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### Liljegren, Jennifer

From: DERF, MARK <MDERF@idem.IN.gov>

Sent: Monday, January 25, 2016 4:28 PM

To: Portanova, Mary; Robinson, Randall

Cc: NEYMAN, MARK; Mosier, Michael; Sherman, St even; Jones, Cody C; Summerhays, John;

Liljegren, Jennifer

Subject: Evansville anemometer height

Attachments: NOAA_NWS_email_thread_Evansv ille_anemometer_height.docx;

LADCO_states_email_thread_Eva nsville_anemometer_height.docx

Follow Up Flag: Follow up

Flag Status: Completed

All,

After a conference call with Region 5 in October 2015 concerning Indiana’s 1

‐ hour SO2 consent decree submittal, this

issue concerning the inconsistency in the anemometer height at the Evansville Regional Airport automated surface

observing system (ASOS): Identifier WMO 72432/WBAN 93817 was brought up. We researched several National

Weather Service (NWS) and National Oceanic and Atmospheric Administrative (NOAA) websites as well as past email

threads within the LADCO states and Region 5 from July 2010 that talked about anemometer heights. Based on our

research, there appears to be varying heights listed for the Evansville Regional Airport ASOS anemometer. We have

seen 33, 26, 30 feet from numerous documents concerning the meteorological station at the Evansville Regional

Airport. This may be due to the site being moved several times over the years. As mentioned in the email thread

initiated by Region 5 and Indiana in July 2010 (attached), NWS had recommended states were to assume 33 feet (10

meter) anemometer heights unless other information was provided. With varying heights provided, it appeared that

using a 33 feet anemometer height was the best approach.

Attached is the email thread with NOAA and NWS staff that helped us answer this question. I sent an email to

nws.answers@noaa.gov explaining the situation and after several forwards to appropriate NWS and NOAA staff, a blue

print of the relocation of the meteorological station was provided, showing the ground elevation of 410 feet and the

sensor elevation of 440 feet. As further explained from a recent photo of the current meteorological station, the sensor

is located on a “S” arm with the difference in sensor to ground elevation of 30 feet measured at the cross arm. With the

anemometer located on the top of the “S” arm, the 33 feet (10 meter) height of the anemometer would appear to be

correct. Therefore, IDEM feels 10 meters best represents the anemometer height at Evansville Regional Airport and

Indiana’s modeling for AB Brown’s emission limits established in their Commissioner’s Order is accurate and acceptable.

Due to the inconsistencies found in our research, the need for a central location for important information that goes

into the AERMET, AERSURFACE and other utility programs that are used to create the meteorological files is needed to

promote consistency among all the states in their creation of meteorological data.

If you have any additional questions concerning this issue, please contact me. Thank you.

Mark Derf

Section Chief

– Technical Support and Modeling

Indiana Department of Environmental Management

Office of Air Quality

100 North Senate Avenue

Indiana, IN 46206

‐ 2251

Phone 317 233

‐ 56822 Fax 317 233

‐ 2342

mderf@idem.IN.gov