An Apparent Relationship between Eurasian Spring Snow Cover and the Advance Period of the Indian Summer Monsoon

1982 ◽  
Vol 21 (12) ◽  
pp. 1929-1932 ◽  
Author(s):  
B. Dey ◽  
O. S. R. U. Bhanu Kumar
2017 ◽  
Vol 30 (4) ◽  
pp. 1273-1289 ◽  
Author(s):  
Subhadeep Halder ◽  
Paul A. Dirmeyer

Abstract This observationally based study demonstrates the importance of the delayed hydrological response of snow cover and snowmelt over the Eurasian region and Tibet for variability of Indian summer monsoon rainfall during the first two months after onset. Using snow cover fraction and snow water equivalent data during 1967–2003, it is demonstrated that, although the snow-albedo effect is prevalent over western Eurasia, the delayed hydrological effect is strong and persistent over the eastern part. Long soil moisture memory and strong sensitivity of surface fluxes to soil moisture variations over eastern Asia and Tibet provide a mechanism for soil moisture anomalies generated by anomalies in winter and spring snowfall to affect rainfall during the initial months in summer. Dry soil moisture anomalies over the eastern Eurasian region associated with anomalous heating at the surface and midtroposphere help in anchoring of an anomalous upper-tropospheric “blocking” ridge around 100°E and its persistence. This not only leads to prolonged weakening of the subtropical westerly jet but also shifts its position southward of 30°N, followed by penetration of anomalous troughs in the westerlies into the Indian region. Simultaneously, intrusion of cold and dry air from the midlatitudes can reduce the convective instability and hence rainfall over India after the onset. Such a southward shift of the jet can also significantly weaken the vertical easterly wind shear over the Indian region in summer and lead to decrease in rainfall. This delayed hydrological effect also has the potential to modulate the snow–atmosphere coupling strength for temperature and precipitation in operational forecast models through soil moisture–evaporation–precipitation feedbacks.


2021 ◽  
Author(s):  
Amit Kumar ◽  
Akshaya Verma ◽  
Sameer K Tiwari ◽  
Santosh K Rai

<p>Glaciers in the Indian Himalayan Region (IHR) are sensitive to climatic changes. Rivers originating from Himalaya have higher water yields in the ablation season due to large inputs from the melting of snow and glaciers, which is critical for sustaining downstream ecosystem, agricultural practices, hydroelectric power generation, and urban water supplies. Integrated investigations are frequently unavailable at a regional scale over a longer period, which is hampered due to the non-availability of data caused by harsh weather conditions, difficult terrain, as well as difficulty in maintaining the instruments at such high altitudes (> 3000 m asl). The hydrological understanding of melting processes from glacierized basins requires a network of reliable meteorological and hydrological observations. In absence of such reliable meteorological data, most of the hydrological simulation studies are forced to extrapolate air temperature from nearby basins, lower elevations, or consider satellite-based observations, which often deviate or differ from the actual ground conditions and lead to large uncertainty in model outputs. Therefore, an integrated approach for collecting hydrological and meteorological data along with other data like snow-cover, suspended sediment transfer and stable isotopic signatures of different components of the hydrograph were conceptualized for glacierized river basins in Garhwal Himalaya (Bhagirathi and Alaknanda). Our results suggest that the annual distribution of temperature lapse rates (TLR) established exhibits a bimodal pattern and the TLR’s are significantly lower than the adiabatic lapse rate. The major components of the streamflow are derived from snow and glacier melt, while rainfall contributes little during the Indian Summer Monsoon (ISM). Westerlies significantly feed the glacier with snow, while rainfall is dominant during the Indian Summer Monsoon (ISM). Precipitation and temperature are the dominant meteorological factors controlling melting processes and sediment delivery. Climate and topography control the distribution of seasonal snow cover/ snowline in the region. Extreme events like heavy rainfall, flash floods, glacial lake outbursts floods, etc. can be traced using hydrometeorological and isotopic data at high altitude stations. Therefore, in light of the challenges and potential research gaps, the study produces actionable knowledge in the Garhwal Himalaya for better understanding and modeling of glacio-hydrological processes by incorporating ground-based observations.</p>


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