Annual Precipitation Amount Research Articles

The influence of soil hydrothermal regime on post-fire recovery process in the ribbon-like pine forests of Western Siberia

The features of the hydrothermal regime and the vegetation cover of burnt-out areas in the ribbon-like pine forests of Western Siberia have been studied on a zonal-typological basis. Dry forest growth conditions after a fire are characterized by a weak development of the ground cover and natural regeneration than fresh and moist forest growth conditions. As we move from the dry steppe subzone to the southern forest-steppe, the forest growing conditions on the burnt areas improve thanks to an increase in the annual amount of precipitation and soil moisture.

Продуктивність сіяних лучих травостоїв залежно від елементів технології вирощування

The results of research on the influence of species composition of grass mixtures, the level of fertilizing, and growth stimulator Fumar on the productivity of sown meadow herbage on typical low-humus chernozems of the Right-Bank Forest-Steppe are presented. The experimental part of the work was performed in the scientific laboratories of the Forage Production, Land Reclamation, and Meteorology Department in the production unit of the National University of Life and Environmental Sciences of Ukraine "Agronomic Research Station". The territory of the research station is located in the Right-Bank Forest-Steppe and is a part of Bila Tserkva agro-soil district. The experimental plots were laid on typical low-humus chernozems, coarse-grained light loam in terms of mechanical composition, which are characterized by a high content of gross and mobile forms of nutrients. The climate of the region is characterized by unstable humidity and moderate temperatures. The average annual air temperature is 6-8 ° C. The annual amount of precipitation reaches 562 mm, during the growing season - 354-394 mm (63-70% of the annual norm), which falls unevenly throughout the year. The purpose of the study is to establish patterns of high productivity formation of sown perennial grasses depending on the species composition and fertilizers on typical low-humus chernozems of Right-Bank Forest-Steppe. The analysis of fertilizers effect showed that the highest productivity on all stands was provided by the combined application of complete mineral fertilizer and biostimulator of growth Fumar (N60P60K90 + Fumar), where productivity compared to the option without fertilizer on average over the years of research on alfalfa t/ha of dry mass or by 9%, on its mixtures with cereals - by 0.89–1.19 t/ha, or by 9–11%, and on cereal herbages - by 2.79 t/ha, or by 54% at LSD 0.41 t/ha. Productivity from the use of growth stimulant Fumar increased by 0.27-0.32 t/ha of dry weight or 2-4% and depended a little on the species composition of herbages. High efficiency of alfalfa inclusion in leguminous-cereal grass mixtures, as well as use of single-species alfalfa sowing for fodder purposes, especially on backgrounds without mineral nitrogen, was revealed. The productivity of these herbages in comparison with cereal herbages on nitrogen-free backgrounds (variants without fertilizers and P60K90) on average for 2014–2016 increased from 3.74–4.10 to 8.06–8.68 t/ha of fodder units, from 0.57-0.66 to 1.70-1.96 of crude protein, from 93.7-101.4 to 182.1-206.2 GJ/ha of gross energy and from 38.9-42.7 to 82.4–91.3 GJ/ha of metabolic energy or by1.8–3.0 times, while on backgrounds with nitrogen application (variants N60P60K90 and N60P60K90 + Fumar) - respectively from 5.73–5.93 to 8, 27–9.22 t/ha, from 1.13–1.21 to 1.89–2.29 t/ha, from 139.8–144.8 to 192.5–219.1 GJ/ha, and from 59.6–61.7 to 89.4–98.2 GJ/ha, or by 1.4–1.6 times. Comparison of the productivity of alfalfa-cereal mixtures with single-species sowing of alfalfa shows that on the same backgrounds it was at the same level with slight fluctuations. On average, in the first three years of use, the most influential factor in the yield of 1 ha of dry mass is the factor of grass cover with a share of 60%. The share of fertilizer factor is 40%. The inclusion of alfalfa in legumes and cereal mixtures, as well as the use of single-species sowing for fodder purposes compared to cereals in the background without mineral nitrogen on average for the first three years of use, increases the productivity of sown grasslands from 5.12-5.54 to 10,44–10.78 t/ha of dry weight, from 3.74–4.10 to 8.06–8.68 t/ha of feed units, from 0.57–0.66 to 1.70 1.96 of crude protein and from 38.9–42.7 to 82.4–91.3 GJ/ha of exchange energy or by 1.8–3.0 times, while on backgrounds with N60 application - from 7.28–7.59, respectively, to 9.42–9.71 t/ha, from 5.73–5.93 to 8.27–9.22 t/ha, from 1.13–1.21 to 1.89–2.29 t/ha and from 59.6–61.7 to 89.4–98.2 GJ/ha, or only by 1.4–1.6 times. Among the alfalfa-cereal herbages in the first two years of use, the most productive was the agrocenosis, the cereal part of which is represented by smooth bromegrass and English bluegrass. The lowest, but quite high productivity of alfalfa and alfalfa-grass herbages is provided without fertilizers, which on average for the first three years of use ranges from 9.95 to 10.86 t/ha of dry weight, 1.70 to 1.85 t/ha of crude protein, 82.4–85.8 GJ/ha of metabolic energy, while cereals, respectively, 5.12 t/ha, 3.74 t/ha, 0.57 t/ha, 38.9 GJ/ha.

