Summer Rainfall Research Articles

Trend Analysis of Rainfall and Temperature in the Kharun Watershed: Implications for Climate and Water Management

Rainfall and temperature are critical meteorological variables for understanding climate change and its potential impacts on water resources. Rainfall and Temperature are the most important for climatic parameters. The result of this study will help to take necessary steps and measures for agricultural production. This study focuses on analyzing rainfall and temperature trends in the Kharun watershed, Chhattisgarh, using the Mann-Kendall (MK) test and Sen's slope (SS) estimator. The analysis covers seasonal (summer, winter, and monsoon) and annual trends across key stations. Results for precipitation trends reveal mixed outcomes. At Dhamtari, a significant increasing trend in summer rainfall (z = 3.21, p < 0.01, Sen's slope = 0.77) was observed, though the annual trend remains insignificant. In Patharidih, summer rainfall also shows a significant upward trend (z = 2.04, p = 0.04), while Raipur exhibits a significant decline in both annual and summer precipitation (z = -1.04, p = 0.03, Sen's slope = -0.27). Temperature trends indicate no significant changes in maximum temperature across most stations, though slight positive trends are observed in summer and monsoon seasons. However, minimum temperature trends show a significant decline during winter at Dhamtari and Raipur (z = -2.12, Sen's slope = -0.04). These findings highlight localized seasonal variability in rainfall and temperature, underlining potential challenges for water resource management and climate adaptation in the region.

Seasonal Variations in the Thermal Stratification Responses and Water Quality of the Paldang Lake

We evaluated the thermal and chemical stratifications of Paldang Lake using Schmidt’s stability index (SSI) and the chemical stratification index (IC-i) with weekly data from 2013 to 2022. The temporal trends of stratification were analyzed alongside correlations with meteorological, hydrological, and water quality variables. Thermal stratification intensified with rising air temperature and sunshine duration, while hydrological factors like discharge and retention time affected SSI during periods with less than five days of water retention. During summer, fewer occurrences of intense rainfall or early rainfall before August led to stronger stratification. In fall, nutrient influx from external sources during summer stimulated algal growth, increasing Chlorophyll-α (Chl-α) concentrations. Summer rainfall had a significant impact on the strength and duration of stratification in Paldang Lake. Annual rainfall patterns and subsequent changes in discharge were key factors affecting the physical environment of the lake, which in turn determined water quality and the extent of algal blooms. We provide insights into the seasonal stratification and water quality variations in temperate river-type reservoirs like Paldang Lake. SSI and IC-i from this research can be applied to understand stratification and mixing dynamics in other lakes.

Nitrogen requirements of canola (Brassica napus L.) at sustained deficit irrigation levels in central Free State, South Africa

In South Africa canola (Brassica napus L.) is cultivated in rotation with wheat under winter rainfall in the Western Cape province. Expansion of the crop to the other eight provinces is propagated to reduce a shortage of locally produced plant oils. At the same time, canola may serve as a rotational crop for wheat in these summer rainfall provinces. In central Free State, agronomic information for canola production is lacking. An experiment with a line source sprinkler irrigation system was therefore conducted to establish the influence of water application levels (175, 233, 295, 351 and 420 mm) in combination with nitrogen (N) application rates (0, 70, 140, 210 and 280 kg ha−1) on the branches, pods and seeds per canola plant. The biomass and seed yields of canola were also measured, allowing calculation of harvest indices. All six variables were strongly influenced by the interaction of water and N applications. An optimal seed yield of 2.907 kg ha−1 was estimated with a 351 mm water application and a 280 kg ha−1 N application. This resulted in a water use efficiency of 8.28 kg seed ha−1 mm−1 water and a nitrogen use efficiency of 10.38 kg seed kg−1 N.

