Long-term Precipitation Variability Research Articles

Productivity, water and nitrogen utilization of intensified dryland farming with annual forages on the Chinese Loess plateau

Understanding the relationships of productivity performance and water utilization and soil nitrogen dynamics after annual forage planting during the fallow period (F) in winter wheat (Triticum aestivum L.; W) mono-cropping is critically important for maintaining sustainable livestock and grain production in semiarid regions. We used 2 years (2017–2019) of data to investigate soil nitrogen dynamics, production, water utilization, and fallow efficiency when forage rape (Brassica campestris L.; R) and common vetch (Vicia sativa L.; V) were planted in a 3-month summer fallow of the W-F-W-F cropping system. Three cropping systems were comprised of winter wheat-summer fallow-winter wheat-summer fallow (W-F-W-F), winter wheat-forage rape-winter wheat-forage rape (W-R-W-R), and winter wheat-forage rape-winter wheat-common vetch (W-R-W-V). The results showed that the annual forage planting decreased the average NO3−-N content by 54.8% compared with the W-F-W-F cropping system. Compared with the W-F-W-F cropping system, planting annual forage in summer fallow increased the average system forage production by 4.93 t ha−1. Local total annual precipitation can meet crop-water requirements, and the limiting factor for agricultural production was the drought due to the uneven seasonal distribution of precipitation. In comparison to the W-F-W-F cropping system, annual forage planting decreased the average available soil moisture storage by 50.3 mm above the 80 cm soil layer. Compared with that in the W-R-W-R (23.21 t ha−1) and W-F-W-F (30.25 t ha−1) cropping systems, the crop productivity in the W-R-W-V cropping system (33.23 t ha−1) was relatively stable and high because the reduction in subsequent winter wheat yield (2.96 t ha−1) was adequately offset by the forage yield (5.15 t ha−1). Adding forage rape to the W-F-W-F cropping system decreased system crop-water productivity (CWP) by 40.9%. However, the CWP, precipitation use efficiency (PUE), and soil nitrate in the W-R-W-V cropping system increased by 30.4, 30.1, 110.9, and 82.0%, respectively, compared with those in the W-R-W-R cropping system. Therefore, the W-R-W-V cropping system is recommended for better water and fertility management as well as grain and forage production in semiarid regions. However, further study is required to involve drought years for better evaluation of the effect of long-term precipitation variability on the crop productivity.

K-Means and C4.5 Decision Tree Based Prediction of Long-Term Precipitation Variability in the Poyang Lake Basin, China

The machine learning algorithms application in atmospheric sciences along the Earth System Models has the potential of improving prediction, forecast, and reconstruction of missing data. In the current study, a combination of two machine learning techniques namely K-means, and decision tree (C4.5) algorithms, are used to separate observed precipitation into clusters and classified the associated large-scale circulation indices. Observed precipitation from the Chinese Meteorological Agency (CMA) during 1961–2016 for 83 stations in the Poyang Lake basin (PLB) is used. The results from K-Means clusters show two precipitation clusters splitting the PLB precipitation into a northern and southern cluster, with a silhouette coefficient ~0.5. The PLB precipitation leading cluster (C1) contains 48 stations accounting for 58% of the regional station density, while Cluster 2 (C2) covers 35, accounting for 42% of the stations. The interannual variability in precipitation exhibited significant differences for both clusters. The decision tree (C4.5) is employed to explore the large-scale atmospheric indices from National Climate Center (NCC) associated with each cluster during the preceding spring season as a predictor. The C1 precipitation was linked with the location and intensity of subtropical ridgeline position over Northern Africa, whereas the C2 precipitation was suggested to be associated with the Atlantic-European Polar Vortex Area Index. The precipitation anomalies further validated the results of both algorithms. The findings are in accordance with previous studies conducted globally and hence recommend the applications of machine learning techniques in atmospheric science on a sub-regional and sub-seasonal scale. Future studies should explore the dynamics of the K-Means, and C4.5 derived indicators for a better assessment on a regional scale. This research based on machine learning methods may bring a new solution to climate forecast.

