Analiza vertikalnih strujanja u tropskom konvektivnom graničnom sloju tijekom mjerne kampanje DACCIWA

master's thesis

• Title (english): Analysis of vertical motions in tropical convective boundary layer during DACCIWA field campaign
• Author: Petar Golem
• Mentor: Maja Telišman Prtenjak (mentor)
• Mentor: Karmen Babić (mentor)
• Committee member: Maja Telišman Prtenjak (predsjednik povjerenstva)
• Committee member: Željko Večenaj (član povjerenstva)
• Committee member: Marijan Herak (član povjerenstva)
• Committee member: Branko Grisogono (član povjerenstva)
• Committee member: Iva Dasović (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Geophysics); Zagreb
• Defense date and country: 2020-09-24, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Geophysics; Meteorology and Climatology

Abstract

Doppler lidarska mjerenja vertikalne brzine provedena u okolici Savè-a (Benin) u sklopu projekta DACCIWA iz 2016. godine korištena su kako bi se okarakterizirala statistička svojstva konvektivnih vertikalnih strujanja u tropskom konvektivnom graničnom sloju (CBL-u). Metoda uvjetnog uzorkovanja korištena je kako bi se identificirala i odvojila silazna i uzlazna strujanja. Odabrana su dva slučaja rano poslijepodnevnog CBL-a – jedan s formacijom plitkih kumulusa i jedan bez. Vrijednosti statističkih veličina normaliziranih skalama sloja miješanja u oba režima nisu pokazale značajnije razlike. Uzlazna strujanja su zauzimala oko 18–23%, a silazna 50–53% vremenskog zapisa na oba dana. Prosječne širine uzlaznih strujanja iznose oko 0.22–0.28zi, dok su širine silaznih oko 1.5 puta veće. Prosječne vertikalne brzine unutar strujanja iznose oko 0.51–0.56w∗ u oba smjera. Vertikalne brzine unutar strujanja ovise o širini istog. Vertikalne brzine rastu od 0.4w∗ za strujanja manjih dimenzija (manjih od oko 0.2zi) do 0.8w∗ za strujanja širine graničnog sloja. Brzine u silaznim strujanjima su oko 20% manjih iznosa u slučaju širih strujanja. Krivulje ove ovisnosti skalirane skalama sloja miješanja jednake su u oba odabrana slučaja. Zaključujemo da u odabranom slučaju prisustvo plitkih kumulusa, bar što se tiče statističkih veličina vertikalnih strujanja, nije imalo značajniji utjecaj na razvoj i stanje graničnog sloja.

Abstract (english)

Doppler lidar measurements of vertical velocity taken outside Savè (Benin) as a part of the DACCIWA program that ran trough the June and July of 2016 are utilized to characterize the statistical properties of the convective vertical motions in the tropical CBL. Method of conditional sampling is used to identify and separate updrafts from downdrafts. Two cases of early afternoon CBL are chosen – one with formation of shallow cumulus clouds and one without. Updraft and downdraft statistics, once normalized by mixed layer scales, do not show significant variation between the two regimes. Updraft stake up about 18–23%, and downdrafts 50–53% of the lidar timeb series. Average updraft widths range from 0.22zi to 0.28zi, and downdrafts are about 1.5 times wider. Draft–mean vertical velocity is 0.51–0.56w∗ in both directions. Draft–mean vertical velocities show dependence on the draft's width. Vertical velocities increase from about 0.4w∗ for smaller drafts (smaller than about 0.2zi) to 0.8w∗ for drafts with widths equal to BL depth. Downdraft–mean velocities are about 20% weaker for large draft widths. Once normalized by mixed layer scales, curves of this dependence for the two chosen cases collapse onto each other. We conclude that, inasmuch draft statistics are concerned, presence of shallow cumuli did not have a large impact on development and state of the BL.

• Keywords: granični sloj; termali; plitki kumulusi; kampanja DACCIWA
• Keywords (english): boundary layer; thermals; shallow cumuli; DACCIWA campaign
• Language: croatian
• URN:NBN: urn:nbn:hr:217:789684
• Study programme: Title: Graduate university study pf Physics - Geophysics; specializations in: Seismology and Physics of the Earth's Interior, Meteorology and Physical Oceanography; Course: Seismology and Physics of the Earth's Interior; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra fizike – geofizike (magistar/magistra fizike – geofizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2020-10-13 08:25:36