scholarly journals Growth in mid-monsoon dry phases over the Indian region: prevailing influence of anthropogenic aerosols

2019 ◽  
Vol 19 (19) ◽  
pp. 12325-12341 ◽  
Author(s):  
Rohit Chakraborty ◽  
Bijay Kumar Guha ◽  
Shamitaksha Talukdar ◽  
Madineni Venkat Ratnam ◽  
Animesh Maitra
Keyword(s):  
Large Scale ◽  
Potential Evapotranspiration ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Anthropogenic Aerosols ◽  
Gangetic Plain ◽  
Rcp 8.5 ◽  
Urbanized Region ◽  
Indo Gangetic Plain

Abstract. A detailed investigation on the potentially drought-prone regions over India is presented in this study based on the balance between precipitation and potential evapotranspiration (PET) during the southwest Asian mid-monsoon season. We introduce a parameter named dry day frequency (DDF) which is found suitable to present the drought index (DI) in mid-monsoon season, hence strongly associated with the possibility of drought occurrences. The present study investigates the probable aspects which influence the DDF over these regions, revealing that the abundance of anthropogenic aerosols especially over urbanized locations has a prevailing role in the growth of DDF during the last few decades. The prominent increasing trend in DDF over Lucknow (26.84∘ N, 80.94∘ E), a densely populated urban location situated in the Indo-Gangetic Plain, strongly reflects the dominant association of anthropogenic aerosols with the increasing dry phase occurrences. Increase in DDF (∼90 %) during the last 60 years is observed over this urban area compared to a broader region in its surroundings. In addition, periodic impacts of large-scale phenomena like ENSO (El Niño–Southern Oscillation) or SSN (sunspot number) become weaker when the study location is downscaled towards an urbanized region. Finally, when long-term projections of DDF are drawn using the high urbanization scenario of RCP 8.5, a huge rise in dry days is seen during mid-July to mid-September (reaching up to 50 dry days by the year 2100 over Lucknow), which will be a crucial concern for policymakers in future.

scholarly journals Growth in mid-monsoon dry phases over Indian region: Prevailing influence of anthropogenic aerosols

2019 ◽  
Author(s):  
Rohit Chakraborty ◽  
Bijay Kumar Guha ◽  
Shamitaksha Talukdar ◽  
Madineni Venkat Ratnam ◽  
Animesh Maitra
Keyword(s):  
Potential Evapotranspiration ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Anthropogenic Aerosols ◽  
Gangetic Plain ◽  
Policy Makers ◽  
North West ◽  
Spot Number ◽  
Rcp 8.5 ◽  
Urbanized Region

Abstract. A detailed investigation on the potentially drought prone regions over India has been presented in this study based on the balance between precipitation and potential evapotranspiration (PET) during the South West Asian mid-monsoon season. We methodically introduce a parameter named dry day frequency (DDF) which is found suitable to present the drought index (DI) in mid-monsoon season hence strongly associated with the possibility of drought occurrences. The present study investigates the probable aspects which influence the DDF over these regions revealing that the abundance of anthropogenic aerosols especially over urbanized location have prevailing role on the growth of DDF during last few decades. The prominent increasing trend in DDF over Lucknow (26.84° N, 80.94° E), a densely populated urban location situated in the Indo-Gangetic plain, strongly reflects the dominant association of man-made aerosols with the increasing dry phase occurrences. Increase in DDF (~ 90 %) during the last 60 years is observed over this urban area compared to a broader region in its surroundings. In addition, periodic impacts of synoptic scale phenomena like ENSO (El Niño–Southern Oscillation) or SSN (Sun spot number) become weaker when the study location is downscaled towards an urbanized region. However, there still remains some unclear role of air-mass transport on DDF over the potential drought prone region of north-west India. Finally, when long term projections of DDF are drawn using the high urbanization scenario of RCP 8.5 a huge rise in dry days are seen during mid-July to mid-September (reaching up to 50 dry days by the year 2100 over Lucknow) which will be a very crucial concern for policy makers in future.

scholarly journals Long term MAX-DOAS measurements of NO<sub>2</sub>, HCHO and aerosols and evaluation of corresponding satellite data products over Mohali in the Indo-Gangetic plain

