Climatic Research Unit: Data

Lamb Weather Types

Lamb

Professor H.H. Lamb subjectively classified each day's weather over the British Isles from 1861 to February 1997. All the years have been published, except for 1996/7, in Lamb (1972) and Hulme and Barrow (1997). The complete series of the classification is given here. Several periods before 1861 have also been classified (see Lamb, 1991).

File format

format(a) descriptive header line for year = firstyear to lastyear (rows) for month = 1 to 12 (columns) format(31i3) each day of month

File format
format(a) descriptive header line for year = firstyear to lastyear (rows) for month = 1 to 12 (columns) format(31i3) each day of month

Lamb Types - Number coding

-1 U -9 non-existent day 0 A 20 C 1 ANE 11 NE 21 CNE 2 AE 12 E 22 CE 3 ASE 13 SE 23 CSE 4 AS 14 S 24 CS 5 ASW 15 SW 25 CSW 6 AW 16 W 26 CW 7 ANW 17 NW 27 CNW 8 AN 18 N 28 CN

Lamb Types - Number coding
-1 U -9 non-existent day 0 A 20 C 1 ANE 11 NE 21 CNE 2 AE 12 E 22 CE 3 ASE 13 SE 23 CSE 4 AS 14 S 24 CS 5 ASW 15 SW 25 CSW 6 AW 16 W 26 CW 7 ANW 17 NW 27 CNW 8 AN 18 N 28 CN

Filename Description
lwtlamb.dat Lamb Weather Types - Lamb 1861-1997

Filename	Description
lwtlamb.dat	Lamb Weather Types - Lamb 1861-1997

References

Hulme, M. and Barrow, E. (Editors), 1997: Climate of the British Isles: present, past and future, Routledge, London, 454pp.

Lamb, H.H., 1972: British Isles Weather types and a register of daily sequence of circulation patterns, 1861-1971. Geophysical Memoir 116, HMSO, London, 85pp.

Lamb, H.H., 1991: British Isles daily wind and weather patterns 1588, 1781-86, 1972-91 and shorter early sequences (in 1532, 1570 and other years, notably 1688, 1689, 1694, 1697, 1703, 1717, 1783-4, 1791, 1792, 1795, 1822, 1825, 1829, 1845, 1846, 1849, 1850, 1854-5. Climate Monitor 20, 47-70.

Jenkinson

An objective scheme to classify the daily circulation according to the Lamb weather typing scheme was developed by Jenkinson and Collison (1977). The objective scheme uses daily grid-point mean sea level pressure data (see map below). The objective and the original subjective Lamb scheme have been compared by Jones et al., (1993). A new series has now been producuced using reanalyses data (Jones, et al., 2012). For the period from 1871-1947 the 20CR developed by Compo et al. (2011) is used and for 1948 to present the National Centers for Environmental Prediction, NCEP Reanalysis by Kalnay et al., (1996) is used. In developing a new and more consistent series, we have chosen to base the analysis data on the synoptic hour 12, as this is in the centre of the civil day to which the LWTs refer. The series from 1871 to the present day is given here.

File format

Description of columns day month year PM-1000 W S F Z G Dir LWT Definitions: PM_1000 average pressure over the grid points W westerly flow S southerly flow F resultant flow Z total shear vorticity G gale day Dir direction of flow LWT see above table

File format
Description of columns day month year PM-1000 W S F Z G Dir LWT Definitions: PM_1000 average pressure over the grid points W westerly flow S southerly flow F resultant flow Z total shear vorticity G gale day Dir direction of flow LWT see above table

Location of the grid points over the British Isles.

Filename	Description
20CR_1871-1947_ncep_1948-2011_12hrs.dat	1871-1947 20CR; 1948-present NCEP
20CR_1871-1947_ncep_1948-2011_12hrs.csv	as above in csv format (contains headers)
20CR_1948-2010_12hrs.dat	1948-2010 (20CR to facilitate comparison)

The following files provide the output described at the other synoptic hours, but they do not contain the LWT:

Filename	Description
ncep_1948_2011_00hrs.dat	1948-present NCEP 00hrs
ncep_1948_2011_06hrs.dat	1948-present NCEP 06hrs
ncep_1948_2011_18hrs.dat	1948-present NCEP 18hrs

Filename	Description
20CR_1871-2010_00hrs.dat	1871-2010 20CR 00hrs
20CR_1871-2010_06hrs.dat	1871-2010 20CR 06hrs
20CR_1871-2010_18hrs.dat	1871-2010 20CR 18hrs

NB 'present' equates to last year, we intend to update using the NCEP series annually around March.

References

Compo, G.P., Whitaker, J.S., Sardeshmukh, P.D., Matsui, N., Allan, R.J., Yin, X., Gleason, Jr B.E., Vose, R.S., Rutledge, G., Bessemoulin, P., Brönnimann, S., Brunet, M., Crouthamel, R.I., Grant, A.N., Groisman, P.Y., Jones, P.D., Kruk, M.C., Kruger, A.C., Marshall, G.J., Maugeri, M., Mok, H.Y., Nordli, Ø., Ross, T.F., Trigo, R.M., Wang, X.L., Woodruff, S.D., Worley, S.J., 2011: The Twentieth Century Reanalysis Project. Q. J. R. Meteorol. Soc. 137 1-28. DOI:10.1002/qj.776.

Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., Wollen, J., Zhu, Y., Chelliah, M., Ebisuzaki, W., Higgins.,W., Janowiak, J., Mo, K.C., Ropelewski, C., Wang, J., Leetmaa, A., Reynolds, R., Jenne, R. and Joseph, D., 1996: The NCEP/NCAR 40-year reanalysis project. Bulletin of the American Meteorological Society, 77, 437-471.

Jenkinson, A.F. and Collison, F.P., 1977: An initial climatology of gales over the North Sea. Synoptic Climatology Branch Memorandum No. 62, Meteorological Office, Bracknell.

Jones, P.D., Hulme, M. and Briffa, K.R., 1993: A comparison of Lamb circulation types with an objective classification scheme. Int. J. Climatol. 13, 655-663.

Jones, P.D., Harpham, C. and Briffa, K.R., 2012: Lamb Weather Types derived from Reanalysis Products. Int. J. Climatol. xx, xxx-xxx (online only at present). DOI: 10.1002/joc.3498

Last updated: April 2012, Colin Harpham

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Please use the attribution Climatic Research Unit, University of East Anglia