Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Teleconnections”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

The Role of the Stratosphere in Teleconnections Arising From Fast and Slow MJO Episodes

The Madden-Julian Oscillation (MJO) can influence the extratropical circulation on timescales up to several weeks, with a dependence on the MJO characteristics: MJO episodes that propagate slowly across the Maritime Continent have a stronger impact on Euro-Atlantic weather than fast MJO episodes. While the tropospheric pathway for MJO teleconnections with varying phase speeds is well understood, in this study, we investigate the contribution of the Northern Hemisphere stratospheric pathway for fast versus slow MJO episodes. During slow MJO episodes, Phases 5–6 lead to increased upward wave propagation in the North Pacific sector, and subsequently enhanced heat flux at 100 hPa, leading to the weakening of the polar vortex. The results suggest a clear role of stratosphere-troposphere coupling for slow MJO episodes, which is proposed as a mechanism for anomalously strong positive polar cap height anomalies in MJO Phases 7–8.

Priyanka Yadav↗
NASA NTRSDate not supplied

Ocean-Land Teleconnections and Chaotic Atmospheric Variability in Climate Models, with Implications for Real-World Behavior

This study introduces a unique approach to estimating a fundamental but unmeasurable property of Nature: ρo 2 , the fraction of the variance of a given meteorological variable that is determined by boundary forcing (specifically, SSTs) as opposed to chaotic atmospheric dynamics. Here, we focus on continental monthly-averaged near-surface air temperature, or T2M. Rather than determining the fractions of SST-explained T2M variance found for a specific atmospheric general circulation model (AGCM) and then assuming that these fractions also represent Nature, we perform an analysis that entails: (i) evaluating a specific AGCM’s ability to capture observed variability with an infinite number of ensemble members, (ii) quantifying the degree to which different modeling systems agree on SST-land teleconnections, and (iii) combining these results into our novel estimates of ρo 2 . The derived ρo 2 fields suggest, with caveats, that AGCMs tend to overestimate the fraction of explained T2M variance (the signal-to-total variance ratio) in the Tropics.

Randal D Koster↗
DOE OSTI2024

Modeling Spatial Asymmetries in Teleconnected Extreme Temperatures

Abstract Combining strengths from deep learning and extreme value theory can help describe complex relationships between variables where extreme events have significant impacts (e.g., environmental or financial applications). Neural networks learn complicated nonlinear relationships from large datasets under limited parametric assumptions. By definition, the number of occurrences of extreme events is small, which limits the ability of the data-hungry, nonparametric neural network to describe rare events. Inspired by recent extreme cold winter weather events in North America caused by atmospheric blocking, we examine several probabilistic generative models for the entire multivariate probability distribution of daily boreal winter surface air temperature. We propose metrics to measure spatial asymmetries, such as long-range anticorrelated patterns that commonly appear in temperature fields during blocking events. Compared to vine copulas, the statistical standard for multivariate copula modeling, deep learning methods show improved ability to reproduce complicated asymmetries in the spatial distribution of ERA5 temperature reanalysis, including the spatial extent of in-sample extreme events.

Krock, Mitchell L.↗
NASA NTRS1986

Tropical-extratropical geopotential height teleconnections during the Northern Hemisphere winter

Simultaneous and lagged correlation patterns between height anomalies in the Northern Hemisphere (NH) or in the Southern Hemisphere (SH) and height anomalies at tropical stations in two major tropical precipitation zones (the Indochina maritime continent and Africa) were examined. The height anomalies among the tropical stations in these zones and its nearby Pacific Ocean, South America, and Africa are strongly correlated; they are also correlated with stations in Australia and the North PLacific Ocean. The correlations between height anomalies at any of these stations and NH height anomalies show a well-defined global pattern with major features concentrated in the United States and adjacent oceans. Depending upon the location of the stations, the pattern is either a Pacific North American (PNA), a Tropical NH (TNH), or a mixed pattern having both elements. During the El Nino/Southern Oscillation (ENSO) years both TNH and PNA patterns appear in simultaneous and lagged maps, but in non-ENSO years the TNH is weak in simultaneous charts.