Ecohydrological Dynamics and Temporal Water Origin in a European Mediterranean Vineyard

ABSTRACTViticulture is an essential sector in agriculture as wine production plays a vital role in the socio‐economic life of many countries, especially in the Mediterranean area. Grapevines are a valuable, long‐lived species able to grow in hot and dry regions. We currently do not know whether rain‐fed grapevines entirely rely on deep soil water or make substantial use of shallow water from summer precipitation events. Without knowing this, we poorly understand what fraction of summer precipitation inputs contributes to grapevine transpiration. This has implications for how we quantify grapevine‐relevant precipitation budgets and for predicting the impacts of climate change on grape and wine production. We investigated grapevine water use in a vineyard in the Chianti region, central Italy. During the growing season of 2021, we monitored precipitation and soil moisture at 30‐ and 60‐cm depth. We collected over 250 samples for stable isotope analysis from rainfall, soil, and plants. Since traditional plant water sampling is problematic for grapevines, we collected samples from shoots, leaves, and condensed leaf transpiration after sealed plastic bags were wrapped around a shoot. We use these alternative plant samples to reconstruct the isotopic signal in the xylem water and infer the plant's seasonal water origin throughout the growing season. The analysis of the seasonal origin of water revealed that, throughout the growing season, soil water and plant water received disproportional contributions by rain that had fallen in the winter, even when compensating for the Mediterranean climate of the area. Only in late summer did the grapevines use substantial amounts of summer rainfall, whose contribution occasionally became dominant. These results provide a better understanding of ecohydrological interactions and uptake dynamics in valuable socio‐economic agroecosystems such as vineyards.

Temporal variability of spatial patterns of correlations between summer rainfall and the Oceanic Niño Index in the Pampean region

The Argentinean Pampean region is essential for global food security, known for its extensive production of soybeans, corn, and wheat. The November to January (NDJ) trimester is critical for rainfed summer crops, as precipitation during this period directly affects soil moisture and crop yields. The El Niño-Southern Oscillation (ENSO), particularly its Oceanic Niño Index (ONI), plays a crucial role in influencing precipitation patterns in this region. This study investigates the spatial correlation between the ONI and NDJ precipitation from 1990 to 2021 sing a 20-year sliding window approach. We conducted Pearson correlation and cluster analyses to identify regions with consistent ONI-precipitation relationships. Our findings reveal notable temporal variability, with a general decrease in correlation strength since the window 1995–2014. This decline is likely driven by changes in ENSO dynamics and the influence of other climate variability modes, highlighting the need to consider factors modulating the ONI-precipitation relationship. Notably, the addition of the strong 2015 El Niño, which exhibited inconsistent precipitation behaviour compared to previous strong El Niño events such as 1997, contributed to this weakening. While the 1997 El Niño brought widespread positive rainfall anomalies, the 2015 event was marked by weaker and even negative precipitation anomalies in part of the region. This difference mirrors similar patterns reported in other parts of South America, such as Ecuador and Coastal Peru, and may be linked to a poleward shift in the jet streams during the 2015/2016 El Niño. The results underscore the complexity of ENSO's impact on regional climate and highlight the need for adaptive agricultural planning. By enhancing the understanding of ONI-precipitation dynamics, this study aims to improve long-term climate predictions and support sustainable agricultural practices in the Pampean region.

Supporting the development of climate-resilient water safety plans through a risk-screening framework for drinking water source protection

ABSTRACT Climate change-induced impacts on water-quality challenge risk management of drinking water. Uncertainty around future changes and limited resources require approaches that enable prioritisation at regional or national scale for planning and adaptive intervention. This paper presents a framework for risk screening drinking water supplies, providing a staged approach to building the capacity for integrating climate change into risk management. The framework is applied to drinking water sources of the Scottish national drinking water provider, developing raw water trajectories for indicative water-quality parameters (water colour and Escherichia coli). It establishes baseline understanding of water-quality controls through multivariate statistical analysis. It incorporates climate and land-use change into the model using climate (UKCP18) and land-use projections. The results suggest potential higher organic carbon production in soils from increased production with higher temperature, combined with reduced dilution and drought effects from reductions in summer rainfall. For E. coli, risks arise through land-use change leading to potential agricultural intensification. The framework supports the targeted development of climate-resilient Water Safety Plans, prioritising systems most at risk of raw water-quality deteriorations. It emphasises source protection to maintain or improve regulatory compliance, minimise socioeconomic and environmental harms, and generate additional benefits.

