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Principal Investigator: V. R. Kotamarthi (Argonne National Laboratory)
Larry Di Girolamo (UIUC) Richard Coulter (Argonne)
Mike Iacono (AER Inc.)
V. Ramaswamy (NOAA-GFDL)
Greg McFarquhar (UIUC)
Sethu Raman (NCSU)
Ralph Kahn (NASA-JPL)
Mavendra Dubey (LLNL)
Doug Worsnop (Aerodyne)
S. K. Satheesh (IISc),
K. Krishnamoorthy (ISRO)
Ram Sagar (ARIES),
S. Tripathi (IIT-K)
Argonne National Laboratory
University of Illinois, Urbana-Champaign (UIUC)
Atmospheric and Environmental Research, Inc. (AER Inc.)
Las Alamos National Laboratory (LANL)
National Aeronautics and Space Administration – (NASA – GSFC)
North Carolina State University (NCSU)
Indian Institute of Technology, Kanpur, India (IIT-K)
Indian Space Research Organization, Trivandrum, India (ISRO)
Indian Institute of Science, Bangalore, India (IISc)
Date Submitted: May 15, 2008
Location of Proposed Activities: Nagpur (primary site); Kanpur, Nainital, Bangalore (auxiliary sites)
Proposed Period of Deployment: April 2010–January 2011 (Shold be extended until April 2011. In page 9, you mention to the end of Spring which is April)
The Indian subcontinent is one of the largest and most rapidly developing sections of the world today. The Ganges River valley in particular is undergoing rapid industrialization, large scale landuse changes and pressures from rapidly increasing population on the environment and natural resources. The Ganges River provides the region with water needed for sustaining life, is fed primarily by snow and rainfall associated with Indian summer monsoon (ISM). Human impacts resulting from changes in precipitation patterns, temperature, and the flow of the snow-fed rivers could be immense. The impacts of climate change on snowfall in the mountains and on monsoons have been modeled extensively. The expected range of behavior varies from no change in annual precipitation to an increase. Many of the studies evaluated the impact of doubling CO2 and thus focused on changes resulting from tele-connection of the ISM with the Atlantic, the Pacific, and snow-covered Eurasia. Changes in the ISM over population centers in the subcontinent itself have rarely been evaluated. Increasing aerosol, air pollution, and deforestation, resulting in changes in surface albedo and insolation, could potentially lead to low monsoon rainfall. In recent years, satellite-based measurements have indicated that the upper Ganges valley has some of the highest persistently observed aerosol optical depths. The aerosol layer covers a vast region, extending across the Indo-Gangetic Plain to the Bay of Bengal during the winter and early spring of each year. Aerosols from this region were shown during the INDOEX field studies to affect cloud formation and monsoon activity over the Indian Ocean. This is one of the few regions showing a trend towards increasing surface dimming. The consequences of these aerosols and associated pollution for surface insolation over the Ganges valley and monsoons in particular are not well understood. Increasing air pollution over this region could modify the radiative balance through direct, indirect, and semi-indirect effects associated with aerosols.
The AMF deployment proposed here is designed to measure relevant radiative and aerosol optical characteristics in this region and provide a baseline measurement. The purpose will be collect a data set that in conjunction with other planned and ongoing efforts in this region will address the potential consequences of increasing regional-scale atmospheric pollution on the ISM and consequently on the hydrology of this sensitive climate zone. The AMF deployment will coincide with a field study initiated by India starting in 2008 and extending 2011. This field study titled ‘Continental Tropical Convergence zone’ will involve aircrafts, ships and nearly 30 ground stations of varying capabilities deployed for this 3-year time period. A NASA field effort named TIGERZ for validating AERONET and CALIPSO retrievals is also scheduled for this time period. The AMF deployment starting approximately at the end of spring 2010 and lasting to the end of winter 2011 makes the AMF deployment part of large data collection effort. With a ten-month deployment we will have an opportunity to measure different regimes of the monsoon climate: the wet monsoon period the dry, hot summer; and the dry winter. Each regime has its own distinct radiative and atmospheric dynamic drivers. The high concentration of aerosols in the upper Ganges valley, together with hypotheses involving several possible mechanisms with direct impacts to the hydrologic cycle of the region, gives us a unique opportunity to generate data sets that would be useful both in understanding the processes at work and in providing a data set that could be used for evaluating these processes in climate and radiative transfer models. All of the measurements from this study will be used to generate a merged data set for model evaluations and process-scale model development. Several models, including RRTM, the NCAR CCSM and GFDL global-scale models, and regional scale climate models, will be evaluated with the measurements. The measurements, in particular, will also assist with several closure studies for shortwave radiation models, including RRTMG.
