Information on the NILU Forecast Products

General Info

Five-day forecasts are provided to support scientific field campaigns. Normally, they are updated once a day, but during large experiments the system can be run four times a day. If you would like to have the products available more often than once a day during your field mission, please contact Andreas Stohl (Tel: +47 6389 8035) or Sabine Eckhardt (Tel: +47 6389 8187) to discuss possibilities.

Meteorological Fields

The meteorological fields (geopotential height at 500 hPa, surface pressure, equivalent potential temperature, CAPE, and vertical velocity at 500 hPa) are extracted from the Global Forecast System (GFS) data of the National Centre for Environmental Prediction (NCEP)


The trajectory forecasts are calculated with the trajectory model FLEXTRA based on Global Forecast System (GFS) data of the National Centre for Environmental Prediction (NCEP). 8-day backward and 4-day forward trajectory forecasts are provided for two locations. Trajectories are started every 500 m in the vertical and every 3 hours.

For the four-day warm conveyor belt trajectories, trajectories are started at 500 m in the domain 110 deg W to 50 deg W and 20 deg N to 60 deg N. Only those trajectories are displayed that ascent more than 5000 m and travel north-eastwards within the four days.

Emission Tracer Forecasts

Emission tracer forecasts are calculated with the particle dispersion model FLEXPART based on Global Forecast System (GFS) data of the National Centre for Environmental Prediction (NCEP). Tracer masses are carried by particles following trajectories calculated using the GFS winds and stochastic components for turbulence and convection. Tracer forecasts are run separately for anthropogenic emissions from Asia, Europe and North America. For each of these forecasts, three tracers are available: carbon monoxide, nitrogen oxides (expressed as NO2), and sulfur dioxide (including direct emissions of sulfate). These species are run as passive tracers for a duration of 20 days, after which tracer particles are dropped from the simulation. In addition, a biomass burning CO tracer is available; the emission algorithm ingests actual information on MODIS fire detections, landuse information, and emission factors.

As the emission basis, the EDGAR version 3.2 fast track inventory for the year 2000 with a resolution of 1 degree is used, excecpt for most of North America where the inventory of Frost and McKeen (2004) is used. This inventory is based on the U.S. EPA NEI-99 inventory (National Emissions Inventory, base year 1999, version 3) and has an original resolution of 4 km, plus point sources. For initializing FLEXPART, the high resolution has been kept for high-emission grid cells and strong point sources. Weaker sources were aggregated to coarser resolution. For Mexico City, an inventory provided by Jerome Fast was used, which has a resolution of 4.5 km. Again, the high resolution was kept for high-emission grid cells.

The different regional tracers are available for the following computational domains:
70 W - 74 E, 30 N - 90 N at a resolution of 0.6 deg.
0 E - 30 E, 65 N - 90 N at a resolution of 0.25 deg.

Quasi-Lagrangian flight opportunities

IMPORTANT NOTE: this product is not active at this time

Quasi-Lagrangian flight opportunities into the Mexico City plume are calculated for the aircraft involved in the MIRAGE and IMPACT campaigns. Currently, these are the NCAR C-130, the NASA DC-8, and the DLR Falcon. A paper describing the forecasts for such a Lagrangian campaign in detail has recently been published in ACP.

The orange dots in the figures show the assumed bases of three aircraft and orange circles indicate their ranges of operation. The centroid locations of air parcels selected as Lagrangian opportunities are presented as dots superimposed on maps of the total Mexico City CO tracer columns. The dots are colored according to the actual CO tracer mixing ratio in the air parcel using the same color scale as used for the total columns, but scaled to a maximum value of 249 ppb. Note, therefore, that the colors of the dots do not match with the colors of the background contours, which show total columns rather than mixing ratios. The number drawn on top of each dot indicates the air parcel's centroid altitude in kilometers. The five best Lagrangian opportunities are drawn as bigger circles surrounded by a white ring (sometimes only few are visible which cover the others). The trajectories of the 50 best cases are also shown as black lines.

If you have any questions about the GFS modelling products please contact Sabine Eckhardt or Andreas Stohl.

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