scholarly journals Assessment of Recent Changes in Dust over South Asia Using RegCM

2021 ◽  
Author(s):  
A Asutosh ◽  
S. K Pandey ◽  
V Vinoj
Keyword(s):  
Radiative Forcing ◽  
Monsoon Rainfall ◽  
Water Cycle ◽  
Regional Climate ◽  
Short Wave ◽  
Positive Trend ◽  
Indian Landmass ◽  
Desert Regions ◽  
Semi Arid

Pre-monsoon dust aerosols over Indian regions are closely linked to the monsoon dynamics and Indian summer monsoon rainfall. Past observational studies have shown a decline in dust loading over the Indian landmass potentially caused by changing rainfall patterns over the desert regions. Such changes are expected to have far reaching impact on regional energy balance and monsoon rainfall. Using a regional climate-chemistry model, RegCM4.5 with an updated land module, we have simulated the long-term (2001-2015) changes in dust over the arid and semi-arid dust source regions of the North-Western part of the sub-continent. It is found that the area-averaged dust aerosol optical depth (AOD) over the arid and semi-arid desert regions has declined by 17% since the start of this millennium. The rainfall over these regions exhibits a positive trend of 0.1 mm day-1year-1 and a net increase of > 50%. The wet deposition is found to be dominant and ~5 fold larger in magnitude over dry deposition and exhibits total changes of ~ 79 % and 48% in the trends in atmospheric dust. As a response, significant change in the surface (11%), top of the atmosphere radiative forcing (7%), and widespread atmospheric cooling are observed in short wave domain of radiation spectrum, over the Northern part of the Indian landmass. Such quantification and long term change studies are necessary for understanding the regional climate change and the water cycle.

Long-term (2008–2017) analysis of atmospheric composite aerosol and black carbon radiative forcing over a semi-arid region in southern India: Model results and ground measurement

2020 ◽  
Vol 240 ◽  
pp. 117840
Author(s):  
Raja Obul Reddy Kalluri ◽  
Balakrishnaiah Gugamsetty ◽  
Rama Gopal Kotalo ◽  
Lokeswara Reddy Thotli ◽  
Chakradhar Rao Tandule ◽  
...  
Keyword(s):  
Black Carbon ◽  
Arid Region ◽  
Radiative Forcing ◽  
Southern India ◽  
Ground Measurement ◽  
Semi Arid Region ◽  
Semi Arid

A multi-century spring precipitation history for northern Iran derived from tree-ring δ18O 

2021 ◽  
Author(s):  
Zeynab Foroozan ◽  
Jussi Grießinger ◽  
Kambiz Pourtahmasi ◽  
Achim Bräuning
Keyword(s):  
Tree Ring ◽  
Large Scale ◽  
Regional Climate ◽  
Spring Precipitation ◽  
Northern Iran ◽  
The Past ◽  
Precipitation Record ◽  
Hydroclimatic Variability ◽  
Semi Arid

<p>Knowledge about the long-term hydroclimatic variability is essential to analyze the historic course and recent impact of climate change, especially in semi-arid and arid regions of the world. In this study, we present the first tree-ring δ<sup>18</sup>O chronology for the semi-arid parts of northern Iran based on juniper trees. We were able to reconstruct past hydroclimatic variability for the past 500 years. The highly significant correlation between tree-ring δ<sup>18</sup>O and spring precipitation indicates the primary influence of spring moisture availability on δ<sup>18</sup>O variations. The thereof derived precipitation reconstruction reveals short and long-term variability of precipitation intensity, duration, and frequency of dry/wet events. During the past 500 years, the driest period occurred in the 16<sup>th</sup> century, whereas the 18th century was comparably wet. A gradual decline in the reconstructed spring precipitation is evident since the beginning of the 19th century, culminating in the continuing drought of the 20<sup>th</sup> century. An analysis of dry/wet years indicated that over the last three centuries, the occurrence of years with a relatively dry spring is increasing. In contrast, more humid spring conditions are decreasing. However, the overall frequency of the occurrence of extreme events increased over the past five centuries. In addition, past hydrological disasters recorded in Persian history were well represented in our reconstruction. Correlations between our reconstructed precipitation record and large-scale circulation systems revealed no significant influence of large-scale climatic drivers on spring precipitation variations in north Iran, which therefore seem to be mostly controlled by a regional climate forcing.</p>

