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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 1,117 records · Page 62
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NASA NTRS1995

Response of the Tropical Boundary Layer to Weak Surface Forcing

During the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE), a series of airborne thermal infrared observations and in situ atmospheric measurements were made near the sea surface through heights exceeding 4 km. Air movements associated with the sea surface temperature and the marine atmospheric boundary layer were studied.

TOGA COARE sea surface temperature tropical weathe↗
NASA NTRS2013

Two Distinct Roles of Atlantic SSTs in ENSO Variability: North Tropical Atlantic SST and Atlantic Nino

Two distinct roles of the Atlantic sea surface temperatures (SSTs), namely, the North Tropical Atlantic (NTA) SST and the Atlantic Nino, on the El Nino-Southern Oscillation (ENSO) variability are investigated using the observational data from 1980 to 2010 and coupled model experiments. It appears that the NTA SST and the Atlantic Nino can be used as two independent predictors for predicting the development of ENSO events in the following season. Furthermore, they are likely to be linked to different types of El Nino events. Specifically, the NTA SST cooling during February, March, and April contributes to the central Pacific warming at the subsequent winter season, while the negative Atlantic Nino event during June, July, and August contributes to enhancing the eastern Pacific warming. The coupled model experiments support these results. With the aid of a lagged inverse relationship, the statistical forecast using two Atlantic indices can successfully predict various ENSO indices.

Atlantic Nino↗
NASA NTRS2013

Improving NASA's Multiscale Modeling Framework for Tropical Cyclone Climate Study

One of the current challenges in tropical cyclone (TC) research is how to improve our understanding of TC interannual variability and the impact of climate change on TCs. Recent advances in global modeling, visualization, and supercomputing technologies at NASA show potential for such studies. In this article, the authors discuss recent scalability improvement to the multiscale modeling framework (MMF) that makes it feasible to perform long-term TC-resolving simulations. The MMF consists of the finite-volume general circulation model (fvGCM), supplemented by a copy of the Goddard cumulus ensemble model (GCE) at each of the fvGCM grid points, giving 13,104 GCE copies. The original fvGCM implementation has a 1D data decomposition; the revised MMF implementation retains the 1D decomposition for most of the code, but uses a 2D decomposition for the massive copies of GCEs. Because the vast majority of computation time in the MMF is spent computing the GCEs, this approach can achieve excellent speedup without incurring the cost of modifying the entire code. Intelligent process mapping allows differing numbers of processes to be assigned to each domain for load balancing. The revised parallel implementation shows highly promising scalability, obtaining a nearly 80-fold speedup by increasing the number of cores from 30 to 3,335.

tropical cyclone interannual variability↗
NASA NTRS2014

ENSO Effect on East Asian Tropical Cyclone Landfall via Changes in Tracks and Genesis in a Statistical Model

Improvements on a statistical tropical cyclone (TC) track model in the western North Pacific Ocean are described. The goal of the model is to study the effect of El Nino-Southern Oscillation (ENSO) on East Asian TC landfall. The model is based on the International Best-Track Archive for Climate Stewardship (IBTrACS) database of TC observations for 1945-2007 and employs local regression of TC formation rates and track increments on the Nino-3.4 index and seasonally varying climate parameters. The main improvements are the inclusion of ENSO dependence in the track propagation and accounting for seasonality in both genesis and tracks. A comparison of simulations of the 1945-2007 period with observations concludes that the model updates improve the skill of this model in simulating TCs. Changes in TC genesis and tracks are analyzed separately and cumulatively in simulations of stationary extreme ENSO states. ENSO effects on regional (100-km scale) landfall are attributed to changes in genesis and tracks. The effect of ENSO on genesis is predominantly a shift in genesis location from the southeast in El Nino years to the northwest in La Nina years, resulting in higher landfall rates for the East Asian coast during La Nina. The effect of ENSO on track propagation varies seasonally and spatially. In the peak activity season (July-October), there are significant changes in mean tracks with ENSO. Landfall-rate changes from genesis- and track-ENSO effects in the Philippines cancel out, while coastal segments of Vietnam, China, the Korean Peninsula, and Japan show enhanced La Nina-year increases.

simulation↗
NASA NTRS2014

OH in the Tropical Upper Troposhere and Its Relationships to Solar Radiation and Reactive Nitrogen

In situ measurements of [OH], [HO2] (square brackets denote species concentrations), and other chemical species were made in the tropical upper troposphere (TUT). [OH] showed a robust correlation with solar zenith angle. Beyond this dependence, however, [HOx] ([OH] + [HO2]) only weakly responds to variations in its source and sink species. For example, at a given SZA, [HOx] was broadly independent of the product of [O3] and [H2O]. This suggests that [OH] is heavily buffered in the TUT. One important exception to this result is found in regions with very low [O3], [NO], and [NOy], where [OH] is highly suppressed, pointing to the critical role of NO in sustaining OH in the TUT.

