Halifax 2011 Lidar Measurements Archive

This is preliminary data. For more information, contact:

Prof. Thomas J. Duck
Department of Physics and Atmospheric Science,
Dalhousie University,
Halifax, Nova Scotia, Canada, B3H 3J5

Tel: (902)494-1456
Fax: (902)494-5191
E-mail: tom.duck@dal.ca

Halifax is located at 44.6N, 63.6W.

Please see the examples to learn how to interpret our measurements.

The following data sets from the BORTAS-Dalhousie Ground Station (DGS) are also available:

And at other locations of interest:

IMPORTANT: If you plan to publish with any of these data, you must contact the responsible persons and secure their agreement, including co-authorship.



2011-07-03 13:19:17 to 2011-07-03 20:04:00


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2011-07-07 14:58:48 to 2011-07-07 19:21:09

This was a short, four hour test run measurement. The HYSPLIT trajectory shows that the low level aerosols come the Northern US and Great Lake cities. MODIS htspots do not indicate significant fires over central Canada.

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2011-07-08 13:07:28 to 2011-07-08 19:28:54

In this six hour measurement, we see a thick, descending cloud at 5-8 km and a thin aerosol layer at 3 km, in addition to the usual low level aerosols. The HYSPLIT trajectory shows that the 3 km aerosol layer originates over central Canada, and could be a result of boreal forest burning. MODIS hotspots do not indicate strong burning in this region.

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2011-07-10 14:39:30 to 2011-07-12 03:44:13

We see a notable aerosol layer below 2 km during the first half of the measurement, which gets more concentrated in the second half. Back trajectories on the first half (HYSPLIT 1) show that the aerosol plume most likely originated over the NE US and is most likely caused by pollution. The same is seen in the more dense plume at 2300 UTC, July 11 (HYSPLIT 2). MODIS hospots do not show significant activity over the areas where these plumes originated.

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2011-07-13 13:28:44 to 2011-07-13 23:55:58

Measurements on July 13 only span about 10 hours. Aerosol coverage is seen for most of the measurement up to 3km height. At approximately 1600UTC a denser low altitude layer starts to cover Halifax. It is possible that the clouds seen from 1800 to just after 2200UTC between 1 and 2 km are caused by condensation on the dense aerosol layer. The clouds extinguish a majority of the beam for higher altitudes causing the increased levels of noise visible. HYSPLIT back trajectories for the beginning of this dense layer suggest that it might have originated from South-Eastern parts of the Northwest Territories or from Ontario and Manitoba. Both areas had had forest fires, as seen from MODIS hotspot images, in the previous few days indicating that this might be the cause of the increased aerosol coverage.

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2011-07-15 14:59:59 to 2011-07-15 22:33:07


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2011-07-16 20:25:45 to 2011-07-16 22:32:06


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2011-07-17 12:04:10 to 2011-07-17 23:59:56


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2011-07-17 12:04:10 to 2011-07-21 21:58:51

This 106 hour long measurement shows constant high aerosol loading in the lower 3 km, the plots above show divisions of this long measurement.

21st of July plume

This measurement shows a heavy burden of Aerosol within the first 2 km from midnight (UTC) on the 21st, and this was even visible with the naked eye, this is a photo (time shown on image is local time, 1409 UTC) showing the view looking North West from the roof of the Dunn building, showing the thick haze lying over the city.

The hysplit back trajectory shows that air parcels at 1.5km came directly from the Great Lakes region and passed over Southern Ontaria, where the fire hotspot map shows an area of burning, however air parcels at 500m took a more circuitous path, so it is difficult to judge the actual source region of the plumes.

The satellite images show that upper level clouds where situated above Halifax at the this time, but where not widespread or particularly thick, whereas low level clouds form a sparse but continual blanket over the Maritines, a larger storm system associated with a mid latitude cyclone is situated over Quebec at this time, it was the arrival of that system later in the evening that ended the measurement.


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2011-07-22 03:21:14 to 2011-07-22 11:58:59


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2011-07-22 13:44:52 to 2011-07-23 15:29:36

This measurement, spanning roughly 24 hours from the 22nd to the 23rd of July, has some very interesting patterns visible in the aerosol distribution. At around 1600UTC on the 22nd we see well-defined stratified layers of dense aerosol arriving. HYSPLIT back trajectories for air parcels at the altitudes of the observed aerosol plumes suggest that these aerosols were advected from somewhere along the US-Canadian border. A photograph from Dalhousie at 2100UTC (1800 local time) captures the hazy sky. This haziness might be the low hanging aerosol we observed from lidar measurements. At around 2300UTC, when we see the aerosol layers merge into a large plume below 2km height, we see a similar HYSPLIT back trajectory, although there is a possibility that in this case some of the aerosol was also carried from states such as Louisiana and Arkansas. These HYSPLIT models seem to agree with MODIS hot spot images from three days prior, where we see significant forest fires along the borders of Louisiana, Arkansas and Mississippi. It is quite likely that the boreal biomass aerosols from this region mixed with pollution from the major cities along the US-Canadian border, forming the dense aerosol plume we observed above Halifax. Throughout this measurement the dense aerosol was at very low altitudes with fog present at times, causing the gaps in data and the high noise for the first few hours of the measurement.

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2011-07-23 23:24:34 to 2011-07-26 04:30:15

This measurement spans just over 48 hours and shows low level aerosol loading throughout. There are no significant high altitude plumes. A HYSPLIT trajectory suggests that the aerosols below 4 km from 00:00UTC to 12:00UTC on July 24 most likely originated as anthropogenic pollution in the cities along the US-Canadian border. MODIS shows some burning just north of Saskatchewan, but little elsewhere.

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2011-07-31 08:56:01 to 2011-07-31 23:56:58


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2011-08-01 02:01:19 to 2011-08-02 02:54:43


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2011-08-06 03:29:08 to 2011-08-06 22:55:12


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2011-08-12 14:34:31 to 2011-08-13 00:22:57


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2011-08-13 10:55:47 to 2011-08-15 05:32:30


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2011-08-16 14:15:43 to 2011-08-16 20:23:57


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2011-08-17 12:35:36 to 2011-08-17 19:50:21


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2011-08-21 13:08:20 to 2011-08-22 04:29:49


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2011-08-23 13:19:12 to 2011-08-23 23:57:10


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