Seasonal climate summary for the southern hemisphere (summer 2017–18): an exceptionally warm season for Australia – a short-lived and weak La Niña

2019 ◽  
Vol 69 (1) ◽  
pp. 351
Author(s):  
Tamika Tihema
Keyword(s):  
Southern Hemisphere ◽  
Warm Season ◽  
Summer Rainfall ◽  
La Niña ◽  
Atmospheric Circulation Patterns ◽  
La Nina ◽  
Circulation Patterns ◽  
Tasman Sea ◽  
Average Rainfall

This is a summary of the southern hemisphere atmospheric circulation patterns and meteorological indices for summer 2017–18; an account of seasonal rainfall and temperature for the Australian region is also provided. A short-lived and weak La Niña developed but decayed by the end of February 2018. Sea-surface temperatures were exceptionally warm in the Tasman Sea from late 2017 to early 2018. It was an exceptionally warm summer for Australia, and the third-warmest mean temperature on record for the nation. Summer rainfall was close to the long-term average for Australia, with aboveaverage rainfall in west and below-average rainfall in the east.

scholarly journals Quasi-stationary waves in the Southern Hemisphere during El Niño and La Niña events

2004 ◽  
Vol 22 (3) ◽  
pp. 789-806 ◽  
Author(s):  
V. Brahmananda Rao ◽  
J. P. R. Fernandez ◽  
S. H. Franchito
Keyword(s):  
South America ◽  
Southern Hemisphere ◽  
Rossby Wave ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Numerical Study ◽  
La Niña ◽  
Austral Spring ◽  
La Nina

Abstract. Characteristics of quasi-stationary (QS) waves in the Southern Hemisphere are discussed using 49 years (1950–1998) of NCEP/NCAR reanalysis data. A comparison between the stationary wave amplitudes and phases between the recent data (1979–1998) and the entire 49 years data showed that the differences are not large and the 49 years data can be used for the study. Using the 49 years of data it is found that the amplitude of QS wave 1 has two maxima in the upper atmosphere, one at 30°S and the other at 55°S. QS waves 2 and 3 have much less amplitude. Monthly variation of the amplitude of QS wave 1 shows that it is highest in October, particularly in the upper troposphere and stratosphere. To examine the QS wave propagation Plumb's methodology is used. A comparison of Eliassen-Palm fluxes for El Niño and La Niña events showed that during El Niño events there is a stronger upward and equatorward propagation of QS waves, particularly in the austral spring. Higher upward propagation indicates higher energy transport. A clear wave train can be identified at 300hPa in all the seasons except in summer. The horizontal component of wave activity flux in the El Niño composite seems to be a Rossby wave propagating along a Rossby wave guide, at first poleward until it reaches its turning latitude in the Southern Hemisphere midlatitudes, then equatorward in the vicinity of South America. The position of the center of positive anomalies in the austral spring in the El Niño years over the southeast Pacific, near South America, favors the occurrence of blocking highs in this region. This agrees with a recent numerical study by Renwick and Revell (1999). Key words. Meteorology and atmospheric dynamics (climatology; general circulation; ocean-atmosphere interactions)

scholarly journals Diversity of East China Summer Rainfall Change in Post-El Niño Summers

2020 ◽  
Vol 8 ◽  
Author(s):  
Wen Zhang ◽  
Xiaoye Zhou ◽  
Pang-Chi Hsu ◽  
Fei Liu
Keyword(s):  
El Niño ◽  
North China ◽  
El Nino ◽  
Summer Rainfall ◽  
La Niña ◽  
East China ◽  
La Nina ◽  
Huaihe River Valley ◽  
Precipitation Anomalies ◽  
Cluster 2

East China has experienced positive precipitation anomalies in post-El Niño summers, mainly in the Yangtze-Huaihe River Valley. This kind of monsoonal rainfall change induced by El Niño, however, is not always the same due to El Niño diversity and mean state change. Here, we use cluster analysis on the post-El Niño (PE) East China summer precipitation anomalies to identify the diversity of this El Niño-induced monsoon change. The result shows that PE East China summer rainfall anomalies mainly display three different modes for all selected 20 El Niño events from 1957 to 2016. Cluster 1 shows the middle and lower reaches of the Yangtze River demonstrate strong wet anomalies, while South and North China are dominated by dry anomalies, similar to a sandwich mode. Cluster 2 is distinguished by dry anomalies over South China and wet anomalies over North China, exhibiting a dipole mode. Compared with Cluster 1, the change caused by Cluster 3 is different, showing negative anomalies over the Yangtze-Huaihe River Valley. The three clusters are correlated with successive events of El Niño, a quick transfer to a strong La Niña and a quick transfer to a weak La Niña respectively. The associated anomalous anticyclone (AAC) focuses on (120°E, 20°N) in Cluster 1, which expands southward for Cluster 2 and moves eastward for Cluster 3. The feedback of AAC-sea surface temperature (SST) mainly works for supporting the AAC in Cluster 1, but it is weak for Cluster 2; the strong easterly anomalies related to La Niña contribute to the AAC location change for Cluster 2. Both AAC-SST feedback and easterly anomalies support the AAC of Cluster 3. The CMIP5 output can capture these diverse responses in circulation except that their simulated AAC for Cluster 1 is significant to the east of the observed.

