New ISTI temperature dataset - station trends map

This is my second post on the new beta release of the ISTItemperature database. The first post was a Google Maps interactive map of the stations. This time we have an interactive global trend map in the style I did for GHCN.

Again, the dataset is large, and takes a few seconds to load, so I have put it below the fold. It is a globe that shows individual station trends with shading on a triangular mesh. The shading color is accurate at the stations themselves. You can display the stations and mesh, and click to pick up the numerical information. There is a little navigator map that lets you reorient the globe as you wish. Maps are available for periods of 30, 45 and 60 years to present. You can magnify 2x, 4x or 8x.

I should emphasise that these are trends for individual stations - there is no modelling or smoothing, except for the triangle shading interpolation. I find that valuable in that it shows the spatial correlation (or lack of). I was interested to see if the larger ISTI set gave a similar result to GHCN.

I think it does. A notable feature of all these plots, whether for period averages or trends, is that the US seems more of a patchwork than ROW. This is of course partly the higher density of stations, but I think there really is less coherence. Perhaps there is a quality issue (associated with the large numbers).

Anyway, the map is below the jump. There is some further discussion of the methods in this plot from last November. Below the map I've written a little about the numerics..

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Click on this map to orient the world plot. Show Stations Show Mesh Magnification 2× 4× Trend period 1952-2011 1967-2011 1982-2011 Station

How the trends are calculated.

The trends are calculated using monthly data over calendar years (So I didn't use 2012 months). There is a tricky issue with seasonality. If you take the trend of a year from autumn to autumn, monthly, you'll get an uptrend even if the year ends as it began. The calendar year is mostly winter to winter or summer to summer, so the effect is much diminished. I allowed for this using the method from TempLS. Instead of just one intercept, I fit (OLS) twelve monthly offsets (means) as well as the slope. This subtracts out the seasonal variation and gives the underlying trend.

Sea Temperatures

As usual I've added SST's by taking a published gridded set and putting artificial stations at the grid centres. Previously I've used ERSST, this time I used HADSST2. The emphasis is on the land data, but the mesh goes haywire without ocean nodes. The HAD grid is coarser, so the ocean trends are more patchy. Because of the arbitrary placement of stations at 5x5 grid centres, it can happen that they appear on land. Please excuse.

Update There are some odd hotspots in southern oceans for the longer time periods. This is an artefact. It is caused by an arrangement I have which enables me to use the same mesh for all three time intervals (meshes take time to download). I use a single mesh with a node for every station with any admissible trend - a station has to have 80% of months reporting to be assigned a trend over a period. Where for a time period a station doesn't have a trend, I assign an interpolated value for coloring purposes. The station is not shown, so the effect should be a minor upset in the shading only. However, there are in those parts some stations which do not have any connected stations with trends (for that time interval - worst at 60 years). Then the interpolation goes wrong, and the shading shows artificial heat. I don't think it happens anywhere on land.

New ISTI Temperature database - stations in Google Maps with GHCN

A few days ago, Peter Thorne of NOAA noted in a comment that a new Initiative ISTI, with NOAA involvement, has released a large new database of surface temperatures. It's on a similar scale to BEST, and I'll do comparisons in due course. But as an initial step, I thought it would be useful to gather a Google maps presentation, as I did for GHCN.

The beta release is here. I used the recommended merge (3 Oct version). The data combines TMIN, TMAX and TAVG (and is big!); I extracted the TAVG. There were 39430 stations in the inventory.

This is a big set for the GM application, so I've divided it into 8 regions with about 5000 each. You can look at them all at once if you like, but it will run very slowly. Selecting one or two regions is much better. There is a little map at the right of the display showing where they are. Because the data takes several seconds to download, I've put the map beneath the fold.

The idea of the map is that it shows stations with tags with information that you can pop up by clicking. But the main use is that you can filter by categories. You can choose ranges of start date (of data), end date, duration and altitude. The mechanics are that you make these selections, select regions, and then press one of the colors (for tag). What you've asked for will appear in that color, additional to what was there before. A special (and useful) color is invisible. The range choices combine with "or" logic, so you get "and" by making what you don't want go away. Because it is "or", you need to suppress the "All" button to make other choices. The buttons toggle. The middle columns with gt and lt signs also toggle.

I've included GHCN stations for comparison. There is a checkbox for each database. To compare you'll probably want to display in one color with one box ticked, and in another with the other box ticked (only one at a time). The green pin is useful here, in case of overlaps.

The map starts out blank, waiting for you to choose a region (or two). It's below the jump:

Usage

The map initially shows no markers. You need to select regions. I'd recommend starting with just one. If you click one of the marker colors, you'll then see a mass of markers in that region. You can filter some out with the invisible button - remember to toggle the "All" button when making selections. You could filter out, say, all stations starting after 1850. The selections are only operative if the left radio button is on.

You can ask for a different selection and a different color. It is the color request that creates actions. This second request doesn't erase markers already showing, though it will change the colors of those that qualify.

Note that choosing a small number of regions helps with performance, but other choices which reduce tags on screen do not help (the tags are there but invisible).

Worked example

I was curious about whether ISTI had more really old data than GHCN. As I found earlier, BEST v1 has a similar number of stations overall, but little new before 1850. So I did this:

1. Set Region 6
   
2. Unset All, set StartYr, and change the textbox to 1800.
   
3. Under Actions, click Yellow.
   
4. Unset ISTI, set GHCN
   
5. Under Actions, click Pin.
   

So I see a lot of yellow tags in Europe, some with green pins, and some green pins on their own. Clicking on the pins brings up info including start dates. Some things I notice:

• In UK, GHCN has Gordon Castle, Greenwich and Manchester. ISTI doesn't, but has a Central England, which may cover the last two.
  
Both have a Trondheim in the right place, with similar dates (ISTI 1761-2012, GHCN 1761-1981). But ISTI has TRONDHEIM_VAERNES, about 2.5° further E, from 1762-2011. Duplicate?
• GHCN has Lund, 1753-1773. ISTI not.
  
• ISTI has two Budapest records, both starting in 1780. GHCN has one.
  ISTI has San Fernando, from 1786, GHCN not.
  
• ISTI has two Prague records (PRAHA-KLEMENTINUM,PRAHA-RUZNY), one starting in 1771, the other in 1775. GHCN has Praha-Ruzyne.
  
• ISTI has a record for Vienna and one for Wien. Both start in 1775.
  
• ISTI has OBERSCHLEISSHEIM and UCCLE (Belg), GHCN not.
  

So ISTI has a few extras in that period in Europe, some of which may be duplicates.