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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.

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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Representation of Modes of Variability in Six U.S. Climate Models

We compare the performance of several modes of variability across six U.S. climate modeling groups, with a focus on identifying robust improvements in recent models [including those participating in phase 6 of the Coupled Model Intercomparison Project (CMIP)] compared to previous versions. In particular, we examine the representation of the Madden–Julian oscillation (MJO), El Niño–Southern Oscillation (ENSO), the Pacific decadal oscillation (PDO), the quasi-biennial oscillation (QBO) in the tropical stratosphere, and the dominant modes of extratropical variability, including the southern annular mode (SAM), the northern annular mode (NAM) [and the closely related North Atlantic Oscillation (NAO)], and the Pacific–North American pattern (PNA). Where feasible, we explore the processes driving these improvements through the use of “intermediary” experiments that utilize model versions between CMIP3/5 and CMIP6 as well as targeted sensitivity experiments in which individual modeling parameters are altered. We find clear and systematic improvements in the MJO and QBO and in the teleconnection patterns associated with the PDO and ENSO. Some gains arise from better process representation, while others (e.g., the QBO) from higher resolution that allows for a greater range of interactions. Our results demonstrate that the incremental development processes in multiple climate model groups lead to more realistic simulations over time.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Are 100 Ensemble Members Enough to Capture the Remote Atmospheric Response to +2°C Arctic Sea Ice Loss?

This study presents results from the Polar Amplification Multimodel Intercomparison Project (PAMIP) single-year time-slice experiments that aim to isolate the atmospheric response to Arctic sea ice loss at global warming levels of +2°C. Using two general circulation models (GCMs), the ensemble size is increased up to 300 ensemble members, beyond the recommended 100 members. After partitioning the response in groups of 100 ensemble members, the reproducibility of the results is evaluated, with a focus on the response of the midlatitude jet streams in the North Atlantic and North Pacific. Both atmosphere-only and coupled ocean–atmosphere PAMIP experiments are analyzed. Substantial differences in the midlatitude response are found among the different experiment subsets, suggesting that 100-member ensembles are still significantly influenced by internal variability, which can mislead conclusions. Despite an overall stronger response, the coupled ocean–atmosphere runs exhibit greater spread due to additional ENSO-related internal variability when the ocean is interactive. The lack of consistency in the response is true for anomalies that are statistically significant according to Student’s t and false discovery rate tests. This is problematic for the multimodel assessment of the response, as some of the spread may be attributed to different model sensitivities whereas it is due to internal variability. Here, we propose a method to overcome this consistency issue that allows for more robust conclusions when only 100 ensemble members are used.

58 GEOSCIENCES↗
DOE OSTI2022

The Roles of Westward-Propagating Waves and the QBO in Limiting MJO Propagation

Abstract A recent study categorized the Madden–Julian oscillation (MJO) during boreal winter season into four types called stand, jump, slow, and fast MJO. This study focuses on the stand and jump MJO. Based on whether their convection penetrates the Maritime Continent (MC), stand and jump MJOs are seen as non-penetrating (NP) MJOs, while the other two are seen as eastward-penetrating (EP) MJOs. Results reveal the relative roles of the westward-propagating wave (WPW), as well as the QBO and ENSO, in limiting MJO propagation. Lack of the premoistening over the southern sea surface of the MC stops NP MJO from penetrating the MC. The active convection of the WPWs hinders the descending branch of the NP MJO circulation and therefore leads to the insufficient meridional advective moistening over the southern sea surface of the MC. The independent convection over the Pacific for jump MJOs is influenced by a combined effect of the QBO and ENSO. The tropopause instability induced by the MJO is found to significantly decouple from its convection over the Pacific in westerly QBO (QBOW) winters more than in easterly QBO (QBOE) winters. For jump MJOs, the independent convection over the central Pacific comes from local WPWs whose amplification and further development into deep convection are correlated to jump the MJOs’ decoupled tropopause instability. For stand MJOs, however, the seasonal-mean La Niña–like cool SST anomalies weaken the WPW activity over the central Pacific and confine WPWs within the western Pacific. Therefore, the decoupled tropopause instability of stand MJOs is out phase of WPWs and fails to induce an independent convection over the central Pacific.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Evolution of the Internal Climate Modes under Future Warming

