Decrease in evaporation over the Indian monsoon region: Implication on regional hydrological cycle

Using surface observations from 58 widely distributed stations over India, a highly significant (99.9 ) decreasing trend of pan evaporation (Epan) of 9.24 mm/a/a is calculated for 1971 to 2010. This constitutes a ~10 reduction of Epan over the last four decades. While Epan is decreasing during the wet summer monsoon season (JJAS), as well as during the dry rest of the year, the rate of decrease during the dry season is much larger than that during the wet season. Apart from increasing solar dimming, surface winds are also persistently decreasing over the Indian sub-continent at the rate of -0.02 m/s/a resulting in ~40 reduction over the last four decades. Based on PenPan model, it is shown that both the above factors contribute significantly to the decreasing trend in Epan. On a continental scale, annual mean potential evaporation (Ep) is larger than rainfall (P or Ep-P > 0, moisture divergence) indicating that India is water-limited. However, during wet monsoon P > Ep (or Ep-P < 0, moisture convergence) indicating that India is energy-limited during this season. Long term data shows that annually Ep-P follows a significant decreasing trend indicating that water limitation is decreasing with time. This is largely due to stronger decreasing trend of Ep-P during the dry season compared to weaker increasing trend of Ep-P during the wet monsoon season. The scatter plot of Ep-P versus Ep also conveys that the decrease in Ep leads to increase in moisture convergence in wet season and decrease in moisture divergence in dry season

Cloud fraction retrieval and its variability during daytime from ground-based sky imagery over a tropical station in India

Total Sky Imager (TSI) is operated at a high altitude station in the Western Ghats of the Indian sub-continent from June 2012 to June 2013. The TSI image content is classified as clear, thin and thick clouds using red blue ratio (RBR) threshold technique and then cloud fraction (CF) is retrieved. An algorithm is proposed to improve the accuracy of CF retrieval, by adapting the methodologies used in earlier studies and new developments are suggested in sections of the validation of clear sky image and the aerosol correction factor. Time series of thin, thick and total CF are constructed for each day at 5 min interval. These measurements at high temporal resolution are first of their kind over a tropical station in India. Both thick and thin CFs showed high temporal variability. The transition from one season to another season also showed distinct CF variability. Monthly mean CF showed a mono model distribution in the winter months (December and January) and a bimodal distribution in the pre-monsoon months (March, April, May) including February. During the monsoon season (JJAS) about 90% CF is observed throughout the day. The post-monsoon months (October, November) show a bimodal distribution with one peak in the morning hours and another peak in the afternoon hours. Unlike thin CF, total and thick CFs showed almost similar variability. The comparison of CF retrieved from MODIS (Terra and Aqua) and TSI showed a good correlation for overcast sky conditions, while partial cloudy skies showed less correlation due to the effect of satellite viewing angles. Such continuous measurements of CF at high temporal resolution are essential for cloud radiative forcing studies

Aerosol indirect effects from ground-based retrievals over the rain shadow region in Indian subcontinent

Aerosol-induced changes in cloud microphysical and radiative properties have been studied for the first time using ground-based and airborne observations over a semiarid rain shadow region. The study was conducted for nonprecipitating, ice-free clouds during monsoon (July to September) and postmonsoon (October) months, when cloud condensation nuclei (CCN) concentrations over the region of interest increased monotonically and exhibited characteristics of continental origin. A multifilter rotating shadowband radiometer and microwave radiometric profiler were used to retrieve the cloud optical depth and liquid water path (LWP), respectively, from which cloud effective radius (CER) was obtained. CER showed wide variability from 10–18 µm and a decreasing trend toward the postmonsoon period. During monsoon, the estimated first aerosol indirect effect (AIE) increased from 0.01 to 0.23 with increase in LWP. AIE at different super saturations (SS) showed maximum value (significant at 95%) at 0.4% SS and higher LWP bin (250–300 g/m2). Also, statistically significant AIE values were found at 0.6% and 0.8% SSs but at lower LWP bin (200–250 g/m2). The relationship between CCN and CER showed high correlation at 0.4% SS at higher LWP bin, while at higher SSs good correlations were observed at lower LWPs. Data combined from ground-based and aircraft observations showed dominance of microphysical effect at aerosol concentrations up to 1500 cm−3 and radiative effect at higher concentrations. This combined cloud microphysical and aerosol radiative effect is more prominent during postmonsoon period due to an increase in aerosol concentration