2.0 Project Description
The Ganges valley region is one of the largest and most rapidly developing sections of the Indian subcontinent. Bounded by the Indian Ocean to the east, the Thar Desert to the west, the Himalayas to the north, and the central plains of India to the south, the region covers approximately 2.25 million km2 (Coleman and Huh, 2004). This region is home to about 700 million people and accounts for about 20% of the Indian gross domestic product. It houses heavy industry such as steel, cement, and power plants and is one of the ancient continuously farmed regions of the world. The crops grown here provide much of the food for the rest of India. The Ganges River, which provides the region with water needed for sustaining life, is fed primarily by snow and rainfall associated with Indian summer monsoon (ISM). The upper Ganges valley has some of the largest glaciers in the Himalayas, and aerosol/black carbon deposition on the glaciers and snow cover could have long-term effects on regional hydrology. Human impacts due to changes in precipitation patterns, temperature, and the flow of the snow-fed rivers could be immense. The persistent winter fog in the region is already a cause of much concern, and several studies have been proposed to understand the economic, scientific, and societal dimensions of this problem. Recent studies have also linked increased aerosol loading and ozone to the decline in vegetation along the foothills of the Himalayas.
The impacts of climate change on snowfall in the mountains and on monsoons have been modeled extensively (Houghton et al., 2001). The expected range of behavior varies from no change in annual precipitation to an increase. However, recent studies have suggested that average rainfall could be constant, while the intensity of the rainfall events increases (Goswami et al., 2006). The short-term forecasting capability of different models for Indian monsoons is still in question (Gadgil and Sani, 1998). Short-term parametric forecasting models of ISM have a long history, with parameters ranging from El Niño-Southern Oscillation (ENSO) (Shukla and Paolina, 1983) to sun spot activity (Bhattacharyya and Narishma, 2005). The current generations of full 3-D climate models however are unsuccessful in simulating the intra-seasonal variability of the ISM. Analyses of the intra-seasonal variability in the model demonstrated that the convection schemes generate intra-seasonal variability of much lower amplitude than the observed variance (Meehl et al., 2006, Gadgil and Sani 1998). A number of climate model simulations primarily evaluate the impact of changing sea surface temperatures, which have been shown to correlate strongly with monsoon rainfall over the Indian subcontinent (Webster et al., 2002) and with ENSO (Kumar et al., 2006). Many of these studies evaluate the impact of doubling CO2 and thus focus on changes resulting from tele-connection of the ISM with the Atlantic, the Pacific, and snow-covered Eurasia.
Changes over population centers in the subcontinent itself have rarely been evaluated. Increasing aerosol, air pollution, and deforestation resulting in changes in surface albedo and insolation were shown, through use of a simple box model, to potentially lead to low monsoon rainfall (Zickfeld et al., 2005). The upper Ganges valley has some of the highest persistently observed aerosol optical depths (AODs) in the MISR global data set (Di Girolamo et al., 2004; Figure 1). The aerosol layer covers a vast region, extending across the Indo-Gangetic Plain to the Bay of Bengal during the winter and early spring of each year. The AOD shows variability within the region and is highest in the sub Himalayan regions of eastern India. The aerosols are composed mostly of anthropogenic pollution particles and are high in sulfate, nitrate, organic, and black carbon contents (Singh et al., 2004; Tripathi et al., 2005; Dey and Tripathi, 2007). The aerosols may also include mineral dust from the Thar Desert (Chinnam et al., 2006). Aerosols from this region were shown to affect cloud formation and monsoon activity over the Indian Ocean during the INDOEX field studies (Ramanathan et al., 2002; Ramanathan et al., 2005).