Linking basin-scale hydrology with climatic parameters in western Himalaya: Application of satellite data, temperature index modelling and in-situ observations

Due to limited spatial and temporal in-situ runoff data availability, Himalaya-Karakoram (HK) glaciohydrology has a significant knowledge gap between large-scale and small-scale runoff modelling studies. This study reconstructs longest basin-wide runoff series in Chandra-Bhaga Basin by applying a high-resolution glaciohydrological model SPHY (Spatial Processes in Hydrology) over 1950–2022. Two-tier model calibration is done using in-situ basin-wide runoff (1973–2006) and MODIS snow cover (2003–2018). Model validation is done against in-situ Chhota Shigri Glacier catchment-wide runoff (2010–2015). The modelled mean annual basin-wide runoff is 60.21 ± 6.17 m3/s over 1950–2022, with maximum runoff in summer-monsoon months, peaking in July (182.69 m3/s). Glacier runoff (ice melt + snowmelt over glacier) contributes maximum (39%) followed by equal contributions from snowmelt runoff from non-glacierized basin area and baseflow (25%), while rainfall-runoff contributes minimum (11 %) to total runoff. There is a significant volumetric increase by ∼7% from pre- (59.17 m3/s) to post-2000 (63.47 m3/s) mainly because of early onset of snowmelt post-2000 that resulted in a hydrograph shift by ∼25 days earlier in spring. The glacier runoff is overestimated by 3% from RGI 7.0 inventory compared to different manually delineated inventories over 1950–2022, because of higher glacierized area from RGI 7.0. The precipitation shows a negative trend, but total runoff shows a positive trend due to positive trend of temperature that resulted in more glacier runoff and rainfall-runoff for basin over last 72 years. Basin-wide runoff is mainly governed by summer temperature which directly controls the amount of glacier and snowmelt runoffs and is supported by summer rainfall. This study highlights importance of basin-scale model calibration with in-situ data in large scale studies and stresses the need for in-situ observations in high-altitude Himalayan region. Basin-scale calibrated model parameters are transferable to glacier catchment scale within Chandra-Bhaga Basin, showing the model robustness at a small catchment scale.

Impact of parametric seasonal variations on water quality in the Crocodile River and Inyaka Dam in the Mpumalanga Province, South Africa

This study assessed seasonal variations in water quality and their impact on the Inyaka Dam and Crocodile River in Mpumalanga Province, South Africa. A total of 206 water samples were collected across four seasons to analyse parameters including pH, turbidity, electrical conductivity (EC), temperature, Manganese (Mn), Iron (Fe), phosphate (PO43−), nitrate-nitrogen (NO3-N), E. coli, total coliforms, faecal streptococci, and Bifidobacteria. Principal component analysis (PCA) and Pearson correlation identified major pollutants and their seasonal variations, while cluster analysis grouped water quality by parameter fluctuations.Findings indicated that water quality in both the Inyaka Dam and the Crocodile River exceeded permissible limits. In the Inyaka Dam, summer rainfall (202.68 mm) spurred microbial growth, including E. coli and Bifidobacteria, while winter saw elevated levels of PO43−, EC, Fe, and NO3-N. The Crocodile River exhibited its poorest water quality in summer, with high levels of conductivity, turbidity, Fe, Mn, and NO3-N, driven largely by rainfall. Winter pollution in the river was marked by E. coli, PO43−, total coliforms, NO3-N, and Bifidobacteria.The study highlights significant pollution in the Crocodile River, particularly in summer, linked to rainfall and effluent discharges. Microbial pollution persisted across seasons, influenced by both weather and point-source contamination. The winter season exacerbated water quality deterioration in the Crocodile River due to reduced flow, while Inyaka Dam's winter pollution was attributed to lake stratification.

