Atlantic Multidecadal Oscillation (AMO) modulates North Atlantic atmospheric blocking

Atmospheric blocking over the high-latitude North Atlantic blocks the westerly jet stream, causing the eastward propagation of weather systems to stall for 7 days or so. An earlier study  by Häkkinen et al. (2011) used the 20th century atmospheric reanalysis product of NOAA (20CR) to show that the wintertime blocking frequency over high latitude North Atlantic covaries... Continue Reading →

Four types of the Madden-Julian Oscillation

Madden-Julian Oscillation (MJO) is the main mode of intraseasonal atmospheric variability in the tropical Indo-Pacific Oceans and the major source of subseasonal predictability of precipitation and extreme weather events in many parts of the globe. Although MJO is known as an eastward propagating equatorial atmospheric kelvin wave, not all MJO events are identical in terms of their strength... Continue Reading →

Extreme U.S. Great Plains heat waves are linked to East Asian Monsoon

Heat waves are the leading weather‐related cause of death in the U.S. For example, the most recent U.S. extreme heat waves that occurred over the Great Plains in 2011 and 2012 caused 362 deaths. These events are unusual and largely unpredictable beyond the synoptic time scale. However, their number and severity have increased and are projected... Continue Reading →

Recent intensification of Amazonian flooding extremes is linked to the tropical Atlantic warming and tropical Pacific cooling

The Amazonian River basin hosts the one of the major global deep tropical convective systems, and thus drives the global Hadley and Walker circulations and the global hydrological cycle. Changes in the water cycle and deep convection activity in this region are, however, largely affected by remote oceans, especially the tropical Pacific, via the Walker circulation.... Continue Reading →

El Nino-induced suppression of Atlantic ITCZ contributes to the spring warming of the tropical North Atlantic

It is a well-known phenomenon that the Tropical North Atlantic (TNA) warms in boreal spring and early summer (April – June) following El Nino peaks in boreal winter (Enfield and Mayer, 1997). This involves formation of the so-called extratropical atmospheric stationary Rossby wave trains from the tropical Pacific (e.g., Lee et al., 2008). A new paper published... Continue Reading →

Increasing frequency of North American winter extremes caused by the eastward shift of the North Pacific Oscillation

The North Pacific Oscillation (NPO) is a dipole oscillation of the sea level pressure (or the atmospheric mass) between the subpolar low and subtropical high over the North Pacific Ocean. A study published in Nature Climate Change showed that the center of the NPO shifted eastward during the recent decades (1995-2014), and thus increased the frequency of... Continue Reading →

Pantropical inter-ocean interactions & the rising influence of tropical Atlantic Ocean

Conventional view so far has been that El Nino - Southern Oscillation (ENSO) is largely responsible for energizing the dominant modes of SST variability  in the tropical Atlantic and Indian Oceans through changes in the Walker circulation and extratropical atmospheric waves. However, recent studies have shown that SST variability in the tropical Atlantic and Indian... Continue Reading →

Recent warming of the Indian Ocean suppresses the Indian summer monsoon circulation

A recent article published in Science Advances analyzed an atmospheric reanalysis dataset (MERRA2) covering the 1980–2016 period to show that a significant warming occurred in the Indian Ocean over the study period, and thus reduced the temperature difference between the Indian subcontinent and Indian Ocean in boreal summer. The reduced land-ocean temperature difference in turn produced anomalous... Continue Reading →

Arctic sea-ice decrease may suppress U.S. tornado activity in summer

The observed losses in  Arctic sea ice during the past decades have been linked to the relaxation of poleward thickness gradients (thus weakened zonal winds) and a slower eastward progression of Rossby waves in the upper-level, which help promote prolonged extreme weather conditions, such as heat waves, within the mid-latitudes (e.g., Francis & Vavrus, 2012). However, the background... Continue Reading →

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