Wednesday, February 18, 2015

Google Maps and GHCN adjustments

Google Maps and GHCN adjustments

A fortnight ago I posted a Google Maps gadget for viewing GHCN stations colored according to the effect on them of GHCN adjustments. I've been doing some improvements, and rewriting the code in the process. This simplifies the logic, and I'm hoping to produce a generic application to operate on any supplied data.

For the moment, the main improvement is that it displays a count of whatever is colored on the screen. So you can quickly show how many have been adjusted up, or down, with selection criteria specified. The other improvement is that the popup data includes a link to the GHCN display page, giving extensive history and graphs of observations and adjustments.

I have also updated the data to Jan 2015.

The plot is below. And below that, some details about the usage logic. The field Trend_Adj is the trend difference over whole of life made by adjustment, in °C/cen. It is set to NaN for stations with less than 360 months of adjusted data in total (maybe with gaps).

The green box on the right has a collection of selection criteria. Some are comparisons, some are logical. The second small button toggles between the relation options (>,==,T/F etc), and for comparison, the third is a text box in which you enter the reference value. Only one selection can be live at a time, determined by the left radio button.

When you have a live selection, you can click a radio button in the top orange section (Pink,Cyan etc). Any stations that fulfill your requirement will change to that color. In the middle column, the numbers in each color are shown, and updated with each choice. Invisibles are still in the totals.

The right column shows the most recent logical operation that was implemented for that color. It does not show the status of all markers in that color. If the color is eg pink, then the expression will not include markers that were pink before the latest selection, and the other logicals don't change. I could make a logical expression for the state, but it would quickly get very complicated.

The All button, when F does nothing, but when T and live changes everything to one color. You may want to start with everything invisible. I'd make this the default, except that it is a bit discouraging when you are first trying to make something happen.

You can enter NaN into the text fields, which will have the effect of changing any NaN to that color. Usually used to make them invisible. For Trend_Adj, there is the option of equality ("=="), mainly used to test for zero. I should warn that it tests to rounding level, which is 0.01. Very few stations totally escape adjustment (eg MMTS), but it is often very small.

I've included Lat and Lon; it doesn't mean much when you have a map. but is useful for counting, eg Arctic. I have given Urban and Rural as separate options, because there is also Mixed. So if you color Urban T, that is what you see, but Rural F gives Urban and Mixed.

You'll find negative logic useful. The advice on how to sculpt an elephant is, take a very big rock and chip away anything that doesn't look like an elephant. Same here. If you want pink to show urban stations that have trend increased on adjustment, then pink all uptrended, then go to Urban F, and make that invisible. That will affect other colors too (if any).


  1. Impressive. Needless to say I checked a few places I've lived to see how my personal experience correlates to the adjustments.

    While looking at this map, I realize that two of the stations are poorly sited for global studies being as they are at boundary conditions extremely susceptible, or amplifying, slight changes.

    A vertical boundary condition exists at my hometown which sits in a bowl. Cold, dense air accumulates in the winter with a sharp boundary layer to much warmer air sitting on top of the bowl. The station is right at the edge of this bowl so in winter it might be measuring the cold, dense air or the warmer air just above it and the difference is enormous, 20 to 40 degrees (F) in less than a thousand feet.

    A lateral boundary exists in the Aleutian Islands. ADAK/NAVY 42570454000. Trend Adj 1.06. Urban. Airpt Y

    Urban? You've got to be kidding me. Take a look on Google Earth. Yeah its an airport but the *minimum* wind was hardly ever less than 20 knots typically 40 knots, well mixed in other words. Furthermore it has only 10 sunny days a year so UHI is nonexistent. Really, seriously, when the sun came out, which it did only in the eye of each cyclonic storm in an eternal succession of such things, you had one hour to enjoy it.

    But those storms breed because of a collision of cold, dry polar easterlies with mid-latitude westerlies which blow over the Japan Current to pick up heat and moisture.

    A slight movement poleward of this boundary will produce huge and dramatic changes on the land underneath the former location of the boundary. It doesn't mean huge and dramatic global climate change; it means that change is more noticeable at a boundary. Anyway, the adjustments are rather severe on this station which I consider improper because the actual change on the ground was dramatically noticeable. I was there in the 1970's during Northern Hemisphere's cold spell and it was impressively stormy; blew the roof right off the building where I was staying (it had a doubled roof fortunately) and the anemometer, or wind speed thingy, blew right off the mast but it recorded something like 180 knots before it was ripped off the mast. What happens is called "williwaw" and is a combination of wind being funneled between mountains picking up velocity, combined with becoming cooler and denser because of the snow on the mountains, so when it comes pouring down the other side it has gained density and velocity and will follow Earth contours like an avalanche. I had a big heavy chain holding the hood of my pickup truck and pretty much everyone had 2 inch nylon straps fastened to car doors to limit their opening in the case you were an idiot and opened your car door with the wind coming from behind.

    Fun times.

    1. Neither ADAK nor Dutch Harbor are current stations. Basically GHCN is a mix between a historic project in early 90's, where they basically collected every good record available, and an ongoing project since about 1997, with selected stations. We can think over where stations might be best placed, but for the history, we just have to use what is there.

  2. Something's odd with the Urban thing. Both 42570454000 and 42570482001 show as urban on the map. But they're both listed and rural and low night light (R and C) in the inv file.

    1. I agree that the urban classifications can be surprising. But Here are the inventory listings. The C at the end means Urban
      42570454000 51.8800 -176.6500 4.0 ADAK/NAVY 0R -9MVxxCO 1A-9HEATHS, MOORS C
      42570482001 53.9000 -166.5300 5.0 DUTCH HARBOUR ALASKA 0R -9MVxxCO 1A-9HEATHS, MOORS C