Sedimentological and geochemical proxies reveal changes in the South Atlantic Convergence Zone in Southeast South America during the Late-Holocene

Today, the South Atlantic Convergence Zone (SACZ), a convective band that extends across central Brazil to the western South Atlantic Ocean, modulates Southern Hemisphere summer rainfall in Southeastern Brazil. During the Holocene, however, the role of the SACZ over the rainfall regime in this part of South America is still under debate. This study aims to provide new insights into the SACZ Late-Holocene variability through analysis of the geochemical (XRF-based bulk sediment Metal/Metal ratios) and sedimentological (grain size and end-member modeling) variations along four cores retrieved in a coastal area (24–49 m water depth) located in the core of modern SACZ. Our records show an increase in Ti/Ca ratios, suggesting increased rainfall and that the terrigenous input to the Brazilian southeastern inner shelf changed in the Late-Holocene (last 4200 years). These changes are also followed by a decrease in the K/Ti ratio, indicative of an increase in chemical weathering in the sediment source, and an increase in the Mn/Ti, suggesting an increase in oxidation. Additionally, decadal-scale variability with periodicities of 25 and 55 years obtained by a time-series (Redfit) analysis highlights a potential role of the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation, respectively, as drivers of the SACZ variability over the last 4200 years.

Interannual variation of summer southwest monsoon rainfall over the monsoon core regions of the eastern Bay of Bengal and its relationship with oceans

The study looked at how summer monsoon rainfall in the eastern Bay of Bengal area changes from year to year due to Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO). Study used rainfall data and sea surface temperature data to see these variations. It's found that during ENSO positive phase, rainfall decreased in the eastern coastal region of the Bay of Bengal but increased in the northern Indo-Myanmar region. The opposite happened during ENSO negative phase. The study used a special analysis method called EOF and Morlet wavelet power-spectrum analysis to look for important patterns in the rainfall data and did correlation analysis to understand what causes abnormal rainfall in these regions. The study also found that the local convection and water vapor flux during ENSO positive phase are related to the anomalous rainfall in the Monsoon Core region. Rainfall is made stronger by the unusual anticyclone circulation in the upper troposphere. A strong/weak Mainland Indochina southwest monsoon (MSwM) in the positive or negative phase of ENSO can bring excess/less moisture to wet/dry the local southwest summer rainfall. In northern Indo-Myanmar, the anomalous rainfall is not only relied on the intensity of the MSwM but also the frequency of western disturbances also influences the regional rainfall, and further study need to develop.

Future Scenarios of Design Rainfall Due to Upcoming Climate Changes in NSW, Australia

The occurrence of rainfall is significantly affected by climate change around the world. While in some places this is likely to result in increases in rainfall, both winter and summer rainfall in most parts of New South Wales (NSW), Australia are projected to decrease considerably due to climate change. This has the potential to impact on a range of hydraulic and hydrologic design considerations for water engineers, such as the design and construction of stormwater management systems. These systems are currently planned based on past extreme rain event data, and changes in extreme rainfall amounts due to climate change could lead to systems being seriously undersized (if extreme precipitation events become more common and/or higher in magnitude) or oversized (if extreme rainfall events become less frequent or decrease in magnitude). Both outcomes would have potentially serious consequences. Consequently, safe, efficient, and cost-effective urban drainage system design requires the consideration of impacts arising from climate change on the approximation of design rainfall. This study examines the impacts of climate change on the probability of occurrence of daily extreme rainfall in New South Wales (NSW), Australia. The analysis was performed for 29 selected meteorological stations located across NSW. Future design rainfall in this research was determined from the projected rainfall for different time periods (2020 to 2039, 2040 to 2059, 2060 to 2079, and 2080 to 2099). The results of this study show that design rainfall for the standard return periods was, in most cases, lower than that derived employing the design rainfall obtained from the Australian Bureau of Meteorology (BoM). While most of the analysed meteorological stations showed significantly different outcomes using the climate change scenario data, this varied considerably between stations and different time periods. This suggests that more work needs to be performed at the local scale to incorporate climate change predicted rainfall data into future stormwater system designs to ensure the best outcomes.

