2020 Infra Surface Weather Observations

Surface Weather Observations Comparison of Various Observing Systems

Scott Landolt & Matthias Steiner National Center for Atmospheric Research [email protected]

USHST Infrastructure Summit 12 – 13 March 2020 in Washington, DC

Station Type Frequency of Reports Automated Surface 5 minutes Observing System (ASOS) (limited access to 1 minute data) Automated Weather 20 minutes Observing System (AWOS) 15 minutes (standard), can be Road Weather Information more frequent but varies state to System (RWIS) state and even site to site 5 – 15 minutes, can vary from Mesonet station to station

Iowa station network

Weather Variable ASOS AWOS RWIS Mesonet Temperature X X X X Relative X X X X Humidity/Dewpoint

Wind Speed/Direction X X X X

Barometric Pressure X X X X

Ceiling Height X X X X Visibility X X X X Present Weather X X X X Precipitation X X X X Accumulation Road Condition X X X X

X – All Stations Report X – Some Stations Report X – No Stations Report

Station Type Siting Areal Representativeness Automated Surface Miles (varies depending on Airport grounds, unobstructed Observing System (ASOS) local conditions & weather) Automated Weather Miles (varies depending on Airport grounds, unobstructed Observing System (AWOS) local conditions & weather) Next to roadways, can be in canyons, valleys, mountain 500 feet to miles (varies Road Weather Information sides, near rivers/lakes, on depending on local System (RWIS) bridges, etc. Terrain and local conditions & weather) features can play significant role in observations Farmland/ranchland, generally Miles (varies depending on Mesonet outside of city influences local conditions & weather)

© 2020 University Corporation for Atmospheric Research 4 Scale Comparison • Surface stations cover synoptic scale • Satellite covers meso scale • Radar covers storm scale • Combined they capture processes at 10s of minutes & 100s of meters

- except in complex terrain Radar & urban environments Satellite ASOS

ASOS, AWOS & MesoWest station separation distances

Networks • Network availability, type of sensors, & station density varies notably among locations

Station Type Sensors Nearly all sensors standardized Automated Surface from site to site; FAA/NWS Observing System (ASOS) owned and maintained Four different companies authorized to install/maintain; Automated Weather sensors standardized within Observing System (AWOS) companies but not between companies Limited to no standardization, Road Weather Information even within individual state System (RWIS) sites Sensors typically standardized Mesonet within each network but not between networks

The four vendors for AWOS are: 1) All Weather Inc. (AWI) 2) Optical Scientific Inc. (OSI), formerly Belfort Instrument Co. 3) Mesotech International 4) DBT Transportation Services LLC, formerly Vaisala

ASOS • All sensors checked twice per year (unless a sensor is flagged as needing maintenance) AWOS • All sensors checked twice per year (unless a sensor is flagged as needing maintenance) RWIS • Variable, may be sensor dependent • Could be weekly to yearly maintenance intervals Mesonet • Variable, typically six months to one year.

Previous Studies ASOS Visibility Sensor • Prior studies conducted utilizing non-collocated sensors - several RWIS sites surrounding ASOS site - terrain/altitude differences can have significant impacts AWOS Visibility Sensors (two examples of four) on non-collocated sites - lack of standardized sensors means prior study results may only be valid for subset of RWIS stations Future Studies RWIS Visibility Sensors (two examples of many) • Need co-located sensors • Need to understand data quality issues as well - both at sensor & network levels

Links to Key Documents • https://ops.fhwa.dot.gov/publications/ess05/ess05.pdf • https://www.ncdc.noaa.gov/data-access/land-based-station-data/ land-based-datasets/automated-weather-observing-system-awos • https://www.ofcm.gov/meetings/atd/gmu2016/pdf/8%20Joseph.pdf Scientific Publications • Several conference & some peer-reviewed comparison studies • Some technical reports • Few textbooks on atmospheric measurements Other Relevant Websites • https://madis.ncep.noaa.gov • https://wxde.fhwa.dot.gov • https://mesowest.utah.edu • http://mesonet.agron.iastate.edu/info/nni.phtml