Projected changes in air temperature, precipitation and aridity in Serbia in the 21st century

AbstractIn this study, the projected changes of the average monthly and annual air temperatures, precipitation amounts and De Martonne aridity index in Serbia in the 21st century are examined. For that purpose, the spatial distribution of air temperature and precipitation amount is statistically modelled using data of 64 climatologic stations and 421 precipitation stations for the period 1976–2005 using multiple linear regression. The De Martonne aridity index is calculated from the spatially distributed data. In order to obtain regional averages and variability, we divide Serbia into three subdomains: the western zone (the Dinarides), eastern mountainous (Carpathian‐Balkan) zone and the terrains with altitudes lower than 500 m a.s.l. (Lowland). As a second step, the members of the COordinated Regional Downscaling EXperiment (CORDEX) for Europe (EURO‐CORDEX) are evaluated in terms of near‐surface air temperature and precipitation for Serbia. By comparing respective values for the period 1976–2005 with future periods 2021–2050 and 2071–2100, we derive the climate change signal for near‐surface air temperature, precipitation and the De Martonne index for both scenarios RCP4.5 and RCP8.5. Hereby, the ensemble averages are calculated as weighted averages using the inverse standardized Euclidean distance by comparing observation and model results for near‐surface air temperature and precipitation as a weight. We find for the period 2071–2050 that most ensemble members predict a statistically significant increase in monthly and annual near‐surface air temperature in both scenarios in all three subdomains, and a statistically significant decrease in the yearly De Martonne index in the RCP8.5 scenario in the Carpathian‐Balkan and Dinarides. For the last decades of the 21st century, our findings indicate much higher temperatures and increased risks of drought for the RCP 8.5 scenario compared to both the observations from 1976 to 2005 and the RCP 4.5 scenario.

An Analysis of the Influence of Annual Rainfall Fluctuations on Wildfire Occurrence in Protected Areas in the Northwest of Zimbabwe

The occurrence and threat from wildfires are a conservation concern in semi-arid savanna-protected areas. The risk of wildlife occurrence is uncertain under climate change scenarios. However, general predictions are that different changes are likely to occur in weather conditions in different landscapes. We sought to analyze the influence of annual precipitation on wildfire occurrence in a protected area landscape in northwest Zimbabwe. Data on annual rainfall received and wildfire occurrence for Chizarira National Park (CNP), Chirisa Safari Area (CSA), and Sengwa Wildlife Research Area (SWRA) was analyzed using regression analysis. The relationship between the annual precipitation amount received per site and the number of wildfires recorded per site showed a positive correlation only for CSA. No significant differences were observed for CNP and SWRA at a significant level of p< 0.05. The highest number of wildfires were recorded between July and November. We advance that annual rainfall is one factor among many drivers of wildfires and that this is not uniform but varies across the landscape. Effective annual precipitation contributes to high vegetation biomass production and accumulation of such biomass increases the risk of wildfires. In some instances, rainfall patterns could not explain the occurrence of wildfires. We, therefore, contend that other drivers such as human activities and natural factors are important drivers of wildfires across the three sites. The conservation implication of our finding is that robust fire management plans need to take an ecosystem approach that includes communities adjacent to protected areas.

