How many truckloads for carrying a typical “boomerang” Saharan dust over the Atlantic?

Saharan dust outbreak often occurs across the Atlantic. Here, a big #aerosol plume was captured by  the Sentinel-3 Ocean & Land Colour Instrument (OLCI) from the  Copernicus programme led by the European Union (EU). A big fraction of it usually travels across-Atlantic and one may think it doesn’t come back to us…

Screenshot 2019-11-01 at 22.17.49.png
Red-Green-Blue (RGB) composite imaged from Sentinel-3 OLCI, 2019.11.01. Source:

But the forecast of Aerosol Optical Depth (AOD) for Friday 1st November 2019, computed by the Copernicus Atmospheric Service (CAMS) & depicted by the Windy on-line application, shows a striking dust “boomerang”-like pattern. After travelling a large distance, a heavy dust load eventually comes back to South Europe. Wind is a key factor explaining such aerosol long-range transport.

Screenshot 2019-11-01 at 22.23.47.png
AOD forecast for Friday 2019.11.01 at 11 am, computed by CAMS and illustrated by Windy. Source:,15.708,-55.020,3

My colleague, Dr. Antti Lipponen, researcher at the Finnish Meteorological Institue (FMI), evaluated this transport phenomenon in a fancy unit. “Based on NASA’s GEOS-FP analysis the area of the dust over the Atlantic Ocean is about 9.1 million km² and the mass of the dust about 2.6 million tons (2 600 000 000 kg). If a truck would carry 40 tons of dust it would make about 65 000 truckloads!!!

Screenshot 2019-11-03 at 14.50.10.png

More information?

  • Windy here
  • Copernicus Atmospheric Service (CAMS) here
  • Follow Anti Lipponen on Twitter here
  • Aerosol WebPage here

Saharan dust transport over Gran Canaria islands & Cabo Verde

On 2019.02.05, a remarkable dust outbreak issued from the Western Sahara coast spread over Gran Canaria islands. This thick plume, with heavy load of particles, and larger than 1.000 km width, was well observed via a series of satellite images:



Screenshot 2019-04-21 at 10.39.08
Tweet from the AC SAF showing images from Meteosat Second Generation (MSG) SEVIRI (left) and GOME2 Metop UVAI index (right) of the Saharan dust outbreak of 2019.02.05. Source:

Several days later, on 2019.03.02, another Saharan dust was transported over Cabo Verde. Similarly, a very large and thick plume was captured in the images from the NASA SUOMI VIIRS sensor, and measured by the aerosol index UVAI from Tropomi.

Such aerosol dust events regularly occur in these areas. I always find the related satellite images not only impressive but also informative regarding their spatial scales, intensity and transport.


More information?

  • The EU Copernicus programme here
  • Overview of the NASA & NOAA SUOMI mission here
  • The EUMETSAT AC SAF here
  • EUMETSAT agency here
  • TROPOMI WebPage here
  • Current Earth observation satellites with Sentinel-3 & Sentinel-5 Precursor WebPage here
  • Aerosol webPage here


Biomass burning in Central Africa: NOx, CO & aerosol animations from Sentinel-5 P & SUOMI observations

Biomass burning is a major source of trace gases & aerosol particles on a regional and a global scale (Seiler and Crutzen, 1980; Logan et al., 1981; Crutzen and Andreae, 1990; Andreae, 1991). Interannual variations in biomass burning within specific regions of the world can be dramatic, depending on factors such as rainfall and political incentives to clear land. The forest fires in Indonesia during 1997–1998 and those in Mexico during 1998, both related to the El Nino Southern Oscillation (ENSO) induced drought, are well known examples of extreme fire events (e.g. Levine, 1999; Nakajima et al., 1999; Peppler et al., 2000; Cheng and Lin, 2001).

The principal biomass burning areas can be observed in the Amazonian region and in central Africa. Among the trace gases released, NO2 – nitrogen dioxide & CO – carbon monoxide abundances can be very high. Satellite observations are a helpful tool for the identification of these sources in the troposphere and to follow their transport. In addition, these intensive biomass burning episodes release a large quantity of aerosol particles, at fine size and with absorbing properties.

Below are the animations of NO2 and CO columns as observed by the TROPOMI sensor, on-board the Sentinel-5 Precursor mission from the European Copernicus program. These animations cover ~1 month of biomass burning over Central Africa. They are extracted from the SentinelHub Earth Observation (EO) browser.

Additionally, you can visualise here animations based on the NASA SUOMI VIIRS observations showing the fire detected pixels (in red) and the detection of fine absorbing particles in large concentrations. Note that SUOMI and Sentinel-5 P are flying together on the same orbit / same track with only a few minutes apart.


