Total Amount Of Precipitation Research Articles

Responses of terrestrial ecosystem productivity and community structure to intra-annual precipitation patterns: A meta-analysis.

The productivity and community structures of terrestrial ecosystems are regulated by total precipitation amount and intra-annual precipitation patterns, which have been altered by climate change. The timing and sizes of precipitation events are the two key factors of intra-annual precipitation patterns and potentially drive ecosystem function by influencing soil moisture. However, the generalizable patterns of how intra-annual precipitation patterns affect the productivity and community structures of ecosystems remain unclear. We synthesized 633 observations from 17 studies and conducted a global meta-analysis to investigate the influences of intra-annual precipitation patterns on the productivity and community structures of terrestrial ecosystems. By classifying intra-annual precipitation patterns, we also assess the importance of the magnitude and timing of precipitation events on plant productivity. Our results showed that the intra-annual precipitation patterns decreased diversity by 6.3% but increased belowground net primary productivity, richness, and relative abundance by 16.8%, 10.5%, and 45.0%, respectively. Notably, we found that the timing uniformity of precipitation events was more important for plant productivity, while the plant community structure benefited from the increased precipitation variability. In addition, the relationship between plant productivity and community structure and soil moisture dynamic response was more consistent with the nonlinear model. The patterns of the responses of plant productivity and community structure to altered intra-annual precipitation patterns were revealed, and the importance of the timing uniformity of precipitation events to the functioning of production systems was highlighted, which is essential to enhancing understanding of the structures and functions of ecosystems subjected to altered precipitation patterns and predicting their changes.

Response of Erosive Precipitation to Vegetation Restoration and Its Effect on Soil and Water Conservation Over China's Loess Plateau

AbstractLarge‐scale vegetation restoration profoundly affects ecohydrological and hydrometeorological processes with consequent effects on soil and water conservation. However, it is still unclear how revegetation affects the joint relationship between streamflow and sediment yield from the land‐atmosphere interactions perspective. In this study, we combine in situ hydro‐meteorological observations, satellite observed land surface characteristics, and coupled land‐atmosphere model simulations to address this knowledge gap through a case study focusing on the Loess Plateau, where a megaproject of revegetation has been implemented since 2000. We find that historical annual streamflow and sediment yield have decreased over the Loess Plateau and 12 main revegetated basins, mainly due to enhanced canopy transpiration and soil conservation functions of revegetation. However, the magnitude of sediment yield reduction is much higher than that of streamflow for both mainstream and tributaries of the Yellow River. Specifically, the mean decreasing rate of sediment yield is 2.91 times of streamflow in the mainstream Yellow River, while for tributaries, the mean decline rate of sediment yield is 1.71 times of streamflow. Despite increases in total precipitation amount, erosive precipitation exhibits a clear downward trend over the Loess Plateau after the large‐scale revegetation (2000–2015). This is mainly driven by enhanced local moisture recycling caused by revegetation‐induced redistribution of water and energy budgets. Decreases in erosive precipitation frequency coupled with increased precipitation amount enhance streamflow availability and simultaneously mitigate soil erosion. Our findings highlight the importance of factoring in the two‐way feedbacks between revegetation and erosive precipitation when planning soil and water conservation.

Use of Indices on Daily Timescales to Study Changes in Extreme Precipitation Across Nepal Over 40 Years (1976–2015)

