ALBERT

Description: Numerous studies have concluded that historical Hadley cell expansion simulated in reanalyses is much larger than the future expansion predicted by climate model simulations. Is Hadley cell expansion too weak in climate models, or are the trends in reanalyses spuriously large? This study shows that the mean meridional circulation in reanalyses generally does not conserve mass. The mass imbalance projects onto trends in the Hadley cell edge latitudes by modifying both the mean and anomalous circulation. In correcting for the imbalance, the majority of Hadley cell expansion trends in early-generation reanalyses in both hemispheres are revised to be smaller in magnitude, bringing them into closer agreement with the trends in modern reanalyses and climate models. While the methodology presented here is statistical in nature, it produces quantitatively similar results to a more sophisticated mass budget correction method. ©2018. American Geophysical Union. All Rights Reserved.

Description: The width of the tropical Hadley circulation (HC) has garnered intense interest in recent decades, owing to the emerging evidence for its expansion in observations and models and to the anticipated impacts on surface climate in its descending branches. To better clarify the causes and impacts of tropical widening, this work generalizes the zonal mean HC to the regional level by defining meridional overturning cells (RC) using the horizontally divergent wind. The edges of the RC are more closely connected to surface hydroclimate than more traditional metrics of regional tropical width (such as the sea level pressure ridge) or even than the zonal mean HC. Simulations reveal a robust weakening of the RC in response to greenhouse gas increases, along with a widening of the RC in some regions. For example, simulated widening of the zonal mean HC in the Southern Hemisphere appears to arise in large part from regional overturning anomalies over the Eastern Pacific, where there is no clear RC. Unforced interannual variability in the position of the zonal mean HC edge is associated with a more general regional widening. These distinct regional signatures suggest that the RCs may be well suited for the attribution of observed circulation trends. The spatial pattern of regional meridional overturning trends in reanalyses corresponds more closely to the pattern associated with unforced interannual variability than to the pattern associated with CO2 forcing, suggesting a large contribution of natural variability to the recent observed tropical widening trends. © 2019. American Geophysical Union. All Rights Reserved.

Description: Haiti has suffered great losses from deforestation, with little forest cover remaining today. Current reforestation efforts focus on seedling quantity rather than quality. This study examined limitations to the production of high-quality seedlings of the endemic Hispaniolan pine (Pinus occidentalis Swartz). Recognizing the importance of applying sustainable development principles to pine forest restoration, the effects of growing media and container types on seedling growth were evaluated with the goal of developing a propagation protocol to produce high-quality seedlings using economically feasible nursery practices. With regard to growing media, seedlings grew best in compost-based media amended with sand. Topsoil, widely used in nurseries throughout Haiti, produced the smallest seedlings overall. Despite a low water holding capacity and limited manganese, compost-based media provided adequate levels of essential mineral nutrients (particularly nitrogen), which allowed for sufficient seedling nutrition. Seedling shoot and root growth, as well as the ratio of shoot biomass to root biomass, were greater in polybags relative to D40s. Results indicate that economically feasible improvements to existing nursery practices in Haiti can improve the early growth rates of P. occidentalis seedlings.

