The Most Important Bora Property Is Its Gustiness. We Studied Bora Gusts by Using New Observa- Tions Collected During the Four-Month Period in 2012

Home , Bora (wind)

AUTHORS: Nejc Povšič, Andraž Jurinčič, Rok Žorž, SUPERVISORS: Nadja Pregeljc, Vladimir Anžel, SECONDARY SCHOOL Ana Čufer, Nika Obed, Mirjam Miletič, Kristijan Zorn, Sebastijan Mozetič, Jože Rakovec, Nedjeljka Žagar, Diocesan Gymnasium Vipava Domen Rabak, Rok Miklavčič, Benjamin Smrdel, Dominik Vrčon Rahela Žabkar, Gregor Skok, Luka Honzak, Vanja Blažica Bora in Vipava Valley Analysis of Observational and Forecast Data

AUSTRIA H The most important bora property is its gustiness. We studied bora gusts by using new observations collected during the four-month period in 2012. On less than 2 km distance, bora velocity ITALY more than doubles. We compared bora forecasts of the SPACE-SI prognostic model with the ob- SLOVENIA CROATIA servations to show that current forecast models lack the ability to describe the bora gustiness. N

0 25 50 km

Example of the Adriatic bora forecast by SPACE-SI New observations Bora simulations model valid for 10.2. 2012 at 19.00. We analyzed new observations from 5 instruments along two SPACE-SI in collaboration with Chair of Meteorology measurement lines. Horizontal distance between the FMF UL has its own operational weather forecast on instruments is about 1.5 km. Bora measurements from 10 3.7 km spatial resolution with WRF-ARW model February 2012 illustrate the main ﬁndings: (http://vreme.space.si). • all observations contain high-frequency variability, typical for bora (bora gusts), A special model setup was prepared for this project, fo- • along A line bora strength doubles from A01 towards A02 over cusing on the Vipava valley region and using higher 1.5 km horizontal and 100 m vertical distance, resolution (1.2 km). Model forecasts have been com- • in the valley average bora speed does not vary from one side to pared with bora observations. another.

25 Line A, 10.2.2012 20 A1 A2 A3 ] s / m [ 15 d e e p s 10 d n i W

5 Impressions

0 Nika: “Bora is a part of my life since the birth and I have 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : : : : : : : : 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 1 1 1 1 1 1 1 1 1 1 2 2 2 2 Model representation of the Vipava valley and surrounding orography. always taken it as a self-evident fact of our lifes. The project Hour enabled me to understand how bora develops and how we can use physics and mathematics to understand and fore- 25 Line B, 10.2.2012 Model veriﬁcation cast its occurrence.” 20 B1 B2 ] s /

m Comparison of model outputs and DARS stations shows [ 15 d

e Mirjam: “As a child, I though bora is everywhere and I was e

p that the model predicts bora occurrence, evolution and s 10 d not aware it is a specialty of our valley. The project has n i average speeds well. However, the model is not capable W tought me how diﬀerent factors work together to make the 5 to represent bora gusts. unique climate of the Vipava valley.” 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : : : : : : : : 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 1 1 1 1 1 1 1 1 1 1 2 2 2 2 25 Hour Zemono, 10.2.2012 Andraž: “I am glad that I could participate in the project. To- 20 s ]

/ gether we came up with interesting ﬁndings. In addition, I m [

15 d

e also improved my knowledge of Excell.“ e s p 10 d n i Other stations W 5 Model Measurements Conclusions 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : : : : : : : : 0 1 2 3 4 5 6 7 8 9 • 0 1 2 3 4 5 6 7 8 9 0 1 2 3 Behind any observations there are errors involved in 1 1 1 1 1 1 1 1 1 1 2 2 2 2 Locations of the DARS (Slovenian Hour making it. motorway company) 25 Ribnik, 10.2.2012 • Clouds sitting on the mountain top can tell the story of 20 measurement sites along the Model Measurements winds behind and above the mountains. s ] / m [ 15

highway H4 through the Vipava d

e • Satellites are able to observe clouds with good resolutions. e s p valley. d 10 • Bora speeds in the valley are 2 times greater than on the n i W

5 slopes. • Current weather models forecast average speeds of bora 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : : : : : : : : 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3

1 1 1 1 1 1 1 1 1 1 2 2 2 2 but can not forecast its gusts. Hour • Bora variation along the valley basin are not signiﬁcant.

Small Satellites Systems and Services - The 4S Symposium 2012 Portorož, Slovenia, 4-8 June 2012