AbstractThis paper presents a comprehensive picture of extreme precipitation across Nepal from 1976 to 2015 based on high‐quality daily precipitation observations from 28 precipitation stations spatially distributed across the country. We computed 11 extreme precipitation indices. The selected indices allow the analysis of extreme events (such as flood/inundation) related to heavy precipitation and evaluate the linkage with indications of agricultural production and drought (such as consecutive dry and wet days). Using a simple daily intensity index (SDII) and the number of days with daily precipitation ≥10 mm (R10), along with the total amount of annual precipitation (PRCPTOT), we summarized the distribution of the wet periods of the year at different locations. We divided the study period into two halves (T1: 1976–1995 and T2: 1996–2015) to examine the temporal mean, trends, and their shift. We emphasized the changes in those indices between these two periods across the country. Our results show that although the amount of precipitation (in terms of PRCPTOT and SDII) did not change significantly between the two periods (i.e., T1 and T2), there exists a clearly increasing trend of extreme precipitation indices in T2 compared to T1. In addition, the consecutive dry days show the rising tendency of elongated dry spells that can adversely affect plant/crop growth in the future. Our study recommends the need for effective management of both precipitation extremes (i.e., drier and wetter), for instance, by introducing irrigation facilities and flood mitigation measures.

Characteristics of the extreme precipitation and its impacts on ecosystem services in the Wuhan Urban Agglomeration

Summer extreme precipitation is one of the most frequent, intense, and influential extreme weather events that occurs frequently in the Wuhan Urban Agglomeration (WUA). Preventing meteorological disasters and coping with climate change necessitate understanding the characteristics and causes of extreme precipitation and its impact on ecosystems. In this study, the spatiotemporal characteristics of summer extreme precipitation in the WUA are analysed from 1961 to 2020. Then, NCEP reanalysis data and the relevant circulation index are used to explore the causes of extreme precipitation. Finally, how extreme precipitation influences key ecosystem services, such as water yield, water regulation, and soil conservation, is investigated. The results reveal that (1) extreme precipitation in the WUA has shown an obvious upwards trend over the past 60 years. Huanggang, Xianning, Huangshi, Wuhan, and E'zhou city demonstrate the highest values. The extreme precipitation increased significantly after 1980s, especially the R97.5P and PRCPTOT with change rate of 12.1 mm/10a and 18.82 mm/10a respectively. (2) Atmospheric circulation variation is a dominant factor affecting extreme precipitation in the WUA and causes the meridional distribution of the “+ − +” wave train in eastern China. The intensity and location of the Western Pacific subtropical high are closely related to extreme precipitation. Furthermore, the weakening of the East Asian summer monsoon circulation is also conducive to the occurrence of extreme precipitation. (3) The spatial distribution of water yield and runoff retention in abnormal extreme precipitation years are similar to the variation patterns of the total amount of extreme precipitation. Water yield and runoff retention in high-value extreme precipitation years are higher than that in low-value extreme precipitation years, while soil conservation shows no difference. In addition, ecosystem services have a synergistic relationship in high-value areas and a trade-off relationship in low-value areas. This study can contribute to the understanding of extreme precipitation in the WUA and its interaction with ecosystem services.

СОВРЕМЕННОЕ СОСТОЯНИЕ РЕСУРСОВ ВЛАГИ НА ФОНЕ КЛИМАТИЧЕСКИХ ИЗМЕНЕНИЙ НА СЕВЕРО-ВОСТОЧНОМ СКЛОНЕ БОЛЬШОГО КАВКАЗА (В ПРЕДЕЛАХ АЗЕРБАЙДЖАНСКОЙ РЕСПУБЛИКИ)

The paper presents the results of our investigation of the moisture resources on the northeastern slope of the Greater Caucasus. For this purpose, standard meteorological data archives of the Siyazan, Khachmaz, Guba, Khaltan and Gyryz meteorological stations located at different heights of this slope were used for the period of 1966-2005. Regional climate changes were assessed by comparing the average monthly air temperature and the amount of precipitation using the diff method for 1961-1990 and 1991-2005. Long-term trends in the change in the total amount of atmospheric precipitation, the Selyaninov HTC andD.I. Shashko’s moisture index for the warm period of the year and the ratio of the precipitation amount for the warm period to the annual precipitation amount were evaluated. It was found out that the multi-year tendency of the precipitation amounts during the warm period has not actually changed.