Simulation and estimation of future precipitation changes in arid regions: a case study of Xinjiang, Northwest China

Precipitation is critical for maintaining the stability of an ecosystem, especially in arid regions. This study primarily focuses on climatic changes during present (from 1985 to 2005) and future (from 2040 to 2059) periods in Xinjiang, Northwest China. In this study, the Weather Research and Forecasting model is implemented in Xinjiang to efficiently predict the future climate. Moreover, the National Climate Research Center Community Climate System Model version 4 is employed for the mid-21st century under representative concentration pathways 4.5 and 8.5 (RCP4.5 and RCP8.5, respectively). Our results indicate that the amount of annual precipitation will increase in the future under RCP4.5 and RCP8.5 in Xinjiang, especially in mountainous areas. The increase in precipitation is predicted to be much smaller under RCP8.5 than under RCP4.5, except in Southern Xinjiang. Moreover, the increasing precipitation predicted in Xinjiang implies that the current humid and warm conditions will persist, thereby further indicating that Xinjiang is still currently suffering from a dry climate. The largest increase in seasonal precipitation is predicted to occur in spring and summer in Tianshan and Northern Xinjiang, whereas this phenomenon is predicted to occur in spring and winter in Southern Xinjiang. In addition, it is predicted that daily heavy precipitation events will occur more frequently in various subregions of Xinjiang, although light rain events will remain dominant. Finally, the relative humidity is closely related to the changes in annual and seasonal precipitation.

Regeneration trends along climate gradients in Taxodium distichum forests of the southeastern United States

The development of relict vegetation at the edges of some ecosystems has taken place particularly in environments where the regeneration of foundational species is declining. As an important stage of regeneration in the Taxodium distichum, this study explored the relationship of cone volume and seed number across environmental gradients in the Mississippi River Alluvial Valley (MRAV) and northern Gulf of Mexico Coast (GOM) in a long-term network of forested wetlands (North American Baldcypress Swamp Network (NABCSN)) from 2007 to 2019. Resembling spheroids, the volumes of Taxodium distichum cones were based on the measured dimensions of the cones collected in swamps across southeastern environmental gradients. Cones with larger volumes also had larger numbers of seeds (r2 = 0.423, F = 113.9, p < 0.0001; Linear regression equation: Seed number per cone = 9.8925223 + 0.8854056* Cone volume cm3). Mean cone volumes were related to water availability with highest volumes in locations with moderate amounts of total annual precipitation (e.g., White River National Wildlife Refuge (NWR) Arkansas, Tensas NWR Louisiana, and Morgan Brake NWR Mississippi), and longer periods of annual percent time of site drawdown. Cone volume was high in 2018 following the 2017 mega-flood in the Mississippi River Alluvial Valley (MRAV) generated by Hurricane Harvey. Mean annual air temperature was not related to cone volume. Along the Gulf Coast, mean cone volume increased from east to west from Florida to Texas. Especially near the edge of the range of T. distichum forests, smaller cones may be related to regeneration failure and lower seed numbers to support regeneration. A better understanding of regeneration constraints can inform managers of the emergence of relict status in these forests.

Analysis of decadal precipitation changes at the northern edge of the Alps

Precipitation data from four weather stations in Bavaria, Germany, situated at the northern edge of the Alps have been evaluated for the period 1901 to 2019. Decadal changes have been computed as sliding 30‑year averages and as the difference between the 30‑year periods 1990–2019 and 1901–1930. The annual precipitation at these four stations increases, fitting in magnitude roughly to the temperature increase in the course of global warming. The number of dry days slightly increases as well as a consequence of a northward shift of the storm tracks over Europe. Due to these two features the precipitation intensity on wet days increases. The increase in maximum daily precipitation amounts is less than the increase in the annual precipitation amount. The observed maximum daily precipitation in the full four datasets is 138.5 mm at the station Hohenpeisenberg in 1999. The length of dry spells is increasing at three of the four stations as well. The overall observed precipitation patterns fit to the findings of regional climate model simulations for future climate scenarios for this region. Thus, they can be interpreted as signs that climate change is well underway in Southern Bavaria as it is in most places of the world.

