Search results for "latitude"

Frequent Ultrafine Particle Formation and Growth in the Canadian Arctic Marine Environment

2017

Abstract. The source strength and capability of aerosol particles in the Arctic to act as cloud condensation nuclei have important implications for understanding the indirect aerosol-cloud effect within the polar climate system. It has been shown in several Arctic regions that ultrafine particle (UFP) formation and growth is a key contributor to aerosol number concentrations during the summer. This study uses aerosol number size distribution measurements from ship-board measurement expeditions aboard the research icebreaker CCGS Amundsen in the summers of 2014 and 2016 throughout the Canadian Arctic to gain a deeper understanding of the drivers of UFP formation and growth within this marine…

2020

Abstract. The new PAGES2k global compilation of temperature-sensitive proxies offers an unprecedented opportunity to study regional to global trends associated with orbitally driven changes in solar irradiance over the past 2 millennia. Here, we analyze pre-industrial long-term trends from 1 to 1800 CE across the PAGES2k dataset and find that, in contrast to the gradual cooling apparent in ice core, marine, and lake sediment data, tree rings do not exhibit the same decline. To understand why tree-ring proxies lack any evidence of a significant pre-industrial cooling, we divide those data by location (high Northern Hemisphere latitudes vs. midlatitudes), seasonal response (annual vs. summer)…

Arctic aerosols and the ‘Divergence Problem’ in dendroclimatology

2021

Considering the importance and complexity of natural (e.g., volcanic eruptions and wildfires) and anthropogenic (e.g., mining, oil and shipping industries) aerosol emissions to Arctic warming is particularly timely given the recent temperature extremes recorded at high-northern latitudes (Cohen et al., 2020; Overland and Wang, 2021). Despite our knowledge about the observed and modelled climatic effects of rising Arctic aerosol concentrations (Schmale et al., 2021), which may exhibit regional and seasonal differences and call for diverse research priorities from local to circumpolar scales, we feel that the ecological consequences of an aerosol-induced reduction in surface irradiance (i.e.,…

Kilpailu vaikuttaa nieriän ravintoon

2013

Lapin nieriäkannat ovat monin paikoin taantuneet uusien kalalajien levittäytymisen seurauksena. Tuore väitöskirjatutkimus osoittaa, että nieriä voi vaihtaa ravintoaan ja elinpaikkaansa vähentääkseen kilpailua muiden kalalajien kanssa. nonPeerReviewed

Measurements of aerosol and CCN properties in the Mackenzie River delta (Canadian Arctic) during spring–summer transition in May 2014

2018

Within the framework of the RACEPAC (Radiation–Aerosol–Cloud Experiment in the Arctic Circle) project, the Arctic aerosol, arriving at a ground-based station in Tuktoyaktuk (Mackenzie River delta area, Canada), was characterized during a period of 3 weeks in May 2014. Basic meteorological parameters and particle number size distributions (PNSDs) were observed and two distinct types of air masses were found. One type were typical Arctic haze air masses, termed accumulation-type air masses, characterized by a monomodal PNSD with a pronounced accumulation mode at sizes above 100 nm. These air masses were observed during a period when back trajectories indicate an air mass origin in the north-e…

2020

Abstract. The vertical distribution and seasonal variation of water vapour volume mixing ratio (H2O VMR), of relative humidity with respect to ice (RHice) and particularly of regions with ice-supersaturated air masses (ISSRs) in the extratropical upper troposphere and lowermost stratosphere are investigated at northern mid-latitudes over the eastern North American, North Atlantic and European regions for the period 1995 to 2010. Observation data originate from regular and continuous long-term measurements on board instrumented passenger aircraft in the framework of the European research programme MOZAIC (1994–2010), which continues as the European research infrastructure IAGOS (from 2011). …

Characterization of transport regimes and the polar dome during Arctic spring and summer using in situ aircraft measurements

2019

The springtime composition of the Arctic lower troposphere is to a large extent controlled by the transport of midlatitude air masses into the Arctic. In contrast, precipitation and natural sources play the most important role during summer. Within the Arctic region sloping isentropes create a barrier to horizontal transport, known as the polar dome. The polar dome varies in space and time and exhibits a strong influence on the transport of air masses from midlatitudes, enhancing transport during winter and inhibiting transport during summer. We analyzed aircraft-based trace gas measurements in the Arctic from two NETCARE airborne field campaigns (July 2014 and April 2015) with the Alfred W…

The Effects of Orography on the Extratropical Transition of Tropical Cyclones: A Case Study of Typhoon Sinlaku (2008)

2018

Abstract Extratropical transition (ET) can cause high-impact weather in midlatitude regions and therefore constitutes an ongoing threat at the end of a tropical cyclone’s (TC) life cycle. Most of the ET events occur over the ocean, but some TCs recurve and undergo ET along coastal regions; however, the latter category is less investigated. Typhoon Sinlaku (2008), for example, underwent ET along the southern coast of Japan. It was one of the typhoons that occurred during the T-PARC field campaign, providing unprecedented high-resolution observational data. Sinlaku is therefore an excellent case to investigate the impact of a coastal region, and in particular orography, on the evolution of ET…

Relationships between the Antarctic Oscillation, the Madden-Julian Oscillation and ENSO, and consequences for rainfall analysis

2010

Abstract The Antarctic Oscillation (AAO) is the leading mode of atmospheric variability in the Southern Hemisphere mid- and high latitudes (south of 20°S). In this paper, the authors examine its statistical relationships with the major tropical climate signals at the intraseasonal and interannual time scales and their consequences on its potential influence on rainfall variability at regional scales. At the intraseasonal time scale, although the AAO shows its most energetic fluctuations in the 30–60-day range, it is not unambiguously related to the global-scale Madden–Julian oscillation (MJO) activity, with in particular no coherent phase relationship with the MJO index. Moreover, in the hi…

Rossby Wave Packets on the Midlatitude Waveguide-A Review

2018

Abstract Rossby wave packets (RWPs) are Rossby waves for which the amplitude has a local maximum and decays to smaller values at larger distances. This review focuses on upper-tropospheric transient RWPs along the midlatitude jet stream. Their central characteristic is the propagation in the zonal direction as well as the transfer of wave energy from one individual trough or ridge to its downstream neighbor, a process called “downstream development.” These RWPs sometimes act as long-range precursors to extreme weather and presumably have an influence on the predictability of midlatitude weather systems. The paper reviews research progress in this area with an emphasis on developments during…