Projection of extreme precipitation in the Minjiang River Basin, Southeast China

AbstractExtreme precipitation events, which have intensified with global warming, will have a serious influence on society. Based on the latest generation of CMIP6 climate models and high-resolution grid observation data, the quantile mapping method and Taylor diagrams were used to correct and evaluate the simulation values. Six extreme precipitation indices for the near (2021–2040), middle (2051–2070), and far (2081–2100) periods of the 21st century were analyzed under shared socioeconomic pathway scenarios (SSP2-4.5 and SSP5-8.5). The results show that most of the extreme precipitation indices will increase over the Minjiang River Basin in the future, and both extreme precipitation and persistent drought will increase at the same time, which is more likely to cause extreme drought and flood disasters. For seasonal variation, the total amount and intensity of extreme precipitation will increase fastest in autumn, while the frequency of extreme precipitation will increase most in summer. Multimodel median changes show a decrease in the return period of RX1day (the maximum 1-day precipitation). By the end of the 21st century, under SSP5-8.5, the extreme events expected once every 100 years under the current climate are expected to occur approximately every 18.6 years.

Altitude-specific differences in tree-ring δ2H records of wood lignin methoxy in the Qinling mountains, central China

The Qinling Mountains (Qinling Mts.) are characterized as a distinct transition of bioclimatic zones along the north-south geographic boundary in China. Although ongoing global warming may affect the growth of most tree species across elevation gradients, the effect of modern warming on the stable hydrogen isotopes of tree-ring wood is still unknown. In this study, we developed early- and late-wood δ2H chronologies from 1900 to 2018 CE of lignin methoxy groups (δ2HLM) at 700-m intervals from 1700 to 3100 m a.s.l. along the elevation gradient in Mount Taibai (Mt. Taibai), the peak of the Qinling Mts. The δ2HLM values of the earlywood were relatively enriched in 2H compared to the latewood, and an elevation-dependent depleting trend along the altitudinal gradient was observed. Comparing the δ2HLM values with modelled δ2H values of precipitation (δ2HPre) of the sample sites, similar isotopic patterns can be obtained. The reconstructions of δ2HPre values confirm the strong coherence between the isotopic composition of the source water and the methoxy groups in the growing season. The consistency of δ2HLM chronologies between the early- and late-wood at the higher sites was stronger than that at the lower sites. The additional lagged effect and climate response revealed significant seasonal and altitudinal differences. At the timberline site, δ2HLM values of earlywood were mainly related to the January and February temperatures, whereas δ2HLM values of latewood correlated most strongly with temperature from July to September, and both values were controlled by the amount of total precipitation. In addition, the combined new δ2HLM chronologies, based on the lag-1 autocorrelation and the weighted average of the current year earlywood and previous latewood, could be used to merge the corresponding temperature signals from the middle- and low-elevation sites. Altitudinal correlations of elevation offset between the annual δ2HLM chronologies and interpolations of precipitation and temperature suggested that the δ2HLM values at higher elevations better represent regional climatic changes. Therefore, topographic effects such as elevation differences should be considered in large-scale applications of δ2HLM values in future studies.

Prospective of the utilization of rainfall in coastal regions in the context of climatic changes: case study of Egypt

Changes in climate drivers are projected to have a considerable impact on coastal freshwater supply and demand systems in future decades. The utilization of rainfall in coastal regions to secure sufficient freshwater to satisfy the rising demands of socioeconomic development has become a critical duty for decision-makers. This article assesses the present state of rainwater utilization in the water resources system for the coastal regions in Egypt. Volumes of annual rainfall that precipitate in 11 coastal Egyptian cities are estimated using ArcGIS maps and the run off rational equation. A future vision of using the estimated rainwater harvesting (RWH) from urban coastal cities in the water resources system is presented. Several scenarios are suggested and analyzed for using these volumes of water in the total water resources system in Egypt and also in the water resources system corresponding to each selected coastal governorate. The results indicated that over the areas under consideration, the annual maximum total amount of precipitation is limited to 1.8 km3. However, it is anticipated that 1 km3 of the average annual quantity of rainfall water is efficiently used for agriculture. These findings are intended to help managers, planners, and decision-makers to choose locations, invest in water resources, and employ RWH as a substitute for traditional water sources.

