Pune, India

The Indian Institute of Tropical Meteorology or IITM is a scientific institution based in India for expanding research in meteorology of the tropics in general with special reference to monsoon meteorology of India. The current in charge director of IITM is Dr. R. Krishnan Wikipedia.

Time filter

Source Type

News Article | January 19, 2016
Site: news.yahoo.com

A fisherman paddles his boat in the Indian Ocean next to Jazeera beach near Somalia's capital Mogadishu, October 2, 2015. REUTERS/Feisal Omar/Files More NEGOMBO, Sri Lanka (Thomson Reuters Foundation) - Anslem Silva has fished for four decades from this popular harbor on Sri Lanka's west coast, but for five years now filling his boat has become increasingly difficult. "We seem to be spending more and more time out at sea looking for catch. Where there were fish for decades, now there is very little. It is strange, but all of us have been noticing that," said the 54-year-old fisherman, who operates his own trawler on multi-day trips reaching 100 to 150 kilometres (60 to 90 miles) off the coast. Overfishing is responsible for some of the lowered catch, but another problem may also be contributing: lack of food for the fish themselves, driven by global warming. "Rapid warming in the Indian Ocean is playing an important role in reducing phytoplankton up to 20 percent," said Roxy Mathew Koll, a scientist at the Centre for Climate Change Research at the Indian Institute of Tropical Meteorology in Pune. Over six decades, rising water temperatures appear to have been reducing the amount of phytoplankton – microscopic plants at the base of the ocean food chain – available as food for fish, according to research released in December by Koll and other scientists from the United States, South Africa and France. That “may cascade through the food chain, potentially turning this biologically productive region into an ecological desert,” Koll said. Such a change would curb food security not only in Indian Ocean rim countries but also global fish markets that buy from the region, he said. As waters in parts of the Indian Ocean have warmed by 1.2 degrees Celsius over the last century, the mixing of surface water and nutrient-rich deeper waters have slowed, the scientists said. That has prevented nutrients from reaching the plankton, which are mostly active in surface waters. “The vertical mixing (of water) is a critical process for introducing nutrients into the upper zones where sufficient light is available for photosynthesis,” said Raghu Murtugudde, a scientist from the University of Maryland. The researcher said that recent data showed phytoplankton levels falling dramatically in some regions that are traditionally home to large shoals of fish, such as near the Kenyan and Somali coasts. “Recent satellite data show that the decline is up to 30 percent in the western Indian Ocean during the last 16 years, which is one of the most biological productive regions in the tropics and host to some of the most economically viable tuna species,” said Marcello Vichi, another of the study’s coauthors, from the University of Cape Town. The western Indian Ocean is responsible for 20 percent of the global tuna catch, the research said. While tuna overfishing was a contributing factor to lower stocks of the fish, declines in food sources – such as phytoplankton – were also a significant problem, it said. Koll predicted fish stocks could decline significantly further in the face of continued overfishing and ocean warming. “All of the state-of-the-art climate models unanimously project that the Indian Ocean will continue to warm under increasing greenhouse gases. This will result in a further decline of the phytoplankton in the Indian Ocean, exaggerating the stress on the marine ecosystem and the fish, which are already affected by overfishing,” he said. The impact will be felt in countries around the Indian Ocean, including India, Sri Lanka and Bangladesh. But importers such as the United States, Europe and Japan also could feel the impact, the scientists said. Fishermen in Sri Lanka say they already see the number of fishing boats in some of the country’s ports declining as a result of the changes. “It is very difficult to operate a new boat … so few people now want to get into fishing at a large scale,” said Mohamed Riyazudeen, who works as a boat captain from Valechchennei, an important fishing port on Sri Lanka’s east coast. He called the research on ocean warming very bad news. “What are we to do? We don't know any other trade and if there is no fish, what are we to catch?” he asked.

Beig G.,Indian Institute of Tropical Meteorology
Journal of Geophysical Research: Space Physics | Year: 2011

A detailed overview of long-term secular trends in temperature of the mesosphere and lower thermosphere considered to be induced by increase in greenhouse gases has been provided by Beig et al. (2003). Since then, quite a few new results have been emerged as some of the data series have become sufficiently large enough to provide results with improved confidence. Our understanding on the nature of temperature trends in the mesosphere/lower thermosphere (MLT) region is relatively better now. In the mesosphere, some of the results confirmed the earlier findings, and some new results obtained by satellite and lidar data over the tropical region have indicated a relatively weaker cooling trend as compared to the past but nevertheless strengthened the conclusion about the cooling trends. However, in the mesopause region, some of the new results now indicate a break in trend and tendency of negative signal where earlier no trend feature was noticed. This slice of no trend feature in between two cooling regimes was puzzling the modeling community, who were in search of a convincing explanation. This paper briefly outlines the progress made over the recent past in the field of MLT region secular temperature trends attributed mainly to growth of greenhouse gases near the Earth's surface. Copyright 2011 by the American Geophysical Union.

