Santiago Gassó, Associate Research Scientist

Santiago Gassó


NASA Goddard
Bldg 33, Room C310
Greenbelt, MD 20771

Phone: 301-614-6244
Fax: 301-614-6420


Remote sensing of absorbing aerosols in the UV-NIR wavelength range

In addition to scatter light, airborne particulate matter such as smoke and dust (also known as aerosols) absorb solar energy. This absorbed energy does not reach the surface and the reduction (or redistribution) of this energy can impact photosynthetic processes in both land and ocean ecosystems. In addition, this energy is returned to the environment in the form of heat and changing the ambient temperature in the atmospheric column. This results in, for example, cloud dissipation among other effects. Thus characterization of these aerosols from space is very important because it will enable a better understanding of their energy balance in the atmosphere as well the processes modulate cloud formation and dissipation. The observation absorbing aerosols is most effective in the ultra-violet range of the electromagnetic spectrum. Currently, very few space sensors have the capability to detect these aerosols. One of them is the Ozone Monitoring Instrument on board the NASA’s Aura satellite. As member of the aerosol science team of OMI (lead by Dr. Omar Torres), I work to improve existing and new approaches to observe these aerosols.
High Latitude Dust in Cold Environments

High Latitude Dust refers to dust generated in mid to high latitudes such as in cold deserts (Patagonia desert in South America) and in the vicinity of glaciers (Alaska, Iceland). The deserts are distinctive in the sense they occur in cold environments, normally not associated with warmer places (such as the Saharan desert) but they do have low precipitation, dry conditions and high winds all necessary conditions for dust production. Satellite images confirm that dust production per event can be abundant. However, the frequency of the events and the abundance of the material produced in these cold environments is much lower than the mid-latitude counterparts. Yet, because their location, they could have a disproportionate and indirect effects in climate. The reason is that most of these sources are located upwind of ocean ecosystems known to be deficient of the micronutrient iron (Fe). Since it is abundant in dust, it is possible that the deposition of Fe may impact the marine ecosystem downwind (specifically via the ingest of nutrients by phytoplankton). Also the study of high latitude dust in modern times can provide clues of the dynamics of atmospheric transport during previous ice-ages. The reason is that the dust is commonly found in ice cores in both poles and it is well known the most of it originated from high latitude sources. By understanding the production and transport patterns of modern dust transport, it will be possible to better understand how past climates evolved.
Observations of the Impact of Passive Volcanic Activity on Clouds

Volcanic activity from space is most easily detectable when the eruption is powerful enough to send ashes above clouds. However, most of the active volcanoes emit gases, water vapor and ash in rather unenergetic eruptions where the emissions stay at cloud level or do not penetrate through the cloud layer aloft. Consequently, the vast majority of volcanic activity remains undetected unless the volcano is nearby a human settlement or a surface remote sensor. In addition, volcanoes are a source of aerosol and aerosol precursors (such as sulfur dioxide) and they are regularly emitted and mixed with clouds in the environment. Because the injection of these materials into the cloud, the cloud micro- and macro-physical properties of these clouds change accordingly. The extent of this impact is rather unclear. However, passive volcanic activity provides a natural laboratory to study the indirect effect of aerosols in clouds such as the change of the cloud’s reflective and precipitation properties.


Dr. Gassó specializes in observational studies of aerosols, clouds and their interactions using a combination of satellite detectors. He has extensive knowledge of the aerosol retrieval algorithms of the detectors MODIS and OMI and their performance.

He is an University of Washington graduate in geophysics (Atmospheric Science track) with thesis work on in-situ observations of aerosols, their optical properties in relation to remote sensing and evaluation of the first versions of the MODIS aerosol algorithm. In his post-doctoral work, he acquired aerosol global modeling experience with the design of a (currently operational) module of the optical and radiative aerosol properties in the Navy Aerosol Assimilation Prediction System (NAAPS) model. Then, he was awarded a NASA grant to evaluate NAAPS model outputs and compare with satellite retrievals of mass concentration and then an ONR grant to evaluate sulfate emission inventories in NAAPS. Also, he has participated as aerosol scientist in the NPOESS Preparatory Project science team (2005-08) . Since 2008, he is an Ozone Monitoring Instrument (OMI) science team and a member of the OMI aerosol remote sensing group led by Dr. Omar Torres. During 2009 to 2011, he lead the Aerosol-Ocean Interactions working group, one of the science working groups for the Aerosol, Clouds and Ecosystems (ACE) mission, a proposed NASA mission to fulfill the NRC Decadal Survey requirements.

In addition to the operational aspects of remote sensing retrievals, his research interests include study of dust at high latitudes. In particular, characterization of its production and long range transport as well as its impacts in biogeochemical and paleo-climate studies. This is an activity he has carried out for the last 15 years. He has been a collaborator and Co-I in internationally funded projects to survey and monitor dust activity in Patagonia. He made the first dedicated satellite and model studies of dust activity in Patagonia. In 2007 , he chaired and organized the Multidisciplinary Workshop on Southern South American Dust held in Puerto Madryn, Argentina, 2007 for which obtained NSF funding and had an attendance 60 participant (~20 international). Between 2010 and 2013, he participated as co-I in a NASA-IDS funded project to characterize dust transport from Alaska glaciers and has been monitoring the area with remote sensing tools since then. Since 2014, he is part of the High Latitude Dust and Cold Environment Network, a working group supported by The Leverhulme Trust (UK). He has authored or co-authored 23 peer-reviewed journal articles many on the subject of dust transport at high latitudes as characterized by satellite, model and surface observations.

Also, he developed an interest in studying volcanoes through a discovery he made in 2006. He found that low levels volcanic activity (non-explosive passive degassing activity VEI<2) can be detected in cloudy conditions by studying the change in properties in nearby water clouds. The discovery provides an excellent opportunity for studying aerosol-cloud interactions as well as provides a way to detect volcanic activity in cloudy conditions.
Twitter : @SanGasso
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