Physically Based Summer Temperature Reconstruction From Melt Layers in Ice Cores

AbstractPrevious reconstructions of summer temperatures from ice cores have relied on a statistical relationship between a melt layer and temperature observed at nearby stations. This study presents a novel method for reconstructing summer temperatures from melt layers in ice cores using an energy balance model that incorporates heat conduction and meltwater refreezing in the firn. We use the seasonal patterns in the ERA‐Interim reanalysis data set for an ice core site to calculate the amounts of refreezing water within the firn under various summer mean temperature (SMT) and annual precipitation conditions, and prepared calibration tables containing these three variables. We then estimate the SMTs from the refreezing amount and annual accumulation, both of which can be obtained from an ice core. We apply this method to four ice cores that were recovered from sites with different climates: two sites on the Greenland Ice Sheet, one in Alaska, and one in Russian Altai. The reconstructed SMTs show comparable variations with those of observed temperatures at nearby stations. The nonlinear relationship between SMT and melt layer thickness differs between sites, indicating that a single linear approximation cannot be employed to estimate SMT. Sensitivity analyses suggest that the annual temperature range, amount of annual precipitation, and firn albedo (which is a time‐invariant value in the model) significantly affect the relationship between SMT and melt layer thickness. This new method provides an alternative to existing approaches and yields an independent estimate of SMT from ice cores that have been affected by melting.

Precipitation and yield of spring wheat in the semiarid zone of Orenburg Cis-Urals

Spring wheat is produced in Orenburg Cis-Urals in conditions of moisture deficiency. Among 69 years studied (1951-2019), 16 turned out to be dry, 25-arid, with a total precipitation of less than 380 mm. In terms of precipitation during the growing season 50 years were dry and arid, a total was less than 130 mm. According to the annual amount of precipitation, a cyclicality was established with alternation of two humid decades with one dry one. In support of the hypothesis, precipitation in the first half of the growing season of wheat is dominant, and the least in the second of all categories. Significant relationships were established between them and the yield, r = 0.814 and r = 0.574. Annual moisture resources have a weaker relationship with yield (r = 0.566) than precipitation during the growing season (r = 0.730). The surge in yield due to precipitation in the first half of the growing season of wheat is its response to the moistening of the upper soil layer during tillering and the formation of a secondary root system. Hence, the main requirement for the technology of growing spring wheat is to moisten the top 0-5 cm of the soil layer in the tillering phase to 17% of the mass of dry soil and above.

Assessment of runoff characteristics changes of the left bank tributaries of the Upper Dniester under warming conditions

The inflow of water from the left-bank tributaries of the Upper Dniester is an important component of the runoff formation for the whole river. The study of changes in their water content in the context of global warming is quite urgent and agrees with the provisions of the strategic programme for the Dniester Basin for 2021-2035 aimed at ‘climate change mitigation’ and ‘promoting the principles of sustainable water management’.&#x0D; The paper's objective is to carry out a research into the changes in climatic factors and runoff characteristics that occurred on the left bank of the Upper Dniester in the early 21st century.&#x0D; The research was performed on the basis of hydrometeorological data for the period of 1945-2018. The main research methods include the regression analysis and the method of differential integral curves.&#x0D; It is found that, within the area under study, there is an increase in average annual air temperatures against the background of constant or insignificantly increasing amounts of annual precipitation, thus creating unsatisfactory conditions for runoff formation. It is established that, during the months of cold period, there is an increase in air temperature and that since 1989 the frequency of cases, when the temperature crosses the range of positive values, keeps increasing. 1989 is a turning point in the chronological course of average annual air temperatures; a positive phase of long-term fluctuations starts since that year. With regard to annual precipitation fluctuations from the mid-60s of the last century up to 2013, a positive phase was also identified; within this phase there was a short period of insufficient moisture (1981-1996). It was found that the response of runoff characteristics to climate change was not the same. Maximum runoff during the spring flood is the most sensitive to global warming, since such warming has worsened the conditions for accumulation of water reserves in the snow cover. The transition of maximum runoff fluctuations to the low-water phase took place in 1981. The average long-term decrease in the maximum water flow rates during the spring flood for the period of 1950-2018 amounts to -16.9%. Unlike maximum runoff, the characteristics of the annual and minimum runoff changed gradually during the winter and summer low-water periods and the final transition to the low-water phase of fluctuations occurred only in 2009-2011. Certain inertia of changes in the water resources of Podillya rivers under the warming conditions is caused by the subsurface component making a high contribution to the annual runoff formation (60%). Significant portion of the groundwater supply ‘mitigated’ the effects of surface runoff loss during spring floods. The research allowed establishing the occurrence of statistically significant negative trends in the annual and minimum runoff fluctuations since 1998. If continue to preserve, the identified climate change trends will decrease the inflow of water from the Podillya rivers to the main Dniester River.