High-resolution regional climate modeling of warm-season precipitation over the Tibetan Plateau: Impact of grid spacing and convective parameterization

The Tibetan Plateau (TP) features high elevation and complex terrain, which together shape the region's unique precipitation with high spatial heterogeneity and strong diurnal variations. Due to low spatial resolution, deficient convective parameterization (CP) and uncertainties in other physical assumptions, global climate models and traditional regional models tend to produce excessive precipitation with an earlier diurnal timing. In this work, two sets of numerical experiments with 4- and 10-km grid spacing, respectively, were performed using the Weather Research and Forecasting model to simulate the seasonal precipitation for an average warm season (April–September 2017) over the TP. Results showed that the 4-km experiment with microphysics only (i.e., without CP) reproduced the precipitation amount, frequency, intensity and diurnal cycle reasonably well on regional and local scales, as well as the nocturnal propagating convection at the lee side. The 10-km experiments with scale-aware CP schemes significantly overestimated the precipitation amount and frequency, underestimated the intensity, and failed to capture the diurnal propagation signature. The 10-km experiment with microphysics only had the poorest skill in representing the spatial distribution of precipitation. The scale-aware CP schemes on the 4-km grid caused a too-frequent occurrence of light precipitation even though their overall contribution to the total precipitation amount was rather small, and thus had little benefit to the model performance. A common deficiency in all experiments was excessive afternoon precipitation across the high elevation of the central Himalaya possibly due to the excessive surface insolation, but the satellite-based data may not accurately capture the afternoon precipitation. This research highlights the value of the 4-km model (the so-called convection-permitting model) and the limited benefit of the tested convective parameterizations over the TP.

Investigating survival/growth ratio of scots pine (Pinus sylvestris L.) afforestation efforts and effects of BUROR terracing operations on some soil properties in the lands susceptive to soil erosion in Erzincan

Erzincan-Keklik kayası mevkiinde yürütülen bu çalışmada, 2012 yılında, BUROR mini-ekskavatörle teraslama sonrası uygulanan ağaçlandırma ve erozyon kontrol faaliyetlerinde dikilen sarıçam fidanlarının 2018 yılı vejetasyon dönemi sonundaki (6 yıllık) gelişim durumlarının değerlendirmesi yapılmıştır. Bu amaçla, dikimlerin yapıldığı alandan 20 m x 20 m büyüklüğünde (yaklaşık 400 m2) toplam 7 deneme parseli seçilmiş ve her bir parselde rasgele tespit edilen 30 (toplamda 210 adet) fidanın boyu, kök boğazı çapları ve dikimden bu yana geçen her bir vejetasyon dönemine ait yıllık boy artımları ölçülmüştür. Ayrıca, söz konusu bu ağaçlandırma ve erozyon kontrol faaliyetlerinin toprakta neden olduğu olası bazı fiziksel ve kimyasal değişimleri tespit etmek üzere de 42 tanesi dikim yapılan terasların içinden (fidan dibinden), 29 tanesi ise terasların aralarından (doğal/kontrol alan) olmak üzere toplamda 71 bozulmuş toprak örneği alınarak pH, organik madde (OM), elektriksel iletkenlik (Eİ), agregat stabilitesi ve tekstür değerleri için analize tabi tutulmuşlardır. Araştırma sonucunda, altı yıllık büyüme dönemi sonunda, dikilen sarıçam fidanlarında %88’lik bir başarı oranı yakalandığı, ortalama kök boğaz çaplarının ise 47.3 mm’ye ulaştığı belirlenmiştir. Bununla beraber, güney bakıdaki yamaçlarda dikilen sarıçam fidanlarının ulaştıkları ortalama 130.3 cm’lik boy ile kuzey bakıdakilerden (120.9 cm) istatiksel olarak daha uzun oldukları tespit edilmiştir. Toprak analiz verileri üzerindeki değerlendirmelerde ise mini ekskavatörle yapılan BUROR terasların bazı toprak özellikleri üzerinde negatif etkiler yarattığı ve kısmen bozulan bu özelliklerin doğal değerlerine ulaşmasının zaman alacağı sonucuna varılmıştır. Son olarak, bu araştırmanın önemli sonuçlarından birinin de 2013 ile 2018 büyüme dönemlerindeki sarıçam boy artımlarıyla hem bir önceki yıl yağan toplam yağış miktarları (R2 = 0.77) hem de vejetasyon dönemindeki yağış miktarları arasında (R2 = 0.85) yüksek bir ilişki olduğunun tespit edilmesi olmuştur.

