Fifty Years of African Dust Studies in the Caribbean Basin: The Role of Dust in Climate and Air Quality

Poster thumbnail
Session IV: Initiatives to improve observational coverage of the ocean, land, and atmosphere
Joseph
Prospero
Rosenstiel School of Marine and Atmospheric Science, University of Miami
Mineral dust has received increasing attention in climate assessments because it can affect climate through radiative and cloud processes and through ocean fertilization and the carbon cycle. But the generation and transport of dust is itself a function of climate. Our aerosol studies show that the Caribbean Basin is greatly impacted by African dust. Measurements that began on Barbados in 1965 show a strong summertime maximum which has varied greatly over 50 years. Most notable was the huge increase observed in the early 1970s and 1980s that was linked to the onset of drought in North Africa. Recent records from Cayenne show that during spring dust is carried to South America at rates comparable to those observed on Barbados in summer. The dust reaching the western Atlantic falls almost entirely within the size range under 10 µm diameter (i.e., PM10) and thus can impact air quality and human health. Because of dust, PM10 in the Basin frequently exceeds the WHO guideline at frequencies comparable to those measured in major urban areas in Europe and the US. To assess the impact of dust on health we need to understand the factors that modulate dust emissions in Africa and transport across the Atlantic and we need to better characterize the properties of this dust as they relate to human health. These need to be linked to studies in the Basin that focus on respiratory and cardiovascular health and the role that dust might play in health. For maximum effectiveness, studies of aerosols and health should be carried out in an integrated framework. Plans are underway to establish an ad hoc multi-institutional federated network of aerosol and radiation measurements throughout the Basin. These would be integrated with satellite products and chemical transport models so as to produce forecasts and health alerts.
Day 
Thursday, September 10, 2015

Number of comments:   14

Comments

Hi Joseph,

Thanks for sharing your work! The link between dust transport and local climate is an important source of variability over the regions affected.

I can see your poster and paper (Prospero et al. 2014) show records for specific measurement locations in the Caribbean. Last year, an anormal deposition of African dust was observed in central Colombia (June 27, 2014). Previous local measurements do not indicate such large deposition of material from the Sahara. We have a poster related to that event (https://usclivar.org/2015-iasclip-abstract/saharan-dust-transport-northern-south-america-case-study). Are you aware of how common is that large concentrations of African dust deposit over central Colombia? This event occurred in late-June, when the ITCZ is usually northward.

Many thanks!

The event in late June 2014 was rather large. But it was not usually large in the context of African dust transport in comparison to what we on occasion measure at Barbados. It was unusual in that the transport was carried to the low latitudes at this time of year (late June). In the paper that you site (Prospero et al., 2014) you will see that the transport to Cayenne is at a maximum in March-April. Transport drops off sharply after that time. I believe that the the June 2014 event was unusual because we were entering into an El Nino phase which is generally associated with a southward shift in transport paths.

This discussion reminds me of a paper that I read in Scientific America in the 1960s when I first became interested in AFrican dust. The paper (really, an extended note) described the calinha (sp?), episodes of dense haze observed in Venezuela (as described by the writer) in the spring. I concluded that it was African dust. I expect that dust would be more difficult to detect by remote sensing (or by samplers) because of other sources of aerosols in the region that could obscure the effects of dust. It might be interesting to take a look at the CALIPSO product to see if you could detect such events. See for example: Adams, A. M., J. M. Prospero, and C. Zhang (2012), CALIPSO derived three-dimensional structure of aerosol over the Atlantic and adjacent continents, Journal of Climate.10.1175/jcli-d-11-00672.1

I look forward to chatting with you.

Joe Prospero

Very interesting big picture view of the role of dust in the intra-Americas climate. Indirect effects are hard to measure, i.e. impacts on SSTs including possible lags. May be numerical ensembles under low/high dust seasons may provide valuable information with focus on flux variability. The direct effects such as precipitation could be measured by the type of network you suggest, have you looked at the role of aerosols on precipitation i.e. large concentrations of CCN may lead to suppression (direct), this coupled to reduced convection (indirect). We suggested the possible role on the direct effect of precip in 2-articles in the past (JGR-A).

Please, note that in Puerto Rico there are various instruments that could be of use to the network, 2-lidars, 1-ceilometer, focus on AOT and PBL heights. We will be glad to make the link, one of them is operated by our center (NOAA-CREST).

Best regards. Jorge.

Are your lidars (and other products) on-line?

Ceilometer and LIDAR data may be attained from:

http://ece.uprm.edu/noaa-crest/
Ceilometer data is available from May 2013-January 2015.
LIDAR data is available form December 2008 to September 2014.

Data from both sensors will be updated soon to reflect this summer 2015 field campaign where the ceilometer was run continuously while the LIDAR on a daily basis. Other instruments were used during the field study for Convection and Aerosols. Results of this 2015 campaign will be published in BAMS. Hope this is helpful.