Mo, Kingtse C.↗
NASA NTRS2000

Teleconnection Linking Asian/Pacific Monsoon Variability and Summertime Droughts and Floods Over the United States

Major droughts and floods over the U.S. continent may be related to a far field energy source in the Asian Pacific. This is illustrated by two climate patterns associated with summertime rainfall over the U.S. and large-scale circulation on interannual timescale. The first shows an opposite variation between the drought/flood over the Midwest and that over eastern and southeastern U.S., coupled to a coherent wave pattern spanning the entire East Asia-North Pacific-North America region related to the East Asian jetstream. The second shows a continental-scale drought/flood in the central U.S., coupled to a wavetrain linking Asian/Pacific monsoon region to North America.

Lau, K. M.↗
NASA NTRS2000

Earth System Science at NASA: Teleconnections Between Sea Surface Temperature and Epidemics in Africa

The research carried out in the Earth Sciences in NASA and at NASA's Goddard Space Flight Center will be the focus of the presentations. In addition, one research project that links sea surface temperature to epidemics in Africa will be highlighted. At GSFC research interests span the full breath of disciplines in Earth Science. Branches and research groups focus on areas as diverse as planetary geomagnetics and atmospheric chemistry. These organizations focus on atmospheric sciences (atmospheric chemistry, climate and radiation, regional processes, atmospheric modeling), hydrological sciences (snow, ice, oceans, and seasonal-to-interannual prediction), terrestrial physics (geology, terrestrial biology, land-atmosphere interactions, geophysics), climate modeling (global warming, greenhouse gases, climate change), on sensor development especially using lidar and microwave technologies, and on information technologies, that enable support of scientific and technical research.

Meeson, Blanche W.↗
NASA NTRS1998

Spaceborne Sensors Observe El Nino Teleconnection

The anomalous warming along the equator is part of the developing El Nino condition and is related to the westerly wind anomalies and the relaxation of the trade-winds over the equatorial Pacific.

El Nino Spaceborne sensors↗
NASA NTRS1999

Teleconnection of the 1997 El Nino Observed by Spaceborne Sensors and the Dacadal Anomalies in the Northeast Pacific

Liu et al.[1998] (hereafter referred as LTH), superimposed wind velocity anomalies observed by the NASA Scatterometer (NSCAT) on the map of sea surface temperature (SST) anomalies observed by the Advanced Very High Resolution Radiometer (AVHRR) in the Pacific at the end of May 1997, and illustrated that the three regions of anomalous warming in the North Pacific Ocean are related to wind anomalies through different mechanisms.

global change Empirical Orthogonal Function (EOF) ↗
NASA NTRS2010

The 2010 Pakistan Flood and the Russia Heat Wave: Teleconnection of Extremes

The Pakistan flood and the Russia heat wave/Vvild fires of the summer of2010 were two of the most extreme, and catastrophic events in the histories of the two countries occurring at about the same time. To a casual observer, the timing may just be a random coincidence of nature, because the two events were separated by long distances, and represented opposite forces of nature, i.e., flood vs. drought, and water vs. fire. In this paper, using NASA satellite and NOAA reanalysis data, we presented observation evidences that that the two events were indeed physically connected.

Lau, William K.↗
NASA NTRS2011

Climate Teleconnections and Recent Patterns of Human and Animal Disease Outbreaks

Recent clusters of outbreaks of mosquito-borne diseases (Rift Valley fever and chikungunya) in Africa and parts of the Indian Ocean islands illustrate how interannual climate variability influences the changing risk patterns of disease outbreaks. Extremes in rainfall (drought and flood) during the period 2004 - 2009 have privileged different disease vectors. Chikungunya outbreaks occurred during the severe drought from late 2004 to 2006 over coastal East Africa and the western Indian Ocean islands and in the later years India and Southeast Asia. The chikungunya pandemic was caused by a Central/East African genotype that appears to have been precipitated and then enhanced by global-scale and regional climate conditions in these regions. Outbreaks of Rift Valley fever occurred following excessive rainfall period from late 2006 to late 2007 in East Africa and Sudan, and then in 2008 - 2009 in Southern Africa. The shift in the outbreak patterns of Rift Valley fever from East Africa to Southern Africa followed a transition of the El Nino/Southern Oscillation (ENSO) phenomena from the warm El Nino phase (2006-2007) to the cold La Nina phase (2007-2009) and associated patterns of variability in the greater Indian Ocean basin that result in the displacement of the centres of above normal rainfall from Eastern to Southern Africa. Understanding the background patterns of climate variability both at global and regional scale and their impacts on ecological drivers of vector borne-diseases is critical in long-range planning of appropriate response and mitigation measures.

