Troy's Scratchpad

December 21, 2010

Continuing “A New Model for UHI in the US 1970-2000”

Filed under: Uncategorized — troyca @ 9:56 pm

This is a continuation of first part of the UHI analysis with the USHCNv2 temperature record from 1970-2000 using NHGIS economic and industry data.  Code and intermediate results can be downloaded for this post here.

In that post, Zeke left a helpful comment mentioning that the apparent UHI signal might instead simply be the bias of comparing stations that switched from CRS to MMTS instrumentation at different times.  Using the CRS-only stations here did not leave us with a lot of data to make a definitive statement.

In this analysis, I use the station history file found here to determine the month and year in which a particular station switched from CRS to MMTS, thereby allowing us to calculate the number of months between when one station and its neighbor station changed.

There are two notes I’d like to make before starting:

  1. The station history file ends in 1994.  If there is a history file that extends beyond that, I can’t find it.
  2. Stations switch-overs may simply not be recorded.  Therefore, I cannot simply assume that if a station does not note a switch to MMTS, that it has simply stayed as CRS.  Because of this and #1, the program only classifies stations as “NO_SWITCH” IF there is no switch recorded AND the station is listed in the “ushcn-crs-stations.txt” meta file.  This means that the NO_DATA category consists of stations that have either made the switch to MMTS after 1994, do not have a year or record for the switch, or have switched to ASOS instead.

Given the above notes, here is a chart showing the number of station switch-overs per year within the network for stations with valid temp data (7 or more reported years for each decade from 1970 to 2000):

And here is the subset of stations that include NHGIS data as well (which we’ll actually be using in our analysis):

As we can see, the bulk of the changes occur within the mid eighties.

Now for the results of our pairwise comparison tests.  These take much of the same form as the previous tests, except we now have another threshold as well for determining inclusion: # of months between the switch-overs.  A couple more notes regarding assumptions within this exercise:

  1. I only count the monthly difference up to the point that it will have an effect in our analysis.  So since we only go up to 2000, a station which never makes the shift away from CRS will list the switch date as January 2001.
  2. Some switch-overs have the year listed but not the month.  In these cases, I’ve set the month to “6”.

As you can see, the signal appear pretty robust and its existence is not greatly affected by the difference between the months switching to MMTS.  I was hoping to do more in this post, and have begun looking into the PHA (as you may have noticed in my last post) to see if I can gauge the magnitude of the UHI effect in the F52 dataset, but have run into difficulties with this project.  If anybody has experience re-creating the official F52 dataset by running the PHA, please drop me a line.

2 Comments »

  1. […] my recent pairwise station tests, I’ve been comparing nearby stations with different “distance” thresholds.  […]

    Pingback by USHCN Station Temperature Similarities by Distance « Troy's Scratchpad — January 6, 2011 @ 12:27 am

  2. Troy,

    In response to your comment over at CA, Menne is helping me by running his PHA code on different selections of urban and rural co-op and ushcn stations (based on nightlights, GRUMP, 1930-2010 population growth, and impermeable surfaces urbanity proxies). I’m collaborating on a paper with him and a few other folks that attempts to address quantifying UHI in different datasets (tob, F52, and F52 post GISS Step2 UHI corrections–e.g. F52 step2). We’ve been working on a pair-based comparison approach somewhat similar (oddly enough) what you’ve been developing independently.

    I’ll see if I can release the resulting urban and rural F52 series for your use. If you want to create your own urbanity classification for coop stations, I can see if we have the bandwidth to produce a separate series for you to work with. Shoot me an email at hausfath (at) gmail.com and we can chat about it more

    Comment by Zeke Hausfather — January 12, 2011 @ 5:34 pm


RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Create a free website or blog at WordPress.com.

%d bloggers like this: