scholarly journals Tropospheric temperature variation over India and links with the Indian summer monsoon : 1971-2000

MAUSAM ◽  
2022 ◽  
Vol 53 (3) ◽  
pp. 289-308
Author(s):  
D. R. KOTHAWALE ◽  
K. RUPA KUMAR
Keyword(s):  
Summer Monsoon ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Temporal Variations ◽  
Mean Annual Temperature ◽  
Tropospheric Temperature ◽  
Temperature Variations ◽  
Annual Cycles ◽  
The Mean ◽  
Spatio Temporal

In the context of the ever increasing interest in the regional aspects of global warming, understanding the spatio-temporal variations of tropospheric temperature over India is of great importance. The present study, based on the data from 19 well distributed radiosonde stations for the period 1971-2000, examines the seasonal and annual mean temperature variations at the surface and five selected upper levels, viz., 850, 700, 500, 200 and 150 hPa. An attempt has also been made to bring out the association between tropospheric temperature variations over India and the summer monsoon variability, including the role of its major teleconnection parameter, the El Niño/Southern Oscillation (ENSO).   Seasonal and annual mean all-India temperature series are analyzed for surface and five tropospheric levels.  The mean annual cycles of temperature at different tropospheric levels indicate that the pre-monsoon season is slightly warmer than the monsoon season at the surface, 850 hPa and 150 hPa levels, while it is relatively cooler at all intermediate levels.  The mean annual temperature shows a warming of 0.18° C and 0.3° C per 10 years at the surface and 850 hPa, respectively.   Tropospheric temperature anomaly composites of excess (deficient) monsoon rainfall years show pronounced positive (negative) anomalies during the month of May, at all the levels.  The pre-monsoon pressure of Darwin has significant positive correlation with the monsoon temperature at the surface and 850 hPa.

scholarly journals Spatial Variations in the Diurnal Pattern of Precipitation over Nepal Himalayas

2015 ◽  
Vol 15 (2) ◽  
pp. 57-64 ◽  
Author(s):  
Dibas Shrestha ◽  
Rashila Deshar
Keyword(s):  
Summer Monsoon ◽  
Diurnal Cycle ◽  
Monsoon Season ◽  
Tropical Rainfall Measuring Mission ◽  
Early Morning ◽  
Temporal Variations ◽  
Diurnal Cycles ◽  
Diurnal Cycle Of Precipitation ◽  
Spatio Temporal ◽  
The Impact

The Central Himalayan Region (Nepal Himalayas), comprised of two clear sub-parallel mountain ranges, is atypical location for studying the impact of rugged topography on spatio temporal variations of precipitation. The relationship between topography and diurnal cycles of rainfall have been investigated utilizing 13-year (1998–2010) high resolution (0.05° × 0.05°) Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data. An investigation of diurnal cycle of precipitation revealed an afternoon maximum during the pre-monsoon season (March–May) and midnight–early morning maximum during the summer monsoon season (June–August)over the southern slopes of the Himalayas. The summer monsoon exhibited a robust spatial variation of diurnal cycle of precipitation, during afternoon-evening time, primary rainfall peak appeared along the Lesser Himalayas (~2,000–2,200 m above mean sea level), while early-morning rain in contrast showed maximum concentration along the southern margin of the Himalayas (~500–700 m above MSL). An afternoon-evening rainfall peak was attributed to higher rain frequency, whereas early-morning rainfall peak was attributed to fewer but rather intense rainfall. It is suggested that, confluence between down slope and moist south easterly monsoon flow triggers convection near the foothills of the Himalayas during early morning period. The results further suggested the morning precipitation moves southward in the mature monsoon season.DOI: http://dx.doi.org/njst.v15i2.12116Nepal Journal of Science and Technology Vol. 15, No.2 (2014), 57-64

scholarly journals Spatio-temporal variations of land surface temperature and precipitation due to climate change in the Jhelum river basin, India

MAUSAM ◽  
2021 ◽  
Vol 71 (4) ◽  
pp. 661-674
Author(s):  
HIMAYOUN DAR ◽  
ROSHNI THENDIYATH ◽  
MOHSIN FAROOQ
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
21St Century ◽  
Temporal Variations ◽  
Average Increase ◽  
Temperature And Precipitation ◽  
Rcp 8.5 ◽  
The Mean ◽  
Spatio Temporal ◽  
Precipitation And Temperature