Anyamba, Assaf↗
NASA NTRS2011

Teleconnection, Regime Shift, and Predictability of Climate Extremes: A Case Study for the Russian Heat Wave and Pakistan Flood in Summer 2010

In this talk, we present observational evidence showing that the two major extremes events of the summer of 2010, i.e., the Russian heat wave and the Pakistan flood were physically connected. We find that the Pakistan flood was contributed by a series of unusually heavy rain events over the upper Indus River Basin in July-August. The rainfall regimes shifted from an episodic heavy rain regime in mid-to-late July to a steady heavy rain regime in August. An atmospheric Rossby wave associated with the development of the Russian heat wave was instrumental in spurring the episodic rain events , drawing moisture from the Bay of Bengal and the northern Arabian Sea. The steady rain regime was maintained primarily by monsoon moisture surges from the deep tropics. From experiments with the GEOS-5 forecast system, we assess the predictability of the heavy rain events associated with the Pakistan flood. Preliminary results indicate that there are significantly higher skills in the rainfall forecasts during the episodic heavy rain events in July, compared to the steady rain period in early to mid-August. The change in rainfall predictability may be related to scale interactions between the extratropics and the tropics resulting in a modulation of rainfall predictability by the circulation regimes.

Lau, W. K.↗
NASA NTRS2012

The 2010 Pakistan Flood and Russian Heat Wave: Teleconnection of Hydrometeorological Extremes

In this paper, preliminary results are presented showing that the two record-setting extreme events during 2010 summer (i.e., the Russian heat wave-wildfires and Pakistan flood) were physically connected. It is found that the Russian heat wave was associated with the development of an extraordinarily strong and prolonged extratropical atmospheric blocking event in association with the excitation of a large-scale atmospheric Rossby wave train spanning western Russia, Kazakhstan, and the northwestern China-Tibetan Plateau region. The southward penetration of upper-level vorticity perturbations in the leading trough of the Rossby wave was instrumental in triggering anomalously heavy rain events over northern Pakistan and vicinity in mid- to late July. Also shown are evidences that the Russian heat wave was amplified by a positive feedback through changes in surface energy fluxes between the atmospheric blocking pattern and an underlying extensive land region with below-normal soil moisture. The Pakistan heavy rain events were amplified and sustained by strong anomalous southeasterly flow along the Himalayan foothills and abundant moisture transport from the Bay of Bengal in connection with the northward propagation of the monsoonal intraseasonal oscillation.

Lau, William K. M.↗
NASA NTRS2014

Use of Machine Learning Techniques for Iidentification of Robust Teleconnections to East African Rainfall Variability in Observations and Models

Providing advance warning of East African rainfall variations is a particular focus of several groups including those participating in the Famine Early Warming Systems Network. Both seasonal and long-term model projections of climate variability are being used to examine the societal impacts of hydrometeorological variability on seasonal to interannual and longer time scales. The NASA / USAID SERVIR project, which leverages satellite and modeling-based resources for environmental decision making in developing nations, is focusing on the evaluation of both seasonal and climate model projections to develop downscaled scenarios for using in impact modeling. The utility of these projections is reliant on the ability of current models to capture the embedded relationships between East African rainfall and evolving forcing within the coupled ocean-atmosphere-land climate system. Previous studies have posited relationships between variations in El Niño, the Walker circulation, Pacific decadal variability (PDV), and anthropogenic forcing. This study applies machine learning methods (e.g. clustering, probabilistic graphical model, nonlinear PCA) to observational datasets in an attempt to expose the importance of local and remote forcing mechanisms of East African rainfall variability. The ability of the NASA Goddard Earth Observing System (GEOS5) coupled model to capture the associated relationships will be evaluated using Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations.

Roberts, J. Brent↗
NASA NTRS2014

Use of Machine Learning Techniques for Identification of Robust Teleconnections to East African Rainfall Variability

Hidden Markov models can be used to investigate structure of subseasonal variability. East African short rain variability has connections to large-scale tropical variability. MJO - Intraseasonal variations connected with appearance of "wet" and "dry" states. ENSO/IOZM SST and circulation anomalies are apparent during years of anomalous residence time in the subseasonal "wet" state. Similar results found in previous studies, but we can interpret this with respect to variations of subseasonal wet and dry modes. Reveal underlying connections between MJO/IOZM/ENSO with respect to East African rainfall.

Roberts, J. Brent↗