Comparative study of aircraft- and satellite-derived aerosol and cloud microphysical parameters during CAIPEEX-2009 over the indian region

This article presents the spatial and vertical distribution of aerosols and cloud microphysical parameters from the combined data sets of aircraft and satellites. The aircraft-based Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX) was conducted in India during May to September 2009. During the experimental period, 3 days were identified on which space-borne lidar (CALIPSO) and radar (CloudSat) were nearby/over passed the observational regions, which covered north, south central, and southern parts of the Indian subcontinent. The results obtained from these three cases are explored. Similar features of aerosol layering and water/ice cloud signatures are observed by both aircraft and CALIPSO. In addition, events where dust aerosols acting as ice nuclei and polluted aerosols increase the depth of warm rain initiation are observed. The CloudSat profiles of liquid water content, droplet number concentration, and effective radii are underestimated when compared with the corresponding aircraft profiles. The aircraft measurements are able to bring out fine variability in vertical distribution, which would be more useful for regional parameterization schemes and model evaluatio

In situ measurements of aerosol vertical and spatial distributions over continental India during the major drought year 2009

The variability in aerosol vertical and spatial distribution over the continental Indian region is studied using the airborne observations during the Cloud Aerosol Interactions and Precipitation Enhancement EXperiment (CAIPEEX) from May to September, 2009. The fine mode (0.1-3.0μm) aerosol vertical profiles up to 6km at different regions showed different vertical structures mostly influenced by the atmospheric boundary layer (ABL) depth as well as the origin of air mass trajectories and the presence of clouds. Elevated aerosol layers are observed during pre-monsoon and during monsoon at some locations but comparatively lower than the one observed in the boundary layer. During monsoon, aerosol number concentration showed strong vertical gradient and a transition is observed between the boundary layer and the free troposphere. The coarse mode (>3μm) aerosol vertical profiles also showed elevated layers at higher altitudes due to the incursion of dry air laddened with dust. The spatial distribution shows significant variation at the elevated layers as compared to that in the boundary layer during pre-monsoon, while high variability is observed in the boundary layer during monsoon. The frequency distribution of different aerosol types from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) showed dominating contributions from dust, polluted dust and smoke during pre-monsoon. During monsoon also traces of these pollutants were found to be high as the year 2009 is a drought year with rainfall deficiency of 22. The surface level number concentration and the height of ABL are found to influence the aerosol optical depths significantly

Possible evidence of new particle formation and its impact on cloud microphysics from airborne measurements over Bay of Bengal

Airborne measurements conducted under a special mission over Bay of Bengal (BoB) during the CAIPEEX (Cloud Aerosol Interaction and Precipitation Enhancement EXperiment) in 2011 were analyzed in the present study. Research flights were carried out on 19 and 20 October, 2011 (referred as RF1 and RF2), in the region over BoB, which was influenced by a depression to evaluate the aerosol–cloud interactions over marine environment. The increased concentration of aitken/accumulation mode particles was observed at 500 m above sea surface level over the ocean after the passage of the depression. The source of these particles and their subsequent growth during RF1 at about 200 km from coastline has been attributed to (i) increased production of aerosols due to oxidation of dimethyl sulfide (DMS) because of upwelling of the deep ocean water during the depression and (ii) anthropogenic aerosols transported from inland. Moreover, measurements of accumulation and coarse mode particles with diameter ranging from 0.1 to 3 μm and cloud droplets in the range 3 to 47 μm show systematic growth associated with cloud microphysical/rain formation process. On the other hand, no such evidence of increasing particle concentration and growth has been observed at about 60 km from coastline towards southeast during RF2. Evidently, the rain event observed during the night hours of 19 October caused the washout and scavenging of aerosols which contributed towards the decreased aerosol concentration observed near the coast