Beig G.,Indian Institute of Tropical Meteorology
Journal of Geophysical Research: Space Physics | Year: 2011

Understanding trends in any atmospheric quantity typically requires the ability to distinguish between naturally occurring processes that result in trends, such as the 11 year solar cycle, and potential anthropogenic secular trends that occur simultaneously. After the review of mesospheric and lower thermospheric temperature response to solar activity by Beig et al. (2008), a few new results along with some modified results by revisiting the older data sets have been reported recently. Main improvement is due to the length of data series and amount of data which have been accounted in recent years. This article summarizes the progress made in the field of temperature variability due to changing solar activity as reported recently. Recent investigations revealed that the solar signal becomes stronger with increasing latitude in the mesosphere. Temperature response to solar activity at the lower part of mesopause region is around a few degrees per 100 solar flux units (sfu), which becomes stronger (4-5 K/100 sfu) in the upper part of this region in both hemispheres. The overall global picture indicates that the solar signal in the mesopause region temperature in the Northern Hemisphere is relatively stronger in recent time in a majority of locations compared to results reported in earlier reviews. Copyright 2011 by the American Geophysical Union.

Yadav R.K.,Indian Institute of Tropical Meteorology
Climate Dynamics | Year: 2013

This study examines the emerging role of Indian Ocean sea surface temperature (SST) on the inter-annual variability (IAV) of Indian north-east monsoon rainfall (NEMR). The IAV of NEMR is associated with the warm SST anomaly over east Bay-of-Bengal (BoB) (88.5oE-98.5oE; 8.5oN-15.5oN) and cool SST anomaly over east equatorial Indian Ocean (80.5oE-103.5oE; 6.5oS-3.5oN). The gradient of SST between these boxes (i.e. northern box minus southern box) shows strong and robust association with the Indian NEMR variability in the recent decades. For establishing the teleconnections, SST, mean sea level pressure, North Indian Ocean tropical storm track, and circulation data have been used. The study reveals that during the positive SST gradient years, the inter-tropical convergence zone (ITCZ) shifts northwards over the East Indian Ocean. The tropical depressions, storms and cyclones formed in the North Indian Ocean moves more zonally and strike the southern peninsular India and hence excess NEMR. While, during the negative SST gradient years, the ITCZ shifts southwards over the Indian Ocean. The tropical depressions, storms and cyclones formed in the North Indian Ocean moves more northwestward direction and after crossing 15oN latitude re-curve to north-east direction towards head BoB and misses southern peninsular India and hence, deficient NEMR. © 2012 Springer-Verlag Berlin Heidelberg.

Yadav R.K.,Indian Institute of Tropical Meteorology
International Journal of Climatology | Year: 2012

This study examines decadal changes of the El Niño/Southern Oscillation (ENSO) influence on the interannual variability (IAV) of Indian northeast monsoon rainfall (NEMR). In recent decades, the ENSO influence has strengthened over the NEMR variability. During El Niño years, the subsidence anomaly over the warm-pool region of Indonesia was much stronger in the recent decades as compared to the earlier decades. The zonally elongated warm sea surface temperatures (SSTs) of the warm-pool region along the tropical Indo-Pacific Ocean were much warmer than the earlier decades, which had intensified the deep convections over the Indian Ocean. The northwestward propagating trailing Rossby-gyres, formed in the western portion of the equatorial deep convection and stratiform heating, intensified as tropical storms and cyclones over north Indian Ocean. These storms and cyclones strike southern peninsular India and hence flood northeast monsoon (NEM) years. During the recent decades in the La Niña years, the contracted warm SSTs over the warm-pool region were much warmer than the earlier decades which intensified the deep convection and stratiform heating over there. The tropical storms and cyclones that formed due to Rossby-gyre dynamics had to travel a long distance towards the northwestward direction over the Bay of Bengal and misses southern peninsular India, and hence, the drought NEM years. © 2011 Royal Meteorological Society.

Tree growth-climate relationship analysis revealed the important role of soil moisture availability in development of annual growth rings. Winter season (October-March) Palmer Drought Severity Index (PDSI) is an important factor in developing annual tree-rings during subsequent growing seasons. The chronology was strongly correlated with winter PDSI in recent few decades, more so than in the earlier period, indicating that tree growth is more dependent on climate. Many low growth years detected during El Nino events are probably related to moisture deficiency. The result indicates that the tree growth is mostly affected by the soil moisture availability during the recent warm periods over the region. © 2011 Elsevier Ltd and INQUA.

Tree-ring chronologies of fir (Abies pindrow) and spruce (Picea smithiana) show highly significant positive correlation with Palmer Drought Severity Index (PDSI) as compared to rainfall over the region. This study indicates that soil moisture availability during summer season (April-September) plays a vital role in developing the annual ring-width pattern. Higher mean, maximum, and minimum temperatures during the summer season are not found to be conducive for the growth of the trees. The summer seasons' PDSI of the region has been reconstructed from AD 1820-1981. © 2011 Elsevier Ltd and INQUA.