Description: The Antarctic Centennial Oscillation (ACO) is a paleoclimate temperature cycle that originates in the Southern Hemisphere, is the presumptive evolutionary precursor of the contemporary Antarctic Oscillation (AAO), and teleconnects to the Northern Hemisphere to influence global temperature. In this study we investigate the internal climate dynamics of the ACO over the last 21 millennia using stable water isotopes frozen in ice cores from 11 Antarctic drill sites as temperature proxies. Spectral and time series analyses reveal that ACOs occurred at all 11 sites over all time periods evaluated, suggesting that the ACO encompasses all of Antarctica. From the Last Glacial Maximum through the Last Glacial Termination (LGT), ACO cycles propagated on a multicentennial time scale from the East Antarctic coastline clockwise around Antarctica in the streamline of the Antarctic Circumpolar Current (ACC). The velocity of teleconnection (VT) is correlated with the geophysical characteristics of drill sites, including distance from the ocean and temperature. During the LGT, the VT to coastal sites doubled while the VT to inland sites decreased fourfold, correlated with increasing solar insolation at 65°N. These results implicate two interdependent mechanisms of teleconnection, oceanic and atmospheric, and suggest possible physical mechanisms for each. During the warmer Holocene, ACOs arrived synchronously at all drill sites examined, suggesting that the VT increased with temperature. Backward extrapolation of ACO propagation direction and velocity places its estimated geographic origin in the Southern Ocean east of Antarctica, in the region of the strongest sustained surface wind stress over any body of ocean water on Earth. ACO period is correlated with all major cycle parameters except cycle symmetry, consistent with a forced, undamped oscillation in which the driving energy affects all major cycle metrics. Cycle period and symmetry are not discernibly different for the ACO and AAO over the same time periods, suggesting that they are the same climate cycle. We postulate that the ACO/AAO is generated by relaxation oscillation of Westerly Wind velocity forced by the equator-to-pole temperature gradient and propagated regionally by identified air-sea-ice interactions.

Description: Circadian rhythms allow an organism to synchronize internal physiological responses to the external environment. Perception of external signals such as light and temperature are critical in the entrainment of the oscillator. However, sugar can also act as an entraining signal. In this work, we have confirmed that sucrose accelerates the circadian period, but this observed effect is dependent on the reporter gene used. This observed response was dependent on sucrose being available during free-running conditions. If sucrose was applied during entrainment, the circadian period was only temporally accelerated, if any effect was observed at all. We also found that sucrose acts to stabilize the robustness of the circadian period under red light or blue light, in addition to its previously described role in stabilizing the robustness of rhythms in the dark. Finally, we also found that CCA1 is required for both a short- and long-term response of the circadian oscillator to sucrose, while LHY acts to attenuate the effects of sucrose on circadian period. Together, this work highlights new pathways for how sucrose could be signaling to the oscillator and reveals further functional separation of CCA1 and LHY.

Description: Subirrigation (SI), where water is provided to container seedlings from below and rises through the growing media via capillary action, is regarded as an environmentally-responsible method of delivering water and fertilizer to nursery-grown plants, resulting in more uniform crops and improved production efficiency. While a concern around adopting this method is that a potential higher salt concentration in the upper layers of growing media under SI may inhibit root growth and result in decreased plant quality, few studies have focused on how root morphology is altered by SI. Therefore, a balanced two-factor factorial design with three rates of fertilization (50, 100, and 150 mg N seedling−1) and two irrigation methods (SI or overhead irrigation (OI)) was used to examine the growth response of Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr) seedlings for one nursery season. Associated changes between rhizosphere electrical conductivity (EC) and root morphology of different root size classes were analyzed. Results show that (1) height, root-collar diameter, and root volume were similar between seedlings grown under SI and OI. However, (2) compared to seedlings receiving OI, SI-seedlings had less root mass, length, and surface area but greater average root diameter (ARD). (3) Morphological differences were evident primarily in root diameter size classes I–III (D ≤ 1.0 mm). (4) Fertilizer rate influenced root length and surface area up to 130 days after sowing but affected ARD throughout the growing season such that seedlings treated with 50 mg N had smaller ARD than seedlings treated with 100 mg N. (5) As the growing season progressed, SI-media had significantly higher EC compared to OI-media and EC increased with increasing fertilizer rate under SI but not under OI. These results indicate that SI can produce larch seedlings of similar height and root collar diameter (RCD) compared to OI, but root systems are smaller overall with fewer small-diameter roots, which may be related to high EC levels in SI-media, which is exacerbated by the use of high rates of fertilizer. Therefore, the EC in the media should be monitored and adjusted by reducing fertilizer rates under SI.

