Exposure-plant response of ambient ozone over the tropical Indian region

A high resolution regional chemistry-transport model has been used to study the distribution of exposure-plant response index (AOT40, Accumulated exposure Over a Threshold of 40 ppb, expressed as ppb h) over the Indian geographical region for the year 2003 as case study. The directives on ozone pollution in ambient air provided by United Nations Economic Commission for Europe (UNECE) and World Health Organization (WHO) for vegetation protection (AOT40) have been used to assess the air quality. A substantial temporal and spatial variation in AOT40 values has been observed across the Indian region. Large areas of India show ozone values above the AOT40 threshold limit (3000 ppb h for 3 months). Simulated AOT40 values are found to be substantially higher throughout the year over the most fertile Indo-Gangetic plains than the other regions of India, which can have an adverse effect on plants and vegetation in this region. The observed monthly AOT40 values reported from an Indian station, agree reasonably well with model simulated results. There is an underestimation of AOT40 in the model results during the periods of highest ozone concentration from December to March. We find that the simulated AOT40 target values for protection of vegetation is exceeded even in individual months, especially during November to April. Necessary and effective emission reduction strategies are therefore required to be developed in order to curb the surface level ozone pollution to protect the vegetation from further damage in India whose economy is highly dependent on agricultural sector and may influence the global balance

Relationship between Size of Cloud Ice and Lightning in the Tropics

The association of lightning flashes with mean cloud ice size over continental and oceanic region in the tropical areas has been analyzed using the observations from various satellite platforms (MODIS, TRMM, and LIS) for the period 2000–2011. We found that frequency of lightning in general is higher over the continental region compared to oceanic region, whereas larger size of cloud ice is observed over the oceanic regions compared to the continental regions. Relationship between lighting and cloud ice size shows similar features over both continental and oceanic regions. For the first time, we show that total lighting increases with increase in the cloud ice size; attends maximum at certain cloud ice size and then decreases with increase in cloud ice size. Maximum lightning occurred for the mean cloud ice size of around 23–25 µm over the continental region and mean cloud ice size of around 24–28 µm over the oceanic region. Based on our observation we argue that the relation between lightning and mean cloud ice size follow the curve linear pattern, and not linear

Radiative Forcing of Black Carbon over Delhi

The radiative effects of black carbon (BC) aerosols over New Delhi, the capital city of India, for the period August 2010–July 2011, have been investigated using Santa Barbara DISTORT Atmospheric Radiative Transfer (SBDART) model in the present paper. The monthly mean BC concentrations in Delhi, an urban location, vary in between 15.935 ± 2.06 μg m−3 (December 2010)–2.44 ± 0.58 μg m−3 (July 2011). The highest value for monthly mean BC forcing has been found to be in November 2010 (66.10 ± 6.86 Wm−2) and the lowest in July 2011 (23 ± 3.89 Wm−2). Being the host city for the XIX Commonwealth Games (CWG-2010), government of Delhi set up a plan to reduce emissions of air pollutants during Games, from 03 October to 14 October, 2010. But opposite to the expectations, the emission controls implemented were not sufficient to reduce the pollutants like black carbon (BC), and therefore relatively a high value of BC radiative forcing (44.36 ± 2.4) was observed during the month of October 2010

