Ceilometer evaluation of the eastern Mediterranean summer boundary layer height – first study of two Israeli sites

Abstract

Abstract. Active remote-sensing instruments, such as ceilometers, have been shown to be potentially useful for the investigation of the behavior of the atmospheric mixing layer height (MLH). For the first time ever, high-resolution measurements of backscatter intensity, taken from two CL31 ceilometers situated inland and onshore of Israel, have enabled evaluation of the mean diurnal cycle of the MLH in the eastern Mediterranean region. Although the Israeli summer synoptic conditions are considered to be quite stable, results for the summer season (July-August 2014) showed the inland MLH to be about 200 m higher than the MLH at the onshore site, situated only 7.5 km away. The prevailing influence of the sea breeze front (SBF), as it progresses inland, is presented by the ceilometer plots. Complementing results were found between the radiosonde profiles and the adjacent ceilometer at the inland site of Beit Dagan. In contrast to the expected regularity of clear skies during the Israeli summer, the ceilometers revealed significant cloud cover throughout the day, with higher presence onshore. Assessment of cloud thickness in further research would serve to improve the evaluation of the MLH evolution.

Comparison of aerosol lidar retrieval methods for boundary layer height detection using ceilometer aerosol backscatter data

“…Aerosol backscatter BLHs are derived with a covariance wavelet transform utilizing the Haar wavelet compound step function with multiple user-defined wavelet dilations (Cohn and Angevine, 2000;Davis et al, 2000;Brooks, 2003;Baars et al, 2008;Compton et al, 2013;Uzan et al, 2016). This method identifies the sharp aerosol backscatter gradient corresponding to the top of the BL by calculating the wavelet transform.…”

“…Apart from a few occasions (e.g., André and Mahrt, 1982;Berman et al, 1999;Day et al, 2010), NSL measurements are particularly uncommon since most radiosonde launches are performed during daytime ML hours. In recent years, remote-sensing techniques such as light detection and ranging (lidar), radio acoustic sounding systems (RASS), and sonic detection and ranging (sodar) systems have allowed for the continuous monitoring of the BL (Cohn and Angevine, 2000;Schäfer et al, 2011;Seibert et al, 2000;Emeis et al, 2004Emeis et al, , 2006Emeis et al, , 2012Eresmaa et al, 2006;Baars et al, 2008;McKendry et al, 2009;Muñoz and Undurraga, 2010;Haman et al, 2012;Milroy et al, 2012;Compton et al, 2013;Scarino et al, 2014;Wiegner and Gasteiger, 2015;Uzan et al, 2016). Ceilometers in particular offer a low-maintenance and low-cost solution to constantly monitoring the ML using aerosol backscatter while also facilitating the monitoring of the nocturnal stable layer, internal aerosol layers, and the nighttime residual layer (Haman et al, 2012Pandolfi et al, 2013;Peña et al, 2013).…”

New insights into the vertical structure of the September 2015 dust storm employing eight ceilometers and auxiliary measurements over Israel

“…in the elevated southern site (Nevatim, 400 m a.s.l.). Clouds are identified by the peak shape of the ceilometer profiles (Uzan et al, 2016) and the high rangecorrected signal of 10 −1 m −1 sr −1 which in this case was 4 orders of magnitude higher than the range-corrected signal of the dust plume (shown in Fig. 17b-c).…”

“…20b). An increase in solar radiation enables significant ground heating to values measured prior to the initiation of the dust storm (not shown), thus allowing generation of thermals and the creation of a late sea breeze cycle (Uzan et al, 2016). The entrance of the sea breeze front between 11:00 and 12:00 UTC eventually produced a narrow dust layer ascent visible in mainly on the coastline of Tel Aviv and Hadera ceilometers (Figs.…”

“…The output files were downloaded from the University of Wyoming site (http://weather.uwyo.edu/upperair/sounding.html; sta- tion number 40172). With respect to Stull (1988), the MLH was defined by the RS profiles as the height where an inversion in the temperature was identified along with a significant drop in relative humidity, strong wind shear and an increase in the virtual temperature (Uzan et al, 2016;Uzan and Alpert, 2012;Levi et al, 2011).…”