2020 ◽  
Author(s):  
Vinod Kumar ◽  
Steffen Beirle ◽  
Steffen Dörner ◽  
Abhishek Kumar Mishra ◽  
Sebastian Donner ◽  
...  
Keyword(s):  
Monsoon Season ◽  
Ozone Production ◽  
Data Set ◽  
Gangetic Plain ◽  
Agricultural Residue ◽  
Modis Aod ◽  
Tropospheric No2 ◽  
The Difference ◽  
Indo Gangetic Plain

Abstract. We present comprehensive long term ground-based MAX-DOAS measurements of aerosols, nitrogen dioxide (NO2) and formaldehyde (HCHO) from Mohali (30.667° N, 76.739° E, 310 m above mean sea level), located in the densely populated Indo-Gangetic Plain (IGP) of India. We investigate the temporal variation and vertical profiles of aerosols, NO2 and HCHO and identify factors driving their ambient levels and distributions for the period from January 2013 to June 2017. We observed mean aerosol optical depth (AOD) at 360 nm, tropospheric NO2 vertical column density (VCD) and tropospheric HCHO VCD for the measurement period to be 0.63 ± 0.51, (6.7 ± 4.1) × 1015 molecules cm−2 and (13.2 ± 9.8) × 1015 molecules cm−2, respectively. Concerning the tropospheric NO2 VCDs, Mohali was found to be less polluted than urban and suburban locations of China and western countries, but comparable HCHO VCDs were observed. High tropospheric NO2 VCDs were observed in periods with enhanced biomass and biofuel combustion (e.g. agricultural residue burning and domestic burning for heating). Highest tropospheric HCHO VCDs were observed in agricultural residue burning periods with favourable meteorological conditions for photochemical formation, which in previous studies have shown an implication on high ambient ozone also over the IGP. Highest AOD is observed in the monsoon season, indicating possible hygroscopic growth of the aerosol particles. Most of the NO2 is located close to the surface, whereas significant HCHO is present at higher altitudes up to 600 meters. The vertical distribution of aerosol was found to be linked to the boundary layer height. The ground-based data set was also used for satellite validation. High-resolution MODIS AOD measurements correlate well but were systematically higher than MAX-DOAS AODs. NO2 VCDs from OMI correlate reasonably with MAX-DOAS VCDs, but are lower by ~ 30–50 % due to the difference in vertical sensitivities and the rather large OMI footprint. OMI HCHO VCDs exceed the MAX-DOAS VCDs by up to 30 %. For surface volume mixing ratio (VMR), MAX-DOAS NO2 measurements show a good correlation but a slight overestimation compared to the in situ measurements. However, for HCHO, a larger bias was observed due to large measurement uncertainties. The difference in vertical representativeness was found to be crucial for the observed biases in NO2 and HCHO inter-comparisons. Using the ratio of NO2 and HCHO VCDs measured from MAX-DOAS, we have found that the peak daytime ozone production regime is sensitive to both NOx and VOCs in winter but strongly sensitive to NOx in other seasons.

On the frequency of the 2015 monsoon season drought in the Indo-Gangetic Plain

2016 ◽  
Vol 43 (23) ◽  
pp. 12,102-12,112 ◽  
Author(s):  
Vimal Mishra ◽  
Saran Aadhar ◽  
Akarsh Asoka ◽  
Sivananda Pai ◽  
Rohini Kumar
Keyword(s):  
Monsoon Season ◽  
Gangetic Plain ◽  
Indo Gangetic Plain

scholarly journals Explaining the trends and variability in the United States tornado records using climate teleconnections and shifts in observational practices

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Niloufar Nouri ◽  
Naresh Devineni ◽  
Valerie Were ◽  
Reza Khanbilvardi
Keyword(s):  
Population Density ◽  
Large Scale ◽  
Southern Oscillation ◽  
The United States ◽  
Anthropogenic Factors ◽  
Climate Variables ◽  
Term Trend ◽  
Cyclical Variability ◽  
Long Term Trend

