Sabin T P

• PhD
• Scientist at Indian Institute of Tropical Meteorology

Western disturbances (WDs) are synoptic-scale weather systems embedded within the subtropical westerly jet. Manifesting as upper-level troughs often associated with a lower-tropospheric low over western or northern India, they share some dynamical features with extratropical cyclones. WDs are most common during the boreal winter (December to March)...

The large-scale convection during the Asian summer monsoon plays an important role in the rapid transport of boundary layer aerosols into the Asian summer monsoon anticyclone. Here, using the state-of-the-art ECHAM6–HAMMOZ aerosol-chemistry-climate model, we show that these aerosols are further transported to the Arctic along isentropic surfaces by...

Western disturbances (WDs) are synoptic-scale weather systems embedded within the subtropical westerly jet. Manifesting as upper-level troughs often associated with a lower-tropospheric low over Western India, they share some dynamical features with extratropical cyclones. WDs are most common during the boreal winter (December to March), during whi...

The rapid melting of glaciers in the Hindu Kush Himalayas (HKH) during recent decades poses an alarming threat to water security for larger parts of Asia. If this melting persists, the entirety of the Himalayan glaciers are estimated to disappear by end of the 21st century. Here, we assess the influence of the spring 2020 COVID-19 lockdown on the H...

This study investigates the projected changes in the upper troposphere and lower stratosphere (UTLS) water vapor over the Asian summer monsoon (ASM) region based on satellite records, numerical simulations using variable-resolution global climate model focused over south Asia (HIST-natural and anthropogenic forcing in the historical period, and FUT...

Evapotranspiration (ET) is the primary process of water transfer in the hydrological cycle over land and is linked to water, energy and carbon cycles. While the global hydrological cycle is expected to intensify in a warming climate with enhanced ET and precipitation, the magnitude and spatial distribution of regional scale response of ET to climat...

This study addresses the role of human-induced climate change on the interactions of convective activities between the Indian summer monsoon (ISM) and western North Pacific (WNP) regions - an important scientific issue which has been hitherto overlooked. We have examined this problem using two numerical experiments of a high-resolution climate mode...

Northern Hemispheric summer monsoons were more intense during the mid-Holocene (MH ~ 6000 years ago) and coincided with a northward shift of the Intertropical Convergence Zone (ITCZ) compared to the pre-industrial (PI) climate. Ancient civilizations in the Indus valley, Mesopotamia, and Egypt appear to have flourished during this period, thanks to...

The rapid melting of glaciers in the Hindu Kush Himalayas (HKH) during recent decades poses an alarming threat to water security for lager parts of Asia. If this melting persists, the entire Himalayan glaciers is estimated to disappear by end of 21st century. Here, we assess the influence of the spring 2020 COVID-19 lockdown on the HKH, demonstrati...

The high level of aerosol pollution in South Asia has a measurable impact on clouds, radiation, and precipitation. Here, exploring multiple observational data sets and simulations of the state-of-the-art ECHAM6-HAMMOZ chemistry-climate model, we report that the reduction in anthropogenic emissions during the COVID-19 lockdown period has enhanced pr...

The West North Pacific (WNP) is a breeding ground for tropical cyclones (TC) all through the year with peak activity during August-September, in contrast to the North Indian Ocean where tropical cyclones (TC) are observed mainly during April-June and October-December but suppressed in July-August due to the strong vertical wind shear of the Indian...

Accumulation of water vapor in the upper troposphere/lower stratosphere (UT/LS) over the Asian continent is a recognized feature during the boreal summer monsoon. While there has been a debate on the role of monsoon convective intensities on the UT/LS water vapor accumulations, there are ambiguities with regard to the effects of organized monsoon c...

A monsoon refers to a seasonal transition of regimes in atmospheric circulation and precipitation in response to the annual cycle of solar insolation and the distribution of moist static energy (Wang and Ding, 2008; Wang et al., 2014; Biasutti et al., 2018). A global monsoon can be objectively identified based on precipitation contrasts in the sols...

Aerosol concentrations over Asia play a key role in modulating the Indian summer monsoon (ISM) rainfall. Lockdown measures imposed to prevent the spread of the COVID-19 pandemic led to substantial reductions in observed Asian aerosol loadings. Here, we use bottom-up estimates of anthropogenic emissions based on national mobility data from Google an...

