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1

Climate indices and drought characteristics in the river catchments of Western Ghats of India

Shetty Swathi, Umesh Pruthviraj, Shetty Amba

Acta Geophysica

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2024

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Vol. 72, no. 1

371--384

EN

The study addresses the long-term trend in rainfall, minimum and maximum temperature, and the climate indices for the river catchments located in the diverse climate of the Western Ghats of India. The dry sub-humid Chaliyar catchment and humid Kajvi catchment have shown a dramatic change in the decadal rainfall, with the decade 1950-1960 being the point of change. The monsoon rainfall has decreased in the Chaliyar and Netravati catchments and increased insignificantly in the Kajvi catchment. With the increase in mean temperature, the number of rainy days is decreasing, and intense rainfall is increasing in the pre-monsoon. The increase in minimum temperature is more severe in all three catchments, irrespective of the region’s climate. The decline in rainy days is more figurative in the humid and per-humid catchments and has seen a 16-20% decrease in Rx 1 day, Rx 3 day, and Rx 5 day in the past six decades with an insignificant increase in the dry subhumid catchment. The frightful increase in warm days/nights with a decrease in cool days/nights has been alarming for the extremity of temperature in future years. The significant changes in the forest area in Chaliyar and Kajvi catchment and the increase in a built-up area in Netravati may have a decisive role in the nonseasonal variability in rainfall and temperature along with increasing greenhouse gases. In the case of meteorological drought studied using the Standardized Precipitation Index (SPI), moderate droughts have occurred over the Chaliyar and Kajvi, and extreme droughts over the Netravati catchments with no reduction in the frequency or severity of short-duration extreme rainfall events. The geographical location of the catchment has a greater impact on the characteristics of the rainfall and meteorological drought, and these changes in the hydrological regimes of the catchment have a significant bearing on the water availability in the catchments in the future years.

2

Analyzing trend and forecast of rainfall and temperature in Valmiki Tiger Reserve, India, using non parametric test and random forest machine learning algorithm

Roshani, Sajjad Haroon, Saha Tamal Kanti, Rahaman Md Hibjur, Masroor Md, Sharma Yatendra, Pal Swades

Acta Geophysica

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2023

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Vol. 71, no. 1

531--552

EN

Assessment of spatiotemporal dynamics of meteorological variables and their forecast is essential in the context of climate change. Such analysis can help suggest possible solutions for flora and fauna in protected areas and adaptation strategies to make forests and communities more resilient. The present study attempts to analyze climate variability, trend and forecast of temperature and rainfall in the Valmiki Tiger Reserve, India. We utilized rainfall and temperature gridded data obtained from the Indian Meteorological Department during 1981–2020. The Mann–Kendall test and Sen’s slope estimator were employed to examine the time series trend and magnitude of change at the annual, monthly and seasonal levels. Random forest machine learning algorithm was used to estimate seasonal prediction and forecasting of rainfall and temperature trend for the next ten years (2021–2030). The predictive capacity of the model was evaluated by statistical performance assessors of coefficient of correlation, mean absolute error, mean absolute percentage error and root mean squared error. The findings revealed a significant decreasing trend in rainfall and an increasing trend in temperature. However, a declining trend for maximum temperature has been observed for winter and post-monsoon seasons. The results of seasonal forecasting exhibited a considerable decrease in rainfall and temperature across the Reserve during all the seasons. However, the temperature will increase during the summer season. The random forest machine learning algorithm has shown its effectiveness in forecasting the temperature and rainfall variables. The findings suggest that these approaches may be used at various spatial scales in different geographical locations.

3

Assessment of evidence based climate variability in Bhagirathi sub basin of India: a geostatistical analysis

Rehman Sufa, Sajjad Haroon, Masroor Md, Rahaman Md Hibjur, Roshani, Ahmed Raihan, Sahana Mehebub

Acta Geophysica

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2022

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Vol. 70, no 1

445--463

EN

Climate variability analysis is essential for predicting the behavior of various extreme weather events and making communities resilient. Notwithstanding the profound concerns, climate variability assessment faces numerous challenges due to inadequate and sometimes unavailability of data at spatiotemporal scales. This study makes an attempt to analyse climate variability in the Bhagirathi Sub-basin of India. Six meteorological variables were analysed from fourteen weather stations located in the Sub-basin during 1968–2017. Modified Mann–Kendall test was employed to ascertain the trends in meteorological variables. One-way ANOVA was used to assess the relationship between and within the variables. A total of 432 households were selected for reaffirming climate variability and impact on landscape. Significant trends were detected in highest maximum, mean maximum (Mmax) and mean minimum (Mmin) temperatures, relative humidity (Rh), rainfall and vapour pressure (Vp) at annual and seasonal scales. Stations located in eastern and deltaic Sub-basins registered varying trends in these meteorological variables due to anthropogenic activities-induced land use changes. ANOVA revealed a robust relation among rainfall, Vp, Mmin and Mmax. Perceptions of the sampled households revealed that climate variability has considerably affected food intensity, vegetation, soil, water resources and agricultural pattern. We find modified Mann– Kendall method effective in analysing climate variability in the Sub-basin. Thus, this method can be utilized for effective analysis of climate variability at spatial scales in geographical regions.

