winds and calculates an hourly average wind. In AERMET, these 1 hourly averaged winds replace

2 the standard observation time winds read from the archive of meteorological data. This results in

3 a lower number of calms and missing winds and an increase in the number of hours used in

4 averaging concentrations. For more details regarding the use of NWS data in regulatory

5 applications, see Section 8.3.2 of Appendix W. For more information about the processing of

6 NWS data in AERMET and AERMINUTE, see the AERMET (U.S. EPA, 2004c; U. S. EPA,

7 2012b) and AERMINUTE User’s guides (U.S. EPA, 2011d).


9 Since the release of AERMINUTE in 2011, some permitting agencies have expressed

10 concern that the inclusion of AERMINUTE output in AERMOD will lead to an increase in the

11 conservatism of AERMOD output. This perceived increase in conservatism is due to an increase

12 in hours with lower wind speeds input into AERMOD. The purpose of AERMINUTE is not to

13 lead more conservative concentration estimates, but to increase the data quality and

14 representativeness of the meteorological inputs into AERMOD. Concentrations are not

15 calculated for hours with reported calm winds or variable winds. These calm or variable winds

16 are due to the METAR reporting code used to report ASOS observations. In the METAR coding

17 used to report surface observations beginning July 1996, a calm wind is defined as a wind speed

18 less than 3 knots and is assigned a value of 0 knots. The METAR code also introduced the

19 variable wind observation that may include wind speeds up to 6 knots, but the wind direction is

20 reported as missing, if the wind direction varies more than 60 degrees during the 2-minute

21 averaging period for the observation. These are often hours of interest because these are light

22 wind conditions and important for the 24-hour PM2.5 standard. With the use of AERMINUTE,

23 hourly averages can be calculated for those hours with reported calm or missing winds because

24 the 2-minute average winds in the one-minute data files have not been subjected to the METAR

25 coding. In effect, AERMINUTE is obtaining data that was unavailable because of METAR

26 coding, making the meteorological data more representative of the area.



n551 - n552 - n553 - n554 - n555 - n556 - n557 - n558 - n559 - n560 - n561 - n562 - n563 - n564 - n565 - n566 - n567 - n568 - n569 - n570 - n571 - n572 - n573 - n574 - n575 - n576 - n577 - n578 - n579 - n580 - n581 - n582 - n583 - n584 - n585 - n586 - n587 - n588 - n589 - n590 - n591 - n592 - n593 - n594 - n595 - n596 - n597 - n598 - n599 - n600


   Flag of Portugal 


 castellano: DISPER CUSTIC DESCAR RADIA    italiano:     


 français:    português:  






deutsch: DIS CUS  DES  RAD

castellano: DIS CUS DES  RAD   english: DIS CUS DES RAD  


 português: DIS CUS DES RAD   italiano:   DIS CUS  DES RAD


français:  DIS CUS DES RAD