Precipitation Analysis Research Articles

Combined assimilation of hourly rainfall data and every 10-min AHI radiance with WRF 4DVar for the short-range heavy rainfall forecast in Eastern China

Rainfall observations and geostationary satellite water vapor radiances account for complementary humidity information over rainy areas and large-scale environments, respectively. This study investigates the simultaneous assimilation of China Hourly Merged Precipitation Analysis (CHMPA) data and clear-sky water vapor radiances provided by the Himawari-8 Advanced Himawari Imager (AHI) with Four-Dimensional Variational (4DVar) data assimilation method using Weather Research and Forecasting (WRF) model with an hourly rapid-update cycling data assimilation configuration. The rapid-update 4DVar assimilation is configured as 10-min interval for AHI radiances and 1-h interval for CHMPA rainfall data in a same 1-h assimilation time window. Generally positive impacts from assimilating CHMPA rainfall and AHI water vapor radiance observations are achieved for the 12-h short-term precipitation forecast. Error reductions are found after assimilating CHMPA rainfall and AHI water vapor radiance observations for both analyses and forecasts when compared to ERA5 reanalysis. It is found that combined assimilation of CHMPA rainfall and AHI water vapor radiance data has clearly positive impacts on heavy rainfall forecasts. A heavy rainfall case that occurred in Jiangsu Province on 28 June 2020 is examined in details. The combined assimilation of infrared radiances from AHI water vapor channels together with CHMPA rainfall data improves the vertical and horizontal transport of humidity conditions, which better adjusts the humidity distribution. The over-estimation of rainfall forecast caused by the assimilation of CHMPA is alleviated. This result can provide reference for quantitative precipitation forecasts of regional numerical weather model.

Dual action of a distinctive colloidal 3-(Benzimidazole-2-yl)-2-hydroxybenzaldehyde grafted chitosan support for the continual detection ability for Hg (II) in aqueous environ and inherent emission-induced live cell imaging

In this research work, an interesting sugar based fluorescent materials has been successfully developed to detect metal ions (Hg2+) in aqueous solution. The prepared colloid, 3-(benzimidazole-2-yl)-2-hydroxy benzaldehyde/chitosan (ChI) has significant characteristics as greener and eco-friendly material. ChI has found for switching of proton transfer between enol-imine and keto-enamine forms of ChI through excited-state intramolecular proton transfer (ESIPT) mechanism. The internal chemical-bonding and functionality of ChI are confirmed through FTIR, UV–Vis, fluorescence, SEM, TEM, DLS etc. ChI shows its fluorescence-quenching, selectivity, scavenging and chelating capabilities for Hg2+ ions in the presence of other cations in aqueous solution. Spectral and XRD analysis have established the remarkable continual and consistent detection of Hg2+ in aqueous system with a limit of detection of 0.204 nM. The strong chelating agent EDTA is used to regain of fluorescence of ChI in support of labile chelation ability of ChI and to show reversibility for continual detection of Hg2+ due to the strong EDTA/Hg2+ complexation. Scavenging ability is investigated using Na2S solution followed by the XRD analysis of precipitate appeared. Also, ChI shows its efficiency for the fluorescence cell imaging in live HADF cells with negligible cytotoxicity. Convincingly, ChI has processed as materials with very significant addition and advancement for its multimodal and eco-friendly behavior in current material development research.

Bias-Corrected CMIP5 Projections for Climate Change and Assessments of Impact on Malaria in Senegal under the VECTRI Model.