Long-term AOD trend analysis and Classification of major aerosol types over Iran from 1980 to 2018

2020 ◽  
Author(s):  
Robabeh Yousefi ◽  
Fang Wang ◽  
Quansheng Ge ◽  
Abdallah Shaheen ◽  
Juerg Luterbacher
Keyword(s):  
Trend Analysis ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Positive Trend ◽  
Desert Dust ◽  
Study Results ◽  
Southwest Of Iran ◽  
Aerosol Types

<p>Based on the importance of the effects of aerosols on climate pattern change, our study contributes towards a better understanding of the Aerosol Optical Depth (AOD) trends from different datasets and the contribution of each dominant aerosol over Iran. A long-term AOD dataset (1980–2018) from the reanalysis-based Modern Era Retrospective Analysis for Research and Applications (MERRA-2) and the satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS) /Terra Collection 6.1(C6.1) and Level 2 (L2) in the years 2001-2018. The result of AOD trend showed some differences between MERRA-2 and MODIS in autumn and winter.  But, generally, the increasing and slightly decreasing trends appeared over the southwest and north of the country, respectively. The upward trend was mainly observed in the southwest of Iran because of the proximity to the major source areas of natural mineral dust in spring and summer of both AOD datasets which was also obtained in the regional trend analysis and the city of Ahvaz experienced a strong positive trend compared with other selected cities. Also, an unforeseen downward trend was observed in the last decade. Finally, the classification of major aerosol types during 1980-2018 indicated that the mixed aerosols (43.28%) and clean marine (37.38%) were the dominate aerosols followed by the clean continental (9.78%) and desert dust (5.56%) with minor contributions of biomass burning/urban industrial (3.98%) aerosols. Later, the increase of desert dust around 2010 was another obvious result in spring and summer. Our study results indicate that the variation in dust aerosols has a key role in determining the AOD changes in Iran which are contributed in regional climate change and environmental evolutions.</p>

scholarly journals Comparison of Long-Term Changes in Non-Linear Aggregated Drought Index Calibrated by MERRA–2 and NDII Soil Moisture Proxies

Water ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 26
Author(s):  
Fhumulani Mathivha ◽  
Nkanyiso Mbatha
Keyword(s):  
Soil Moisture ◽  
Drought Index ◽  
Water Cycle ◽  
Critical Role ◽  
Phase Relationship ◽  
Positive Trend ◽  
Long Term Changes ◽  
Non Linear ◽  
Seasonal Correlation

This study aimed at evaluating Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA–2) and Normalized Difference Infrared Index (NDII) soil moisture proxies in calibrating a comprehensive Non-linear Aggregated Drought Index (NADI). Soil moisture plays a critical role in temperature variability and controlling the partitioning of water into evaporative fluxes as well as ensuring effective plant growth. Long-term variability and change in climatic variables such as precipitation, temperatures, and the possible acceleration of the water cycle increase the uncertainty in soil moisture variability. Streamflow, temperature, rainfall, reservoir storage, MERRA–2, and NDII soil moisture proxies’ data from 1986 to 2016 were used to formulate the NADI. The trend analysis was performed using the Mann Kendall, SQ-MK was used to determine the point of trend direction change while Theil-Sen trend estimator method was used to determine the magnitude of the detected trend. The seasonal correlation between the NADI-NDII and NADI-MERRA–2 was higher in spring and autumn with an R2 of 0.9 and 0.86, respectively. A positive trend was observed over the 30 years period of study, NADI-NDII trend magnitude was found to be 2.94 units per year while that of NADI-MERRA–2 was 1.21 units. Wavelet analysis showed an in-phase relationship with negligible lagging between the NDII and MERRA–2 calibrated NADI. Although a robust comparison is recommended between soil moisture proxies and observed soil moisture, the soil moisture proxies in this study were found to be useful in monitoring long-term changes in soil moisture.