scholarly journals The relationship between seasonal snow cover in Japan and recent climatic change

1993 ◽  
Vol 18 ◽  
pp. 166-172 ◽  
Author(s):  
Motori Nishimori ◽  
Ryuichi Kawamura
Keyword(s):  
Large Scale ◽  
Correlation Coefficients ◽  
The Sea Of Japan ◽  
Atmospheric Circulation Patterns ◽  
Teleconnection Patterns ◽  
Circulation Patterns ◽  
The Relationship ◽  
Seasonal Snow Cover ◽  
Rotated Empirical Orthogonal Function

Atmospheric circulation patterns associated with snowfall fluctuations in Japan are examined using a rotated empirical orthogonal function (EOF) analysis. We also compute correlation coefficients between the scores of EOF modes in the 500 hPa geopotential height field of the Northern Hemisphere (NH) and amounts of snowfall in Japan on annual, monthly and pentad time scales. It is found that recent variability of snowfall amount in Japan is closely related to the long-term variations of large-scale circulation patterns. It is suggested that the dominance of teleconnection patterns such as Pacific/North American (PNA) and Northern Asian (NA) are responsible for the increase of snowfall in the coastal regions of the Sea of Japan during the cold period for Japan (1977–86).

scholarly journals Can small pelagic fish landings be used as predictors of high-frequency oceanographic fluctuations in the 1–2 El Niño region?

2016 ◽  
Vol 42 ◽  
pp. 61-72 ◽  
Author(s):  
Franklin Isaac Ormaza-González ◽  
Alejandra Mora-Cervetto ◽  
Raquel María Bermúdez-Martínez ◽  
Mario Armando Hurtado-Domínguez ◽  
Manuel Raúl Peralta-Bravo ◽  
...  
Keyword(s):  
Linear Correlation ◽  
El Niño ◽  
El Nino ◽  
Pelagic Fish ◽  
La Niña ◽  
Negative Slope ◽  
South American ◽  
Small Pelagic Fish ◽  
La Nina

Abstract. A group of small pelagic fish captured between 1981 and 2012 within El Niño area 1–2 by the Ecuadorian fleet was correlated with the oceanographic Multivariate ENSO Index (MEI), and the Oceanographic El Niño Index (ONI) referred to El Niño region 3–4. For the period 1981–2012, total landings correlated poorly with the indexes, but during 2000–2012 (cold PDO) they proved to have a 14–29 % association with both indexes; the negative slope of the curves suggested higher landing during cold events (La Niña) and also indicated a tendency to decrease at extreme values ( >  0.5 and  < −1.0). Round herring (Etrumeus teres) fourth-quarter (Q4) landings were related to the MEI in a nonlinear analysis by up to 80 %. During moderate or strong La Niña events landings noticeably increased. Bullet tuna (Auxis spp.) catches showed a negative gradient from cold to warm episodes with an R2 of 0.149. For Chilean jack mackerel (Trachurus murphyi) irregular landings between 2003 and 2007 were observed and were poorly correlated (R2 < 0.1) with ONI or MEI. Anchovy (Engraulis ringens) captured in Ecuadorian waters since 2000 had an R2 of 0.302 and 0.156 for MEI and ONI, respectively, but showed a higher correlation with the cold Pacific Decadal Oscillation (PDO). South American pilchard (Sardinops sagax) was higher than −0.5 for the ONI and MEI, and landings dramatically decreased; however, Q4 landings correlated with ONI and MEI, with R2 of 0.109 and 0.225, respectively (n = 3). Linear correlation of Q4 indexes against the following year's Q1 landings had a linkage of up to 22 %; this species could therefore be considered a predictor of El Niño. Chub mackerel (Scomber japonicus) landings did not have a significant linear correlation with the indexes for 1981–2012 and therefore could not be considered a valid predictor. Chuhueco (Cetengraulis mysticetus) is a local species with high landings during El Niño years and, conversely, remarkably low landings during La Niña years. Additionally, chuhueco availability and landings were negatively affected by cold PDOs. Pacific thread herring (Opisthonema spp.) showed a 24 and 36 % relationship between landings (Q1) and the MEI and ONI (Q4). Therefore, results suggest that the South American pilchard and Pacific thread herring could be considered good species to use as predictors of El Niño in region 1–2 (Ecuador), especially when average Q4 MEI ∕ ONI is used against the next trimester Q1 landing. All species were prone to lower landings and/or fishing availability during strong–extreme events (ONI/MEI,  >  1.0 and  <  −1.0), and were also shown to be affected by the PDO. In the long term, landings decreased under warm PDO and vice versa, and therefore PDO fluctuations could be used to help manage these fisheries and to help the industry in long-term planning.