Abstract Climate modes play an important role in weather and climate variability over multiple spatial and temporal scales. This research assesses Earth system model (ESM) projections of the spatiotemporal characteristics of key internal climate modes (NAM, SAM, PNA, ENSO, PDO, and AMO) under high (SSP585) and low (SSP126) radiative forcing scenarios and contextualizes those projections using historical fidelity. Time series analyses are used to assess trends and mode phase characteristics are summarized for the historical period and for the end of the twenty-first century. Spatial patterns are compared to infer morphological changes. Shifts in the power spectra are used to examine changes in variability at subannual, interannual, and interdecadal scales. Changes in time-lagged correlations are used to capture the evolution of first-order interactions. While differences in historical skill are predominantly ESM dependent, changing mode characteristics in a warmer climate also exhibit variability between individual ensemble realizations. NAM, SAM, and ENSO tend to evolve toward increased prevalence of the positive phase up to 2100 across the multimodel ensemble while the PNA and PDO exhibit little trend but increasing phase intensity. AMO characteristics are shown to depend on the method used to remove the external signal. ESMs that show higher historical fidelity tend to show more modest changes in those modes under global nonstationarity. Changes in mode interactions are found to be highly ESM dependent but exhibit broadly similar behavior to historical relationships. These findings have implications for our understanding of internal variability and make clear that the choice of ESM, and even the ESM realization, matters for applications of climate projections. Significance Statement Internal modes of variability are important to understand due to their impact on local, regional, and global weather and climate patterns. Future climate changes will not only be affected by the variability arising from these modes, but the modes will themselves change in response to the changing climate. Spatial and temporal aspects of the modes are assessed from projections of future climate and related to how well they are captured in the historical climate. This yields some measure of confidence in the changes exhibited by the models. In most cases, when historically skillful models exhibit changes that are different from those produced by less skillful models, they tend to produce more modest changes. These results, as well as the variability between model outcomes, mean decisions on which ESM to use for projections of the future climate matter significantly.

Meteorology & Atmospheric Sciences↗
DOE OSTI2024

Tropical Interbasin Interaction as Effective Predictors of Late-Spring Precipitation Variability in the Southern Great Plains

Abstract The southern Great Plains experience fluctuating precipitation extremes that significantly impact agriculture and water management. Despite ongoing efforts to enhance forecast accuracy, the underlying causes of these climatic phenomena remain inadequately understood. This study elucidates the relative influence of the tropical Pacific and Atlantic basins on April–May–June precipitation variability in this region. Our partial ocean assimilation experiments using the Community Earth System Model unveil the prominent role of interbasin interaction, with the Pacific and Atlantic contributing approximately 70% and 30%, respectively, to these interbasin contrasts. Our statistical analyses suggest that these tropical interbasin contrasts could serve as a more reliable indicator for late-spring precipitation anomalies than El Niño–Southern Oscillation. The conclusions are reinforced by analyses of seven climate forecasting systems within the North American Multi-Model Ensemble, offering an optimistic outlook for enhancing real-time forecasting of late-spring precipitation in the southern plains. However, the current predictive skills of the interbasin contrasts across the prediction systems are hindered by the lower predictability of the tropical Atlantic Ocean, pointing to the need for future research to refine climate prediction models further. Significance Statement Agriculture and infrastructure in the southern plains face challenges from severe late-spring precipitation extremes. Traditional predictors like El Niño–Southern Oscillation (ENSO) lose effectiveness during the critical spring-to-summer transition, creating a forecasting gap. This study introduces the concept of tropical interbasin interactions, known to enhance seasonal predictability for late-spring precipitation in the southern plains. Novel climate model experiments highlight contributions from the tropical Pacific and Atlantic, offering a promising predictability that potentially surpasses the limitations of ENSO-based predictions. These outcomes hold the potential for developing operational forecasts of late-spring precipitation anomalies in the southern plains, enabling proactive risk management.

