AGW Observer

Observations of anthropogenic global warming

New research – general climate science (August 23, 2016)

Posted by Ari Jokimäki on August 23, 2016

Some of the latest papers on general climate science (i.e. papers that haven’t been included to any other categories) are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.


Reconsidering meteorological seasons in a changing climate (Kutta & Hubbart, 2016)

Abstract: Traditional definitions of seasonality are insufficient to reflect changes associated with a swiftly changing climate. Regional changes in season onset and length using surface based metrics are well documented, but hemispheric assessments using tropospheric metrics has received little attention. The long-term average of six-hourly analyses of temperature on isobaric surfaces, provided by the Twentieth Century Reanalysis Project, is separated here into quartiles to determine climatologic seasonal end dates. Annual season end dates are defined as the date when the 5-day moving average rose above (winter and spring) or fell below (summer and fall) the long term mean. Climatic season end dates fall between meteorological and astronomical season end dates. The length of summer has increased by an average of 13 days and the length of winter has decreased by an average of 20 days, which are more substantial seasonal changes than previous studies. These changes in season length have occurred largely within the past 36 years, corresponding to most aggressive anthropogenic climate change. Results show that the planetary boundary layer is warming at nearly twice the rate of the free troposphere. The spatial distribution of warming suggests that topographically induced weather systems are collocated with maxima or minima in free tropospheric and boundary layer temperature slope. Furthermore, regions of greatest ensemble spread are not collocated with relative maxima or minima in free troposphere or boundary layer temperature slope. This improved assessment of seasonal transitions is useful to climatologists, agricultural land managers, and scientists interested in seasonally driven biology, hydrology and biogeochemical processes.

Mikhail Budyko’s (1920–2001) contributions to Global Climate Science: from heat balances to climate change and global ecology (Oldfield, 2016)

Abstract: Mikhail Ivanovich Budyko (1920–2001) was a Soviet climatologist perhaps best known in the West for his contribution to understandings of climate change. He acted as director of the Main Geophysical Observatory (named after A.I. Voeikov) in Leningrad (St Petersburg) from 1954 and played an active role in advancing Soviet climate agendas within an international context. Three main stages in the development of Budyko’s work related to climate systems and global ecology (late 1940s-mid 1980s) are identified. The first period encompasses his early efforts devoted to understanding and quantifying the interrelationship between the lower atmosphere and the earth’s surface. This stage of his career was also characterized by a growing interest in regional- and global-scale processes, and was underpinned by collaborative work involving climatologists, physical geographers, and other cognate scientists. The second stage highlights the broadening of his global interest in order to engage more deeply with both natural and anthropogenic climatic and environmental change. The third stage reflects on the development of his expansive and evolutionary approach to the biosphere, and his insight into the formative role of climate with respect to the functioning of physical and biological processes. Furthermore, this later work also exhibited a strong belief in the ability of humankind to reflect wisely on its growing influence on the physical environment and respond appropriately.

Wave climate in the Arctic 1992–2014: seasonality and trends (Stopa, Ardhuin & Girard-Ardhuin, 2016)

Abstract: Over the past decade, the diminishing Arctic sea ice has impacted the wave field, which depends on the ice-free ocean and wind. This study characterizes the wave climate in the Arctic spanning 1992–2014 from a merged altimeter data set and a wave hindcast that uses CFSR winds and ice concentrations from satellites as input. The model performs well, verified by the altimeters, and is relatively consistent for climate studies. The wave seasonality and extremes are linked to the ice coverage, wind strength, and wind direction, creating distinct features in the wind seas and swells. The altimeters and model show that the reduction of sea ice coverage causes increasing wave heights instead of the wind. However, trends are convoluted by interannual climate oscillations like the North Atlantic Oscillation (NAO) and Pacific Decadal Oscillation. In the Nordic Greenland Sea the NAO influences the decreasing wind speeds and wave heights. Swells are becoming more prevalent and wind-sea steepness is declining. The satellite data show the sea ice minimum occurs later in fall when the wind speeds increase. This creates more favorable conditions for wave development. Therefore we expect the ice freeze-up in fall to be the most critical season in the Arctic and small changes in ice cover, wind speeds, and wave heights can have large impacts to the evolution of the sea ice throughout the year. It is inconclusive how important wave–ice processes are within the climate system, but selected events suggest the importance of waves within the marginal ice zone.

Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction (Yonehara et al. 2016)

Abstract: Ocean surface winds are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface winds measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of wind that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ~5 km) ocean surface winds. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground speed fluctuated presumably due to tail winds and head winds. Taking advantage of the ground speed difference in relation to flight direction, we reliably estimated wind speed and direction experienced by the birds. These bird-based wind velocities were significantly correlated with wind velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution wind observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface winds, potentially complementing conventional wind measurements by covering spatial and temporal measurement gaps.

The Climate of Titan (Mitchell & Lora, 2016)

Abstract: Over the past decade, the Cassini-Huygens mission to the Saturn system has revolutionized our understanding of Titan and its climate. Veiled in a thick organic haze, Titan’s visible appearance belies an active, seasonal weather cycle operating in the lower atmosphere. Here we review the climate of Titan, as gleaned from observations and models. Titan’s cold surface temperatures (∼90 K) allow methane to form clouds and precipitation analogously to Earth’s hydrologic cycle. Because of Titan’s slow rotation and small size, its atmospheric circulation falls into a regime resembling Earth’s tropics, with weak horizontal temperature gradients. A general overview of how Titan’s atmosphere responds to seasonal forcing is provided by estimating a number of climate-related timescales. Titan lacks a global ocean, but methane is cold-trapped at the poles in large seas, and models indicate that weak baroclinic storms form at the boundary of Titan’s wet and dry regions. Titan’s saturated troposphere is a substantial reservoir of methane, supplied by deep convection from the summer poles. A significant seasonal cycle, first revealed by observations of clouds, causes Titan’s convergence zone to migrate deep into the summer hemispheres, but its connection to polar convection remains undetermined. Models suggest that downwelling of air at the winter pole communicates upper-level radiative cooling, reducing the stability of the middle troposphere and priming the atmosphere for spring and summer storms when sunlight returns to Titan’s lakes. Despite great gains in our understanding of Titan, many challenges remain. The greatest mystery is how Titan is able to retain an abundance of atmospheric methane with only limited surface liquids, while methane is being irreversibly destroyed by photochemistry. A related mystery is how Titan is able to hide all the ethane that is produced in this process. Future studies will need to consider the interactions between Titan’s atmosphere, surface, and subsurface in order to make further progress in understanding Titan’s complex climate system.

Other papers

Identifying anomalously early spring onsets in the CESM large ensemble project (Labe et al. 2016)

Drylands extent and environmental issues. A global approach (Pravalie, 2016)

Was Venus the First Habitable World of our Solar System? (Way et al. 2016)

Royal Navy logbooks as secondary sources and their use in climatic investigations: introducing the log-board (Norrgård, 2016)

Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction (Yonehara et al. 2016)

Climatology of cold season lake-effect cloud bands for the North American Great Lakes (Laird et al. 2016)

Homogenization and assessment of observed near-surface wind speed trends across Sweden, 1956-2013 (Minola, Azorin-Molina & Chen, 2016)

Objective identification of multiple large fire climatologies: an application to a Mediterranean ecosystem (Ruffault et al. 2016)

Extension of summer climatic conditions into spring in the Western Mediterranean area (Jansa et al. 2016)

Homogenized Variability of Radiosonde Derived Atmospheric Boundary Layer Height over the Global Land Surface from 1973 to 2014 (Wang & Wang, 2016)

ICOADS Release 3.0: a major update to the historical marine climate record (Freeman et al. 2016)

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