scholarly journals Thermodynamic Phase and Ice Cloud Properties in Northern Hemisphere Winter Extratropical Cyclones Observed by Aqua AIRS

2015 ◽  
Vol 54 (11) ◽  
pp. 2283-2303 ◽  
Author(s):  
Catherine M. Naud ◽  
Brian H. Kahn
Keyword(s):  
Northern Hemisphere ◽  
Cloud Cover ◽  
Frontal Region ◽  
Extratropical Cyclones ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Cloud Properties ◽  
Hemisphere Winter ◽  
Thermodynamic Phase ◽  
Northern Hemisphere Winter

AbstractIce cloud properties in Northern Hemisphere winter extratropical cyclones are examined using the Atmospheric Infrared Sounder (AIRS), version 6, cloud products. The cloud thermodynamic phase product indicates that warm frontal clouds are dominated by ice, liquid-phase clouds occur outside of the warm frontal region, and supercooled or mixed-phase clouds are found in the southwestern quadrant of the cyclones. Stratiform ice clouds populate the warm frontal region and portions of the cold sector while convective ice clouds populate southeastern portions of the warm front and the southeastern quadrant. Total cloud cover is smaller in land cyclones than in ocean cyclones, especially in the southwestern quadrant and the warm frontal region. Ice cloud cover is less over land in the warm frontal region, because land cyclones are generally weaker and drier than ocean cyclones. The impact of cyclone average precipitable water (PW) and the magnitude of 850-hPa vertical ascent ω850 on the thermodynamic phase, occurrence of stratiform or convective ice cloud, ice particle effective diameter, optical thickness, and cloud-top temperature are discussed. When comparing land and ocean cyclones with similar PW and ω850, ice cloud coverage is found to be greater over land. Convective ice cloud occurs more often and is deeper over land. Supercooled cloud appears to persist to colder temperatures over ocean than over land, especially in the warm frontal region. These results suggest that, over land, ice cloud formation in warm fronts is possibly more efficient because of a greater aerosol amount from local or regional sources.

scholarly journals The Role of Warm Conveyor Belts for the Intensification of Extratropical Cyclones in Northern Hemisphere Winter

2016 ◽  
Vol 73 (10) ◽  
pp. 3997-4020 ◽  
Author(s):  
Hanin Binder ◽  
Maxi Boettcher ◽  
Hanna Joos ◽  
Heini Wernli
Keyword(s):  
Northern Hemisphere ◽  
Extratropical Cyclones ◽  
Cyclone Center ◽  
Explosive Cyclones ◽  
Conveyor Belts ◽  
Upper Level ◽  
Hemisphere Winter ◽  
Warm Conveyor Belts ◽  
Northern Hemisphere Winter

Abstract The role of warm conveyor belts (WCBs) and their associated positive low-level potential vorticity (PV) anomalies are investigated for extratropical cyclones in Northern Hemisphere winter, using ERA-Interim and composite techniques. The Spearman correlation coefficient of 0.68 implies a moderate to strong correlation between cyclone intensification and WCB strength. Hereby, cyclone intensification is quantified by the normalized maximum 24-h central sea level pressure deepening and WCB strength by the WCB air mass associated with the cyclone’s 24-h period of strongest deepening. Explosively intensifying cyclones typically have strong WCBs and pronounced WCB-related PV production in the cyclone center; they are associated with a WCB of type W2, which ascends close to the cyclone center. Cyclones with similar WCB strength but weak intensification are either diabatic Rossby waves, which do not interact with an upper-level disturbance, or cyclones where much of the WCB-related PV production occurs far from the cyclone center and thereby does not contribute strongly to cyclone deepening (WCB of type W1, which ascends mainly along the cold front). The category of explosively intensifying cyclones with weak WCBs is inhomogeneous but often characterized by a very low tropopause or latent heating independent of WCBs. These findings reveal that (i) diabatic PV production in WCBs is essential for the intensification of many explosive cyclones, (ii) the importance of WCBs for cyclone development strongly depends on the location of the PV production relative to the cyclone center, and (iii) a minority of explosive cyclones is not associated with WCBs.

scholarly journals Predictability Changes of Stratospheric Circulations in Northern Hemisphere Winter

2016 ◽  
Vol 94 (1) ◽  
pp. 7-24 ◽  
Author(s):  
Tomoko ICHIMARU ◽  
Shunsuke NOGUCHI ◽  
Toshihiko HIROOKA ◽  
Hitoshi MUKOUGAWA
Keyword(s):  
Northern Hemisphere ◽  
Hemisphere Winter ◽  
Northern Hemisphere Winter

scholarly journals Polar stratospheric cloud observations by MIPAS on ENVISAT: detection method, validation and analysis of the northern hemisphere winter 2002/2003

2005 ◽  
Vol 5 (3) ◽  
pp. 679-692 ◽  
Author(s):  
R. Spang ◽  
J. J. Remedios ◽  
L. J. Kramer ◽  
L. R. Poole ◽  
M. D. Fromm ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Detection Method ◽  
Michelson Interferometer ◽  
The Arctic ◽  
Spectral Signature ◽  
Winter Period ◽  
Second Phase ◽  
Good Correspondence ◽  
Hemisphere Winter ◽  
Northern Hemisphere Winter

Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on ENVISAT has made extensive measurements of polar stratospheric clouds (PSCs) in the northern hemisphere winter 2002/2003. A PSC detection method based on a ratio of radiances (the cloud index) has been implemented for MIPAS and is validated in this study with respect to ground-based lidar and space borne occultation measurements. A very good correspondence in PSC sighting and cloud altitude between MIPAS detections and those of other instruments is found for cloud index values of less than four. Comparisons with data from the Stratospheric Aerosol and Gas Experiment (SAGE) III are used to further show that the sensitivity of the MIPAS detection method for this threshold value of cloud index is approximately equivalent to an extinction limit of 10-3km-1 at 1022nm, a wavelength used by solar occultation experiments. The MIPAS cloud index data are subsequently used to examine, for the first time with any technique, the evolution of PSCs throughout the Arctic polar vortex up to a latitude close to 90° north on a near-daily basis. We find that the winter of 2002/2003 is characterised by three phases of very different PSC activity. First, an unusual, extremely cold phase in the first three weeks of December resulted in high PSC occurrence rates. This was followed by a second phase of only moderate PSC activity from 5-13 January, separated from the first phase by a minor warming event. Finally there was a third phase from February to the end of March where only sporadic and mostly weak PSC events took place. The composition of PSCs during the winter period has also been examined, exploiting in particular an infra-red spectral signature which is probably characteristic of NAT. The MIPAS observations show the presence of these particles on a number of occasions in December but very rarely in January. The PSC type differentiation from MIPAS indicates that future comparisons of PSC observations with microphysical and denitrification models might be revealing about aspects of solid particle existence and location.

scholarly journals Evaluating Impacts of Recent Arctic Sea Ice Loss on the Northern Hemisphere Winter Climate Change

2018 ◽  
Vol 45 (7) ◽  
pp. 3255-3263 ◽  
Author(s):  
Fumiaki Ogawa ◽  
Noel Keenlyside ◽  
Yongqi Gao ◽  
Torben Koenigk ◽  
Shuting Yang ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Ice ◽  
Northern Hemisphere ◽  
Arctic Sea Ice ◽  
Winter Climate ◽  
Winter Climate Change ◽  
Arctic Sea ◽  
Hemisphere Winter ◽  
Arctic Sea Ice Loss ◽  
Northern Hemisphere Winter
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