TITLE: Mesonet Automated Weather Observing System (AWOS) Iowa 1-min Data [JOSS] CONTACTS: Steve Williams UCAR/JOSS P.O. Box 3000 Boulder, CO 80307-3000 phone: 303-497-8164 email: sfw@ucar.edu 1.0 DATA SET OVERVIEW This data set contains 1-minute resolution surface meteorological data from the Automated Weather Observing System (AWOS) stations located across the state of Iowa. This data set covers the period from 19 May through 07 July 2003. The data are in ASCII format. 2.0 INSTRUMENT DESCRIPTION 2.1 Instrumentation information Some information on AWOS can be found at the Federal Aviation Administration Automated Weather Sensors page at: http://www2.faa.gov/asos/ Information on the Iowa AWOS can be found at the Iowa Environmental Mesonet AWOS page at: http://mesonet.agron.iastate.edu/AWOS/ 2.2 Station Locations These station locations are taken from the AirNav database (http://www.airnav.com). Elevations are in meters. City ID State Latitude Longitude Elev ---------------------------------------------------------------- ALGONA AXA IA 43.0779106 / -94.2719928 371.6 ANKENY IKV IA 41.6912856 / -93.5663033 277.4 ATLANTIC AIO IA 41.4072672 / -95.0469064 360.3 AUDUBON ADU IA 41.7013756 / -94.9205417 392.3 BOONE BNW IA 42.0495694 / -93.8475722 353.6 Carroll CIN IA 42.0461944 / -94.7890000 367.0 CHARITON CNC IA 41.0196239 / -93.3596803 320.0 CHARLES CITY CCY IA 43.0726086 / -92.6107783 342.9 CLARINDA ICL IA 40.7217836 / -95.0264267 302 CLARION CAV IA 42.7419439 / -93.7589094 354.2 COUNCIL BLUFFS CBF IA 41.2594722 / -95.7599722 381.9 CRESTON CSQ IA 41.0214614 / -94.3633192 394.4 DECORAH DEH IA 43.2755014 / -91.7393739 352.7 DENISON DNS IA 41.9864325 / -95.3807208 388.9 FAIRFIELD FFL IA 41.0533242 / -91.9789233 243.5 FORT MADISON FSW IA 40.6592625 / -91.3268175 220.7 HARLAN HNR IA 41.5843889 / -95.3396389 375.2 KEOKUK EOK IA 40.4599078 / -91.4285011 204.5 KNOXVILLE OXV IA 41.2988856 / -93.1138156 282.9 LeMARS LRJ IA 42.7780178 / -96.1936894 364.5 MONTICELLO MXO IA 42.2240453 / -91.1658219 253.9 Mount Pleasant MPZ IA 40.9466139 / -91.5110750 223.7 MUSCATINE MUT IA 41.3678633 / -91.1482164 167.0 NEWTON TNU IA 41.6744297 / -93.0217292 290 OELWEIN OLZ IA 42.6808447 / -91.9744783 328.0 ORANGE CITY ORC IA 42.9902644 / -96.0627967 431 Pella PEA IA 41.4000667 / -92.9458833 269.7 RED OAK RDK IA 41.0105278 / -95.2598611 318.2 SHELDON SHL IA 43.2083936 / -95.8334331 432.5 SHENANDOAH SDA IA 40.7514817 / -95.4134722 296.0 STORM LAKE SLB IA 42.5971944 / -95.2406667 453.5 Vinton VTI IA 42.2186261 / -92.0259281 258 WASHINGTON AWG IA 41.2761008 / -91.6734439 229.8 WEBSTER CITY EBS IA 42.4366389 / -93.8688611 341.7 3.0 DATA COLLECTION AND PROCESSING UCAR/JOSS conducted no processing or quality control on these data. Further information is also available at the FAA Automated Weather Sensor Home Page: http://www2.faa.gov/asos/index.htm 4.0 DATA FORMAT AND FILE NAMING 4.1 Data Format ADU 2002-06-02 00:02 92 54 11 130 0 10 0 29.78 9000 1 0 0 0 0 ADU,AUDUBON,41.7,-94.92,2003-06-02 