Interaction of a Sea Breeze and a Moist Convection Over The
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Interaction of a sea breeze and a moist convection over the northeastern Adriatic coast: an analysis of the sensitivity experiments using the high‐resolution mesoscale model Gabrijela Poljak1, Maja Telišman Prtenjak1, Marko Kvakić2, Kristina Šariri3 and Željko Večenaj1 1Andrija Mohorovičić Geophysical Institute, Department of Geophysics, Faculty of Science, University of Zagreb, Zagreb, Croatia 2ILRI, Nairobi, Kenya 3Croatian Metrology Institute, Zagreb, Croatia email: [email protected] & [email protected] Motivation & Aim Results -> Evaluation of the model Results -> Sensitivity tests ¾ The northeastern (NE) Adriatic, in particular, Impact of the SST variability (9/July/2006 at 15 CET) the Istrian peninsula, represents the most In-situ statistical evaluation: Taylor diagram for Pula-Airport ECMWF SST satellite SST convective area in Croatia especially in the 8/Jun/2003 9/Jul/2006 8/Aug/2006 warm part of the year (Mikuš et al., 2012). ¾ In at least 51% of daytime Cb occurrences, sea C) breezes (SB) develops along the coast. (e.g. ° Babić et al., 2012; Poljak et al., 2014). ¾ The SB characteristics highly depend on location and local topographic characteristics. ( Temperature ¾ The influence of the size and temperature of the water surface and topography on the SB- Cb interplay at particular Adriatic area is still 8/Jun/2003 9/Jul/2006 8/Aug/2006 insufficiently known. Mixing ratio (kg/kg) Fig. 3: Taylor diagram for temperature (°C) and mixing ratio (kg/kg) for three selected cases. The acceptable mesoscale model skill could be done if Stdev_WRF ~ Stdev_M and RMSD < Stdev_M (Pielke, 2002). This is mostly not valid for Kessler microphysics option. Experiments biases {obs-fcst} for speed (m/s) PBL 8/Jun/2004 9/Jul/2007 8/Aug/2006 YSU -0.87 -0.99 -0.85 -0.82 -1.12 -0.72 -0.90 -0.93 -1.08 -1.09 -1.06 -1.34 MYJ -0.86 -1.05 -1.09 -1.01 -0.97 -0.38 -1.32 -1.10 -1.11 -0.83 -0.77 -1.18 BL -0.80 -0.88 -0.81 -0.85 -1.09 -0.83 -0.92 -1.08 -1.13 -0.97 -0.99 -1.00 O Kess Lin WSM6 O Kess Lin WSM6 O Kess Lin WSM6 Microphysics Fig. 1: The satellite SST and ground temperature distribution in the area of interest (the northern <-0.8 -0.8->-0.9 -0.9->-1.0 -1.0->-1.1 -1.0->-1.1 >-1.2 Adriatic at 11 CET on 9 July 2006) and measuring sites Fig. 4: Experiments biases for all experiments for speed (m/s) in Pula Airport. as white circles (Udine, San Pietro Capofiume (SPC), Portorož-Airport, Pazin, Poreč, Pula-airport). Biases computed as observed minus each experiment forecast. Regardless the model setup, the WRF model always underestimated wind speed. Data In-situ statistical evaluation: spectral analysis ¾ Three chosen cases from Poljak et al. (2004): sim01 sim02 sim08 sim11 sim12 sim18 ¸sim21 sim22 sim28 sim61 sim62 sim68 obsv 7 8 4 32 0.02 Fig. 6: Distribution of 10-m wind, (wind vectors and speed in m/s) (i) 8/June/2003 (a) (b) (c) (d) (e) 2 (ii) 9/July/2006 6 6 30 0.018 in (a,b), sensible heat flux, W/m (c,d) and 10-m wind with the 2 5 28 ] ] 4 0.016 ] (iii) 8/August/2006 ] maximum simulated radar reflectivity factor, dBZ (e,f). More −1 −1 −1 4 −1 26 2 0 0.014 realistic SST distribution caused a larger sea-land temperature ¾ Radiosounding (Udine & SPC) and near [°C] [m s t [m s 3 [m s 24 H [kg kg v u V surface data (Fig. 1). 0 q 0.012 difference, stronger SB with larger vertical speeds and stronger 2 22 −2 deep convection. 