scholarly journals Quantifying and reducing researcher subjectivity in the generation of climate indices from documentary sources

2021 ◽  
Author(s):  
George Adamson ◽  
David Nash ◽  
Stefan Grab
Keyword(s):  
Southern Africa ◽  
Climatic Variability ◽  
Intraclass Correlation ◽  
Annual Rainfall ◽  
Climate Indices ◽  
Documentary Sources ◽  
Rainfall Index ◽  
Central Value ◽  
Related Discipline ◽  
Back Calculation

Abstract. The generation of index-based series of meteorological phenomena, derived from narrative descriptions of weather and climate in historical documentary sources, is a common method to reconstruct past climatic variability. This study is the first to explicitly examine the degree of inter-rater variability in producing such series, a potential source of bias in index-based analyses. Two teams of raters were asked to produce a five-category annual rainfall index series for the same dataset, consisting of transcribed narrative descriptions of meteorological variability for 11 ‘rain-years’ in nineteenth-century Lesotho, originally collected by Nash and Grab (2010). One group of raters (n = 71) comprised of students studying for postgraduate qualifications in climatology or a related discipline; the second group (n = 6) consisted of professional meteorologists and historical climatologists working in southern Africa. Inter-rater reliability was high for both groups, at r = 0.99 for the student raters and r = 0.94 for the professional raters, although ratings provided by the student group disproportionately averaged to the central value (0: normal/seasonal rains) where variability was high. Back-calculation of intraclass correlation using the Spearman-Brown prediction formula showed that a target reliability of 0.9 could be obtained with as few as eight student raters, and four professional raters. This number reduced to two when examining a subset of the professional group (n = 4) who had previously published historical climatology papers on southern Africa. We therefore conclude that variability between researchers should be considered minimal where index-based climate reconstructions are generated by trained historical climatologists working in groups of two or more.

Climatic variability and change over southern Africa: a reflection on underlying processes

1997 ◽  
Vol 21 (1) ◽  
pp. 23-50 ◽  
Author(s):  
S.J. Mason ◽  
M.R. Jury
Keyword(s):  
Southern Africa ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Climatic Variability ◽  
Sea Surface ◽  
Annual Rainfall ◽  
Eastern Equatorial Pacific ◽  
Moisture Fluxes ◽  
Sea Surface Temperature Anomalies

Quasi-periodicities in annual rainfall totals over southern Africa have been identified; in particular, an approximately 18-year cycle may be related to interdecadal variability in sea-surface temperatures in the eastern equatorial Pacific and central Indian Oceans. A 10-year cycle along the south coast is related to variability in standing wave 3. Atmospheric anomalies associated with wet and dry years can be related to changes in the frequency, intensity and persistence of important rainfall-producing weather systems and highlight the significance of the strength of the continental heat low and the preferred locations and amplitudes of the westerly troughs. El Niño Southern Oscillation events and sea-surface temperature anomalies in the Indian and South Atlantic Oceans can influence both the tropical and the temperate atmospheric circulation and moisture fluxes over the subcontinent and thus are significant influences on rainfall variability. Evidence for long-term climatic change is not as definitive as in the Sahel, although there are indications of desiccation in some areas since the late-1970s. Increases in temperatures are of approximately the same magnitude as the hemispheric trends and may be attributable to the enhanced greenhouse effect.

A Note on Rainfall Variability and Trends in Nigeria: Implications for Agricultural Production*

2021 ◽  
pp. 232102222110514
Author(s):  
Kolawole Ogundari ◽  
Adebola Abimbola Ademuwagun ◽  
Ogechukwu Appah
Keyword(s):  
Food Security ◽  
Coefficient Of Variation ◽  
Agricultural Production ◽  
Hypothesis Test ◽  
Rainfall Variability ◽  
Climatic Variability ◽  
Least Square ◽  
Annual Rainfall ◽  
Average Annual Rainfall ◽  
Over Time

The climatic change crisis has led to a renewed interest in understanding the dynamic of climatic variability over time. This is because rainfall variability in response to climate change poses a severe threat to global food security and agricultural production in general. As a result of this, the study investigates the convergence of rainfall variability in Nigeria. We use historical climate data on annual rainfall collected from meteorological stations across 12 states and covering 1992–2013. This gives rise to a balanced panel data of 12 states and 20 periods, which yields 240 observations. The study used a sigma convergence hypothesis test estimated using ordinary least square, fixed-effect and feasible generalized least square models. The coefficient of variation is taken as a measure of rainfall variability in the study. The results showed a negative (declining) linear correlation between rainfall’s coefficient of variation and data year. This means that rainfall variability decreased over time. This indicates evidence of convergence of rainfall, which means states with lower average annual rainfall are catching up on states with higher average annual rainfall over time. And, from the agricultural production standpoint, this result shows that the potential threat of rainfall variability to food security is not severe. In addition, it indicates a decrease in risk and uncertainty in food crop production associated with rainfall variability. JEL Classifications: O13, O55, Q10, Q54