00:00,70,49,9,100,0,10,0,29.95,25500,255,2550 0,255,25500,255, ADU - station identifier AUDOBON - station name 41.7 - latitude -94.92 - longitude 2003-06-02 - yyyy-mm-dd 00:00 - hh:mm (UTC) 70 - temperature in Deg F 49 - dew point temperature in Deg F 11 - Wind Speed (knots) 100 - Wind Direction 0 - Wind Gust (knots) 10 - Visibility (statute miles) 0 - Hourly Precipitation Accumulator (inches; reset to 0.0 at 56 minutes after each hour) 29.95 - Altimeter (inches of mercury) 25500 - Cloud Deck 1 Height 255 - Cloud Deck 1 Coverage 25500 - Cloud Deck 2 Height 255 - Cloud Deck 2 Coverage 25500 - Cloud Deck 3 Height 255 - Cloud Deck 3 Coverage 4.2 File Naming Conventions ADU_20030602.txt ADU is the station identifier (see station list above) 20030602 is yyyymmdd 5.0 DATA REMARKS The Iowa Mesonet receives 1 minute observations from the state Department Of Transportation (DOT) in Iowa, which owns a network of 37 AWOS sensors that report their data in METAR format (via a private company) to the world via the Federal Aviation Administration (FAA) NADIN network and then to the Iowa Mesonet via the National Weather Service (NWS). Dew point readings from many of these sites have been reading too high. These errors appear to be a result of incorrect calibration. Minute-by-minute observations around the time onsite calibration is believed to occur show a gap in the observations. This is believed to be when the site is being taken offline for calibration. However, this cannot be confirmed because calibration information is not publicly released. For example: [times are in UTC, TMPF -> Air Temperature in F, DWPF -> Dew Point in F] Orange City (KORC) UTC VALID TIME |TMPF|DWPF 2003-11-06 17:59 | 37 | 19 2003-11-06 18:00 | 37 | 19 2003-11-06 18:01 | 37 | 19 2003-11-06 18:14 | 39 | 29 <-- 10 degree jump 2003-11-06 18:15 | 39 | 30 2003-11-06 18:16 | 39 | 30 Sheldon (KSHL) UTC VALID TIME |TMPF|DWPF 2003-11-06 18:53 | 36 | 22 2003-11-06 18:54 | 36 | 22 2003-11-06 18:55 | 36 | 22 2003-11-06 19:20 | 39 | 29 <-- 7 degree jump 2003-11-06 19:21 | 39 | 29 2003-11-06 19:22 | 39 | 29 Harlan (KHNR) UTC VALID TIME |TMPF|DWPF 2003-10-02 17:42 | 57 | 24 2003-10-02 17:43 | 57 | 25 2003-10-02 17:44 | 57 | 25 2003-10-02 18:08 | 63 | 36 <-- 11 degree jump 2003-10-02 18:09 | 63 | 36 2003-10-02 18:10 | 63 | 36 Denison (KDNS) UTC VALID TIME |TMPF|DWPF 2003-10-02 19:33 | 64 | 32 2003-10-02 19:34 | 64 | 32 2003-10-02 19:35 | 65 | 33 2003-10-02 19:48 | 67 | 37 <-- 4 degree jump 2003-10-02 19:49 | 66 | 37 2003-10-02 19:50 | 66 | 37 Looking at a current surface plot, one can easily see the high dew points in Iowa from the AWOS sensors. Unfortunately, with such a high concentration of AWOS versus ASOS sensors in Western Iowa, some pollution can be seen to show up in various model data assimilation systems. For instance: http://downdraft.caps.ou.edu/wx/p/r/spmeso/adas/td.png The Iowa Mesonet continues to request that this problem be fixed. As of the time of this data, it has not. 6.0 REFERNCES None.