Abstract
Abstract. For the first time, vertically resolved long-term lidar measurements of the aerosol distribution were conducted in Haifa, Israel. The measurements were performed by a PollyXT multi–wavelength Raman and polarization lidar. The lidar was measuring continuously over a 2-year period from March 2017 to May 2019. The resulting data set is a series of manually evaluated lidar optical property profiles. To identify the aerosol types in the observed layers, a novel aerosol typing method that was developed at TROPOS is used. This method applies optimal estimation to a combination of lidar-derived intensive aerosol properties to determine the statistically most-likely contribution per aerosol component in terms of relative volume. A case study that shows several elevated aerosol layers illustrates this method and shows, for example, that coarse dust particles are observed up to 5 km height over Israel. From the whole data set, the seasonal distribution of the observed aerosol components over Israel is derived. Throughout all seasons, coarse spherical particles like sea salt and hygroscopically grown continental aerosol were observed. These particles originate from continental Europe and were transported over the Mediterranean Sea. Sea-salt particles were observed frequently due to the coastal site of Haifa. The highest contributions of coarse spherical particles are present in summer, autumn, and winter. During spring, mostly coarse non-spherical particles that are attributed to desert dust were observed. This is consistent with the distinct dust season in spring in Israel. An automated time–height-resolved air mass source attribution method identifies the origin of the dust in the Sahara and the Arabian deserts. Fine-mode spherical particles contribute significantly to the observed aerosol mixture during all seasons. These particles originate mainly from the industrial region at the bay of Haifa.
Highlights
Automated, continuous height-resolved measurements were performed by the multi-wavelength Raman and polarization lidar PollyXT of TROPOS for 2 years from March 2017 until May 2019 at the Technion in Haifa, Israel, in collaboration with the Viterby Faculty of Electrical and Computer Engineering
3.1.6 Conclusions from optical properties. Using these optical property profiles, we can conclude so far that, due to high Ångström exponents and low depolarization ratios, small, spherical particles are likely to be present in the planetary boundary layer (PBL)
Upper layer, the low Ångström exponents and the higher depolarization ratios indicate the presence of large, non-spherical particles, like desert dust
Summary
Continuous height-resolved measurements were performed by the multi-wavelength Raman and polarization lidar PollyXT of TROPOS for 2 years from March 2017 until May 2019 at the Technion in Haifa, Israel, in collaboration with the Viterby Faculty of Electrical and Computer Engineering This is the first long-term observation of the vertical aerosol distribution in Israel. We analyze vertically resolved aerosol measurements performed by lidar and present a new retrieval scheme developed at TROPOS (Floutsi et al, 2019) in order to identify the aerosol types observed above Haifa This retrieval scheme applies the optimal estimation method (OEM) to a combination of lidar-derived intensive aerosol properties (i.e., concentration-independent), to determine the statistically most-likely contribution per aerosol component in terms of relative volume. The results of the aerosol typing and air mass source attribution for the entire measurement period are presented From these results, the seasonal variations of the vertically resolved aerosol distribution over Haifa is derived.
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