Update below provided by Mike Palecki:
Kelly Redmond announced yesterday the rollout of a newway to access USCRN (and eventually USHCN-M) station data using theWRCCsub-hourly tool.
This is a good platform for visualizing data, especially with regards to grouping multiple variables chosen by a user on one graph, a capability we do not currently have at theUSCRN Web site. Kelly’s example also expressed quite well the power of the triplicate measurement approach promoted by USCRN. The sub-hourly tool also provides great flexibility in calculating accumulated values, and creating tables in a format optimized for a particular user.
In his announcement, Kelly expressed some uncertainties about certain aspects of the USCRN data, which I would like to address below.
Kelly:Some of the info is only updated (either at the platform or at the NCDCingestsite) once an hour. So, for example, wecannot seem to find 5 minute wind mean/max, but only hourly.
Also,there do not seem to be 5-minute winds, but only hourly means, and a single peak gust for the whole hour, rather than for each 5-minute period, the way one would usually do this. Also, there is scalar speed but no direction (we've never been sure why, because thisis sosimple to add), so the wind roses all come up blank. (Wind, and some of the other stuff, is not a primary measurement ... these are intended as diagnostics of temp and precip calues.)
USCRN: Wind data have not been transmitted or archived at the 5-min interval during the history of the program. In addition, wind direction measurements are not taken at USCRN sites. The hourly wind speed observations are not taken at 10 m heights like is typical, but at the height of the air intake to the aspirated platinum resistance thermometers,typically about 1.5 m above the ground. These data are most useful for understanding wind influences on temperature and precipitation measurements, as Kelly mentioned parenthetically, and they are not really comparable to wind data from other networks. In addition, infrared surface temperature and global solar radiation are also only available as hourly means or statistics. In the future, some of these variables may be sampled at the 5-minute rate, but a decision has not been taken on this issue currently.
With regards to data updates, the USCRN station platforms transmit data hourly in three hour blocks of time (redundancy in case of a rare dropped transmission), so true latency depends on the time not only in processing the transmissions, but how far from the beginning of the hour the transmission takes place. USCRN and USHCN-M are essentially near-real-time platforms, but not real time.
Kelly:The nomenclature can be tricky and we are trying to come up with asyntax thatapplies to all types of platforms and data recording methodologies. This is not easy. Forinstance, we may wish to obtain the longterm statistics (max, min, mean) of the maximum minimum 5-minute mean(oversome defined interval), or some such thing.
The basic temperature is called Mean Temperature (because it is a 5-minute mean). We cannot seem to find the max and min temperature within that basic 5-minute reporting interval (which is usually what we call Max Temp and Min Temp). So, what is called Max and Min temp are actually *hourly* max and min of the 12 5-minute mean temps.
USCRN: At the individual platinum resistance thermometer(PRT) level, only the 5-minute mean temperatures are retained and transmitted to NCDC. There is no maximum or minimum for each 5-minute period. However, a maximum or minimum temperature for the hour is calculated not from the125-minute means, but from a 5-minute window that is moved in 10-sec steps. Therefore, the maximum and minimum temperatures for each PRT and hour are based on 360 possible 5-minute intervals during the hour. Finally, the official hourly temperature values for a station are derived by considering observations from all three PRTs in a complicated algorithm that also looks at fan speeds, pair-wise comparisons, and other system indicators, choosing the median of the available measurements.
Kelly:One other thing, for precip, we pull the full precision, and can bin incrementally or in accumulated format, and don't have to worry about 5-minute round off if we don't feel like it.
USCRN: Fullprecision being pulled from USCRN is tenths of millimeters. In the WRCC product, many decimal places are preserved, related to the conversion from metric to English units.
Kelly:There are many ways to create an hour from 5-minute data, many ways of creating a day from sub-daily or sub-hourly data, and many ways of creating a month or a year, as well. Our goal is to eventually make this as explicit as possible, and also leave all these decisions to user control.
USCRN: It is useful for users to have flexibility in calculating accumulated valuesfrom5-minute data. However, many users simply need an hourly, daily, or monthly value that is provided without need for considering calculation rules. We will be working with the WRCC to provide the option for users to select the hourly, daily, and monthly values for certain variables as they are directly calculated by USCRN. For the moment,users may find some small differences between USCRN hourly, daily, and monthly observations and the ones calculated directly by the sub-hourly tool at WRCC.
We appreciate this effort to move USCRN and USHCN-M data to the user community, including the work done at the WRCC, and hourly USCRN products now available at the MRCC. We will work to coordinate activities so as to ensure data are comparable through these various portals, and that the user may choose the interface that is most convenient for a given purpose.
Mike Palecki, USCRN