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IMPROVE Optical Data

The raw IMPROVE transmissometer and nephelometer data available in ASCII files.  See the Tools section for data processing tools and aggregation algorithm.

WARNING!

The nephelometer and transmissometer data found on this website are preliminary, and have only undergone basic QA procedures.  There are known minor issues with both the nephelometer and transmissometer data sets, including the following:

 

  1. Some transmissometer Bext values are reported with no interference (validity code = 0), even though there is no corresponding RH value to determine whether RH interference flags should have been applied.  These values should be reported as ‘suspect’ (validity = 9).
  2. Validity codes other than those found in the transkey and nephkey documents (i.e. 5 and 8) occur in some older data.  Treat these observations as ‘suspect’.
  3. Small numbers of outlier Bext/Bsp data points occur at most sites.  These values are usually islands of Bext/Bsp values in between several interference-flagged observations.  The points are marked as ‘valid’, but should be used with caution.
  4. Zero values for transmissometers are inherently uncertain due to changes in lamp brightness and other factors.  Trends and discontinuities in low Bext values should be considered as having likely been caused by instrument related changes.
  5. Nephelometer Bsp values are generated by subtracting a fixed Rayleigh scattering value for each site from each scattering measurement.  The variability of actual ambient Rayleigh scattering coupled with the nephelometer’s inherent uncertainty will lead to frequent negative Bsp values that are valid.
  6. Many sites have anomalous temperature readings reported as valid which are clearly unrealistic.  Use caution when examining temperature effects.
  7. Relative humidity values before about 1993 are subject to significant uncertainty, and should be used with caution.  After about 1993, the RH measurements above about 95% still have significant uncertainty. In nephelometer data sets, many RH values greater than 100% are reported as valid.

 These issues are being addressed, and may be resolved in future data releases.

IMPROVE Network Metadata - Monitoring site information including site location, history, pictures, and air quality variables samples.

Nephelometer Data Description - Description of the data file formats and validity and inference codes for the nephelometer data

Transmissometer Data Description - Description of the data file formats and validity and inference codes for the Transmissometer data

Warnings on the Use of Transmissometer Data to Analyze Long-Term Visibility Trends - Describes some of the limitations and issue concerning the transmissometer data and problems with using the long-term transmissometer records for trend analysis. 

Model LPV-2: Long Path Visibility Transmissometer - Technical Manual for Theory of Operation and Operating Procedures.

Model NGN-2: Open-Air Integrating Nephelometer - Technical Manual for Theory of Operation and Operating Procedures.

Reprocessing of all 1993-2004 Nephelometer data - In August, 2004, Air Resource Specialists (ARS) reevaluated the scattering properties of the SUVA span gas used in processing Optec NGN-2 nephelometer data.  This resulted in changing the Rayleigh multiplier it uses for SUVA to 7.25 from the value 7.1 which has been in use since 1993.  This new multiplier effectively increases the NGN-2 scattering coefficient by approximately 2.5%.  All historical nephelometer data has been reprocessed and the data posted to the IMPROVE website on July 18, 2005.

Nephelometer Data

(Click on the site location code to download its data in a PKzip file)
Location Site Name Lat (degrees) Lon (degrees) Elevation (m) Start Date End Date Sponsor
ACAD1 Acadia National Park 44.37 -68.26 122 6/1/1993 12/31/1997 NPS
ACAD2 Acadia National Park 44.37 -68.26 158 10/1/1997   NPS
BIBE1 Big Bend National Park 29.30 -103.18 1052 1/1/1998   NPS
BOWA1 Boundary Waters Canoe Area 47.95 -91.50 515 4/1/1993 9/30/1997 USFS
CHIR1 Chiricahua National Monument, AZ 32.01 -109.39 1570 12/17/2003    NPS
COGO2 Columbia River Gorge Natural Scenic Area 45.57 -122.21 243 6/1/2001 3/9/2005  USFS
COHU1 Cohutta 34.79 -84.62 743 5/24/2000   USFS
CORI1 Columbia River Gorge 45.66 -121.00 198 9/1/1993 3/9/2005 USFS
DOSO1 Dolly Sods /Otter Creek Wilderness 39.10 -79.43 1175 3/1/1993 12/31/2006 USFS
GICL1 Gila Wilderness 33.22 -108.23 1783 3/1/1994 11/1/2003 USFS
GRSM1 Great Smoky Mountains National Park 35.63 -83.94 793 3/1/1993   NPS
HANC1 Hance Camp at Grand Canyon NP 35.97 -111.99 2266 12/1/1997   NPS
INGA1 Indian Gardens 36.08 -112.13 1166 6/1/2004   NPS
JARB1 Jarbidge Wilderness 41.89 -115.43 1889 3/1/1993 9/30/1997 USFS
JARI1 James River Face Wilderness, VA 37.63  -79.51  299  12/01/2000 11/1/2003  USFS
LOPE1 Lone Peak Wilderness 40.44 -111.71 1745 9/1/1993 9/4/2001 USFS
LYBR1 Lye Brook Wilderness 43.14 -73.13 1010 6/1/1993 11/1/2003 USFS
MACA1 Mammoth Cave National Park 37.22 -86.07 219 3/1/1993 8/31/1997 NPS
MACA2 Mammoth Cave National Park 37.13 -86.15 236 6/1/1997   NPS
MORA1 Mount Rainier National Park 46.76 -122.12 421 12/1/1992   NPS
MOZI2 Mount Zirkel Wilderness 40.54 -106.68 3224 6/1/1994   USFS
MOZI1 Mount Zirkel Wilderness 40.46 -106.74 3215 9/1/1993 7/16/1994 USFS
NACA1 National Capitol - Central, Washington D.C. 38.9 -77.04

514

7/1/2003

  

 
OKEF1 Okefenokee National Wildlife Refuge 30.74 -82.13 47 12/1/1992 8/31/1997 FWS
PEFO3 Petrified Forest National Park, AZ 34.91 -109.80  1690  11/18/2003   NPS
SHEN1 Shenandoah National Park 38.52 -78.43 1073 9/1/1996   NPS
SHRO1 Shining Rock Wilderness 35.38 -82.77 1612 6/1/1994 9/21/1999 USFS
SNPA1 Snoqualamie Pass, Snoqualamie N.F. 47.42 -121.43 1152 9/1/1993 5/15/2001 USFS
THSI1 Three Sisters Wilderness 44.29 -122.04 881 9/1/1993 5/15/2001 USFS
VIIS1 Virgin Islands National Park 18.33 -64.79 46 3/1/1998 9/30/2005 NPS
UPBU1 Upper Buffalo Wilderness 35.83 -93.20 720 12/1/1992 11/30/1997 USFS
WIMO1 Wichita Mountains 34.73 -98.71 510 3/1/2001    FWS

                       Non-IMPROVE Nephelometer Data
Location Site Name Lat (degrees) Lon (degrees) Elevation (m) Start Date End Date Sponsor
BLIS1 D.L. Bliss State Park, NV 38.98 -120.10 

2116 

8/12/1996

3/31/2006

TRPA
CHPA1 Children's Park - Tucson, AZ 32.3 -110.98

704

7/1/2003

  

ADEQ
CEBL1 Cedar Bluffs 38.77 -99.76

689

9/1/2004

  

CENRAP

CRAY1 Craycroft (Tucson urban) 32.2 -110.88

809

1/1/2001

  

ADEQ
DYRT1 Dysart - Phoenix, AZ 33.64 -112.34

364

7/16/2003

  

ADEQ
EBFO1 Edwin B. Forsythe National Wildlife Refuge 39.47 -74.45

5

3/1/1993

 5/31/1994

FWS

ESTR1 Estrella Mountain Park, AZ 33.39 -112.39

290

1/1/2003

  

ADEQ
GRER1 Greer 34.06 -109.44

2513

4/1/2001

  

ADEQ
GRGU1 Great Gulf Wilderness 44.31 -71.22

439

6/1/1995

3/31/2005

USFS
GRVS1 Green River, WY 41.84 -109.61

1951

7/22/1996

 10/17/2000

WYOVIS
HUMB1 Humbolt 33.998 -111.8

1586

3/1/1997

 11/25/2003 

ADEQ
IKBA1 Ike's Backbone 34.34 -111.68

1303

6/1/2001

  

