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Heatwaves are characterized by an increase in temperature to extreme levels, which adversely distress the living organisms. India ranks second in terms of disaster mortality among the world countries, preponderantly by heatwave—influenced by regional climatology. In this study, the Excess Heat Factor (EHF) index is used to detect the heatwave using the ERA-Interim reanalysis dataset over various states of India during the summer period (April–June of 2017–2019). EHF categorizes heatwaves based on the severity, which is an intensity measure created by combining the measures of excess heat, long-term temperatures anomaly characteristics by each location’s unique climatology of heat by various thresholds. The heatwave events are analysed by combining the means of excess heat and heat stress, which has a strong aspect of EHF measurements. Concerning the intensity of future heatwaves, EHF index helps to analyse the frequency and intensity of heatwave episodes and alert those community most exposed to heat related illness. One of the indices is derived from a climatological background to analyse the severity of heatwave over the Indian states. The analysis over India using the EHF index reflected a substantial rate of increase in the intensity and the frequency of heatwaves in the successive years with an average EHF intensity (mean EHF for the analysis period) of ~ 41 °C2, ~ 38 °C2 and ~ 39 °C2, especially over the north–western states, eastern coastal states and central and southern states, respectively. The results of this study serve as a drive in the risk and vulnerability planning and assessment.

The first part of the study refers to the occurrence of the Indian summer events in Romania, over the 1961-2019 period. The second part analyses the Indian summer event recorded in Romania in October 2019. The datasets used for the first part were daily maximum and minimum temperatures recorded in the past 59 years at 23 climatological weather stations, divided into 6 regions. Regarding the methodology, first step was to determine the annual and seasonal occurrence of the first frost for each weather station, and then the presence of the warm spells (WSs), based on the percentile threshold method. So, we could determine WSs with different types of intensity (using the 90th, 95th, 98th percentile), and durations. For the Indian summer event recorded between 12 and 28 October 2019, daily maximum temperatures from 157 weather stations were compared to absolute maximum temperatures over the period 1961-2018. Synoptic conditions were determined using weather charts at sea level pressure, geopotential height and temperature of 925, 850, 700 and 500 hPa. The main finding is: Indian summer events are frequent in the Carpathians and in the Northern, Central and the Western regions of Romania, especially in November, followed by October; no matter the intensity, short duration events have high number of cases, and severe and extremely severe events were registered in the past 20 years; the Indian summer event from October 2019 was influenced by synoptic and local conditions, as well. Overall the Indian summer is not present in Romania every year, but it is more frequent and intense in the last 20 years.

This observational study mainly examines the impacts of short- and long-time fluctuations of surface wind fields over the Arabian Sea (AS), the Bay of Bengal (BoB), and the southern Indian Ocean (SIO) on Indian Summer Monsoon Rainfall (ISMR), with special reference to strong and weak Indian summer monsoons (ISM). Two datasets over 1991–2014 are used: (1) the daily gridded rainfall produced by India Meteorological Department (IMD), and (2) the Cross-Calibrated Multi-Platform (CCMP) wind product version 2.0 created by Remote Sensing Systems. Monthly mean surface wind speed, convergence, and curl in the AS, BoB, and SIO are overall not significantly different between strong and weak ISMRs except for wind speed in the AS in September. However, the probability density function (PDF) distribution of daily values over the AS, BoB, and SIO during strong ISMRs is different from during weak ISMs, suggesting that sub-monthly surface wind characteristics could be useful in diagnosing rainfall characteristics. Except for rainfall in the northeast part of India, Indian regional rainfalls are closely linked with surface wind speeds over the AS, and wind convergence and curl over the BoB on short timescales of up to 1 week. The daily area-averaged wind convergence over the BoB is better correlated with regional rainfall during strong ISMs than during weak ISMRs. Multiple linear regression analysis shows that the fluctuations of monthly wind fields in the AS and BoB can affect monthly rainfall in some regions but are not related to a significant change in rainfall over the whole India. It is the short-time fluctuations of wind speed over the AS as well as wind convergence and curl over the BoB rather than their long (monthly) timescale fluctuations that are related to the strength of ISMR. Surface winds over the SIO on weather timescales have little influence on ISMR.

The fluctuating climatic conditions of the Saharo-Arabian deserts are increasingly linked to human evolutionary events and societal developments. On orbital timescales, the African and Indian Summer Monsoons were displaced northward and increased precipitation to the Arabian Peninsula which led to favorable periods for human occupation in the now arid interior. At least four periods of climatic optima occurred within the last 130,000 years, related to Marine Isotope Stages (MIS) 5e (128–121 ka BP), 5c (104–97 ka BP), 5a (81–74 ka BP) and 1 (10.5–6.2 ka BP), and potentially early MIS 3 (60–50 ka BP). Stalagmites from Southern Arabia have been key to understanding climatic fluctuations and human-environmental interactions; their precise and high-resolution chronologies can be linked to evidence for changes in human distribution and climate/environment induced societal developments. Here, we review the most recent advances in the Southern Arabian Late Pleistocene and Early Holocene stalagmite records. We compare and contrast MIS 5e and Early Holocene climates to understand how these differed, benchmark the extremes of climatic variability and summarize the impacts on human societal development. We suggest that, while the extreme of MIS 5e was important for H. sapeins dispersal, subsequent, less intense, wet phases mitigate against a simplistic narrative. We highlight that while climate can be a limiting and important factor, there is also the potential of human adaptability and resilience. Further studies will be needed to understand spatio-temporal difference in human-environment interactions in a climatically variable region.