Features of growth and development of alfalfa-cereal grass stands depending on the species composition and fertiliser

The results of studies on the influence of the species composition of herbage, the level of fertiliser, and growth stimulator Fumar on the density and botanical composition of plants are presented. The experimental part of the study was performed in the scientific laboratories of the Department of feed production, land reclamation and meteorology in the production division of the National University of Life and Environmental Sciences of Ukraine "Agronomic Research Station". The territory of the station is located in the Right-Bank Forest-Steppe and is part of the Bilotserkivsky agro-soil district. Experimental plots were laid on chernozems of typical low-humus large-dusty light loamy mechanical composition, which are characterised by a high content of nutrients. The climate of the region is characterised by unstable humidity and moderate temperature conditions. The average annual air temperature is 6-8°C. The annual amount of precipitation reaches 562 mm, during the growing season – 354-394 mm (63-70% of the annual norm), which falls unevenly throughout the year. Based on the conducted studies, it was identified that sown herbage is formed with a density of 686-1250 shoots per 1 m2 and a height of 58-148 сm. Alfalfa-cereal and cereal stands are denser than alfalfa ones. For the period from 1 to 3 years of use of herbage, the density of alfalfa shoots decreases, while that of orchard grass and smooth brome increases, and more intensively with the introduction of N60. During the first three years of use, grass stands are formed with the dominance of sown components with a share of alfalfa in single-species sowing of 85-98%, in alfalfa – cereal mixtures – 30-58%. For the period from the 1st to the 3rd year of use of alfalfa-cereal stands, the share of alfalfa decreases by 11-24%, and more intensively with the introduction of N60. In addition, between the two cereal components, there is a change of co-dominant – from meadow fescue to eastern fescue, eastern fescue to orchard grass, perennial ryegrass to smooth brome, like in the cereal stand, eastern fescue to smooth brome. In the 3rd year of use, ryegrass thins out, reducing the involvement rate to 5-14%

Comparison of the root–soil water relationship of two typical revegetation species along a precipitation gradient on the Loess Plateau

Soil water and root distribution following revegetation are key research topics in water-limited ecosystems. However, little is known about the interaction between soil water and root distribution in deep soils under different precipitation conditions. Knowledge of the root–soil water relationship of revegetated land and its response to precipitation is crucial for the management of water resources and ecological restoration worldwide, including on the Chinese Loess Plateau. In this study, we investigated soil water and root distribution under apple orchard and black locust down a 10 m soil profile and exposed to different amounts of annual precipitation on the Loess Plateau. The results showed that soil water content (SWC) under two typical planted forests both significantly decreased as the mean annual precipitation (MAP) decreased. SWC spatial variation is demarcated by a 500–550 mm precipitation threshold, being relatively high when MAP > 550 mm but extremely low when MAP < 500 mm. In apple orchards, the depth above which 50% of the roots were present increased with increasing precipitation, but in black locust it became shallower. The results of a linear mixed model revealed a significant relationship between fine root length density and SWC depletion degree for black locust irrespective of the amount of precipitation, but it was only found in the 200–1000 cm soil layers with MAP > 550 mm and the 0–200 cm soil layers with MAP < 550 mm for apple orchards. The MAP × depth interaction was significant with respect to SWC depletion degree for MAP > 550 mm, but not for MAP < 550 mm in both vegetation types. These findings add to our current understanding of the root–soil water relationship of species used for revegetation and highlight the need to assess the long-term effect of revegetation on soil water consumption in water-limited ecosystems.

Development of artificial intelligence models for well groundwater quality simulation: Different modeling scenarios.