The Indian summer monsoon rainfall (ISMR) is vital for the livelihood of millions of people in the Indian region; droughts caused by monsoon failures often resulted in famines. Large volcanic eruptions have been linked with reductions in ISMR, but the responsible mechanisms remain unclear. Here, using 145-year (1871–2016) records of volcanic erupti...

Earth System Models (ESM) are important tools that allow us to understand and quantify the physical, chemical & biological mechanisms governing the rates of change of elements of the Earth System, comprising of the atmosphere, ocean, land, cryosphere and biosphere (terrestrial and marine) and related components. ESMs are essentially coupled numeric...

Assessments of impacts of climate change and future projections over the Indian region, have so far relied on a single regional climate model (RCM) - eg., the PRECIS RCM of the Hadley Centre, UK. While these assessments have provided inputs to various reports (e.g., INCCA 2010; NATCOMM2 2012), it is important to have an ensemble of climate projecti...

Ozone in the upper troposphere is a dominant radiative constituent. In this study, we investigate ozone variability due to stratospheric intrusions in the upper troposphere over India and associated radiative impacts during monsoon breaks co‐occurring with El Niño using the ECHAM5‐HAMMOZ, Global‐Chemistry‐climate model simulations, and ERA‐Interim...

This chapter discusses observed and projected changes in global climate to set the context, after which it discusses the scientific issues around the complexity of regional climate over the Indian subcontinent, with a focus on the Indian Monsoon. It introduces the Earth System Model from India (IITM-ESM), and synthesises the major findings of the r...

Precipitation is an important component of the global water cycle, and the impacts of anthropogenic climate change on precipitation have significant implications on agricultural activities (Porter et al. 2014).

The atmospheric circulation during the South Asian Summer Monsoon season is analyzed in moist isentropic coordinates. The horizontal mass transport is sorted in terms of its equivalent potential temperature and separated into the upper and tropospheric contributions. This technique makes it possible to trace the transport of air parcels over long d...

In this chapter, we discuss climate variability over the Western Himalaya based on instrumental records as well as information derived from tree-ring data. We focus here on two important climatological elements, namely rainfall and temperature of Western Himalayan region. Trend analyses of rainfall based on 14 stations covering entire western Himal...

Droughts have become more severe and recurrent over the Indian sub-continent during the second half of the twentieth century, leading to more severe hydro-climatic and socio-economic impacts over one of the most densely populated parts of the world. So far, droughts have mostly been connected to circulation changes concomitant with the abnormal war...

Winter-to-early spring non-monsoonal precipitation over the Western Himalayas (WH) primarily comes from eastward propagating synoptic-scale weather systems known as western disturbances (WDs). Earlier studies have noted that an increasing trend of synoptic-scale WD activity in the past few decades has contributed to enhanced propensity of daily pre...

This article provides a brief account of the development of the IITM Earth System Model (IITM-ESM) at the Centre for Climate Change Research, Indian Institute of Tropical Meteorology, in order to address key questions pertaining to the science of Climate Change. The IITM-ESM has been developed by transforming a state-of-the-art seasonal prediction...

Significance Propagating atmospheric vortices contribute more than half of the total rainfall received by the fertile and highly populated Gangetic plains of India. How the activity of these storms will change in a warming climate is not yet understood, due to both the inadequate representation of these disturbances in global climate models and a l...

The potential role of aerosol loading on the Indian summer monsoon rainfall during the El Niño years are examined using satellite-derived observations and a state of the art fully interactive aerosol-chemistry-climate model. The Aerosol Index (AI) from TOMS (1978–2005) and Aerosol Optical Depth (AOD) from MISR spectroradiometer (2000–2010) indicate...

Assessments of impacts of climate change and future projections over the Indian region, have so far relied on a single regional climate model (RCM) - eg., the PRECIS RCM of the Hadley Centre, UK. While these assessments have provided inputs to various reports (e.g., INCCA 2010; NATCOMM2 2012), it is important to have an ensemble of climate projecti...

Rising propensity of precipitation extremes and concomitant decline of summer-monsoon rains are amongst the most distinctive hydroclimatic signals that have emerged over South Asia since 1950s. A clear understanding of the underlying causes driving these monsoon hydroclimatic signals has remained elusive. Using a state-of-the-art global climate mod...