Radial Growth Responses of Four Southeastern USA Pine Species to Summertime Precipitation Event Types and Intense Rainfall Events

Previous dendroclimatic studies have examined the relationship between total precipitation amounts and tree radial growth in the southeastern USA, yet recent studies indicate that specific precipitation event types and rainfall intensities influence longleaf pine (Pinus palustris Mill.) radial growth unequally. It remains unknown if other pine species respond similarly regarding specific precipitation types and intensities as most dendroclimatic studies have focused on precipitation amounts on monthly-to-annual scales without examining either the event type or intensity nor focusing on daily data. Here, we examine summertime climate–radial growth relationships in the southeastern USA for four native pine species (longleaf, shortleaf, Virginia, pitch) during 1940–2020. We examine and compare each species’ response to precipitation event types and intense rainfall events (IREs) and address if the temporal sensitivity to these events is species specific. Distinct temporal sensitivities exist among species, and there is a consistent association between convective, stationary front, and quasi-stationary precipitation and radial growth. All species except Virginia pine have significant (p < 0.001) associations between IREs and radial growth, even though IREs account for ~49% of summertime rainfall. These results suggest precipitation-type sensitivity to radial growth may have dendroclimatic implications.

Remote sensing for monitoring the impacts of agroforestry practices and precipitation changes in particle size export trends

Recent land use changes, the absence of soil protection between crop periods, and extreme precipitation events have been highlighted as major influential factors in the fluctuations of sediment export in the last decades at the catchment scale worldwide. In this regard, soil erosion and fine-particle export are two of the major concerns of soil nutrient loss and water-quality decrease (e.g., increasing turbidity and vector of chemicals). However, while rainfall effects have been well-monitored, recent land use changes and management need additional approaches to evaluate their effect. In Mediterranean mountainous environments, in addition to forest management, agricultural practices during different cropland stages likely increase sediment and particle-bound chemicals in the drainage system. Moreover, most catchments lack instrumentalization. Thus, there is a gap in the knowledge on the processes influencing the sediment exported in ungauged catchments. To evaluate the processes involved, remote sensing and seasonal sampling of suspended sediments were examined for 5 years in a representative agroforestry system in three sub-catchments (SBCs) with different proportions of land uses. Temporal trends of NDVI, EVI, MSAVI, SAVI, and NDWI indices were analyzed for monitoring the vegetation status. With this information, we attempt to evaluate the soil response in terms of particle size export to land use change, vegetation status, and precipitation distribution in fine-grained sediment-reaching streams. Our findings not only highlight the significant effect of heavy precipitation events and vegetation cover on the grain-size fraction of the exported sediment but also reveal the existence of more complex factors influencing the export dynamics. A silt-increasing trend due to the increase of individual heavy precipitations from 2017 onward despite the total precipitation amount not increasing was detected. It is shown that indices such as NDVI and NDMI help detect small changes in vegetation cover, while EVI, SAVI, and MSAVI are more robust for detecting general patterns in large vegetated areas and preventing the appearance of artefacts in the data. Results from this study suggest that land use changes combined with short-scale changing trends of rainfall likely explain most of the possible effects observed in terms of sediment export changes.

