Long-term Precipitation Trends Research Articles

Elevation dependent precipitation changes in historical and future times in the Himalayan Upper Ganga Basin, India

This study examines long-term (1991–2092) precipitation trends in the Upper Ganga Basin (UGB) across multiple elevations, using historical data (1991–2022) and future Coupled Model Intercomparison Project Phase 6 (CMIP6) climate model datasets (2022–2092). By identifying the top five best-fit models from 29 climate model datasets, this study assesses historical patterns and project future changes in the Near-Future-Term (NFT) (2023–2056) and Far-Future-Term (FFT) (2061–2092) under moderate and extreme scenarios. Based on the evaluation of 29 CMIP6 climate models precipitation products, five models namely: BCC-CSM2-MR, CMCC-CM2-SR5, INM-CM5–0, KIOST-ESM, and NESM3 were selected as the best models describing precipitation over UGB and future precipitation of these models were bias corrected using linear scaling bias correction approach. Also it was observed that in the UGB region usually the climate models are much more reliable in capturing the precipitation pattern in lower and mid elevation regions as compared to higher-elevation regions. Further analysis of best five climate models' future precipitation indicates a substantial increase in wet spell occurrences in the south-western part of UGB, while the north-western and central regions are expected to see a rise in dry spell counts, although dry spell increase is insignificant. The mid-elevation range from 2200 to 4050 m which historically receives the most precipitation and is expected to continue experiencing the highest volume of precipitation in the future. The lower elevation range (287–1500 m) has anticipated the most substantial increase in future precipitation. Analysis suggests a future rise in low precipitation events (2.5 mm/day to 10 mm/day) at high elevations (4050 m to 7399 m) and an increase in events exceeding 10 mm/day in mid to low elevations (287 m to 4050 m). Although an increase in low precipitation events is expected across the entire UGB, it is particularly noteworthy that the region between 287 m to 4050 m is likely to experience a greater prevalence of these events. Historically, high elevations witnessed most of the years with over 20 days of annual snowfall. However, future scenarios indicate a prominent shift, predominantly anticipating <20 days per year of snowfall, signifying a significant change in snowfall patterns within the UGB. An analysis of snowfall patterns within the UGB indicates that historically, in the elevation range of 1500 m to 2200 m, some years have experienced 3–7 days of snowfall per year, however, under the SSP245 (NFT) scenario, this is projected to decrease to 2–5 days per year. Conversely, in scenarios SSP245 (FFT), SSP585 (NFT), and SSP585 (FFT), it is anticipated that there will be no snowfall in this elevation range in the future.

The Relationship between Changes in Hydro-Climate Factors and Maize Crop Production in the Equatorial African Region from 1980 to 2021

Agricultural production across the African continent is subjected to various effects of climate variability. One of the main staple foods in Sub-Saharan Africa is maize. However, limited scientific research has recently focused on understanding the possible effects of hydro-climatic variability on maize production. The aim of the present work was to contribute to policy and climate adaptation, thus reducing the vulnerability of maize production to climate change over Equatorial Africa. This study firstly examined long-term trends of precipitation (PRE), soil moisture (SM), actual evapotranspiration (E), and potential evapotranspiration (Ep), as well as surface air temperatures, including the minimum (TMIN) and maximum (TMAX). Secondly, the relationship between maize production and these climate variables was quantified for 18 Equatorial African countries (EQCs) over 1980−2021. To assess the linear trends, Mann–Kendall and Sen’s slope tests were used to quantify the magnitude of the hydro-climatic variable trends at the 5% significance level, and Pearson’s correlation coefficient was used to evaluate the relation of these climate parameters with the maize production. The annual mean PRE declined at 0.03 mm day−110a−1. Other climate variables increased at different rates: SM at 0.02 mmday−110a−1, E at 0.03 mm day−110a−1, Ep at 0.02 mm day−1 10a−1, TMIN and TMAX at 0.01 °C day−110a−1. A regional analysis revealed heterogeneous significant wet–dry and warm–cool trends over the EQCs. While, spatially, dry and warm climates were observed in the central to eastern areas, wet and warm conditions dominated the western regions. Generally, the correlations of maize production with the E, Ep, TMAX, and TMIN were strong (r &gt; 0.7) and positive, while moderate (r &gt; 0.45) correlations of maize production with PRE and SM were obvious. These country-wide analyses highlight the significance of climate change policies and offer a scientific basis for designing tailored adaptation strategies in rainfed agricultural regions.