Long-term precipitation monitoring and its linkage with flood scenario in changing climate conditions in Kashmir valley

The flood in Kashmir valley has a long history and is considered as recurrent phenomena, though the flood occurred in 2014 was extremely severe due to its extent, intensity and impact on mankind. To understand the variation of this precarious climatic condition, the long-term variability of precipitation over Kashmir valley was analysed over a period of 1901–2018 on an annual, seasonal, monthly and weekly basis to investigate the pattern of precipitation and its linkage to flooding. The mean annual precipitation analysis exhibits only few (06) severe incidences (>1226mm). Sen’s slope estimation exhibited a statistically positive trend during winter season (0.458 mm year−1) as compared to rainy season (-0.661 mm year−1) at the 5% level of significance. The major deficit (> −99%) in precipitation anomaly was recorded forming the September month as anomalous. September 2014 exceptionally confronted one incidence of sudden but continuous weekly high precipitation (>130 mm) with intensity of 22.82 mm day−1 during 15 years.

Quantifying long-term variability of precipitation and temperature over Zambia

A cursory or even detailed inspection of literature shows that while the annual cycle of precipitation and temperature in Zambia are well understood, there is a general lack of documentation on long term trends and periodicities over the country. In this study, we extensively examined the temporal and spatial changes in precipitation and temperature over Zambia for the period 1950–2016. We used the modified Mann–Kendall (m-MK) test with the aim of eliminating the effect of autocorrelation on precipitation and temperature trends based on Global Precipitation Climatology Centre (GPCC) and National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) products. Overall, significant decrease (increase) in precipitation (temperature) was evident. We further observed that, on average, precipitation has been decreasing by 1.1 mm yr−1. The highest drying rate was observed recently in the 2010s with a decrease of −24.4 mm/year. An abrupt change in the trend of precipitation was reported in 1980/1981 significant at 5% significance level. The highest amount in mean annual rainfall was 1093.5 mm reported in the 1960s while the lowest (966.4 mm) was reported in the 1990s. During the core of the rainy season, the western and southern provinces of the country are observed to generally experience negative rainfall anomalies implying more precipitation deficits in these areas. Temperature has been observed to be on the rise since the 1980s and no sudden changes have been observed in its trend over the country. Results further indicate that temperature has been increasing at a rate of 0.01 °C yr−1. The highest temperature increment (0.08 °C yr−1) was observed in the 2000s. Spatial analyses showed that temperature anomalies were positive across the whole country with higher anomalies being manifested in the 2000s and 2010s especially across North-eastern areas of the country. Findings embodied in this work provide a strong foundation for future climate monitoring and for studies that focus on examining extreme weather phenomena over Zambia.

Interannual and Long-Term Precipitation Variability Along the Subtropical Mountains and Adjacent Chaco (22–29° S) in Argentina

Recent studies documenting climate variability in South America have provided valuable information for understanding current and past dynamics of the climate system. Long meteorological records represent an essential tool to properly characterize climate fluctuations from decadal to multi–decadal scales. Unfortunately, the scarcity of continuous and homogeneous instrumental records is a major constraint to determine long–term variations in South America. Our knowledge of the forcings modulating the hydrological variability in mountains is still limited, despite their importance as freshwater sources for people living in the adjacent piedmonts and lowlands. The objective of this work is to determine the spatial–temporal variability of precipitation in the humid subtropical Andes and the Chaco region in North Western Argentina (NWA). Thirty– four rainfall records covering the common period 1934–1990, partially updated to 2016, were used to extend and identify the dominant patterns of seasonal to annual hydroclimatic variability based on principal components analysis. Intensity and frequency of droughts and pluvials (95th percentiles, respectively) were determined for the dominant patterns of variability. Our results show a positive trend in precipitation since 1970s in all temporal patterns and sub–regions. In addition, precipitation variability (both positive and negative extremes) increases during these last decades. Correlation analysis with sea–surface temperatures and wind anomalies during summer, reveal Amazon moisture sources and large–scale oceanic controls on NWA precipitation. The extended precipitation series shows that the frequency of pluvials has increased since the 1970s interrupted by few extreme droughts. This record can be considered representative of precipitation variations across NWA, including different environments in the Chaco, sub–Andes and Puna.