The stilbene biosynthetic pathway and its regulation in Scots pine

Conifers dominate the boreal forests of the Northern Hemisphere, and especially members of the family Pinaceae have great economic and ecological significance. Part of their success is thought to arise from the vast array of secondary metabolites they produce. The products of secondary metabolism are essential for plants to survive in the ever-changing environment. In Scots pine (Pinus sylvestris L.), two groups of secondary metabolites, stilbenes and resin acids, are crucial for decay resistance of heartwood timber and for active defense responses against herbivores and fungal pathogens. Several studies have shown that stilbenes improve decay resistance of pine heartwood. Since there is wide variation in the concentration of stilbenes between individuals and the trait has high heritability, it may be possible to breed heartwood that is more decay-resistant. However, breeding for heartwood properties is slow, since the decay resistance characteristics can be estimated at the earliest from 30-year-old trees. Early selection methods utilizing genetic markers or chemical screening are needed, but we do not yet understand which genes control the biosynthesis of stilbenes and what the genetic differences are between individuals that explain the variation in the capacity to produce stilbenes. Importantly, there is genetic correlation between stress-induced stilbene biosynthesis in seedlings and the heartwood stilbene content in their adult mother trees. Here, we examined the pine transcriptional responses under two conditions that were previously known to activate stilbene biosynthesis: heartwood formation in adult trees and ultraviolet (UV)-C treatment of needles in seedlings. We found that these two conditions had very little in common, except for the activation of stilbene pathway genes. For example, the regulators of the two responses seemed not to be shared. The activation of the stilbene pathway in response to UV-C treatment occurred a few hours after the onset of the treatment and was independent of translation. Stilbene biosynthesis seems to be an early defense response in Scots pine. Heartwood formation, an important developmental process in the senescence of secondary xylem, is poorly understood. Based on transcriptomic analysis, stilbene biosynthesis occurs in situ in the transition zone between the sapwood and heartwood, but resin acids were synthesized primarily in the sapwood. Bifunctional nuclease, an enzyme involved in the process of developmentally programmed cell death (dPCD), is a useful marker for heartwood formation and aided us in defining the timing of the process, from spring to late autumn. Expression of this marker, which is strictly confined to dPCD conditions, further clarified that heartwood formation truly is a process that is initiated by intrinsic programming instead of environmental cues. The transcriptomic data revealed that the expression of the previously characterized pinosylvin O-methyltransferase gene, PMT1, was not induced under stilbene-forming conditions. A new PMT-encoding gene, PMT2, was identified by coexpression analysis. The gene showed an inducible expression pattern very similar to that of the stilbene synthase gene under all conditions studied. PMT2 furthermore methylated pinosylvin with high specificity, in contrast to PMT1, which accepted several substrates.Pohjoisen pallonpuoliskon kasvillisuus on havumetsien hallitsemaa ja etenkin mäntykasvien (Pinaceae) heimoon kuuluu taloudellisesti ja ekologisesti merkittäviä lajeja. Yksi selitys havupuiden menestykselle saattaa olla niiden kyky tuottaa laaja kirjo erilaisia sekundaariyhdisteitä. Männyn (Pinus sylvestris L.) tärkeimpiin sekundaariyhdisteisiin kuuluvat stilbeenit ja terpeenit toimivat puolustuksessa tuholaisia ja patogeenejä vastaan. Aikaisemmat tutkimukset ovat osoittaneet, että aktiivisen puolustuksen lisäksi etenkin stilbeenit parantavat männyn sydänpuun lahonkestävyyttä. Sydänpuun stilbeenien määrä vaihtelee huomattavasti yksilöiden välillä ja ominaisuus on periytyvä, mikä mahdollistaa sydänpuun lahonkestävyyden parantamisen jalostuksen keinoin. Sydänpuun laatuominaisuuksien jalostus on kuitenkin hidasta ja varhaisvalintaan soveltuvien geenimerkkien tunnistaminen nopeuttaisi jalostusprosessia. Emme kuitenkaan vielä tiedä, mitkä geenit säätelevät stilbeenien biosynteesiä ja selittävät erot sydänpuun stilbeenien määrässä. Stilbeenien tuotanto käynnistyy erilaisten stressitekijöiden vaikutuksesta neulasissa ja mantopuussa. Indusoituva tuotanto korreloi sydänpuun stilbeenien määrän kanssa ja tätä voidaan mahdollisesti hyödyntää kemiallisessa seulonnassa taimien varhaisvalinnassa. Tässä väitöskirjassa tutkittiin muutoksia männyn transkriptomissa sydänpuun muodostumisen aikana ja UV-C käsittelyn seurauksena. Stilbeenien biosynteesireitin entsyymejä koodavat geenit aktivoituivat kummassakin tapauksessa, mutta muuten transkriptomeilla oli hyvin vähän yhteistä. Esimerkiksi yhteisiä transkriptiota sääteleviä tekijöitä ei löydetty ja vaikuttaakin siltä, että eri transkriptiofaktorit säätelevät stilbeenien biosynteesireittiä sydänpuun kehityksen aikana ja stressitekijöiden vaikutuksesta. Sydänpuun muodostumisen aikana puussa tapahtuvat kemialliset ja rakenteelliset muutokset tunnetaan joillakin lajeilla hyvin, mutta itse prosessin ajoittuminen sekä käynnistymiseen ja säätelyyn vaikuttavat tekijät ovat vielä suurelta osin tuntemattomia. Stilbeenin biosynteesistä vastaavat geenit ilmenivät vaihettumisvyöhykkeellä mantopuun ja sydänpuun välissä, jossa sydänpuun muodostuminen käynnistyy ja näin tukee aiempaa käsitystä stilbeenien in situ biosynteesistä. Hartsihappojen biosynteesistä vastaavat geenit taas ilmenivät lähinnä mantopuussa, jolloin ne todennäköisesti kuljetetaan vaihettumisvyöhykkeelle sen ulkopuolelta. Ohjelmoidulla solukuolemalla on suuri merkitys sekä kasvin kehityksessä, että stressivasteissa. Bifunktionaalinen nukleaasi (BFN) on entsyymi, joka on yhdistetty aiemmissa tutkimuksissa spesifisesti kasvien kehityksellisiin tapahtumiin. Entsyymiä koodaavan geenin havaittiin ilmenevän ainoastaan vaihettumisvyöhykkeellä. Tämä tukee hypoteesia, jonka mukaan sydänpuun muodostuminen on sisäisesti säädelty eikä ympäristötekijöiden laukaisema tapahtuma. Bifunktionaalinen nukleaasi toimi myös hyödyllisenä markkerina sydänpuun muodostumisen ajoittamisessa keväästä myöhäiseen syksyyn. Transkriptiodata paljasti, että aiemmin tunnistettu stilbeenireitin viimeistä reaktiota katalysoiva metyylitransferaasientsyymiä (PMT1) koodaava geeni ei indusoitunut tutkituissa stilbeenejä tuottavissa olosuhteissa. Tunnistimme uuden metyylitransferaasia koodaavan geenin (PMT2), jonka ekspressioprofiili vastasi stilbeenireitin toisen entsyymin, stilbeenisyntaasin ekspressiota kaikissa tutkituissa olosuhteissa. PMT2 metyloi spesifisesti pinosylviiniä kun taas PMT1 metyloi stilbeenien lisäksi useita rakenteellisesti erilaisia substraatteja

