Remote Sensing-Based Assessment of the Variability of Winter and Summer Precipitation in the Pamirs and Their Effects on Hydrology and Hazards Using Harmonic Time Series Analysis

Abstract

Moisture supply in the Pamir Mountains of Central Asia significantly determines the hydrological cycle and, as a result, impacts the local communities via hazards or socioeconomic aspects, such as hydropower, agriculture and infrastructure. Scarce and unreliable in situ data prevent an accurate assessment of moisture supply, as well as its temporal and spatial variability in this strongly-heterogeneous environment. On the other hand, a clear understanding of climatic and surface processes is required in order to assess water resources and natural hazards. We propose to evaluate the potential of remote sensing and regional climate model (RCM) data to overcome such issues. Difficulties arise for the direct analysis of precipitation if the events are sporadic and when the amounts are low. We hence apply a harmonic time series analysis (HANTS) algorithm to derive spatio-temporal precipitation distributions and to determine regional boundaries delimiting areas where winter or summer precipitation dominate moisture supply. We complement the study with remote sensing-based products, such as temperature, snow cover and liquid water equivalent thickness. We find a strong intra-and inter-annual variability of meteorological parameters that result in strongly variable water budget and water mobilization. Climatic variability and its effects on floods and droughts are discussed for three outstanding years. The in-house Remote Sens. 2015, 7 9728 developed HANTS toolbox is a promising instrument to unravel periodic signals in remote sensing time series, even in complex areas, such as the Pamir.

Glacier melt buffers river runoff in the Pamir Mountains

“…Glaciological studies generally reported glacier retreat or glacier mass loss in the greater Pamir region [ Kääb et al ., ; Sorg et al ., ; Lutz et al ., ; Bolch et al ., ] although parts in the Pamir and the Karakoram display slight mass gain [ Gardelle et al ., ]. The spatial heterogeneity in glacier evolution in the Pamir is partly inherent from precipitation gradients and seasonality [ Fuchs et al ., ; Pohl et al ., ] although this does not account for short‐term local meteorological conditions that can play a crucial role [ Mölg et al ., ; Liu et al ., ; Khromova et al ., ]. This is important to note because the assessment of glacier evolution is often based on very few observations due to the limited availability of adequate remote sensing products.…”

Sensitivity analysis and implications for surface processes from a hydrological modelling approach in the Gunt catchment, high Pamir Mountains

“…2). Pohl et al (2015) show complex effects of weather variability on water availability and storage in the greater Pamir region. The complexity results from the interplay of temperature, precipitation amounts and timings, and resulting snow cover.…”

Bridging Glaciological and Hydrological Trends in the Pamir Mountains, Central Asia

“…The eastern part of the River Gunt catchment spans over the dry plateau of the Tajik East Pamirs, adjacent to the above-mentioned "meteorological anomaly". The western part of the catchment can be seen as predominately westerly-influenced [43]. The same is true for the Bartang River basin north of the Gunt basin, which drains the entire Tajik South-East Pamirs before receiving the meltwaters of the Central Pamirs and the southern drainage of the Fedchenko area.…”

“…This glacio-nival dry climate is induced by westerlies-dominated moisture supply, which causes a precipitation gradient from high values in the North-West Pamir to the lowest values in the East Pamirs [42]. The arid South-East Pamirs (north of the Karakoram) are characterized by a precipitation maximum in summer, whose potential origin is the subject of controversial discussions [20,43,44]. Precipitation in the East Pamirs is said to increase (seen in Global Precipitation Climatology Project (GPCP) data [4]) and expected to trigger glacial mass gain from the West Kunlun Shan up to the Pamirs [20].…”

“…This water supply is endangered by the absence of glacier meltwater during the ablation period, which is the main growing season. In August and September, the basin hardly receives any rainfall, and snow cover has already disappeared (Pohl et al [32,43]). The contribution of glacier retreat to river runoff is relatively smaller in western subbasins ( Figure 2E).…”