Browse

You are looking at 101 - 110 of 118,421 items for

  • Refine by Access: All Content x
Clear All
Sukyoung Lee and Yohai Kaspi

Abstract

The structure and stability of Jupiter’s atmosphere is analyzed using transformed Eulerian mean (TEM) theory. Utilizing the ammonia distribution derived from microwave radiometer measurements of the Juno orbiter, the latitudinal and vertical distribution of the vertical velocity in the interior of Jupiter’s atmosphere is inferred. The resulting overturning circulation is then interpreted in the TEM framework to offer speculation of the vertical and meridional temperature distribution. At midlatitudes, the analyzed vertical velocity field shows Ferrel-cell-like patterns associated with each of the jets. A scaling analysis of the TEM overturning circulation equation suggests that in order for the Ferrel-cell-like patterns to be visible in the ammonia distribution, the static stability of Jupiter’s weather layer should be on the order of 1 × 10−2 s−1. At low latitudes, the ammonia distribution suggests strong upward motion, which is reminiscent of the rising branch of the Hadley cell where the static stability is weaker. Taken together, the analysis suggests that the temperature lapse rate in the midlatitudes is markedly smaller than that in the low latitudes. Because the cloud-top temperature is nearly uniform across all latitudes, the analysis suggests that in the interior of the weather layer, there could exist a temperature gradient between the low- and midlatitude regions.

Restricted access
Yajie Li, Amanda Lee Hughes, and Peter D. Howe

Abstract

Message diffusion and message persuasion are two important aspects of success for official risk messages about hazards. Message diffusion enables more people to receive lifesaving messages, and message persuasion motivates them to take protective actions. This study helps to identify win–win message strategies by investigating how an underexamined factor, message content that is theoretically important to message persuasion, influences message diffusion for official risk messages about heat hazards on Twitter. Using multilevel negative binomial regression models, the respective and cumulative effects of four persuasive message factors—hazard intensity, health risk susceptibility, health impact, and response instruction—on retweet counts were analyzed using a dataset of heat-related tweets issued by U.S. National Weather Service accounts. Two subsets of heat-related tweets were also analyzed: 1) heat warning tweets about current or anticipated extreme heat events and 2) tweets about nonextreme heat events. This study found that heat-related tweets that mentioned more types of persuasive message factors were retweeted more frequently, and so were two subtypes of heat-related tweets. Mentions of hazard intensity also consistently predicted increased retweet counts. Mentions of health impacts positively influenced message diffusion for heat-related tweets and tweets about nonextreme heat events. Mentions of health risk susceptibility and response instructions positively predicted retweet counts for tweets about nonextreme heat events and tweets about official extreme heat warnings, respectively. In the context of natural hazards, this research informs practitioners with evidence-based message strategies to increase message diffusion on social media. Such strategies also have the potential to improve message persuasion.

Restricted access
Qian Li, Matthew H. England, and Andrew McC. Hogg

Abstract

The Southern Ocean has undergone significant climate-related changes over recent decades, including intensified westerly winds and increased radiative heating. The interplay between wind-driven cooling and radiative warming of the ocean is complex and remains unresolved. In this study, idealized wind and thermal perturbations are analyzed in a global ocean–sea ice model at two horizontal resolutions: nominally, 1° and 0.1°. The sea surface temperature (SST) response shows a clear transition from a wind-driven cooling phase to a warming phase. This warming transition is largely attributed to meridional and vertical Ekman heat advection, which are both sensitive to model resolution due to the model-dependent components of temperature gradients. At higher model resolution, due to a more accurate representation of near-surface vertical temperature inversion and upward Ekman heat advection around Antarctica, the anomalous SST warming is stronger and develops earlier. The mixed layer depth at midlatitudes initially increases due to a wind-driven increase in Ekman transport of cold dense surface water northward, but then decreases when the thermal forcing drives enhanced surface stratification; both responses are more sensitive at lower model resolution. With the wind intensification, the residual overturning circulation increases less in the 0.1° case because of the adequately resolved eddy compensation. Ocean heat subduction penetrates along more tilted isopycnals in the 1° case, but it orients to follow isopycnal layers in the 0.1° case. These findings have implications for understanding the ocean response to the combined effects of Southern Hemisphere westerly wind changes and anthropogenic warming.

