Global Analysis - September 1999
Note: The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. Effective September 2012, the GHCN-M version 3.2.0 dataset of monthly mean temperature replaced the GHCN-M version 3.1.0 monthly mean temperature dataset. Beginning with the August 2012 Global monthly State of the Climate Report, released on September 17, 2012, GHCN-M version 3.2.0 is used for NCDC climate monitoring activities, including calculation of global land surface temperature anomalies and trends. For more information about this newest version, please see the GHCN-M version 3.2.0 Technical Report.
*The GHCN-M version 3.1.0 Technical Report was revised on September 5, 2012 to accurately reflect the changes incorporated in that version. Previously that report incorrectly included discussion of changes to the Pairwise Homogeneity Algorithm (PHA). Changes to the PHA are included in version 3.2.0 and described in the version 3.2.0 Technical Report. Please see the Frequently Asked Questions to learn more about this update.
The above figure shows September 1999 temperature anomalies calculated from available in-situ stations using a 1880 - 1998 base period. Two persistent high pressure areas, one over Europe and one over eastern Canada and the northeast U.S., resulted in temperatures well above the long term mean in these areas. (See the September atmospheric circulation pattern for the Northern Hemisphere.) Mean temperatures were more than 5 C above average in some locations. Above average temperatures were also recorded in the Far East, much of the southern half of South America, the Mediteranean and western areas of the United States. The largest area of cooler than average temperatures is shown throughout the central and southeastern areas of the U.S. No other area of widespread below average temperatures are shown in this figure; however, it is possible that cooler than average temperatures were more extensive, but not shown in this figure due to unreported data.
|Preliminary mean monthly temperature anomalies (using a base period 1880-1998) for September are shown in the figure to the left. September 1999 ocean temperatures were much lower than the 1997 and 1998 values and were the 3rd coolest this decade. However, land temperature anomalies continued to be very warm. The average global land temperature was 0.65 C above the long term mean, the second warmest anomaly on record.|
Western Europe was wetter than average as a low pressure trough in the eastern Atlantic brought abundant moisture to Iceland and western areas of the European continent. An area of high pressure limited precipitation throughout much of eastern Europe. Tropical cyclones affected parts of Korea and southwestern Japan, producing much above average rainfall in these areas. For additional details on precipitation and temperatures in September see the Global Regional page .
larger image As shown on the adjacent map, precipitation anomalies were highly variable in September. Flooding rains fell in northern areas of India and Bangladesh, while areas in the south and west were much drier than average. Eastern areas of the U.S. received record rainfall in September primarily due to hurricanes Dennis and Floyd. Areas to the west continued to be much drier than the long term mean. (See the U.S. national page for a complete discussion.)
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