Description: Jules Verne’s adventure novels Five Weeks in a Balloon and Around the World in 80 Days highlighted some of the great technological advances of the late 19th century that revolutionized travel and captured the imagination of the public [ Verne, 1863, 1873]. Among those inspired by the novels was Nellie Bly, an American journalist for the New York World , who set off in November 1889 to complete a journey by rail and steamship, following Verne’s imagined path around the world in a record 72 days [ Bly, 1890] (Figure 1). Fig. 1. In 1889–1890, real-life New York World reporter Nellie Bly completed Jules Verne’s imagined path (shown here) around the world in slightly less than Verne’s “80 days.” Neither Bly’s journey nor Verne’s Around the World in 80 Days actually involved balloon travel, but Verne’s book drew on his previous novel Five Weeks in a Balloon. The earlier novel inspired the idea of incorporating balloon travel for one leg of the trip in the 1956 movie Around the World in 80 Days that has become a beloved misconception about Verne’s later book. Credit: Roke/Wikimedia Commons CC BY-SA 3.0 Bly’s accounts demonstrated how new technology, such as the transcountry railroads in the United States and India and the Suez Canal, brought exotic destinations within reach. The revolutionary development of submarine cables and the electric telegraph allowed Bly to keep her editors, and the larger connected world, aware of her progress in near-real time. The France-U.S. collaborative Stratéole 2 project is planning its own series of balloon trips, which will circle the world near the equator for 80 days (more or less), as did these fictional and factual 19th century adventurers, demonstrating new technology and sending new observations from the voyage back via satellite. Drifting with the Winds Scientists with the Stratéole 2 project will release superpressure balloons, designed to drift in the lower stratosphere, from the Seychelles islands in the Indian Ocean (Figure 2). Superpressure balloons contain a fixed amount of helium sealed inside an envelope that does not stretch. This type of balloon is not fully inflated when it is launched, but it expands to its full volume as it rises to an altitude where the gas density inside the balloon matches the density of the surrounding air and where it drifts with the wind. Fig. 2. Early test flights of the French National Center for Space Studies superpressure balloon system during February–May 2010 followed a tropical route. The flight durations of the three balloons were 92, 78, and (yes!) 80 days. The traces of the balloon paths show some wave structure, and the balloon paths reversed direction when the quasi-biennial oscillation, a periodic east–west oscillating feature in tropical lower stratospheric winds, changed phase. Credit: A. Hertzog Each balloon will carry as many as four instruments. As they collect their high-accuracy measurements of meteorological variables, chemical tracers, clouds, and aerosols, their horizontal motions are nearly identical to those of the surrounding air mass. These measurements will advance our knowledge and understanding of cirrus clouds, aerosols, and equatorial waves in the tropical tropopause layer (TTL; the transition region between the troposphere and the stratosphere) and in the lower stratosphere. Shown here is a fully inflated superpressure balloon in the lab at the French National Center for Space Studies (CNES). Credit: Philippe Cocquerez, CNES The Stratéole 2 research program will begin with a five-balloon technology validation campaign in Northern Hemisphere (boreal) fall–winter 2018–2019, followed by 20 balloon flights in boreal fall–winter 2020–2021. In the second campaign, 10 balloons will fly at an altitude near 20 kilometers, just above the TTL, and another 10 will fly near 18 kilometers, within the TTL. From past experience, we expect each balloon to fly for more than 2 months. Typically, a balloon will fly for about 84 days before chaotic atmospheric motions or interactions with Rossby waves push it outside of the deep tropics. A final 20-balloon campaign in 2023–2024 will drift in the opposite direction because of the shifting phase of the quasi-biennial oscillation (QBO), a dominant, periodic east–west oscillating feature in tropical lower stratospheric winds. Challenges Aloft The Stratéole 2 campaign targets the TTL, the primary entry point for tropospheric air into the stratosphere. As air slowly ascends across the TTL, the coldest temperatures encountered at the cold point tropopause (CPT) freeze water vapor into ice crystals. The formation of ice crystals dehydrates the air and regulates the amount of humidity reaching the global stratosphere, giving the TTL an outsized importance considering its geographic extent. The ice crystals form thin cirrus clouds, which have a global impact on the balance between