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 July 1999 temperature anomalies
calculated from available in-situ stations using an 1880 - 1998
base period. Temperature anomalies are absent from several areas of
the globe due to a lack of reporting stations. To improve spatial
coverage of global temperature anomalies, satellite data has been
combined with in-situ station records in the spatial temperature
plot below. Several areas of the globe had temperatures above the
long-term mean. The British Isles to the Black Sea, the eastern
half of North America, and central Asia were all covered by high
pressure, which promoted the warm anomalies. In contrast, northern
Scandinavia and northwestern Canada were dominated by upper level
troughs, which promoted cooler than average temperatures.
Southeastern China and most of Argentina were cooler than
average.
Temperature
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Preliminary mean
monthly temperature anomalies (using a base period 1880-1998) for
July are shown in the figure to the left. July 1999 land and ocean
temperatures were much lower than the record values recorded in
1998. Temperatures (for land and ocean) remained above the
long-term mean for the 23rd year in a row. |
| There are three areas
of the globe with distinct warm surface temperature anomalies. The
majority of the United States and southeastern Canada were well
above average this month. High pressure dominated western Russia
southward to the Mediterranean Sea, causing the surface to be much
warmer than usual. The largest warm anomalies resided just north of
the Black Sea. Another area of warmer than usual temperatures
occurred over central Russia, and extended southward into Mongolia
and northeastern China. This area was also associated with a
persistent upper level ridge. |
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| Cold temperature
anomalies were most evident in the east equatorial Pacific, in
association with La Niña. These cool anomalies extended
eastwards into the coastal and southern areas of South America. The
greatest cold anomalies were in northwestern Canada, and these
corresponded with a upper level trough.
The atmospheric circulation anomaly pattern for July 1999 is
available for the Northern Hemisphere
and Southern
Hemisphere.
See the U.S. Regional / Statewide
Analyses pages and the Global
Regional Analyses pages for more details on regional climate in
the United States and throughout the world.
|
Precipitation
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There are some
distinct features on the precipitation anomaly map. The largest
negative anomalies occurred over most of India. This is the season
of the southwest monsoon when India gets its monsoonal rain. The
monsoon was weaker than usual this July and restricted to eastern
India and Bangladesh where flooding occurred. In contrast, the
Mediterranean area is usually very dry at this time of year, yet in
July they had above average precipitation. Widespread flooding
occurred along the Yangtze River in southern China and Japan
received above average rainfall, while parts of northeastern China
were drier than usual. The western Sahel received more rain than
average, which is excellent for their growing season, while
northeastern Europe was drier than usual. The majority of Argentina
had above average rainfall, which is beneficial for their winter
wheat crop. |
Global Surface Wetness
| The summer monsoon
rains over Mexico and the southwest U.S. were stronger than normal
in July, which caused above average surface wetness. It was also
wetter than average across the Plains near the U.S.-Canadian
border. The snow in northern Canada was slow to melt this summer,
which promoted above average surface wetness in July. This was also
true for north central Russia. Heavy rains fell across eastern
portions of the Indian subcontinent and brought major flooding
across portions of eastern India and Bangladesh. Heavy rains also
caused flooding in the Yangtze river basin in China. |
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In contrast, rainfall was below average across the remainder of the
western and southern portions of Asia. Much of southeastern
Australia was drier than usual, while the adjoining area to the
southwest had above average rainfall. Rainfall in the Sahel region
of Africa was above average, but some sectors experienced unusually
dry conditions.