LONG-TERM VARIABILITY OF PRECIPITATION FORM IN HORNSUND (SPITSBERGEN) IN RELATION TO ATMOSPHERIC CIRCULATION (1979–2009)

The paper discusses the impact of the atmospheric circulation on the long-term variability of liquid, mixed and solid precipitation. The three precipitation forms were characterised by their totals, the number of days when they prevailed, and the contribution of each to the overall precipitation totals. Trends, as a background to further analysis, were calculated with regard to each characteristic of each precipitation form. The most significant increases were recorded in the contribution of liquid precipitation to the overall precipitation totals in September and in the mixed precipitation totals in December and November. Arctic Oscillation (AO) was found to have only a minor influence on the long-term variability of precipitation characteristics. The AO phase could to some degree account for the observed variation in the number of days with liquid precipitation. On the other hand, the direction of the local advection could account for considerably more of this variability and also the variability in liquid precipitation totals.

Characteristics of long-term variability of precipitation in selected river catchment areas in India based on GPCC data for the years 1901–2010

Characteristics of long-term variability of precipitation in selected river catchment areas in India based on GPCC data for the years 1901–2010

Characteristics of long-term variability of precipitation in the territory of Poland based on GPCC data for the years 1901–2010

Characteristics of long-term variability of precipitation in the territory of Poland based on GPCC data for the years 1901–2010

Influence of Precipitation Changes on the SPI and Related Drought Severity. An Analysis Using Long-Term Data Series

Drought indices, such as the Standardized Precipitation Index (SPI) are used to quantify drought severity. Due to the SPI probabilistic and standardized nature, a given value of SPI computed in distinct time periods or locations indicates the same relative drought severity but corresponds to different amounts of precipitation. Thus, the present study aims at contributing for a comprehensive analysis of the influence of long-term precipitation variability on drought assessment by the SPI. Long records of monthly precipitation, spanning from 1863 to 2007 in several locations across Portugal, were divided into 30 years sub-periods and the SPI with 12-month time scale (SPI-12) was computed for each sub-period and for the entire period of records. The probability distributions adjusted to precipitation in those different time periods were compared envisaging to detect the SPI sensitivity to the reference period and, therefore, to changes in precipitation. Precipitation thresholds relative to the upper limits of SPI-12 drought categories were obtained and the influence of the time period was investigated. Results have shown that when SPI values derived from the full data record for a recent time period are lower/higher than the SPI values derived from data of the considered time period a recent downward/upward shift of precipitation has occurred. Coherently, a common pattern of drought aggravation from the initial until the more recent period was not detected. However, in southern locations, lower precipitation thresholds of the SPI drought categories were generally found in the more recent period, particularly for more severe drought categories, whereas in the northern locations Porto and Montalegre, an increase was detected. The impacts of the reference period on the computed SPI drought severity and frequency are shown, bringing to discussion the need for updating ´normal´ conditions when long term precipitation records are available and precipitation changes are observed.

Scale-dependence of persistence in precipitation records

A statistical analysis of rainfall records over Europe compared with climate reconstructions based on sediment and pollen time series data suggests that proxy records can be reliable descriptors of long-term precipitation variability. Long-term persistence or Hurst–Kolmogorov behaviour has been identified in many hydroclimatic records1. Such time series are intriguing because they are the hallmark of multi-scale dynamical processes that govern the system from which they arise2. They are also highly relevant for water resource managers because these systems exhibit persistent, for example, multi-decadal, mean shifts or extremes clustering that must be included into any long-term drought management strategy. During recent years the growing number of palaeoclimatic reconstructions has allowed further investigation of the long-term statistical properties of climate3,4 and an understanding of their implications for the observed change5. Recently, the consistency of the proxy data for precipitation was strongly doubted, when their persistence property was compared to the corresponding estimates of instrumental records and model results6,7. The latter suggest that droughts or extremely wet periods occur less frequently than depicted in the palaeoclimatic reconstructions. Here, we show how this could be the outcome of a varying scaling law and present some evidence supporting that proxy records can be reliable descriptors of the long-term precipitation variability.

Long-term precipitation variability in the Ionian Islands, Greece (Central Mediterranean): climatic signal analysis and future projections

The present study examines the variability of the precipitation regime across the Ionian Islands complex, Greece (Central Mediterranean), for a period spanning more than one century. Significant negative long-term linear trends in the annual precipitation totals are observed, more pronounced in the southern parts of the studied area, while a climatic discontinuity possibly occurred during the 1970s, manifested first in the southern Ionian. Statistically significant nonlinear trends and subdecadal intermittent oscillations were detected using Monte Carlo singular spectral analysis. The correlation of the winter precipitation variability at Ionian complex with the North Atlantic Oscillation anomalies was also investigated and extended in the frequency domain. Finally, future projections were performed using an ensemble of Regional Climatic Models. Model simulations suggested a decrease of the order of ∼20% or more in the mean annual precipitation of the area by the end of the century.

