scholarly journals Consistency of Estimated Global Water Cycle Variations over the Satellite Era

2014 ◽  
Vol 27 (16) ◽  
pp. 6135-6154 ◽  
Author(s):  
F. R. Robertson ◽  
M. G. Bosilovich ◽  
J. B. Roberts ◽  
R. H. Reichle ◽  
R. Adler ◽  
...  
Keyword(s):  
El Niño ◽  
Land Surface ◽  
Decadal Variability ◽  
El Nino ◽  
La Niña ◽  
Specific Humidity ◽  
Near Surface ◽  
La Nina ◽  
Global Oceans ◽  
Global Water

Abstract Motivated by the question of whether recent interannual to decadal climate variability and a possible “climate shift” may have affected the global water balance, we examine precipitation minus evaporation (P – E) variability integrated over the global oceans and global land for the period 1979–2010 from three points of view—remotely sensed retrievals and syntheses over the oceans, reanalysis vertically integrated moisture flux convergence (VMFC) over land, and land surface models (LSMs) forced with observations-based precipitation, radiation, and near-surface meteorology. Over land, reanalysis VMFC and P − evapotranspiration (ET) from observationally forced LSMs agree on interannual variations (e.g., El Niño/La Niña events); however, reanalyses exhibit upward VMFC trends 3–4 times larger than P − ET trends of the LSMs. Experiments with other reanalyses using reduced observations show that upward VMFC trends in the full reanalyses are due largely to observing system changes interacting with assimilation model physics. The much smaller P − ET trend in the LSMs appears due to changes in frequency and amplitude of warm events after the 1997/98 El Niño, a result consistent with coolness in the eastern tropical Pacific sea surface temperature (SST) after that date. When integrated over the global oceans, E and especially P variations show consistent signals of El Niño/La Niña events. However, at scales longer than interannual there is considerable uncertainty especially in E. This results from differences among datasets in near-surface atmospheric specific humidity and wind speed used in bulk aerodynamic retrievals. The P variations, all relying substantially on passive microwave retrievals over ocean, also have uncertainties in decadal variability, but to a smaller degree.

scholarly journals Network analysis reveals strongly localized impacts of El Niño

2017 ◽  
Vol 114 (29) ◽  
pp. 7543-7548 ◽  
Author(s):  
Jingfang Fan ◽  
Jun Meng ◽  
Yosef Ashkenazy ◽  
Shlomo Havlin ◽  
Hans Joachim Schellnhuber
Keyword(s):  
El Niño ◽  
El Nino ◽  
Large Fraction ◽  
Surface Air Temperature ◽  
Climatic Conditions ◽  
La Niña ◽  
Near Surface ◽  
La Nina ◽  
Agriculture Industry ◽  
Global Impacts

Climatic conditions influence the culture and economy of societies and the performance of economies. Specifically, El Niño as an extreme climate event is known to have notable effects on health, agriculture, industry, and conflict. Here, we construct directed and weighted climate networks based on near-surface air temperature to investigate the global impacts of El Niño and La Niña. We find that regions that are characterized by higher positive/negative network “in”-weighted links are exhibiting stronger correlations with the El Niño basin and are warmer/cooler during El Niño/La Niña periods. In contrast to non-El Niño periods, these stronger in-weighted activities are found to be concentrated in very localized areas, whereas a large fraction of the globe is not influenced by the events. The regions of localized activity vary from one El Niño (La Niña) event to another; still, some El Niño (La Niña) events are more similar to each other. We quantify this similarity using network community structure. The results and methodology reported here may be used to improve the understanding and prediction of El Niño/La Niña events and also may be applied in the investigation of other climate variables.

scholarly journals Comments on “Characterizing ENSO Coupled Variability and Its Impact on North American Seasonal Precipitation and Temperature”

2017 ◽  
Vol 30 (1) ◽  
pp. 427-436 ◽  
Author(s):  
D. E. Harrison ◽  
Andrew M. Chiodi
Keyword(s):  
North American ◽  
El Niño ◽  
Land Surface ◽  
El Nino ◽  
Longwave Radiation ◽  
La Niña ◽  
Seasonal Temperature ◽  
The North ◽  
La Nina ◽  
Linear Approach