On the climate-health issue, studies have already attempted to understand the influence of climate change on the transmission of malaria. Extreme weather events such as floods, droughts, or heat waves can alter the course and distribution of malaria. This study aims to understand the impact of future climate change on malaria transmission using, for the first time in Senegal, the ICTP's community-based vector-borne disease model, TRIeste (VECTRI). This biological model is a dynamic mathematical model for the study of malaria transmission that considers the impact of climate and population variability. A new approach for VECTRI input parameters was also used. A bias correction technique, the cumulative distribution function transform (CDF-t) method, was applied to climate simulations to remove systematic biases in the Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models (GCMs) that could alter impact predictions. Beforehand, we use reference data for validation such as CPC global unified gauge-based analysis of daily precipitation (CPC for Climate Prediction Center), ERA5-land reanalysis, Climate Hazards InfraRed Precipitation with Station data (CHIRPS), and African Rainfall Climatology 2.0 (ARC2). The results were analyzed for two CMIP5 scenarios for the different time periods: assessment: 1983-2005; near future: 2006-2028; medium term: 2030-2052; and far future: 2077-2099). The validation results show that the models reproduce the annual cycle well. Except for the IPSL-CM5B model, which gives a peak in August, all the other models (ACCESS1-3, CanESM2, CSIRO, CMCC-CM, CMCC-CMS, CNRM-CM5, GFDL-CM3, GFDL-ESM2G, GFDL-ESM2M, inmcm4, and IPSL-CM5B) agree with the validation data on a maximum peak in September with a period of strong transmission in August-October. With spatial variation, the CMIP5 model simulations show more of a difference in the number of malaria cases between the south and the north. Malaria transmission is much higher in the south than in the north. However, the results predicted by the models on the occurrence of malaria by 2100 show differences between the RCP8.5 scenario, considered a high emission scenario, and the RCP4.5 scenario, considered an intermediate mitigation scenario. The CanESM2, CMCC-CM, CMCC-CMS, inmcm4, and IPSL-CM5B models predict decreases with the RCP4.5 scenario. However, ACCESS1-3, CSIRO, NRCM-CM5, GFDL-CM3, GFDL-ESM2G, and GFDL-ESM2M predict increases in malaria under all scenarios (RCP4.5 and RCP8.5). The projected decrease in malaria in the future with these models is much more visible in the RCP8.5 scenario. The results of this study are of paramount importance in the climate-health field. These results will assist in decision-making and will allow for the establishment of preventive surveillance systems for local climate-sensitive diseases, including malaria, in the targeted regions of Senegal.

Urban Climate and the Homeless Population: Exposure, Impacts, and Strategies

Background: This article approaches how the urban climate has become a risk factor for the homeless population. Methods: The empirical investigation draws on Rio de Janeiro, Brazil, considering the impacts of cold, heat, and rainfall events on these individuals. Precipitation and surface temperature analyses were performed to identify the urban climate processes to which the homeless are exposed. Results: Results indicate that these individuals tend to prioritize commercial areas for settling down, overlooking their susceptibility to extreme weather events. Conclusion: Downtown Rio de Janeiro concentrates the highest temperature and precipitation thresholds, increasing homeless exposure to urban climate effects as the group is also concentrated in the area. Their exposure intensifies morbidities and comorbidities and will likely be aggravated by increased extreme events due to climate change.

Effect of pH and Precipitations on Copper–Molybdenum Rougher Flotation in Seawater

Effect of pH and precipitations on copper–molybdenum ore rougher flotation has been investigated in seawater with flotation experiments followed by precipitation estimation with thermodynamic calculations, turbidity measurements and XRD analysis. Results of flotation experiments in seawater indicated that the effect of pH on copper and molybdenum flotation maximum recovery seems limited. On the other hand, pH drastically influences copper and molybdenum flotation kinetic constant, it decreased a lot with increasing pH, and results of pH 8.5 and 9.0 is quite similar. From thermodynamic calculation, precipitation effect on seawater less than pH 9 seems limited since CaCO3 and Mg(OH)2 does not exist on this pH region. To estimate precipitation on pH in seawater, turbidity measurements were carried out with controlled pH and results indicated even pH is less than 9, noticeable turbidity can be seen. To confirm precipitation in seawater, precipitation was collected from controlled pH seawater solution. XRD analysis of precipitation indicated that obtained precipitation at pH 8.7 is CaCO3, CaSO4 and Mg(OH)2. This result is not same as the result of thermodynamic calculation and it might be due to the activity coefficient and ionic strength effect. Although flotation kinetic is influenced with turbidity, turbidity influence on maximum recovery is limited. Effect of kinetic might be due to that precipitation exist as suspension and it prevent bubble and mineral attachments. Small effect of precipitation on maximum recovery might be due to exist of few precipitation on the surface of copper and molybdenum mineral since most of mineral in rougher flotation is gangue minerals and also most of precipitations might be on gangue minerals. These results indicated that seawater flotation have to take into account of precipitation effect more for flotation kinetic than maximum flotation recovery.