Carbon dioxide fluxes of cyanobacterial crusts and underlying soil under different precipitation patterns in the Ulan Buh Desert, China

Cyanobacterial crusts, sensitive to changes in the moisture content, are widely distributed in the Ulan Buh Desert. Changes in precipitation patterns due to global climate change are expected to influence the carbon emission and photosynthetic carbon fixation of soil in areas covered with cyanobacterial crusts. We assessed how changes in precipitation amount and frequency affect carbon processes of Cyanobacterial Crusts. Taking average precipitation amount and frequency in August during the past 30 years as control, we established nine precipitation patterns (three amounts × three frequencies). The net carbon flux (NCF) and dark respiration rate (DRR) of cyanobacterial crusts and underlying soil were investigated. Precipitation could stimulate NCF and DRR immediately. With increasing water application times, the peak values of NCF, DRR and 12 h cumulative carbon emissions gradually decreased. Both precipitation amount and frequency significantly affected cumulative carbon emissions but without an interactive effect. Under the same frequency, cumulative carbon emissions increased with increasing precipitation amounts. Under the same total precipitation amount, cumulative carbon emissions caused by high-frequency events were the highest, followed by those of low-frequency precipitation and the control. However, such changes, against the background of a changing global climate, will result in increased carbon emissions of cyanobacterial crusts and underlying Soil, suggesting that cyanobacteria should be considered in projections of the future carbon budget.

Inconsistent Frequency Trends Between Hourly and Daily Precipitation During Warm Season in Mainland of China

AbstractPrecipitation change is determined by changes in frequency and intensity. Based on hourly and daily precipitation data sets in China (1961–2014) and CMIP6 model, this study found that observed inconsistency in the frequency trend at the two time resolutions (hourly and daily) reflected precipitation becoming more concentrated at 13.4% of stations, resulting in the specific precipitation phenomenon of “more hours in one day, but fewer days.” However, models exhibited opposite precipitation phenomenon at 16.5% of stations and cannot reproduce the widespread increase in the proportion of extreme precipitation amounts (PA) in the total PA, especially at an hourly resolution. Although stations with significant trend from CMIP6 approximately twice the observation, both CMIP6 and observations showed that frequency and intensity changes dominated the total PA trend at hourly and daily time resolutions, respectively. These results demonstrated that daily precipitation observations could not fully capture the important features of short‐duration rainfall.

Rainfall erosivity and climate change: some estimations for the Baltata River basin

The paper assesses the possible impact of changes in precipitation due to global warming on rainfall soil erosion in a small river basin. The Modified Fourier Index (MFI) was selected as an indicator of erosivity. Comparison of this index values in two climatic thirty-years (1991-2010 vs. 1961-1990) has showed that due to insignificant changes in the total amount of annual precipitation, a weak level of erosion hazard, caused by rainfalls in the previous period, has remained in the studied basin under conditions of climate change.

Dynamic Formation Processes and Characteristics of “28 June 2012” Debris Flow in Aizi Valley, Ningnan County, Sichuan Province, China