Chikamoto, Yoshimitsu↗
DOE OSTI2022

Leaf sample detail, Feb2016-May2016, PA-SLZ, PA-PNM, PA-BCI: Panama

This data package contains details of the date, location, species and photographs of leaf samples collected on a monthly basis from Feb to May 2016 from Parque Natural Metropolitano (PA-PNM), Barro Colorado Island (PA-BCI) and Bosque Protector San Lorenzo (PA-SLZ) in Panama. Data from BCI only available for March. This data was collected as part of the 2016 El Niño-Southern Oscillation (ENSO) campaign. Included in this data package are an Excel file with data (2016ENSO_Panama_LeafSamples) and two Excel files with associated metadata. Sample photos are included in five zip files, organized by month and site. Also included is a Word document (Metadata_description_2016_ENSO_Panama) with details such as data collection methods, equipment used, and site information. Data to be used as a reference to linking related datasets including leaf water potential, leaf spectra, LMA, gas exchange and leaf chemistry (CHN, NSC). Most leaves were sampled from sunlit canopy trees. VERSION 2 update. The identification of a species from the PNM site has been corrected as follows: the identification of the tree initially identified as Pseudosamanea guachapele (ALBIED) has been revised to Albizia adinocephala (ALBIAD). The updated data package includes revised data, metadata and protocol documents updated to reflect this change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Diurnal leaf gas exchange survey, Feb2016-May2016, PA-SLZ, PA-PNM: Panama

This data package contains the results of a diurnal leaf gas exchange survey measured on sunlit canopy trees within the NGEE Tropics sites Parque Natural Metropolitano (PA-PNM) and Bosque Protector San Lorenzo (PA-SLZ) in Panama. Measurements were taken on a monthly basis from February to May of 2016. This data was collected as part of the 2016 El Niño-Southern Oscillation (ENSO) campaign. Included in this data package are two Excel files with data (2016ENSO_Panama_DiurnalGasEx, 2016ENSO_Panama_AreaCorrections) and additional Excel files with associated metadata. Also included is a Word document (Metadata_description_2016_ENSO_Panama) with details such as data collection methods, equipment used, and site information. See related datasets for further sample details, leaf water potential, LMA, leaf spectra, other gas exchange and leaf chemistry. VERSION 2 update. The identification of a species from the PNM site has been corrected as follows: the identification of the tree initially identified as Pseudosamanea guachapele (ALBIED) has been revised to Albizia adinocephala (ALBIAD). The updated data package includes revised data, metadata and protocol documents updated to reflect this change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Leaf mass area, Feb2016-May2016, PA-SLZ, PA-PNM, PA-BCI: Panama

This data package contains leaf mass data per unit area measured on a monthly basis from February to April, 2016, at the Bosque Protector San Lorenzo (PA-SLZ) and Parque Natural Metropolitano (PA-PNM) sites in Panama. Data from the Barro Colorado Island (PA-BCI) site are only available for March. This data was collected as part of the 2016 El Niño-Southern Oscillation (ENSO) campaign. Included in this data package are an Excel file with data (2016ENSO_Panama_LMA1) and two Excel files with associated metadata. Also included is a Word document (Metadata_description_2016_ENSO_Panama) with details such as data collection methods, equipment used, and site information. See related datasets for further sample details, leaf water potential, leaf spectra, gas exchange and leaf chemistry. VERSION 2 update. The identification of a species from the PNM site has been corrected as follows: the identification of the tree initially identified as Pseudosamanea guachapele (ALBIED) has been revised to Albizia adinocephala (ALBIAD). The updated data package includes revised data, metadata and protocol documents updated to reflect this change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Leaf spectra, Feb2016-April2016, PA-SLZ, PA-PNM, PA-BCI: Panama

This data package contains leaf spectra data measured on a monthly basis from February to April, 2016. Measurements were taken at the Bosque Protector San Lorenzo (SLZ), Barro Colorado Island (BCI) and Parque Natural Metropolitano (PNM) NGEE Tropics sites in Panama. Data from the BCI site are only available for March, 2016. Within the attached zip file are PDF manuals for instruments used, a guide to data collection protocol, and metadata files, including a PDF containing metadata for the 2016 ENSO gas exchange campaign. Also included is an additional zip file "2016_ENSO_BNL_Leaf_Spectra_Archive.zip" with data in .csv format organized by site. This data was collected as part of the 2016 ENSO campaign. See related datasets (existing and future) for further sample details, leaf water potential data, LMA, and gas exchange and leaf chemistry data. VERSION 2 update. The identification of a species from the PNM site has been corrected as follows: the identification of the tree initially identified as Pseudosamanea guachapele (ALBIED) has been revised to Albizia adinocephala (ALBIAD). The updated data package includes revised data, metadata and protocol documents updated to reflect this change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Leaf water potential, Feb2016-May2016, PA-SLZ, PA-PNM, PA-BCI: Panama