Evaluation and Applicability Analysis of GPM Satellite Precipitation over Mainland China

This study aims to systematically evaluate the accuracy and applicability of GPM satellite precipitation products (IMERG-E, IMERG-L, and IMERG-F) with varying time lags at different spatial and temporal scales over mainland China. We use quantitative statistical indicators, including correlation coefficient (CC), root mean square error (RMSE), mean absolute error (MAE), mean daily precipitation, probability of detection (POD), false alarm rate (FAR), bias, and equitable threat score (ETS), based on observations from 2419 national gauge sites. The results show that GPM satellite precipitation products perform well in eastern and southern humid regions of China, with relatively poorer performance in western and northern regions in terms of spatial distribution. It reflects the sensitivity of GPM precipitation retrieval algorithm to climate and precipitation type, topography, density, and quality of ground observation across different latitudes. Despite the design of GPM for different forms of precipitation, IMERG products perform the best in summer and the worst in winter, indicating that estimating snowfalls via satellite is still challenging. In terms of precipitation intensity, IMERG products significantly improve performance for light and no rain (POD ≥ 0.7), but errors gradually increase for moderate, heavy, and torrential rain, due to the saturation tendency of satellite echoes. Overall, we comprehensively evaluate the IMERG products, revealing the distinct characteristics at various spatial–temporal scales focusing on rainfall accumulations over mainland China. This study provides an important reference for other similar satellite-based precipitation products. It also helps the parameter optimization of hydrological modelling, especially under extreme precipitation conditions, to enhance the accuracy of flood simulation.

Assessing CFSR climate data for rainfall-runoff modeling over an ungauged basin between Iraq and Iran

In most developing countries, networks of gauge observations are frequently sparse and may have significant spatial and temporal gaps in the meteorological records. Reanalysis products are extensively used as alternative climate inputs for watershed modeling that provide continuous data worldwide. However, the direct utilization of such products is highly doubtful at different basin scales. This article aims to evaluate the accuracy of the Climate Forecast System Reanalysis (CFSR) product for streamflow simulation using the Soil and Water Assessment Tool (SWAT) model in the northeastern part of the Little Zab River Basin (LZRB), a mountainous basin between Iraq and Iran. The quality of CFSR was assessed from two viewpoints: (1) the precipitation aspect, an analysis of the CFSR precipitation compared to observational meteorological data (OMD) from 2004 to 2013 on a daily time scale, and (2) the hydrology aspect, a comparison of the SWAT model performance based on OMD (scenario I) and the CFSR product (scenario II) for monthly streamflow simulations. Results showed that the CFSR precipitation had a satisfactory correlation with rain gauge data ranging from 0.55 to 0.81. The performance of OMD in SWAT-based streamflow simulation achieved a ‘very good’ rating in calibration (2006–2010) and validation (2011–2013). Meanwhile, the CFSR-based model demonstrated a ‘very good’ hydrologic prediction skill in calibration. In contrast, CFSR revealed a lower performance in the validation period as it considerably overestimated base and peak flows in LZRB. Nevertheless, model uncertainty analysis after calibration showed that more than 88% of measured streamflow values at the basin outlet were bracketed within the 95 percent prediction uncertainty (95PPU) band for OMD and CFSR. These findings revealed that the CFSR product, after proper bias correction, could be a reliable alternative climate input for hydrologic modeling and climatological studies in semi-arid basins where gauge data is limited.

Spatial-Temporal Changes of Abarkuh Playa Landform from Sentinel-1 Time Series Data

Playas, as the flattest landforms in semiarid and arid regions, are extremely sensitive to climate changes, such as changes in the hydrologic regime of the landscape. The changes in these landforms due to irrigation, anthropogenic activities, and climate change could be a source of disasters. In this study, we explored the spatial-temporal changes of the Abarkuh Playa in Central Iran using the time series of the Sentinel-1 backscatter dataset in the three scales. Our results showed that the western area of the Abarkuh Playa has been changed to other landforms with different characteristics, which is clear from all backscatter maps. The spatial-temporal analysis of the time series of backscatter data using the independent component analysis and time series of precipitation revealed that the backscatter variations were associated with direct rainfall across the playa and the surface was reacting to changes in the soil moisture content. The results of the power scale showed that the boundary of the playa could successfully be recognized as the oscillating pattern from other landforms in the study area. Moreover, the spatial-temporal analysis of backscatter in the power scale showed that different polarizations could reveal different patterns of surface changes for the playa.