More information?

  • TROPOMI, on-board the Copernicus Sentinel-5 Precursor satellite, here
  • NO2 – nitrogen dioxide here
  • CO – carbon monoxide here
  • Aerosol particles here
  • Trace gases in the atmospheric composition here

Retrieving aerosol height and tropospheric NO2 from OMI – Ebook Thesis online!

Research Thesis book cover – Julien Chimot – July 2018

Almost 3 months ago, on 2018.09.10, I had the privilege to defend my research thesis at Delft University of Technology. A big moment after 4 years of intensive collaboration with my colleagues of the Geoscience & Remote Sensing Department and KNMI and in the presence of several friends and relatives. An very strict protocol to follow according to the Dutch rules and tradition.

My thesis book is now available online as an Ebook here! Feel free to have a look if you are interested by aerosol layer height retrieval, UV-Vis satellite measurements such as OMI, tropospheric NO2, air quality and climate observations. My main papers are concatenated there.

Enjoy the reading!

Seeing electricity energy through night-time pictures

Night-time pictures of of 2018.10.07 observed by the NASA SUOMI NPP VIIRS sensor. Credit NASA Worldview Earthdata

I am never tired of watching at night-time pictures from NASA SUOMI satellite worldview. We can directly observe how much our western societies depend on electricity.

While the last Intergovernmental Panel on Climate Change (IPPC) report just got released, and stresses the urgency to act extremely quickly for limiting the global warming close to 1.5 deg, one should keep in mind that the worldwide electricity sector is one of the highest source of CO2  – Carbon dioxide released in the atmosphere. Do we want to keep our lights on? Let’s ban then coal gas & use electricity sources with low CO2  – Carbon dioxide emissions (including nuclear!).


More information?

  • The last IPCC report here
  • NASA-NOAA Satellite Reveals New Views of Earth at Night here

Just another Day on Aerosol Earth by NASA – A well-done picture highlighting the very diverse aerosol types and their heterogeneous distributions!

Just Another Day on Aerosol Earth
NASA Earth Observatory images by Joshua Stevens, using GEOS data from the Global Modeling and Assimilation Office at NASA’s Goddard Space Flight Center (Credit NASA,


Have you seen this very recent visualisation aerosol mapping, released by NASA and made by Joshua Stevens? This visualisation very nicely highlights the different aerosol types and their complex distribution on Earth for a single day, 23rd August 2018, based on the GEOS FP model output. Some satellite observations were assimilated to constrain the modelling of atmospheric transport and physical processes.

Atmospheric aerosol are particles suspended in the air. Their sources are very mixed. Aerosol can be man-made or natural: e.g. smoke, desert dust, sea spray, nitrates and sulfates. The aerosol effects on the sunlight modify the shortwave radiation field in the atmosphere. This directly impacts the climate and the satellite observations devoted to ocean surface, land surface, vegetation, and atmospheric gases. Furthermore, heavy load of aerosols affects our air quality.

In spite of many progresses during the last 10-20 years, aerosol observations from space-borne instruments remain incredibly complex. One of the main reasons is their heterogeneity: aerosols are everywhere, but with very variable quantities  spatially (horizontally and vertically!), and temporally. And, as highlighted by this NASA picture, aerosol types are also very heterogeneous! Retrieving all these parameters from single satellite measurements, without ambiguity with respect to surface characteristics and clouds, is the difficult task of the scientists working with atmospheric satellite measurements. Many works to continue to do…


More information

  • NASA WebPage “Just another Day on Aerosol Earth” here
  • Aerosol WebPage here

Sentinel-3 B launch in live from EUMETSAT

We attended the launch of the second satellite platform of the Sentinel-3 mission. An event in live was organised at EUMETSAT, and what a blast!

Check the pictures here.

As part of the Copernicus programme, Sentinel-3 is a very important mission for ocean colour, sea and land surface, fire, atmosphere and climate purposes. With the two platforms, Sentinel-3 A and B, an optimal global coverage will be now obtained. The next observations and related products are promising!

More information?

  • Check the diverse pictures of this fantastic launch via the Twitter accounts of EUMETSAT and ESA
  • Sentinel-3 satellite mission here
  • The current Sentinel-3 services provided by EUMETSAT here

And watch below the movie from EUMETSAT in live in the Sentinel-3 control centre “Sentinel-3: Operating satellites” with Hillary Wilson, EUMETSAT’s Sentinel-3 manager, and Kevin Marston, EUMETSAT’s System operation manager.

