scholarly journals What Drives the North Atlantic Oscillation’s Temperature Anomaly Pattern? Part I: The Growth and Decay of the Surface Air Temperature Anomalies

2019 ◽  
Vol 77 (1) ◽  
pp. 185-198 ◽  
Author(s):  
Joseph P. Clark ◽  
Steven B. Feldstein
Keyword(s):  
Skin Temperature ◽  
Air Temperature ◽  
Temperature Anomaly ◽  
Surface Air Temperature ◽  
Temperature Changes ◽  
Temperature Anomalies ◽  
The North ◽  
Temperature Advection ◽  
Anomaly Pattern ◽  
Air Temperature Anomaly

Abstract Composite analysis is used to examine the physical processes that drive the growth and decay of the surface air temperature anomaly pattern associated with the North Atlantic Oscillation (NAO). Using the thermodynamic energy equation that the European Centre for Medium-Range Weather Forecasts implements in their reanalysis model, we show that advection of the climatological temperature field by the anomalous wind drives the surface air temperature anomaly pattern for both NAO phases. Diabatic processes exist in strong opposition to this temperature advection and eventually cause the surface air temperature anomalies to return to their climatological values. Specifically, over Greenland, Europe, and the United States, longwave heating/cooling opposes horizontal temperature advection while over northern Africa vertical mixing opposes horizontal temperature advection. Despite the pronounced spatial correspondence between the skin temperature and surface air temperature anomaly patterns, the physical processes that drive these two temperature anomalies associated with the NAO are found to be distinct. The skin temperature anomaly pattern is driven by downward longwave radiation whereas stated above, the surface air temperature anomaly pattern is driven by horizontal temperature advection. This implies that the surface energy budget, although a useful diagnostic tool for understanding skin temperature changes, should not be used to understand surface air temperature changes.

scholarly journals What Leads to Persisting Surface Air Temperature Anomalies from Winter to Following Spring over Mid- to High-Latitude Eurasia?

2020 ◽  
Vol 33 (14) ◽  
pp. 5861-5883 ◽  
Author(s):  
Renguang Wu ◽  
Shangfeng Chen
Keyword(s):  
Atmospheric Circulation ◽  
Air Temperature ◽  
North Atlantic ◽  
High Latitude ◽  
Surface Air Temperature ◽  
Circulation Anomaly ◽  
The North ◽  
Anomaly Pattern ◽  
The North Atlantic ◽  
Atmospheric Circulation Anomaly

AbstractSurface air temperature (SAT) anomalies tend to persist from winter to the following spring over the mid- to high latitudes of Eurasia. The present study compares two distinct cases of Eurasian SAT anomaly evolution and investigates the reasons for the persistence of continental-scale mid- to high-latitude Eurasian SAT anomalies from winter to following spring (termed persistent cases). The persisting SAT anomalies are closely associated with the sustenance of large-scale atmospheric circulation anomaly pattern over the North Atlantic and Eurasia, featuring a combination of the North Atlantic Oscillation/Arctic Oscillation (NAO/AO) and the Scandinavian pattern, from winter to spring. The combined circulation anomalies result in SAT warming over most of mid- to high-latitude Eurasia via anomalous wind-induced temperature advection. The sustenance of atmospheric circulation anomaly pattern is related to the maintenance of the North Atlantic triple sea surface temperature (SST) anomaly pattern due to air–sea interaction processes. The Barents Sea ice anomalies, which form in winter and increase in spring, also partly contribute to the sustenance of atmospheric circulation anomalies via modulating thermal state of the lower troposphere. In the cases that notable SAT warming (cooling) in winter is replaced by pronounced SAT cooling (warming) in the subsequent spring—termed reverse cases—the North Atlantic SST anomalies become small and the Greenland Sea ice change is a response to atmospheric change in spring. Without the support of lower boundary forcing, the atmospheric circulation anomaly pattern experiences a reverse in the spatial distribution from winter to spring likely due to internal atmospheric processes.

scholarly journals Spatio–Temporal Characterization of Land Surface Air Temperature Anomaly over Nigeria

