IRI Climate Digest August
2001
July Global Climate Summary
Climatological Background In July, heating of the continents
in the Northern Hemisphere results in strengthened monsoon systems which
bring rains to West Africa, South Asia, and southwestern North America.
In the Southern Hemisphere winter has set in with stronger north-south
temperature gradients fueling active mid-latitude storm tracks.
Monthly Mean Temperature (1961-1990), data from the Climate Research
Unit, University of East Anglia
Monthly Mean Precipitation (1961-1990), data from the Climate Research
Unit, University of East Anglia
Temperatures
Europe: July brought a resurgence of above average conditions
with temperatures well above average across eastern Europe, from the Mediterranean in the south
northward to Scandinavia.
Asia: In contrast to recent months, central Russia, east of
the Ural Mountains, was unusually cool. Much of Siberia averaged warmer than usual as did Japan,
the Korean Peninsula and northeastern China.
Africa: Temperatures returned to near-average along
coastal areas of western North Africa while central sections including Chad, Niger, Algeria and Libya were
much warmer than average for the month, as was much of the central Congo Basin.
Australia: Temperatures continued well above average across
eastern sections of New South Wales and Victoria.
North America: Unusually warm conditions extended from
the northern half of Mexico northward through the Great Plains of the United States and in much
of north-central Canada. Temperatures were well below average from New England southward to
the Mid-Atlantic states in the US.
South America: Temperatures were well above average in
much of Brazil and Paraguay. Unusually warm conditions were also observed in eastern Colombia northward
into Venezuela.
Temperature Difference from the 1961-1990 mean, with data from NCEP
Climate Prediction Center, CAMS.
Precipitation
Asia: Very heavy summer monsoon rainfall fell across much
of eastern and northern India as well as in both northern and southern Pakistan. Tropical cyclones
along with heavy monsoon rains soaked much of southern China, especially along and near costal
areas. Unusually dry conditions persisted across sections of the North China Plain and developed
in Mongolia.
Indonesia and the Philippines: Rainfall was unseasonably
heavy across sections of Sumatra and Java. Tropical cyclone activity produced very heavy rains
across northern sections of the Philippines.
Africa: Rainfall was near to above average across much
of the Sahel while unusually dry conditions developed in areas along the Guinea coast in West Africa.
Rainfall was below average across much of western Ethiopia and into eastern border areas
of Sudan. Unusually heavy rain fell across eastern sections of the Demcratic Republic of
the Congo, Uganda and northwest Tanzania.
South America: Rainfall was well above average in extreme
western Brazil as well as northern Bolivia and eastern Peru. Unseasonably dry conditions
prevailed over much of the region north of the equator.
North and Central America: Much needed rainfall fell across
the Florida peninsula in conjunction with a tropical storm while much of the central and northeastern
United States was unusually dry. Drought conditions developed across Honduras,
Guatemala, Nicaragua and Costa Rica as below average rainfall in much of those areas persisted
during July. Central and southern Mexico also saw below average rainfall during the month.
Europe: Very wet across central Europe, Poland especially.
Ununusually heavy rainfall also fell across much of France and in northern Scandinavia.
Australia and New Zealand: Below average rainfall continued
along eastern coastal sections of Queensland and New South Wales and in much of Victoria. Drought
conditions continued in many areas of New Zealand as rainfall continued below average.
Precipitation Difference from the 1979-2000 mean, with data from NCEP
Climate Prediction Center, CAMS-OPI.
Oceanic Conditions
Tropics: The slightly warmer than average sea surface
temperatures (SSTs) in the west-central equatorial Pacific which emerged in June strengthened
somewhat in July while near average SSTs continued across much of the eastern portion of the
basin. Despite the modest warming in western areas during July, current observations continue
to indicate near neutral conditions and numerical models continue to predict near-neutral
to slightly warmer than average conditions to continue over the next 6 to 9 months.
The eastern two-thirds of the Indian Ocean continue to be warmer than
average while the warmer than average SSTs in the Gulf of Guinea have weakened in the
tropical Atlantic. Above average temperatures in the tropical North Atlantic persisted
through July.
Mid latitudes: In the North Pacific, unusually warm waters
cover much of western and central areas at low latitudes with below average SSTs located across
much of the north. In the South Pacific, above average SSTs continue to the east of Australia
and in central sections of the basin. In the North Atlantic, a broad band of above average
SSTs extended from Europe southwestward into the subtropics.
Monthly Sea Surface Temperature Difference from the 1950-1979 mean,
with data from the Environmental Modeling Center, NCEP/NOAA.

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