El Niño and La Niña seasonal weather anomaly associations provide a useful basis for winter forecasting over the North American regions where they are sufficiently strong in amplitude and consistent in character from one event to another. When the associations during La Niña are different than El Niño, however, the obvious quasi-linear-statistical approach to modeling them has serious shortcomings. The linear approach of L’Heureux et al. is critiqued here based on observed land surface temperature and tropospheric circulation associations over North America. The La Niña associations are quite different in pattern from their El Niño counterparts. The El Niño associations dominate the statistics. This causes the linear approach to produce results that are inconsistent with the observed La Niña–averaged associations. Further, nearly all the useful North American associations have been contributed by the subset of El Niño and La Niña years that are identifiable by an outgoing longwave radiation (OLR) El Niño index and a distinct OLR La Niña index. The remaining “non-OLR events” exhibit winter weather anomalies with large event-to-event variability and contribute very little statistical utility to the composites. The result is that the linear analysis framework is sufficiently unable to fit the observations as to question its utility for studying La Niña and El Niño seasonal temperature and atmospheric circulation relationships. An OLR-event based approach that treats La Niña and El Niño separately is significantly more consistent with, and offers an improved statistical model for, the observed relationships.

A Study of Dry Spells in Iran Based on Satellite Data and Their Relationship With ENSO

2021 ◽  
Author(s):  
Mohammad Rezaei ◽  
Efi Rousi ◽  
Elham Ghasemifar ◽  
Ali Sadeghi
Keyword(s):  
Satellite Data ◽  
El Niño ◽  
Arid Regions ◽  
El Nino ◽  
La Niña ◽  
Specific Humidity ◽  
La Nina ◽  
Dry Spells ◽  
Southern Half ◽  
Semi Arid

Abstract The study of Maximum number of Consecutive Dry Days (MCDDs) is one approach to analyse precipitation behavior in arid and semi-arid regions of Iran. This study is a first attempt to investigate the MCDDs and their relationship with the El Niño/Southern Oscillation (ENSO) in winter months over Iran. The study was carried out using Tropical Rainfall Measuring Mission (TRMM) satellite data on a daily basis at 1° latitude × 1° longitude spatial resolution and reanalysis data for the period 1998-2019. Results showed that the highest values of MCDDs are observed in southeastern Iran and the lowest in northwestern Iran. Based on the coefficients of the linear trend of the MCDDs, the significant increasing trends are remarkably more abundant than declining trends, especially in the northern half of the country in December and January. The results regarding the relationship between ENSO and MCDDs indicated a non-stationary behavior, with significant negative correlation for December (especially in southwest) and positive correlation for January and February (especially in southeast). The largest differences in the correlation coefficients were observed between December and January. In general, during El Niño (La Niña) phases, the length of MCDDs decreases (increases) in December and increases (decreases) in January especially in the southern half. By comparing different large-scale climate parameters for the two months, we found that during El Niño (La Niña) phases, a negative (positive) anomaly of geopotential height, and a positive (negative) anomaly of zonal wind and specific humidity are observed over the region in December, while the opposite situation occurs in January. The innovation of this study is the use of satellite data that provide a continuous spatial coverage of the region and the consideration of the ENSO teleconnection pattern in regards to dry spells. We find that El Niño (La Niña) has contradictory effects on MCDDs in different winter months in the southern half of the country. These findings are of great importance for a country like Iran that lies in arid and semi-arid regions, as they can be useful for water resources management.

scholarly journals Visualizing the Large-Scale Patterns of ENSO-Related Climate Anomalies in North America

2009 ◽  
Vol 13 (3) ◽  
pp. 1-50 ◽  
Author(s):  
Jacqueline J. Shinker ◽  
Patrick J. Bartlein
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Precipitation Anomaly ◽  
La Niña ◽  
Specific Humidity ◽  
Spatial And Temporal Variability ◽  
Climate Anomalies ◽  
Enso Events ◽  
La Nina

Abstract The variations of large-scale climatic controls and surface responses through the annual cycle during strong positive (El Niño) and negative (La Niña) phase ENSO events are analyzed to assess the within-year and among-year variations of climate anomalies. Data from the NCEP–NCAR reanalysis project are presented as small-multiple maps to illustrate the spatial and temporal variability in North American climate associated with extreme phases of ENSO. Temperature, mean sea level pressure, 500-mb geopotential heights, and 850-mb specific humidity have composite-anomaly patterns that exhibit the greatest degree of spatial and temporal coherence. In general, the composite-anomaly patterns for El Niño and La Niña events are of opposite sign, with stronger, more spatially coherent anomalies occurring during El Niño events than during La Niña events. However, the strength and coherency of the precipitation anomaly patterns are reduced in the interior intermountain west during both positive and negative phase of ENSO. The variations in precipitation anomalies are compared to the 500-mb omega and 850-mb specific humidity composite-anomaly patterns, which provide information on the controls of precipitation by large-scale vertical motions and moisture availability thus providing information on the specific mechanisms associated with precipitation variability during ENSO events.

scholarly journals The role of the Amazon Basin moisture in the atmospheric branch of the hydrological cycle: a Lagrangian analysis

2014 ◽  
Vol 18 (7) ◽  
pp. 2577-2598 ◽  
Author(s):  
A. Drumond ◽  
J. Marengo ◽  
T. Ambrizzi ◽  
R. Nieto ◽  
L. Moreira ◽  
...  
Keyword(s):  
El Niño ◽  
Amazon Basin ◽  
Hydrological Cycle ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Specific Humidity ◽  
Tropical Atlantic ◽  
La Nina

Abstract. We used a Lagrangian model (FLEXPART) together with the 1979–2012 ERA-Interim reanalysis data to investigate the role of the moisture in the Amazon Basin in the regional hydrological budget over the course of the year. FLEXPART computes budgets of evaporation minus precipitation by calculating changes in the specific humidity along forward and backward trajectories. The tropical Atlantic is the most important remote moisture source for the Amazon Basin. The tropical North Atlantic (NA) mainly contributed during the austral summer, while the contribution of the tropical South Atlantic (SA) prevailed for the remainder of the year. At the same time, the moisture contribution from the Amazon Basin itself is mainly for moisture supplying the southeastern South America. The 33-year temporal domain allowed the investigation of some aspects of the interannual variability of the moisture transport over the basin, such as the role of the El Niño Southern Oscillation (ENSO) and the Atlantic Meridional Mode (AMM) on the hydrological budget. During the peak of the Amazonian rainy season (from February to May, FMAM) the AMM is associated more with the interannual variations in the contribution from the tropical Atlantic sources, while the transport from the basin towards the subtropics responds more to the ENSO variability. The moisture contribution prevailed from the SA (NA) region in the years dominated by El Niño/positive AMM (La Niña/negative AMM) conditions. The transport from the Amazon towards the subtropics increased (reduced) during El Niño (La Niña) years.

scholarly journals Asymmetric Modulation of El Niño and La Niña and the Linkage to Tropical Pacific Decadal Variability

2017 ◽  
Vol 30 (12) ◽  
pp. 4705-4733 ◽  
Author(s):  
Yuko M. Okumura ◽  
Tianyi Sun ◽  
Xian Wu
Keyword(s):  
El Niño ◽  
Decadal Variability ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
La Niña ◽  
Climate System Model ◽  
Pacific Decadal Variability ◽  
La Nina ◽  
Leading Mode

El Niño–Southern Oscillation (ENSO) in a 1300-yr preindustrial control simulation of the Community Climate System Model, version 4 (CCSM4), exhibits distinct modulation in association with tropical Pacific decadal variability (TPDV). The frequency and duration of El Niño events modulate with changes in the interbasin sea surface temperature (SST) gradient related to the leading mode of TPDV, which resembles the interdecadal Pacific oscillation (IPO). La Niña shows similar changes with the IPO but is also controlled by changes in El Niño that often precedes La Niña, and these effects tend to cancel each other. The amplitude of ENSO, on the other hand, is closely related to the second leading mode of TPDV that affects the zonal and meridional contrast of tropical Pacific climate. Significant changes in the pattern and seasonal evolution related to this TPDV mode are found mainly for El Niño because of the nonlinear relation between the atmospheric deep convection and SSTs. The resultant changes in the amplitude of El Niño, in turn, affect the amplitude and duration of the following La Niña, as well as the asymmetry in their patterns and duration. The decadal ENSO modulation associated with both TPDV modes is not symmetrical between El Niño and La Niña and thus is not likely to occur solely as a result of random variability. The patterns of TPDV in CCSM4 have resemblance to those simulated by its atmospheric component coupled to a slab ocean model, suggesting that TPDV induced by stochastic atmospheric variability interacts with the ENSO dynamics.

scholarly journals The role of the South Pacific in modulating Tropical Pacific variability

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Christine T. Y. Chung ◽  
Scott B. Power ◽  
Arnold Sullivan ◽  
François Delage
Keyword(s):  
El Niño ◽  
Decadal Variability ◽  
El Nino ◽  
South Pacific ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
La Niña ◽  
The South ◽  
La Nina ◽  
Sst Anomalies