We conducted literature searches of records from Illinois, Indiana, Iowa, Minnesota, Missouri, North Dakota, Ohio, and Wisconsin to create a source bibliography of wildland fire descriptions occurring between 1673 and 1905. A total of 795 landscape fire records were identified within or near the eastern tallgrass prairie–forest transition region, including 32 attributed to Native Americans, 194 to Europeans from spontaneous records in the nineteenth century, and 569 to Europeans from a systematic dataset collected during the late nineteenth and early twentieth centuries in Minnesota. From these historical accounts, we find overwhelming evidence that a two- to three-week period during October and November, known then as “Indian summer,” was the primary wildland fire season. Our records indicate that Native Americans used fire primarily for hunting, whereas Euro-American fires were set to reduce fire hazards near their habitations, to eliminate crop residues, and to facilitate plowing, or they were escapes due to mere carelessness. Only five lightning-caused fires were identified. Individual fires frequently burned thousands of hectares, creating dense smoke, damaging trees, personal property, and occasionally burning inhabitants fatally. South and southwest were the most frequent wind directions during wildfires. Drought years, including 1796, 1819, 1856, and 1871, were characterized by extensive fires, which ultimately resulted in legislation to protect property owners and public welfare. Fire events for the study period are certainly underestimated by this dataset because only large, spectacular, threatening fires were recorded, especially during European settlement. In addition, our estimate of Native American fire frequency and prevalence is less than their historical/expected frequency, due to their widespread population collapse and changed hunting methods following contact and dispossession by Europeans.

This is an edited transcript of a conversation held in Thurloe Sq, London, on 25 July 2020. Peter Wilson’s exhibition ‘Indian Summer and Thereafter’ had opened at Betts Project the previous evening...

Nineteen thirty-eight was the last full season played by baseball slugger Lou Gehrig before amyotrophic lateral sclerosis (ALS) forced him to retire. He struggled to hit and field well for much of the season, and his final statistics -- a .295 batting average, 29 home runs, 114 runs batted in – were unusually low for him. But in mid-season, Gehrig enjoyed a streak in which he seemed to regain his previous power. This three-week stretch, not studied closely by neurologists or baseball historians until now, suggests that the “Iron Horse” may have experienced a temporary ALS reversal, which can be instructive for researchers and those coping with the disease.

Many of Ivo Petrić’s last works are orchestral. Some are related to his native Slovenia, while others are concertos for various solo instruments. They are normally in one movement, either showing some connection with traditional separate movements or multi-tempo works with numerous motivic interconnections.

Using nine model simulations from the PMIP3, we study simulated mean Indian summer (June–September) climate and its variability during the Last Millennium (LM; CE0850-1849) with emphasis on the Medieval Warm Period (MWP; CE1000-1199) and Little Ice Age (LIA; CE1550-1749), after validation of the simulated ‘current day (CE1850-2005)’ climate and trends. We find that the simulated above (below) mean-LM summer temperatures during the MWP (LIA) are associated with relatively higher (lower) moisture, and relatively higher (lower) number of concurrent El Ninos (La Ninas). Importantly, the models simulate higher (lower) Indian summer monsoon rainfall (ISMR) during the MWP (LIA) compared to the LM-mean, notwithstanding a strong simulated negative correlation between NINO3.4 index and the area-averaged ISMR. Interestingly, the percentage of the simulated strong El Ninos (La Ninas) associated with negative (positive) ISMR anomalies is higher (lower) in the LIA (MWP). This nonlinearity is explained by the simulated background climate changes, as follows. Distribution of simulated anomalous 850 hPa boreal summer velocity potential during MWP in models indicates, relative to the mean LM conditions, a zone of anomalous convergence in the central tropical Pacific flanked by two zones of divergence, i.e. a westward shift in the Walker circulation. The anomalous divergence centre in the west during the MWP also extends into the equatorial eastern Indian Ocean, triggering in an anomalous convergence zone over India and relatively higher moisture transport therein and therefore excess rainfall during the MWP as compared to the LM-mean, and hence an apparent weakening in the El Nino impact.

The sedimentology, geochemistry, and plant microfossils of volcanic lake sediments from Cambodia were analysed to reconstruct a 4700 year record of change in moisture availability. This site sits at the heart of the intersection zone of the East Asian and Indian summer monsoons – a climatic system that is socio-ecologically important but poorly understood. Proxies for lake deepening and shallowing indicate a stepwise weakening of the summer monsoon from c. 4700 to 1700 cal. years BP, after which it appears to gradually strengthen. This trend is punctuated by seven dry events between 4300 and 1540 cal. years BP. The results present one of the longest, continuous records of palaeo-hydrological change in the Asian monsoon intersection zone. In doing so, they suggest that the climate of the region was broadly comparable to the East Asian summer monsoon (EASM) province to approximately 2240 cal. years BP, and the Indian summer monsoon (ISM) province between 2240 and 1700 cal. years BP. The subsequent, late Holocene hydroclimate appears to reflect a combination of both subsystems. These findings highlight dynamism in EASM and ISM dominance over mainland southeast Asia over the past five thousand years, but overall demonstrate regional vs. local scale influence on the hydroclimate of the region. The multi-decadal periods of strong drying that punctuate longer-term monsoon patterns demonstrate the natural variability of the mid- to late- Holocene climate of the intersection zone. This is of consequence given that apparently less severe drought events of the last millennium have had dramatic socio-economic consequences. Resultantly, planning for the resilience of socio-ecological systems within the region needs to account for the real potential of similar scale events occurring in the future, particularly given the increased extremes predicted for Asian summer monsoon region over the 21st century.