Debaje S.B.,Indian Institute of Tropical Meteorology
Environmental Science and Pollution Research | Year: 2014

In this study, we estimate yield losses and economic damage of two major crops (winter wheat and rabi rice) due to surface ozone (O3) exposure using hourly O3 concentrations for the period 2002-2007 in India. This study estimates crop yield losses according to two indices of O3 exposure: 7-h seasonal daytime (0900-1600 hours) mean measured O3 concentration (M7) and AOT40 (accumulation exposure of O3 concentration over a threshold of 40 parts per billion by volume during daylight hours (0700-1800 hours), established by field studies. Our results indicate that relative yield loss from 5 to 11 % (6-30 %) for winter wheat and 3-6 % (9-16 %) for rabi rice using M7 (AOT40) index of the mean total winter wheat 81 million metric tons (Mt) and rabi rice 12 Mt production per year for the period 2002-2007. The estimated mean crop production loss (CPL) for winter wheat are from 9 to 29 Mt, account for economic cost loss was from 1,222 to 4,091 million US$ annually. Similarly, the mean CPL for rabi rice are from 0.64 to 2.1 Mt, worth 86-276 million US$. Our calculated winter wheat and rabi rice losses agree well with previous results, providing the further evidence that large crop yield losses occurring in India due to current O3 concentration and further elevated O3 concentration in future may pose threat to food security. © 2014 The Author(s).

Roxy M.,Indian Institute of Tropical Meteorology
Climate Dynamics | Year: 2014

Over the tropical oceans, higher sea surface temperatures (SST, above 26 °C) in summer are generally accompanied by increased precipitation. However, it has been argued for the last three decades that, any monotonic increase in precipitation with respect to SST is limited to an upper threshold of 28-29.5 °C, and beyond this, the relationship fails. Based on this assessment it has often been presumed that, since the mean SSTs over the Asian monsoon basins (Indian Ocean and north-west Pacific) are mostly above the threshold, SST does not play an active role on the summer monsoon variability. It also implies that increasing SSTs due to a changing climate need not result in increasing monsoon precipitation. The current study shows that the response of precipitation to SST has a time lag, that too with a spatial variability over the monsoon basins. Taking this lag into account, the results here show that enhanced convection occurs even up to the SST maxima of 31 °C averaged over these basins, challenging any claim of an upper threshold for the SST-convection variability. The study provides us with a novel method to quantify the SST-precipitation relationship. The rate of increase is similar across the basins, with precipitation increasing at ~2 mm day-1 for an increase of 1 °C in SST. This means that even the high SSTs over the monsoon basins do play an active role on the monsoon variability, challenging previous assumptions. Since the response of precipitation to SST variability is visible in a few days, it would also imply that including realistic ocean-atmosphere coupling is crucial even for short term monsoon weather forecasts. Though recent studies suggest a weakening of the monsoon circulation over the last few decades, results here suggest an increased precipitation over the tropical monsoon regions, in a global warming environment with increased SSTs. Thus the signature of SST is found to be significant for the Asian summer monsoon, in a quantifiable manner, seamlessly through all the timescales-from short-term intraseasonal to long-term climate scales. © 2013 Springer-Verlag Berlin Heidelberg.

News Article | January 21, 2016
Site: www.techtimes.com

The Indian Ocean is an ecological desert in the works, warned scientists who sounded the alarm not just on overfishing but also on the pernicious effects of global warming. Overfishing is not the sole cause for the lowered catch in the region – food sources for fish are increasingly becoming scarce because of global warming. Warming in the Indian Ocean has been decreasing phytoplankton by up to 20 percent, revealed Roxy Mathew Koll, a scientist working at the Indian Institute of Tropical Meteorology. Along with other scientists, Koll put out related research in December. Rising water temperatures appear to have been decreasing the number of phytoplankton – microscopic plants located at the base of the marine food chain serve as food for fish – for more than six decades now. This scarcity of phytoplankton is feared to affect the whole food chain and likely turn the Indian Ocean into an “ecological desert,” according to Koll. This situation will hound food security not just in the region but also international fish markets that get their supply from such countries. Fifty-four-year-old Anslem Silva, for instance, has been fishing for 40 years from a harbor on the west coast of Sri Lanka. However, for about five years now, it has been tough for him to fill his boat. “Where there were fish for decades, now there is very little. It is strange, but all of us have been noticing that.” Waters in sections of the Indian Ocean have warmed over the past century by 1.2 degrees Celsius or 34.16 degrees Fahrenheit, leading to a slower integration of surface water and nutrient-dense deeper waters. This has barred nutrients from getting to plankton, which mostly find themselves in surface waters. This vertical mixing, according to scientist Raghu Murtugudde of the University of Maryland, is a critical procedure to bring nutrients into upper zones that harbor sufficient light for photosynthesis. According to data, phytoplankton amounts are also declining in regions that typically shelter large schools of fish, including areas near the coasts of Kenya and Somali. There is already up to 30 percent decline in the western part of the Indian Ocean, which is among the most biologically sound regions and home to 20 percent of the tuna catch worldwide. The researchers are not so optimistic as fish stocks will likely decline even further in the face of overfishing and warming of the oceans, bending under the pressure of increased greenhouse gases. Countries such as India, Sri Lanka, Bangladesh, and import partners United States and Europe could experience the negative blow.

Loading Indian Institute of Tropical Meteorology collaborators
Loading Indian Institute of Tropical Meteorology collaborators