Impact Assessment of Orography on the Extreme Precipitation Event of July 2010 over Pakistan: A Numerical Study

Abstract

The topography influences monsoon precipitation and gives rise to significant rainfall events in South Asia. The physical mechanism involved in such events includes mechanical uplifting, thermodynamics, small scale cloud processes, and large scale atmospheric circulations. The investigation into orographic precipitation is pursued by synoptic and model analysis. Deep convection occurs as warm moist airflow is channeling over steep mountains. WRF model coupled with Morrison double moment scheme is used to assess the relative impact of topography on extreme rainfall event of 26–30 July 2010 in Pakistan. Two sensitivity tests with full topography (CTL) and reduced topography by 50% (LOW) are carried out. Two distinct precipitation zones over Hindukush and Himalaya mountains are identified. The topographic changes significantly affect moisture divergence and spatial and temporal distribution of precipitation. A low level jet is created on windward side of big mountains, yielding enhanced moisture flux and instability. Eddy kinetic energy significantly changes with orographic height. Energy flux created further unstabilized atmosphere and deep convection, producing wide spread heavy rainfall in the area in Himalaya foothills. Under the set synoptic conditions, orographic orientation enhanced the moisture accumulation and deep convection, resulting in occurrence of this extreme event.

Late-Spring Severe Blizzard Events over Eastern Romania: A Conceptual Model of Development

“…Studies that have highlighted the role of synoptic-local scale interaction in amplifying the extreme events were made for Europe and beyond, too. Apart from the influence of the sea surface temperature (e.g., [27,28]), studies have also focused on the role of orography (including the Carpathian mountains) in the distribution and intensity of precipitation [29][30][31]. Such studies are important in identifying how atmospheric dynamical and thermodynamical processes interact with the particularities of the topography of each region and, as far as possible, in improving the forecast model output.…”

Climate Change and its Effects on Pakistan

“…The findings address a major shift in precipitation patterns in Pakistan as a result of the intensity of heavy rainfall events during monsoon seasons. The heavy rainfall events are resulting in flash floods and associated destructions (Muhammad Tahir et al, 2015) Other related repercussions include damage to cropping and low productivity, water stress, disruption in cultivation, damage to infrastructure, and other long-term socio-economic ramifications.…”

“…The analysis highlights the sea-level rise as a major threat to the coastal regions in the country. The erosion, saltwater intrusion, and coastal flooding are observed consequences, affecting coastal communities, infrastructure, and livelihoods (Muhammad Tahir et al, 2015). Therefore, the increasing vulnerability of coastal regions in Pakistan due to extreme weather events is placing significant economic challenges and social burdens that would affect the community in the long run.…”

“…The weather changes also alter the monsoon season. It can be witnessed by the increased frequency of heavy rainfalls and severe floods (Muhammad Tahir et al, 2015) The rapid melting of glaciers in the mountain ranges such as the Karakoram range and the Hindu Kush has threatened the country's water resources. Though glaciers provide natural reservoirs, and supply fresh water through rivers used for agriculture and hydropower generation (Rehman et al, 2021).…”

As chuvas de relevo: a influência da serra de Itaqueri nos acumulados pluviométricos regionais

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