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Not AvailableExpert systems are computer programs (may be extended to mobile interfaces) that solve problems by mimicking human reasoning processes, relying on logic, rules of thumb opinion and experience. Rice Expert System has been developed for extension professionals and farmers to act as an interface to diagnose the field problems. Generally farmers face problems like choosing suitable varieties, knowledge on pesticides/fungicides application, pest and disease problems, yield losses etc. which conventionally difficult to address. An attempt was made to develop an expert system for rice varieties, pests and diseases to aid in the decision making at farm level. This expert system consists of series of questions and answers to diagnose the problem, to browse directly major pests/diseases/varieties, to access information on better crop protection measures, commonly used pesticides for rice and frequently asked questions.On line expert system is a dynamic system to diagnose pest and disease problems at field level. The alpha version of the system was successfully hosted on public domain and can be upgraded for various ecosystems. This facility is expected to aid and enhance the performance of progressive farmers and agricultural extension personnel and reduce the time required to tackle biotic stresses without waiting for an expert advice. Further this system can be integrated with mobile phones to reach each and every farmer of the country.This has been designed to help extension workers, farmers and other stakeholders in identifying the field problems they face in Indian rice fields. The diagnostics is basically based on the stage of the crop, but has options to select or search at any point based on symptoms, type of problems. The tool helps to identify the possible causal agent and the management options in brief. Varietal and management techniques can also be browsed through based on the agro-climatic conditions across the country. Similar comprehensive expert systems across the major crops in India will help extension system to be more effective. Key words : Expert systems, Interface, suitable varieties, agro-climatic conditions.Not Availabl

Aircraft observations of elevated pollution layers near the foothills of the Himalayas during CAIPEEX-2009

Pre-monsoon aerosols in the northern part of India may play an important role in the advancement of the monsoon. This study investigates the properties of aerosols and their spatial and vertical distribution near the foothills of the Himalayas using data from an instrumented aircraft during the Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX), 2009. CAIPEEX was conducted over five days during May 2009 in the northern part of India near the foothills of the Himalayas. On all the flight days thick haze was observed, with elevated aerosol layers up to 4 km with varying concentrations. The sources are identified as being from local anthropogenic activities such as biomass burning, as inferred from MODIS fire maps and dust from local as well as from long-range transport, as suggested by trajectory analysis. The aerosol size distributions depict the increases in both fine and coarse mode aerosols in polluted layers. This indicates that aerosols over this region are well mixed and the vertical distribution is a mixture of both biomass burning and dust aerosols at different altitudes, as also observed by CALIPSO and inferred from Mie calculations. Clouds observed above the elevated aerosol layers showed higher droplet concentrations (200-1400 cm -3) with small effective radii (3.5 to < 6 μm). Ice phase observed above 6 km at temperatures lower than -14°C might be due to the presence of dust aerosol acting as potential ice nuclei

Microstructural, thermal and electrical properties of electron irradiated Li₂CO₃ doped PVA

616-620Poly (vinyl alcohol) doped with Li2CO3 composite films have been prepared by solvent casting method and irradiated with energetic electrons. The FTIR study shows that the electron irradiation creates free radicals, chain scission and cross-linking within the polymer composite. The effect of these changes induces structural modifications and enhances the amorphosity of the composite, which has been studied using X-ray diffraction method. The thermal properties have been studied using thermogravimetric analysis and it has been found that the onset temperature (To) of decomposition increases up to 150 kGy and then decreases for higher doses. Using this data activation energy of the thermal decomposition has been determined which is in good corroborated with To values. This indicates that the cross-linking of polymer chains takes place in lower dose and the cleavage occurs at higher doses. The DC conductivity results show that the conductivity increases up to 1.0103×10-3S/cm for 300 kGy doses