| 1. |
- JEONG, SJ, et al.
(författare)
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Increase in vegetation greenness and decrease in springtime warming over east Asia
- 2009
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Ingår i: GEOPHYSICAL RESEARCH LETTERS. - 0094-8276. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the impact of increased vegetation greening on the springtime temperature over east Asia for 1982-2000. An analysis of station-based temperature records and satellite-measure normalized difference vegetation index (NDVI) indicates that slight warming (<0.4 degrees C 10-yr(-1)) occurred over regions that experienced large increase in NDVI (>= 0.08 10-yr(-1)). On the contrary, strong warming (>= 0.8 degrees C 10-yr(-1)) occurred over regions that exhibited minor changes in NDVI (<0.04 10-yr(-1)). For the most part, this inverse NDVI-temperature relationship observed with the daily maximum temperature. Thus, it is suggested that the decrease in warming was mostly attributable to the increase in evapotranspiration associated with increased vegetation greening. Earlier vegetation growth may have further strengthened the effect of this vegetation-evaporation on spring temperature. Citation: Jeong, S.-J., C.-H. Ho, and J.-H. Jeong (2009), Increase in vegetation greenness and decrease in springtime warming over east Asia, Geophys. Res. Lett., 36, L02710, doi: 10.1029/2008GL036583.
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| 2. |
- JEONG, SJ, et al.
(författare)
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Reduction of spring warming over East Asia associated with vegetation feedback
- 2009
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Ingår i: GEOPHYSICAL RESEARCH LETTERS. - 0094-8276. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- Over East Asia, surface air temperature displays a significant increasing trend particularly in early months of the year for the period of 1982-2000. Warming per decade is strongest in late winter, 1.5 degrees C in February and 1.1 degrees C in March, but is significantly reduced in spring, 0.4 degrees C in April and 0.1 degrees C in May. During the analysis period, the reduced temperature increase from late winter to spring is found to be in contrast with the increased vegetation greenness derived from the satellite-measured leaf area index over the domain. We examined this inverse relationship using two climate model experiments-coupled with and without a dynamic vegetation model. In both experiments, strong warming in winter is relatively well reproduced, but weak warming in spring is observed only in the coupled experiment. Analysis of the surface energy budget indicates that weaker spring warming results from an evaporative cooling effect due to the increased vegetation greenness. Over East Asia, the vegetation-evaporation feedback, therefore, may produce seasonal asymmetry in the warming trend. Citation: Jeong, S.-J., C.-H. Ho, K.-Y. Kim, and J.-H. Jeong (2009), Reduction of spring warming over East Asia associated with vegetation feedback, Geophys. Res. Lett., 36, L18705, doi: 10.1029/2009GL039114.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- HO, CH, et al.
(författare)
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Influence of stratospheric quasi-biennial oscillation on tropical cyclone tracks in the western North Pacific
- 2009
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Ingår i: GEOPHYSICAL RESEARCH LETTERS. - 0094-8276. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- The possible influence of the stratospheric quasi-biennial oscillation (QBO) on tropical cyclone (TC) passages in the western North Pacific (WNP) is examined using TC data recorded by the Tokyo Typhoon Center and the QBO index derived from reanalysis data. The influence is observed to be significant. The number of TCs approaching the East China Sea is large during the westerly phase of the QBO; however, during the easterly phase, the number of TCs approaching the eastern offshore of Japan is large. This difference in the TC tracks is found to be related to the background flow change associated with the QBO. However, the total number of TC events over the WNP and the sum of the number of TCs approaching the aforementioned two regions appear to be unrelated to the QBO phases. Citation: Ho, C.-H., H.- S. Kim, J.- H. Jeong, and S.-W. Son (2009), Influence of stratospheric quasi-biennial oscillation on tropical cyclone tracks in the western North Pacific, Geophys. Res. Lett., 36, L06702, doi:10.1029/2009GL037163.
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| 7. |
- Jeong, Jee-Hoon, 1976
(författare)
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Characteristics of atmospheric circulation associated with cold surge occurrences in East Asia: A case study during 2005/06 winter
- 2008
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Ingår i: Advances in Atmospheric Sciences. - 1861-9533. ; 25:5, s. 791-804
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Tidskriftsartikel (refereegranskat)abstract
- The characteristics of the upper-level circulation and thermodynamical properties for the period when two distinct cold surges broke out over East Asia during the 2005/06 winter are investigated. From early December 2005 to early January 2006, exceptionally cold weather lasted for approximately one month due to two successive cold surges that took place on 2 December 2005 and 2 January 2006, respectively. This study reveals that both involve the upper-tropospheric circulation, which induces the amplification and expansion of the surface Siberian high toward East Asia, but arose from different causes: the former is caused by the upper-level blocking originated from the North Pacific and the latter is caused by the upper-level wave train across the Eurasian Continent. In particular, it is suggested that the lower-tropospheric anomalous wind caused by upper-level circulation anomalies and a steep meridional temperature gradient amplified by phase-locked annual cycle combined to induce very strong cold advection in East Asia, which resulted in exceptionally cold weather that lasted for several weeks. The present results emphasize that the characteristics of the upper-tropospheric circulation can be considered as important precursors to cold surge occurrences in East Asia.
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| 8. |
- 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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| 9. |
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| 10. |
- Kim, B-M., et al.
(författare)
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Investigation of Stratospheric Precursor for the Cold Surge Event using Potential Vorticity Inversion Technique
- 2009
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Ingår i: Asia-Pacific Journal of Atmospheric Sciences. - 1976-7633. ; 45:4, s. 513-522
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Tidskriftsartikel (refereegranskat)abstract
- The downward influence of stratospheric potential vorticity (PV) on the cold surge occurrence over East Asia was examined. Strong negative PV anomalies in the upper stratosphere and the rising of geopotential height in the upper troposphere about one week ahead of the cold surge occurrence were suggested as precursory perturbations triggering the development of the cold surge, which is dynamically validated by the piecewise potential vorticity inversion technique. When the inversion is applied to the stratospheric PV anomalies, geopotential and temperature anomalies balanced to the stratospheric PV were remarkably well reproduced in both amplitude and penetrating depth as in the observations. Although the PV anomalies are mostly confined to the stratosphere, our results confirm that its downward influences are sufficiently strong such that associated tropospheric anomalies with the stratospheric PV are capable of triggering the cold surge occurrence within the given mechanism.
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