The consequences of these aerosols and associated pollution for surface insolation over the Ganges valley and monsoons in particular are not well understood. Doubling of the concentration of the major greenhouse gas CO2 is expected to result in increasing temperatures
Figure 1: Multi-angle Imaging SpectroRadiometer (MISR) aerosol optical depths at mid-visible wavelengths (558 nm), averaged over December-February of years 2001, 2002, 2003, and 2004 (from Di Girolamo et al., 2004).
over the land of the subcontinent and into the mid-troposphere (Kothwale and Rupa Kumar, 2002). This effect could be expected to intensify the summer pressure gradient differential between the land and ocean and thus strengthen the ISM (Hu et al., 2000). Several recent studies that include aerosols and GHGs have shown there is an equally likely possibility that precipitation could be much lower than the range observed during the Halocene due to changes in orbital parameters (Mitchell and Johns 1997). These changes can be abrupt resulting from a bifurcation in the response of precipitation to planetary albedo changes (Zickfield et al. 2004, Knopf et al. 2006). A recent study has shown that the measured surface insolation over India has decreased by 4% between 1980 and 2000 (Padma-Kumari et al. 2007; Pinker et al. 2005). Over the Indian Ocean, it has also been shown recently that the lower atmospheric solar heating is increased by about 50% due to the brown cloud (Ramnathan et al., 2007). This is expected to make the atmosphere more stable over the ocean and thus reduce convective mixing. Increasing air pollution over India could alter this outcome by modifying the assumed radiative balance through (1) increased back-scattering from anthropogenic aerosols such as sulfates and nitrates; (2) localized heating of the cloud air mass due to increasing concentrations of black carbon, thus leading to droplet evaporation; (3) changes in the size of cloud droplets due to increasing aerosols in the atmospheric column; and (4) altered precipitation due to changes in aerosol sizes.
The proposed field study is designed to measure relevant radiative, cloud, convection and aerosol optical characteristics on mainland India over an extended period of time to develop a comprehensive data set extending from pre monsoon to post monsoon that could be used to constrain convection, cloud properties and aerosols. This data set would provide a baseline and lead to a better evaluation of the potential consequences of increasing regional-scale atmospheric pollution on the ISM and consequently on the hydrology of this sensitive climate zone.
An AERONET site has been operational in Kanpur (26.28 N, 80.24 E) for the past six years. Initial analysis of the data has already yielded a number of interesting results. The measured AOD at this site shows large variability, with high values during much of the year and lower values during spring. The Angstrom coefficient has small values during the summer months and higher values during the winter and early spring (Figure 2). The low Angstrom values during the summer are indicative of larger particles (most likely desert dust), while the higher values during winter and early spring indicate an abundance of smaller particles, potentially of anthropogenic origin.
Figure 2: AERONET data from Kanpur, year 2005.
This region is also undergoing rapid industrialization. Coal remains the primary energy source for heavy industry. The region is dotted with large coal-based power generation facilities, cement factories, and steel mills, all using extensive amounts of coal (Figure 3). The long-range viability of the aerosol plume and hence its regional and global impacts are very dependent on the vertical structure of the aerosol cloud. Climatologically, a high-pressure ridge over the wintertime Indo-Gangetic Plain confines the pollution to the planetary boundary layer (PBL), creating the high concentrations. The synoptic regional wind is dominated by westerly flow (Figure 4). This flow pattern has been used to suggest that most of the dust observed in this region has its origin in the western Thar Desert of India and, beyond India’s national boundaries, in the Middle East. The flow pattern in the PBL is northwesterly over this region and is marked by light winds. The primary sources of the aerosols are thought to be emissions from some large coal-fired power plants (Figure 3), local and long-range-transported dust, and biofuels and biomass burning.
The period during late December and early January marks the traditional planting of the second crop for the year in much of this area. This period is also associated with burning of agricultural waste from the previous harvest, which is a significant additional source of aerosols to the regional aerosol mix (Singh, 2006). The northwesterly winds at the 850 mb level indicate a potential for long-range transport of biomass burning plumes into the region of observed high aerosols (Figure 4). Measuring aerosols during the entire annual cycle would be ideal for characterizing the anthropogenic component of the observed aerosols in the Ganges valley and evaluating their impacts on regional and global scales.