scholarly journals Pan-European groundwater to atmosphere terrestrial systems climatology from a physically consistent simulation

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Carina Furusho-Percot ◽  
Klaus Goergen ◽  
Carl Hartick ◽  
Ketan Kulkarni ◽  
Jessica Keune ◽  
...  
Keyword(s):  
Land Surface ◽  
Climate Models ◽  
Water Cycle ◽  
Regional Climate ◽  
Regional Climate Models ◽  
Data Set ◽  
Groundwater Dynamics ◽  
Terrestrial System ◽  
Terrestrial Water

AbstractApplying the Terrestrial Systems Modeling Platform, TSMP, this study provides the first simulated long-term (1996–2018), high-resolution (~12.5 km) terrestrial system climatology over Europe, which comprises variables from groundwater across the land surface to the top of the atmosphere (G2A). The data set offers an unprecedented opportunity to test hypotheses related to short- and long-range feedback processes in space and time between the different interacting compartments of the terrestrial system. The physical consistency of simulated states and fluxes in the terrestrial system constitutes the uniqueness of the data set: while most regional climate models (RCMs) have a tendency to simplify the soil moisture and groundwater representation, TSMP explicitly simulates a full 3D soil- and groundwater dynamics, closing the terrestrial water cycle from G2A. As anthopogenic impacts are excluded, the dataset may serve as a near-natural reference for global change simulations including human water use and climate change. The data set is available as netCDF files for the pan-European EURO-CORDEX domain.

Radiative forcing of atmospheric brown clouds over the Indo-Gangetic Plain

2021 ◽  
Author(s):  
Manish Jangid ◽  
Amit Mishra
Keyword(s):  
Optical Depth ◽  
Radiative Forcing ◽  
Water Cycle ◽  
Monsoon Season ◽  
Regional Climate ◽  
Winter Season ◽  
Gangetic Plain ◽  
Post Monsoon ◽  
Using Data ◽  
Indo Gangetic Plain

<p>Atmospheric brown clouds (ABCs) are a dense and extensive pollution layer and have significant implications on air quality, agriculture, water cycle, and regional climate. The objective of the present study is to observe seasonal and spatial variations in the occurrence of ABCs and its radiative effects. The Indo-Gangetic plain (IGP) is the most populated region of India, which is an extended region in the foothills of the Himalayas. The IGP is one of the ABCs hotspots over the globe. The frequency of ABCs occurrences and radiative forcing were calculated using data from seven ground-based remote sensors situated across the IGP. We have used total ~ 5000 days of Level-2 aerosol measurements from seven AERosol Robotic NETwork (AERONET) stations (Karachi, Lahore, Jaipur, New Delhi, Kanpur, Gandhi college and Dhaka University) for three seasons (Pre-monsoon, Post-monsoon, and Winter) during 2000-2019. An algorithm based on the optical properties of aerosols is used to defined extreme pollution events (ABCs days) for each site. Our results show more frequent occurrences of ABCs over the region in the pre-monsoon out of all three seasons. However, spatial variation is found in all seasons, like maximum frequency of ABCs over western IGP region in post-monsoon and minimum is at eastern IGP region in the winter season. Further, we have used the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model to calculate radiative forcing during ABCs days on all sites of study. Aerosol optical depth (AOD) and absorption optical depth (AAOD) was used to calculate radiative forcing over the IGP region. Radiative forcing of ABCs is negative at both the surface (SRF) and top of the atmosphere (TOA), whereas it is positive in the atmosphere (ATM). In magnitude, it was found minimum in the pre-monsoon season at TOA. However, other seasons have specific features over specific locations, for example, in the winter season, radiative forcing is maximum over Kolkata at TOA, SRF, and ATM, which are -13.81 W/m<sup>2</sup>, -50.90 W/m<sup>2</sup>, and +37.09 W/m<sup>2</sup> respectively. In the pre-monsoon season, radiative forcing is maximum at Delhi (-9.59 W/m<sup>2</sup>) at TOA. In post-monsoon season radiative forcing maximum at Gandhi-college (-11.30 W/m<sup>2</sup>) at TOA. This ground observation is also compared with Modern Era Retrospective analysis and Research and Applications-2 (MEERA 2) modal data. These results indicate the cooling effect of ABCs at the surface and TOA over the IGP region throughout the period.</p>

scholarly journals Simulation of dust aerosol and its regional feedbacks over East Asia using a regional climate model