Must read – A warning from 15,000 world scientists


25 years ago, in 1992, 1700 independent scientists already told us in their “World Scientists – Warning to Humanity – 1st Notice”. And yet, it seems that was not sufficient. This month, a second notice was submitted, this time by about 15,000 worldwide scientists. And the message is still quite clear: “the world is going toward catastrophic biodiversity loss and untold amounts of human misery” and we have little time to act before avoiding this.

This may sound like an unrealistic, even irrational alarmist message. But it is worth reminding that, since its beginning, science work (and scientists) is beforehand based on observations, facts, interpretations with evaluation of uncertainties, implementing models that are then continuously and thoroughly evaluated  by confronting with observations.

This article is relatively short and very simple to read. No need to be an expert, every citizen can easily understand all the messages. I think this is the duty to each of us to take some minutes for reviewing it, and then thinking about our actions. Especially, the causes are nowadays well identified: rapid population growth, deforestation, agricultural production, and rising greenhouse gases from burning fossil fuels that has triggered and driven our climate change.

For this last one, in spite of continuous denial and unjustified claims (especially in the USA), the odds from IPCC and COP23 are pretty clear: CO2 – Carbon dioxide and CH4 – Methane amount in the atmosphere are historically unique, and the emissions keep increasing. Some of these increases are also even observable from space.

Atmospheric levels of CH4 – Methane from 2003 to 2005 and 2008 to 2010, showing  increased concentrations in the latter dataset (in red). The newly released ‘Climate Research Data Package No. 3’ covers more than one decade (2003–14) of atmospheric data products used to get information on the sources and sinks of carbon dioxide and methane. The data products are available through the website: (Source ESA:


A positive sign: stratospheric O3 – Ozone hole over Antarctic is recovering. If our actions have allowed to create and then solved this problem, then we can still do something, at every level, about the greenhouse gases.

Several journals and websites forwarded this article. But I have the feeling yet it could reach more and more people and lead to further discussions and actions in our societies. Hope this is not too late…


More information?

  • Ripple et al., 2017: Full articles World Scientists’ Warning to Humanity, 1st and 2nd notices here. You can also endorse the 2017 article here
  • European Space Agency (ESA): CO2 – Carbon dioxide and CH4 – Methane on the rise here
  • CO2 – Carbon dioxide WebPage here
  • CH4 – Methane WebPage Here


Preparing TROPOMI to join OMI in space in Autumn 2017

Loading Sentinel-5P (Source:
S5P leaves UK
Moving Sentinel-5P on its way from Airbus Defence & Space in Stevenage, UK, to Standsted airport (Source:

Finally, that’s official! TROPOMI, on-board Sentinel-5 Precursor, the 1st European operational satellite mission devoted to air quality, ozone & climate monitoring, should be launched within the next weeks. And this looks very impressive!

What are the new signs? The Sentinel-5P campaign kicked off, the satellite left UK to Russia some days ago, and several media allow to follow it (through ESA blogs and Twitter accounts). All of these new elements have appeared just some days before our very soon 20th OMI Science Team Meeting focused on the last 13-year developments and data sets.

Let’s keep the fingers crossed that OMI can continue to fly and acquire new observations together with its successor TROPOMI. Autumn 2017 promises to be a very exciting season for our community!

More information?

  • TROPOMI WebPage here
  • OMI WebPage here
  • Sentinel-5P launch campaign kicks off on ESA blog here
  • Farewell to Sentinel-5P on ESA blog here
  • The 20th OMI Science Team Meeting WebPage announcement here


Neural Network, NO2 and aerosol height retrievals at the next 20th OMI Science Team Meeting at NASA, USA

© Rendering of Ozone Monitoring Instrument (OMI) on board of AURA in flight (Source:

The 20th OMI Science Team Meeting will be held at NASA Goddard in Greenbelt MD, USA from Tuesday September 12 through Thursday September 14, 2017. With nearly 14 years of data and the impending launch of TROPOMI on board-Sentinel-5 Precursor, there is much to discuss within the OMI (& TROPOMI) team and user community regarding the current state of OMI, trends and longer-terms records, comparisons with (satellite) data sets, and the validation of OMI data. This meeting will highlight recent OMI results as well as address research plans and program goals for the coming year.

On Tuesday afternoon, at 14:00 during the aerosol – cloud session, I will have the great opportunity to present the status of our activities. In particular, focus will be on the development, application and validation of the OMI aerosol layer height retrieval based on a neural network (i.e. machine learning) approach, and the correction of aerosol radiation effects in the OMI tropospheric NO2 observations.

Gotten curious? See you there then!


More information?

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