incoming solar radiation and radiation reflected back into space at tropical latitudes. Water vapor and cirrus feedbacks are extremely important in climate system models. The underlying processes that control the formation and sublimation (direct conversion of ice crystals to water vapor) of these clouds remain strongly debated. These processes involve the interplay of deep convection, microphysics, aerosols, wave-induced temperature variations with timescales ranging from minutes to weeks, and the balance of forces driving large-scale slow ascent of air in the tropics. The superposition of wave-induced fluctuations on the average upwelling motion forces the temperatures in the TTL to extreme values at the CPT—less than –94°C at times and well below those expected from radiative equilibrium. These same waves also drive the QBO, which has an important long-range indirect influence on high-latitude seasonal forecasts. The waves, generated by convection below, transport momentum vertically across the TTL and drive QBO wind variations as the momentum dissipates in the stratosphere. Satellite and in situ observations can track the wind reversals of the QBO, but most general circulation models cannot replicate the QBO using current methods. This shortcoming is due to a combination of inadequate spatial resolution and a lack of small-scale wave drag applied at the subgrid scale. Even when models do simulate the QBO, doubts remain on the contribution from various families of waves with different scales and frequencies. As a result, even models that internally generate a QBO were unable to forecast the anomalous disruption of the oscillation that occurred in February 2016 [ Osprey et al., 2016]. Science Objectives This superpressure balloon, shown here at launch, is not fully inflated. As it rises, the volume of helium sealed inside increases until the spherical balloon is fully inflated, giving the balloon a fixed density. Once the balloon has reached the atmospheric level where the air has the same density, it drifts with the wind, providing accurate wind measurements. Credit: Philippe Cocquerez, CNES The overarching objectives of Stratéole 2 are to explore processes that control the transfer of trace gases and momentum between the equatorial upper troposphere and lower stratosphere. The instruments will provide fine-scale measurements of water vapor, temperature, and aerosol/ice at the balloon gondola and also within several kilometers below flight level, documenting air composition and investigating the formation of cirrus in the upper TTL. The balloons also provide unique measurements of equatorial waves over the full spectrum from high-frequency buoyancy waves to planetary-scale equatorial waves, providing information needed to improve representation of these waves in climate models. Stratéole 2 balloons will sample the whole equatorial band from 20°S to 15°N, thus complementing the widespread (but limited-resolution) spaceborne observations and the high-resolution (but geographically restricted) airborne and ground-based measurements from previous field missions. Past balloon campaign measurements sampling the Antarctic stratospheric vortex [see Podglajen et al., 2016] have been used to make accurate estimates of wave momentum fluxes as well as to explain springtime stratospheric ozone loss rates; we expect similar successes with our current campaigns. Stratéole 2 balloon flights will collect measurements over oceanic areas that are otherwise devoid of any stratospheric wind measurements.Other Stratéole 2 science objectives include contributions to operational meteorology and satellite validation. Wind analyses and forecasts have notably large errors in the tropics because sparse tropical wind measurements cannot be modeled in a straightforward way through their dynamical relation to temperature, as they are at higher latitudes. Thus, reducing these errors requires a higher density of measurements. Stratéole 2 balloon flights will address this data shortage by providing unprecedented, accurate wind observations in the equatorial regions of the upper troposphere and lower stratosphere. In particular, the project will collect measurements over oceanic areas that are otherwise devoid of any stratospheric wind measurements. The data will also contribute to the validation of Atmospheric Dynamics Mission Aeolus (ADM-Aeolus) wind products. An innovative European Space Agency mission, ADM-Aeolus, due to be launched in September 2018, is designed to perform the first spaceborne wind lidar measurements, providing unprecedented global coverage. The ensemble of Stratéole 2 instrumentation includes in situ measurements of pressure, temperature, and winds every 30 seconds and less frequently sampled observations of ozone, aerosols, water vapor, and carbon dioxide, plus remotely sensed cloud structure from microlidar and directional