Temperature and precipitation changes over the glaciated parts of Indian Himalayan Region during 1901-2016

摘要

The existing knowledge on long-term climate trends over glaciated parts of Indian Himalayan Region (IHR) is limited. The present study aims at assessing the long-term (1901-2016) as well as the recent (1990-2016) temperature and precipitation trends over the glaciated parts of western (WH), central (CH) and eastern Himalaya (EH) within the IHR using Climate Research Unit Time Series version 4.01 (CRU TS4.01) data. Mann-Kendall and Sen's slope estimator tests were employed to determine the monotonic trend direction and magnitude of change over time on annual and seasonal basis. The temperature and precipitation trends were quantitatively assessed here in terms of percent change over mean as well as in absolute terms. Results show that annual average temperature remains 0 degrees C in WH (2.26 degrees C) and CH (3.24 degrees C) but 0 degrees C in EH (-0.97 degrees C). Long-term analysis (1901-2016) reveals the maximum warming in EH (74.67% or 0.93 degrees C) followed by WH (52.56% or 0.64 degrees C) and minimum in CH (44.31% or 0.73 degrees C). The winter warming is notably higher (WH: 1.11 degrees C, CH: 1.19 degrees C and EH: 1.41 degrees C) than the summer (WH: 0.31 degrees C, CH: 0.26 degrees C and EH: 0.54 degrees C). Annual precipitation gradually increases from WH (535.57 mm) to CH (749.91 mm) to EH (1249.49 mm), of which 68%, 76%, and 90% respectively, are summer-induced. Nevertheless, precipitation showed no clear trend in WH (slight increase of 4.53%) and EH (slight decrease of -5.30%), but a clear reduction in CH (-19.25%). Seasonally, precipitation decreased in winter (-4.53%) but increased in summer (10.65%) in WH, clearly decreased in both winter (-24.69%) and summer (-17.01%) in CH, and slightly increased in winter (2.21%) but decreased in summer (-6.80%) in EH. In recent decades (1990-2016), warming trend further accelerated in WH (0.95 degrees C) and CH (1.01 degrees C) but decreased in EH (0.60 degrees C). The overall precipitation trends also changed during 1990-2016 as WH experienced an overall reduction (-5%), CH maintained a declining trend (-13.10%), and EH showed slight increase (1.01%). The study concludes that the climate of glaciated parts has changed significantly, but the trend and magnitude is highly heterogeneous over different regions which likely influenced the glaciated environment.