Rainfall Impacts Dissolved Organic Matter and Cation Export From Permafrost Catchments and a Glacial River During Late Summer in Northeast Greenland

ABSTRACTOngoing and amplified climate change in the Arctic is leading to glacier retreat and to the exposure of an ever‐larger portion of non‐glaciated permafrost‐dominated landscapes. Warming will also cause more precipitation to fall as rain, further enhancing the thaw of previously frozen ground. Yet, the impact of those perturbations on the geochemistry of Arctic rivers remains a subject of debate. Here, we determined the geochemical composition of waters from various contrasting non‐glacial permafrost catchments and investigated their impact on a glacially dominated river, the Zackenberg River (Northeast Greenland), during late summer (August 2019). We also studied the effect of rainfall on the geochemistry of the Zackenberg River, its non‐glacial tributaries, and a nearby independent non‐glacial headwater stream Grænse. We analyzed water properties, quantified and characterized dissolved organic matter (DOM) using absorbance and fluorescence spectroscopy and radiocarbon isotopes, and set this alongside analyses of the major cations (Ca, Mg, Na, and K), dissolved silicon (Si), and germanium/silicon ratios (Ge/Si). The glacier‐fed Zackenberg River contained low concentrations of major cations, dissolved Si and dissolved organic carbon (DOC), and a Ge/Si ratio typical of bulk rock. Glacial DOM was enriched in protein‐like fluorescent DOM and displayed relatively depleted radiocarbon values (i.e., old DOM). Non‐glacial streams (i.e., tributaries and Grænse) had higher concentrations of major cations and DOC and DOM enriched in aromatic compounds. They showed a wide range of values for radiocarbon, Si and Ge/Si ratios associated with variable contributions of surface runoff relative to deep active layer leaching. Before the rain event, Zackenberg tributaries did not contribute notably to the solute export of the Zackenberg River, and supra‐permafrost ground waters governed the supply of solutes in Zackenberg tributaries and Grænse stream. After the rain event, surface runoff modified the composition of Grænse stream, and non‐glacial tributaries strongly increased their contribution to the Zackenberg River solute export. Our results show that summer rainfall events provide an additional source of DOM and Si‐rich waters from permafrost‐underlain catchments to the discharge of glacially dominated rivers. This suggests that the magnitude and composition of solute exports from Arctic rivers are modulated by permafrost thaw and summer rain events. This event‐driven solute supply will likely impact the carbon cycle in rivers, estuaries, and oceans and should be included into future predictions of carbon balance in these vulnerable Arctic systems.

The Impact of Changing Climate on an Endangered Epiphytic Orchid (Pleione formosana) in a Montane Cloud Forest and the Conservation Challenge Ahead.

Pleione formosana Hayata is an endemic orchid that was once widely distributed across the mid-elevations of Taiwan. However, populations of this orchid have steadily shrunk due to orchid poaching in most of its habitats. By correlating data from micrometeorological stations that we installed in the cloud forest canopy at the study site, Yuanyang Lake (YYL) from 2017, we discovered the critical role of spring rainfall in triggering flowering and summer rainfall in promoting the growth of new bulbs. We found that rising temperatures and frequent drought events threaten orchid growth, potentially leading to pathogen infections. We climbed old-growth yellow cypresses to collect seed capsules of P. formosana for in vitro germination at YYL beginning in the autumn of 2018. Orchid plantlets were reintroduced to the study site in mid-August of 2022. However, the seedlings failed to survive the summer of 2023. This study is the first persistent monitoring of this rare orchid in the forest canopy of this old-growth cloud forest. Based on the result, we propose conservation strategies and directions for protecting this orchid on a regional scale. Our study highlights the mounting challenge to conservation efforts posed by global climate change.