The present study investigated the spatio-temporal variations of precipitation and temperature for the projected period (2011-2100) in the Jhelum basin, India. The precipitation and temperature variables are projected under RCP 8.5 scenario using statistical down scaling techniques such as Artificial Neural Network (ANN) and Wavelet Artificial Neural Network (WANN) models. Firstly, the screened predictors were downscaled to predictand using ANN and WANN models for all the study stations. On the basis of the performance criteria, the WANN model is selected as an efficient model for downscaling of precipitation and temperature. The future screened predictor data pertaining to RCP 8.5 of CanESM2 model were downscaled to monthly temperature and precipitation for future periods (2011-2100) using WANN models. The investigation of the future projections revealed an average increase of 17-25% in the mean annual precipitation and 20-25% average increase in the monthly mean precipitation for all the selected stations towards the end of 21st century. The monthly mean temperature also showed an increase of 2-3 °C for all the study stations towards the end of 21st century. The mean seasonal temperature of the projected period is found to be increasing for all the four seasons in most parts of the basin.

scholarly journals Evolutions of sea level high and warm pool in the southeastern Arabian Sea and their association with Asian monsoons : A study on cause-and-effect relationships

MAUSAM ◽  
2021 ◽  
Vol 59 (1) ◽  
pp. 87-94
Author(s):  
O. P. SINGH
Keyword(s):  
Sea Level ◽  
Summer Monsoon ◽  
El Niño ◽  
Arabian Sea ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Warm Pool ◽  
Sea Surface ◽  
Southeastern Arabian Sea

The present study aims at gaining more insight into the evolution of warm pool and associated sea level dome in the southeastern Arabian Sea before the summer monsoon onset.  The results show that the Sea Surface Temperature (SST) maximum in the warm pool region is found during April close to the southwest coast of India.  The Sea Surface Height (SSH) maximum over the same region is observed during December. The collapse of sea level dome begins well in advance during the pre-monsoon whereas the warm pool collapses after the onset of summer monsoon during June.  Therefore, there is a lag of about three to four months between the collapses of the sea level high and the warm pool.  Most interesting aspect is the dramatic increase of SST from September and SSH from October which is continued throughout the post monsoon season (October - December). Therefore, both the collapse and evolution of warm pool are dramatic events before and after the summer monsoon.                    There are considerable variations in the intensity of warm pool and the height of sea level dome on interannual scale.  The variation during El-Nino Southern Oscillation (ENSO) epoch of 1987-88 has revealed many interesting features.  During El-Nino year 1987 the warm pool intensity reached its peak in June whereas during La Nina year 1988 the warm pool attained its maximum intensity much earlier, i.e., in April. 

scholarly journals Influence of Asian Summer Monsoon Anticyclone on the Trace gases and Aerosols over Indian region

2019 ◽  
Author(s):  
Ghouse Basha ◽  
M. Venkat Ratnam ◽  
Pangaluru Kishore ◽  
S. Ravindrababu ◽  
Isabella Velicogna
Keyword(s):  
Summer Monsoon ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Trace Gases ◽  
La Niña ◽  
La Nina ◽  
Asian Summer

Abstract. The Asian Summer Monsoon Anticyclone (ASMA) persisting during monsoon season in the upper troposphere and lower stratosphere (UTLS) region play an important role in confining the trace gases and aerosols for a longer period thus affects regional and global climate. Our understanding on these trace gases and aerosols variability in the ASMA is limited. In this study, the effect of the ASMA on the trace gases (Water Vapour (WV), Ozone (O3), Carbon Monoxide (CO)) and aerosols (Attenuated Scattering Ratio (ASR)) obtained from long-term (2006–2016) satellite measurements is investigated. Since the ASMA is present in the UTLS region, its influence on the tropopause characteristics is also explored. Higher tropopause altitude, WV, CO and ASR confining to the ASMA region is observed, whereas tropopause temperatures and O3 are found low. There exists large inter-annual variation in the ASMA and hence its effect on these trace gases and aerosols are also seen clearly. A significant relationship is also observed between the phases of Quasi-Biannual Oscillation (QBO) and El Niño Southern Oscillation (ENSO) on the trace gases and ASR, including the tropopause when measurements in the ASMA region are subject to multivariate regression analysis. Further, the influence of the Indian summer monsoon (ISM) activity on the ASMA trace gases and aerosols is studied with respect to active and break spells of monsoon, strong and weak monsoon years, strong La Niña, El Niño years. Results show a significant increase in WV, CO and decrease in O3 during the active phase of the ISM, strong monsoon years and strong La Niña years in the ASMA. Enhancement in the ASR values during the strong monsoon years and strong La Niña years is observed. Thus, it is prudent to conclude that the dynamics of the ASMA play an important role in the confinement of several trace gases and aerosols and suggested to consider the activity of summer monsoon while dealing with them at sub-seasonal scales.