ADEQ
LTBV1 Lake Tahoe Boulevard, NV 38.95 -119.96

1902

2/13/1996

 9/30/2004

TRPA
LTBV2 Lake Tahoe Boulevard, NV 38.95 -119.96

1902

10/01/2005

 3/31/2006

TRPA
MAYV1 Mayville 43.44 -88.53

306

10/1/2001

 12/31/2006

WISC-DNR
MAZA1 Mazatzal 33.91 -111.41

2164

3/1/1997

 8/29/2000

ADEQ
MILW1 Milwaukee, WI 43 -87.89

193

6/1/2004

 6/30/2006

WISC-DNR
MCFD1 McFadden 33.91 -110.97

2175

10/1/1997

 2/1/2000

ADEQ
MUSR1 Muleshoe 32.33 -110.23

1402

07/1/1997

 6/30/2005 

ADEQ
NEBR1 Nebraska Forest, NE    

 

08/10/2005

  

CENRAP
ORPI1 Organ Pipe National Monument, AZ 31.95 -112.8

366

4/1/1997

  

ADEQ
PHON1 Phoenix 33.5 -112.1

372

4/1/2002

  

LADCO
ROMA1 Cape Romain 40.36 -105.58

668

6/12/2003

  

ADEQ
RUCA1 Rucker Canyon 31.5 -109

1637

10/1/1997

 5/23/2001

ADEQ
QUAK1 Quaker City, OH 39.94 -81.34

372

1/1/1999 1/14/2004  

EPA
QUVA1 Queen Valley - Superstition Wilderness, AZ 33.29 -111.29

668

6/1/2003  

ADEQ

SIAN1 Sierra Ancha 34.09 -110.94

1595

7/1/2000

  

ADEQ
SENY1 Seney National Wildlife Refuge 46.29 -85.95

216

1/1/2002

 6/30/2006

LADCO
SYCA1 Sycamore canyon 35.14 -111.97

2126

7/1/1998

  

ADEQ
TUCN1 Tucson Central, AZ 32.24 -110.96

745

4/1/1997

  

ADEQ
TUMO1 Tucson Mountain 32.28 -111.17 

754 

12/30/1996

 11/07/2001

ADEQ
TUMO2 Tucson Mountain - Saguaro National Monument, AZ 32.28 -111.17 

754

11/8/2001

  

ADEQ
VEIX1 Vehicle Emissions - Phoenix, AZ 33.46 -112

345

7/1/2003

  

ADEQ

Transmissometer Data

All data have only be QA'ed to Level 1 and should be considered preliminary.  They should only be used after careful scrutiny and reconciliation with aerosol and nephelometer data.

Prior to using these data please see:  Warnings on the Use of Transmissometer Data to Analyze Long-Term Visibility Trends

In August 2006 the 1986-2004 transmissometer data were reprocessed and re-submitted.  Details on the reprocessing can found here.

(Click on the site location code to download its data in a PKzip file)

Location Site Name Receiver Transmitter Mean Elevation Elevation Angle (deg) Distance Start Date End Date Sponsor
Lon (deg) Lat (deg) Elevation (m) Bearing (deg) Lon (deg) Lat (deg) Elevation (m)
ACAD1 Acadia National Park -68.26 44.37 134 134 -68.23 44.35 466 300 5 4 9/1/1987 8/31/1993 NPS
BADL1 Badlands National Park -101.90 43.79 806 239 -101.95 43.77 805 805 -0.01 4.151 12/1/1987 9/30/2006 NPS
BAND1 Bandelier National Monument -106.26 35.78 2011 315 -106.30 35.81 2143 2077 1.65 4.058 9/1/1988 9/30/2006 NPS
BRID1 Bridger Wilderness -109.79 42.93 2390 11 -109.77 42.97 2568 2479 2.01 5.083 9/1/1988 12/31/2006 USFS
CANY1 Canyonlands National Park -109.82 38.46 1806 73 -109.75 38.48 1774 1790 -0.29 6.426 12/1/1986 9/30/2006 NPS
CHIR2 Chiricahua National Monument -109.39 32.01 1567 97 -112.54 32.01 1682 1625 2.07 3.180 12/1/1998 6/30/2001 NPS
CHIR1 Chiricahua National Monument -109.39 32.01 1567 84 -109.32 32.01 2235 1901 6.26 6.123 12/1/1988 2/28/1999 NPS
GLAC1 Glacier National Park -113.94 48.56 968 232 -113.99 48.53 975 972 0.08 5.276 12/1/1988 9/30/2006 NPS
GRBA1 Great Basin National Park -114.21 38.99 2130 315 -114.24 39.02 2365 2248