Chlorophyll has long been known to influence air–sea gas exchange and CO2 drawdown. But chlorophyll also influences regional climate through its effect on solar radiation absorption and thus sea surface temperature (SST). In the Bay of Bengal, the effect of chlorophyll on SST has been demonstrated to have a significant impact on the Indian summer (southwest) monsoon. However, little is known about the drivers and impacts of chlorophyll variability in the Bay of Bengal during the southwest monsoon. Here we use observations of downwelling irradiance measured by an ocean glider and three profiling floats to determine the spatial and temporal variability of solar absorption across the southern Bay of Bengal during the 2016 summer monsoon. A two-band exponential solar absorption scheme is fitted to vertical profiles of photosynthetically active radiation to determine the effective scale depth of blue light. Scale depths of blue light are found to vary from 12 m during the highest (0.3–0.5 mg m−3) mixed-layer chlorophyll concentrations to over 25 m when the mixed-layer chlorophyll concentrations are below 0.1 mg m−3. The Southwest Monsoon Current and coastal regions of the Bay of Bengal are observed to have higher mixed-layer chlorophyll concentrations and shallower solar penetration depths than other regions of the southern Bay of Bengal. Substantial sub-daily variability in solar radiation absorption is observed, which highlights the importance of near-surface ocean processes in modulating mixed-layer chlorophyll. Simulations using a one-dimensional K-profile parameterization ocean mixed-layer model with observed surface forcing from July 2016 show that a 0.3 mg m−3 increase in chlorophyll concentration increases sea surface temperature by 0.35 ∘C in 1 month, with SST differences growing rapidly during calm and sunny conditions. This has the potential to influence monsoon rainfall around the Bay of Bengal and its intraseasonal variability.

India experienced two extreme summer monsoons, 2007 (active monsoon) and 2009 (weak monsoon) in the recent past decade. The characteristic features of these two contrasting Indian summer monsoons have been presented. The country received 11.8% excess and 17.1% deficit rainfall during 2007 and 2009 monsoon seasons, respectively. These large deviations in rainfall encourage us to study the influence of meteorological factors on rainfall activity. The distributions of rainfall over India, latent heat flux, wind, Vertically Integrated Moisture Transport (VIMT), and Vertically Integrated Moisture Divergence (VIMD) values in the layer 1000–300 hPa for the domain, 0°–40°N, 40°–120°E in the two contrasting monsoon seasons are evaluated. In active monsoon, (i) predominant low level southwesterly flow over the Arabian sea and deflection of winds over the Bay of Bengal, strengthening of the tropical easterly jet stream, wide area extent of easterlies in the upper troposphere, the maximum strength of easterlies in the upper troposphere (150 hPa) is observed over the area around 10°–15°N and 70°–75°E; (ii) position of subtropical ridge is more northward, i.e., 32°N; (iii) a predominant moisture transport in the layer 1000–300 hPa from Southern Hemisphere, Arabian Sea and the Bay of Bengal to the Indian mainland, westward/northward transport of moisture and area coverage of larger quantum of moisture flux is seen; and (iv) India experienced more number of mesoscale systems. The reverse is true for weak monsoon. Positive (neutral) Indian Ocean Dipole (IOD) and La-Nina (El-Nino) conditions lead to active (poor) summer monsoon conditions over India in 2007 (2009) year.

A comprehensive study on the Indian summer monsoonal rainfall (ISMR) is performed in the light of decadal changes in the continuous rainfall events and the number of rainy days using 68 years (1951–2018) of gridded rain gauge data. Non-parametric Mann–Kendall’s test is applied on total rainfall amount, the number of rainy days, number of continuous rainfall events, and rainfall magnitude to find trends over different climatic zones of India for the two periods, 1951–1984 and 1985–2018. Our results found a decreasing trend for more than 4-days of continuous rainfall events during the recent 34 years (1985–2018) compared to 1951–1984. The rate of increase/decrease in extreme/continuous rainfall events does not follow a similar trend in number of continuous rainfall events and magnitude. Moreover, the rainfall is shifted towards a lesser number of continuous rainfall days with higher magnitudes during 1985–2018. During the crop’s sow season (i.e., the first 45 days from the onset date of Indian monsoon), the total number of rainy days decreased by a half day during the last 34 years. Over the Central and North East regions of India, the number of rainfall days decreased by ~0.1 days/yr and ~0.3 days/yr, respectively, during 1985–2018. Overall, the decreasing trends in continuous rainfall days may escalate water scarcity and lead to lower soil moisture over rain-fed irrigated land. Additionally, an upsurge in heavy rainfall episodes will lead to an unexpected floods. On a daily scale, rainfall correlates with soil moisture and evaporation up to 0.87 over various land cover and land use regions of India. Continuous light-moderate rainfall seems to be a controlling factor for replenishing soil moisture in upper levels. A change in rainfall characteristics may force the monsoon-fed rice cultivation period to adopt changing rainfall patterns.

Corroboration of El Nino and Southern Oscillation (ENSO) events on the climatic variability in the Indian subcontinent is mentioned in various studies. In the Indian context, if we observe the rising number of dengue cases, it could be treated as a major cause of health concern for the government of this country. Nowadays, an increasing number of dengue incidences are reported from different Indian states which are leading to unfortunate hospitalization and fatal death of the people. Keeping the context in mind, we have examined the relationship between the ENSO events, inter-annual variability in dengue cases in major states of India and Indian summer monsoonal rainfall (ISMR). In this study, we use Pearson’s product-moment correlation (hereafter PPMC) to find out the interconnections between ‘+ winter ONI’ (OND, NDJ, DJF, and JFM seasons) events, rainfall index for the JJAS season (June, July, August, September) and annual 10 major state-level data of dengue cases index for the past 14 years. It has been observed through the study that the PPMC result between the ‘rainfall index’ and ‘dengue index’ is showing greater variation among different states of the country. Interestingly, we have observed that the correlation result between the ‘+ winter ONI’ and dengue incidence index have (r) value ranging from highly (−) to very high (+) value −0.53 to + 0.83 across the different states.

Indian Summer and Winter monsoon winds are major drivers of the mixed layer processes in the Arabian Sea. Our study shows that the Arabian Sea &lsq...