2009 ◽  
Vol 9 (4) ◽  
pp. 1095-1110 ◽  
Author(s):  
D. F. Zhang ◽  
A. S. Zakey ◽  
X. J. Gao ◽  
F. Giorgi ◽  
F. Solmon
Keyword(s):  
East Asia ◽  
Regional Climate Model ◽  
Radiative Forcing ◽  
Climate Model ◽  
Regional Climate ◽  
Short Wave ◽  
Dust Aerosol ◽  
Dust Aerosols ◽  
Source Regions ◽  
Long Wave

Abstract. The ICTP regional climate model (RegCM3) coupled with a desert dust aerosol model is used to simulate the net radiative forcing (short-wave and long-wave) and related climate effects of dust aerosols over East Asia. Two sets of experiments are completed and intercompared, one without (Exp. 1) and one with (Exp. 2) the radiative effects of dust aerosols. The experiments encompass the main dust producing months, February through May, for 10 years (1997–2006), and the simulation results are evaluated against ground station and satellite data. The model captures the basic observed climatology over the area of interest. The spatial and temporal variations of near surface concentration, mass load, optical depth and emission of dust aerosols from the main source regions are reproduced by model. The main model deficiency is an overestimate of dust amounts over the source regions and an underestimate downwind of these source areas, which indicates an underestimate of dust dispersal. Over the desert source regions, the net TOA radiative forcing is positive, while it is small over the other regions as a result of high surface albedo values which reduce the short-wave radiative forcing. The net surface radiative fluxes are decreased by dust and this causes a surface cooling locally up to −1°C. The inclusion of net (short-wave and long-wave) dust radiative forcing leads to a reduction of dust emission in the East Asia source regions, which is mainly caused by an increase in local stability and a corresponding decrease in dust lifting. Our results indicate that dust effects should be included in the assessment of climate change over East Asia.

scholarly journals Long-Term Projection of Water Cycle Changes over China Using RegCM

2021 ◽  
Vol 13 (19) ◽  
pp. 3832
Author(s):  
Chen Lu ◽  
Guohe Huang ◽  
Guoqing Wang ◽  
Jianyun Zhang ◽  
Xiuquan Wang ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Climate Model ◽  
Water Cycle ◽  
Regional Climate ◽  
Model Performance ◽  
Theoretical Physics ◽  
Mitigation Measures ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Wet Season

The global water cycle is becoming more intense in a warming climate, leading to extreme rainstorms and floods. In addition, the delicate balance of precipitation, evapotranspiration, and runoff affects the variations in soil moisture, which is of vital importance to agriculture. A systematic examination of climate change impacts on these variables may help provide scientific foundations for the design of relevant adaptation and mitigation measures. In this study, long-term variations in the water cycle over China are explored using the Regional Climate Model system (RegCM) developed by the International Centre for Theoretical Physics. Model performance is validated through comparing the simulation results with remote sensing data and gridded observations. The results show that RegCM can reasonably capture the spatial and seasonal variations in three dominant variables for the water cycle (i.e., precipitation, evapotranspiration, and runoff). Long-term projections of these three variables are developed by driving RegCM with boundary conditions of the Geophysical Fluid Dynamics Laboratory Earth System Model under the Representative Concentration Pathways (RCPs). The results show that increased annual average precipitation and evapotranspiration can be found in most parts of the domain, while a smaller part of the domain is projected with increased runoff. Statistically significant increasing trends (at a significant level of 0.05) can be detected for annual precipitation and evapotranspiration, which are 0.02 and 0.01 mm/day per decade, respectively, under RCP4.5 and are both 0.03 mm/day per decade under RCP8.5. There is no significant trend in future annual runoff anomalies. The variations in the three variables mainly occur in the wet season, in which precipitation and evapotranspiration increase and runoff decreases. The projected changes in precipitation minus evapotranspiration are larger than those in runoff, implying a possible decrease in soil moisture.