I notice that you have an AERONET instrument. But the record is sporadic as are those at other PR sites. It would be very helpful to have a continuous quality record in the future to fit into the concept of an ad hoc network. What are your plans in this regard? Do you work with Olga Mayol: You might be interested to know that we are holding a meeting in Barbados on 16 October to discuss future air quality measurements across the region. Olga will be attending.

Hi Joseph -

The AERONET site at La Parguera has the best record in Puerto Rico. They have level 1.5 data (cloud screened) from July 2000 to the present, and level 2.0 data (cloud screened and quality assured) up until April of 2015. Here is the link:

http://aeronet.gsfc.nasa.gov/cgi-bin/type_one_station_opera_v2_new?site=La_Parguera&nachal=0&year=23&aero_water=0&level=3&if_day=0&if_err=0&place_code=10&year_or_month=1

Mayaguez AERONET has been running most of the time since it's inception, although the sunphotometer have to be serviced by NASA two or three times.

Continuous operation of at least 1 of the sensors could be coordinated if operated as part of long-term campaigns.

We do interact with Olga in occasions.

The Barbados workshop sounds interesting, if open for guests, can you please share the agenda? my email is: gonzalez@me.ccny.cuny.edu.

Thanks. Jorge.

Yes, the various interactions are complex and difficult to disentangle. It is clear that dust does indeed impact on SSTs in the tropical Atlantic. I do not recall if anyone has examined the degree to which they impact the Caribbean Basin.

There are extensive ongoing investigations of radiation-aerosol-cloud interactions in the region. Bjorn Stevens of the Max Planck Institut für Meteorologie, Hamburg< established the Barbados Cloud Observatory (BCO) on Barbados in 2010. The BCO is a very advanced facility carrying out a wide range of measurements (http://barbados.zmaw.de/). This effort is cooperative with the Caribbean Institute of Meteorology and Hydrology located at Husbands, Barbados (Dr. David Farrell, Principal.

At Miami Dr. Paquita Zuidema and Bruce Albrect study African dust effects on clouds and radiation. We have a dedicated facility: The Cloud-Aerosol-Rain Observatory (CAROb) located the the UM Rosenstiel School on Virginia Key.

I am aware of the activities on Puerto Rico through my contacts with Olga Mayol (University of Puerto Rico - Rio Piedras) with whom I have interacted for many years.

With regard to the "ad hoc federated network"mentioned in my presentation, we will hold a meeting in Barbados on 16 October at CIMH, Barbados. The main purpose of the meeting is to celebrate the 50 anniversary of atmospheric and climate research on Barbados. But it will also serve as a means of initiating discussions about the development of the "ad hoc" federated network in the Caribbean Basin.

In response to the earlier comment by Paola Arias:

In my response, I spoke of my long interest in dust in the Caribbean and in particular in northern South America. I mentioned a phenomenon (which I misspelled), the "calina". I stated that I had read an article in Scientific American in the 1960s. I tracked down the article:

The Amateur Scientist
An amateur investigates the origin of Venezuela's peculiar fog: the calina
By C. L. Stong
Scientific American, 1961

It is interesting that a query of Google turns up no other mention of this phenomenon except in a rather poor short piece in Wikipedia. I am quite certain that a major factor in the calina is African dust. It would appear that this would be a good research project to pursue in the context of the larger interest in long-range African dust and its impacts on the region, including health.

Joseph,

I have long found this connection between Africa and the Caribbean via dust transport interesting and important. Some of our recent work (Martin et al., 2014) using CMIP5 models to investigate decadal variability in West Africa has shown that at least some CMIP5 models are able to represent the feedbacks between Atlantic SST - Sahel rainfall and Saharan dust. I was quite surprised and encouraged that we could see dust being transported into the Atlantic in some of these climate models in response to changing SST and rainfall. There certainly seems to be potential for examining these processed in a "model world" to compare with reality.

Elinor

Amato Evan has published a number of papers on this subject.

It is a real challenge to model dust, as you know. The dust generation process is so highly nonlinear with respect to wind speed (third power) and to soil moisture. Also to small-scale terrain effects. One of the objectives of our ad hoc network is to acquire data on a scale that will provide a data set that can be used to test and develop models.

The dust story this year has been rather unusual. We experienced very strong and very early dust events in the Caribbean and Miami. In Miami we had heavy dust in May continuing into July. And then transport dropped dramatically. We have seen very little dust in Miami or Barbados in August to present. We suspect, of course, that this anomaly is linked to El Nino. We note that some of the highest dust concentrations that we have seen since the 19980s was in 1998 during that strong El Nino year. But, having said that, over the long record it is difficult to identify a strong and consistent relationship.

A very interesting poster. Would you be able to point me to papers, where circulation changes to the North Atlantic Subtropical high and trade winds affects the rate of dust deposition in the Caribbean Sea. With so much work being done the role of the Atlantic warm pool and its synergism with the overlying atmospheric circulations, I wonder if the interannual variations of the warm pool could have an implication on the dust deposition in the Intra-American Seas.

Send an eamil to me at jprospero@rsmas.miami.edu and I will send some citations to you.