The plains of northwest South Asia receive rainfall during both the Indian summer (June–September) and winter (December–March) monsoon. Researchers have long attempted to deconstruct the influence of these precipitation regimes in paleoclimate records, in order to better understand regional climatic drivers and their potential impact on human populations. The mid–late Holocene transition between 5.3 and 3.3 ka is of particular interest in this region because it spans the period of the Indus Civilization from its early development, through its urbanization, and onto eventual transformation into a rural society. An oxygen isotope record of the surface-dwelling planktonic foraminifer Globigerinoides ruber from the northeast Arabian Sea provided evidence for an abrupt decrease in rainfall and reduction in Indus River discharge at 4.2 ka, which the authors linked to the decline in the urban phase of the Indus Civilization (Staubwasser et al., 2003). Given the importance of this study, we used the same core (63KA) to measure the oxygen isotope profiles of two other foraminifer species at decadal resolution over the interval from 5.4 to 3.0 ka and to replicate a larger size fraction of G. ruber than measured previously. By selecting both thermocline-dwelling (Neogloboquadrina dutertrei) and shallow-dwelling (Globigerinoides sacculifer) species, we provide enhanced detail of the climatic changes that occurred over this crucial time interval. We found evidence for a period of increased surface water mixing, which we suggest was related to a strengthened winter monsoon with a peak intensity over 200 years from 4.5 to 4.3 ka. The time of greatest change occurred at 4.1 ka when both the summer and winter monsoon weakened, resulting in a reduction in rainfall in the Indus region. The earliest phase of the urban Mature Harappan period coincided with the period of inferred stronger winter monsoon between 4.5 and 4.3 ka, whereas the end of the urbanized phase occurred some time after the decrease in both the summer and winter monsoon strength by 4.1 ka. Our findings provide evidence that the initial growth of large Indus urban centers coincided with increased winter rainfall, whereas the contraction of urbanism and change in subsistence strategies followed a reduction in rainfall of both seasons.

Loess and stalagmite records in China show different responses of Asian monsoon to the astronomical insolation during Marine Isotope Stage (MIS) 5c and 5e, raising the question whether the amplitudes of the whole Asian monsoon are linearly controlled by the astronomical summer insolation changes and whether the regional differences exist. In this study, a set of numerical experiments are conducted for these stages to examine the sensitivity of Asian summer monsoon to changes in the astronomical parameters. The results highlight a complicated response changing with regions and signals. The East Asian monsoon is remarkably stronger during MIS-5e, which is characterized by southerly winds, primarily due to the anomalous anticyclone over northwestern Pacific. The intensified East Asian monsoon leads to less precipitation in the eastern China and Japan but more in the further north and northwest. However, the Indian monsoon circulation does not vary significantly while the precipitation over Arabian Sea is significantly promoted by the upward air motion. Change in water vapor sources of Indian and Pacific Oceans qualitatively explains the observed differences in stalagmite δ18O records, implying that these proxy changes are primarily controlled by the water vapor delivery from oceans, at least on the astronomical timescale.

The Himalayas in the north part of Indian sub-continent is characterized by variable topography, heterogeneous landuse and climate variations. It acts as a barrier to atmospheric circulation for Indian summer and winter monsoon, thus modulating the associated precipitation over these regions. Western disturbances embedded in Indian winter monsoon (IWM) arriving from Mediterranean region result in one-third of annual precipitation over Himalayas. In the recent decade, studies have shown increased forcings associated with Arctic Oscillations (AOs). In the present study, impact of AO on IWM (December, January, February—DJF) is analyzed. During positive AO years, Polar region is having low surface pressure and colder conditions in comparison with higher pressure with cold surges to midlatitudes during negative AO years. For detailed analysis, National Center of Environmental Prediction/National Center for Atmospheric Research, US reanalysis data is used. Analysis of positive and negative AO year composites shows stronger westerlies over Arabian Sea and neighboring Indian region. Stronger north–south temperature gradient due to warmer Indian Ocean and colder Tibetan region is seen during positive AO years. In addition, weakening of Hadley circulation is seen during positive AO years. This weakening helps in Polar and/or extratropical mass to move southwards having mid-latitude interactions leading to enhanced precipitation over Indian regions. Extensive and intense wave train seen during positive AO years indicates Rossby wave response. Such forcings associated with AOs led to increased precipitation over the northern Indian region.

This study undertakes a comprehensive assessment of dynamical downscaling of summer monsoon (June–September; JJAS) rainfall over heterogeneous regions namely the Western Ghats (WG), Central India (CI) and North-Eastern Region (NER) for long term mean, excess and deficit episodes for the historical period from 1951 to 2005. This downscaling assessment is based on six Coordinated Regional Climate Downscaling Experiments (CORDEX) for South Asia (SAS) region, their five driving Global Climate Models (GCM) simulations along with observations from India Meteorological Department (IMD) and Asian Precipitation Highly Resolved Observational Integrated Towards Evaluation for Water Resources (APHRODITE). The analysis reveals an overall reduction of dry bias in rainfall across the regions of Indian sub-continent in most of the downscaled CORDEX-SAS models and in their ensemble mean as compared to that of driving GCMs. The interannual variabilities during historical period are reasonably captured by the ensemble means of CORDEX-SAS simulations with an underestimation of 0.43%, 38% and 52% for the WG, CI and NER, respectively. Upon careful examination of the CORDEX-SAS models and their driving GCMs revealed considerable improvement in the regionally downscaled rainfall. The value addition of dynamical downscaling is apparent over the WG in Regional Climate Model (RCM) simulations with an improvement of more than 30% for the long term mean, excess and deficit episodes from their driving GCMs. In the case of NER, the improvement in the downscaled rainfall product is more than 10% for all the episodes. However, the value addition in the CORDEX-SAS simulations for CI region, dominantly influenced by synoptic scale processes, is not clear. Nevertheless, the reduction of dry bias in the complex topographical regions is remarkable. The relative performance of dynamical downscaling of rainfall over complex topography in response to local forcing and orographic lifting depict the value addition (30% over WG and 10% over NER, with a statistical significance of more than 5% level), when compared with the synoptic scale system induced rainfall over the plains of central-India.