AbstractTropical Pacific variability (TPV) heavily influences global climate, but much is still unknown about its drivers. We examine the impact of South Pacific variability on the modes of TPV: the El Niño-Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO). We conduct idealised coupled experiments in which we suppress temperature and salinity variability at all oceanic levels in the South Pacific. This reduces decadal variability in the equatorial Pacific by ~30% and distorts the spatial pattern of the IPO. There is little change to overall interannual variability, however there is a decrease in the magnitude of the largest 5% of both El Niño and La Niña sea-surface temperature (SST) anomalies. Possible reasons for this include: (i) reduced decadal variability means that interannual SST variability is superposed onto a ‘flatter’ background signal, (ii) suppressing South Pacific variability leads to the alteration of coupled processes linking the South and equatorial Pacific. A small but significant mean state change arising from the imposed suppression may also contribute to the weakened extreme ENSO SST anomalies. The magnitude of both extreme El Niño and La Niña SST anomalies are reduced, and the associated spatial patterns of change of upper ocean heat content and wind stress anomalies are markedly different for both types of events.

scholarly journals On the Investigation of the Typology of Fog Events in an Arid Environment and the Link with Climate Patterns

2020 ◽  
Vol 148 (8) ◽  
pp. 3181-3202 ◽  
Author(s):  
T. S. Mohan ◽  
Marouane Temimi ◽  
R. S. Ajayamohan ◽  
Narendra Reddy Nelli ◽  
Ricardo Fonseca ◽  
...  
Keyword(s):  
United Arab Emirates ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Arid Environment ◽  
Reanalysis Data ◽  
La Niña ◽  
Radiation Fog ◽  
Near Surface ◽  
La Nina

Abstract The central aim of this work is to investigate the characteristics of fog events over the United Arab Emirates (UAE) and identify the underlying physical processes responsible for fog initiation and dissipation. To achieve this, hourly meteorological measurements at eight airport stations, along with ERA5 reanalysis data (1995–2018), are utilized. The analysis indicates the dominance of radiation fog (RAD) as, on average, 70% of the observed events fall under this category. Fog in the UAE typically forms between 2000 and 0200 local time (LT) and dissipates between 0600 and 0900 LT. During a typical dense fog event recorded during 22–23 December 2017, cooling and moistening tendencies of up to 1.2 K h−1 and 0.7 g kg−1 h−1 are observed ~5–6 h before fog onset. In the vertical, a dry and warm layer above 750 hPa gradually descends from above 500 hPa to promote the development of fog. Similar conclusions are reached when analyzing composites of fog events. Further, the variability of fog occurrence associated with El Niño–Southern Oscillation (ENSO) patterns is explored. It is concluded that the El Niño (warm) and La Niña (cold) phases exhibit very different spatial characteristics with respect to surface meteorological variables. In particular, during El Niño events, the near-surface atmosphere is cooler and moister compared to La Niña events, favoring RAD fog formation over the UAE. Besides, fog events during El Niño years tend to last longer compared to La Niña years due to an earlier onset.

scholarly journals Two Types of the Western Pacific Pattern, Their Climate Impacts, and the ENSO Modulations

2019 ◽  
Vol 32 (3) ◽  
pp. 823-841 ◽  
Author(s):  
Ying Dai ◽  
Benkui Tan
Keyword(s):  
North American ◽  
El Niño ◽  
El Nino ◽  
Climate Impacts ◽  
La Niña ◽  
Western Pacific ◽  
Near Surface ◽  
La Nina ◽  
Enso Modulation ◽  
The Western Pacific

The western Pacific (WP) pattern is a major teleconnection pattern that influences the wintertime Northern Hemisphere climate variations. Based on daily NCEP–NCAR reanalysis data, this study examines the climate impacts and the El Niño–Southern Oscillation (ENSO) modulation of two types of the WP pattern. The result shows that the WP patterns may arise from precursory disturbances over Asia and the North Pacific or from the Pacific–North American (PNA) pattern of the same polarity as or opposite polarity to that of the WP patterns. Among these WP patterns, the WP patterns that arise from the PNA pattern of the same polarity are most influential on North American near-surface and polar stratospheric air temperatures; furthermore, their frequency of occurrence, amplitude, and duration can be affected by ENSO phases: the positive WP patterns occur more frequently with larger amplitude and longer duration in El Niño than in La Niña; and the negative WP patterns occur less frequently with smaller amplitude and shorter duration in El Niño than in La Niña. The above findings suggest that the PNA pattern plays a crucial role in the climate impacts and the ENSO modulation of the WP patterns.

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