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- Chen, Deliang, 1961, et al.
(författare)
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Recent Recovery of the Siberian High Intensity
- 2011
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 116
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Tidskriftsartikel (refereegranskat)abstract
- This study highlights the fast recovery of the wintertime Siberian High intensity (SHI) over the last two decades. The SHI showed a marked weakening trend from the 1970s to 1980s, leading to unprecedented low SHI in the early 1990s according to most observational data sets. This salient declining SHI trend, however, was sharply replaced by a fast recovery over the last two decades. Since the declining SHI trend has been considered as one of the plausible consequences of climate warming, the recent SHI recovery seemingly contradicts the continuous progression of climate warming in the Northern Hemisphere. We suggest that alleviated surface warming and decreased atmospheric stability in the central Siberia region, associated with an increase in Eurasian snow cover, in the recent two decades contributed to this rather unexpected SHI recovery. The prominent SHI change, however, is not reproduced by general circulation model (GCM) simulations used in the IPCC AR4. The GCMs indicate the steady weakening of the SHI for the entire 21st century, which is found to be associated with a decreasing Eurasian snow cover in the simulations. An improvement in predicting the future climate change in regional scale is desirable.
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| 4. |
- Jeong, Jee-Hoon, 1976, et al.
(författare)
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Greening in the circumpolar high-latitude may amplify warming in the growing season
- 2012
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 38:7-8, s. 1421-1431
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Tidskriftsartikel (refereegranskat)abstract
- We present a study that suggests greening in the circumpolar high-latitude regions amplifies surface warming in the growing season (May–September) under enhanced greenhouse conditions. The investigation used a series of climate simulations with the Community Atmospheric Model version 3—which incorporates a coupled, dynamic global vegetation model—with and without vegetation feedback, under both present and doubled CO2 concentrations. Results indicate that climate warming and associated changes promote circumpolar greening with northward expansion and enhanced greenness of both the Arctic tundra and boreal forest regions. This leads to additional surface warming in the high-latitudes in the growing season, primarily through more absorption of incoming solar radiation. The resulting surface and tropospheric warming in the high-latitude and Arctic regions weakens prevailing tropospheric westerlies over 45–70N, leading to the formation of anticyclonic pressure anomalies in the Arctic regions. These pressure anomalies resemble the anomalous circulation pattern during the negative phase of winter Arctic Oscillation. It is suggested that these circulation anomalies reinforce the high-latitude and Arctic warming in the growing season.
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| 5. |
- Jeong, Jee-Hoon, 1976, et al.
(författare)
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Impact of urban warming on earlier spring flowering in Korea
- 2011
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Ingår i: International Journal of Climatology. - : Wiley. - 1097-0088 .- 0899-8418. ; :31, s. 1488-1497
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Tidskriftsartikel (refereegranskat)abstract
- Using long-term (1954-2004) observations of four selected species in South Korea: goldenbell (Forsythia koreana), azalea (Rhododendron mucronulatum), cherry (Prunus yedoensis), and peach (Prunus persica), the impact of urban warming on spring flowering was investigated. Trends of early spring temperatures and first-flowering dates (FFDs) of the four plants were cross-compared among nine differently urbanized cities. It was clearly observed that urban warming has led to an advance in the timing of first-flowering of several days to weeks during recent decades, while the intrinsic physiology of plants to sense thermal energy has not been changed. The degree of advancement of the FFD was observed to be roughly proportional to degree of urbanization. Moreover, the sensitivity of the FFD to urban warming was estimated to be higher for the shrub species (-9.07 and -6.64 days °C-1 for goldenbell and azalea, respectively) than the tree species (-2.46 and -2.90 days °C-1 for peach and cherry, respectively). Our results suggest that the impact of urban warming should be considered as an influential factor which drives changes in the regional natural environment, especially in regions of rapid urbanization. Copyright © 2010 Royal Meteorological Society
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| 6. |
- Jeong, Jee-Hoon, 1976, et al.