The Indian and East Asian summer monsoons are two active components of the global monsoon system and are closely related. However, their relationship is weakened after the late 1970s. This study revisited the possible mechanism for the weakening relationship between Indian and central East Asian summer rainfall, focusing on the influence from the middle-to-high-latitude climate system. The results show that variability in the summer North Atlantic Oscillation since the late 1970s induces a zonal atmospheric teleconnection pattern, resulting in anomalous upper level atmospheric circulation south of the Baikal Lake, which is further closely related to central East Asian summer rainfall over the period after the late 1970s. When the signal of the atmospheric circulation variability south of the Baikal Lake is removed, the relationship between the Indian and central East summer rainfall becomes significant again over the period after the late 1970s. The summer North Atlantic Oscillation thus opposes the influence of the Indian summer rainfall on central East Asian summer rainfall, consequently contributing to the breakdown of the Indian–central East Asian summer rainfall relationship after the late 1970s.

Previous studies have shown that the Atlantic Multidecadal Oscillation (AMO) can play an important role in modulating the variability of Indian summer monsoon rainfall (ISMR) over a 50–60-yr timescale. A significant positive correlation between the AMO and ISMR is found both in observations and models. However, instrumental records show that the relationship becomes non-significant or even of opposite sign after the mid-1990s, suggesting a weakening of the AMO–ISMR connection. The mechanism for the breakdown of the AMO–ISMR connection is investigated in the present work, and the results suggest that a substantial warming in the Indian–tropical western Pacific Ocean plays a role. The warming weakens the meridional gradient of tropospheric temperature between Eurasia and the Indian Ocean, and reduces the meridional sea level pressure gradient between the Indian Subcontinent and Indian Ocean, weakening the Indian summer monsoon. Thus, warming in the Indian–tropical western Pacific Ocean seems responsible for the weakened connection between the AMO and ISM.

Previous studies have found a link between north China and Indian rainfall during summer, with significantly increased rainfall in north China related to a stronger Indian summer monsoon. This link is weakened after the late 1970s, generally attributed to the reduced magnitude of interannual variability in the Indian summer rainfall. This study reveals a similar change in this rainfall link in early summer after the late 1970s. Related to a heavier Indian early summer rainfall, rainfall in north China enhances significantly before the late 1970s but not thereafter. The change in rainfall teleconnection is caused by the weakened impact on north China rainfall of a midlatitude wave train along the Asian jet in the upper troposphere. After the late 1970s, the portion of the wave train over East Asia displaces eastward, leading to an eastward shift in the associated ascending motion and, subsequently, enhanced rainfall from north China to the Yellow Sea. Moreover, the change in the midlatitude wave train is attributed to the change in the basic state over East Asia (i.e., a northward shift of the East Asian upper-tropospheric westerly jet after the late 1970s). The latter reduces stationary Rossby wavenumber and increases wavelength of the midlatitude wave train, leading to an eastward shift of the wave train over East Asia. Therefore, in this study a mechanism is proposed for the change in early summer, different from the previous mechanism for the entire summer period.

The article is dedicated to the investigation of the two-component nominative unit “Indian Summer” meaning a period of warm weather in autumn. The analysis of the dictionary entries was done, possible theories of its origin were given and the ways of its motivation were found. We used the method of cognitive onomasiological analysis that consists of two stages: the interpretation of the onomasiological structure of the nominative unit and the simulation of the corresponding structure of knowledge about the unit nominated. 5 theories of the origin of the lexical unit “Indian Summer” were found. Each of them has different type of motivation of nomination. The unit investigated has both direct and indirect meanings that can be explained by the significance of the notion in the minds of people. “Indian Summer” is the realia of North America but its lexical equivalents are used all over the world to denote the climatic phenomenon of unusually warm weather in autumn.

Previous studies have indicated a connection between interannual variations of the Indian and North China summer rainfall. An atmospheric circulation wave pattern over the mid-latitude Asia plays an important role in the connection. The present study compares the influence of the above-normal and below-normal Indian summer rainfall on the North China summer rainfall variations. Composite analysis shows that the mid-latitude Asian atmospheric circulation and the North China rainfall anomalies during summer tend to be anti-symmetric in above-normal and below-normal Indian rainfall years. Analysis indicates that the Indian-North China summer rainfall relation tends to be stronger when larger Indian rainfall anomaly occurs during a higher mean rainfall period. The observed long-term change in the Indian-North China summer rainfall relationship cannot be explained by the impact of the El Nino-Southern Oscillation (ENSO). The present study evaluates the Indian-North China summer rainfall relationship in climate models. Analysis shows that the Indian-North China summer rainfall relationship differs largely among different climate models and among different simulations of a specific model. The relationship also displays obvious temporal variations in both individual and ensemble mean model simulations. This suggests an important role of the atmospheric internal variability in the change of the Indian-North China summer rainfall relationship.

In 1977, Jean Rouch visited New York to show his films at the first Margaret Mead Film Festival. Later, he returned to the United States to make his cine-portrait of Mead, and he was invited to teach film workshops in the Boston area. He coined the term “Indian Summer School” for these programs. I taught visual anthropology with Rouch at Harvard Summer School from 1980 to 1986. America fascinated Rouch; he, meanwhile, bewildered his students. In the 1980s, Africa was remote from the consciousness of most Americans, and filmmakers of color were not empowered. Rouch’s films and cinematic inventions opened the students up to new fields, and to the possibility of seeing and representing African societies.