Long-Term Variability of Precipitation form in Hornsund (Spitsbergen) in Relation to Atmospheric Circulation (1979–2009)

Abstract The paper discusses the impact of the atmospheric circulation on the long-term variability of liquid, mixed and solid precipitation. The three precipitation forms were characterised by their totals, the number of days when they prevailed, and the contribution of each to the overall precipitation totals. Trends, as a background to further analysis, were calculated with regard to each characteristic of each precipitation form. The most significant increases were recorded in the contribution of liquid precipitation to the overall precipitation totals in September and in the mixed precipitation totals in December and November. Arctic Oscillation (AO) was found to have only a minor influence on the long-term variability of precipitation characteristics. The AO phase could to some degree account for the observed variation in the number of days with liquid precipitation. On the other hand, the direction of the local advection could account for considerably more of this variability and also the variability in liquid precipitation totals.

Long-term precipitation variability on thunderstorm days in Poland (1951–2000)

The paper discusses the frequency of precipitation, broken down into amount categories, on thunderstorm days in Poland during the period 1951–2000. The authors looked at the number of thunderstorm days with precipitation versus the total thunderstorm days. Frequencies of certain precipitation totals on thunderstorm days were determined for various Polish regions, as well as long-term and annual precipitation variabilities. Daily precipitation and thunderstorm observation records from 47 Polish weather stations were used in the study. Precipitation on thunderstorm days was broken down into the following categories: dry day or trace precipitation, 0.1–10.0 mm, 10.1–20.0 mm, 20.1–30.0 mm, and more than 30.0 mm. These categories were studied for variability in five thunderstorm regions in Poland. The study revealed at that precipitation occurred on most of the thunderstorm days in the second half of the 20th century in Poland (on average 85% of cases). On 63% of thunderstorm days there was between 0.1 and 10.0 mm of rain. Cases of more than 30.0 mm of precipitation were very rare (2.7%) and were recorded mostly in mountainous areas. Annual frequencies of the various precipitation categories were similar across all of the regions. There was more variability in the long-term view, but in most cases no clear trend could be established. Slight decrease in number of thunderstorm days without precipitation (statistically significant in regions II and III) and an increase in days with the lowest precipitation, 0.1–10.0 mm (statistically significant in region V) was stated.

Trend analysis of Icelandic discharge, precipitation and temperature series

This study is a part of a Nordic co-operative research project, Climate and Energy, funded by Nordic Energy Research and the Nordic energy sector. The project has the objective of a comprehensive assessment of the impact of climate change on Nordic renewable energy resources including hydropower, wind power, biofuels and solar energy. In this paper, the long term variability of precipitation, temperature and discharge of Icelandic rivers is analyzed with respect to trends. Trend is tested for two periods: 1941–2002, since the longest Icelandic discharge records reach 60 years back in time, and 1961–2000, so that a larger set of discharge records could be included, as only a few Icelandic discharge records extend more than 40 years back in time. An eventual trend in the time series is analyzed using the Mann–Kendall test. The test is applied to the time series of both annual and seasonal values, and also to the timing and volume of the maximum daily discharge in spring and autumn, respectively. The main conclusions from the study are that, despite significant increase in measured precipitation, discharge in non-glacial rivers has not increased. Meanwhile, spring temperatures have a negative trend and spring floods, therefore, are larger and delayed.

Seasonal, interannual and long-term variability of precipitation and snow depth in the region of the Barents and Kara seas

Seasonal, interannual and long-term variability of precipitation and snow depth in the region of the Barents and Kara seas

Seasonal, interannual and long-term variability of precipitation and snow depth in the region of the Barents and Kara seas

Observation data of temperature, precipitation and snow depth have been compiled and generalized climatologically for a network of 38 stations in and around the Barents and Kara seas, for the period 1951–1992. The monthly precipitation totals were corrected for measuring errors, and the correction method is described in detail. The corrected precipitation values show that the annual precipitation in the region ranges from more than 500 mm along the coast of the Kola Peninsula to less than 200 mm in parts of the north-eastern Kara Sea. The solid fraction of the annual precipitation ranges from 70 % in northern parts to 35 % in southern parts. For the period 1951–1992 the analysis indicates decreasing trends in annual values of temperature, precipitation and snow depths in the north-eastern parts of the region.