scholarly journals Modelling persistence in annual Australia point rainfall

2003 ◽  
Vol 7 (2) ◽  
pp. 197-211 ◽  
Author(s):  
J. P. Whiting ◽  
M. F. Lambert ◽  
A. V. Metcalfe
Keyword(s):  
Markov Model ◽  
Strong Evidence ◽  
Markov Models ◽  
Southern Oscillation ◽  
Mixture Distribution ◽  
Simulation Models ◽  
Annual Rainfall ◽  
Climate Indices ◽  
Rainfall Time Series ◽  
Fractional Differencing

Abstract. Annual rainfall time series for Sydney from 1859 to 1999 is analysed. Clear evidence of nonstationarity is presented, but substantial evidence for persistence or hidden states is more elusive. A test of the hypothesis that a hidden state Markov model reduces to a mixture distribution is presented. There is strong evidence of a correlation between the annual rainfall and climate indices. Strong evidence of persistence of one of these indices, the Pacific Decadal Oscillation (PDO), is presented together with a demonstration that this is better modelled by fractional differencing than by a hidden state Markov model. It is shown that conditioning the logarithm of rainfall on PDO, the Southern Oscillation index (SOI), and their interaction provides realistic simulation of rainfall that matches observed statistics. Similar simulation models are presented for Brisbane, Melbourne and Perth. Keywords: Hydrological persistence,hidden state Markov models, fractional differencing, PDO, SOI, Australian rainfall

scholarly journals Coherent response of lakes in Ontario, Canada to reductions in sulphur deposition: the effects of climate on sulphate concentrations

2003 ◽  
Vol 7 (4) ◽  
pp. 583-595 ◽  
Author(s):  
P. J. Dillon ◽  
K. M. Somers ◽  
J. Findeis ◽  
M. C. Eimers
Keyword(s):  
Repeated Measures ◽  
Hydrological Cycle ◽  
Southern Oscillation ◽  
Intraclass Correlation ◽  
Temporal Trends ◽  
Temporal Coherence ◽  
Major Influence ◽  
Climate Indices ◽  
Sulphur Deposition ◽  
South Central

Abstract. Sulphate deposition in south-central Ontario declined between 1976 and 2000 by more than 50%, whereas lake sulphate (SO42–) concentrations decreased by, on average, only half as much. To investigate the factors that controlled this slower than expected response, the temporal patterns in lake SO42– concentrations were compared with patterns in both deposition and climate, since climate has a major influence on the hydrological cycle in this part of the continent. To do this, the temporal coherence in SO42– concentrations between 9 lake basins was estimated using the intraclass correlation from a repeated-measures analysis of variance and two subsets of lakes were found (six in one group, four in the other), each with lakes having synchronous patterns. One subset (4 lakes) included the 3 with the longest water replenishment times (>3.4 yr) which are expected to respond to decreases in SO42– deposition more slowly. However, the average pattern reflecting the temporal changes of each of the two subsets was very similar. The response of both subsets of lakes to the decreasing SO42– deposition over two decades was independent of the degree of acidification or sensitivity to acidification of the lakes. In a determination of which factors best predicted each of those two subsets’ SO42– time series, good predictive models were produced by regional/global-scale climate indices, specifically the Southern Oscillation Index (SOI) describing the El Niño Southern Oscillation (ENSO) and the North Atlantic Oscillation Index (NAOI), as well as by SO42– deposition indices. When the predictor variables were combined, models which described the long-term changes in lake SO42– concentration best included the SOI, the NAOI and SO42– deposition. Thus, large-scale climate factors play a major role in determining the response of aquatic systems to changes in SO42– deposition, perhaps through their influence on lake and/or catchment processes that effectively delay recovery. Keywords: Atmospheric deposition, lake recovery, temporal trends, climate, temporal coherence

scholarly journals Bioclimatic zonation and potential distribution of Spodoptera frugiperda (Lepidoptera: Noctuidae) in South Kivu Province, DR Congo

BMC Ecology ◽  
2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Marcellin C. Cokola ◽  
Yannick Mugumaarhahama ◽  
Grégoire Noël ◽  
Espoir B. Bisimwa ◽  
David M. Bugeme ◽  
...  
Keyword(s):  
Spodoptera Frugiperda ◽  
Potential Distribution ◽  
Climatic Variability ◽  
Crop Damage ◽  
Annual Rainfall ◽  
Mean Annual Temperature ◽  
Dr Congo ◽  
Dispersal Capacity ◽  
Jackknife Test ◽  
South Kivu

