GRAPHICAL CLIMATOLOGY OF DOWNTOWN LOS ANGELES DAILY TEMPERATURES AND RAINFALL,
BY YEAR (1921-PRESENT)
By Charles Fisk*, Newbury Park, CA. Latest Update: 15 March 2010
The following is a visual climatology of Downtown Los Angeles, California temperatures and precipitation, from 1921, the earliest year of continuous available digital observations, into the present year 2010. Included are summary overview charts followed by 91 year-to-year graphs from 1921 to 2010 depicting daily temperatures and rainfall.
The 1921-to-present period of record consists of observations from the Los Angeles Weather Bureau Office (through July 1964), the Los Angeles Civic Center (through late July 1999), and the Downtown USC Campus (late July 1999-to Present)
For the 1921-2000 period, data were accessed from the NOAA National Climatic Data Center on-line site, and from 2001 on, from the NWS Office-Los Angeles/Oxnard site (Downtown Los Angeles Climate page):
CLIMATE OVERVIEW GRAPHS –
DAILY MEANS & EXTREMES (FOR 1921-2008)
CLIMOGRAMS FOR LOS ANGELES INT’L AIRPORT:
“Diurnal and Seasonal Wind Variabilty for Selected Stations in Central and Northern California Climate Regions” – American Meteorological Society 21st Conference on Climate
Variability and Change - Phoenix, 2009. http://ams.confex.com/ams/pdfpapers/150512.pdf
“Diurnal and Seasonal Wind Variabilty for Selected Stations in Southern California Climate Regions” – American Meteorological Society 20th Conference on Climate Variability and
Change - New Orleans, 2008. http://ams.confex.com/ams/pdfpapers/135164.pdf
“Identification of Intra-month Daily Mean Temperature Modes Using Principal Components Analysis” – American Meteorological Society 16th Conference on Applied Climatology –
San Antonio, 2007. http://ams.confex.com/ams/pdfpapers/119632.pdf
“Principal Components Analysis of Month-to-Month Precipitation Variability for Downtown Los Angeles (1877-8 Through 2003-4 Seasons)” – American Meteorological Society 19th Conference
on Hydrology – San Diego, 2005. http://ams.confex.com/ams/pdfpapers/86848.pdf
“Objective Identification of Extreme-most Anomalous Daily Max/Min Historical Temperature Patterns Using Principal Components Analysis” – American Meteorological Society 17th Conference
on Probability and Statistics in the Atmospheric Sciences – Seattle, 2004. http://ams.confex.com/ams/pdfpapers/69198.pdf
The uppermost chart for a given year’s page (see links below) are “floating-bars” of the daily maxima and minima. Superimposed on the bars are two line traces, the upper one connecting 1921 to present average daily maxima, the lower one average daily minima. The bars depict the varying diurnal, synoptic, long-wave, and seasonal influences on temperature over time, and subjectively, some years’ visual features can be quite interesting to look at, interpreted physically or simply for their own sake.
The second chart down shows the day-to-day mean temperature anomalies (daily mean temperature less the corresponding long-term climatological mean). Vertical lines extending upward from the zero line indicate above average means for the day (colored red), those extending downward indicate below average daily means (colored blue). In general, the most extreme departures for Downtown Los Angeles are positive, reflecting to a large extent the occurrence of warming offshore flow episodes. In the entire 1921-present series, greatest positive departure for any given calendar day is +28 F for 6 April 1989, the most negative departure -19 F for 10 January 1949.
YEAR-TO-YEAR GRAPHS - LINKS
The third chart down shows the second chart’s anomalies in deseasonalized (“standardized”) form. This adjusts for the fact that individual calendar days have higher or lower inherent year-to-year variability in mean temperature. For example, Downtown Los Angeles calendar day mean temperature standard deviations for the 1921-2008 period ranged from 6.73 F (29 January) to 3.37 F (4 August) – see chart (top). To convert each of the daily temperature anomalies to a common, relative scale, they are divided by their corresponding calendar day standard deviations to create “standardized departures” or “z-scores. Those of plus or minus 3.0 occur just 0.5% of the time; nearly all of these positively signed, again reflecting extreme warming offshore flow episodes. Greatest positive departure in the record is +5.3 for 11 June 1979, greatest negative –3.4 for 22 December 1990.