2019 ◽  
pp. 1-9
Author(s):  
O. O. Ajileye ◽  
S. S. Aladodo ◽  
A. B. Rabiu
Keyword(s):  
Air Temperature ◽  
Land Surface ◽  
Temperature Anomaly ◽  
Surface Air Temperature ◽  
Temporal Variations ◽  
Capital City ◽  
Percentage Increase ◽  
Air Temperatures ◽  
Spatio Temporal ◽  
Air Temperature Anomaly

In this study, seventeen gridded stations across the latitude over Nigeria were selected with a view to determine and characterize land surface air temperature anomaly for both minimum and maximum values. The study intends to present graphic illustrations of spatial and temporal variations of land surface air temperature anomaly within a period 2008 – 2013. Long-term averages of minimum and maximum land surface air temperatures were obtained from National Aeronautic and Space Administration satellite meteorological dataset (1983 – 2007). Also, monthly and annual averages of land surface air temperatures were obtained from tutiempo.net to compute monthly anomaly, annual anomaly and percentage departure of minimum and maximum land surface air temperatures within a period of 2008 – 2013. The results showed that Jos had consistently experienced -10.8 and -4 percent decrease in minimum and maximum LSAT anomaly for the period under review. The implication is that Jos is getting colder than usual. The minimum LSAT anomaly declined by -2.8 percent in Lagos. Other stations across Nigeria showed a considerable percentage increase in minimum LSAT anomaly led by Yola (19.5%), Sokoto (18%) and Katsina (15.5%). Inland stations had percentage increase of minimum LSAT anomaly ranging between 5.8% and 10% except in Osogbo where the percentage increase was 1.8%. Osogbo is a less populated capital city of Osun state with active agricultural activities as heat sink. Percentage increase of minimum LSAT anomaly was not significant in Nigerian coastal areas most especially at Port Harcourt (0.5%). The spatial distribution of maximum LSAT anomaly across Nigerian latitudinal belt, unlike minimum LSAT anomaly, reduced in trend except in Lagos, Makurdi, Abuja, Bida, Minna and Kano. The minimum and maximum anomaly for maximum LSAT was observed at Jos and Makurdi respectively. There are 2 stations to be watched in terms of getting colder in the years to ahead namely Jos and Osogbo while Makurdi and Yola are gradually becoming hotspots.

Intensified impacts of central Pacific ENSO on the reversal of December and January surface air temperature anomaly over China since 1997

2020 ◽  
pp. 1-49
Author(s):  
Hua Li ◽  
Ke Fan ◽  
Shengping He ◽  
Yong Liu ◽  
Xing Yuan ◽  
...  
Keyword(s):  
Air Temperature ◽  
Southern Oscillation ◽  
Function Analysis ◽  
Surface Air Temperature ◽  
Walker Circulation ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Siberian High ◽  
Temperature Anomalies ◽  
Air Temperature Anomaly

AbstractThe reversal of surface air temperature anomalies (SATA) in winter brings a great challenge for short-term climate prediction and the mechanisms are not well understood. This study found that the reversal of SATA between December and January over China could be demonstrated by the second leading mode of multivariate empirical orthogonal function analysis on the December-January SATA. It further reveals that the central Pacific El Niño-Southern Oscillation (CP ENSO) has contributed more influences on such a reversal of SATA since 1997. CP ENSO shows positive but weak correlations with SATA over China in both December and January during pre-1996, whereas it shows significantly negative and positive correlations with the SATA in December and January, respectively, during post-1997. The CP ENSO-related circulations suggest that the change of the Siberian high plays an essential role in the reversal of SATA since 1997. Sea surface temperature anomalies pattern associated with the CP ENSO leads to a westward-replaced Walker circulation which alters the local meridional circulation and further impacts the Siberian high and SATA over China since 1997. Moreover, the seasonal northward-march of convergence zone from December to January causes northward-replaced west branch of the Walker circulation in January compared with that in December. The west branch of Walker circulation in December and January directly modulates local Hadley and Ferrel circulations, and then causes contrasting Siberian high anomalies through inducing opposite vertical motions anomalies over Siberia. The reversal of SATA between December and January is therefore more frequently observed over China since 1997. The above-mentioned mechanisms are validated by the analysis at pentad time scale and confirmed by numerical simulations.

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