Статья посвящена рассмотрению реализации мотива двойничества в творчестве А. Штифтера на примерах повестей «Полевые цветы», «Горный лес», «Записки моего прадеда» и романа «Бабье лето». Устанавливается способ взаимодействия двойников в каждом произведении и смысл удвоения в системе образов. The paper studies how the motive of the duality is realized in the works of A. Stifter, such as “Feldblumen”, “Der Hochwald”, “Die Mappe meines Urgrossvaters” and the novel “Indian summer”. We look for the way how counterparts interact in each work and what role plays doubling in the system of images.

Hydroclimatic variations during the summer monsoon season (June–September) across the Himalaya are examined over the past several hundred years using tree-ring oxygen isotope records. Owing to their strong associations with hydroclimatic variables including precipitation, relative humidity, and the Palmer Drought Severity Index, tree-ring δ18O chronologies from the Himalaya can be used to reconstruct summer monsoon intensity precisely. A regional chronology derived from five local chronologies across the Himalaya shows a significant correlation with Indian summer rainfall data. One of the most noteworthy features of the regional chronology is a drying trend over the past 180 years, indicating that summer monsoon intensity in the Himalayan region has weakened. A declining land–ocean thermal gradient over South Asia seems to be responsible for the weakened summer monsoon. By analyzing spatio-temporal correlations between zonally distributed tree-ring data over the Himalaya, we also explore possible changes in the relative contributions of source water originating in the Arabian Sea and the Bay of Bengal.

The responses of Asian monsoon subsystems to both hemispheric climate forcing and external orbital forcing are currently issues of vigorous debate. The Indian summer monsoon is the dominant monsoon subsystem in terms of energy flux, constituting one of Earth’s most dynamic expressions of ocean–atmosphere interactions. Yet, the Indian summer monsoon is grossly under-represented in Asian monsoon palaeoclimate records. Here, we present high-resolution records of Indian summer monsoon-induced rainfall and fluvial runoff recovered in a sediment core from the Bay of Bengal across Termination II, 139–127 thousand years ago, including coupled measurements of the oxygen isotopic composition and Mg/Ca, Mn/Ca, Nd/Ca and U/Ca ratios in surface-ocean-dwelling foraminifera. Our data reveal a millennial-scale transient strengthening of the Asian monsoon that punctuates Termination II associated with an oscillation of the bipolar seesaw. The progression of deglacial warming across Termination II emerges first in the Southern Hemisphere, then the tropics in tandem with Indian summer monsoon strengthening, and finally the Northern Hemisphere. We therefore suggest that the Indian summer monsoon was a conduit for conveying Southern Hemisphere latent heat northwards, thereby promoting subsequent Northern Hemisphere deglaciation. During deglacial warming at Termination II, about 130,000 years ago, the Indian summer monsoon helped convey heat northwards as deglaciation progressed from the Southern to the Northern Hemisphere, according to sediment records from the Bay of Bengal.

The Indian subcontinent receives most of its annual precipitation due to Indian summer (June, July, August and September) monsoon. Southeastern coastal region of the India receives significant amount of precipitation due to the northeast monsoon (October and November). Over northern Indian region almost one-third of annual precipitation is received during winter (December, January and February) by eastward moving extratropical cyclone called ‘western disturbances (WDs)’ in Indian meteorological parlance. Various studies are conducted to understand the Indian summer and northeast monsoons. However, the dynamics and characterization of winter precipitation is not well understood except with reference to the western disturbances (WDs). In this study, wintertime dynamics associated with large-scale flows and WDs influencing winter precipitation is proposed and termed ‘Indian winter monsoon’. In addition, winter precipitation – the Indian winter monsoon – is proposed as eastward traveling WDs embedded in the large-scale subtropical westerlies over the Indian sub-continent. During winter (December, January and February) upper level subtropical westerly jet moves southwards and passes over the Indian sub-continent and provides associated precipitation over the northern Indian region. With concurrent research and changing global context, increased understanding of the Indian winter monsoon is imperative. Equally important is the behavior of WDs showing different patterns in the Peninsular India and the Himalaya particularly during the Holocene. During the Little Ice Age (LIA), it appears that high frequency of El Nino events was responsible for drier conditions in the core monsoon zone but generated more monsoon “breaks” over the Himalaya and thus the climatic conditions in the core Indian summer monsoon area were generally opposite to those in the foothills of the Himalaya during the Holocene period. During this period, a higher frequency of El Nino events might have restricted transport of warm water to the North Atlantic Ocean and brought about a cooling of adjacent continents including Central Asia and this may have amplified the extent of snow over Asia during the winter, and may even have been accounted for early snow in the region at the expanse of reduction in the Indian summer monsoon strength. Thus, this study delineates the Indian winter monsoon at intraseasonal-sub seasonal-interannual-paleoclimate scale and provides comprehensive details on defining the Indian winter monsoon and makes an attempt to understand the WDs particularly from mid-Holocene onwards as well.

Hydroclimatic process in the Yarlung Tsangpo River (YTR) basin, a sensitive area to climate change, is obviously changing during recent years, but there has limited understanding about it. In this study, we investigated the spatiotemporal variation of precipitation over last four decades in the basin and the impact thereon of the changing Indian summer monsoon at interannual and decadal time scales. All the precipitation series have similar scaling behavior, reflecting similar climatic regime throughout the basin. However, the effect of the Indian monsoon strengthens from the downstream to upstream, causing spatial variability in the seasonal distribution of precipitation, and on this basis, the YTR basin is roughly divided into three regions: east, middle, and west. Both the occurrence times and magnitude of precipitation extremes, ranging 25-50mm/d, are exhibiting downward trends over the last four decades, which bodes well for water disaster controls in the basin. The Indian summer monsoon index, as an intensity indicator for the Indian summer monsoon, shows a positive relationship with the summer precipitation in the YTR basin. Periodic variability of the Indian monsoon determines the interannual nonstationary fluctuations of precipitation. Especially, the weakening effect of the Indian summer monsoon has caused an obvious decrease in precipitation over the rainy season after 1998. If the Indian summer monsoon keeps weakening, the precipitation would decrease and potentially water shortage would become more severe in the basin. Effective adaptation strategy should therefore be developed proactively to handle the unfavorable water situation, which is likely to occur in the future.