Tropical upper troposphere↗
NASA NTRS2014

Sensitivity of Tropical Cyclones to Parameterized Convection in the NASA GEOS5 Model

The sensitivity of tropical cyclones (TCs) to changes in parameterized convection is investigated to improve the simulation of TCs in the North Atlantic. Specifically, the impact of reducing the influence of the Relaxed Arakawa-Schubert (RAS) scheme-based parameterized convection is explored using the Goddard Earth Observing System version5 (GEOS5) model at 0.25 horizontal resolution. The years 2005 and 2006 characterized by very active and inactive hurricane seasons, respectively, are selected for simulation. A reduction in parameterized deep convection results in an increase in TC activity (e.g., TC number and longer life cycle) to more realistic levels compared to the baseline control configuration. The vertical and horizontal structure of the strongest simulated hurricane shows the maximum lower-level (850-950hPa) wind speed greater than 60 ms and the minimum sea level pressure reaching 940mb, corresponding to a category 4 hurricane - a category never achieved by the control configuration. The radius of the maximum wind of 50km, the location of the warm core exceeding 10 C, and the horizontal compactness of the hurricane center are all quite realistic without any negatively affecting the atmospheric mean state. This study reveals that an increase in the threshold of minimum entrainment suppresses parameterized deep convection by entraining more dry air into the typical plume. This leads to cooling and drying at the mid- to upper-troposphere, along with the positive latent heat flux and moistening in the lower-troposphere. The resulting increase in conditional instability provides an environment that is more conducive to TC vortex development and upward moisture flux convergence by dynamically resolved moist convection, thereby increasing TC activity.

GEOS5↗
NASA NTRS2014

Comparison of Tropical Ozone from SHADOZ with Remote Sensing Retrievals from Suomi-npp Ozone Mapping Profile Suite (OMPS)

The Ozone Mapping Profile Suite (OMPS) was launched October 28, 2011 on-board the Suomi NPP satellite (http://npp.gsfc.nasa.gov). OMPS is the next generation total column ozone mapping instrument for monitoring the global distribution of stratospheric ozone. OMPS includes a limb profiler to measure the vertical structure of stratosphere ozone down to the mid-troposphere. This study uses tropical ozonesonde profile measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ, http://croc.gsfc.nasa.gov/shadoz) archive to evaluate total column ozone retrievals from OMPS and concurrent measurements from the Aura Ozone Monitoring Instrument (OMI), the predecessor of OMPS with a data record going back to 2004. We include ten SHADOZ stations that contain data overlapping the OMPS time period (2012-2013). This study capitalizes on the ozone profile measurements from SHADOZ to evaluate OMPS limb profile retrievals. Finally, we use SHADOZ sondes and OMPS retrievals to examine the agreement with the GEOS-5 Ozone Assimilation System (GOAS). The GOAS uses data from the OMI and the Microwave Limb Sounder (MLS) to constrain the total column and stratospheric profiles of ozone. The most recent version of the assimilation system is well constrained to the total column compared with SHADOZ ozonesonde data.

OMPS↗
NASA NTRS2014

Characteristics of Tropical Cyclones in High-resolution Models in the Present Climate

The global characteristics of tropical cyclones (TCs) simulated by several climate models are analyzed and compared with observations. The global climate models were forced by the same sea surface temperature (SST) fields in two types of experiments, using climatological SST and interannually varying SST. TC tracks and intensities are derived from each model's output fields by the group who ran that model, using their own preferred tracking scheme; the study considers the combination of model and tracking scheme as a single modeling system, and compares the properties derived from the different systems. Overall, the observed geographic distribution of global TC frequency was reasonably well reproduced. As expected, with the exception of one model, intensities of the simulated TC were lower than in observations, to a degree that varies considerably across models.

