نتایج جستجو برای: arctic oscillation
تعداد نتایج: 61620 فیلتر نتایج به سال:
Studies from a variety of disciplines document recent change in the northern high-latitude environment. Prompted by predictions of an amplified response of the Arctic to enhanced greenhouse forcing, we present a synthesis of these observations. Pronounced winter and spring warming over northern continents since about 1970 is partly compensated by cooling over the northern North Atlantic. Warmin...
A novel diagnostic tool is presented, based on polar-cap temperature anomalies, for visualizing daily variability of the Arctic stratospheric polar vortex over multiple decades. This visualization illustrates the ubiquity of extended-time-scale recoveries from stratospheric sudden warmings, termed here polar-night jet oscillation (PJO) events. These are characterized by an anomalously warm pola...
1 Throughout much of the latter half of the 20th century, the dominant mode of North2 ern Hemisphere (NH) extratropical wintertime circulation variability−the Arctic Oscillation 3 (AO)−exhibited a positive trend, with decreasing high-latitude sea-level pressure (SLP) and 4 increasing mid-latitude SLP. General circulation models (GCMs) show this trend is related 5 to several factors, including N...
The connections between the Madden–Julian Oscillation (MJO) and Arctic (AO) are examined in both observations model forecasts. In observations, time-lag composites carried out for AO indices anomalies of 1,000-hPa geopotential height after an active or inactive initial MJO. results show that when is its positive (negative) phase at time, activity generally enhanced (weakened) Reforecast data 11...
Carbon, water and energy exchanges between forests and the atmosphere depend upon seasonal dynamics of both temperature and precipitation, which are influenced by low frequency climate oscillations such as: El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Eastern Pacific Oscillation (EPO) and the Pacific-North American (PNA). This study investigate...
An AO is an example of teleconnection pattern in the northern hemisphere’s winter. In this study, the effect of AO on the monthly minimum temperatures in the North-East region of Iran is investigated. The required statistics, including statistics monthly minimum temperatures for 17 synoptic stations of the under study area was provided from Iran Meteorological Organization’s (IRMO). Pearson cor...
introduction long-term annual extreme climate events, especially temperature and precipitation, have generally been used as indicators for the assessment of climate change. one of the most changeable climatic variables in time and space is precipitation. there are great number of research papers focusing on extreme precipitation on global, regional and national scales have been written. the res...
A survey of the spatial and temporal behavior of the atmospheric general circulation as it relates to both polar regions is presented. The review is based on the European Centre for Medium-Range Weather Forecasts (ECMWF) 40-year reanalysis (ERA-40), updated using ECMWF operational analyses. The analysis spans 1960–2005 in the Northern Hemisphere, but is restricted to 1979–2005 in the Southern H...
Ground-based Fourier transform infrared (FTIR) measurements of solar absorption spectra can provide ozone total columns with a precision of 2 % but also independent partial column amounts in about four vertical layers, one in the troposphere and three in the stratosphere up to about 45 km, with a precision of 5–6 %. We use eight of the Network for the Detection of Atmospheric Composition Change...
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