The bottom chart depicts daily precipitation totals, as high as 5.88 inches (2 March 1938).
REPEAT LINKS TO SOME OF THE MORE INTERESTING YEAR-TO-YEAR GRAPHS, WITH ACCOMPANYING NOTES -
1921 - Wettest May in history (3.57”), and also coolest -- 1921-present.
1926 - More than 7 ½” rain in April – most for any April in all history (1878-present).
1930 - Highly fluctuating temperature pattern through the year.
1931 - Warmest year in the historical record up to this point.
1932 – Coo1 summer, but warmest November of the entire history (1877-present) followed by a sharp early December cold snap.
1937 – Very cold January, highest temperature only 61 F. Each of the year’s first 58 days colder than normal.
1938 - Torrential late February/early March rains cause severe local flooding; 5.88” rain on 2 March.
1939 – Week-long September heat wave precedes landfall of dissipating hurricane, which drops more than 5” rain. Warmest December of entire history (1877-present).
1940-41 - Wettest July-June “water year” (32.76”) since 1883-84, and until 1977-78.
1944 – Coolest calendar year of 1921-present period. Also coolest June and July.
1948-49 – Coldest meteorological winter (December-February) and calendar month (January) of entire history. Record coldest minimum (28 F) for any day (1921-present) on 4 January.
1953 - Driest calendar year (4.08”) in all history.
1955 – Eight-day run of 100 F or higher maxima from 31 August; 110 F on 1 September.
1959 - Warmest calendar year to date.
1960-61 - Driest water year (4.85”) in all history up to this time.
1963 - Late September heat wave.
1965 - October heat wave. More than 15” rain in November and December.
1966 - 100 F on 1 November.
1967 - Highly irregular day-to-day temperature pattern over course of year. Nearly 8 3/4” rain in November.
1969 - January wettest calendar month (14.94”) since December 1889.
1971 - Another highly irregular day-to-day temperature pattern over course of year. January experiences 95 F, February 91 F, September 106 F, and October 102 F, but December’s monthly mean ties 1916’s for lowest in history.
1971-72 - Nearly all the water year’s precipitation falls in December.
1975 - Coolest year since 1948.
1977-78 - Wettest water year (33.44”) since 1883-84 and until 2004-05.
1980 - Warmest year of entire history to date. Heavy February rains.
1981 - Another record warm year (surpasses 1980’s mark by 1.2 F). June also warmest in history.
1983 - Great El Nino year. Wettest calendar year, 1921-present (34.04”). Another record warmest year (surpasses 1981’s mark by <0.1 F).
1984 - September warmest calendar month in all history.
1985 - Warmest July in all history up to this time - 107 F on 1st.
1986 - Warmest January in all history.
1988 - 110 F on 1 September.
1989 - 106 F in April surpasses previous high mark for month by 7 F.
1990 - 112 F on 26 June sets all time high mark for any month. Late December cold spell.
1990-91 - “March Miracle” water year. Heavy late-February and March rains set in after exceptionally dry winter up to this point.
1992 - Warmest April of entire history.
1995 - More than 12 ½” rain in January. Warmest February of entire history.
1997 - Warmest meteorological Spring (March-May) of entire history. No recorded rainfall from 18 Feb through 24 Sep – 219 days.
1998 - The other great El Nino year of the 20th Century. Nearly 13 ¾” rain in February.
2001 - Coolest year since 1975.
2001-02 - Driest water year (4.42”) in all recorded history up to this point.
2004-05 - Wettest water year (37.25”) since 1883-4 and 2nd wettest in all recorded history.
2006 - Coolest March since 1962. Warmest July in all history.
2006-07 Driest water year (3.21”) in all recorded history (27% less than 2001-02’s previous low mark).
* Member, American Meteorological Society