Assessment of long-term historical trends in winter precipitation in Japan using large-ensemble climate simulations: Changes in the impact of southern coastal cyclones

Assessment of long-term historical trends in winter precipitation in Japan using large-ensemble climate simulations: Changes in the impact of southern coastal cyclones

Assessing long-term variability and trends in temperature and precipitation in Gilgit and Hunza river basins

Assessing long-term variability and trends in temperature and precipitation in Gilgit and Hunza river basins

Quantitative assessment of the variations in monthly precipitation trends induced by the impact of three gorges dam.

There are many studies that have examined the impact of the Three Gorges Dam (TGD) on changes in meteorological data, and most of them concluded that the TGD significantly reduced precipitation without taking into account the negative trends that had already existed before the impoundment. In this study, the investigation focused on the monthly precipitation data, and the Mann-Kendall (MK) trend analysis was conducted to show that the TGD had little effect on the trends of the precipitation data. Monthly data (1980-2018) from 19 stations upstream and downstream of the TGD and 5 stations located far from the main river were extracted. The analysis and results showed that although the linear long-term (1980-2018) precipitation trend upstream of the TGD was downward, the MK trend analysis showed that the precipitation trends became upward after impoundment. This situation existed even for station data located outside the region. Also, the analysis of monthly trends in different seasons showed that in spring and winter, there was only a very weak downward trend in monthly precipitation, while in summer and autumn, the trends were upward with steeper slopes. Following the upward trends of the monthly precipitation, the TGD generally positively intensified the monthly precipitation trends upstream and downstream of the dam, with the exception of a few months when total precipitation amounts were consistently low. In contrast to the trend analysis, which showed small and insignificant variations in precipitation data, the 12-month SPEI analysis showed a significant deterioration (about 20%) in the wetness index after impoundment both upstream and downstream of the TGD, while this situation did not occur outside the region. Thus, the TGD has extended dry periods both upstream and downstream of the dam over the past two decades.

Climate change impacts on river discharge to the Sea of Marmara

The Sea of Marmara, located in Northwestern Türkiye, is under multiple stressors, including climate change and industrial, agricultural, and domestic pollution, that cause deoxygenation in coastal waters, with multiregional consequences affecting the surface and deep-water masses transported to the Mediterranean and Black Seas, respectively, via its straits. With climate-change driven changes in the intensity of extreme precipitation events, the marine environment becomes more vulnerable to increasing terrestrial pollutants. Evaluating the spatial and temporal variation of river runoff is crucial to understanding the interaction between the geophysical and hydrogeochemical processes that affects the nutrient balance of the sea. This study aims to (i) explore the historical (for the period 1960-2021) and spatial changes of monthly-averaged coastal discharges along the coastline of the Sea of Marmara for the first time, based on observations from the national hydrological service; (ii) analyze the change in long-term and seasonal trends of runoff and net-precipitation rate and derive a regional relation between the two parameters. Single Spectrum Analysis (SSA) is used to obtain the trends. Gaps in the time series are filled in using a non-parametric spectral estimation method. Discharges from the northern, eastern, and southern basins are, respectively, 3%, 17%, and 80% of the total discharge, which has varied between 1.5 and 15 km3 per year in the last decade, with short-lived extremes occurring in early spring. Total runoff rate shows a declining long-term trend that is accelerating with increasing evaporation. The intensity of the terrestrial precipitation extremes shows a temporal increase; there is a quadratic relation between the long-term trends of net precipitation and total runoff. Quantification of nutrient load distribution along the coastline associated with the spatial-temporal changes in coastal fluxes is urgent because the cumulative stressors (warming, nutrient overenrichment, pollutants) pose a threat of triggering extreme events and eutrophication in the Sea of Marmara with multiregional impact.