Groundwater is one of the most important freshwater resources, especially in arid and semi-arid regions where the annual amounts of precipitation are small with frequent drought durations. Information on qualitative parameters of these valuable resources is very crucial as it might affect its applicability from agricultural, drinking, and industrial aspects. Although geo-statistics methods can provide insight about spatial distribution of quality factors, applications of advanced artificial intelligence (AI) models can contribute to produce more accurate results as robust alternative for such a complex geo-science problem. The present research investigates the capacity of several types of AI models for modeling four key water quality variables namely electrical conductivity (EC), sodium adsorption ratio (SAR), total dissolved solid (TDS) and Sulfate (SO4) using dataset obtained from 90 wells in Tabriz Plain, Iran; assessed by k-fold testing. Two different modeling scenarios were established to make simulations using other quality parameters and the geographical information. The obtained results confirmed the capabilities of the AI models for modeling the well groundwater quality variables. Among all the applied AI models, the developed hybrid support vector machine-firefly algorithm (SVM-FFA) model achieved the best predictability performance for both investigated scenarios. The introduced computer aid methodology provided a reliable technology for groundwater monitoring and assessment.

Characteristics of Summer Hourly Extreme Precipitation Events and Its Local Environmental Influencing Factors in Beijing under Urbanization Background

Studies on urban extreme precipitation and its influencing factors are significant for prevention and reduction of meteorological disasters; however, few studies focus on hourly extreme precipitation (HEP) events due to the limitation of observation. By using the summer hourly precipitation data in Beijing from 1980 to 2020, the spatial distribution and temporal variation of HEP as well as its local environmental influencing factors are investigated. It is found that both summer precipitation amount and frequency of HEP are affected by topography, with high values in windward slope area. The summer precipitation amount of HEP is 160–200 mm, accounting for 42–47% of the annual summer precipitation amount, while the frequency proportion of HEP is only 5.5–6.0%. Although the summer precipitation amount and frequency in Beijing both decrease in the past 41 years, those for HEP present an opposite trend mainly due to the increasing HEP since 2003 and this is a phenomenon worthy of attention. A similar bimodal pattern in diurnal variation is found for the summer precipitation amount and frequency of HEP, with two peaks in 19–22 LT and 01–05 LT, respectively, indicating that HEPs are more concentrated in the evening and early morning especially in urban area. Moreover, the urbanization process of Beijing is consistent with the change trend of HEP, implying that the stronger the urban heat island intensity (UHI), the higher the probability of HEP. Furthermore, the convergence lines of terrain are also conducive to local heavy rainfall, and lower tropospheric stability (LTS) and convective available potential energy (CAPE) as well as aerosols may also affect HEP in Beijing.

REAL-Fog part 2: A novel approach to calculate high resoluted spatio-temporal fog deposition: A daily fog deposition data set for entire Germany for 1949–2018

Fog deposition depends strongly on location and orographic setting. Even if the absolute amount can be small at some locations, it could play a decisive role. This is also true for Germany. In the lowlands, the annual amount of fog precipitation is in the range of a few mm per year, in the higher altitudes of the low mountain ranges a few hundred mm per year. In this article, we estimated the fog deposition based on the REAL-Fog model for Germany at daily time steps and one kilometre spatial resolution for a 70-year period for the years 1949 to 2018. These results were compared with another fog deposition modelling approach, station measurements and water balance modelling for different catchments in our study region. Comparing the results gives quite an interesting insight and outlook to the challenges to face in the future. The gridded data of the daily sum of the fog deposition we made available via HydroShare repository.

Stationarity in the variability of arid precipitation: A case study of arid Central Asia

