STUDIES ON MINERAL DUST USING AIRBORNE LIDAR, GROUND-BASED REMOTE SENSING, AND IN SITU INSTRUMENTATION

In August 2015, the AER-D campaign made use of the FAAM research aircraft based in Cape Verde, and targeted mineral dust. First results will be shown here. The campaign had multiple objectives: (1) lidar dust mapping for the validation of satellite and model products; (2) validation of sunphotometer remote sensing with airborne measurements; (3) coordinated measurements with the CATS lidar on the ISS; (4) radiative closure studies; and (5) the validation of a new model of dustsonde.


INTRODUCTION
From 6 to 25 August 2015, the FAAM BAe-146 research aircraft was based in Praia on the Santiago island (Cape Verde).A ground-based site with several types of instruments was established at the base airport, including two sunphotometers (PREDE-POM01 and CIMEL CE318-NEDPS9 dual-polarization).Additional sun-photometer measurements were available through the permanent AERONET station Cabo Verde in Sal Island.A number of dustsondes of a new type [1] were also launched from Sal.
In this season, mineral dust transport from the Sahara is frequent (see Figure 1).Sixteen research flights were carried out, 10 of which targeted the role of dust as primary heterogeneous ice nuclei (ICE-D campaign).Six more flights, described in this paper and listed in

LIDAR SYSTEM
The aircraft carried a nadir-p elastic backscatter lidar, opera manufactured by Leosphere.Si aerosol extinction coefficient is reference [2].

DUST MAPPING
The dust mapping flights were the spatial distribution and vertic dust layer with the on-board li high altitude over a long distanc is the development of a dust p SEVIRI, based on infrared cha VAR retrieval scheme [3], and yield a good opportunity for it omparisons, such as e.g.Unified Model dust ction of a a large dust load e Canary islands, and a ied out with a refuel at 20 August the experiment a shorter, single flight order of Mauritania on the the cross-section of the ient determined with the the first of these flights.s with little or no dust near ayer is seen to increase in in optical depth.North of is encountered and its This "front" is clearly ible and infrared satellite tern is observed in flights l sections of the mapping d to in situ measurements, down into the dust layer, large particles (up to ~ 100 OD in the high dust region g the limits of the lidar large signal extinction.

IGHT and SAVEX-D
as aimed at a comparison ts to observations from the the International Space scatter lidar operating at aunched in 2015, and with ilar to CALIOP's [4].The flights, instead, was the validation of SKYNET and AERONET groundbased sunphotometer retrievals of columnar aerosol microphysical properties, and in particular the size-distribution [5].The track for these flights was confined within a small area, and the airplane sampled the atmosphere at a series of levels within the dust layer (to measure in situ properties) as well as above (to provide a lidar overview of the scene).As an example, Figure 3 compares the CATS L2 products with the scene depicted by the airborne lidar, showing great consistency.

RADIATIVE CLOSURE, DUST PROPERTIES, AND NEW MODEL DUSTSONDES
In this presentation, we will also show first results concerning our radiative closure studies, the detailed characterization of dust properties, and the comparison of the airborne data with the new dustsondes.

CONCLUSIONS
AER-D has been a very successful campaign, despite relying on a small number of flights.The measurements provide insight on the vertical structure of the Saharan Air Layer and on its microphysical properties; they provide a small but detailed dataset on the dust spatial distribution, designed for satellite and modeling cal/val exercises; and they provide in situ and remote sensing information for the validation of CATS retrievals, sunphotometer retrievals, and the measurements from the new model of dust sondes.
The data analysis is still preliminary at this stage but progress is being made quickly and we anticipate a number of publications in the years to come.

Table
Aerosol extinction coefficient measured by airborne lid ht B923( flight from Cape Verde to the Canary Islands).