Wednesday, March 14, 2012

2458.txt

cc: Tim Osborn <t.osbornatXYZxyz.ac.uk>, dave lister <d.listeratXYZxyz.ac.uk>
date: Wed, 24 Sep 2008 17:51:08 +0100
from: Ian Harris <i.harrisatXYZxyz.ac.uk>
subject: Re: Cru TS 3.0 data
to: Daniel Kingston <d.kingstonatXYZxyz.ac.uk>

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Hi Daniel,

OK, I've found it - I think.

If we look at the nine cells surrounding and including yours, we get
eight stations from each database.

Here are the 1967 values:

Old Database (CRU TS 2.10):
1967 1210 1250 3140 1850 90 0 0 20 100 1670 2170 3090
1967 900 2000 2700 3000 40 0 0 100 200 1300 2700 2640
1967 1120 1630 1730 4750 10 0 0 0 350 890 4460 3910
1967 960 1750 1650 3680 30 0 0 0 440 1090 4100 3630
1967 1440 1570 2960 3280 10 0 0 150 130 1320 2780 2930
1967 210 2350 1340 1890 140 0 0 0 260 840 2940 2110
1967 1090 1090 2580 1220 0 0 0 0 230 2080 2060-9999
1967 260 1280 2570 1970 150 0 0 0 0 770 1850 2500

New database (CRU TS 3.0):
1967 1210 1250 3140 1850 90 0 0 20 100 1670 2170 3090
1967 900 2000 2700 3000 40 0 0 100 200 1300 2700 2640
1967 1120 1630 1730 4750 10 0 0 0 350 890 4460 3910
1967 960 1750 1650 3680 30 0 0 0 440 1090 4100 3630
1967 1440 1570 2960 3280 10 0 0 150 130 1320 2780 2930
1967 210 2350 1340 1890 140 0 0 0 260 840 2940 2110
1967 1090 1090 2580 1220 0 0 0 0 230 2080 2060-9999
1967 260 1280 2570 1970 150 0 0 0 0 770 1850 2500

They are identical. So for April, the 4750 value is present in both
databases. This is the station in question:

6632500 -1238 1695 1702 SILVA-PORTA(B.KUITO) ANGOLA 1930
1992 -999 -999.00

In the 2.10 database, this station had a lot of missing data,
including 1973 to 1983. This would have excluded it from the
processing because a reliable 1961-1990 climatology could not be
established. However, in the 3.0 database, most of that missing data
has been 'found' - so the station would have been included.

If you look at the other 1967 values, I think it's clear that it was
a very wet month in some parts of Angola. Stations with precip above
2000 for April 1967 (both databases):

6631800 -1280 1570 1701 NOVA LISBOA ANGOLA 1940
1992 -999 -999.00
1967 900 2000 2700 3000 40 0 0 100 200 1300 2700 2640

6632500 -1238 1695 1702 SILVA-PORTA(B.KUITO) ANGOLA 1930
1992 -999 -999.00
1967 1120 1630 1730 4750 10 0 0 0 350 890 4460 3910

9967150 -1230 1690 1670 CEILUNGA ANGOLA 1943
1972 -999 -999.00
1967 960 1750 1650 3680 30 0 0 0 440 1090 4100 3630

9967170 -1270 1580 1700 CHIANGA ANGOLA 1947
1992 -999 -999.00
1967 1440 1570 2960 3280 10 0 0 150 130 1320 2780 2930

Note that CEILUNGA is too short to have ever made the grade, but the
value of 3680 supports the 4750. Similarly, CHIANGA has too much
missing data (even for 3.0) to be included. We're left with NOVA
LISBOA (3000) and SILVA-PORTA (4750). The real damning piece of
evidence? NOVA LISBOA was also plagued with missing data in 2.10, and
so also failed to contribute!

In essence: two stations with anomalously high rainfall for April
1967 were excluded from 2.10 but included for 3.0, because of
additional data that enabled normals to be calculated for them. Two
further station in the same area are excluded from both datasets but
have similarly high values.

I am happy to investigate further if you'd like? I'd also welcome
comments as to my reasoning!

Cheers

Harry


On 23 Sep 2008, at 18:29, Daniel Kingston wrote:

> Hi Tim
>
> I realise you are likely to be very busy at the moment, but we have
> come across something in the CRU TS 3.0 data set which I hope you
> can help out with.
>
> We have been looking at the monthly precipitation totals over
> southern Africa (Angola, to be precise), and have found some rather
> large differences between precipitation as specified in the TS 2.1
> data set, and the new TS 3.0 version. Specifically, April 1967 for
> the cell 12.75 south, 16.25 east, the monthly total in the TS 2.1
> data set is 251mm, whereas in TS 3.0 it is 476mm. The anomaly does
> not only appear in this cell, but also in a number of neighbouring
> cells. This is quite a large difference, and the new TS 3.0 value
> doesn�t entirely tie in with what we might have expected from the
> station-based precip data we have for this area. Would it be
> possible for you could have a quick look into this issue?
>
> Many thanks,
>
> Daniel.
>
>
>
> --------------------------------------------------------
> Dr Daniel Kingston
> Post Doctoral Research Associate
> Department of Geography
> University College London
> Gower Street
> London
> WC1E 6BT
> UK
>
> Email d.kingstonatXYZxyz.ac.uk
> Tel. +44 (0)20 7679 0510
>
> http://www.geog.ucl.ac.uk/about-the-department/people/research-
> staff/daniel-kingston/
> -------------------------------------------------------
>

Ian "Harry" Harris
Climatic Research Unit
School of Environmental Sciences
University of East Anglia
Norwich NR4 7TJ
United Kingdom


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