Aerosols, Clouds, and Climate

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Hurricanes induce an “Aeroso...

Title: 
Hurricanes induce an “Aerosol Low” prior to their formation over the oceans
Abstract: 

We report the variability of Aerosol Optical Depth (550nm) from the MODerate Resolution Imaging Spectroradiometer (MODIS), Surface winds from the QSCAT and HYSPILT air mass trajectories, about 15 days prior to the formation of the super cyclones GONU (over the Arabian Sea during 2nd-5th June 2007) and SIDR (over Bay of Bengal during 11th–16th Nov 2007) in the Indian Ocean. The analysis reveals a persistent ‘aerosol-low’ with AOD at 0.1 in the region of the cyclone formation and a region of with AOD at 0.7-0.9 in the adjacent domains. The variability in the QSCAT wind fields and air mass trajectories also support the presence of the ‘aerosol-low’. Analysis of 7 deadliest hurricanes (Katrina, etc) in the last decade over the North Atlantic also reveal the ‘aerosol-low’ patterns of AOD variability, about 15 days prior to the occurrence of these hurricanes.

 

Presentation Type: 
Poster
Co-Authors
Author 1: 
Rahul Reddy
Additional Authors: 
no more authors
Author Roles
Corresponding Author: 
Rahul Reddy
Presenting Author: 
Rahul Reddy

Study of the Radiative Effect ...

Title: 
Study of the Radiative Effect of Smoke in the Southwestern Portion of the Amazon Basin
Abstract: 

During the dry season, large amount of aerosol particles is emitted to the atmosphere in the Amazon Basin. Those particles interact with solar radiation through scattering and absorption processes. Both processes reduce the amount of solar irradiance reaching the surface, while the absorption process can heat the aerosol layer and the scattering process can increase the diffuse fraction of solar radiation. The objective of this talk is to present results of a field experiment conducted in the Southwestern portion of the Amazon Basin during the dry season of 2007 (from 24 August to 29 October), at Reserva Biológica do Jaru (-10,19°; -61,87°), a region surrounded of primary rainforest. Measurements of photosynthetically active radiation (PAR) and global and diffuse broad and narrowband irradiance were conducted. PAR measurements were performed at 7 levels inside the canopy. Additional measurements are continuously performed at a 67m height micrometeorological tower to estimate turbulent sensible and latent heat and CO2 fluxes. From the narrowband data, aerosol optical depth was retrieved and during the field experiment, values higher than 2.0 were frequently observed at channel around 670 nm. Reduction of surface turbulent fluxes was observed due to the presence of smoke, although latent heat flux decreased more slowly, thus, evaporative fraction was higher in smokier or cloudier conditions compared to clear sky conditions. Another result is that the smoke layer reduced the frequency of occurrence of sun flecks due to the attenuation of the direct component of the solar radiation and affected the fraction of absorbed PAR by the vegetation.

Presentation Type: 
Invited Presentation
Co-Authors
Author 1: 
Marcia Akemi Yamasoe
Author 4: 
Bianca Lobo Silva
Additional Authors: 
no more authors
Author Roles
Corresponding Author: 
Marcia Akemi Yamasoe
Presenting Author: 
Marcia Akemi Yamasoe

SERENA Project: remote sensing...

Title: 
SERENA Project: remote sensing of cloud microphysical structure and its interaction with atmospheric aerosols
Abstract: 

The SERENA Project (“Remote sensing of clouds and their interaction with aerosols”, from the acronym in Portuguese) will study experimentally the vertical profile of cloud microphysics and its response to the atmospheric load of smoke aerosols, with a level of spatial and temporal detail that cannot be paralleled by current experimental techniques. This research theme is relevant for weather and climate since aerosols can change the mean lifetime of clouds, their reflective properties, the local thermodynamic conditions within clouds, and their precipitation patterns. These elements have direct influence over Earth's radiative balance, its hydrological and energetic cycles, and they are responsible for a large fraction of the uncertainty in climatic models. In this kind of study measurements using meteorological radars and in situ research aircraft are powerful tools, but they lack the necessary temporal and/or spatial accuracy to fully address the processes occurring in single clouds.
The SERENA Project will retrieve the vertical profile of effective radius of water droplets and ice particles in single clouds, by using measurements of the emerging radiation on cloud sides, while simultaneously measuring meteorological conditions and the aerosol loading in the vicinity of the cloud under analysis. The radiance measurements will be interpreted a posteriori with the aid of radiative transfer simulations in order to retrieve vertical profiles of droplet sizes. Prototypes have been successfully tested in the field.
The results to be obtained will help foster the quantitative knowledge about interactions between aerosols and clouds in a microphysical level. These interactions are a fundamental process in the context of global climatic changes, they are key to understanding basic processes within clouds and how aerosols can influence them.