On 28 June 2012, a large debris flow occurred in Aizi gully, Ningnan County, Sichuan Province, China. It was the most significant debris flow disaster at a construction site in 2012 in China, which left 40 people dead or missing. Field investigations and model calculations were conducted following the event in order to determine dynamic parameters and execute engineering mitigation measures. Analyzing the collected data, it is found that earthquake and drought play a dominant role in debris flow initiation, and from 1 January 1986 to 31 December 2010, 43 earthquakes with a magnitude greater than 3.0 occurred around the study area. Through calculation it was found that the inducive radius of 16 earthquakes was larger than the distance between the epicenter and the study area, and it proves that the study area is frequently affected by seismic activities. Furthermore, on the basis of calculation of rainfall anomaly index H from January 2011 to June 2012, it can be seen that the rainfall of 2011 is extremely low. The percentage of the rainfall anomaly index is almost less than −34%, which indicates that the drought in the basin is serious. Under the influences of repeated seismic activities and continuous droughts, the structure of soil was destroyed and its strength and permeability changed significantly, providing favorable conditions for debris flow initiation. On 28 June 2012, heavy rainfall with the intensity of 23.3 mm/h occurred, and the total amount of precipitation reached 66.1 mm before 6am of 28 June 2012. Debris flow was induced due to the triggering effect of the torrential rain. Studying the causes of the large-scale debris flows in construction sites can significantly facilitate the prevention and mitigation of future debris flow disasters, as well as reduce the potential of hazards caused by debris flows in major engineering areas.

Quantifying moisture recycling of a leeward oasis in arid central Asia using a Bayesian isotopic mixing model

Locally recycled moisture from transpiration and surface evaporation is of great importance in the terrestrial hydrological cycle, especially in the widely distributed oases across arid central Asia. Quantitative assessment of the proportional contribution of recycled moisture to local precipitation, i.e., the recycling ratio, is useful to understand the land-air interaction as well as the anthropogenic impact on the regional water cycle. Here we analyzed the stable hydrogen and oxygen isotopes in precipitation samples collected at six stations across the Kaxgar-Yarkant Oasis in the western Tarim Basin of central Asia from April 2018 to June 2020. Using this data, the moisture recycling ratio in this typical oasis was assessed using a Bayesian three-component isotopic mixing model. For the plain stations, the annual weighted mean δ18O value in precipitation ranged from −5.94 ‰ to −1.46 ‰, and the mountain station has a lower annual mean precipitation isotopic ratio. The average recycling ratio during the summer months ranged between 17.0 % and 63.9 % for each sampling station in the Kaxgar-Yarkant Oasis, and the proportional contribution from transpiration ranged from 15.1 % to 61.3 %. The contribution of plant transpiration to local precipitation is much larger than that of surface evaporation. The recycled portion in total precipitation amount may increase the local precipitation under an oasis expansion background but is insufficient to change the arid background. In addition, the Bayesian isotopic mixing model is promising to determine the recycling ratio in an arid setting, and provides more spatial details than the climate reanalysis-based calculation.

Seasonal heavy precipitation sensitivity to moisture corrections in the western Mediterranean across resolutions

The controlling role of atmospheric water vapour for heavy precipitation leading to extreme events has been widely demonstrated, along with the existing gap of adequate moisture observations and the frequent biases present in model simulations concerning this fundamental variable. In this study, we profit from a state-of-the-art dense network of GPS measurements over Europe retrieving a homogenized GPS-derived Zenith Total Delay (GPS-ZTD) data set up to 10 min of temporal resolution, to assess the seasonal sensitivity of convection-related processes and heavy precipitation modelling to atmospheric humidity corrections. For this purpose, we perform nudging experiments with the COSMO-CLM model at two spatial resolutions, 7 km (parameterized convection) and 2.8 km (explicitly resolved convection) covering the autumn period of 2012, when the Special Observation Period (SOP) 1 of the Hydrological Cycle in the Mediterranean Experiment (HyMeX) program took place in the Western Mediterranean, which is our area of interest.The benefits and disadvantages of GPS-ZTD nudging and resulting moisture corrections are disentangled. The impact on high-resolution parameterized versus convection-permitting simulations is compared. A process-understanding methodology and a local-to-regional approach are used. Our results show a beneficial impact on the seasonal scale at both model grid spacings improving the representation of the chain of processes leading to heavy precipitation, contrary to the non-systematic improvement at the event and sub-event scales. The correction of atmospheric moisture entails a reduction of about 10% in the total column water vapour and corrections on single locations up to 10 mm counteracting the model wet bias across scales. The location, structure, and amount of total precipitation are positively affected. Particularly, the combination of high-resolution atmospheric humidity observations and fine convection-permitting simulations shows great potential for correction of the precipitation daily cycle, key for accurate precipitation modelling. The difference in the density of local and upstream observational networks and the lack of information on the vertical stratification of moisture are identified weaknesses, which could be determinants in obtaining more accurate corrections on seasonal to sub-seasonal scales after assimilation strategies.