Restricted access
Julia Linder and Victoria Campbell-Arvai

Abstract

In the midwestern United States, intensifying impacts from climate change necessitate adaptation by the agricultural sector. Tree fruit agriculture is uniquely vulnerable to climate change due to the long-lived nature of perennial systems, yet very few studies have addressed how fruit growers perceive climate change and are responding to climate risks. For this study, 16 semistructured interviews were conducted with Michigan tree fruit growers to understand how their climate change beliefs, beliefs about adaptive actions, and climate-related risk perceptions influence adaptation behaviors. While there was a great deal of uncertainty about the anthropogenic nature of climate change, growers generally agreed that unprecedented changes in climate and weather patterns were occurring. Because of a perception of little control over future climate impacts, most growers reactively adapted to climate risks that negatively impacted their orchards by implementing measures such as frost protection, irrigation, pesticides, and crop insurance. This study highlighted that while proactive adaptations such as crop diversification, planting new varieties, and improving soil health will be necessary to increase farm resilience in the future, growers were unable to justify making these changes due to their uncertainty about future climate changes. The findings from this study highlight the need for future outreach efforts by university extension agents, private agricultural advisors, and federal and state agency advisors to provide educational information on the long-term impacts of climate change in order to help growers increase the resilience of their farm in the face of future climate impacts.

Restricted access
Muhammad Naufal Razin and Michael M. Bell

Abstract

Hurricane Ophelia (2005) underwent an unconventional eyewall replacement cycle (ERC) as it was a category-1 storm located over cold sea surface temperatures near 23°C. The ERC was analyzed using airborne radar, flight-level, and dropsonde data collected during the Hurricane Rainband and Intensity Change Experiment (RAINEX) intensive observation period on 11 September 2005. Results showed that the spinup of the secondary tangential wind maximum during the ERC can be attributed to the efficient convergence of absolute angular momentum by the midlevel inflow of Ophelia’s dominantly stratiform rainbands. This secondary tangential wind maximum strongly contributed to the azimuthal mean tangential wind field, which is conducive for increased low-level supergradient winds and corresponding outflow. The low-level supergradient forcing enhanced convergence to form a secondary eyewall. Ophelia provides a unique example of an ERC occurring in a weaker storm with predominantly stratiform rainbands, suggesting an important role of stratiform precipitation processes in the development of secondary eyewalls.

Restricted access
Youjia Zou and Xiangying Xi

Abstract

It is generally accepted that the El Niño–Southern Oscillation (ENSO) dominates interannual climate variability. Yet, its genesis and maintenance mechanisms are still under intense debate, with no scientific consensus. Some authors argued that the westerly winds originating over the equatorial Indian Ocean are significantly enhanced and extend eastward in the western and central equatorial Pacific during El Niño events, thus advecting the warm pool eastward along the equator and causing SST anomalies. However, this assertion is unlikely to be quantitatively supported by observational data. Here we present detailed observational data and modeling evidence to demonstrate that the westerly winds had little change in intensity in the western equatorial Pacific, with a wider zonal extent only during most El Niño events, and with a slight increase even in the most pronounced 1997 El Niño. Instead, an eastward equatorial current near the equator has been observed and is considered to play a significant role in shifting the eastern edge of the warm pool eastward, elevating SSTs in the central and eastern equatorial Pacific and giving rise to El Niño, with the interactions between the eastward warm pool and the upwelling in the eastern cold tongue ascertaining the amplitudes of SST anomalies.

Restricted access
Hanii Takahashi, Alejandro Bodas-Salcedo, and Graeme Stephens

Abstract

The latest configuration of the Hadley Centre Global Environmental Model, version 3 (HadGEM3), contains significant changes in the formulation of warm rain processes and aerosols. We evaluate the impacts of these changes in the simulation of warm rain formation processes using A-Train observations. We introduce a new model evaluation tool, quartile-based contoured frequency by optical depth diagrams (CFODDs), in order to fill in some blind spots that conventional CFODDs have. Results indicate that HadGEM3 has weak linkage between the size of particle radius and warm rain formation processes, and switching to the new warm rain microphysics scheme causes more difference in warm rain formation processes than switching to the new aerosol scheme through reducing overly produced drizzle mode in HadGEM3. Finally, we run an experiment in which we perturb the second aerosol indirect effect (AIE) to study the rainfall–aerosol interaction in HadGEM3. Since the large changes in the cloud droplet number concentration (CDNC) appear in the AIE experiment, a large impact in warm rain diagnostics is expected. However, regions with large fractional changes in CDNC show a muted change in precipitation, arguably because large-scale constraints act to reduce the impact of such a big change in CDNC. The adjustment in cloud liquid water path to the AIE perturbation produces a large negative shortwave forcing in the midlatitudes.

