Abstract Significant increase in the frequency of occurrences rainfall extremes has been reported over several parts world. These extreme events were defined at individual grids without considering their spatial extent. Here, using ground-based observations India during boreal summer, we show that average size spatially collocated significantly increasing since 1980. However, such remains unchanged. Around 90% total number large-sized (area ≥ 70 × 10 3 km 2 ) our study period (1951 to 2015)...

Abstract To predict how monsoons will evolve in the 21st century, we need to understand they have changed past. In paleoclimate literature, major focus has been on role of solar forcing but not amplification by feedbacks internal climate system. Here used results from a transient simulation show that amplify effect change insolation Indian summer monsoon. We during deglacial (22 ka 10 ka) were predominantly influenced rising water vapor due increasing sea surface temperature, whereas...

Abstract. Lightning activity constitute the major destructive component of thunderstorms over India. Hence, an understanding long-term variability in lightning occurrence and intensity their interrelation with various causative factors is required. Long-term (1998–2014) Tropical Rainfall Measuring Mission (TRMM) satellite-based observations depict most frequent occurrences along Himalayan foothills, Indo-Gangetic plains coastal regions, while these strikes found to be strongest regions Bay...

Abstract The simulation characteristics of the Asian–Australian monsoon are documented for Community Climate System Model, version 4 (CCSM4). This is first part a two series examining regimes in global tropics CCSM4. Comparisons made to an Atmospheric Model Intercomparison Project (AMIP) atmospheric component CCSM4 [Community Atmosphere 4, (CAM4)] deduce differences simulations run with observed sea surface temperatures (SSTs) and ocean–atmosphere coupling. These also compared previous model...

The existing theories for the tropical teleconnections to Indian summer monsoon (ISM) are diverse in approaches. As a result, it is impossible quantify relative impacts of different climate patterns on ISM, complying with single physical mechanism. Here, we show that ISM can be explained through net moisture convergence driven by surface pressure (Ps) gradients surrounding region. positive and negative phases major modulate these asymmetrically zonal and/or meridional directions leading...

Abstract In recent years India has been increasingly experiencing widespread floods induced by large‐scale extreme rainfall events (LEREs). LEREs are mainly associated with monsoon low‐pressure systems (LPS). The forecast of these high‐flood‐potential events, however, remained challenging. Here, we compare LPSs the summer that led to (LPS‐Lg) and strong did not result in (LPS‐noLg) over central for period 1979–2012. We show having a LPS is sufficient condition produce LEREs, LPS‐Lgs...

Role of Asian and African orography in the Indian summer monsoon has been investigated using a general circulation model. Orography region west 80°E appears to have more impact on rainfall than east 80°E. It found that removal increases seasonal precipitation over sub‐continent by 28%, whereas entire globe reduces it 25%. Moreover, there was substantial delay all‐India onset experiment which mountains were removed globally, mainly due intrusion midlatitude dry air The increase Africa...

Abstract. A theory is proposed to determine the onset of Indian Summer Monsoon (ISM) in an Atmospheric General Circulation Model (AGCM). The ISM delayed substantially absence global orography. impact orography over different parts Earth on has also been investigated using five additional perturbed simulations. large difference date these simulations explained by a new based Surface Moist Static Energy (SMSE) and vertical velocity at mid-troposphere. It found that occurs only after SMSE...

Abstract The low‐level jet (LLJ) over the Indian region, which is most prominent during monsoon (June–September) season, has been studied with a general circulation model (GCM). role of African orography in modulating this focus article. presence intensifies cross‐equatorial flow. Contrary to previous modelling studies we find that flow occurs even absence orography, though much weaker when rainfall high. However, location meridional near equator Somali region linked rather than land–sea...

Abstract The Indian summer monsoon (ISM) shows quasi-rhythmic intraseasonal oscillations (ISO) manifested as alternate ‘active’ phases of copious rainfall and quiescent ‘break’. Within these periodic phases, the daily large variability exhibits spatiotemporally sporadic extreme events. recent decades have witnessed a significant increase in number events, especially phases. This is accompanied by decreasing trend mean weakening variance its low-frequency ISO (LF-ISO) cycle. However, any...