The study diagnoses the relative impacts of the four known tropical Indo-Pacific drivers, namely, El Niño Southern Oscillation (ENSO), ENSO Modoki, Indian Ocean Dipole (IOD), and Indian Ocean Basin-wide mode (IOBM) on African seasonal rainfall variability. The canonical El Niño and El Niño Modoki are in general associated with anomalous reduction (...

Recent studies have drawn attention to a significant weakening trend of the South Asian monsoon circulation and an associated decrease in regional rainfall during the last few decades. While surface temperatures over the region have steadily risen during this period, most of the CMIP (Coupled Model Intercomparison Project) global climate models hav...

Quite a few studies have documented the evolution of monsoon synoptic systems and midlatitude atmospheric blocking associated with the recent heavy precipitation and floods over northwest Pakistan during 2010. This period also witnessed a very unusual Indo-Pacific sea surface temperature (SST) evolution with a strong La Niña event in the Pacific, s...

The suggestion that there exists two types of El Niño in the tropical Pacific has generated a debate in the community. Applying various linear and non-linear approaches on observed and reanalyzed climate datasets primarily for the 1950-2010 period, we revisit the variability of the tropical Pacific in the light of this debate. Our objective is to e...

An intriguing feature associated with ‘breaks’ in the Indian summer monsoon is the occurrence of intense/flood-producing precipitation confined to central-eastern parts of the Himalayan (CEH) foothills and north-eastern parts of India. Past studies have documented various large-scale circulation aspects associated with monsoon-breaks, however the d...

This study examines the feasibility of using a variable resolution global general circulation model (GCM), with telescopic zooming and enhanced resolution (~35 km) over South Asia, to better understand regional aspects of the South Asian monsoon rainfall distribution and the interactions between monsoon circulation and precipitation. For this purpo...

Sea surface temperature (SST) in the region off southern tip of India (STI, 75–83°E, 5–8°N) exhibited a prominent variability in the intraseasonal time scale (both 30–90 d and 10–30 d band) during boreal summer. Mechanisms associated with this intraseasonal variability are studied using three-dimensional ocean general circulation model (OGCM) sensi...

According to current knowledge, convection over the tropical oceans increases with sea surface temperature (SST) from 26 to 29 °C, and at SSTs above 29 °C, it sharply decreases. Our research shows that it is only over the summer warm pool areas of Indian and west Pacific Oceans (monsoon areas) where the zone of maximum SST is away from the equator...

The 2010 summer monsoon was marked by a series of flood events over Pakistan and Northwest India and an intriguing aspect during this season was the strong westward shift of West Pacific Subtropical High (WPSH) by nearly 15° longitude relative to the climatology. This period also witnessed the evolution of an intense La Niña in the Pacific Ocean. L...

The recent series of flood events over Pakistan and Northwest India during the monsoon seasons of 2010 and 2011 are examples of extreme phenomena during the last century that have evoked considerable interest among various scientific communities. One of the causes for the 2010 intense precipitation over Pakistan has been attributed to the interacti...

Understanding the response of the South Asian monsoon (SAM) system to global climate change is an interesting scientific problem that has enormous implications from the societal viewpoint. While the CMIP3 projections of future changes in monsoon precipitation used in the IPCC AR4 show major uncertainties, there is a growing recognition that the rap...

The tropical pacific experienced a hitherto-unseen anomalous basinwide warming from May 2009 through April 2010 with the maximum warming to the east of the dateline, but for a weak anomalous cooling west of 140°E after early boreal fall. Our observed analysis and model experiments isolate the potential teleconnections from TP during the summer of 2...

A typical active–break cycle of the Asian summer monsoon is taken as beginning with maximum SST (pentad 0) over the north Bay of Bengal when the oceans to its west and east from longitude 40°–160°E, and between latitudes 10° and 25°N (area A) also has maximum SST. During this pentad the recently found “Cold Pool” of the Bay of Bengal (between latit...

The marine atmospheric boundary layer (MABL) plays a vital role in the transport of momentum and heat from the surface of the ocean into the atmosphere. A detailed study on the MABL characteristics was carried out using high-resolution surface-wind data as measured by the QuikSCAT (Quick scatterometer) satellite. Spatial variations in the surface w...