Abstract
The climatology of major sources and pathways of moisture for three locales along the Hindu-Kush-Himalayan region are examined, by use of Lagrangian methods applied to the ERA-Interim dataset, over the period from 1980 to 2016 for both summer (JJA) and winter (NDJ) periods. We also investigate the major flooding events of 2010, 2013, and 2017 in Pakistan, Uttarakhand, and Kathmandu, respectively, and analyse a subset of the climatology associated with the 20 most significant rainfall events over each region of interest. A comparison is made between the climatology and extreme events, in the three regions of interest, during the summer monsoon period. For Northern Pakistan and Uttarakhand, the Indus basin plays the largest role in moisture uptake. Moisture is also gathered from Eastern Europe and Russia. Extreme events display an increased influence of sub-tropical weather systems, which manifest themselves through low-level moisture transport; predominantly from the Arabian sea and along the Gangetic plain. In the Kathmandu region, it is found that the major moisture sources come from the Gangetic plain, Arabian Sea, Red Sea, Bay of Bengal, and the Indus basin. In this case, extreme event pathways largely match those of the climatology, although an increased number of parcels originate from the western end of the Gangetic plain. These results provide insights into the rather significant influence of mid-latitudinal weather systems, even during the monsoon season, in defining the climatology of the Hindu-Kush-Himalaya region, as well as how extreme precipitation events in this region represent atypical moisture pathways. We propose a detailed investigation of how such water pathways are represented in climate models for the present climate conditions and in future climate scenarios, as this may be extremely relevant for understanding the impacts of climate change on the cryosphere and hydrosphere of the region.
Highlights
The mountainous regions of the Hindu-Kush-Karakoram-Himalaya (HKKH) contain nearly km3 of ice, which is the third largest mass of ice on Earth, with only Antarctica and the Arctic/Greenland supporting more
The above findings agree with those of [21,23,58,59], showing the key characteristic which led to these extreme events was a result of atypical coupling between mid-latitudinal and monsoonal weather systems, which was realised through the convergence of fast-moving, low-level air from the northwest and low-level moist air from the south-east against the mountainous orography, which resulted in strong updrafts, driving the observed extreme precipitation events
Here, that the moist parcels which travelled over the Arabian Sea and the Indian subcontinent to Northern Pakistan (NP) and U were anomalously low in the troposphere during these extreme events, meaning these parcels were in a state receptive to moisture accumulation and resistant to precipitation
Summary
The mountainous regions of the Hindu-Kush-Karakoram-Himalaya (HKKH) contain nearly km of ice, which is the third largest mass of ice on Earth, with only Antarctica and the Arctic/Greenland supporting more. In addition to the socio-economic issues to habitability caused by long-term climatological changes, extreme hydrological events, such as floods and droughts, which occur due to large excesses or deficiencies in localised precipitation, often lead to a massive loss of lives as well as livelihoods; consider, the non-trivial impacts of changes in the hydroclimate (and, especially, in its extreme events) of mountainous regions on the advent of landslides [18,19]. We analyse a subset of the climatology containing the 20 most significant extreme precipitation events to hit each of our regions of interest and compare the differences in the moisture pathways and sources to the overall climatology and the case studies.
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