Reconsidering the role of albumin towards amorphous calcium phosphate-based calciprotein particles formation and stability from a physico-chemical perspective

The formation of calciprotein particles (CPPs) in serum is a physiological phenomenon fundamental to prevent the rise of ectopic calcifications. CPPs are colloidal hybrid particles made of amorphous calcium phosphate stabilized by a protein, fetuin-A. Since albumin is the most abundant protein present in serum, we aimed at understanding if it plays a synergic action together with fetuin-A towards CPPs formation and stability.CPPs were prepared using a constant fetuin-A concentration (5 µM) and different concentrations of albumin (0–606 µM). The stability of CPPs, their crystallization and sedimentation were followed in situ by combining turbidimetry, precipitation analysis and dynamic light scattering. The morphology was investigated by scanning electron microscopy and cryo-transmission electron microscopy, while crystallinity was inspected by infrared spectroscopy. The effect of albumin on the amount of formed CPPs was also studied, as well as the amount of protein adsorbed on CPPs.We found that albumin is not able to prolong the lifetime of the amorphous phase, but it is very effective in delaying the sedimentation of CPPs after crystallization. Albumin also significantly decreases the amount and size of CPPs when present in their synthetic medium, likely playing a fundamental role in our organism together with fetuin-A towards the stabilization of CPPs.

Atmospheric deposition mapping of particulate elements in the Canadian Athabasca oil sands region

This study used a deposition modeling framework to generate gridded dry, wet, and total (dry + wet) deposition fluxes of 27 particulate elements over the Canadian Athabasca oil sands region and its surrounding areas for the years 2016–2017. The framework employed the element concentrations from the CALPUFF dispersion model outputs that were bias-corrected against measured concentrations, modeled dry deposition velocities, precipitation analysis data, and literature values of element-specific fine mode fractions and scavenging ratios by rain and snow. The annual total deposition (mg/m2/year) of all elements (EM) across the domain ranged from 4.49 to 5450 and the mean and median deposition were 60.9 and 31.0, respectively. Total EM deposition decreased rapidly within a short distance from the oil sands mining area. Annual mean total deposition (mg/m2/year) of EM was 717 in Zone 1 (within 30 km from a reference point, representing the center of the oil sands mining area), 115 in Zone 2 (30–100 km from the reference point), and 35.4 in Zone 3 (beyond 100 km from the reference point). The deposition of individual elements was primarily governed by their respective concentrations and among all elements the annual mean total deposition (μg/m2/year) over the domain varied five orders of magnitude ranging from 0.758 (Ag) to 20,000 (Si). Annual mean dry and wet deposition (mg/m2/year) of EM over the domain were 15.7 and 45.2, respectively. Aside from S, which has relatively lower precipitation scavenging efficiencies, wet deposition was the dominant deposition type in the region contributing from 51% (Pb) to 86% (Ca) of the respective total deposition. Total EM deposition over the domain in the warm season (66.2 mg/m2/year) was slightly higher than that in the cold season (55.6 mg/m2/year). Deposition of individual elements in Zone 1 were generally lower than their deposition at other sites across North America.

Trend analysis and drought evaluation: A case study of Sirnak

Water is necessary for sustaining life for all living things. Therefore, it is vital to evaluate thedrought and trend analysis. A total of 276 time series were evaluated to assess drought and determine thetrend analysis. In this study, meteorological drought analysis and trend analysis were conducted for Şırnakprovince, located in the Northeastern Anatolia region, monthly and yearly time series using theStandardized Precipitation Index (SPI) and linear trend analysis. Meteorological data (temperature andprecipitation) from Şırnak province between 2000-2022 were utilized. The results showed that the regionhas different drought and wet types. Although there were periods of severe drought, normal drought levelswere more observed. The wet and dry periods were identified, and the results were presented graphically.Trend analysis of temperature and precipitation was determined. As a result, the results can contribute tothe water resources planning management for the region.

