The answer for the query  about the origin of
the airmasses which pass above us is provided
by the HYSPLIT model, which is available free
of charge at NOAA (USA).

In the plot, which is updated every 6 hours,
we have represented the trajectories followed
by air-masses in the past four days before
they join our sky

... different colours mark different altitudes:

RED:  air reaching the surface level in  Florence

BLUE: air reaching  Florence at an altitude of 2000 m

GREEN: air reaching  Florence at an altitude of 4000 m

The upper plot shows the trajectories projected
on the Earth’s surface; the lower plot shows the
altitude profile of the same  trajectories. Small
circles are plotted at a distance of 6 hours one
from the other; larger circles are plotted at a
distance of 24 hours.

.

Radiosonde profile

The most recent radiosonde profile, which is
updated every 6 hours, is plotted here.
The profile was obtained by interpolating
the nearest sounding (Rome Pratica di Mare)
in time and space. For this reason, it could
be considered valid for Florence only above
the PBL top (~1000 m altitude)

Here are some links to basic meteorology resources, useful for understanding the following graphs and maps

-Meteorology Online Guide

-Meteorology Tutorial

Meteo Maps: Mediterrenean Sea (NOAA GRIB 0.5° res., processed by INO CNR)
Characteristic Altitudes	Temperature Maps	Wind Maps	Relative Humidity Maps
0°C Isotherm	Temperature/Pressure - 2 meters a.g.	Wind 10 m a.g	RH @ 850 hPa
PBL altitude	Temperature and Altitude @ 850 hPa	Wind @ 850 hPa	RH @ 700 hPa
	Temperature and Altitude @ 500 hPa	Wind @ 500 hPa	RH @ 500 hPa
			Precipitable Water

Satellite Images - Mediterranean Sea (METEOSAT 10)
Visibile Image	Infrared Image	Dust

A comprehensive link to European Meteorological resources is http://www.westwind.ch