Variability Of Precipitation Amounts Research Articles

Precipitation amount and event intervals interact to change plant diversity during dry years in a desert shrubland

Variations in species diversity and soil properties in response to future climate change is a key focus area in ecological research. The influence of precipitation amount on plant community diversity and soil properties, in sandy desert ecosystems, is poorly studied. We chose the Artemisia ordosica community to examine how diversity, and the physical and chemical properties of soil vary in response to changes in precipitation. An in situ experimental platform was used to simulate total monthly precipitation at specific intervals in a desert-grassland region of northern China. The influence of precipitation on the community was investigated using three precipitation amount levels and two intervals. The relative density, coverage, and frequency of species in each experimental quadrat was analyzed for evaluating the community structure. Results showed that variability in precipitation amounts and intervals altered the species diversity in the A. ordosica communities. Increased precipitation amount enhanced whole community’s species diversity via improving the richness of perennial forbs. Lengthening the precipitation intervals enhanced whole community’s species diversity in the context of low precipitation amount but reduced species diversity in high precipitation amount condition. The precipitation patterns affected community species composition and diversity mainly by controlling soil moisture, secondly by changing the nitrogen and organic matter content of the surficial soils. This study revealed that effects of precipitation interval on the species diversity depended on annual precipitation amount and offer an innovative insight to evaluating the succession of desert ecosystems in the context of precipitation change in the future.

Minimizing surface run-off, improving underground water recharging, and on-site rain harvesting in the Kathmandu valley

Nepal’s political institutions and administrative units were thoroughly restructured in 2015 with the promulgation of the new Constitution. Several rural areas were combined to meet the definition of urban threshold criteria to classify rural areas into urban categories. Accordingly, over 3,900 local political and administrative units were amalgamated into 753 units, of which, 293 units are classified as urban. Within these newly defined urban areas, many natural environments have been converted into impervious surfaces such as paved roads, sidewalks, and building roofs. These impervious surfaces have drastically increased the amount of surface run-offs—often termed as “urban floods” --under increasing precipitation caused by global climate change. These incidences have negatively impacted to the groundwater recharge processes in the urban areas.
 Data on groundwater recharge rates are needed in the context of global climate change to understand the status of groundwater recharge processes in the urban areas of Nepal. However, due to various limitations, this study only focuses around the Kathmandu Valley of Nepal to understand: a) how the expansion of urban, peri-urban, and associated areas have resulted in decreasing groundwater recharges; b) how groundwater is affected by the year-to-year variability of precipitation amount (low and high intensity) with the conversion of the natural landscape into built-up areas; and c) how the changing trends in precipitation and evapotranspiration may impact future groundwater availability. This study is based on a review of the literature and the analysis of secondary data available from the government and various social media and authors' professional experiences. The study ends with some recommendations based on experiences from other parts of the world on groundwater recharge processes.

Suspended sediment yield and climate change in Kamchatka, Far East of Russia

Abstract. Key factors of sediment yield formation and variability in the Kamchatsky Krai are relief characteristics and climate (especially precipitation). The last research in climate change in Kamchatka demonstrates climate warming – mean annual air temperature has increased on 1.5 ∘C during the period from 1951 to 2009 in average (the maximum increase was revealed in the west of Kamchatka and in the Kamchatka River valley, the minimum one – in the extreme south and north). Decrease of annual precipitation was observed at the same period. In addition frequency and intensity of precipitation is growing. Thereby described climate changes in Kamchatka influence on sediment yield characteristics directly (influence of precipitation on surface washout formation) and indirectly (through water runoff and hydrological regime of rivers changes). Analysis of spatio-temporal variability in suspended sediment yield demonstrated decrease since late 1970–early 1980 in the most part of rivers in the Kamchatsky Krai. Revealed fluctuations demonstrate very good coincidence with precipitation amount variability. Decrease of precipitation leads to corresponding diminution of rainfall erosive factor in the territory which is the key factor of suspended sediment yield formation and variability in rivers in the Kamchatsky Krai. The value of reduction varies from 1 % to 45 % and involves decrease of erosion rates in the territory. Thereby climate change influences on suspended sediment yield in multiple-valued way. Income of friable volcanic deposits on the catchment surface is the key factor of suspended sediment yield formation and variability in some river basins under the impact of volcanic eruptions, and in combination with raising precipitation it can lead to catastrophic increase of sediment yield.