scholarly journals Aerosol Direct Radiative Effects over China Based on Long-Term Observations within the Sun–Sky Radiometer Observation Network (SONET)

2020 ◽  
Vol 12 (20) ◽  
pp. 3296
Author(s):  
Li Li ◽  
Zhengqiang Li ◽  
Kaitao Li ◽  
Yan Wang ◽  
Qingjiu Tian ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
The Sun ◽  
Radiative Effects ◽  
Observation Network ◽  
Fine Mode ◽  
Cooling Effects ◽  
Semi Arid

To investigate aerosol radiative effects, the Sun–Sky Radiometer Observation Network (SONET) has performed long-term observations of columnar atmospheric aerosol properties at 20 distributed stations around China. The aerosol direct radiative forcing (RF) and efficiency (RFE, the rate at which the atmosphere is forced per unit of aerosol optical depth) were estimated using radiative transfer model simulations based on the ground-based observations dating back to 2009. Results of multi-year monthly average RF illustrated that: the dust-dominant aerosol population at arid and semi-arid sites exerted moderate cooling effects (−8.0~−31.2 W/m2) at the top and bottom of atmosphere (TOA and BOA); RF at continental background site was very weak (−0.8~−2.9 W/m2); fine-mode dominant aerosols at urban and suburban sites exerted moderate cooling effects (−9.3~−24.1 W/m2) at TOA but more significant cooling effects (−19.4~−50.6 W/m2) at BOA; RF at coastal sites was comparable with values of urban sites (−5.5~−19.5 W/m2 at TOA, and −15.6~−44.6 W/m2 at BOA), owing to combined influences by marine and urban–industrial aerosols. Differences between RFE at TOA and BOA indicated that coarse-mode dominant aerosols at arid, semi-arid, and continental background sites were less efficient to warm the atmosphere; but fine-mode dominant aerosols at urban, suburban, and coastal sites were shown to be more efficient to heat the atmosphere.

scholarly journals Anthropogenic climate change has changed frequency of past flood during 2010-2013

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Yukiko Hirabayashi ◽  
Haireti Alifu ◽  
Dai Yamazaki ◽  
Yukiko Imada ◽  
Hideo Shiogama ◽  
...  
Keyword(s):  
Climate Change ◽  
South America ◽  
Radiative Forcing ◽  
Water Cycle ◽  
Flood Frequency ◽  
Anthropogenic Climate Change ◽  
Climate Change Signal ◽  
Northern Eurasia ◽  
Large Ensemble ◽  
The Impact

AbstractThe ongoing increases in anthropogenic radiative forcing have changed the global water cycle and are expected to lead to more intense precipitation extremes and associated floods. However, given the limitations of observations and model simulations, evidence of the impact of anthropogenic climate change on past extreme river discharge is scarce. Here, a large ensemble numerical simulation revealed that 64% (14 of 22 events) of floods analyzed during 2010-2013 were affected by anthropogenic climate change. Four flood events in Asia, Europe, and South America were enhanced within the 90% likelihood range. Of eight snow-induced floods analyzed, three were enhanced and four events were suppressed, indicating that the effects of climate change are more likely to be seen in the snow-induced floods. A global-scale analysis of flood frequency revealed that anthropogenic climate change enhanced the occurrence of floods during 2010-2013 in wide area of northern Eurasia, part of northwestern India, and central Africa, while suppressing the occurrence of floods in part of northeastern Eurasia, southern Africa, central to eastern North America and South America. Since the changes in the occurrence of flooding are the results of several hydrological processes, such as snow melt and changes in seasonal and extreme precipitation, and because a climate change signal is often not detectable from limited observation records, large ensemble discharge simulation provides insights into anthropogenic effects on past fluvial floods.

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