Abstract. The changes in Earth's precession have an impact on the tropical precipitation. This has been attributed to seasonal solar radiation at top of atmosphere. primary mechanism that proposed is change thermal gradient between two hemispheres. may be adequate understand zonal mean changes, but cannot explain variations land and oceans. We used a simple model intertropical convergence zone (ITCZ) unravel how precipitation with precession. Our attributes energy fluxes vertical stability....

Abstract In this study, rainfall estimates by the Tropical Rainfall Measuring Mission are used to understand spatiotemporal structures of convection in intraseasonal time scale and their intensity during boreal summer over South Asia. A quantitative analysis on how these modes modulate central Indian is also provided. Two dominant variability with periodicities 10–20 20–60 days found, latter strongly modulated sea surface temperature. The 20–60-day mode shows northward propagation from...

Using rain-gauge measurements and reanalysis data sets for 1948–2015, we propose a mechanism that controls the interannual variation of summer monsoon onset over central India. In May, about month before onset, low level jet Arabian Sea is 40% stronger 2.5 degrees northward during years early as compared to late onset. A shifted carries 50% more moisture in years, which increases moist static energy India pre-monsoon season. The increase decreases stability atmosphere makes it conducive convection.

Abstract The South Asian summer monsoon has been suggested to be influenced by atmospheric aerosols, and this influence can the result of either local or remote emissions. We have used Hadley Centre Global Environment Model Version 3 (HadGEM3) coupled atmosphere‐ocean climate model investigate for first time centennial‐scale precipitation response emissions sulfur dioxide (SO 2 ), dominant anthropogenic precursor sulfate aerosol, from different midlatitude regions. Despite localized nature...

This paper addresses the problem of designing an efficient implementation a basic atomic read-write data structure over asynchronous message-passing system. In particular, we consider time-efficient implementations this abstraction in case single writer, multiple readers (also called SWMR register) and S servers: readers, t out servers may fail by crashing. Previous tolerate failure any minority (i.e., < S/2) require one communication round-trip for every write, two round-trips read.We...

Understanding the changing nature of intraseasonal oscillatory (ISO) modes Indian summer monsoon manifested by active and break phase, their association with extreme rainfall events are necessary for probabilistic estimation flood-related risks in a warming climate. Here, using ground-based observed rainfall, we define an index to measure strength ISOs show that relative northward-propagating low-frequency ISO (20–60 days) have had significant decreasing trend during past six decades,...

Abstract Improved seasonal prediction of sea surface temperature (SST) anomalies over the global oceans is theme this paper. Using 13 state-of-the-art coupled atmosphere–ocean models and yr forecasts, performance individual models, ensemble mean, bias-removed Florida State University (FSU) superensemble are compared. A total 23 400 forecasts based on 1-month lead times were available for study. Evaluation metrics include both deterministic probabilistic skill measures, such as verification...

Abstract The availability of daily observed rainfall estimates at a resolution 0.5° × latitude–longitude from collection over 2100 rain gauge sites India provided the possibility for carrying out 5-day precipitation forecasts using downscaling and multimodel superensemble methodology. This paper addresses forecast performances regional distribution predicted monsoon rains addition superensemble. extent prediction improvements that arise above those current suite operational models are...

Accumulation of pollution over the southern Arabian Sea has been documented in numerous studies that followed INDOEX field project 1992. In this paper, we show several examples feature from MODIS/CALIPSO data sets. We identify as Bombay Plume makes its way into west coast India. A second part work is on modeling impacts pollution. use a NASA Goddard Earth Observing System (GEOS) model to carry out many comparative forecast simulation experiments include based MODIS and control runs utilize...

Abstract The impact of heating by black carbon aerosols on Indian summer monsoon has remained inconclusive. Some investigators have predicted that reduce rainfall while others argued it will increase rainfall. These conclusions been based local influence the radiative fluxes. aerosol‐like in one region a remote not examined detail. Here, using an atmospheric general circulation model, shown can be as important monsoon. Precipitation northern Arabian Sea and north‐west increased 16% June to...

Leaving out the strong El Niño Southern Oscillation (ENSO) years, our understanding in interannual variation of Indian summer monsoon rainfall (ISMR) stands poor for rest. This study quantifies role ENSO preceding winter on ISMR with a particular emphasis ENSO-neutral and La Niña winter. Results show that, unlike simultaneous ENSO-ISMR relationship, previous reduces mean over country by about 4% even during neutral summer. Moreover, when changes phase from to summer, is anomalously lower...