(författare)
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Intensified Arctic warming under greenhouse warming by vegetation–atmosphere–sea ice interaction
- 2014
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Observations and modeling studies indicate that enhanced vegetation activities over high latitudes under an elevated CO2 concentration accelerate surface warming by reducing the surface albedo. In this study, we suggest that vegetation-atmosphere-sea ice interactions over high latitudes can induce an additional amplification of Arctic warming. Our hypothesis is tested by a series of coupled vegetation-climate model simulations under 2xCO2 environments. The increased vegetation activities over high latitudes under a 2xCO2 condition induce additional surface warming and turbulent heat fluxes to the atmosphere, which are transported to the Arctic through the atmosphere. This causes additional sea-ice melting and upper-ocean warming during the warm season. As a consequence, the Arctic and high-latitude warming is greatly amplified in the following winter and spring, which further promotes vegetation activities the following year. We conclude that the vegetation-atmosphere-sea ice interaction gives rise to additional positive feedback of the Arctic amplification.
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| 7. |
- Jeong, Jee-Hoon, 1976, et al.
(författare)
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Land Surface Initialization Using an Offline CLM3 Simulation with the GSWP-2 Forcing Dataset and Its Impact on CAM3 Simulations of the Boreal Summer Climate
- 2008
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Ingår i: Journal of Hydrometeorology. ; 9:6, s. 1231-1248
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Tidskriftsartikel (refereegranskat)abstract
- The impacts of initialized land surface conditions on the monthly prediction were investigated using ensemble simulations from the Community Atmosphere Model version 3 (CAM3). The land surface initialization was based on an offline calculation of Community Land Model version 3 driven by observation-based meteorological forcings from the Global Soil Wetness Project 2 (GSWP2). A simple but effective correction method was applied to the GSWP2 forcings prior to the offline calculation to reduce the discrepancies between the observation-forced land surface conditions and the modeling system, which can cause climate drift and initial shock problems. The climatological mean of GSWP2 forcings was adjusted to that of the target model (CAM3), while the monthly anomalies were scaled to the model statistics and high-frequency synoptic variabilities were included. Ensemble hindcast experiments with and without land surface initialization were conducted for the boreal summer (May–September), for 1983–95. The initialization process is shown to prevent climate drift and to transfer the atmospheric anomalies to the land surface memory. Statistical analyses of the simulation results reveal that the land surface initialization increased the externally forced variance over most continental regions, which is translated to enhanced potential predictability, particularly for regions with strong land–atmosphere coupling.
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| 10. |
- Linderholm, Hans W., 1968, et al.
(författare)
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Interannual teleconnections between the summer North Atlantic Oscillation and the East Asian summer monsoon
- 2011
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 116:D13
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Tidskriftsartikel (refereegranskat)abstract
- Here we present a study of the relationship between July–August (JA) mean climate over China, which is strongly linked to the East Asian summer monsoon (EASM), and the summer (JA) North Atlantic Oscillation (SNAO). The variations of temperature, precipitation, and cloud cover related to the SNAO were analyzed for the period 1951–2002 using gridded data sets as well as instrumental data from 160 stations in China. It was shown that the major patterns of summer climate over China are highly connected with the interannual variation of the SNAO, supporting a teleconnection between the North Atlantic region and East Asia. Based on the analyses of the daily and monthly reanalysis data sets, we propose possible mechanisms of this teleconnection. Changes in the position of the North Atlantic storm tracks and transient eddy activity associated with the positive (negative) SNAO phase contribute downstream to negative (positive) sea level pressure anomalies in northeastern East Asia. In negative SNAO years, a stationary wave pattern is excited from the southern SNAO center over northwestern Europe to northeastern East Asia. However, during positive SNAO years, a stationary wave pattern is excited extending from the SNAO center across the central Eurasian continent at around 40°N and downstream to the southeast. This may explain a connection between the positive SNAO and atmospheric circulation in middle and southeastern China.
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