A GIS-Based Assessment of Flood Hazard through Track Records over the 1886–2022 Period in Greece

This paper addresses the riverine flood events that have occurred in Greece over the last 136 years (i.e., during the 1886–2022 period), focusing, amongst others, on the case of urban floods. The flood record of various sites of the country has been collected and analyzed to determine their spatial and temporal distribution. Greece is a country where flood data and records are very scarce. Therefore, as there is not an integrated catalog of Greek floods spanning from the 19th century to recently, this is the first attempt to create an integrated catalog for Greece. The sources used include published papers, local and regional newspapers and public bodies (mainly the Ministry of Environment and Energy and the official websites of Greek municipalities). Additionally, the main factors responsible for their occurrence have been issued, regarding the country’s climatic, geological and geomorphological setting, as well as human interventions. In addition, the atmospheric circulation driving factors of floods are assessed via an unsupervised neural network approach (i.e., Self-Organizing Maps). Based on the results of this research, an online GIS-based database has been created, depicting the areas that have been struck by riverine floods in Greece. By clicking a flood event in the online database, one can view several characteristics, depending on data availability, such as duration and height of the rainfall that caused them and number of fatalities. Long-term trends of mean and extremes seasonal precipitation also linked to the spatial distribution of floods. Our analysis shows that urban floods are a very large portion of the overall flood record, and they mainly occur in the two large urban centers, Athens and Thessaloniki, as well as near large rivers such as Pineios. Autumn months and mainly November are the periods with higher flood hazards, based on past records and cyclonic atmospheric circulation constitutes the principal driving factor. Our results indicate that a flood catalog at national level is of fundamental importance, as it can provide valuable statistical insights regarding seasonality, spatial distribution of floods, etc., while it can also be used by stakeholders and researchers for flood management and flood risk analysis and modelling.

The Long-Term Performance of a Rainwater Harvesting System Based on a Quasi-Bicentennial Rainfall Time Series

The University of Genova (Italy) maintains a historical meteorological station that has provided daily rainfall measurements over a quasi-bicentennial period since 1833. The daily rainfall series is analyzed here to assess the impact of long-term precipitation trends on the performance of a rainwater harvesting system. The collected rainwater is used for the irrigation of urban green areas. A behavioral model is applied, involving a dedicated procedure to evaluate the actual soil water content available for vegetation and its decay over time. Non-dimensional indicators are obtained to support adaptation strategies and the sustainable design of the required storage tank. Since both irrigation demand and available water storage depend on the amount of rainfall received, fluctuations in daily rainfall and their trend do affect the performance of the system in a non-trivial way. The results demonstrate that the installation of an RWH system for landscape irrigation is a reliable and resilient solution, at least considering the measured rainfall variations of the last 200 years. In the town of Genoa, no specific adaptation seems necessary in terms of the design of the storage tank other than the usual oversizing, typical of engineering design, to account for uncertainties in the hydrological assessment of any RWH system.

Are the magnitude and frequency of floods increasing in Iran due to climate change? Implications from a 50-year analysis

ABSTRACT The correlation between extreme precipitation and flood magnitude is still poorly understood because of the complex mechanisms controlling flood generation. In this study, we used 50 years of precipitation and streamflow data across Iran to analyse the spatial distribution, slope, and significance of long-term trends in extreme precipitation compared to the spatial distribution of long-term trends for flood magnitude and frequency. Despite the decreasing trend of extreme precipitation in 60% of Iran’s sub-basins, the flood magnitude showed an increasing trend. In particular, the number of flooding days with a return period of 25~50 years and >50 years in 2010s has increased by 1.3 and 2.2 times, respectively, compared to that in 2000s. We attributed the above contrasting relationship between extreme precipitation and flood magnitude to the influence of an increase in short-duration extreme precipitations, extensive land use and land cover change, and reduced soil infiltration due to long-term droughts.

Assessing the impact of precipitation on hardrock aquifer system using standard precipitation index and groundwater resilience index: a case study of Purulia, West Bengal, India.

Groundwater stored in the aquifers provides water security during natural hazards, e.g. clean water access during floods and droughts. Groundwater drought, a phenomenon closely linked with rainfall (climate) variability, is less researched, especially in India. This study aims to detect precipitation and groundwater droughts and comprehend the groundwater response to long-term precipitation trends (25years). As a case study, the drought-affected and groundwater-depleted Purulia district in West Bengal, India, which is a part of the Chotanagpur plateau, was selected. Precipitation and groundwater droughts (in aquifer types of shallow, moderate and deep) are detected using the Standard Precipitation Index (SPI) and Groundwater Resilience Index (GRI). During the 25 yearstudy period (1996-2020),Purulia had 13 (52%) rainfall deficiency years, with an annualaverage rainfall of 1382 mm. SPI detected four severe droughts and the most severe occurring in 2010-2011 (1.50). GRI found that aquifermedium had a 71% [Formula: see text] conditions and are the most resilient and aquiferdeep experienced maximum extreme drought events and is the most stressed. The cross-correlationcoefficients (CCCs) between rainfall and groundwater is moderate in deep, shallow, and medium aquifers, with CCCs - 0.43, - 0.59, and - 0.49, respectively. Positive CCCs are found for seasonal lags of - 3, - 4, and - 7. The study found that during the monsoon, average depth to groundwater level is 1 - 4m and it drops to 8-10m during the lean period, more than 85% of wells are vulnerable to extreme droughts (SPI > 1.5), aquifer's response to rainfall is aquifershallow > aquifermoderate > aquiferdeep, and aquifer's may be arranged as aquifermoderate > aquifershallow > aquiferdeep depending on their drought resistance. This study, with the use of statistical tools and long term data, will aid in the management of groundwater at varying depthsby creating basis forunderstanding the groundwater response to rainfall events.