radiative fluxes. Instruments providing profiles will include GPS radio occultation receivers that measure temperature profiles to the side of the balloons. Novel reel-down devices suspended as far as 2 kilometers directly below the balloons will also provide profiles to explore the fine-scale distribution of temperature, aerosol/ice, and humidity. Capturing temperature variations in high-resolution profiles, in particular, from the unique balloon platform, is an approach that will provide new insight into equatorial wave processes. Measuring ozone in combination with water vapor and carbon dioxide enables us to discover correlations among these tracers that describe transport processes at the top of the TTL, including convective overshoots that rapidly transport air from the surface into the TTL. Data Dissemination Within 12 months of the end of each balloon campaign, the Stratéole 2 data set will be freely available to the scientific community.The Stratéole 2 data policy is in compliance with World Meteorological Organization (WMO) Resolution 40 (WMO Cg-XII) on the policy and practice for the exchange of meteorological and related data and products. Within 12 months of the end of each balloon campaign, the Stratéole 2 data set will be freely available to the scientific community through the Stratéole 2 Data Archive Center (S2DAC), which is scheduled to launch its website in July 2018. S2DAC will collect and make available the balloon observations and associated ground-based and satellite data, reanalyses, and model outputs. The S2DAC includes a primary, full repository at the Dynamic Meteorology Laboratory (LMD) in France and a secondary mirror site at the Laboratory for Atmospheric and Space Physics (LASP) in Boulder, Colo., in the United States. In addition, during the balloon campaigns, a subset of the Stratéole 2 data set, specifically flight-level winds, will be disseminated on the Global Telecommunication System for their assimilation in numerical weather prediction systems. We invite and encourage the use of Stratéole 2 data by the broader scientific community, and potential users can watch for future campaign updates on the project website. Up, Up, and Away In the spirit of Verne’s imagined use of new technologies and Bly’s real-world application of those technologies to explore the world, the Stratéole 2 campaign will scientifically explore the tropical tropopause and lower stratosphere from a long-duration superpressure balloon platform. The use of multiple balloons will permit extensive exploration of the finely layered features and unique processes occurring in this remote part of the atmosphere. With the involvement of the broader scientific community, analyses of the Stratéole 2 measurements hold promise to provide a new and deeper understanding of these processes and the connections of this region to global chemistry, dynamics, and climate variability. Acknowledgments Major funding for the Stratéole 2 campaign is provided by France’s National Center for Space Studies (CNES) and National Center for Scientific Research (CNRS), as well as the U.S. National Science Foundation (NSF).

Description: Climate observations are needed to address a large range of important societal issues including sea level rise, droughts, floods, extreme heat events, food security, and fresh water availability in the coming decades. Past, targeted investments in specific climate questions have resulted in tremendous improvements in issues important to human health, security, and infrastructure. However, the current climate observing system was not planned in a comprehensive, focused manner required to adequately address the full range of climate needs. A potential approach to planning the observing system of the future is presented in this paper. First, this paper proposes that priority be given to the most critical needs as identified within the World Climate Research Program as Grand Challenges. These currently include seven important topics: Melting Ice and Global Consequences; Clouds, Circulation and Climate Sensitivity; Carbon Feedbacks in the Climate System; Understanding and Predicting Weather and Climate Extremes; Water for the Food Baskets of the World; Regional Sea-Level Change and Coastal Impacts; and Near-term Climate Prediction. For each Grand Challenge, observations are needed for long-term monitoring, process studies and forecasting capabilities. Second, objective evaluations of proposed observing systems, including satellites, ground-based and in situ observations as well as potentially new, unidentified observational approaches, can quantify the ability to address these climate priorities. And third, investments in effective climate observations will be economically important as they will offer a magnified return on investment that justifies a far greater development of observations to serve society's needs.