AbstractThe annual frequency of tornadoes during 1950–2018 across the major tornado-impacted states were examined and modeled using anthropogenic and large-scale climate covariates in a hierarchical Bayesian inference framework. Anthropogenic factors include increases in population density and better detection systems since the mid-1990s. Large-scale climate variables include El Niño Southern Oscillation (ENSO), Southern Oscillation Index (SOI), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), Arctic Oscillation (AO), and Atlantic Multi-decadal Oscillation (AMO). The model provides a robust way of estimating the response coefficients by considering pooling of information across groups of states that belong to Tornado Alley, Dixie Alley, and Other States, thereby reducing their uncertainty. The influence of the anthropogenic factors and the large-scale climate variables are modeled in a nested framework to unravel secular trend from cyclical variability. Population density explains the long-term trend in Dixie Alley. The step-increase induced due to the installation of the Doppler Radar systems explains the long-term trend in Tornado Alley. NAO and the interplay between NAO and ENSO explained the interannual to multi-decadal variability in Tornado Alley. PDO and AMO are also contributing to this multi-time scale variability. SOI and AO explain the cyclical variability in Dixie Alley. This improved understanding of the variability and trends in tornadoes should be of immense value to public planners, businesses, and insurance-based risk management agencies.

Oceanography of the New Zealand subantarctic region

2021 ◽  
Author(s):  
◽  
Aitana Forcén-Vázquez
Keyword(s):  
New Zealand ◽  
Interannual Variability ◽  
Water Column ◽  
Large Scale ◽  
Southern Oscillation ◽  
Complex Structure ◽  
Positive Trend ◽  
Intermediate Water ◽  
Subantarctic Region

<p>Subantarctic New Zealand is an oceanographycally dynamic region with the Subtropical Front (STF) to the north and the Subantarctic Front (SAF) to the south. This thesis investigates the ocean structure of the Campbell Plateau and the surrounding New Zealand subantarctic, including the spatial, seasonal, interannual and longer term variability over the ocean properties, and their connection to atmospheric variability using a combination of in-situ oceanographic measurements and remote sensing data.  The spatial and seasonal oceanographic structure in the New Zealand subantarctic region was investigated by analysing ten high resolution Conductivity Temperature and Depth (CTD) datasets, sampled during oceanographic cruises from May 1998 to February 2013. Position of fronts, water mass structure and changes over the seasons show a complex structure around the Campbell Plateau combining the influence of subtropical and subantarctic waters.  The spatial and interannual variability on the Campbell Plateau was described by analysing approximately 70 low resolution CTD profiles collected each year in December between 2002 and 2009. Conservative temperature and absolute salinity profiles reveal high variability in the upper 200m of the water column and a homogeneous water column from 200 to 600m depth. Temperature variability of about 0.7 °C, on occasions between consecutive years, is observed down to 900m depth. The presence of Subantarctic Mode Water (SAMW) on the Campbell Plateau is confirmed and Antarctic Intermediate Water (AAIW) reported for the first time in the deeper regions around the edges of the plateau.  Long-term trends and variability over the Campbell Plateau were investigated by analysing satellite derived Sea Level Anomalies (SLA) and Sea Surface Temperature (SST) time series. Links to large scale atmospheric processes are also explored through correlation with the Southern Oscillation Index (SOI) and Southern Annular Mode (SAM). SST shows a strong seasonality and interannual variability which is linked to local winds, but no significant trend is found. The SLA over the Campbell Plateau has increased at a rate of 5.2 cm decade⁻¹ in the last two decades. The strong positive trend in SLA appears to be a combination of the response of the ocean to wind stress curl (Ekman pumping), thermal expansion and ocean mass redistribution via advection amongst others.  These results suggest that the variability on the Campbell Plateau is influenced by the interaction of the STF and the SAF. The STF influence reaches the limit of the SAF over the western Campbell Plateau and the SAF influence extends all around the plateau. Results also suggest different connections between the plateau with the surrounding oceans, e.g., along the northern edge with the Bounty Trough and via the southwest edge with the SAF. A significant correlation with SOI and little correlation with SAM suggest a stronger response to tropically driven processes in the long-term variability on the Campbell Plateau.  The results of this thesis provide a new definitive assessment of the circulation, water masses and variability of the Campbell Plateau on mean, annual, and interannual time scales which will support research in other disciplines such as palaeoceanography, fisheries management and climate.</p>

scholarly journals Assessment of Water Quality in Indo-Gangetic Plain of South-Eastern Asia under Organic vs. Conventional Rice Farming