Расчет климатических характеристик осадков над Черным морем по данным региональных климатических моделей

The ability of 16 regional climate models (RCMs) from the CORDEX project to adequately simulate the average values and long-term trends in precipitation over the Black Sea is assessed. The results of the simulations performed using the RCMs are compared with the data of the ERA5 reanalysis for the control period (1959–2005). Average annual precipitation and average seasonal precipitation for winter and summer, as well as long-term trends in precipitation for all months in a wide range of quantiles, are analyzed. It was found that average seasonal precipitation over the Black Sea is satisfactorily simulated by most RCMs in winter and by six RCMs in summer. At the same time, the monthly precipitation trends estimated on the basis of forecast calculations are close to those based on the ERA5 data only for one RCM. Keywords: precipitation, quantile regression, Black Sea, CORDEX

Расчет климатических характеристик осадков над Черным морем по данным региональных климатических моделей

The ability of 16 regional climate models (RCMs) from the CORDEX project to adequately simulate the average values and long-term trends in precipitation over the Black Sea is assessed. The results of the simulations performed using the RCMs are compared with the data of the ERA5 reanalysis for the control period (1959–2005). Average annual precipitation and average seasonal precipitation for winter and summer, as well as long-term trends in precipitation for all months in a wide range of quantiles, are analyzed. It was found that average seasonal precipitation over the Black Sea is satisfactorily simulated by most RCMs in winter and by six RCMs in summer. At the same time, the monthly precipitation trends estimated on the basis of forecast calculations are close to those based on the ERA5 data only for one RCM. Keywords: precipitation, quantile regression, Black Sea, CORDEX

Long-term spatio-temporal analysis and trends of precipitation over semi-arid region of Rajasthan

Long-term spatio-temporal analysis and trends of precipitation over semi-arid region of Rajasthan

The Long-Term Trends of Global Land Precipitation in GFDL’s CM4 and ESM4 Climate Models

Abstract Historical precipitation and temperature trends and variations over global land regions are compared with simulations of two climate models focusing on grid points with substantial observational coverage from the early twentieth century. Potential mechanisms for the differences between modeled and observed trends are investigated using subsets of historical forcings, including ones using only anthropogenic greenhouse gases or aerosols, and simulations forced with the observed sea surface temperature and sea ice distribution. For century-scale (1915–2014) precipitation trends, underestimated increasing or unrealistic decreasing trends are found in the models over the extratropical Northern Hemisphere. The temporal evolution of key discrepancies between the observations and simulations indicates that 1) for averages over 15°–45°N, while there is not a significant trend in observations, both models simulate reduced precipitation from 1940 to 2014, and 2) for 45°–80°N observations suggest sizable precipitation increases while models do not show a significant increase, particularly during ∼1950–80. The timing of differences between models and observations suggests a key role for aerosols in these dry trend biases over the extratropical Northern Hemisphere. Additionally, 3) for 15°S–15°N the observed multidecadal decrease over tropical west Africa (1950–80) is only roughly captured by simulations forced with observed sea surface temperature; additionally, 4) in the all-forcing runs, the model with higher global climate sensitivity simulates increasing trends of temperature and precipitation over lands north of 45°N that are significantly stronger than the lower-sensitivity model and more consistent with the observed increases. Thus, underestimated greenhouse gas–induced warming—particularly in the lower sensitivity model—may be another important factor, besides aerosols, contributing to the modeled biases in precipitation trends.