Strong Linkage Between Precipitation Intensity and Monsoon Season Groundwater Recharge in India

AbstractGroundwater is a lifeline for millions of people in India, which is affected by the year‐to‐year variability of precipitation amount and characteristics (low and high intensity). Precipitation intensity has been observed and projected to change in India. However, the crucial impact of precipitation intensity on groundwater recharge in India remains unknown. Here we use in situ data from more than 5,800 groundwater wells to show that precipitation intensity is strongly linked with groundwater recharge in India. In the northwest and north central India, the monsoon season groundwater recharge is linked with the low‐intensity precipitation, while in South India high‐intensity precipitation is a major driver of groundwater recharge. Observed long‐term changes in precipitation characteristics show a decline in the low‐intensity rain in the northwest and north central India that are strongly driven by sea surface temperature over the Pacific Ocean. Increases in the high‐intensity precipitation in South India are linked with the sea surface temperatures in the Atlantic Ocean. Our results highlight the importance of precipitation intensity for the monsoon season groundwater recharge in India, which can provide insights to sustainably manage rapidly declining groundwater resources in India.

Precipitation isoscapes for New Zealand: enhanced temporal detail using precipitation-weighted daily climatology

ABSTRACTPredictive understanding of precipitation δ2H and δ18O in New Zealand faces unique challenges, including high spatial variability in precipitation amounts, alternation between subtropical and sub-Antarctic precipitation sources, and a compressed latitudinal range of 34 to 47 °S. To map the precipitation isotope ratios across New Zealand, three years of integrated monthly precipitation samples were acquired from >50 stations. Conventional mean-annual precipitation δ2H and δ18O maps were produced by regressions using geographic and annual climate variables. Incomplete data and short-term variation in climate and precipitation sources limited the utility of this approach. We overcome these difficulties by calculating precipitation-weighted monthly climate parameters using national 5-km-gridded daily climate data. This data plus geographic variables were regressed to predict δ2H, δ18O, and d-excess at all sites. The procedure yields statistically-valid predictions of the isotope composition of precipitation (long-term average root mean square error (RMSE) for δ18O = 0.6 ‰; δ2H = 5.5 ‰); and monthly RMSE δ18O = 1.9 ‰, δ2H = 16 ‰. This approach has substantial benefits for studies that require the isotope composition of precipitation during specific time intervals, and may be further improved by comparison to daily and event-based precipitation samples as well as the use of back-trajectory calculations.

Climatology of Vb cyclones, physical mechanisms and their impact on extreme precipitation over Central Europe

Abstract. Cyclones, which develop over the western Mediterranean and move northeastward are a major source of extreme weather and known to be responsible for heavy precipitation over the northern side of the Alpine range and Central Europe. As the relevant processes triggering these so-called Vb events and their impact on extreme precipitation are not yet fully understood, this study focuses on gaining insight into the dynamics of past events. For this, a cyclone detection and tracking tool is applied to the ERA-Interim reanalysis (1979–2013) to identify prominent Vb situations. Precipitation in the ERA-Interim and the E-OBS data sets is used to evaluate case-to-case precipitation amounts and to assess consistency between the two data sets. Both data sets exhibit high variability in precipitation amounts among different Vb events. While only 23 % of all Vb events are associated with extreme precipitation, around 15 % of all extreme precipitation days (99 percentile) over the northern Alpine region and Central Europe are induced by Vb events, although Vb cyclones are rare events (2.3 per year). To obtain a better understanding of the variability within Vb events, the analysis of the 10 heaviest and lowest precipitation Vb events reveals noticeable differences in the state of the atmosphere. These differences are most pronounced in the geopotential height and potential vorticity field, indicating a much stronger cyclone for heavy precipitation events. The related differences in wind direction are responsible for the moisture transport around the Alps and the orographical lifting along the northern slopes of the Alps. These effects are the main reasons for a disastrous outcome of Vb events, and consequently are absent in the Vb events associated with low precipitation. Hence, our results point out that heavy precipitation related to Vb events is mainly related to large-scale dynamics rather than to thermodynamic processes.

The interannual variations spectra of precipitation amount on the South Сoast of Crimea

The amplitudes changes of various components of energy spectra of precipitation amount variability falling in Yalta and Feodosia which are calculated for the whole year, as well as for its cool and warm season are studied. It is shown that the SCC climate change occurred in the period from 1870 to 2013 led to substantial changes of considered energy spectra. It is shown that trends in the amplitudes of various components of the studied spectra depend on the geographical location of the observation points.

