Date of Award
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Atmospheric and Earth Science
Committee Chair
Udaysankar Nair
Committee Member
Timothy J. Lang
Committee Member
Larry Carey
Committee Member
John R. Mecikalski
Committee Member
Themistoklis Chronis
Research Advisor
Udaysankar Nair
Subject(s)
Convection (Meteorology), Ocean-atmosphere interaction, Land use--Environmental aspects--Indonesia--Java, Land cover--Environmental aspects--Indonesia--Java
Abstract
In the Maritime Continent (MC), sea and land breezes (SLB), shaped by its numerous islands, are key drivers of the tropical climate. Island morphology, terrain, land cover, and orientation relative to prevailing winds affect these breezes and associated convection. While research has largely focused on larger islands, smaller islands like Java remain understudied. Java features a mountainous chain with several gaps and experienced significant land use and land cover changes (∆LULC) over the past two decades. This dissertation aims to: 1) adapt observational methods to detect mesoscale boundaries in numerical models, 2) analyze the role of Java’s topography and cloud- radiation feedback on SLB and convection, and 3) assess the impact of land use and land cover changes on SLB and convection. The first part of the study evaluated the efficiency of scatterometers in detect- ing coastal mesoscale boundaries at different spatial resolutions, identifying 3-km grid spacing as optimal for the wind gradient method. The second part involved numerical experiments that varied complex terrain and cloud-radiative feedback. Factor sepa- ration analysis using a 3-km grid output revealed that complex terrain weakens the diurnal precipitation cycle, especially offshore rainfall driven by land breezes. Gaps in Java’s mountains chain accelerate land breezes by 0.8 m/s, while cloud radiative forcing reduces cloudiness and rainfall, with a stronger effect in areas with complex terrain, enhancing down-valley flow by 2 m/s and intensifying land breezes. Finally, the study analyzed satellite observations over the past two decades and found significant ∆LULC in Java, including a 56% increase in savannas and an 11.5% decrease in forests. Frequency of occurrence of clouds (FOC) over mountain peaks increased by 10%, while precipitation in western Java increased by 2.2 mm/day. Numerical model experiments showed ∆LULC contributed to a 20% increase in FOC in some mountain areas, partially explaining these tendencies. ∆LULC impacts on clouds varied with Bowen ratio at low elevation, increasing or inhibiting formation. However, the effect of ∆LULC on offshore land breezes and rainfall was minimal. This research offers new insights into how surface processes modulate SLB on smaller islands in the MC.
Recommended Citation
Priftis, Georgios, "The role of surface processes in modulating land-sea breeze circulation : an observational and numerical modeling study in Java" (2024). Dissertations. 426.
https://louis.uah.edu/uah-dissertations/426