Effect of fast drainage in karst sinkholes on surface runoff in Larzac Plateau, France

Study regionA 1 km² mountainous karst watershed on the Larzac Plateau in Southern France. Study focusThe village of La Vacquerie, located at the outlet of the watershed, is punctually affected by flash floods during storm events. On the contrary, no runoff is observed in the village during other rainfalls. A sinkhole, draining surface flows at the entrance of the village, plays a role on these differences. Descriptions of short and intense rainfalls in 2015 (avg. 40 mm/h over 5 h) and long and light events in 2014/2016 (avg. 8 mm/h over 25 h) provide valuable data to calibrate inputs of a distributed physic-based flow model, in particular the sinkhole drainage capacity. This study aims to quantify drainage capacity changes with rainfall characteristics and to find the rain intensity threshold at which runoff exceeds sinkhole capacity. New hydrological insights for the regionThe hydrological water balance of the hydrosystem is affected by the intensity variations for each of the different rain events. It shows the limited part of drainage in sinkhole (10%) during long light rains but its significant increase (40%) during short and intense rains. Drainage in sinkhole is affected by intensity variations rather than by the total amount of precipitation. When intensity exceeds 110 mm/h the sinkhole is submerged. However, this result is obtained in a case of Plateau configuration, where the saturated level, located deep below the surface (here 500 m), does not retro-affect drainage in the sinkhole.

Detecting characteristics of extreme precipitation events using regional and satellite-based precipitation gridded datasets over a region in Central Europe

Perception of the spatio-temporal events of extreme precipitation and their variations is essential for diminishing the natural hazards linked with extreme events. In this research, a satellite-based precipitation dataset derived from remotely sensed soil moisture (SM2RAIN-ASCAT, obtained from ASCAT satellite soil moisture data through the Soil Moisture to Rain algorithm) was selected to evaluate the accuracy of daily precipitation and extreme events estimations against a regional gridded weather dataset by employing various performance indicators, and ETCCDI indicators (CDD, and CWD, SDII, R10mm, R20mm, R95p, R99p, Rx1day, and Rx5day). The study area includes entire Poland as well as small parts of Ukraine, Belarus, Slovakia, the Czech Republic, Russia, and Germany. According to PBIAS (~ −3.9 %) and coefficient of correlation (~0.74), SM2RAIN-ASCAT has good accuracy in the study area. Assessments reveal that, in general, over southern, mountainous part SM2RAIN-ASCAT does not have accurate estimations. According to the reference dataset, during the 2007–2019 period, on average, the length of dry days was ~22 days, while SM2RAIN-ASCAT shows ~19.6 consecutive dry days. In contrast, SM2RAIN-ASCAT overestimated (16 days/year) the consecutive wet days compared to the reference dataset (~8.7 days/year). SM2RAIN-ASCAT underestimated the number of heavy precipitation days index (R10mm) over the northern part of the region, close to the Baltic Sea), but the accuracy increased in the southern parts. SM2RAIN-ASCAT underestimated the maximum 1-day rainfall total and relative max 5-day precipitation amount indices. The total precipitation divided by the amount of wet days index shows that SM2RAIN-ASCAT has relatively acceptable accuracy in the center and south of the study area. Our results show that SM2RAIN-ASCAT should be improved for relatively higher extreme indicators.