Precipitation is particularly scarce in arid Central Asia (CA), and is expected to be severely impacted by future warming, and the assessment of the stationarity of precipitation variability is important for managing surface water resources in this region. In this study, we investigated the statistics of stationarity in the totals and extremes of precipitation in CA based on the longest observational records (1881–2006), tree-ring reconstructed records (1756–2012 and 1760–2015), and the Coupled Model Intercomparison Project 5 (CMIP5) simulations, applying the autocorrelation function and testing criteria established based on the statistical definitions of stationarity. We analyzed the longest daily precipitation record (Tashkent station, 1881–2006) and found that the autocorrelation coefficient of the precipitation totals (PRCPTOT) and annual maximum 1-day precipitation amount (Rx1day) were statistically insignificant for all lags, implying stationary behavior. Regionally, nearly all the Global Historical Climatology Network-Daily Database (GHCN-D) observatory sites (1925–2005) indicated likely stationary behavior. The reconstructed records were also indistinguishable from a random process. For the CMIP5 models, the simulated and projected PRCPTOT closely approximated a purely random process; however, the projected Rx1day maintained non-stationary means in most of the models under the representative concentration pathway (RCPs), implying that extreme events would increase in the future. The mean precipitation changes (ΔP) can be expressed as an exponential function depending on the length of the successive mean periods (μ) and variance (σ2). The ΔP of the next decade is projected to be within ±14.8% of the previous decades mean annual PRCPTOT over CA. The higher the RCPs, the higher the ΔP over CA. The results show that the detection and prediction of precipitation change will be challenging in arid CA.

Inorganic chemical components in precipitation in the eastern U.S. and Eastern Canada during 1989–2016: Temporal and regional trends of wet concentration and wet deposition from the NADP and CAPMoN measurements

With the implementation of the Clean Air Act Amendments of 1990 in the U.S. and similar emission reduction measures in Canada, sulfur dioxide (SO2) and nitrogen oxides (NOx = NO + NO2) emissions in the eastern U.S. and Eastern Canada declined significantly during the period 1989–2016. Correspondingly, air quality over the region improved tremendously and sulfate, nitrate and acidity in precipitation decreased significantly. In this study, we analyzed measurement data in the eastern U.S. and Eastern Canada from the two national long-term wet deposition networks, the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) in the U.S. and the Canadian Air and Precipitation Monitoring Network (CAPMoN) in Canada, to reveal the spatial-temporal trends of precipitation concentrations and wet deposition of sulfate, nitrate, ammonium and acid in the eastern part of North America (broken into 4 different regions) for the period of 1989–2016. Comparing 2014–2016 to 1989–1991, the results show that the acid, sulfate and nitrate wet deposition decreased by 78%, 69% and 46% for 1989–2016, and decreased annually at rates of −2.8~-3.6% yr−1, -2.5~-2.9% yr−1, and -1.6~-2.0% yr−1 over different regions, respectively. It also revealed that there were no statistically significant trends for the annual mean wet concentrations of ammonium (NH4+) in precipitation in the Midwest and the Mid-Atlantic of the U.S. (P>0.4 respectively). However, there were statistically significant increasing trends of annual wet deposition of NH4+ over these latter two regions (P = 0.01–0.13) with an annual rate of increase of 0.6% and 0.4%, respectively. The increasing trends of wet deposition of NH4+ in these regions were mostly due to increasing annual precipitation amounts, as indicated by positive correlation coefficients between them (R = 0.67–0.77), and a statistically significant increasing trend of the precipitation amount during the period. The annual mean wet concentration of chloride ion (Cl−) in precipitation in the above two regions had a clear decreasing trend of −1.5% annually (P < 0.001). In 20 years (2010–2014 vs. 1990–1994), the frequency of acidic rain with pH < 5 was reduced from 72% to 49% in the Northeast U.S. and Eastern Canada, 88% to 37% in the Midwest, 97% to 60% in the Mid-Atlantic and 79% to 49% in the Southeast. The imbalance between the measured cations and anions increased over the years from 2009 to 2016 with the anions dropping lower than the cations in all regions. This can be attributed to the increased dissociation of weak organic acids, i.e., the free H+ contributed from these weak acids increased as the acidity of the precipitation decreased, but the corresponding conjugate bases were not measured and not included in the calculation of total anions. This pH buffering effect needs to be taken into account in assessing the reductions in acid deposition following the implementation of the Clear Air Act Amendments (CAAA) of 1990 in the U.S. and measures to reduce the emissions of SO2 and NOx in Canada.