Abstract Background The fall Armyworm (FAW) Spodoptera frugiperda (JE Smith), is currently a devastating pest throughout the world due to its dispersal capacity and voracious feeding behaviour on several crops. A MaxEnt species distributions model (SDM) was developed based on collected FAW occurrence and environmental data’s. Bioclimatic zones were identified and the potential distribution of FAW in South Kivu, eastern DR Congo, was predicted. Results Mean annual temperature (bio1), annual rainfall (bio12), temperature seasonality (bio4) and longest dry season duration (llds) mainly affected the FAW potential distribution. The average area under the curve value of the model was 0.827 demonstrating the model efficient accuracy. According to Jackknife test of variable importance, the annual rainfall was found to correspond to the highest gain when used in isolation. FAWs’ suitable areas where this pest is likely to be present in South Kivu province are divided into two corridors. The Eastern corridor covering the Eastern areas of Kalehe, Kabare, Walungu, Uvira and Fizi territories and the Western corridor covering the Western areas of Kalehe, Kabare, Walungu and Mwenga. Conclusions This research provides important information on the distribution of FAW and bioclimatic zones in South Kivu. Given the rapid spread of the insect and the climatic variability observed in the region that favor its development and dispersal, it would be planned in the future to develop a monitoring system and effective management strategies to limit it spread and crop damage.

scholarly journals Analysis of a Sahelian annual rainfall index from 1896 to 2000; the drought continues

2002 ◽  
Vol 47 (4) ◽  
pp. 563-572 ◽  
Author(s):  
YANN L'HÔTE ◽  
GIL MAHÉ ◽  
BONAVENTURE SOMÉ ◽  
JEAN PIERRE TRIBOULET
Keyword(s):  
Annual Rainfall ◽  
Rainfall Index

scholarly journals Spatial and Temporal Analysis of Drought in Nepal using Standardized Precipitation Index and its Relationship with Climate Indices

1970 ◽  
Vol 7 (1) ◽  
pp. 59-74 ◽  
Author(s):  
M Sigdel ◽  
M Ikeda
Keyword(s):  
Principal Component Analysis ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Standardized Precipitation Index ◽  
Principal Component ◽  
Component Analysis ◽  
Precipitation Index ◽  
Climate Indices ◽  
Indian Ocean Dipole Mode ◽  
Time Space

Drought over Nepal is studied on the basis of precipitation as a key parameter. Using monthly mean precipitation data for a period of 33 years, Standardized Precipitation Index (SPI) is produced for the drought analysis with the time scale of 3 months (SPI-3) and 12 months (SPI-12) as they are applicable for agriculture and hydrological aspects, respectively. Time-space variability is explored based on Principal Component Analysis (PCA) along with Rotated PCA (RPCA). Four rotated components were explored for both SPI-3 and SPI-12 representing climatic variability with cores over eastern, central and western Nepal separately. Droughts associated with SPI-3 occurred almost evenly over these regions. Droughts associated with SPI-12 were consistent with SPI-3 for summer, since summer precipitation dominates annual precipitation. Connection between SPI and the climate indices such as Southern Oscillation Index (SOI) and Indian Ocean Dipole Mode Index (DMI) was studied, suggesting that one of the causes for summer droughts is El Nino, while the winter droughts could be related with positive DMI. Keywords: Standardized Precipitation Index; Nepal; Principal component analysis; Drought DOI: http://dx.doi.org/10.3126/jhm.v7i1.5617 JHM 2010; 7(1): 59-74

Temperature and precipitation projections for Poland based on downscaled EuroCORDEX ensemble

2020 ◽  
Author(s):  
Joanna Struzewska ◽  
Maciej Jefimow ◽  
Paulina Jagiełło ◽  
Maria Kłeczek ◽  
Anahita Sattari ◽  
...  
Keyword(s):  
Regional Climate ◽  
Annual Rainfall ◽  
Maximum Temperature ◽  
Climate Indices ◽  
Climate Projections ◽  
Spatial And Temporal Variability ◽  
Climate Change Scenarios ◽  
North East ◽  
The North ◽  
Temperature And Precipitation