Restricted access
Elizabeth A. Maroon, Stephen G. Yeager, Gokhan Danabasoglu, and Nan Rosenbloom

Abstract

The subpolar North Atlantic (SPNA) experienced extreme cold during 2015, an event often called the “cold blob.” The evolution of this event in the Community Earth System Model version 1 Decadal Prediction Large Ensemble (CESM1-DPLE) hindcast initialized in November 2014 is compared to observations. This CESM1-DPLE hindcast failed to predict cold conditions during 2015 despite already cold SPNA initial conditions and despite having high sea surface temperature skill in the SPNA in all other years. The goal of this paper is to understand what led to this prediction failure in order to provide insight for future decadal prediction efforts. Our analysis shows that strongly positive North Atlantic Oscillation (NAO) conditions during winter and spring 2015 likely sustained the cold blob but were not simulated in any CESM1-DPLE members. We examine the rarity of the 2015 event using the CESM1-DPLE’s uninitialized counterpart, the CESM1 Large Ensemble (CESM1-LE). Results from the CESM1-LE indicate that the exceptional state of the observed NAO in the winter of 2015 is at least part of the explanation for why this event was not encompassed in the CESM1-DPLE spread. To test another possibility—namely, that deficiencies in the initial conditions degraded the prediction—we performed additional hindcasts using the CESM1-DPLE protocol but different initial conditions. Altering the initial conditions did not improve the simulation of the 2015 cold blob, and in some cases, degraded it. Given the difficulty of predicting this event, this case could be a useful test bed for future prediction system development.

Open access
Abdulrahman Khamaj, Amin G. Alhashim, Vincent T. Ybarra, and Azham Hussain

Abstract

Communicating weather forecasts from the public perspective is essential for meeting people’s needs and enhancing their overall experiences. Because of the lack of cited work on the public’s behavior and perception of weather data and delivery sources in Middle Eastern countries such as Saudi Arabia (KSA), this study employs a cross-sectional questionnaire to fill the gap and apply the protective action decision model to non-Western individuals. The questionnaire examined respondents’ opinions about 1) the importance of weather forecast accessibility, 2) crucial weather features, and 3) available features on existing smartphone weather applications (apps) in KSA. The results showed that nearly all participants reported that their decisions of daily lives and activities were highly dependent on weather forecasts. Most participants thought weather forecast features are necessary. Although the most commonly used source for weather forecasts in KSA was smartphone apps, many participants responded that these apps were lacking specific weather functionalities (e.g., giving weather alerts to their exact location). Regression analyses found that KSA individuals who do not believe that weather forecasts are important are predicted by 1) not wanting any new features added to weather applications and 2) thinking that weather forecasts do not impact lives or property. This study’s findings can guide governmental and private weather agencies in KSA and other Middle Eastern or developing countries to better understand how to meet and communicate people’s weather needs.

Restricted access
W. D. Smyth, S. J. Warner, J. N. Moum, H. T. Pham, and S. Sarkar

Abstract

Factors thought to influence deep cycle turbulence in the equatorial Pacific are examined statistically for their predictive capacity using a 13-yr moored record that includes microstructure measurements of the turbulent kinetic energy dissipation rate. Wind stress and mean current shear are found to be most predictive of the dissipation rate. Those variables, together with the solar buoyancy flux and the diurnal mixed layer thickness, are combined to make a pair of useful parameterizations. The uncertainty in these predictions is typically 50% greater than the uncertainty in present-day in situ measurements. To illustrate the use of these parameterizations, the record of deep cycle turbulence, measured directly since 2005, is extended back to 1990 based on historical mooring data. The extended record is used to refine our understanding of the seasonal variation of deep cycle turbulence.

Open access