Presentation Type: 
Poster
Co-Authors
Author 1: 
Alexandre L Correia
Author 2: 
Felipe F Frigeri
Author 3: 
J Vanderlei Martins
Author 4: 
Paulo Artaxo
Additional Authors: 
no more authors
Author Roles
Corresponding Author: 
Alexandre L Correia
Presenting Author: 
Alexandre L Correia

Spatial variability of the dir...

Title: 
Spatial variability of the direct radiative forcing due to biomass burning aerosols and evaluation of the Amazon's land-use change radiative forcing
Abstract: 

We analyzed data from 2000 to 2009 acquired by the radiometer CERES and by the spectrometer MODIS aboard Terra satellite during the biomass burning season peak. Due to the high spatial coverage of those sensors it was possible to obtain the spatial distribution of the shortwave radiative forcing at the TOA over the Amazon.
The study area was limited between the latitudes 3ºN – 20ºS and between the longitudes 45ºW – 65ºW plus an additional area between 3ºN – 11ºS and 65ºW – 74ºW. In order to analyze only the direct shortwave aerosol effect we used only cloud-free sky conditions. The full area under analysis was divided in 0.5º x 0.5º (latitude / longitude) cells. For each cell we calculated the linear fit of the shortwave radiation flux at the TOA against the aerosol optical depth. The average value obtained for the aerosol radiative forcing for this 10-years period was -10.4 +/- 4.4 W/m2, indicating the large spatial and temporal variations during the biomass burning season.
The behaviour of the radiative forcing with the reflectance at 2.1 um has also been studied. It was possible to verify that as the surface reflectance increases the radiative forcing efficiency becomes less negative, with distinct patterns for surface reflectances below and above 8%.
The radiative forcing due to land-use change has been evaluated by taking the difference between the shortwave flux at the top of the atmosphere for clean conditions in forested regions and deforested regions in Rondonia, for satellite view zenith angles lower than 5 degrees. The value obtained for the land-use change radiative forcing was -22 +/- 3 W/m2. This is a significant result since the effect of land-use change is comparable to the direct aerosol effect but triggers a permanent change in the radiation budget.

Presentation Type: 
Poster
Co-Authors
Author 1: 
Elisa Sena
Author 2: 
Alexandre Correia
Author 3: 
Paulo Artaxo
Additional Authors: 
no more authors
Author Roles
Corresponding Author: 
Elisa Sena
Presenting Author: 
Elisa Sena

Study of direct and indirect a...

Title: 
Study of direct and indirect aerosol radiative forcing over clouds using remote sensing measurements
Abstract: 

Clouds and aerosols are key climatic elements and play a major role on Earth's radiative budget, hydrology and energy cycles. This work studies the relationship between cloud properties and atmospheric aerosols in the Amazon Basin using remote sensing from satellite sensors. Standard retrievals of cloud liquid water path, cloud cover fraction, cloud optical depth and aerosol optical depth are examined from the MODIS sensor aboard Terra and Aqua satellites over the Amazon Basin, from 2000 to 2010. The most updated results will be discussed during the conference, seeking to improve the current knowledge about interactions between aerosols and clouds.

Presentation Type: 
Poster
Co-Authors
Author 1: 
Felipe Fábio Frigeri
Additional Authors: 
no more authors
Author Roles
Corresponding Author: 
Felipe Fábio Frigeri
Presenting Author: 
Felipe Fábio Frigeri

Climatic effects of aerosols i...

Title: 
Climatic effects of aerosols in Amazonia
Abstract: 

Aerosol particles are a critical ingredient in the functioning of Amazonian ecosystem. It control cloud properties, radiative balance, nutrient cycling and other important ecosystem functions. In terms of radiative forcing, aerosols from biomass burning can provide a negative forcing of -300 watts/m2, instantaneously, with an average of 7 years of -38 watts/m2. This is a very high forcing, and have important impacts on carbon uptake by the ecosystem. Aerosols increase the diffuse radiation and plants make photosynthesis more efficiently in forests with larger fraction of diffuse radiation. For high amounts of aerosols, photosynthesis is basically shut down. Aerosols from biomass burning also makes efficient cloud condensation nuclei that alters could microphysics very significantly. It was observed an increase in cloud cover from 25 to 60% when aerosol loading increases the Aerosol Optical Depth (AOD) from 0.1 to 0.7.
We will report long term detailed aerosol measurements 2008 to 2011 as part of the FAPESP AEROCLIMA (Direct and indirect effects of aerosols on climate in Amazonia and Pantanal) project. The dataset obtained encompass the first long term aerosol measurements ever performed in Amazonia, elucidating the differences between the biogenic aerosol population naturally released by the forest metabolism and the anthropogenic aerosols brought to the ecosystem by outer sources as well as regional  biomass burning emissions. These data helps to link climatic effects of aerosols with optical, chemical and physical measurements.