This data package contains leaf water potential data from the Barro Colorado Island (BCI), Parque Natural Metropolitano (PNM), and Bosque Protector San Lorenzo (SLZ) NGEE Tropics field sites in Panama. Pre-dawn and diurnal leaf water potential were measured on a monthly basis from February to May 2016 at SLZ and PNM. Data from BCI are only available for the month of March. This data was collected as part of the 2016 El Niño-Southern Oscillation (ENSO) campaign. Included in the attached zip file are data and metadata folders. The single data file "2016ENSO_Panama_LWP" has been provided in both Excel and CSV formats for usability purposes. The metadata file "Metadata_description_2016_ENSO_Panama" provides protocols, site descriptions, equipment information, and more, and has been provided in .docx and PDF file formats. See related datasets (existing and future) for further sample details, leaf spectra, leaf mass area (LMA), gas exchange and leaf chemistry data. VERSION 2 update. The identification of a species from the PNM site has been corrected as follows: the identification of the tree initially identified as Pseudosamanea guachapele (ALBIED) has been revised to Albizia adinocephala (ALBIAD). The updated data package includes revised data, metadata and protocol documents updated to reflect this change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Changing effects of external forcing on Atlantic–Pacific interactions

Recent studies have highlighted the increasingly dominant role of external forcing in driving Atlantic and Pacific Ocean variability during the second half of the 20th century. This paper provides insights into the underlying mechanisms driving interactions between modes of variability over the two basins. We define a set of possible drivers of these interactions and apply causal discovery to reanalysis data, two ensembles of pacemaker simulations where sea surface temperatures in either the tropical Pacific or the North Atlantic are nudged to observations, and a pre-industrial control run. We also utilize large-ensemble means of historical simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to quantify the effect of external forcing and improve the understanding of its impact. A causal analysis of the historical time series between 1950 and 2014 identifies a regime switch in the interactions between major modes of Atlantic and Pacific climate variability in both reanalysis and pacemaker simulations. A sliding window causal analysis reveals a decaying El Niño–Southern Oscillation (ENSO) effect on the Atlantic as the North Atlantic fluctuates towards an anomalously warm state. The causal networks also demonstrate that external forcing contributed to strengthening the Atlantic's negative-sign effect on ENSO since the mid-1980s, where warming tropical Atlantic sea surface temperatures induce a La Niña-like cooling in the equatorial Pacific during the following season through an intensification of the Pacific Walker circulation. The strengthening of this effect is not detected when the historical external forcing signal is removed in the Pacific pacemaker ensemble. The analysis of the pre-industrial control run supports the notion that the Atlantic and Pacific modes of natural climate variability exert contrasting impacts on each other even in the absence of anthropogenic forcing. The interactions are shown to be modulated by the (multi)decadal states of temperature anomalies of both basins with stronger connections when these states are “out of phase”. We show that causal discovery can detect previously documented connections and provides important potential for a deeper understanding of the mechanisms driving changes in regional and global climate variability.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1984

The appearance of sustained equatorial surface westerlies during the 1982 Pacific warm event

In June 1982 a band of anomalous southerly surface wind, extending from the equator as far south as the Tasman Sea, formed east of Australia (150 deg E to 160 deg E). This flow crossed the equator just before the appearance of sustained westerly winds on the equator somewhat west of the date line. Because these westerly winds induced the initial strong equatorial warming of the ocean east of the date line during the 1982 El Nino-Southern Oscillation (ENSO) event, the southerly jet appears to be an important atmospheric component leading to the onset of the vigorous phase of this event. Some historical evidence suggests that anomalous southerly winds in the same region occurred prior to the appearance of sustained equatorial westerly winds in the major ENSO events of 1957, 1965, and 1972.

Harrison, D. E.↗
NASA NTRS1986

Climate variability as observed by the Nimbus-7 ERB

Limits to the accuracy of the Earth Radiation Budget (ERB) data being obtained by the Nimbus-7 satellite are discussed with emphasis on the implications for the measured variabilities in the global climate. Error analyses are performed for both wide and narrow field of view instruments and the success of in-flight calibration efforts is noted. Alterations in the ERB due to the eruptions of El Chichon in 1982 and the 1982-1983 ENSO event are summarized, particularly the teleconnections which were observed during ENSO.