4

Seasonality shift and streamfow fow variability trends in central India

Kuriqi Alban, Ali Rawshan, Pham Quoc Bao, Montenegro Gambini Julio, Gupta Vivek, Malik Anurag, Linh Nguyen Thi Thuy, Joshi Yogesh, Anh Duong Tran, Nam Thai Van, Dong Xiaohua

Acta Geophysica

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2020

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Vol. 68, no. 5

1461--1475

EN

A better understanding of intra/inter-annual streamfow variability and trends enables more efective water resources planning and management for current and future needs. This paper investigates the variability and trends of streamfow data from fve stations (i.e. Ashti, Chindnar, Pathgudem, Polavaram, and Tekra) in Godavari river basin, India. The streamfow data were obtained from the Indian Central Water Commission and cover more than 30 years of mean daily records (i.e. 1972–2011). The streamfow data were statistically assessed using Gamma, Generalised Extreme Value and Normal distributions to under stand the probability distribution features of data at inter-annual time-scale. Quantifable changes in observed streamfow data were identifed by Sen’s slope method. Two other nonparametric, Mann–Kendall and Innovative Trend Analysis methods were also applied to validate fndings from Sen’s slope trend analysis. The mean fow discharge for each month (i.e. January to December), seasonal variation (i.e. Spring, Summer, Autumn, and Winter) as well as an annual mean, annual maximum and minimum fows were analysed for each station. The results show that three stations (i.e. Ashti, Tekra, and Polavaram) demonstrate an increasing trend, notably during Winter and Spring. In contrast, two other stations (i.e. Pathgudem, Chindnar) revealed a decreasing trend almost at all seasons. A signifcant decreasing trend was observed at all station over Summer and Autumn seasons. Notably, all stations showed a decreasing trend in maximum fows; remarkably, Tekra station revealed the highest decreasing magnitude. Signifcant decrease in minimum fows was observed in two stations only, Chindnar and Pathgudem. Findings resulted from this study might be useful for water managers and decision-makers to propose more sustainable water management recommendations and practices.

5

The water resources of tropical West Africa: problems, progress, and prospects

Ndehedehe Christopher E.

Acta Geophysica

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2019

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Vol. 67, no. 2

621--649

EN

West Africa plays key roles in global climate and shows one of the strongest variations in hydro-climatic conditions. As it turns out, the region appears to be underrepresented in the existing compendium of Earth science and hydrology-focused journal papers when it comes to significant discussion on terrestrial hydrology and freshwater science. This prominent gap is largely precipitated by increasing number of constraints that include lack of considerable and robust investments in gauge measurements for meteorological and hydrological applications, poor funding of research institutions and other disincentives, among other factors. In this manuscript, the challenges and problems in large-scale terrestrial hydrology-focused investigation in West Africa are reviewed. Using a dossier of some recent contributions in the field of remote sensing hydrology, this review also highlights some of the progress in terrestrial hydrology and the opportunities that exist for hydro-geodetic research in West Africa that leverage on sustained investments in satellite geodetic missions. It is noted that West Africa is still a pristine environment for hydrology-focused research and can benefit from recent advancements in sophisticated space agency programs such as the Gravity Recovery and Climate Experiment, which undoubtedly has revolutionized terrestrial hydrology research around the world for nearly two decades. Given the poor density of gauge stations and limited ground observations, hydrological research in West Africa is expected to benefit more from independent space observations and multi-resolution data. This is because the lack of sufficient in-situ data for the parameterizations and adequate initialization of outputs from hydrological models and reanalysis data for hydrological applications results in poor representation of the West African land surface and hydrological state variables. To further improve our contemporary understanding of West Africa’s terrestrial hydrology, the continued evaluation/validation of these observations and space-borne measurements is advocated.