Forecasts of fog events in northern India dramatically improve when weather prediction models include irrigation effects

Dense wintertime fog regularly impacts Delhi, severely affecting road and rail transport, aviation and human health. Recent decades have seen an unexplained increase in fog events over northern India, coincident with a steep rise in wintertime irrigation associated with the introduction of double-cropping. Accurate fog forecasting is challenging due to a high sensitivity to numerous processes across many scales, and uncertainties in representing some of these in state-of-the-art numerical weather prediction models. Here we show fog event simulations over northern India with and without irrigation, revealing that irrigation counteracts a common model dry bias, dramatically improving the simulation of fog. Evaluation against satellite products and surface measurements reveals a better spatial extent and temporal evolution of the simulated fog events. Increased use of irrigation over northern India in winter provides a plausible explanation for the observed upward trend in fog events, highlighting the critical need for optimisation of irrigation practices

Analysis of atmospheric ammonia over South and East Asia based on the MOZART-4 model and its comparison with satellite and surface observations

Limited availability of atmospheric ammonia (NH3) observations limits our understanding of controls on its spatial and temporal variability and its interactions with the ecosystem. Here we used the Model for Ozone and Related chemical Tracers version 4 (MOZART-4) global chemistry transport model and the Hemispheric Transport of Air Pollution version 2 (HTAP-v2) emission inventory to simulate global NH3 distribution for the year 2010. We presented a first comparison of the model with monthly averaged satellite distributions and limited ground-based observations available across South Asia. The MOZART-4 simulations over South Asia and East Asia were evaluated with the NH3 retrievals obtained from the Infrared Atmospheric Sounding Interferometer (IASI) satellite and 69 ground-based monitoring stations for air quality across South Asia and 32 ground-based monitoring stations from the Nationwide Nitrogen Deposition Monitoring Network (NNDMN) of China. We identified the northern region of India (Indo-Gangetic Plain, IGP) as a hotspot for NH3 in Asia, both using the model and satellite observations. In general, a close agreement was found between yearly averaged NH3 total columns simulated by the model and IASI satellite measurements over the IGP, South Asia (r=0.81), and the North China Plain (NCP), East Asia (r=0.90). However, the MOZART-4-simulated NH3 column was substantially higher over South Asia than East Asia, as compared with the IASI retrievals, which show smaller differences. Model-simulated surface NH3 concentrations indicated smaller concentrations in all seasons than surface NH3 measured by the ground-based observations over South and East Asia, although uncertainties remain in the available surface NH3 measurements. Overall, the comparison of East Asia and South Asia using both MOZART-4 model and satellite observations showed smaller NH3 columns in East Asia compared with South Asia for comparable emissions, indicating rapid dissipation of NH3 due to secondary aerosol formation, which can be explained by larger emissions of acidic precursor gases in East Asia