1 −2 20 0.01 0 −4 −4 18 0.008 1 12 24 36 1 12 24 36 1 12 24 36 1 12 24 36 1 12 24 36 −6 Model WRF-ARW, V3 hour hour hour hour x 10 hour (f) (g) 5 (h) (i)20 (j) 5 Impact of the modified topography (MT): 9 July 2006 ¾ initial and boundary conditions (every 6 h) 1.2 1.2 4 4 ] ] 15 ] ECMWF analysis; 1 ] 1 −2 −2 ] −2 −2 2 s s s kg 2 3 3 2 2 ¾ vegetation and land-use data: USGS 24; 0.8 0.8 2 ) [°C 10 f ) [m ) [m ( ) [m f t f f ) [kg ( 0.6 0.6 ( ( ¾ 3 domains (dx=13.5 km, 4.5 km, 1.5 km) & 2- f H 2 2 ( v u fS V q fS fS fS 0.4 0.4 fS way nesting on a Lambert conformal 5 1 1 projection; 0.2 0.2 0 0 0 0 0 ¾ top of the atmosphere = 50 hPa & 80 sigma 30 20 10 5 3 2 30 20 10 5 3 2 30 20 10 5 3 2 30 20 10 5 3 2 30 20 10 5 3 2 T [h] T [h] T [h] T [h] T [h] levels; Several physical options for all domains: Fig. 5: Observed versus modelled time series (top) and power spectra (bottom) Constant: for Portorož-Airport site for 8/June/2003; (a,f) the horizontal zonal wind (m/s), ¾ RRTM for the longwave radiation; (b,g) zonal wind component (m/s), (c,h) merdional wind component (m/s), (d,i) ¾ Dudhia scheme for the shortwave radiation; temperature (°C), (e,j) mixing ratio (kg/kg). The observed time series and ¾ a five-layer thermal diffusion scheme for the spectrum is presented by black line. soil temp.; ¾ the Betts-Miller-Janjić cumulus The image moment analysis, IMA (e.g. Sović et al., 2013) parameterization in 2 outer domain Varying: ¾ PBL schemes: YSU, MYJ and BL ¾ Microphysics schemes: Kessler, Lin, WSM6 Sensitivity numerical tests: (i) a varying SST field provided by the MSG SEVIRI geostationary satellite data (at 5 km) every hour (SST L3C hourly data, Fig. 1); (ii) a modified topography. Fig. 5: The IMA method is used for the analysis of convection comparing the maximum simulated radar Fig. 7: Diurnal evolution of the modeled 10-m wind (in m/s) reflectivity factor (dBZ) with observed associated with the maximum simulated equivalent radar ones (source: ARSO-www.meteo.si). reflectivity factor (dBZ). The field comparison shows: (i) deeper The model is more successful when the intrusion of the flows with eastern directions over the peninsula; Euclidean distance (ED) is smaller, (ii) later development, smaller humidity advection and slower which means that the model is closer inland penetration of the western SB (eliminated slope winds); (iii) the mountain ridge control the onset and accelerated the Fig. 2: Modifying of to reality. the topography was convection. done by a simple cosine weight function which is zero at the Summary boundary and one in ¾ The application of the three methods in the evaluation of the model and the determination of a model setup did not give a specific conclusion. the center, defined However a choice of MYJ and Lin for PBL and microphysics options gave satisfactory result in the most cases. over a 100x100 point ¾ Sensistivity tests have shown the impact of the SB-Cb interaction. It primarily takes place in the boundary layer due to SB modification and thus square area. affects the convergence zone and the position and the lifespan of convective cells. References Babić K, Mikuš P, Prtenjak MT (2012): The relationship between shallow thermal circulation regimes and cumulonimbus clouds along northeastern Adriatic coast. Geofizika, 29,103-120. Mikuš P, Prtenjak MT, Strelec Mahović N (2012): Analysis of the convective activity and its synoptic background over Croatia. Atmos. Res., 104/105,139-153. Acknowledgements Pielke RA (2002): Mesoscale meteorological modeling, 2nd Edition, Academic Press, USA. This work has been supported by the Poljak G, Prtenjak, MT, Kvakić M, Strelec Mahović N, Babić K (2014): Wind patterns associated with the development of daytime thunderstorms over Istria, Ann. Geophys., 32, 401–420. CATURBO (HRZZ, No. 09/151) project. Sović I, Šariri K, Živčić M (2013): High frequency microseismic noise as possible earthquake precursor. 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