Land–Boundary Layer–Sea Interactions in the Middle East
Author(s)
Giannakopoulou, Evangelia Maria
Type
Thesis or dissertation
Abstract
Understanding the land–boundary layer–sea interactions is a primary target both in the
context of low-level jet (LLJ) development and landscape alterations. This thesis attempts
to address and study these interactions in the Middle East.
The thesis investigates the summertime LLJ over the Persian Gulf, known as the
Shamal. Terrain height, land-sea and novel mountain slope sensitivity experiments were
conducted and compared with a control run. It was found that the Weather Research and
Forecasting (WRF) model accurately simulates the LLJ’s vertical structure, nocturnal
features and strong diurnal oscillation of the wind, and that orography, mountain slope
and land/sea breezes determine the Shamal diurnal variation of wind speed and wind
direction. The Iranian mountain range not only channels the northwesterly winds but
also provides a barrier for the easterly monsoon airflow. The steep slopes cause increased
wind speeds; however, the shallow slopes reveal a stronger diurnally varying wind direction
due to larger diurnal heating of the sloping terrain. The land breeze and the lower friction
over the sea increase the intensity of the nocturnal jet over the Gulf.
To determine the effects of the Nile Delta man-induced greening on local climate, the
WRF model was used to compare control simulations, which employ the present-day Nile
Delta landscape, with desertification experiments in which the Nile Delta is replaced by
desert. It was found that the low surface albedo of the present-day agricultural Nile
Delta increases net radiation, which in turn raises potential evapotranspiration (PET).
This suggests that agricultural use increases the water demand by enhancing PET. Non-local
effects were also examined. It was found that a frontal system over the eastern
Mediterranean Sea, associated with a storm event, is shifted farther away from the coast.
This shift is attributed to a stronger land breeze in the present-day land-cover.
context of low-level jet (LLJ) development and landscape alterations. This thesis attempts
to address and study these interactions in the Middle East.
The thesis investigates the summertime LLJ over the Persian Gulf, known as the
Shamal. Terrain height, land-sea and novel mountain slope sensitivity experiments were
conducted and compared with a control run. It was found that the Weather Research and
Forecasting (WRF) model accurately simulates the LLJ’s vertical structure, nocturnal
features and strong diurnal oscillation of the wind, and that orography, mountain slope
and land/sea breezes determine the Shamal diurnal variation of wind speed and wind
direction. The Iranian mountain range not only channels the northwesterly winds but
also provides a barrier for the easterly monsoon airflow. The steep slopes cause increased
wind speeds; however, the shallow slopes reveal a stronger diurnally varying wind direction
due to larger diurnal heating of the sloping terrain. The land breeze and the lower friction
over the sea increase the intensity of the nocturnal jet over the Gulf.
To determine the effects of the Nile Delta man-induced greening on local climate, the
WRF model was used to compare control simulations, which employ the present-day Nile
Delta landscape, with desertification experiments in which the Nile Delta is replaced by
desert. It was found that the low surface albedo of the present-day agricultural Nile
Delta increases net radiation, which in turn raises potential evapotranspiration (PET).
This suggests that agricultural use increases the water demand by enhancing PET. Non-local
effects were also examined. It was found that a frontal system over the eastern
Mediterranean Sea, associated with a storm event, is shifted farther away from the coast.
This shift is attributed to a stronger land breeze in the present-day land-cover.
Date Issued
2012-10
Date Awarded
2012-11
Advisor
Toumi, Ralf
Sponsor
Open Air Laboratories (OPAL)
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)