Dynamics of Maximum Snow Cover Area and Snow Line Altitude Across Nepal (2003-2018) Using Improved MODIS Data

2020 ◽  
Vol 25 (2) ◽  
pp. 17-24
Author(s):  
Nitesh Khadka ◽  
Nitesh Khadka ◽  
Shravan Kumar Ghimire ◽  
Xiaoqing Chen ◽  
Sudeep Thakuri ◽  
...  
Keyword(s):  
Snow Cover ◽  
Monsoon Season ◽  
Temporal Variations ◽  
Vital Role ◽  
Eastern Region ◽  
Snow Cover Area ◽  
Post Monsoon ◽  
Snow Line ◽  
Elevation Zone ◽  
Spatio Temporal

Snow is one of the main components of the cryosphere and plays a vital role in the hydrology and regulating climate. This study presents the dynamics of maximum snow cover area (SCA) and snow line altitude (SLA) across the Western, Central, and Eastern Nepal using improved Moderate Resolution Imaging Spectroradiometer (MODIS; 500 m) data from 2003 to 2018. The results showed a heterogeneous behavior of the spatial and temporal variations of SCA in different months, seasons, and elevation zones across three regions of Nepal. Further, the maximum and minimum SCA was observed in winter (December-February) and post-monsoon (October-November) seasons, respectively. The inter-annual variation of winter SCA showed an overall negative trend of SCA between 2003 to 2018 at the national and regional scales. The SLA was assessed in the post-monsoon season. At the national scale, the SLA lies in an elevation zone of 4500-5000 m, and the approximate SLA of Nepal was 4750 m in 2018. Regionally, the SLA lies in an elevation zone of 4500-5000 m in the Western and Central regions (approx. SLA at 4750 m) and 5000-5500 m in the Eastern region (approx. SLA at 5250 m) in 2018. The SLA fluctuated with the changes in SCA, and the spatio-temporal variations of SLAs were observed in three regions of Nepal. We observed an upward shift of SLA by 33.3 m yr-1 in the Western and Central Nepal and by 66.7 m yr-1 in Eastern Nepal. This study will help to understand the impacts of climate change on snow cover, and the information will be useful for the hydrologist and water resource managers.

Implications of methane emissions in biogeochemical budgeting: A study from a eutrophic tropical lake of South India

2020 ◽  
Author(s):  
Revathy Das ◽  
Appukuttan Pillai Krishnakumar ◽  
Krishnan AnoopKrishnan ◽  
Vivekanandan Nandakumar
Keyword(s):  
Plant Biomass ◽  
Regional Scale ◽  
Temporal Variations ◽  
Physical Factors ◽  
Growing Seasons ◽  
Littoral Zones ◽  
Flux Measurements ◽  
The Mean ◽  
Spatio Temporal ◽  
Lake Systems

<p>Greenhouse gases (GHGs), especially, methane (CH<sub>4</sub>) emissions from the littoral zones of the lakes play an important role in regional biogeochemical budgets. Only a few studies are available in literature highlighting the direct flux measurements of CH<sub>4   </sub>from the aquatic systems. In the present study, an attempt has been made to quantify the spatio-temporal variations of CH<sub>4</sub> efflux and the key physical factors controlling the emission rate, from the vegetated littoral zones of lake Vellayani (5.55Km<sup>2</sup>), located in the urbanized area of Thiruvananthapuram city, Kerala, South-West India. CH<sub>4</sub> efflux were collected from different vegetations in littoral zones, using a static chamber, during the peak growing seasons from March to October in 2016 and further analyses were carried out by using Gas Chromatograph (PE Clarus 500, PerkinElmer, Inc.). The mean efflux rate of CH<sub>4   </sub>from the emergent plant species (Phragmites australis and Typha spp.) was 114.4 mg CH<sub>4</sub> m<sup>-2</sup>h<sup>-1</sup>; while, in the floating leaved species (Nymphaea spp. and Nelumbo Spp.), it <sub>  </sub>was   observed to be 32.6 mgCH<sub>4</sub> m<sup>-2</sup>h<sup>-1</sup>. The results reveal that CH<sub>4</sub> efflux in the zone of emergent vegetation was significantly higher than the floating-leaved zone indicating the importance of plant biomass and standing water depths for the spatial variations of CH<sub>4 </sub>efflux. However, no significant temporal variations were noticed in the physical factors during the peak growing seasons. These results indicate that the vegetated littoral zones of lake, especially the emergent plant zones were supersaturated with CH<sub>4</sub>, facilitating the production of carbon for CH<sub>4</sub> emission<sub>,</sub> but also enable the release of CH<sub>4 </sub>by the diffusion from the intercellular gas lacunas. We conclude that the atmospheric CH<sub>4</sub> emissions will be affected by the growth of exotic species in the lake systems and may be the reason for enhancing the climate warming in local/regional scale.</p>

scholarly journals Spatial distribution of temperature during geomagnetic disturbances

