Climate Assessment for 1998

Climate Assessment for 1998 The global climate during 1998 was affected by opposite extremes of the ENSO cycle, with one of the strongest Pacific warm episodes (El Nio) in the historical record continuing during Januaryearly May and Pacific cold episode (La Nia) conditions occurring from JulyDecember. In both periods, regional temperature, rainfall, and atmospheric circulation patterns across the Pacific Ocean and the Americas were generally consistent with those observed during past warm and cold episodes.Some of the most dramatic impacts from both episodes were observed in the Tropics, where anomalous convection was evident across the entire tropical Pacific and in most major monsoon regions of the world. Over the Americas, many of the El Nio (La Nia) related rainfall anomalies in the subtropical and extratropical latitudes were linked to an extension (retraction) of the jet streams and their attendant circulation features typically located over the subtropical latitudes of both the North Pacific and South Pacific.The regions most affected by excessive El Niorelated rainfall included 1) the eastern half of the tropical Pacific, including western Ecuador and northwestern Peru, which experienced significant flooding and mudslides; 2) southeastern South America, where substantial flooding was also observed; and 3) California and much of the central and southern United States during JanuaryMarch, and the central United States during AprilJune.El Niorelated rainfall deficits during 1998 included 1) Indonesia and portions of northern Australia; 2) the Amazon Basin, in association with a substantially weaker-than-normal South American monsoon circulation; 3) Mexico, which experienced extreme drought throughout the El Nio episode; and 4) the Gulf Coast states of the United States, which experienced extreme drought during AprilJune 1998. The El Nio also contributed to extreme warmth across North America during JanuaryMay.The primary La Niarelated precipitation anomalies included 1) increased rainfall across Indonesia, and a nearly complete disappearance of rainfall across the east-central equatorial Pacific; 2) above-normal rains across northwestern, eastern, and northern Australia; 3) increased monsoon rains across central America and Mexico during OctoberDecember; and 4) dryness across equatorial eastern Africa.The active 1998 North Atlantic hurricane season featured 14 named storms (9 of which became hurricanes) and the strongest October hurricane (Mitch) in the historical record. In Honduras and Nicaragua extreme flooding and mudslides associated with Hurricane Mitch claimed more than 11 000 lives. During the peak of activity in AugustSeptember, the vertical wind shear across the western Atlantic, along with both the structure and location of the African easterly jet, were typical of other active seasons.Other regional aspects of the short-term climate included 1) record rainfall and massive flooding in the Yangtze River Basin of central China during JuneJuly; 2) a drier and shorter-than-normal 1997/98 rainy season in southern Africa; 3) above-normal rains across the northern section of the African Sahel during JuneSeptember 1998; and 4) a continuation of record warmth across Canada during JuneNovember.Global annual mean surface temperatures during 1998 for land and marine areas were 0.56C above the 196190 base period means. This record warmth surpasses the previous highest anomaly of 0.43C set in 1997. Record warmth was also observed in the global Tropics and Northern Hemisphere extratropics during the year, and is partly linked to the strong El Nino conditions during Januaryearly May. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Bulletin of the American Meteorological Society American Meteorological Society

Loading next page...
 
/lp/ams/climate-assessment-for-1998-kg6Yaz7Ojn
Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0477
D.O.I.
10.1175/1520-0477-80.5s.S1
Publisher site
See Article on Publisher Site

Abstract

The global climate during 1998 was affected by opposite extremes of the ENSO cycle, with one of the strongest Pacific warm episodes (El Nio) in the historical record continuing during Januaryearly May and Pacific cold episode (La Nia) conditions occurring from JulyDecember. In both periods, regional temperature, rainfall, and atmospheric circulation patterns across the Pacific Ocean and the Americas were generally consistent with those observed during past warm and cold episodes.Some of the most dramatic impacts from both episodes were observed in the Tropics, where anomalous convection was evident across the entire tropical Pacific and in most major monsoon regions of the world. Over the Americas, many of the El Nio (La Nia) related rainfall anomalies in the subtropical and extratropical latitudes were linked to an extension (retraction) of the jet streams and their attendant circulation features typically located over the subtropical latitudes of both the North Pacific and South Pacific.The regions most affected by excessive El Niorelated rainfall included 1) the eastern half of the tropical Pacific, including western Ecuador and northwestern Peru, which experienced significant flooding and mudslides; 2) southeastern South America, where substantial flooding was also observed; and 3) California and much of the central and southern United States during JanuaryMarch, and the central United States during AprilJune.El Niorelated rainfall deficits during 1998 included 1) Indonesia and portions of northern Australia; 2) the Amazon Basin, in association with a substantially weaker-than-normal South American monsoon circulation; 3) Mexico, which experienced extreme drought throughout the El Nio episode; and 4) the Gulf Coast states of the United States, which experienced extreme drought during AprilJune 1998. The El Nio also contributed to extreme warmth across North America during JanuaryMay.The primary La Niarelated precipitation anomalies included 1) increased rainfall across Indonesia, and a nearly complete disappearance of rainfall across the east-central equatorial Pacific; 2) above-normal rains across northwestern, eastern, and northern Australia; 3) increased monsoon rains across central America and Mexico during OctoberDecember; and 4) dryness across equatorial eastern Africa.The active 1998 North Atlantic hurricane season featured 14 named storms (9 of which became hurricanes) and the strongest October hurricane (Mitch) in the historical record. In Honduras and Nicaragua extreme flooding and mudslides associated with Hurricane Mitch claimed more than 11 000 lives. During the peak of activity in AugustSeptember, the vertical wind shear across the western Atlantic, along with both the structure and location of the African easterly jet, were typical of other active seasons.Other regional aspects of the short-term climate included 1) record rainfall and massive flooding in the Yangtze River Basin of central China during JuneJuly; 2) a drier and shorter-than-normal 1997/98 rainy season in southern Africa; 3) above-normal rains across the northern section of the African Sahel during JuneSeptember 1998; and 4) a continuation of record warmth across Canada during JuneNovember.Global annual mean surface temperatures during 1998 for land and marine areas were 0.56C above the 196190 base period means. This record warmth surpasses the previous highest anomaly of 0.43C set in 1997. Record warmth was also observed in the global Tropics and Northern Hemisphere extratropics during the year, and is partly linked to the strong El Nino conditions during Januaryearly May.

Journal

Bulletin of the American Meteorological SocietyAmerican Meteorological Society

Published: May 1, 1999

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off