6

Wpływ warunków klimatycznych na system fluwialny i melioracje wodne w pradolinach w rejonie Łowicza i Koźmina (Polska Środkowa)

Kobojek E.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2015

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Vol. 24, No. 4

381--390

PL

Artykuł przedstawia wpływ warunków klimatycznych na system fluwialny i meliorację w ostatnich 200 latach. Badania przeprowadzono w pradolinach w środkowej Polsce. Doliny te są bardzo ważnymi elementami nizinnego krajobrazu. Na przełomie wieków XVIII i XIX dna pradolin były zabagnione i kształtowane przez rzeki wielokorytowe. System rzeczny był związany z okresem większych opadów małej epoki lodowej. Takie warunki środowiskowe były bardzo uciążliwe dla gospodarki, dlatego podjęto decyzje o regulacji rzek i melioracji w pierwszej połowie XIX wieku. Prace melioracyjne przeprowadzono jeszcze w dwóch etapach w XX wieku (1928–1932 i 1961–1974). Prace wykonano w wilgotniejszych okresach i po dużych powodziach.

EN

This article presents the influence of climatic conditions on the fluvial system and reclamation in the last 200 years. The research has been conducted in proglacial valleys in Middle Poland. These valleys are extremely important element of the lowland landscape. Between the 18th and 19th century valley floors were paludified and formed by multichannel river system. That river system was connected with periods of higher rain-fall, related to the Little Ice Age. Such natural conditions were troublesome for the economy which is why it was undertaken to regulate the river and reclamation in the first half of the 19 th century. The reclamation was conducted in two stages of the 20th century (1928–1932 and 1961–1974). The operation was realized in wet periods and after major floods.

7

100 lat „Klimatologii ziem polskich” Romualda Mereckiego

Kossowska-Cezak U.

Przegląd Geofizyczny

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2015

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Z. 3-4

237--243

PL

W roku 1914, kiedy Polska nie istniała jako państwo, ukazała się w Warszawie obszerna (ponad 300 stron) monografia klimatu Polski. Jej autorem był Romuald Merecki (1860-1922) – astronom, meteorolog, fizyk i matematyk. W swojej książce, zatytułowanej Klimatologia ziem polskich (ziem polskich w granicach historycznych) pokreślił indywidualne cechy klimatu Polski i podzielił opisywany obszar na regiony („dziedziny”) klimatyczne. Autor skupił głównie uwagę na zmienności czasowej klimatu: wieloletniej, rocznej, dobowej i z dnia na dzień. Przedstawił związki okresowości elementów meteorologicznych (temperatury powietrza, opadów atmosferycznych i ciśnienia atmosferycznego) z aktywnością słoneczną. We wszystkich przedstawianych problemach poszukiwał przyczyn fizycznych. Ta książka, licząca już 100 lat, ma wciąż wartość naukową – również ze względu na bardzo obszerne tabele, stanowiące wartościowe źródło informacji.

EN

In 1914, when Poland did not exist as a state, the comprehensive (over 300 pages) monograph of Polish climate appeared. The author of this book was Romuald Merecki (1860-1922) – astronomer, meteorologist, physicist and mathematician. In this book, entitled Climatology of Polish territory (the territory within historical borders), the author pointed out the individual features of Polish climate and divided the country into climate regions. Author put the main attention on time variability of climate: many-year, annual, daily, from day to day. He demonstrated the relations of the periodicity of meteorological elements (air temperature, precipitations and atmospheric pressure) and solar activity. In every presented problems he made search after the physical causes. This 100-year old book is still of high scientific value, also due to its very abundant tables – a valuable source of information.

8

Intense precipitation and high river flows in Europe - observations and projections

Kundzewicz Z. W.

Acta Geophysica Polonica

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2005

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Vol. 53, nr 4

385--400

EN

Several destructive floods have occurred in the last decade in Europe, causing record high material damage. The question of detection and attribution of changes in various flood-related indices attracts increasing interest. Among the mechanisms that can impact flood risk are changes in socio-economic systems, which influence terrestrial systems, and changes in the climatic system. The atmosphere's water holding capacity (and hence potential for intense precipitation) increases with temperature and more intense precipitation has been documented in the warming world. However, a general and coherent increase in high river flows has not been detected. Results of change detection studies of daily river flow in Europe show that the overall maxima (for the 1961-2000 period) occurred more frequently in the subperiod 1981-2000 than in the subperiod 1961-1980. Regional changes in the timing of floods have been reported in many areas of Europe, with increasing incidence of late autumn and winter floods (caused by rain) and fewer spring snowmelt floods. Also, the number of ice-jam related inundations has decreased. On the other hand, intensive and long-lasting summer precipitation episodes have led to disastrous floods in Central Europe (cf. the 1997 Odra/Oder flood, the 2001 Vistula flood, and the most destructive 2002 deluge on the Labe/Elbe), and river flooding has been recently recognized as a major hazard in the region. Significant differences between future projections and the reference period, indicating the likelihood of increasing flood hazard, have been identified in both intense precipitation and high flows.