2018 ◽  
Vol 4 (4) ◽  
pp. 59-62 ◽  
Author(s):  
Ашхен Караханян ◽  
Ashhen Karakhanyan ◽  
Сергей Молодых ◽  
Sergey Molodykh
Keyword(s):  
Solar Activity ◽  
Geomagnetic Activity ◽  
Lower Troposphere ◽  
Temporal Analysis ◽  
Reanalysis Data ◽  
Tropospheric Temperature ◽  
Geomagnetic Disturbances ◽  
Temperature Variations ◽  
Activity Effect ◽  
Spatio Temporal

We propose an index of efficiency of the solar activity effect on the tropospheric temperature, which takes into account the spatial irregularity of the response to this effect. As a proxy of solar activity we take the PC index of geomagnetic activity, designed to monitor the geomagnetic field at high latitudes. Using NCEP/NCAR reanalysis data, we carry out a comparative analysis of variations in the proposed index and lower-troposphere temperature variations during geomagnetic disturbances. We identify the presence of a high degree of correlation between the temperature in the 925–700 hPa layer and the proposed index of solar activity effect. The spatio-temporal analysis of the index and temperature variations shows that the index of effi-ciency of the solar activity effect describes well both the value and the sign of the observed variations in the spa-tial distribution of the lower-troposphere temperature as compared to the frequently used index of geomagnetic activity.

scholarly journals Hydrologic processes of groundwater in a small monsoon-influenced mountainous watershed

2018 ◽  
Vol 49 (6) ◽  
pp. 2016-2029 ◽  
Author(s):  
Ruiqiang Yuan ◽  
Shiqin Wang ◽  
Lihu Yang ◽  
Jianrong Liu ◽  
Peng Wang ◽  
...  
Keyword(s):  
Water Table ◽  
Northern China ◽  
Temporal Variations ◽  
Hydrologic Processes ◽  
Mountain Valley ◽  
Mountain Watersheds ◽  
Mountainous Watershed ◽  
The Mean ◽  
Spatio Temporal ◽  
In The Beginning

Abstract Mountain block recharge is the least well quantified owing to the lack of a thorough understanding of mountain block hydrological processes. Observations of spatio-temporal variations of groundwater were employed to clarify hydrologic processes in a semi-arid mountainous watershed of northern China. Results showed that the annual feeding rate of precipitation changed between 21% and 40%. However, infiltration of precipitation was mainly drained as interflow on slopes and recharged into the mountain valley as focused recharge. As a result, the mean correlation coefficient between precipitation and groundwater level was only 0.20 and seasonal variations were reduced. Mountain slope is essentially impermeable with no bedrock percolation under arid circumstances. Only a bedrock percolation event occurred after multiple closely-spaced heavy rains during the four-year observation, which induced a local rapid ascending of the water table and an enhanced lateral recharge from upgradient watersheds. The influence of the enhanced lateral recharge lasted three years, suggesting a huge groundwater catchment overcoming local watershed divides in mountain blocks. The average of the gradual recession of the water table was 5.1 mm/d with a maximum of 11.4 mm/d in the beginning stage. Both interflow and bedrock percolation are important. Our results highlight the changeability of hydrologic processes in mountain watersheds.

Analysis of Extreme Temperature Events in North China Based on EMD Method

2013 ◽  
Vol 295-298 ◽  
pp. 854-858 ◽  
Author(s):  
Xiao Ying Chen ◽  
Yi Min Zhu ◽  
Lin Lin Xia ◽  
Wei Xing Zhang
Keyword(s):  
High Temperature ◽  
Temperature Variation ◽  
North China ◽  
Southern Oscillation ◽  
Extreme Temperature ◽  
Temporal Variations ◽  
Mode Decomposition ◽  
Extreme High Temperature ◽  
Spatio Temporal ◽  
Emd Method

The spatio-temporal variations of extreme temperature in North China during 1954-2008 are analyzed based on Empirical Mode Decomposition (EMD) method. The results show that the interannual-to-interdecadal variabilities of extreme temperature in North China. 3-4 years and 7-8 years interannual variabilities as well as a decreasing trend are dominant while 15 years oscillation takes second place in the extreme low temperature variation. Meanwhile, 3-4 year interannual variabilities are dominant while 6-7 years, 14-15 years 40 years oscillation as well as an increasing trend takes second place in the extreme high temperature variation. 3-4 years interannual variabilities of both extreme low and high temperature are closely related to El Nino-Southern Oscillation (ENSO), while interdecadal variabilities and trend of extreme temperature are obviously associated with the Pacific Decadal Oscillation (PDO). Besides, PDO plays an important role on interdecadal modulation of interannual to decadal variabilities of extreme temperature in North China.

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