Projekttr?ger: Universit?t Augsburg

Projektverantwortung vor Ort: M.Sc. Mohammad Saleem Pomee, Prof. Dr. Elke Hertig

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The mountain ranges of Hindukush, Karakoram and Himalayans (HKH) contain the largest glaciers outside the Polar Regions and are often termed the “Third Pole” of the earth. The HKH regional climate is characterized by western disturbances (winter), Indian summer monsoon (summer) and transition between these two synoptic modes. Complex interactions between synoptic-scale circulations, cryosphere, hydrosphere and steep topographic features largely govern regional precipitation, which varies significantly with time and altitudes. The Indus River originates within HKH region, traverses nearly 3,200 kilometer before descending into the Arabian Sea and sustains the livelihood of millions of downstream people by providing freshwater, energy, food security and other eco-services. The upper Indus basin (UIB) located within HKH region primarily controls the hydrological regime of the Indus river system through a combination of rainfall and melting of seasonal and permanent snowfields. In contrast, the Lower Indus (LI) has arid to semi-arid climate and depends heavily on water supply from UIB to meet the water demand for the largest contiguous irrigation system in the world.

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Considering climate hotspot nature of this basin, an assessment of future water availability is of utmost importance. Modeling precipitation and temperature within cryosphere-dominated water supply (i.e. UIB) and demand (LI) regions of the Indus basin under future radiative forcing is fundamental in this regard. However, the available observational network, particularly within complex UIB, does not provide reliable, adequate and consistent data to model effectively the orographic structure of regional climate that largely governs the basin hydrology. Given further the ineffectiveness of various gridded products (de facto observational proxies), a reliable precipitation modeling constitutes a major scientific challenge.

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Due to such an incomplete in situ observational profile even the mean direction of the regional climate change signal is highly controversial and ranges from rapid retreat of glaciers to the so-called “Karakoram anomaly” that involves rather a buildup of glacial mass balance. While the provision of additional useful data is still an ongoing process, improvement in simulation methodologies to exploit the available observational profile still offer some opportunities to reduce associated uncertainties.

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With this background, the current PhD study aims to model future precipitation and temperature changes (both Tmax and Tmin are modeled due to their impact on melt rate and type of precipitation) over Indus basin of Pakistan by analyzing observed precipitation variability over seasons, regions and altitudes. The modeling approach involves the use of large- and medium-scale atmospheric circulations in simulations that have been least explored in this basin. Circulation analysis can additionally explain governing mechanisms to strengthen confidence in simulation results. Given the complex nature of our study region, uncertainties of observations, reanalysis and GCM data are also regarded to assess the reliability of the simulations. The future precipitation and temperature changes derived from such statistically skillful and physically consistent models may provide realistic feedback to support climate-smart water management at basin scale.