The El Nino–Southern Oscillation (ENSO) is a main driving force of the northern hemisphere summer monsoon rainfall, including the Indian Summer Rainfall (ISR). The impacts of typical ENSO and atypical ENSO events on the ISR remain unclear during their developing summers. This study examines the different linkages between a typical ENSO and the ISR and between an a typical ENSO and the ISR. During the developing summer of a typical El Nino, negative rainfall anomalies are seen over the northeastern Indian subcontinent, while the anomalous rainfall pattern is almost the opposite for a typical La Nina; as for an atypical ENSO, the approximate “linear opposite” phenomenon vanishes. Furthermore, an anomalous global zonal wave train is found at mid-latitudes, with a local tripole circulation pattern over central–eastern Eurasia during the developing summer of a typical ENSO, which might explain the corresponding rainfall response over the Indian Peninsula. By contrast, such features are not obvious duri...

Prediction of Indian summer (June–September) rainfall on regional scales remains an open issue. The operational predictions of West Central Indian summer rainfall (WCI-R) and Peninsular Indian summer rainfall (PI-R) made by the Indian Meteorological Department (IMD) had no skills during 2004–2012. This motivates the present study aiming at better understanding the predictability sources and physical processes governing summer rainfall variability over these two regions. Analysis of 133 year data reveal that although the lower boundary forcing that associated with enhanced WCI-R and PI-R featured a similar developing La-Nina and “east high west low” sea-level pressure (SLP) dipole pattern across the Indo-Pacific, the anomalous high sea surface temperature (SST) over the northern Indian Ocean and weak low pressure over northern Asia tended to enhance PI-R but reduce WCI-R. Based on our understanding of physical linkages with the predictands, we selected four and two causative predictors for predictions of the WCI-R and PI-R, respectively. The intensified summer WCI-R is preceded by (a) Indian Ocean zonal dipole-like SST tendency (west-warming and east-cooling), (b) tropical Pacific zonal dipole SST tendency (west-warming and east-cooling), (c) central Pacific meridional dipole SST tendency (north-cooling and south-warming), and (d) decreasing SLP tendency over northern Asia in the previous season. The enhanced PI-R was lead by the central-eastern Pacific cooling and 2-m temperature cooling tendency east of Lake Balkhash in the previous seasons. These causative processes linking the predictors and WCI-R and PI-R are supported by ensemble numerical experiments using a coupled climate model. For the period of 1871–2012, the physics-based empirical (P-E) prediction models built on these predictors result in cross-validated forecast temporal correlation coefficient skills of 0.55 and 0.47 for WCI-R and PI-R, respectively. The independent forecast skill is significantly higher than the skill of operational seasonal forecast made by the IMD for the period of 2004–2012. These prediction models offer a tool for seasonal prediction and their retrospective forecast skills provide an estimation of the lower bound of the predictability for WCI-R and PI-R.

Monthly correlation of Indian monsoon rainfall (IMR) index with various monsoon indices changes predominantly and peaks within summer season (Ailikun and Yasunari, 2001). There is transition in this lead and lagged correlation during spring (March, April and May). This spring transition could not be captured in many general circulation models (GCMs) and is termed as “predictability barrier” (Latif and Graham, 1991). It has been less investigated and hence reasons for dampening/reversal of associated large scale fields during spring are intriguing. Present study illustrates dynamics of spring predictability barrier with Indian summer (June, July, August and September) monsoon (ISM). In this study, based on data from 1979 to 2008, an internal dynamics between various monsoon indices and corresponding IMR anomaly is diagnosed. It is found that secular behaviour of El Nino– Southern Oscillation (ENSO) during preceding spring of monsoon months (June, July, August and September) gets reversed in succeeding spring. Though correlation between various monsoon indices and ISM index remains similar during preceding and succeeding springs with peaks during monsoon (June, July, August and September), corresponding large scale fields show that strong significant convection dominates over the southern equatorial eastern Pacific Ocean, northern equatorial western Pacific Ocean, Indonesian throughflow and weaker significant convection dominates over the Head Bay of Arabian Sea and western to central Indian sub-continent during preceding spring. Such patterns reverse during succeeding spring.

The onset/progression phase of theIndian summer monsoon (ISM) is very crucial for the agricultural sector of the country as it has strong bearing on the sowing of kharif crops, which in turn affects overall food grain production and hence food security. The recent ISMs of 2013 and 2014 exhibited quite distinct progression phases. While 2013 had one of the fastest advancement in the last 70 years, 2014 witnessed a comparatively lethargic progression phase. The major difference was felt in the early monsoon month of June, with 2013 (2014) monthly rainfall being +34% (−43%) of its long period average. Observational investigations reveal that, during June 2013, the monsoon trough was very active in its normal position favouring low-level positive vorticity generation and moisture convergence, whereas the absence of monsoon trough during June 2014 facilitated the prevalence of a strong low-level anticyclonic circulation over central India hampering the northward progression of the ISM. It is found that June 2013 (2014) was associated with (i) stronger (weaker) north-south tropospheric temperature (TT) gradient with positive (negative) TT anomalies over Eurasia and north of 60°N; (ii) negative (positive) SST anomalies over the equatorial Indian Ocean, northwestern Arabian Sea and equatorial eastern Pacific; (iii) stronger (weaker) monsoonal Hadley circulation; and (iv) stronger (weaker) Walker circulation in response to the negative (positive) SST anomalies over the equatorial Pacific. The study also examines the skill of an Ensemble Prediction System (EPS) in predicting the observed contrasting behaviour during June 2013/2014 on extended range (∼15–20 days in advance) in real time. The EPS not only forecasted the observed discrepancy, but also predicted the influential role of the large-scale meteorological conditions prevalent during June 2013 (2014), thus demonstrating the remarkable skill of the EPS in predicting June extremes.

