APPLICATION OF MICROWAVE HIGH FREQUENCIES FOR THE EVALUATION OF CLOUD PROPERTIES AND RETRIEVAL OF
PRECIPITATION RATES
S. Laviola, E. Cattani, and V. Levizzani
Institute of Atmospheric Sciences and Climate, National Research Council of Italy - ISAC-CNR
Via Gobetti 101, I-40129 Bologna, Italy
Corresponding author: s.laviola@isac.cnr.it
Radiation in the microwave frequency range higher than 90 GHz is highly sensitive to the scattering of hydrometeors.
In this work two methods based on the scattering and absorption of radiation by cloud droplets and hydrometeors are
presented.
The 183-WSL (Laviola and Levizzani, 2011a) is a fast rain rate retrieval method which also classifies precipitation
types for applications in nowcasting and weather monitoring. The retrieval scheme consists of two separate algorithms,
for land and ocean, based on the water vapour absorption band at 183.31 GHz. This technique combines the
contribution of the five channels of the AMSU-B/MHS radiometers on the NOAA and MetOpA satellites both for the
detection of rain clouds and rain rate estimation.
The MicroWave Cloud Classification (MWCC) method is physically based on the impact of the clouds (perturbed
signal) on the microwave nominal signal in clear sky conditions (unperturbed signal). The perturbation on the signal at a
certain frequency is evaluated by means of the ratio between the measurement of radiances and its absolute maximum
value (clear sky conditions). All perturbations of different frequencies are combined in a cascade test, which computes
the scalar PMWCC indicating the type of clouds for each observed pixel. As a final output a six-class distribution of cloud
type (three for each stratiform and convective type) is produced where the magnitude of the perturbation index PMWCC
specifies the development stage and the cloud type.
An application of these methods will be presented for studying severe meteorological phenomena over the
Mediterranean Sea. During the warm season when the sea surface temperature is higher than 15-18 °C Mediterranean
storms generally develop as deep organized systems possibly evolving up to the stage of mesoscale convective systems
(MCS). In the last twenty years a subset of these meteorological systems with tropical-like characteristics was classified
as Medicanes (Laviola et al., 2011b).
References
Laviola, S., and V. Levizzani, 2011a: The 183-WSL fast rain rate retrieval algorithm. Part I: Retrieval design. Atmos.
Res., 99, 443-461.
Laviola, S., A. Moscatello, M. M. Miglietta, and V. Levizzani, 2011b: Satellite and numerical model investigation of
two heavy rain events over Central Mediterranean. J. Hydrometeor., 12, 634-649.