Long-term trends of precipitation and erosivity over Northeast China during 1961–2020

Northeast China (NEC) is one of the vital commercial grain bases in China and it has suffered from soil erosion due to prolonged cultivation and lack of protection. To determine long-term trends of precipitation and rainfall erosivity over NEC during the latest decades, daily precipitation for the entire year during 1961–2020 and hourly precipitation for the warm season (May to September) during 1971–2020 were collected for 192 and 126 stations, respectively. Three seasons, including the cold season (October to April), early warm season (May to June), and late warm season (July to September) were divided according to the combination of precipitation and vegetation. Results demonstrate: (1) Daily precipitation reveals total precipitation and rainfall erosivity in the cold season and early warm season increase significantly at relative rates of 3.1% ∼ 6.1% compared with the average during 1961–2020, and those in the late warm season decrease insignificantly. (2) Hourly precipitation reveals storms occurring in the early and late warm seasons have undergone significant increasing changes, which shift towards longer storm duration, larger amount, peak intensity, kinetic energy, and rainfall erosivity during 1971–2020. Moreover, the frequency of extreme storms increased. (3) Rainfall erosivities estimated from daily precipitation during 1971–2020 increase insignificantly for the early and late warm season, whereas those from hourly precipitation increase significantly (6.1% and 5.5%, respectively), which indicates daily precipitation may not be able to capture the trend fully under the warming background, and precipitation at higher resolutions than the daily scale is necessary to detect trends of rainfall erosivity more accurately.

Substantial increase in abrupt shifts between drought and flood events in China based on observations and model simulations

Drought-flood abrupt alternation (DFAA) refers to the rapid transformation between droughts and floods, posing serious threats to ecological security, food production, and human safety. Previous studies have insufficiently investigated DFAA events at large regional scales using high-resolution observations and model simulations. In this study, the standardized precipitation evapotranspiration index was used to construct the DFAA magnitude index, which considers the asymmetric effects of drought and flood alternations. Four types of DFAA events were then investigated using high-resolution station observations and NEX-GDDP-CMIP6 model simulations. The results showed that hotspot areas of drought-flood and flood-drought alternation events were mainly in the northern and eastern parts of China, while the hotspot areas of drought-flood-drought and flood-drought-flood alternation events were obviously smaller than those of drought-flood and flood-drought alternation events. Drought-flood, flood-drought, and drought-flood-drought alternation events showed significant upward trends at rates of 0.075, 0.057, and 0.051 events/decade, respectively, and these increases were attributed to significant increases in moderate, severe, and extreme events across China during 1981–2020. Generally, the total number of DFAA events above moderate grade in the northern, central, and some areas in the southern parts of China increased obviously (>50 %) during 2001–2020 compared to 1981–2000. NEX-GDDP-CMIP6 can reasonably represent the multi-year averages and long-term trends of precipitation, temperature, and DFAA events in China. Except for the flood-drought-flood alternation events, the other three types of DFAA events showed significant increasing trends in the future, with higher rates under the SSP585 scenario than under the SSP245 scenario (e.g., drought-flood alternation events at rates of 0.033 and 0.046 events/decade under SSP245 and SSP585, respectively, during 1981–2100). DFAA events above the moderate grade were predicted to increase significantly in both 2032–2065 and 2066–2099 compared to 1981–2014, especially in northern China for the 2066–2099 under the SSP585 scenario.

Analyzing and Modeling the Spatial-Temporal Changes and the Impact of GLOTI Index on Precipitation in the Marmara Region of Türkiye

Precipitation is a particularly important part of the Earth’s hydrological cycle and, therefore, is a necessary variable for maintaining natural balance. This study investigated past, present, and future changes in precipitation in the Marmara region, and examined the effects of global warming on this variable. The study period was from 1960 to 2020, and the climate data of 15 synoptic stations in the Marmara region were used for this purpose. To achieve the objectives of the study, linear and 6th order polynomial regression, ombrothermic and hythergraph diagrams, geostatistical models, Mann-Kendall test, Pearson correlation, standard Z-scores, and multi-layer perceptron artificial neural network models (MLP-ANN) were used to model and predict precipitation. The results of the linear regression analysis showed that of the 15 stations, 6 stations had an increasing trend, 6 stations had a trendless pattern, and 3 stations had a decreasing trend. In terms of periodic analysis, the main downward trend started in 1964 and continued until 1992, while the main periodic upward trend started in 1992 and continued until 2016. The synoptic stations in the Marmara region showed a lack of precipitation over six to seven months of the year, and the precipitation changes in the region were stronger than the temperature changes. In addition, the highest precipitation was observed on the southeast coast of the Black Sea, and the lowest precipitation was observed in the eastern parts of the region. Moreover, except for the Bilecik and Kocaeli stations, the changes in the long-term trend of precipitation at the other stations were significant. Among the 15 stations, only the Kocaeli and Sarıyer stations showed a positive correlation with global temperature during the annual period. In addition, the developed ANN model was accurate in simulating and predicting precipitation and showed an upward trend over the next seven years.