Climate Variability and Trends in Imotski, Croatia: An Analysis of Temperature and Precipitation

This paper examines the long-term changes in temperature and precipitation in the karst region of Imotski, Croatia, which is of particular interest due to its abundance of karst phenomena. This study analyses temperatures and precipitation on monthly and annual scales at two climatological stations in the region, Imotski and Ričice. Linear regression, the Theil–Sen estimator (β), and the Mann–Kendall test were used to determine the trends and statistical significance. The homogeneity of the data was checked using the Standard Normal Homogeneity Test (SNHT), and the F-test and t-test were used to test the significance of the mean shift between the two subseries. Additionally, the coefficient of variability, standardized rainfall anomaly, and precipitation concentration index were employed to analyze the precipitation variability. The study found a statistically significant (p < 0.05) upward trend in the mean (β = 0.0437) and maximum (β = 0.0590) annual air temperature at the Imotski station and the mean (β = 0.0387) annual temperature at the Ričice station. The SNHT test showed a statistically significant (p < 0.05) shift in the mean annual temperatures after 2007 and maximum annual temperatures after 1998 at the Imotski station. Similarly, a statistically significant (p < 0.05) shift in the mean annual temperatures after 2011 and the maximum annual temperatures after 1998 was found at the Ričice station. A seasonal distribution of precipitation is observed at both the Ričice and Imotski stations, with a downward trend (β = −2.7693) at Ričice and an upward trend (β = 6.0575) at Imotski; however, neither trend is statistically significant (p > 0.05). An increase in the intensity of dry periods and the occurrence of extreme events was also noted. The climatological analysis, conducted for the first time in this area, is a crucial step toward understanding local climate patterns and making informed decisions toward sustainable development and adaptation strategies.

Trend analysis of precipitation using innovative approaches in northwestern Turkey

Precipitation is highly sensitive to climate change, and monitoring its trends over time is essential for understanding the effects of global warming on the Earth's water cycle. This study investigates the effects of climate change on monthly precipitation in the Susurluk Basin located in northwestern Turkey, using innovative trend analysis methods. Innovative Polygon Trend Analysis (IPTA) using star graphics and Improved Visualization for Innovative Trend Analysis (IV-ITA) techniques were used to analyze precipitation data from nine stations in the basin over 50 years (1970–2019), and the findings were compared to classical Mann-Kendall (MK) results. According to the trend analysis results, the MK method detected significant trends in only two months in the decreasing direction. In these decreasing trends observed at Simav and Keles stations in November, z values were calculated as −2.38 and −2.05, respectively. IPTA method detected increasing trends in 54 months and decreasing trends in 40 months; this means there is a change of more than 5% between two half series. The IV-ITA method indicated an increase of more than 40% in the low values for January, March, August, and September. In addition, there was an increasing trend of more than 40% in the high values observed in September at all stations. It was observed that mean precipitation heights increased from September to December and then decreased throughout the basin. It is predicted that decreases in precipitation during dry seasons may put intense pressure on agricultural water use and affect water quality. In addition, the increase in precipitation in spring months may increase flood events. It was determined that graphical innovative trend analysis methods are more effective in trend identification than MK, and these methods' results have much higher visual inspection and linguistic interpretation possibilities. Innovative methods allow for more flexible and in-depth analysis using different statistical parameters.

Phytochemistry and biological activities of latex from Schubertia grandiflora Mart. (Apocynaceae)

Schubertia grandiflora is a plant species that produces latex from roots to flowers. This study aimed to evaluate the latex of S. grandiflora on qualitative phytochemical analysis and effects of quantitative biological activities. Latex was collected from logs. Phytochemical analysis of precipitation and colorimetry were carried out for several groups of phytogroups. Antifungal activity was performed on Sclerotinia sclerotiorum, Colletotrichum acutatum and C. gloeosporioides, cytotoxic activity on Artemia salina, antioxidant activity on DPPH free radical and determination of inhibition on acetylcholinesterase. The latex proved to be rich in phytochemical groups, inhibition capacity of S. sclerotiorum with 64% and for C. gloeosporioides of 30%, low rate of cytotoxicity with 25% in 1000 µg mL-1, reduction of DPPH free radical of 67% and AChE inhibition of 86%. Schubertia grandiflora latex proved to be a potential natural phytochemical agent for diverse biological activities through this study.