The effect of aged aerosols, potentially from this source region, on the hydrologic cycle was explored in the context of monsoons over the Indian Ocean during the INDOEX field study in 1998. The current analysis indicates contradictory effects of aerosols and greenhouse gases on monsoon-related rainfall over India (Chung and Ramanathan, 2006). Aerosols alone have been shown to decrease temperature over portions of the Indian Ocean and thus reduce monsoon activity and related rainfall. However, increasing temperatures due to greenhouse gases might increase the land-ocean temperature contrasts and hence strengthen the monsoon circulation and precipitation. A recent analysis of monsoon rainfall patterns showed a trend of increasingly extreme rainfall events over the Indian subcontinent (Goswami et al., 2006).
igure 3: Coal consumption in India. The predominance of red circles in the Ganges valley is evident.
igure 4: Mean wind field at 850 mb (left) and 300 mb (right) from the NCEP data set, averaged for the years 1980 to 2006.
Lau et al. (2006) recently proposed that an “elevated heat pump” effect could result from heating of the atmosphere due to dust transported from the Indian western desert (Thar) that accumulates over the upper Gangetic Plain, with subsequent mixing of the aerosols with anthropogenically generated soot, sulfate, nitrate, and black carbon. This “elevated heat pump,” the authors suggest, could provide a diabatic heating source that leads to additional heating in the upper and middle atmosphere, as well as strengthening of the monsoon and additional rainfall. The near-source impacts on the cloud generation and hydrologic cycles are relatively unknown, though high concentrations of fine aerosols were recently shown to decrease precipitation in hilly areas during the Chinese monsoon (Rosenfeld et al., 2007). Both extinction optical depth and absorbing-to-scattering ratio have now been shown to be determinants of changes in precipitation (Randal and Ramaswamy, 2007).
The Indian Space Research Organization (ISRO) has undertaken a well-focused activity with long-term objectives for characterizing the aerosol properties over Indian regions with a long-term, dedicated instrumented network, under its Geosphere Biosphere Programme (GBP). The network currently has about 12 stations making regular measurements of spectral AOD by using ISRO’s instruments (the microwave radiometer or MWR), surface aerosol concentrations and size distributions, and black carbon aerosols. In addition, several lidars operating from distinct locations provide information on the altitude profiles of aerosols. Figure 5 shows the spatial coverage of network stations under ISRO-GBP, with the red circles indicating places where ISRO-GBP has operational stations at present or will be installing them shortly. In the Ganga basin, observations are currently available at Kanpur, Dehradun, and Kharagpur, while stations will be coming up in Jodhpur, Nagpur, and Varanasi by 2008. The network also aims at generation of climatology for India incorporating all the heterogeneities, spatial and temporal, over the mainland and islands. Over the oceanic region, efforts to characterize aerosols over Arabian Sea and Bay of Bengal (Nair et al., 2006) have been based extensively on satellite data (NOAA AVHRR). ISRO-GBP has also conducted focused, thematic campaigns over the mainland (called LC-1 and LC-2 for land campaigns 1 and 2), with special emphasis over the Indo-Gangetic Plain in December 2004 (e.g., Moorthy et al., 2005; Pant et al., 2006; Nair et al., 2006). In 2006, the three-month-long ICARB campaign, involving network stations, ships, and aircraft, was carried out under ISRO-GBP (Moorthy et al., 2005).
A new field study is set for the time period extending from 2008 to 2011 to evaluate the function of Inter tropical convergence zone on the ISM. The CTCZ project is sponsored by the Indian Climate Research Program (ICRP). The large-scale rainfall over the Indian region during the summer monsoon is associated with a tropical convergence zone (TCZ), characterized by intense convergence in the boundary layer, cyclonic vorticity above the boundary layer and deep moist convection. This TCZ is called the continental TCZ (CTCZ) to distinguish it from the more common TCZ seen over the tropical oceans. The main objective of CTCZ is to understand the mechanisms leading to space-time variation of the CTCZ during the summer monsoon. We expect the precipitation processes to be strongly influenced by the CCN characteristics, which in the eastern end of CTCZ is marine in nature whereas dominated by the land aerosols (dust & BC) towards the western end. The logic behind the planned measurements relies on the fact that establishment of measurement-based CCN-cloud relationships would lead to better understanding of monsoon clouds which in turn lead to better understanding of monsoon rainfall. The back trajectories (24-hr ) over the IG basin (Fig. 4) showing varying modulations to the aerosol characteristics with continental, desert and marine aerosols over different parts of the IGP, leading to regional differences in radiative impacts. From ISRO, CTCZ project is supported (with 29 surface observatories and aircraft measurements) by ISRO-GBP program.
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