Investigating Hydroclimatic Variables Trends on the Natural Lakes of Western Greece Using Earth Observation Data.

Expected global climate change is allegedly becoming more intense, and the impacts on water resources are being tracked in various hydroclimatic regimes. The present research investigates a hydrologically important area of Greece, where four natural lakes are concentrated. It aims to quantify any potential long-term trends in lake water area, precipitation, and temperature timeseries. Water area timeseries spanning four decades are estimated by the mNDWI from Landsat satellite imagery and used as an index of each lake's water storage. Precipitation and temperature measurements are obtained from the open access datasets Hydroscope and ERA5-Land, respectively. All of the timeseries were tested seasonally and annually with the Pettitt and Mann-Kendal tests for statistically significant breakpoints and trends detection. No timeseries analysis resulted in a statistically significant (at 0.05 or 0.1 levels) annual or seasonal trend. The hydroclimatic regime over the past forty years in western Greece is found to have been relatively stable. Land use was also assessed to have been relatively unchanging, converging to the overall stability of the local water regime. However, the findings of this research should not be interpreted as a reassurance against climate change, but as a call to further research for the detailed regional and local assessment of climate change and hydroclimatic variability with acknowledged statistical approaches.

Observed changes in temperature and precipitation over Asia, 1901-2020

Asia is the largest continent in the world and home to 4.7 billion people. Climate change on this continent, therefore, attracts a significant amount of attention from scientists and policy-makers. However, observational studies of long-term climate change over the continent as a whole are lacking. Using updated, homogenized observational data from stations in Asia since 1901 and systematic-bias-adjusted data from stations in China after 1950, we analyzed the long-term trends of surface air temperature (SAT) and precipitation in Asia and China from 1901-2020. The results showed that (1) in the 120 yr between 1901 and 2020, the annual mean SAT rose significantly at rates of 0.13 ± 0.01 and 0.14 ± 0.03°C decade-1 in Asia and China, respectively. The year 2020 in Asia may have been the warmest year since the beginning of the 20th century. (2) Since 1901, in both Asia and China, the annual mean minimum temperature increased more than twice as fast as the maximum temperature, and the diurnal temperature range (DTR) dropped significantly. (3) From 1901-2019, the annual precipitation anomaly percentage in Asia showed a significant increasing trend at an average rate of 0.52 ± 0.10% decade-1, and the increase was more obvious in high latitudes than in low to mid-latitudes. (4) Since 1901, there has been no significant change in annual precipitation in China, but there was a weak and non-significant decrease in the first half of the 20th century and a significant increase after the mid 20th century. The results presented in this paper can help us understand the spatio-temporal patterns and causes of climate change in the Asian continent and Chinese mainland.

Spatial distribution of oceanic moisture contributions to precipitation over the Tibetan Plateau

Abstract. Evaporation from global oceans is an important moisture source for glaciers and headwaters of major Asian rivers in the Tibetan Plateau (TP). Although the accelerated global hydrological cycle, the altered sea–land thermal contrast and the amplified warming rate over the TP during the past several decades are known to have profound effects on the regional water balance, the spatial distribution of oceanic moisture contributions to the vast TP remains unclear. This hinders the accurate quantification of regional water budgets and the reasonable interpretation of water isotope records from observations and paleo archives. Based on historical data and moisture tracking, this study systematically quantifies the absolute and relative contributions of oceanic moisture to long-term precipitation in the TP. Results show that the seasonal absolute and relative oceanic contributions are generally out of phase, revealing the previously underestimated oceanic moisture contributions brought by the westerlies in winter and the overestimated moisture contributions from the Indian Ocean in summer. Quantitatively, the relative contribution of moisture from the Indian Ocean is only ∼30 % in the south TP and further decreases to below 10 % in the northernmost TP. The absolute oceanic contribution exhibits a spatial pattern consistent with the dipole pattern of long-term precipitation trends across the Brahmaputra Canyon region and the central-northern TP. In comparison, relative oceanic contributions show strong seasonal patterns associated with the seasonality of precipitation isotopes across the TP.