Reconstruction of Summer Rainfall over the Last Five Centuries Based on Oak Chronology (Western Pomerania, Poland)

The quantity and distribution of summer rainfall in Poland is one of the main elements of weather and makes a strong impact on the economy, mostly agriculture, stockbreeding, and forestry and the associated industries. Droughts or heavy rains, occurring increasingly more frequently in summer, are a threat for human activity. This study presents a nearly 500-year-long reconstruction of precipitation in the June–July period for northwestern Poland based on an analysis of tree-ring widths in the native oak species (Quercus spp.) from 24 study plots located in Western Pomerania. Due to the frequent droughts occurring in the last four decades, and due to strong air pollution in the 1960s–1990s, we chose the period 1901–1941 as the calibration period. The performed reconstruction is characterized by a high annual variability in precipitation sums for June and July of the year of the tree-ring formation from 1565 to 2020, with an average rainfall sum for this period equal to 131.7 mm (standard deviation: 28.4 mm). Periods with rainfall shortages in summer occurred in the following years: 1579–1596, 1629–1637, 1650–1655, 1669–1672, 1703–1706, 1739–1748, 1757–1760, 1765–1768, 1808–1811, 1838–1841, 1856–1859, 1958–1961, 1965–1968, 1981–1983, and 2002–2006. Periods with higher than average rainfall in June and July occurred in the following years: 1573–1578, 1605–1609, 1613–1617, 1638–1642, 1694–1698, 1776–1780, 1791–1794, 1828–1831, 1852–1855, 1863–1866, 1877–1879, and 1944–1946. Our reconstruction was verified based on the historical records, available from the XVI century onward. Not all the reconstructed summer precipitation values, however, were confirmed by historical records. Notably, however, the historical data are often incomplete and imprecise. Further, the tree-ring width in the oak depends not only on the precipitation in June and July but also, e.g., on the pluvial conditions late in the previous growth season.

Assessing spatiotemporal heterogeneity of coastal organic nonpoint source pollution via soil erosion in Yellow River Delta, China

China has been facing severe organic pollution and the nonpoint source export from surface soil is usually overlooked in coastal areas. In this paper, from the perspective of catchment and attenuation, we have constructed a risk assessment method for coastal nonpoint source pollution (NSP) by applying the revised universal soil loss equation (RUSLE) and geostatistical analysis. Combined with the soil and water monitoring data, we have simulated regional NSP risks originating from surface soil organic matter (SOM) in the Yellow River Delta (YRD). Field surveys have verified the significant positive correlations between watershed SOM exporting risks and estuarine chemical oxygen demand (COD) fluxes during the rainy season. There present obvious logarithmic relations between the COD fluxes and the rainfall quantities, and the surface organic NSP risks. Larger NSP contributing sources are mainly located in the areas with higher soil exposure and stronger land-sea interactions. It should focus on the agricultural areas and improve relevant fertilizing and tillage methods to reduce source-exporting risks. Additionally, the summer rainfall concentrating periods need to be controlled emphatically, and vegetation-improving strategies need to be supplemented with the spatiotemporal-specific managements. This study provides a new insight for getting early terrestrial warning information for offshore organic water pollution, and presents research references for similar regional NSP issues.