scholarly journals Seasonal climate summary for the southern hemisphere (winter 2016): a strong negative Indian Ocean Dipole brings wet conditions to Australia

2018 ◽  
Vol 68 (1) ◽  
pp. 101
Author(s):  
Blair Trewin
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
The Indian Ocean ◽  
Hemisphere Winter ◽  
Neutral Conditions

This is a summary of the southern hemisphere atmospheric circulation patterns and meteorological indices for winter 2016; an account of seasonal rainfall and temperature for the Australian region and the broader southern hemisphere is also provided. One of the strongest negative phases on record of the Indian Ocean Dipole (IOD) developed during the season, contributing to Australia&apos;s second wettest winter on record, with rainfall above average over the vast majority of the continent. Neutral conditions prevailed in the tropical Pacific following the end of a strong El Niño event in autumn 2016, but the continuing effect of the 2015-16 El Niño was still evident in southern hemisphere temperatures, which were at or near record high levels.

scholarly journals A Remote Sensing Survey of the Role of Landform on the Organization of Orographic Precipitation in Central and Southern Mexico

2008 ◽  
Vol 9 (6) ◽  
pp. 1267-1283 ◽  
Author(s):  
Jason P. Giovannettone ◽  
Ana P. Barros
Keyword(s):  
Spatial Variability ◽  
Large Scale ◽  
Spatial Scales ◽  
Coastal Region ◽  
La Niña ◽  
Southern Mexico ◽  
La Nina ◽  
Basin Scale ◽  
Sierra Madre ◽  
Average Rainfall

Abstract Data from NASA’s TRMM satellite and NOAA’s GOES satellites were used to survey the orographic organization of cloud precipitation in central and southern Mexico during the monsoon with two main objectives: 1) to investigate large-scale forcing versus local landform controls, and 2) to compare the results with previous work in the Himalayas. At large scales, the modes of spatial variability of cloudiness were estimated using the empirical orthogonal function (EOF) analysis of GOES brightness temperatures. Terrain modulation of synoptic-scale high-frequency variability (3–5- and 6–9-day cycles normally associated with the propagation of easterly waves) was found to cause higher dispersion in the EOF spectrum, with the first mode explaining less than 30% of the spatial variability in central and southern Mexico as opposed to 50% and higher in the Himalayas. A detailed analysis of the first three EOFs for 1999, an average La Niña year with above average rainfall, and for 2001, a weak La Niña year with below average rainfall, shows that landform (mountain peaks and land–ocean contrast) and large-scale circulation (moisture convergence) alternate as the key controls of regional hydrometeorology in dry and wet years, or as active and break (midsummer drought) phases of the monsoon, respectively. The diurnal cycle is the dominant time scale of variability in 2001, as it is during the midsummer drought in all years. Strong variability at time scales beyond two weeks is only present during the active phases of the monsoon. At the river basin scale, the data show increased cloudiness over the mountain ranges during the afternoon, which moves over the low-lying regions at the foot of the major orographic barriers [the Sierra Madre Occidental (SMO)/Sierra Madre del Sur (SMS) and Trans-Mexican Volcanic Belt (TMVB)], specifically the Balsas and the Rio de Santiago basins at nighttime and in the early morning. At the ridge–valley scale (∼100–200 km), robust day–night (ridge–valley) asymmetries suggest strong local controls on cloud and precipitation, with convective activity along the coastal region of the SMO and topographically forced convection at the foothills of headwater ridges in the Altiplano and the SMS. These day–night spatial shifts in cloudiness and precipitation are similar to those found in the Himalayas at the same spatial scales.

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