The climate and hydrology of the Western Himalayas is complex and a function of snow and glacier melt, land use, topography, and Indian summer and winter monsoon dynamics. Improving our knowledge about these processes is important from societal and agricultural points of view. In this study, an observational analysis is carried out to assess the changing climatic trends and the associated interannual variability in winter temperature and precipitation at three glacierized regions of Western Himalayas having distinctly different sub-regional characteristics. In situ observations of 23 years (1985–2007) are used. These observations are passed through rigorous statistical quality control checks. Results show higher interannual variability with increasing temperature trends in the glacierized regions of the Siachen (Karakoram Range) and Chotasigri (Great Himalayan Range). Karakoram Range has higher warming trends than the Great Himalayan Range. In case of precipitation, an overall decrease in precipitation is observed with contrasting trends in the last decade. Nino3.4 index is positively correlated with winter precipitation with similar interannual variability. In addition, at Siachen temperature and precipitation show strong negative correlation, and precipitation to spell length correlation is opposite at Siachen and Chotasigri.

The plains of northwest South Asia receive rainfall during both the Indian Summer (June–September) and Winter (December–March) Monsoon. Researchers have long attempted to deconstruct the influence of both precipitation regimes in paleoclimate records, in order to better understand regional climatic drivers and their potential impact on human populations. The Mid–Late Holocene transition between 5.3–3.3 ka BP is of particular interest in this region because it spans the period of the Indus Civilization from its early development to eventual transformation. The oxygen isotope record of the surface-dwelling planktonic foraminifer Globigerinoides ruber from the northeast Arabian Sea provided evidence for an abrupt decrease in rainfall and reduction in Indus River discharge at 4.2 ka BP, which the authors linked to the decline of the urban phase of the Indus Civilization (Staubwasser et al., 2003). Given the importance of this study, we used the same core (63KA) to replicate the oxygen isotope profiles of a larger size fraction of G. ruber than measured previously and, in addition, we measured two other foraminifer species at decadal resolution over the interval from 5.4 to 3.0 ka BP. By selecting both thermocline-dwelling (Neogloboquadrina dutertrei) and shallow-dwelling (Globigerinoides sacculifer) species, we provide enhanced detail of the climatic changes that occurred over this crucial time interval. We found evidence for a period of increased surface water mixing, which we suggest was related to a strengthened winter monsoon with a peak intensity over 200 years from 4.5 to 4.3 ka BP. The time of greatest change occurred at 4.1 ka BP when both the summer and winter monsoon weakened, resulting in a reduction in rainfall in the Indus region. The earliest phase of the Mature Harappan period coincided with the period of inferred stronger winter monsoon between 4.5–4.3 ka BP, whereas the end of the urbanized phase followed the decrease in both the summer and winter monsoon strength by 4.1 ka BP. Our findings provide evidence that the initial growth of large Indus urban centers was coincident with increased winter rainfall, whereas the contraction of urbanism and change in subsistence strategies followed a reduction in rainfall of both seasons.

Atmospheric CH4 observations from two ground-based stations within Indian subcontinent, namely, Sinhagad (SNG) and Cape Rama station (CRI) showed a strong seasonality with a minima (∼1800 ± 20 ppb) during southwest monsoon (SWM; i.e. June–September, JJAS) and a maxima (2000 ± 30 ppb) during northeast monsoon (NEM i.e. December–February, DJF) with a peak-to-peak seasonality close to 200 ppb. The Indian summer (winter) monsoon is characterized with strong southwesterly (northeasterly) winds of oceanic (land) origin at the surface level and strong easterly (westerly) jet streams aloft. The monsoon dynamics has pronounced impact on CH4 variability over India and is analyzed with winds, Lagrangian trajectories, and 3-dimentional distributions of CH4 simulated by a general circulation model. The model simulations suggest a consistent annual vertical structure (mean and sub-seasonal uncertainty) of CH4 over India with a stark contrast in concentration from summer to winter at surface levels (below 750 mb) in confirmation with what is identified by the ground-based observations. During SWM (NEM) the air with comparatively lower (higher) CH4 concentrations from southern (northern) hemisphere reduces the CH4 over India by 1814 ± 26 ppb (enhances by 1950 ± 51 ppb). The contribution of local fluxes to this seasonality appears to be albeit weak as the synthesized CH4 fluxes (from EDGAR dataset) of the Indian peninsula itself show a peak in summer and a dip in winter. Similar property of CH4 is also common to nearby oceanic region (i.e. over Arabian Sea, 1765 ± 10 ppb during summer) suggesting the role of monsoon dynamics as the controlling factor. Further the mixing and convection carries the CH4 to the upper atmosphere and advect inward or outward aloft according the seasonal monsoon dynamics.

In this paper, the impact of the SST drifts in the ECMWF system 3 forecasting system on the simulated monsoon climatology is investigated. It is shown that hindcasts initialized in February show paradoxically better climatological rainfall in the early monsoon season compared to the hindcasts initialized in the May. The differences in rainfall and SST evolution in the two hindcast sets point to the SST differences as the crucial factor that improves the February initialized hindcasts. Further experiments with the atmospheric component of the ECMWF system 3 forecasting system confirm this by showing similar rainfall biases in the early monsoon season as the hindcasts initialized in the May. This study points to the potential beneficial impacts of reducing systematic biases in the atmospheric components forecasting systems, and of an anomaly initialization technique to improve Indian Monsoon forecasts.