Determining the onset of summer rainfall over Vietnam using self-organizing maps

Determining the onset of summer rainfall over Vietnam using self-organizing maps

Impact of Enso on Indian Monsoon and Food Production

El Nino is a big ocean-atmosphere climate interaction It happens when Sea Temperatures (SST) warm up in central and eastern parts of the Equatorial Pacific. Whereas La Nina is the opposite event of it, when ocean SST cools down in those same areas. Together, El Nino and La Nina are known as the El Nino Southern Oscillation Index (O). Usually, El Nino brings warm and dry weather to southern & eastern inland regions of India, Australia, Indonesia, Philippines, Malaysia, and the central Pacific islands. The variations of Indian summer monsoon Rainfall (ISMR) are linked to changes in sea surface temperatures over the equatorial Pacific & Indian Oceans. ENSO events really affect summer rainfall in India and major droughts have faced during El Nino events. When El Nino kicks in, it often leads to weak monsoons & higher temperatures in India. This raises the chances of droughts, which could upset crop production & water supply in India. The lack of rain because of El Nino causes crop production to drop, especially short-duration Kharif crops. This situation can lead to higher inflation rates & slower GDP growth, since agriculture is such a huge part of India’s economy. Therefore, this paper provide information about how El Nino affects climate throughout various regions of India, especially regarding monsoons and growing food.

Role of ocean-atmosphere interaction in intraseasonal variability of summer rainfall over the Indo–Northwest Pacific

Role of ocean-atmosphere interaction in intraseasonal variability of summer rainfall over the Indo–Northwest Pacific

Environmental Filters Structure Cushion Bogs' Floristic Composition along the Southern South American Latitudinal Gradient.

The environmental filtering hypothesis predicts that abiotic factors restrict communities by selecting species capable of survival and persistence under specific conditions, resulting in variations in beta diversity, phylogenetic clustering, and niche differentiation among communities when studying environmental gradients. Cushion bogs and high-altitude wetlands along the Andes display homogeneous flora contrasting with zonal vegetation. Despite being influenced by microclimatic conditions, these ecosystems are subject to diverse environmental effects. Here, we test the environmental filtering hypothesis on the structure of cushion bog communities along a broad-scale latitudinal gradient from 15° S to 42° S. We analyzed 421 bogs and 293 species across three macroclimatic regions with distinct summer, winter, and transitional arid rainfall regimes. Using variance partitioning and membership-based regionalization models, we examined the impacts of climatic, edaphic, and spatial variables on beta diversity. We also assessed species' niche overlap and the influence of environmental filters on the communities' phylogenetic diversity. Results show that species turnover and niche overlap vary with macroclimatic differences, delineating three distinct regions. Notably, phylogenetic clustering in the driest part of the gradient (23° S-24° S) highlights the impact of environmental filtering. Aridity and temperature variations at a broad scale serve as environmental filters shaping the composition of bog communities across southern South America.

Impact of the thermal contrast between the Arabian Sea and the Iranian Plateau on the interannual variability of the East Asian summer monsoon

Abstract The land–sea thermal contrast is known to have a significant impact on the atmospheric circulation. We investigated the influence of the thermal contrast between the Arabian Sea (AS) and the Iranian Plateau (IP) on the interannual variability of the East Asian summer monsoon (EASM). It is found that the thermal distribution of AS–IP exhibits a fixed dipole mode. When the apparent heat over AS (IP) is higher (lower) than normal, summer rainfall is abundant over the mid- and lower reaches of the Yangtze River and Japan with the adjacent maritime regions. By contrast, there is lower rainfall in North China and the coastal regions of South China. We attribute this phenomenon to the propagation of mid-latitude Rossby waves, which play a crucial role in regulating the atmospheric circulations on East Asia and the Northwest Pacific. Significant anomalies in the transport of water vapor were seen in our statistical analyses and were partly reproduced by the Linear Baroclinic Model and Weather Research and Forecasting model experiments. The anticipated outcomes of this research will help to identify another factor related to the variability of the EASM, and provide a scientific basis for understanding the distribution and interaction of thermal anomalies on the plateau system and the Indian Ocean.