IMPACT OF SAHARAN ADVECTION ON PLANETARY BOUNDARY LAYER OVER TARANTO (ITALY) BY LIDAR CEILOMETER

(1)

(2)

Scientific Research Abstracts Vol. 5, p. 182, 2016

ISSN 2464-9147 (Online) Atmospheric Dust - DUST 2016

OBSERVED AND MODELLED ATMOSPHERIC VERTICAL PROFILES

IN THE LOW TROPOSPHERE DURING A SAHARAN DUST ADVECTION

OVER APULIA REGION.

FRanCesCa Fedele (1)*, miCaela meneGotto (1), simona ottonelli (1), annaRita tuRnone (1), anna

GuaRnieRi Calò CaRduCCi (1), GianPaolo GoBBi (2), davide dionisi (2), RoBeRto Bellotti (3) (1) Arpa Puglia, Bari, Italy, (2) ISAC-CNR, Roma, Italy, (3) Istituto Nazionale di Fisica Nucleare (INFN), Bari, Italy

Apulia region is located in the south-eastern part of Italy, surrounded by the Mediterranean sea. In this region Saharan dust advections are very common. The present work aims to investigate meteorological main features associated to these advections and in particular to examine by means of both observed and modelled data whether these events affect PBL (Planetary Boundary Layer) height.

In particular, the work is focused on a case study for which there are available experimental data from LIDAR and radiosounding measurements, plus modelled vertical profiles and maps obtained by the WRF (Weather Research and Forecasting) model.

The LIDAR is a one-wavelength near-infrared CHM15K- Jenoptik ceilometer located in a highly polluted in-dustrial site (the ILVA steel plant in Taranto). It operates continuously in automatic mode and produces vertical profiles in the range 0-15 km with temporal resolution of 30 sec and spatial resolution of 15 m. Ceilometer are recently becoming a suitable support for conventional meteorological observation systems [1].

Radiosounding data used in present work are from the Brindisi radiosounding station belonging to the WMO worldwide radiosounding network and providing data every 12 hours (00:00 and 12:00 UTC).

WRF [2] is a Limited Area Model (LAM) of atmospheric simulation giving outputs on domain up to 1 Km of resolution. For the present work the WRF domain was set at a horizontal resolution of 4 Km and a time resolution of 1 hour.

By LIDAR images a Saharan advection event was selected [3], characterized by several dust layers corresponding to different atmospheric pressure layers.

Online desert dust models have indicated that the selected event involved the whole Apulia region, allowing to exploit data retrieved from Brindisi radiosoundings station, 60 Km away from Taranto. These experimental data put in evidence the presence, among the various layers, of air masses with different thermodynamic features. Given the above, the WRF model has been used to simulate those specific thermodynamic features over the area around the LIDAR site. It was found that the meteorological patterns associated to Saharan advection result in an impact on the typical diurnal cycle of PBL height.

[1] Flentje H., Heese B., Reichardt J., Thomas W. (2010). Aerosol profiling using the ceilometer network of the German Meteorological Ser-vice. Atmospheric Measurement Techniques Discussions, 3, 3643-3673.

[2] Skamarock W.C., Klemp J.B., Dudhia J., Gill D.O., Barker, D.M. Duda, M., Huang X.-Y., Wang W., Powers J.G. (2008). A description of the advanced research WRF Version 3. NCAR Technical Note NCAR/TN–475 + STR.

[3] Mattis I., Flentje H., Thomas W., Markl H. (2013). The DWD ceilometer network for Saharan dust observations. In EGU General Assem-bly Conference Abstracts , Vol. 15, p. 12474.

(3)

Scientific Research Abstracts Vol. 5, p. 216, 2016

ISSN 2464-9147 (Online) Atmospheric Dust - DUST 2016

IMPACT OF SAHARAN ADVECTION ON PLANETARY BOUNDARY

LAYER OVER TARANTO (ITALY) BY LIDAR CEILOMETER

simona ottonelli (1)*, miCaela meneGotto (1), annaRita tuRnone (1), anna GuaRnieRi Calo’

CaRduCCi (1), RoBeRto Giua (1), alessandRa noCioni (1), Gian Paolo GoBBi (2), luCadi liBeRto (2) (1) ARPA Puglia, Bari, Italy, (2) ISAC-CNR, Rome, Italy

Saharan dust strongly contributes to the atmospheric aerosol loading in Mediterranean region, thus affecting cli-mate, precipitation cycle, and human health [1].

The use of LIDAR ceilometers is recently becoming a valid alternative to more sophisticated observation systems in order to detect the presence of a Saharan advection and follow its temporal evolution [2]. Indeed, ceilometers are robust, inexpensive and reliable systems that are suitable for continuous operation over long periods. They are able to provide useful information about the vertical profile of clouds and aerosol layers and to retrieve the height of the planetary boundary layer (PBL).

In this study, a ceilometer placed in a highly polluted industrial site (ILVA, the largest European integrated cycle steel plant) has been employed in order to confirm the presence of desert aerosol over the Apulia region in the month of September 2015. The LIDAR is a one-wavelength near-infrared CHM15K- Jenoptik ceilometer, that operates continuously in automatic mode and produces vertical profiles in the range 0-15 km with temporal resolu-tion of 30 sec and spatial resoluresolu-tion of 15 m in the raw signals. The lack of a depolarizer unity makes the compari-son with the output of online desert dust models (BSC-Dream and Hysplit for backtrajectories) necessary for the correct interpretation of the signal produced by the cielometer during the Saharan advection.

The steps of the analysis are described as follows: firstly, the daily profiles are qualitatively analyzed for the identification of the days affected by Saharan dust; secondly, the PBL height is evaluated using a semi-automatic algorithm exploiting three different methods (variance, threshold and gradient of range-corrected LIDAR signal [3]) for each day of the tested month.

Occurrences of Saharan dust advections are found to be associated to a relevant decrease of the maximum daily value of PBL height. Besides, the PBL height and the readings of in-situ PM10 concentration are found to show a negative correlation.

[1] Karanasiou A., Moreno N., Moreno T., Viana M., de Leeuw F., X. Querol (2012). Health effects from Sahara dust episodes in Europe: Literature review and research gaps, Environment International, 47, 107-114.

[2] Flentje H., Heese B., Reichardt J., Thomas W. (2010). Aerosol profiling using the ceilometer network of the German Meteorological Ser-vice, Atmospheric Measurement Techniques Discussions, 3, 3643-3673.

[3] Steyn D. G., Baldi M., Hoff R. M.(1999). The detection of mixed layer depth and entrainment zone thickness from lidar backscatter pro-files, Journal of Atmospheric and Oceanic Technology, 16, 953-959.