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 960
Author(s):  
Debjani Sihi ◽  
Biswanath Dari ◽  
Zhengjuan Yan ◽  
Dinesh Kumar Sharma ◽  
Himanshu Pathak ◽  
...  
Keyword(s):  
Water Quality ◽  
Quality Parameters ◽  
Basmati Rice ◽  
Conventional Farming ◽  
Eastern Asia ◽  
Gangetic Plain ◽  
South Eastern ◽  
The Impact ◽  
Indo Gangetic Plain

Water contamination is often reported in agriculturally intensive areas such as the Indo-Gangetic Plain (IGP) in south-eastern Asia. We evaluated the impact of the organic and conventional farming of basmati rice on water quality during the rainy season (July to October) of 2011 and 2016 at Kaithal, Haryana, India. The study area comprised seven organic and seven conventional fields where organic farming has been practiced for more than two decades. Water quality parameters used for drinking (nitrate, NO3; total dissolved solids (TDS); electrical conductivity (EC) pH) and irrigation (sodium adsorption ratio (SAR) and residual sodium carbonate (RSC)) purposes were below permissible limits for all samples collected from organic fields and those from conventional fields over the long-term (~15 and ~20 years). Importantly, the magnitude of water NO3 contamination in conventional fields was approximately double that of organic fields, which is quite alarming and needs attention in future for farming practices in the IGP in south-eastern Asia.

scholarly journals Long-term aerosol climatology over Indo-Gangetic Plain: Trend, prediction and potential source fields

2018 ◽  
Vol 180 ◽  
pp. 37-50 ◽  
Author(s):  
M. Kumar ◽  
K.S. Parmar ◽  
D.B. Kumar ◽  
A. Mhawish ◽  
D.M. Broday ◽  
...  
Keyword(s):  
Trend Prediction ◽  
Gangetic Plain ◽  
Potential Source ◽  
Indo Gangetic Plain

scholarly journals Development of a global dataset of Wetland Area and Dynamics for Methane Modeling (WAD2M)

2020 ◽  
Author(s):  
Zhen Zhang ◽  
Etienne Fluet-Chouinard ◽  
Katherine Jensen ◽  
Kyle McDonald ◽  
Gustaf Hugelius ◽  
...  
Keyword(s):  
Land Surface ◽  
Large Scale ◽  
Southern Oscillation ◽  
Microwave Remote Sensing ◽  
Global Scale ◽  
Annual Maximum ◽  
Time Step ◽  
Wetland Area ◽  
Wetland Extent

Abstract. Seasonal and interannual variations in global wetland area is a strong driver of fluctuations in global methane (CH4) emissions. Current maps of global wetland extent vary with wetland definition, causing substantial disagreement and large uncertainty in estimates of wetland methane emissions. To reconcile these differences for large-scale wetland CH4 modeling, we developed a global Wetland Area and Dynamics for Methane Modeling (WAD2M) dataset at ~25 km resolution at equator (0.25 arc-degree) at monthly time-step for 2000–2018. WAD2M combines a time series of surface inundation based on active and passive microwave remote sensing at coarse resolution (~25 km) with six static datasets that discriminate inland waters, agriculture, shoreline, and non-inundated wetlands. We exclude all permanent water bodies (e.g. lakes, ponds, rivers, and reservoirs), coastal wetlands (e.g., mangroves and sea grasses), and rice paddies to only represent spatiotemporal patterns of inundated and non-inundated vegetated wetlands. Globally, WAD2M estimates the long-term maximum wetland area at 13.0 million km2 (Mkm2), which can be separated into three categories: mean annual minimum of inundated and non-inundated wetlands at 3.5 Mkm2, seasonally inundated wetlands at 4.0 Mkm2 (mean annual maximum minus mean annual minimum), and intermittently inundated wetlands at 5.5 Mkm2 (long-term maximum minus mean annual maximum). WAD2M has good spatial agreements with independent wetland inventories for major wetland complexes, i.e., the Amazon Lowland Basin and West Siberian Lowlands, with high Cohen's kappa coefficient of 0.54 and 0.70 respectively among multiple wetlands products. By evaluating the temporal variation of WAD2M against modeled prognostic inundation (i.e., TOPMODEL) and satellite observations of inundation and soil moisture, we show that it adequately represents interannual variation as well as the effect of El Niño-Southern Oscillation on global wetland extent. This wetland extent dataset will improve estimates of wetland CH4 fluxes for global-scale land surface modeling. The dataset can be found at http://doi.org/10.5281/zenodo.3998454 (Zhang et al., 2020).

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