Estimating random errors of eddy covariance data: An extended two-tower approach

The incorporation of eddy covariance (EC) data in a land surface model (LSM) with help of data assimilation techniques requires a specification of the uncertainty of EC measurements. EC measurement uncertainty is composed of a systematic and random component. The systematic error is for example related to the energy balance (EB) closure, whereas the random error can be determined on the basis of differences between simultaneous flux measurements from two towers according to Hollinger and Richardson (2005) (Tree Physiol. 25, 873–885, here referred to as classical approach). The two-tower method, however, can be applied only where two towers share very similar environmental conditions. Here, we introduce an extended procedure to estimate the random error from EC data on the basis of the two-tower approach adapted for more heterogeneous environmental conditions. Our extended procedure consists of three main steps: (1) the EB deficit is corrected by distributing the deficit over the latent and sensible heat fluxes according to the evaporative fraction for each tower. This correction is based on the assumption that the EB deficit is due to an underestimation of the turbulent fluxes; (2) heterogeneity (e.g. different soil properties or vegetation characteristics and local variability in precipitation amounts) between two towers can introduce additional systematic flux differences. These differences can be corrected by normalizing turbulent fluxes at each tower according to the averaged evaporative fraction from two towers; (3) the random error can be determined following the two-tower approach using the normalized fluxes for the two towers. EC data from three different sites with different environmental conditions are used to test the classical and our extended approach: (1) three EC towers are placed at the Merken site, Germany and each of the three towers is surrounded by different vegetation types. This allows an evaluation on the basis of three different two-tower pairs. (2) two EC towers are located at the Roccarespampani site, Italy, with the same vegetation type around both towers. However, there are differences in vegetation age and density between these two towers; (3) for the Howland site, Maine, USA also data from two towers are available with very similar environmental conditions around the two towers. The random errors calculated by our extended approach are smaller than random errors from the classical approach, especially for larger net radiation (or large absolute fluxes). In addition, the random errors calculated by our extended approach result also in 9 out of 10 cases in less steep increases of the random error as function of flux magnitude (compared to the classical method). It was also found that atmospheric stability is an interesting alternative explanatory variable for random error of fluxes, which could be of special interest in the context of the extended two-tower approach. We conclude that our extended two-tower approach can be used to determine the random error of EC data for two towers located in more heterogeneous environmental conditions than aimed at by the original approach.

An entropy-based investigation into the variability of precipitation

Summary Employing the entropy concept spatial and temporal variability of precipitation time series were investigated for the State of Texas, USA. Marginal entropy was used to investigate the variability associated with monthly, seasonal and annual time series. Also, apportionment entropy and intensity entropy were used for investigating the intra-annual and decadal distributions of monthly and annual precipitation amounts and numbers of rainy days within a year and decade respectively. Finally, the Hurst exponent and the Mann–Kendall test were used to evaluate the long-term persistence and trend in the variability of precipitation. Distinct spatial patterns in annual series and different seasons were observed. The variability of precipitation amount as well as number of rainy days within a year increased from east to west of Texas. The results also indicated that highly disorderliness in the amount of precipitation and number of rainy days caused severe droughts during the 1950’s in whole of Texas.

Climatic hazards to the agricultural potential in the North China plain

Spring drought and summer flood and drought pose continuous threats to crop production in the North China Plain. High moisture stress during the spring is shown by the low ratios of actual evapotranspiration ( ET) to potential evapotranspiration ( PE). Uneven precipitation distribution, together with the low preseasonal soil moisture storage, is responsible for spring drought. Precipitation probability analysis for the months of May and June indicates only a 10–30% chance of an adequate moisture supply in this region during spring. Variability of precipitation amount and intensity share the responsibility for summer flood and drought. Precipitation probability alone for the months of July and August indicates that, on the average, the North China Plain has only a 30–50% chance of adequate moisture for crop growth. However, the probability of an optimum amount of precipitation decreases considerably when rain intensity is taken into consideration. Near the two centers of maximum intensity, in July and August, rainfall reaches 22–25 mm per rainy day. By comparison, growing-season precipitation in the winter wheat region of the Great Plains of the U.S.A. is less intense and more evenly distributed.