Seasonal, interannual and long-term variability of precipitation and snow depth in the region of the Barents and Kara seas

Seasonal, interannual and long-term variability of precipitation and snow depth in the region of the Barents and Kara seas

Long-term precipitation variability in Morocco and the link to the large-scale circulation in recent and future climates

Summary Monthly precipitation data from the Global Historical Climatology Network for 42 stations in Morocco and its vicinity are investigated with respect to baroclinicity, storm track and cyclone activity, moisture transports, North Atlantic Oscillation (NAO) variations, and different circulation types by means of correlation and composite studies. The results are related to a climate change scenario from an ECHAM4=OPYC3 transient greenhouse gas only (GHG) simulation. Precipitation in northwestern Morocco shows a clear link to the baroclinic activity over the North Atlantic during boreal winter (DJF). In large precipitation months the North Atlantic storm track is shifted southward, more westerly and northwesterly circulation situations occur and moisture transports from the Atlantic are enhanced. The occurrence of local cyclones and upper-level troughs is more frequent than in low precipitation months. The negative correlation to the NAO is relatively strong, especially with Gibraltar as a southern pole ( � 0.71). The northward shift of the storm track and eastward shift of the Azores High predicted by the ECHAM model for increasing GHG concentrations would therefore be associated with decreasing precipitation and potentially serious impacts for the future water supply for parts of Morocco. In the region south of the Atlas mountains, moisture transports from the Atlantic along the southern flank of the Atlas Mountains associated with cyclones west of Morocco and the Iberian Peninsula can be identified as a decisive factor for precipitation. Northeastern Morocco and Northwestern Algeria, however, is rather dominated by the influence of cyclones over the Western Mediterranean that are associated with a strong northwesterly moisture transport. As both regions appear to be less dependent on the North Atlantic storm track and more on local processes, a straight forward interpretation of the large-scale changes predicted by the ECHAM4=OPYC3 cannot be done without the application of down-scaling methods in the future.

The Response of Soil Moisture to Long-Term Variability of Precipitation

Abstract Soil hydrology is a widely recognized low-pass filter for the interaction between land and atmosphere. However, the lack of adequate long-term measured data on soil moisture profiles has precluded examination of how soil wetness responds to long-term precipitation variations. Such a response can be characterized by its amplitude damping, phase shifting, and increasing persistence with soil depth. These should be correlated with the climate spectra through the interactions between the land and the atmosphere. The major objective of this study is to investigate how precipitation signals are manifested in vertical soil moisture profiles in the context of timescales. Thus, the natural variability of soil moisture profiles is documented using 16 yr of field observational data of soil moisture measured at 11 levels of various depths down to 2.0 m at 17 locations over Illinois. Detailed statistic analyses are made of the temporal variations of soil moisture profiles and concurrently measured precipitati...

Temporal and Spatial Characteristics of Heavy-Precipitation Events in the Midwest

Long-term (1921–90) daily precipitation data from 242 stations were used to identify heavy multiday precipitation events (exceeding the threshold for a 1-yr recurrence interval) that were found to be closely related to flood events. The number of events were aggregated over 5-yr (pentad) periods and compared with total pentad precipitation. Although a strong positive correlation was found, this was due entirely to the event contributions to the total precipitation. When event precipitation was subtracted from total precipitation, no statistically significant correlation was found. The frequency distribution of precipitation totals in nonevent weeks was also found to be similar in years with few or no events compared to years with several events. These findings suggest that the occurrence of these events is not strongly linked to longer-term persistent climate anomalies. These relatively few events make an important contribution to long-term precipitation variability, accounting for about half of the interpentadal variability. To provide information for determining hydrologic impacts from the results of GCMs, a study of spatial precipitation variability during heavy events was undertaken. For each event at each station, grid-average precipitation was calculated for 2° latitude × 2.5° longitude, and 4° latitude × 5° longitude grid cells. The ratio of grid average to heavy-event precipitation totals was determined. These relationships could be used to assess the probability of flood-producing, localized precipitation extremes from GCM grid-average precipitation.