Changes in Slight and Extreme Precipitation Events From 1963 to 2017 Over Northern Xinjiang, China

Based on daily measured data from 25 stations in Xinjiang Province from 1963 to 2017, we discuss the statistical characteristics, linear trends, and temporal concentration of slight precipitation (SP) and extreme precipitation (EP) events, and consider relationships between SP and EP events and daily mean temperature. The results show that SP events contribute strongly to the total annual number of wet days, and that EP events contribute strongly to the total annual precipitation amount. In consist with the decrease in SP events and the increase in EP events over the 55-year period, the contribution of SP events to total annual number of wet days has decreased significantly while the contribution of EP events to total annual precipitation amount has increased significantly. SP event usually distributes through most months of the year, whereas EP event usually concentrates in summer (JJA). Influenced by the negative trends for SP events frequency and positive trends of EP events frequency during recent decades, the concentration degree for SP and EP events have significantly increased and decreased, respectively. Distinct differences are found between the relationships of SP events and EP events to daily mean temperature. The daily mean temperature recorded at the stations in Northern Xinjiang on days with SP events was between –35°C and +34°C, and for EP events ranged from –21°C to +30°C. Regionally averaged curves for the change in SP and EP event frequency with temperature have bimodal and unimodal distributions, respectively. Trends for daily mean temperatures and for the frequency of SP events at different temperatures agree well over nearly the entire temperature range, while trends for daily mean temperatures and for the frequency of EP events at different temperatures are not always consistent. These results will help to improve our understanding of the characteristics and variability of precipitation in arid regions within the context of climate warming.

Dry season intensity has equivocal effects on the nutritional condition of understory birds in a Neotropical forest

Abstract Rainfall regime, the amount and timing of annual precipitation, can influence the breeding phenology, individual fitness, and population dynamics of tropical birds. In Neotropical regions with rainfall seasonality (i.e. wet and dry seasons), the warm phase of the El Niño Southern Oscillation (ENSO) can exacerbate seasonal drought and negatively impact avian survival and reproduction. However, the mechanisms underlying associations between seasonal drought conditions and avian demography are largely unexplored. One hypothesis is that nutritional condition mediates demographic responses to seasonal drought: individuals in poor condition may be less capable of balancing their energy budgets and consequently suffer reduced survival, lower reproductive output, or both. We estimated nutritional condition (i.e. scaled mass index, percent hematocrit, plasma lipid metabolites) as a proxy of energy balance in understory forest birds with contrasting population-level responses to dry season length. This study took place across two dry seasons of differing intensity in central Panama: an El Niño dry season (2016, severe drought) and a more typical dry season (2017). Scaled mass index remained relatively constant throughout both dry seasons and across years for 5 common focal species and among 4 foraging guilds (22 additional species, 27 species total). Three of 5 focal species did exhibit reduced nutritional condition (i.e. lower hematocrit and/or higher β-hydroxybutyrate) during the El Niño dry season but not during the more typical dry season. However, foraging guilds did not show consistent nutritional responses to seasonal drought and we found little evidence of the reduced nutritional condition at the guild level, suggesting that many Neotropical forest bird species are capable of tolerating seasonal drought.

Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina

Abstract. The quantification of volumetric ice and water content in active rock glaciers is necessary to estimate their role as water stores and contributors to runoff in dry mountain catchments. In the semi-arid to arid Andes of Argentina, active rock glaciers potentially constitute important water reservoirs due to their widespread distribution. Here however, water storage capacities and their interannual changes have so far escaped quantification in detailed field studies. Volumetric ice and water content was quantified using a petrophysical four-phase model (4PM) based on complementary electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) in different positions of the Dos Lenguas rock glacier in the upper Agua Negra basin, Argentina. We derived vertical and horizontal surface changes of the Dos Lenguas rock glacier, for the periods 2016–2017 and 2017–2018 using drone-derived digital elevation models (DEMs). Interannual water storage changes of −36 mm yr−1 and +27 mm yr−1 derived from volumetric surface changes for the periods 2016–2017 and 2017–2018, respectively, indicate that significant amounts of annual precipitation can be stored in and released from the active rock glacier. Geophysical results show heterogeneous ice and water content with ice-rich permafrost and supra-, intra- and sub-permafrost water pathways at the end of the thaw period. Active layer and ice-rich permafrost control traps and pathways of shallow groundwater and thus regulate interannual storage changes and water releases from the active rock glaciers in the dry mountain catchment. The ice content of 1.7–2.0 × 109 kg in the active Dos Lenguas rock glacier represents an important long-term ice reservoir, as do other ground ice deposits in the vicinity, if compared to surface ice that covers less than 3 % of the high mountain catchment.