A weeks worth of data from my new MMTS unit

Last week you may recall that I posted about my new self contained MMTS unit that I’m experimenting with as a possible replacement of as a check system for NOAA’s existing MMTS. Below you can see my test setup in my back yard.

This is a custom wireless MMTS with internal data logger that I built, view from my backyard.

The most valuable thing about my version of MMTS is that it is cable free, can be placed anywhere, and can log data automatically for days, weeks of even months, depending on the interval. It also logs relative humidity, and dewpoint.

Here is what the internal sensor package/datalogger unit looks like when not installed in the infrared radiation shield:

When you are ready to download the data for analysis, all you have to do is unscrew the head, connect the USB cable to the datalogger and to your laptop as I did shown below. This easy ability to plug into a laptop to download data and start a new data logging run in under 5 minutes makes the design very suitable for field work away from networking and AC power.

Data transfer for the one week of data I recorded only took about two seconds.

I have plotted all three measurements from the sensor below:

Click for a larger image:

And here is the raw data file, with data logged every minute, in comma delimited format if you wish to plot it, a key to the values is on line1 of the file. jan20-2008.txt

For comparison, I have logs online from the Davis Vantage Pro2 weather station shown in the background

Jan 13th http://www.bidwellranchcam.com/data/011308hd.txt
Jan 14th http://www.bidwellranchcam.com/data/011408hd.txt
Jan 15th http://www.bidwellranchcam.com/data/011508hd.txt
Jan 16th http://www.bidwellranchcam.com/data/011608hd.txt
Jan 17th http://www.bidwellranchcam.com/data/011708hd.txt
Jan 18th http://www.bidwellranchcam.com/data/011808hd.txt
Jan 19th http://www.bidwellranchcam.com/data/011908hd.txt
Jan 20th http://www.bidwellranchcam.com/data/012008hd.txt

I also prepared a comparison file showing how the New MMTS and the nearby Davis Weather Station max/min readings compare. There is good agreement, with some slight differences that could be related to observation height differences between the two sensor sets.

See the comparison file: newmmts_hi-lo_compare.txt

How not to measure temperature, part 47

Ajo, AZ USHCN Station photographed by Bob Thompson

But wait, theres more:

I’ve posted about stations that had proximity to a/c units before, but this one is of particular interest since it has dual a/c units to its west and east. Given that wind tends to hug the side of a building (laminar flow) this provides potential for transferring waste heat from the a/c units to the MMTS sensor. Of course there is the bias based on the MMTS sensor proximity to the building, and the wall corner that it is built into will like provide a night time IR radiative bias near the sensor also. Combined, this station warrants a CRN 5 rating.

Honestly, I don’t know how the COOP manager for the NWS would allow such a poor placement.

This station has an incomplete temperature record, since it apparently has gone through some moves, but the latter part of its graph at the current location seems to confirm a step bias due to the placement.

Bob indicates from the curator that teh station used to be on a nearby hilltop, but was moved, but according to NCDC’s MMS records for COOP station # 020080 it remains on the hilltop today:

LOCATED ON KNOLL SURROUND BY FLAT TERRAIN. KNOLL & SURROUND AREA PARTIALLY COVERED DESERT SCRUB. SITE OVERLOOKS THE MINE PIT APPROX 5 MI TO THE SW-W. LITTLE AJO MTNS 1.0 MI SSE-SW

The NCDC MMS database system is fraught with such discrepancies. I would suspect that researchers that use a lat/lon change to trigger examinations for a step function in the temperature record could miss this station. The lat/lon record for this station is changed in 1998 but the description remains unchanged.

Even using the old lat/lon in the MMS database puts this station not on a hill, but in a scrub field.

See Google Earth The mine pit referenced does have a hill to the east, which may be the location that was originally referenced. There does appear to be places where a Stevenson Screen may have been placed.

Alas, we may never know.