Tropical Cyclones↗
NASA NTRS2014

The Modulation of Tropical Storm Activity in the Western North Pacific by the Madden-Julian Oscillation in GEOS-5 AGCM Experiments

This study examines the influence of the Madden-Julian Oscillation (MJO) on tropical storm (TS) activity in the western North Pacific, using observations and GEOS-5 simulations at 50-km horizontal resolution. While GEOS-5 produces an MJO of faster propagation and weaker amplitude, it nevertheless reproduces the observed modulation of TS activity by the MJO with the highest TS genesis and increased track density in the active phases of MJO. The study suggests that the simulation of the sub-seasonal variability of TS activity could be improved by improving the simulations of the MJO in climate models.

Tropical Storm↗
NASA NTRS2014

The Modulation of Tropical Storm Activity in the Western North Pacific by the Madden-Julian Oscillation in GEOS-5 AGCM Experiments

This study examines the influence of the Madden-Julian Oscillation (MJO) on tropical storm (TS) activity in the western North Pacific, using observations and GEOS-5 simulations at 50-km horizontal resolution. While GEOS-5 produces an MJO of faster propagation and weaker amplitude, it nevertheless reproduces the observed modulation of TS activity by the MJO with the highest TS genesis and increased track density in the active phases of MJO. The study suggests that the simulation of the sub-seasonal variability of TS activity could be improved by improving the simulations of the MJO in climate models.

AGCM↗
NASA NTRS2016

Isotopic Ordering in Atmospheric O2 as a Tracer of Ozone Photochemistry and the Tropical Atmosphere

The distribution of isotopes within O2 molecules can be rapidly altered when they react with atomic oxygen. This mechanism is globally important: while other contributions to the global budget of O2 impart isotopic signatures, the O(3P) + O2 reaction resets all such signatures in the atmosphere on subdecadal timescales. Consequently, the isotopic distribution within O2 is determined by O3 photochemistry and the circulation patterns that control where that photochemistry occurs. The variability of isotopic ordering in O2 has not been established, however. We present new measurements of 18O18O in air (reported as delta36 values) from the surface to 33 km altitude. They confirm the basic features of the clumped-isotope budget of O2: Stratospheric air has higher delta36 values than tropospheric air (i.e., more 18O18O), reflecting colder temperatures and fast photochemical cycling of O3. Lower delta36 values in the troposphere arise from photochemistry at warmer temperatures balanced by the influx of high-delta36 air from the stratosphere. These observations agree with predictions derived from the GEOS-Chem chemical transport model, which provides additional insight. We find a link between tropical circulation patterns and regions where delta36 values are reset in the troposphere. The dynamics of these regions influences lapse rates, vertical and horizontal patterns of O2 reordering, and thus the isotopic distribution toward which O2 is driven in the troposphere. Temporal variations in delta36 values at the surface should therefore reflect changes in tropospheric temperatures, photochemistry, and circulation. Our results suggest that the tropospheric O3 burden has remained within a +/-10 percent range since 1978.

oxygen↗
NASA NTRS2014

Convective Influence and Transport Pathways Controlling the Tropical Distribution of Carbon Monoxide at 100 Hpa

Trajectory calculations with convective influence diagnosed from geostationary-satellite cloud measurements are used to evaluate the relative importance of different Tropical Tropopause Layer (TTL) transport pathways for establishing the distribution of carbon monoxide (CO) at 100 hPa as observed by the Microwave Limb Sounder (MLS) on board the Aura satellite. Carbon monoxide is a useful tracer for investigating TTL transport and convective influence because the CO lifetime is comparable to the time require for slow ascent through the TTL (a couple of months). Offline calculations of TTL radiative heating are used to determine the vertical motion field. The simple trajectory model does a reasonable job of reproducing the MLS CO distributions during Boreal wintertime and summertime. The broad maximum in CO concentration over the Pacific is primarily a result of the strong radiative heating (indicating upward vertical motion) associated with the abundant TTL cirrus in this region. Sensitivity tests indicate that the distinct CO maximum in the Asian monsoon anticyclone is strongly impacted by extreme convective systems with detrainment of polluted air above 360 K potential temperature. The relative importance of different CO source regions will also be discussed.

Tropical Tropopause Layer (TTL)↗