Ardanuy, P. E.↗
NASA NTRS1986

Earth rotation as a proxy for interannual variability in atmospheric circulation, 1860-present

Modern atmospheric and geodetic data sets have demonstrated that changes in the axial component of the atmosphere's angular momentum and in the rotation rate of the solid earth are closely coupled on time scales of up to several years. The feasibility of using a historical record of the earth's rotation as a proxy for year-to-year changes in the zonal wind field over the globe is examined. The bulk of the earth rotation series acquired for this purpose is based on telescopic observations of the occultation of stars by the moon; semiannual values of changes in the length of day derived from these observations have acceptably small errors from about 1860 onwards. These values are filtered to remove decade-scale fluctuations, which are driven primarily by nonatmospheric processes, and the resulting proxy series is examined to see if it contains a signal associated with one of the major modes of interannual variability in the atmosphere, namely that due to the El Nino/Southern Oscillation (ENSO). According to tests of statistical significance, such a signal is present in the historical earth rotation series, in that the day is typically longer during the year following an ENSO oceanic warm event than otherwise. Therefore other signals of interannual variability in the proxy series are considered. In particular, it is inferred that noteworthy trends in atmospheric interannual variability have occurred over the last century; for example, the decade of the 1920s was marked by much larger year-to-year changes in the zonal circulation over the globe than that of the 1940s. Based on modern atmospheric data, it is suggested that most of these circulation changes have resulted from anomalies in the region between 30 deg N and 30 deg S.

Salstein, David A.↗
NASA NTRS1987

Nimbus 7 earth radiation budget wide field of view climate data set improvement. II - Deconvolution of earth radiation budget products and consideration of 1982-1983 El Nino event

A deconvolution technique is employed that permits recovery of daily averaged earth radiation budget (ERB) parameters at the top of the atmosphere from a set of the Nimbus 7 ERB wide field of view (WFOV) measurements. Improvements in both the spatial resolution of the resultant fields and in the fidelity of the time averages is obtained. The algorithm is evaluated on a set of months during the period 1980-1983. The albedo, outgoing long-wave radiation, and net radiation parameters are analyzed. The amplitude and phase of the quasi-stationary patterns that appear in the spatially deconvolved fields describe the radiation budget components for 'normal' as well as the El Nino/Southern Oscillation (ENSO) episode years. They delineate the seasonal development of large-scale features inherent in the earth's radiation budget as well as the natural variability of interannual differences. These features are underscored by the powerful emergence of the 1982-1983 ENSO event in the fields displayed. The conclusion is that with this type of resolution enhancement, WFOV radiometers provide a useful tool for the observation of the contemporary climate and its variability.

Ardanuy, Phillip E.↗
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 NTRS1987

A model El Nino-Southern Oscillation

A coupled atmosphere-ocean model is developed and used to study the ENSO (El Nino/Southern Oscillation) phenomenon. With no anomalous external forcing, the coupled model reproduces certain key features of the observed phenomenon, including the recurrence of warm events at irregular intervals with a preference for three to four years. It is shown that the mean sea surface temperature, wind and ocean current fields determine the characteristic spatial structure of ENSO anomalies. The tendency for phase-locking of anomalies is explained in terms of a variation in coupling strength associated with the annual cycle in the mean fields. Sensitivity studies reveal that both the amplitude and the time scale of the oscillation are sensitive to several parameters that affect the strength of the atmosphere-ocean coupling. Stronger coupling implies larger oscillations with a longer timescale. A critical element of the model oscillation is the variability in the equatorial heat content of the upper ocean. Equatorial heat content increases prior to warm events and decreases sharply during the events. A theory for this variability and the associated transitions between non-El Nino and El Nino states is presented. Implications of the model results for the prediction of El Nino events are discussed.

Zebiak, Stephen E.↗
NASA NTRS1987

Evolution of the Southern Oscillation as observed by the Nimbus-7 ERB experiment

The Nimbus-7 satellite has been in a 955-km, sun-synchronous orbit since October 1978. The Earth Radiation Budget (ERB) experiment has taken approximately 8 years of high-quality data during this time, of which seven complete years have been archived at the National Space Science Data Center. A final reprocessing of the wide-field-of-view channel dataset is underway. Error analyses indicate a long-term stability of 1 percent better over the length of the data record. As part of the validation of the ERB measurements, the archived 7-year Nimbus-7 ERB dataset is examined for the presence and accuracy of interannual variations including the Southern Oscillation signal. Zonal averages of broadband outgoing longwave radiation indicate a terrestrial response of more than 2 years to the oceanic and atmospheric manifestations of the 1982-83 El Nino/Southern Oscillation (ENSO) event, especially in the tropics. This signal is present in monthly and seasonal averages and is shown here to derive primarily from atmospheric responses to adjustments in the Pacific Ocean. The calibration stability of this dataset thus provides a powerful new tool to examine the physics of the ENSO phenomena.

Ardanuy, Philip E.↗