Met Data

1.

Why should I use MM5 data?

There are several reasons why you may want to use MM5 meteorological data:

• There is no station data available in your area
• There is no representative station data available for your site
• The available station data is out of date
• The available station data is not very accurate (e.g. poor treatment of calms)
  
  

2.

How is MM5 data different from station data with regards to low wind conditions?

The majority of meteorological data is collected from airport met stations.  An airports primary concern is high wind speeds which may affect aircraft; due to this, low wind speeds are often not recorded with sufficient accuracy for air dispersion modeling purposes. This is of particular concern because low wind speeds are often responsible for the highest concentrations.
MM5 data does not have this issue as all wind speeds are calculated with equal accuracy.

3.

What is the period of MM5-Processed Met Data provided?

Lakes Environmental can provide one or multiple years of MM5-processed met data, depending on what your requirements are.  Surface and upper air meteorological data are retrieved from a single grid point of the MM5 model output nearest to a user-specified location.  The MM5 model employs the Universal Time Coordinate (UTC) system, surface data will be converted to the local time zone, and upper air data will be left in UTC, as expected in AERMET.

4.

What information is needed for placing an order for MM5-processed meteorological data?

When requesting a quotation or placing an order, the following information should be provided regarding the requested location:

• Latitude and longitude for the center point of your site
• City name and country name
• Time zone
• Time period required

Please visit our MM5 met data order page for further information.

5.

What are the fees for an order?

You can either contact us at sales@weblakes.com for pricing or fill out our comprehensive form on our MM5 met data order page to receive a quotation.

6.

How long will it take to get my order?

This will depend on the number of orders we are currently processing, and the period the MM5 data is to cover.  We will give you an estimated delivery date at time of order.

7.

What is the anemometer height/reference height of the surface station?

The anemometer height is calculated by our meteorologist when processing the MM5 data.  You will be provided with the anemometer height once your data is complete.

8.

How does MM5 produce the wind field?

The MM5 data that we provide to our clients uses meteorological data provided by a vast network of meteorological stations. It then uses conservation equations to calculate how the wind field would behave in between met stations.

9.

What boundary conditions are used to generate the wind fields in MM5?

MM5 uses 1km by 1km gridded land use to estimate surface properties (surface boundary conditions). It also uses the pre-processed wind field for the global weather simulation to obtain the initial time boundary condition at t=0 and at other times as well.

FAQs for CALPUFF Specific MM5 Data

10.

What is the difference on wind fields provided by MM5 and CALMET?

MM5 uses all the conservation equations and has more refined parameterization for processes that cannot be simulated directly. For these reasons MM5 is classified as a prognostic model. CALMET uses a simple mass conservation approach and does not solve the momentum, energy, or moisture conservation equations. CALMET is classified as a diagnostic model.

11.

If MM5 is so much better than CALMET, should I always use MM5 for my CALPUFF modeling?

No. Because MM5 solves the coupled set of conservation equations, it requires a lot of computer resources, time, and experience to run. CALMET is a much simpler model and runs much faster than MM5. Our experience indicates that CALMET can run more than an order of magnitude faster than MM5 in many cases. We recommend that MM5 be used only for projects that require much better accuracy in the wind field.