Ground Based Remote Sensing and In Situ Measurements of Tropical and Anvil
Cirrus Properties. Radiative effects study in Amazonia during September –
October 2014.
Authors: B. Barja1,2, H. Barbosa1 and D. Gouveia1.
[1] Atmospheric physics Laboratory. Universidade de São Paulo. Brazil.
[2] Atmospheric Optics Group. Meteorological Center of Camagüey, Cuba.
Abstract:
Tropical cirrus and anvil clouds are produced by the deep convective clouds outflows.
Ground based ramman lidar located in ACONVEX site (2.89 ºS 59.97 ºW, 100 m asl),
approximately 25 km up-wind from Manaus-AM, Brazil give the possibility to study the
tropical cirrus and anvil clouds. With this instrument it is possible to obtain the
geometrical characteristics of these clouds, extinction and backscattering coefficients
profile and the optical depth. In the other hand research aircraft measurements of
detailed microphysical properties of tropical cirrus and anvil clouds could be conducted
in the ACRIDICON - CHUVA Campaign during September-October 2014. The set of
the instruments aboard the HALO aircraft will enable to generate composite particle
size distributions, ice water content, effective radius, and particle habit in tropical cirrus
and anvil clouds. Some collocated measurements of tropical cirrus and anvil clouds
could be particularly useful to study their instant radiative effect. It could be possible
with the solar irradiance measurements inside the clouds, above clouds and surface.
Also with all microphysical and macrophysical obtained characteristics some runs of
radiative transfer numerical codes could be conducted in order to compare with the
radiation measurement. The profile of the cloud radiative forcing and heating rates
could be obtained.
There are some results about the geometrical and optical characteristics of the cirrus
clouds using lidar measurements in ACONVEX. The mean geometrical characteristics
during one week of measurements between 30th August and 7th September of 2011,
was determined. During the all period the mean value of base, top and maximum
backscattering heights was 11.5 km, 13.4 km and 12.8 km, respectively. The
maximum/minimum values for these characteristics during overall period were 17.9
km/6.0 km, 19.5 km/6.5 km and 19.2 km/6.4 km, respectively. The optical properties of
cirrus clouds determined for this period with lidar shows the Cloud Optical Depth
(COD) diurnal variation, low values during local night and high values during local
daytime. But the COD values are not higher than 0.7. This indicates that during the
analyzed period only optically thin cirrus clouds are present in ACONVEX site.
There are other results on the geometrical and opticalcharacteristics of cirrus clouds
with lidar in ACONVEX. This results is during the period of two years 2011 and 2012
with the mean values of 12.4 ± 2.0 km, 14.3 ± 2.2 km to the abase and top altitude,
respectively. The occurrence frequency for the whole period was 71.0 %, with a
maximum of 83% in the months of March, April and May and minimum of 52 % in th
months of June, July and August. The cirrus clouds were classified as subvisual with
24%, optically thin 42 % and cirrus stratus 35 %.
These results show that there are cirrus clouds in the altitude where the HALO aircraft
have their maximum flight range (12.501 km). Thus, it is possible to implement some
measurements on tropical cirrus and anvil clouds in the ACONVEX site with the set of
instruments on the HALO aircraft. Using collocated lidar and HALO in situ
microphysical measurements could be possible to develop some studies about
shortwave radiative transfer in tropical anvil and cirrus clouds. This is a proposal to
implement the study as a part of the ACRIDICON - CHUVA Campaign during
September-October 2014.