Examination of Measured to Predicted Hydraulic Properties for Low Impact Development Substrates

To counter the impacts of climate change and urbanization, engineers have developed ingenious solutions to reduce flooding and capture stormwater contaminants through the use of Low Impact Developments (LIDs). The soil is generally considered to be completely saturated when designing for the LIDs. However, this may not always be an accurate or realistic approach, as the soil could be variably unsaturated leading to inaccurate designs. To analyse the flow under variably unsaturated conditions, Richards’ equation can be used. To solve the Richards’ equation, two nonlinear hydraulic properties, namely soil water characteristic curve (SWCC) and the unsaturated hydraulic conductivity function are required. Laboratory and field measurements of unsaturated hydraulic properties are cumbersome, expensive and time- consuming. Pedotransfer functions (PTFs) estimate soil hydraulic properties using routinely measured soil properties. This paper presents a comparison between the direct measurement obtained through experimental procedures and the use of PTFs to estimate soil hydraulic properties for two green roof and three bioretention soil medias. Comparison between the measured and estimated soil hydraulic properties was accomplished using two different approaches. Statistical analyses and visual comparisons were used to compare the measured and estimated soil hydraulic properties. Additionally, numerical modelling to predict the water balance at the ground surface was conducted using the measured and estimated soil hydraulic properties. In some instances, the use of predicted hydraulic properties resulted in overestimation of the cumulative net infiltration of as much as 60 % for the green roof substrate, but was considered negligible for the bioretention substrate. Design performance criteria for green roof and bioretention facilities were examined using the measured and estimated soil hydraulic properties under extreme precipitation analysis. Results indicate that there is a high level of uncertainty when using PTFs for LID materials. A percent difference between the measured and predicted properties for the green roof peak time delay under a 2-year storm can be as much as 300%. For the bioretention design criteria of a 25-year storm, the surface runoff was overestimated by 14.7 cm and by 100% for the ponding time percent difference.

Assessment of Temperature, Precipitation, and Snow Cover at Different Altitudes of the Varzob River Basin in Tajikistan

The analysis of precipitation, snow cover, and temperature based on measured data is important for many applications in hydrology, meteorology, climatology, disaster management, and human activities. In this study, we used long-term historical datasets from the Varzob River Basin (VRB) in Tajikistan to evaluate the trend and magnitudinal changes in temperature, precipitation, and snow cover area in the Anzob (upstream), Maykhura (midstream), and Hushyori (downstream) regions of the VRB using the original Mann–Kendall test, modified Mann–Kendall test, Sen’s slope test, and Pettitt test. The results revealed a decreasing trend in the mean monthly air temperature at Anzob station in the upstream region for all months except January, February, and December between 1960 and 2018 and 1991 to 2018. In each of the three regions, the mean annual temperature indicated a clear upward trend. Seasonal precipitation indicated a large increasing trend in January and February at the Anzob station from 1960 to 2018, but a significant downward trend in April in the upstream, midstream, and downstream regions between 1960 and 1990 and from 1991 to and 2018. In the VRB, almost all stations exhibited a downward trend in annual precipitation across all periods, whereas the upstream region showed a non-significant upward trend between 1960 and 1990. The monthly analysis of snow cover in the VRB based on ground data showed that the maximum increase in snow cover occurs in April at the Anzob station (178 cm) and in March at Maykhura (138 cm) and Hushyori stations (54 cm). The Mann–Kendall test, based on MODIS data, revealed that the monthly snow cover in the VRB increased in April and July while a decrease was recorded in February, September, November, and December from 2001 to 2022. The trend’s stable pattern was observed in March, May, August, and October.

Верификация детерминистского и вероятностного радиолокационного наукастинга осадков в теплый и холодный периоды года на Европейской территории России

Comparative quality analysis of ensemble radar precipitation nowcasting based on test results for the warm (May–September 2020) and cold (November 2021–March 2022) seasons are presented. Composite precipitation intensity fields obtained from radar observations were used as control data for verification. In both periods, a slight but systematic advantage of forecasts of the mean ensemble field was revealed, which indicates the expediency of using ensembles of even a small volume. For all the skill scores used (except for the frequency bias), forecasts in the cold season turn out to be better than forecasts in the warm season, however, the sample sizes for verification in the cold season may be significantly lower than the corresponding sample sizes in the warm season. The problems of comparative quality analysis are discussed, which are caused, in particular, by the loss of spatial connectivity of the composite field during the cold season. Keywords: ensemble nowcasting of meteorological fields, radar precipitation estimates, composite precipitation field, point and spatial field forecast verification

Event‐based extreme precipitation variability analysis over a part of the Hindu Kush Himalayan region