Presentation Type: 
Invited Presentation
Co-Authors
Author 1: 
Paulo Artaxo
Author 2: 
Luciana Rizzo
Author 3: 
Kenia Wiedemann
Author 4: 
Samuel P. Camara
Author 5: 
Melina Paixão
Author 6: 
Samuel P. Camara
Author 7: 
Micael cecchini
Author 8: 
Andrea Arana
Author 9: 
Silvia Lucca
Additional Authors: 
no more authors
Author Roles
Corresponding Author: 
Paulo Artaxo
Presenting Author: 
Paulo Artaxo

Evolution of Aerosol Propertie...

Title: 
Evolution of Aerosol Properties Before, During After Fog Events Near Paris, France
Abstract: 

A new instrument, the Aerosol Particle Spectrometer with Depolarization (APSD), was been deployed during the period from November, 2010 through March, 2011 to measure aerosol particle properties as part of the Paris Fog Experiment. The APSD measures the size and degree of light depolarization of individual particles in the size range from 0.5 to 20 μm. Three detectors measure light scattered as particles pass through a focused laser beam by collecting at side and back angles. These three pieces of information provide a measure of the particle size, composition and shape. Many unexpected results have come from the measurements that were made during fog free periods and when fog formed on aerosols with many different sources. Preliminary analysis shows that immediately proceeding many of the fog events, there was an abrupt increase in depolarization events signaling the possibility of increased biogenic activity. At other times, significant shifts in the size distribution seem linked to processing of the aerosols by the fog. The APSD promises to offer important new information on aerosol properties that were not previously possible.

Presentation Type: 
Platform Presentation
Co-Authors
Author 1: 
Darrel Baumgardner
Author 2: 
Graciela Raga
Additional Authors: 
no more authors
Author Roles
Corresponding Author: 
Darrel Baumgardner
Presenting Author: 
Darrel Baumgardner

Impact of the Unusual Dust Haz...

Title: 
Impact of the Unusual Dust Haze on Regional Climate of Sub-Sahel West Africa
Abstract: 

Aerosol optical properties over sub-Sahel West Africa is presented in this study. Changes in meteorological parameters, aerosol optical depth (AOD), Angstrom exponent α, infrared (IR) sky temperature and atmospheric emissivity were further investigated before, during, and after major dust storms. The analysis showed significant changes in all of the above parameters due to increase in atmospheric dust loading. Shortly after the storm arrived, air pressure rapidly increased, temperature decreases, relative humidly increased from 10% to 30%, the wind direction became northerly and the wind speed increased to  a maximum of 30 m/s. Measurements show pronounced seasonal influence with maximum dust loading during the cold winter “harmattan” seasons of every year. Large values of aerosol optical depth (AOD), 500nm > 1.50 combined with low values of Ångström exponent α < 0.2 were mainly observed during the dust periods. The aerosol direct radiative forcing (ADRF) at the bottom and the top of the atmosphere ΔF, and forcing efficiency ΔFeff evaluated from the Sun-photometer measurements during the harmattan period (often associated with desert dust + biomass burning) is reported for this region for the first time. The aerosol volume size distributions show distinct fine (geometric mean radii of 0.18 ±0.13 µm) and coarse modes (geometric mean radii of 4.71±4.55 µm) with a remarkable increase in the volume concentration during the harmattan dust episodes. The global and direct radiation components decreased respectively, and the diffuse component increases in comparison with the previous clear day. IR sky temperatures and sky emissivity increased by 18oC and 0.15, respectively, 3 h after the   arrival of the storm.
Keywords: Aerosol, Angstrom exponent, harmattan, radiative forcing, sky temperature, sky emissivity

Presentation Type: 
Poster
Co-Authors
Author 2: 
Vincent Ola Ajayi
Additional Authors: 
no more authors
Author Roles
Corresponding Author: 
Kehinde Olufunso Ogunjobi
Presenting Author: 
Kehinde Olufunso Ogunjobi