precipitation. In particular, in the considered test cases, results report an improvement in average of 83% in terms of probability of rainy areas detection, of 45% in terms of false alarm rate, and of 47% in terms of root mean square error in the retrieval of the amount of precipitation.

Evaluation of Microphysics Schemes in Tropical Cyclones Using Polarimetric Radar Observations: Convective Precipitation in an Outer Rainband

AbstractCloud microphysics significantly impact tropical cyclone precipitation. A prior polarimetric radar observational study by the authors revealed the ice-phase microphysical processes as the dominant microphysics mechanisms responsible for the heavy precipitation in the outer rainband of Typhoon Nida (2016). To assess the model performance regarding microphysics, three double-moment microphysics schemes (i.e., Thompson, Morrison, and WDM6) are evaluated by performing a set of simulations of the same case. While these simulations capture the outer rainband’s general structure, microphysics in the outer rainbands are strikingly different from the observations. This discrepancy is primarily attributed to different microphysics parameterizations in these schemes, rather than the differences in large-scale environments due to cloud–environment interactions. An interesting finding in this study is that the surface rain rate or liquid water content is inversely proportional to the simulated mean raindrop sizes. The mass-weighted raindrop diameters are overestimated in the Morrison and Thompson schemes and underestimated in the WDM6 scheme, while the former two schemes produce lower liquid water content than WDM6. Compared with the observed ice water content based on a new polarimetric radar retrieval method, the ice water content above the environmental 0°C level in all simulations is highly underestimated, especially at heights above 12 km MSL where large concentrations of small ice particles are typically prevalent. This finding suggests that the improper treatment of ice-phase processes is potentially an important error source in these microphysics schemes. Another error source identified in the WDM6 scheme is overactive warm-rain processes that produce excessive concentrations of smaller raindrops.