AbstractExtreme precipitation is a primary driver of flood hazards causing damage to humans and infrastructure. Analysis of extreme precipitation without considering temporally compounding events underestimates the severity of the hazard. Especially mountainous regions such as the Hindu Kush Himalayan region are highly vulnerable to multiday extreme precipitation events. However, analysis of such events and their time distribution patterns are still unknown, and a comprehensive assessment is needed. To this, the concept of event‐based extreme precipitation, which accounts for the preceding and succeeding precipitation, is employed for the Upper Indus basin using three reference gridded datasets, namely, Indian Meteorological Department (IMD), Multi‐Source Weighted Ensemble Precipitation (MSWEP) and Himalayan Adaption, Water and Resilience (HI‐AWARE). Four different types of time distribution patterns were identified based on the occurrence of extreme precipitation during an event. We identified that the time distribution pattern with the peak on the right side is predominant among the four types. Subsequently, trend analysis on the characteristics, namely amount, frequency, duration and concentration ratio for all four events, display negative trends with IMD and MSWEP datasets, whereas HI‐AWARE displays positive trends in the northwestern part of the catchment. Further, the 100‐year return level of the amount of multiday extreme precipitation is computed along with the traditional method of single‐day extremes considering nonstationarity. The differences between the return values obtained using the traditional method and the event‐based extreme precipitation concept were distinct and substantial (>50 mm for three datasets). The findings clearly show that the analysis of multiday events is much more essential than single‐day extreme events, particularly for events like floods. Moreover, the results of the study were found to be conflicting among reference datasets, demonstrating the importance of identifying the suitability of reference datasets in extreme event analysis.

A comparative analysis of merging strategies for satellite precipitation estimates and ground observations over Chinese mainland

Satellite precipitation estimates are attractive for providing spatially continuous precipitation measurement on the global scale, but improvements in accuracy are still needed relative to the point-scale gauge observations. In this study, two integration frameworks named Geographical Differential Analysis (GDA) and Geographical Ratio Analysis (GRA) combined with two interpolation techniques named Ordinary Kriging (OK) and Inverse Distance Weighting (IDW) were adopted to merge the satellite precipitation with ground-based observations. The Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) research product was merged with the ground rain gauges derived from CGDPA (China Gauge-based Daily Precipitation Analysis) at a monthly scale over the Chinese mainland from 2011 to 2015, and the merged precipitation products were evaluated by 10-fold cross-validation. Results showed that the merged precipitation products based on the GDA integration framework had significant improvements relative to the original TMPA. Moreover, the method based on GDA combined with Ordinary Kriging (GDA-OK) delivered better performances compared to the GDA-IDW (method based on GDA combined with Inverse Distance Weighting) since the OK considers the global spatial correlation. However, the GRA-based merged precipitation products had systematic underestimations over Chinese mainland during all seasons and were not recommended for satellite-gauge precipitation merging over the large spatial scale of Chinese mainland. In addition, we found that the OK is quite sensitive to the density gauge network, the shrinkage of the number of rain gauges may result in great uncertainties and errors in the OK interpolation technique.

Optical coherence tomography and digital image processing for scaling and Co-precipitation investigation on reverse osmosis membrane

Scaling known as the precipitation of inorganic salts is a main concern in the reverse osmosis (RO) process due to its effects on the process performance and life-time of membranes. Although single salt precipitation has been continuously studied, the co-precipitation of salts is rarely investigated due to its complexity, especially under process hydrodynamic conditions. Recently, optical coherence tomography (OCT) has been adopted as an in situ and rapid technique for monitoring the fouling in membrane processes. This study aims to develop an approach using OCT and digital image processing for qualitative and quantitative analysis of single salt precipitation and co-precipitation on RO membrane under hydrodynamic conditions. The effects of supersaturation, sodium chloride (NaCl), flow rate, and applied pressure are investigated. The developed approach enables the detection of crystal growth under the OCT. The morphology of precipitated salt, i.e CaSO4, including crystal shape and size obtained from OCT acquisition, agrees with the images from a scanning electron microscope (SEM). The growth of each crystal in co-precipitation of CaSO4 and CaCO3 is well detected in appearance time and growth pattern. This is beneficial to differentiate crystal morphology in the co-precipitation system. The quantitative surface coverage proportion and total volume are in well correlated the changes of RO performance parameters of permeate flux, conductivity (feed, concentrate, and permeate), and Ca2+ concentrate profile by time, which allows the scaling progress to be directly evaluated over time. This study reveals the high potential of combining OCT acquisition and digital image processing for direct observations and studying single salt and co-precipitation under RO hydrodynamic conditions, which can be extended for another type of composite fouling.