<p>Regional climate projections are necessary to assess possible changes in the exposure and risk to allow planning the adaptation strategies.</p><p>Projections of temperature and precipitation trends were developed using a consistent methodology and homogeneous datasets to address the needs of up-to-date climate change scenarios for Poland.</p><p>The Euro-Cordex results with the resolution of 0.11deg (about 12.5km) for RCP4.5 and RCP8.5 were downscaled based on various historical gridded datasets (EOBS, ERA5, UERRA and data from IMWM).</p><p>Ensemble analysis was undertaken to assess the projection uncertainty and ensemble mean were calculated for base parameters (daily average, minimum, and maximum temperature and daily precipitation sum) as well as for the number of climate indices.</p><p>We will present spatial and temporal variability of selected climate indices over Poland for subsequent decades. Increase of the annual average temperature is due to the rise in the number of hot days and the reduction of the number of frost days. All temperature indices are characterized by statistically significant trends, strongest for RCP8.5. The most pronounced changes in the frequency and amount of precipitation occur in the north-east of Poland. The total number of days with precipitation increases slightly. The increase in the annual rainfall is due to the increase in the number of days with extreme precipitation.</p><p>Results are presented via an interactive web portal. Further analysis includes the development of projection for solar radiation, wind speed, humidity and snow cover.</p>

scholarly journals Climatic information of Western Sahel (1535–1793 AD) in original documentary sources

2014 ◽  
Vol 10 (5) ◽  
pp. 3877-3900 ◽  
Author(s):  
V. Millán ◽  
F. S. Rodrigo
Keyword(s):  
18Th Century ◽  
Climatic Conditions ◽  
Ordinal Scale ◽  
Annual Rainfall ◽  
Minor Importance ◽  
Documentary Sources ◽  
Western Sahel ◽  
Dry Conditions ◽  
Droughts And Floods ◽  
Original Documentary

Abstract. The Sahel is the semi-arid transition zone between arid Sahara and humid tropical Africa, extending approximately 10–20° N from Mauritania in the West to Sudan in the East. The African continent, one of the most vulnerable regions to climate change, is subject to frequent droughts and famine. One climate challenge research is to isolate those aspects of climate variability that are natural from those that are related to human influences. Therefore, the study of climatic conditions before mid-19th century, when anthropogenic influence was of minor importance, is very interesting. In this work the frequency of extreme events, such as droughts and floods, in Western Sahel from the 16th to 18th centuries is investigated using documentary data. Original manuscripts with historical chronicles from Walata and Nema (Mauritania), Timbuktu and Arawan (Mali), and Agadez (Niger) have been analyzed. Information on droughts, intense rainfall, storms and floods, as well as socioeconomic aspects (famines, pests, scarcity, prosperity) has been codified in an ordinal scale ranging from −2 (drought and famines) to +2 (floods) to obtain a numerical index of the annual rainfall in the region. Results show wet conditions in the 17th century, as well as dry conditions in the 18th century (interrupted by a short wet period in the 1730s decade).

scholarly journals Vulnerability of Calabar Rainfall to Climatic Variability Events: A Critical Factor in Integrated Water Resources Management in the Tropical Coastal Location in Southeastern Nigeria

2021 ◽  
Vol 16 (1) ◽  
pp. 115-122
Author(s):  
Solomon O. Amadi ◽  
Mfongang E. Agbor ◽  
Sunday O. Udo
Keyword(s):  
Water Resources ◽  
Water Resources Management ◽  
Rainfall Variability ◽  
Climatic Variability ◽  
Standardized Precipitation Index ◽  
Annual Rainfall ◽  
Least Squares Regression ◽  
Southeastern Nigeria ◽  
Resources Management ◽  
Dry Spell

In this study, Calabar annual total rainfall was analysed for trend and climatic variability events with focus on drought occurrence. Monthly rainfall data from in situ measurements over a 41 year period (1972-2012) were used for the study. Standard tests were used to evaluate the trends and variability in annual rainfall. Rainfall variability was estimated as standardized rainfall departures and used to identify and delimitate the dry and wet spell sequences of Calabar rainfall. The rainfall series were analysed for Standardized Precipitation Index (SPI) using SPSS Version 17 software. The least squares regression plot was executed using Excel 2010 to depict the trend, variability and regression parameters. The average annual rainfall for Calabar is 2984.64 mm with standard deviation of 394.9 mm. 36.59% of the period showed positive SPI while 63.41 % of the period indicated negative SPI values. Wet spell dominated the later part of the period but sandwiched with dry spells whereas dry spell were dominant from 1972 to 1994. The area experienced a non-significant upward trend of 15.21 mm per year over the interval. The SPI values indicate that Calabar experienced distinct inter-annual rainfall cycles that represent mild to extreme droughts and wet spells which are a demonstration of consequential annual rainfall variability. The results underscore the need for effective monitoring of Calabar rainfall for prompt warnings and responses that would guarantee effective risk reduction and management in the run-in to the occurrence of the extreme events. The paper further highlights the need for data-driven approach to policy making in water resources management. This would provide a fascinating insight into the improvement in long-term water resources management in the city and its suburbs.

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